CN115838521B

CN115838521B - Hollow fiber composite, method for producing same, pole piece, battery module, battery pack, and device

Info

Publication number: CN115838521B
Application number: CN202210698413.6A
Authority: CN
Inventors: 云亮; 孙信; 吴李力; 董苗苗; 宋佩东
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-06-20
Filing date: 2022-06-20
Publication date: 2024-06-28
Anticipated expiration: 2042-06-20
Also published as: CN115838521A

Abstract

The invention relates to a hollow fiber composite and a manufacturing method thereof, a pole piece, a battery module, a battery pack and a device. The hollow fiber composite includes hollow fibers having an average pore diameter of 3 μm to 40 μm, optionally 5 μm to 30 μm, and magnetic particles distributed on at least a part of the surfaces of the hollow fibers. According to the hollow fiber composite of the present invention, the wetting time of the electrolyte to the pole piece can be shortened in a battery or the like containing the same, and the battery or the like containing the same can be made to achieve high energy density and excellent rate performance.

Description

Hollow fiber composite, method for producing same, pole piece, battery module, battery pack, and device

Technical Field

The invention relates to the field of batteries, in particular to a hollow fiber composite, a manufacturing method thereof, a pole piece, a battery module, a battery pack and a device.

Background

At present, with the continuous development of science and technology, batteries such as lithium ion batteries and metal lithium batteries are widely applied to portable small-sized mobile devices such as mobile phones, video cameras and notebook computers, and various electronic devices such as large-sized devices requiring high energy with high power such as electric automobiles and energy storage systems. As a result, the requirements on the performance of the battery, in particular the energy density of the battery, are also increasing. Therefore, how to increase the energy density of the battery has become one of the hot spots of research.

In order to increase the energy density of the battery, for example, a method of increasing the content of the active material to increase the thickness of the battery electrode sheet is considered. The method can improve the carrying capacity of active substances on the surface of the pole piece in unit area, and is very beneficial to improving the specific energy of the battery. However, in the practical application process, if the thickness of the battery pole piece is increased by only increasing the content of the active material, the electrolyte is difficult to permeate into the active material close to the surface of the pole piece, so that the wettability of the electrolyte is poor, the active material close to the current collector almost cannot participate in electrochemical reaction, the capacity cannot be normally exerted, on the other hand, the active material far from the current collector is deeply discharged, and further structural damage is caused during long circulation, capacity attenuation is aggravated, and the high-current rate performance and the circulation performance of the pole piece are poor.

Disclosure of Invention

The present application has been made in view of the above circumstances, and an object thereof is to provide a hollow fiber composite capable of improving energy density and rate characteristics of a battery and shortening a soaking time of an electrolyte solution to a pole piece even if an amount of an active material is increased, a method for manufacturing the same, and a pole piece, a battery module, a battery pack, and an electric device including the hollow fiber composite.

In order to achieve the above object, a first aspect of the present application provides a hollow fiber composite comprising: hollow fiber; and magnetic particles distributed on at least a part of the surface of the hollow fibers, the hollow fibers having an average pore diameter of 3 μm to 40 μm, alternatively 5 μm to 30 μm.

The hollow fiber composite is used for the membrane of the electrode, so that micron-sized through holes with a certain depth can be formed in the membrane, the occurrence of a closed hole phenomenon caused by too small pore diameter in the electrode manufacturing process can be avoided, the liquid phase mass transfer capability can be improved, the infiltration and reflux of electrolyte are facilitated, the ion transmission is accelerated, the liquid phase polarization is reduced, the depth of an electrochemical reaction of a pole piece is increased, the gram capacity of an active substance is improved, the quick charge performance is improved, the energy density and the multiplying power performance of a battery can be improved, the electrolyte is facilitated to permeate into the active substance close to the surface of the pole piece, and the infiltration time of the electrolyte to the pole piece can be shortened; in addition, as the depth of the electrochemical reaction of the pole piece is increased, the pole piece can be formed thicker, and the use of a current collector and a diaphragm can be reduced in the secondary battery shell with the same volume, so that the cost is greatly reduced.

In some embodiments, the hollow fibers have an average fiber diameter of 4 μm to 60 μm, alternatively 5 μm to 30 μm. By making the average fiber diameter of the hollow fiber within the above range, when the hollow fiber composite is used for a membrane, it is possible to achieve both high energy density and excellent rate characteristics without affecting the conductive network of the pole piece, and to shorten the wetting time of the electrolyte to the pole piece.

In some embodiments, the hollow fibers have an average fiber length of 30 μm to 100 μm, alternatively 40 μm to 80 μm. The average fiber length of the hollow fiber is in the range, so that the energy density and the multiplying power performance of the battery can be further improved, the infiltration and the backflow of the electrolyte are facilitated, the depth of the electrochemical reaction of the pole piece is increased, and the infiltration time of the electrolyte to the pole piece is further shortened.

In some embodiments, the hollow fibers are composed of a polymer having an electrical conductivity of 5 x 10 ^- ⁵S/m～5×10^-3 S/m, optionally one or more selected from the group consisting of polyacrylonitrile, polyurethane, polypropylene. By making the hollow fiber of the above polymer, when the hollow fiber composite is used for a membrane, the energy density and rate capability of the battery can be further improved without affecting the conductive network of the pole piece.

In some embodiments, the magnetic material constituting the magnetic particles is one or more selected from the group consisting of ferroferric oxide, alnico, iron-chromium-cobalt alloy, and iron-silicon alloy. The magnetic particles have an average particle diameter of 1nm to 100nm, alternatively 1nm to 50nm. When the hollow fiber composite is used for the membrane by using the magnetic particles with specific average particle size, micron-sized through holes with a certain depth can be formed on the membrane, so that the infiltration and reflux of electrolyte are facilitated, the depth of electrochemical reaction of the pole piece is increased, the gram-capacity exertion of active substances is increased, and the energy density and the multiplying power performance of the battery are further improved.

In some embodiments, the mass ratio of the magnetic particles to the hollow fibers is 1:20 to 2:10. By controlling the mass ratio of the magnetic particles to the hollow fibers in the hollow fiber composite within the above-described range, it is possible to achieve both high energy density and excellent rate performance without affecting the performance of the battery.

In addition, a second aspect of the present application provides a method for producing a hollow fiber composite according to the first aspect of the present application, comprising the steps of,

A step of dissolving a polymer constituting the hollow fiber in an organic solvent and sufficiently mixing the dissolved polymer to prepare a spinning solution;

spinning the prepared spinning solution to obtain the hollow fiber;

Dispersing the prepared hollow fibers and magnetic particles in a solvent and crushing to obtain crushed materials;

And drying the obtained pulverized product to obtain a hollow fiber composite.

In some embodiments, additives are also included in the dope, the additives being organic additives and/or inorganic additives, optionally one or more selected from polyethylene glycol, polyvinylpyrrolidone, potassium chloride, calcium chloride, sodium chloride, lithium bromide, lithium nitrate.

In some embodiments, the organic solvent in the dope is a solvent that dissolves the polymer, optionally one or more selected from acetone, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide.

In some embodiments, the method of spinning is a wet spinning method, optionally an electrospinning method.

In some embodiments, the solvent in which the hollow fibers and the magnetic particles are dispersed is a solvent in which the hollow fibers and the magnetic particles are not dissolved and uniformly dispersed, optionally one or more selected from water and alcohol, optionally water and/or ethanol.

Further, a third aspect of the present application provides a pole piece comprising a current collector and a membrane provided on at least one surface of the current collector, the membrane comprising the hollow fiber composite according to the first aspect of the present application or the hollow fiber composite produced by the method for producing a hollow fiber composite according to the second aspect of the present application.

Through the hollow fiber compound, through holes with a certain depth are formed in the membrane, so that the liquid phase mass transfer capability is improved, the electrolyte is facilitated to infiltrate and reflow, the ion transmission is accelerated, the liquid phase polarization is reduced, the depth of the pole piece for electrochemical reaction is increased, the gram capacity of active substances is increased, and the quick charge performance is improved, so that the energy density and the rate capability of the battery can be improved, the electrolyte is facilitated to infiltrate into the active substances close to the surface of the pole piece, and the infiltration time of the electrolyte to the pole piece can be shortened; in addition, the use of current collectors and diaphragms can be reduced, so that the cost is greatly reduced.

In some embodiments, through holes are formed in the membrane from the hollow fiber composite, the through holes having an average depth of 20 μm to 200 μm, alternatively 30 μm to 100 μm. Through forming the through-hole of certain degree of depth on the diaphragm, can increase the degree of depth that the pole piece takes place electrochemical reaction, further improve the liquid phase and pass the ability, more be favorable to infiltration and the backward flow of electrolyte to further shorten the infiltration time of electrolyte to the pole piece, and further improve the energy density and the multiplying power performance of battery.

In some embodiments, the membrane has an open porosity of 1% to 10%, alternatively 2% to 5%. By making the aperture ratio of the membrane within the above range, the electrolyte can be more favorably infiltrated and reflowed, thereby further improving the energy density and the multiplying power performance of the battery and further shortening the infiltration time of the electrolyte to the pole piece.

In some embodiments, the membrane has a thickness of 200 μm to 1000 μm, alternatively 250 μm to 600 μm. By setting the thickness of the membrane to the above range, the depth of the electrochemical reaction of the electrode sheet can be increased, and the gram capacity of the active material can be increased.

In some embodiments, the mass percent of the hollow fiber composite in the membrane is 1% to 10%, alternatively 3% to 5%. By incorporating the hollow fiber composite in the specific range in the membrane, low cost, low wetting time of the electrolyte to the pole piece, high energy density of the battery, and excellent rate performance can be achieved without affecting the conductive network of the pole piece.

In some embodiments, the pole piece is a positive pole piece or a negative pole piece, optionally a positive pole piece.

A fourth aspect of the present application provides a battery, comprising: a pole piece according to the third aspect of the application, or a pole piece having the hollow fiber composite according to the first aspect of the application or a hollow fiber composite produced by the method of producing a hollow fiber composite of the second aspect of the application.

A fifth aspect of the application provides a battery module comprising a battery according to the fourth aspect of the application.

A sixth aspect of the application provides a battery pack comprising the battery module according to the fifth aspect of the application.

A seventh aspect of the present application provides an apparatus comprising at least one of the battery according to the fourth aspect of the present application, the battery module according to the fifth aspect of the present application, or the battery pack according to the sixth aspect of the present application.

The battery, battery module, battery pack and device of the present application comprise a pole piece having the hollow fiber composite provided by the present application, and thus have at least the same advantages as the pole piece.

Drawings

Fig. 1 is a schematic structural view of an embodiment of the positive electrode sheet of the present application.

Fig. 2 is a schematic view of a battery according to an embodiment of the present application.

Fig. 3 is an exploded view of the battery of one embodiment of the present application shown in fig. 2.

Fig. 4 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 5 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 6 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 5.

Fig. 7 is a schematic view of an apparatus in which a battery according to an embodiment of the present application is used as a power source.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present application more apparent, embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, it should be understood by those of ordinary skill in the art that these examples are merely illustrative of the technical solution of the present application and are not limiting.

For simplicity, the present application specifically discloses some numerical ranges. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each point or individual value between the endpoints of the range is included within the range, although not explicitly recited. Furthermore, each separately disclosed point or individual value may itself be combined as a lower limit or upper limit with any other point or individual value or with other lower limit or upper limit to form a range not explicitly recited.

In the description herein, unless otherwise indicated, "above" and "below" are intended to include the present number, and "one or more" means two or more.

The above summary of the present application is not intended to describe each disclosed embodiment or every implementation of the present application. The following description more particularly exemplifies illustrative embodiments. Guidance is provided throughout this application by a series of embodiments, which may be used in various combinations. In the various examples, the list is merely a representative group and should not be construed as exhaustive.

The hollow fiber composite of the present application, a method for producing the same, and a pole piece, a battery module, a battery pack, and an electric device including the hollow fiber composite will be described in detail with reference to the drawings.

Hollow fiber composite

The hollow fiber composite of the present application comprises: hollow fiber; and magnetic particles distributed on at least a part of the surface of the hollow fiber, the hollow fiber having an average pore diameter of 3 μm to 40 μm, alternatively 5 μm to 30 μm.

The hollow fiber of the present application is a shaped fiber having a cavity in the axial direction in the cross section. The shape of the hollow cross section of the hollow fiber is not particularly limited, and examples thereof include a circular shape, an elliptical shape, and a quadrangular shape, and from the viewpoint of facilitating the infiltration and the reflow of the electrolyte, the hollow fiber is preferably a circular shape or an elliptical shape, and more preferably a circular shape. The number of holes of the hollow fiber is not particularly limited, and examples thereof include single holes, two holes, four holes, and the like, and single holes are preferable from the viewpoint of not affecting the conductive network of the electrode sheet and facilitating the infiltration and reflow of the electrolyte.

The hollow fiber has the average pore diameter in the range, so that the occurrence of a closed pore phenomenon caused by too small pore diameter in the electrode manufacturing process can be avoided, the liquid phase mass transfer capability can be improved, the infiltration and the reflux of electrolyte are facilitated, the transmission of ions is accelerated, and the depth of the electrochemical reaction of the electrode plate is increased. In addition, the pore size of the hollow fibers can be measured by methods known in the art. For example, an electron micrograph of a cross section of a hollow fiber is taken by a scanning electron microscope, and the maximum diameter of any 30 pores in the photograph is measured and averaged to obtain an average pore diameter of the hollow fiber.

The magnetic material constituting the magnetic particles may be any material having magnetic properties, and specifically, alloys of ferromagnetic materials such as nickel (Ni), iron (Fe), cobalt (Co) (e.g., co—fe, co—fe—ni, ni—fe, etc.), alloys of these alloys mixed with nonmagnetic elements (e.g., tantalum, boron, chromium, platinum, silicon, carbon, nitrogen, phosphorus, etc.), oxides containing 1 or more of Co, fe, ni (e.g., fe—mno, etc.), intermetallic compounds called semi-metallic ferromagnetic materials (hassle alloys: niMnSb, co ₂MnGe、Co₂ MnSi, etc.), oxides (e.g., crO ₂、Fe₃O₄, etc.), and the like may be cited. Among them, from the viewpoint that the magnetic particles can be firmly adsorbed on the surface of the hollow fiber and that a micrometer-sized through hole of a certain depth can be formed in the membrane, the magnetic material constituting the magnetic particles is preferably one or more selected from the group consisting of ferroferric oxide, alnico, fechronico, and fesilcon.

The inventors of the present application have made intensive studies to solve the above-mentioned problems occurring in the prior art, and as a result, found that: the hollow fiber compound containing the magnetic particles is added into the membrane of the electrode, so that micron-sized through holes with a certain depth can be formed in the membrane, the occurrence of a closed hole phenomenon caused by too small pore diameter in the electrode manufacturing process can be avoided, the liquid phase mass transfer capability can be improved, the infiltration and the backflow of electrolyte are facilitated, the ion transmission is accelerated, the liquid phase polarization is reduced, the depth of an electrochemical reaction of a pole piece is increased, the gram capacity of an active substance is improved, the quick charging performance is improved, the energy density and the multiplying power performance of a battery can be improved, the electrolyte can be facilitated to be quickly permeated into the active substance close to the surface of the pole piece, and the infiltration time of the electrolyte to the pole piece can be shortened; in addition, as the depth of the electrochemical reaction of the pole piece is increased, the pole piece can be formed thicker, and the use amount of the current collector and the diaphragm can be reduced in the secondary battery shell with the same volume, so that the cost of the battery is greatly reduced. Therefore, according to the hollow fiber composite of the present embodiment, a battery or the like including the hollow fiber composite can achieve high energy density, excellent rate performance, and a low wetting time of the electrode sheet with the electrolyte.

In the hollow fiber composite of the present application, the hollow fibers have an average fiber diameter of 4 μm to 60 μm, alternatively 5 μm to 30 μm. By making the average fiber diameter of the hollow fiber within the above range, when the hollow fiber composite is used for a membrane, it is possible to achieve both high energy density and excellent rate characteristics without affecting the conductive network of the pole piece, and to shorten the wetting time of the electrolyte to the pole piece. The average fiber diameter of the hollow fiber of the present application can be measured by a method known in the art. For example, an electron micrograph of a cross section of a hollow fiber is taken by a scanning electron microscope, and the fiber diameters of any 30 fibers in the photograph are measured and averaged to obtain an average fiber diameter of the hollow fiber.

In the hollow fiber composite of the present application, the hollow fibers have an average fiber length of 30 μm to 100 μm, alternatively 40 μm to 80 μm. By making the average fiber length of the hollow fiber in the above range, the energy density and the multiplying power performance of the battery can be further improved, and the electrolyte is more favorable for infiltration and backflow, and the depth of the electrochemical reaction of the pole piece is increased, so that the infiltration time of the electrolyte to the pole piece is further shortened.

In the hollow fiber composite of the present application, the hollow fibers are composed of a polymer, optionally a polymer having an electrical conductivity of 5×10 ^-5S/m～5×10^-3 S/m, optionally one or more of polyacrylonitrile, polyurethane, polypropylene. By making the hollow fiber of the above polymer, when the hollow fiber composite is used for a membrane, the energy density and rate capability of the battery can be further improved without affecting the conductive network of the pole piece.

The molecular weight of the polymer constituting the hollow fiber is not particularly limited as long as the number average molecular weight is 1 ten thousand or more. The electrical conductivity of the polymer constituting the hollow fiber can be measured by a conductivity tester.

In the hollow fiber composite of the present application, the average particle diameter of the magnetic particles is 1nm to 100nm, alternatively 1nm to 50nm. When the hollow fiber composite is used for the membrane, micron-sized through holes with a certain depth can be formed in the membrane by using the magnetic particles with the average particle size in the range, so that the infiltration and reflux of electrolyte are facilitated, the depth of electrochemical reaction of the pole piece is increased, the gram capacity of active substances is increased, and the energy density and the multiplying power performance of the battery are further improved. The average particle diameter of the magnetic particles in the hollow fiber composite of the present application can be measured by a method known in the art. For example, the measurement can be performed by a laser particle size distribution analyzer.

In the hollow fiber composite of the present application, the mass ratio of the magnetic particles to the hollow fibers is 1:20 to 2:10. By controlling the mass ratio of the magnetic particles to the hollow fibers in the hollow fiber composite within the above-described range, it is possible to achieve both high energy density and excellent rate performance without affecting the performance of the battery. The mass ratio of the magnetic particles to the hollow fibers can be controlled by controlling the feed ratio of the raw materials in the manufacture of the hollow fiber composite.

Method for producing hollow fiber composite

The hollow fiber composite of the present application can be produced by a production method comprising the following steps. In particular the number of the elements,

A step of dissolving a polymer constituting the hollow fiber in an organic solvent and sufficiently mixing the dissolved polymer to prepare a dope (hereinafter, sometimes simply referred to as a "dope preparation step");

Spinning the obtained spinning solution to obtain a hollow fiber (hereinafter, sometimes simply referred to as "spinning step");

A step of dispersing the obtained hollow fibers and magnetic particles in a solvent and pulverizing the dispersed hollow fibers and magnetic particles to obtain a pulverized product (hereinafter, sometimes simply referred to as "pulverizing step");

And a step of drying the obtained pulverized product to obtain a hollow fiber composite (hereinafter, may be simply referred to as "drying step").

The steps are described in detail below.

[ Step of preparing spinning solution ]

The spinning solution preparation step is a step of dissolving a polymer constituting the hollow fiber in an organic solvent and sufficiently mixing the same, thereby preparing a spinning solution.

The organic solvent used in the spinning solution step is not particularly limited as long as it is a volatile organic solvent capable of dissolving the polymer constituting the hollow fiber. Examples thereof include ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; aprotic polar solvents such as N, N-dimethylformamide and N, N-dimethylacetamide. Among them, acetone, tetrahydrofuran, N-dimethylformamide and N, N-dimethylacetamide are preferable. These organic solvents may be used singly or in combination of two or more.

In addition, in order to enhance the compatibility of the polymer resin in the spinning solution and to facilitate the formation of the cavity, an additive may be further contained in the spinning solution. Examples of such additives include organic additives such as polyethylene glycol and polyvinylpyrrolidone; inorganic additives such as potassium chloride, calcium chloride, sodium chloride, lithium bromide, and lithium nitrate. These additives may be used either individually or in combination of two or more. The organic additives help to increase the miscibility of the polymer in the spinning solution, the inorganic additives help to form the hollow cavities of the hollow fibers, and help to control the pore size of the hollow fibers during spinning.

The content of the polymer constituting the hollow fiber in the obtained spinning solution may be 3 to 18% by mass, preferably 5 to 10% by mass, and the content of the organic solvent may be 72 to 97% by mass, preferably 80 to 90% by mass. In the case of adding the additive to the spinning solution, the content of the additive in the spinning solution may be 1 to 10%, preferably 3 to 6%.

Examples of the mixing method used in the spinning solution preparation step include mixing by ultrasonic waves, mixing by a homogenizer, and the like, and are not particularly limited.

[ Spinning step ]

The spinning step is a step of spinning the prepared spinning solution to obtain the hollow fiber. Examples of the spinning method include wet spinning and electrostatic spinning, and from the viewpoint of productivity, the electrostatic spinning method is preferable.

When spinning is performed by the electrostatic spinning method, the spinning solution placed in the electric field is sufficiently charged, and then the spinning solution is discharged from the hollow fiber nozzle toward the receiving device, and the organic solvent evaporates, and at this time, the charge density of the spinning solution becomes excessive, and the organic solvent evaporates while further refining by coulomb repulsion, so that a dry coating film containing hollow fibers is finally formed. As spinning conditions for the electrospinning, the feeding speed was set to 1 to 15ml/min, the receiving distance was set to 5 to 20cm, the rotational speed was set to 100 to 800rpm/min, and the voltage was set to 10 to 20kV. By adjusting the spinning conditions, the fiber diameter and pore diameter of the hollow fiber can be controlled.

In the case of spinning by the wet spinning method, the spinning solution is discharged from a hollow fiber nozzle, and then is drawn and coagulated by a coagulation bath to finally obtain a hollow fiber. As spinning conditions for wet spinning, the feed rate was set to 1 to 15ml/min and the rotational speed was set to 100 to 800rpm/min. The coagulation bath may be appropriately selected according to the kind of polymer used. The fiber diameter and the pore diameter of the hollow fiber can be adjusted by controlling the size of the spray head, the stretching force, the solidification condition and the like.

In addition, a step of standing the spinning solution for a certain period of time may be performed before the spinning step. By this step, the spinning solution can be defoamed. The time for the standing is not particularly limited as long as the spinning solution can be defoamed, and examples thereof include 1 to 12 hours, and preferably 1 to 6 hours from the viewpoint of productivity.

[ Pulverizing step ]

The pulverization step is a step of dispersing the obtained hollow fibers and magnetic particles in a solvent and pulverizing to obtain a pulverized product. By dispersing the hollow fibers and the magnetic particles in a solvent, it is advantageous for the magnetic particles to be uniformly adsorbed on at least a part of the surfaces of the hollow fibers. By "surface" is meant herein both the surface of the inner wall of the cavity of the hollow fiber and the outer surface of the hollow fiber.

The solvent used in the pulverization step is not particularly limited as long as it does not dissolve the hollow fibers and the magnetic particles and can uniformly disperse them, and examples thereof include water; alcohols such as ethanol and propanol are preferably water or ethanol from the viewpoint of cost. These solvents may be used singly or in combination of two or more.

In the pulverizing step, pulverization may be performed using a pulverizer. Examples of the pulverizer include a medium-free pulverizer such as an air jet mill; medium type pulverizer such as ball mill, bead mill, rod mill, and crusher. The particle diameter of the pulverized product can be appropriately adjusted according to the particle diameter of the targeted hollow fiber.

[ Drying step ]

The drying step is a step of drying the obtained pulverized product to obtain a hollow fiber composite. The drying may be performed by placing the pulverized product after pulverization in an oven, but is not limited thereto, and any method may be used as long as the pulverized product can be dried without damaging the structure of the hollow fiber.

The resulting hollow fiber composite mainly comprises hollow fibers and magnetic particles, and the diameter of the magnetic particles is nano-scale, so that the pore diameter of the hollow fiber composite is basically equal to that of the hollow fibers, and the fiber diameter of the hollow fiber composite is basically equal to that of the hollow fibers.

Battery cell

The battery in the present application refers to a battery that can be continuously used by activating an active material by means of charging after the battery is discharged. Typically, a battery includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The barrier film sets up between positive pole piece and negative pole piece, and it can prevent inside emergence short circuit to the electron insulation, makes active ion can permeate and remove between positive and negative pole simultaneously, plays the effect of isolation. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate.

The hollow fiber composite of the application can be used in the membrane of the positive pole piece and/or the negative pole piece, preferably in the membrane of the positive pole piece. The hollow fiber compound is contained in the membrane of the positive electrode plate and/or the negative electrode plate, so that micron-sized through holes with a certain depth can be formed in the membrane, the occurrence of a closed hole phenomenon in the electrode manufacturing process can be avoided, the liquid phase mass transfer capability can be improved, the infiltration and backflow of electrolyte are facilitated, the ion transmission is accelerated, the liquid phase polarization is reduced, the depth of the electrochemical reaction of the electrode plate is increased, the gram capacity of active substances is improved, the quick charge performance is improved, the energy density and the multiplying power performance of a battery can be improved, the electrolyte can be facilitated to be quickly permeated into the active substances close to a current collector, and the infiltration time of the electrolyte to the electrode plate can be shortened; in addition, the use amount of the current collector and the diaphragm can be reduced, so that the cost of the battery is greatly reduced.

The battery of the present application may be any of a lithium ion battery, a metal lithium battery, and the like.

[ Positive electrode sheet ]

Fig. 1 is a schematic structural view of an embodiment of the positive electrode sheet of the present application. As shown in fig. 1, the positive electrode tab 100 of the present application includes a positive electrode current collector 20 and a positive electrode membrane 10 provided on one surface in the thickness direction of the positive electrode current collector. In addition, the positive electrode current collector has two surfaces opposing each other in the thickness direction thereof, and the positive electrode membrane may be disposed on the two opposing surfaces of the positive electrode current collector.

The positive electrode sheet 10 includes a micron-sized through hole 11 formed of the hollow fiber composite of the present application. By including the hollow fiber composite in the membrane, an external magnetic field is applied in the manufacturing process of the positive membrane to enable the hollow fiber composite to be oriented in the depth direction of the membrane, so that a through hole with a certain depth is formed in the membrane, the liquid phase mass transfer capability is improved, the electrolyte is facilitated to be infiltrated and reflowed, the ion transmission is accelerated, the liquid phase polarization is reduced, the depth of the electrode plate for electrochemical reaction is increased, the gram capacity of the positive active substance is increased, the quick charge performance is improved, the energy density and the multiplying power performance of the battery can be improved, the electrolyte is facilitated to be quickly infiltrated into the active substance close to the current collector, and the infiltration time of the electrolyte to the electrode plate can be shortened.

Through holes are formed in the membrane sheet from the hollow fiber composite, the through holes having an average depth of 20 μm to 200 μm, alternatively 30 μm to 100 μm. Through forming the through-hole of certain degree of depth on the diaphragm, can increase the degree of depth that the pole piece took place electrochemical reaction, further improve the liquid phase and pass the ability, more be favorable to infiltration and the backward flow of electrolyte to further improve energy density and the multiplying power performance of battery, and further shorten the infiltration time of electrolyte to the pole piece, can also avoid the reduction of energy density and multiplying power performance because the through-hole is dark too deeply, and avoid because the through-hole is dark too little and can't shorten the infiltration time of electrolyte to the pole piece. In the present application, the size of the average depth of the through holes can be adjusted by adjusting the length of the hollow fibers or the like. In addition, the average depth of the through-holes can be measured by a method using ion polishing and scanning electron microscopy.

In some embodiments, the aperture ratio of the through-holes formed by the hollow fiber composite on the membrane is 1% to 10%, alternatively 2% to 5%. By making the aperture ratio within the above range, the infiltration and the reflow of the electrolyte can be more facilitated, thereby further improving the energy density and the rate performance of the battery.

In some embodiments, the mass percent of hollow fiber composite in the membrane is 1% to 10%, alternatively 3% to 5%. By containing the hollow fiber composite in the specific range in the membrane, the cost is low, the high energy density of the battery and the excellent rate performance are achieved under the condition that the conductive network of the electrode is not affected, the use amount of the current collector and the membrane can be reduced, and the cost of the battery is greatly reduced.

The positive electrode sheet of the present application further comprises a positive electrode active material. The positive electrode active material may include, but is not limited to, lithium cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel type lithium manganate, spinel type lithium nickel manganate, lithium titanate, and the like. One or more of these may be used as the positive electrode active material.

The positive electrode film sheet of the present application further comprises an optional binder and a conductive agent. The application does not limit the types of the conductive agent and the binder, and can be selected according to actual requirements.

As an example, the binder may include one or more selected from styrene-butadiene rubber (SBR), aqueous acrylic resin (water based ACRYLIC RESIN), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA). The conductive agent may include one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In the battery of the present application, the positive electrode current collector may be a metal foil, a porous metal plate, or a composite current collector. As the metal foil and the porous metal plate, for example, a foil of a metal such as aluminum, copper, nickel, titanium, silver, or the like, or a porous plate of an alloy thereof, preferably aluminum foil, may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (e.g., aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). The thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm, more preferably 8 μm to 16 μm.

The positive electrode sheet of the present application may be prepared according to a method generally known in the art. For example, the hollow fiber composite, the positive electrode active material, the optional conductive agent, the optional binder, and any other ingredients may be dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector in a state of applying an external magnetic field, and obtaining the positive electrode plate after the procedures of drying, cold pressing and the like.

[ Negative electrode sheet ]

In the battery of the present application, the negative electrode tab generally includes a negative electrode current collector and a negative electrode membrane disposed on at least one surface of the negative electrode current collector. As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode membrane is provided on either one or both of the two surfaces opposing the anode current collector.

The negative electrode sheet may contain the hollow fiber composite of the present application, similarly to the positive electrode sheet. Thus, a micrometer-sized through hole formed of the hollow fiber composite of the present application is produced in a depth in the negative electrode sheet. Therefore, the liquid phase mass transfer capability is improved, the infiltration and the backflow of the electrolyte are facilitated, the depth of the electrochemical reaction of the pole piece is increased, the energy density and the multiplying power performance of the battery are improved, and the infiltration time of the electrolyte to the pole piece is shortened.

In the negative electrode sheet, the average depth, the aperture ratio, the thickness of the membrane, and the content of the hollow fiber composite are the same as those in the positive electrode sheet, and preferably the same.

In the battery of the application, the negative electrode current collector can be made of metal foil, porous metal plate or composite current collector. For example, as the metal foil or porous metal plate, a foil or porous plate of a metal such as copper, nickel, titanium, or iron, or an alloy thereof, preferably copper foil, may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (e.g., copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In the battery of the present application, the negative electrode membrane typically further includes a negative electrode active material, and optionally a conductive agent, a binder, and a thickener.

The negative electrode active material may be used as a negative electrode active material commonly used in the art for preparing a negative electrode of a battery, and may be, for example, one or more of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon-carbon composite, siO, li-Sn alloy, li-Sn-O alloy, sn, snO, snO ₂, spinel-structured lithium titanate Li ₄Ti₅O₁₂, li-Al alloy, and metallic lithium.

As an example, the conductive agent may include one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

As an example, the binder may include one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), aqueous acrylic resin (water-based ACRYLIC RESIN), and carboxymethyl cellulose (CMC).

As an example, the thickener may be carboxymethyl cellulose (CMC) or the like.

The present application is not limited to these materials, and the present application may also use other materials than the anode active material, the conductive agent, the binder, and the thickener, which can be used as a battery.

The negative electrode tab of the present application may be prepared according to a method generally known in the art. Specifically, a hollow fiber composite, a negative electrode active material, and optionally a conductive agent, a binder, and a thickener are dispersed in a solvent to form a uniform negative electrode slurry, and then the negative electrode slurry is coated on a negative electrode current collector in a state of applying an external magnetic field, and the negative electrode is obtained through procedures such as drying, cold pressing, and the like. Wherein the solvent can be N-methyl pyrrolidone (NMP) or deionized water, etc.

[ Electrolyte ]

The electrolyte of the present application comprises an organic solvent, an electrolyte lithium salt and an additive. The types of the organic solvent and the electrolyte lithium salt are not particularly limited, and may be selected according to actual needs.

As an example, the solvent may be one or more selected from Ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene Carbonate (BC), fluoroethylene carbonate (FEC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylsulfone (EMS) and diethylsulfone (ESE), and two or more thereof are preferably used.

As an example, the electrolyte lithium salt may be one or more selected from lithium hexafluorophosphate (LiPF ₆), lithium tetrafluoroborate (LiBF ₄), lithium perchlorate (LiClO ₄), lithium hexafluoroarsenate (LiAsF ₆), lithium bis-fluorosulfonimide (LiFSI), lithium bis-trifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (lipfob), lithium dioxaato borate (LiBOB), lithium difluorophosphate (LiPO ₂F₂), lithium difluorodioxaato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP).

The electrolyte may also optionally include additives. The additive may be any additive that can be used for a battery, and is not particularly limited, and may be selected according to actual needs. As an example, the additive may include one or more of Vinylene Carbonate (VC), ethylene carbonate (VEC), succinonitrile (SN), adiponitrile (AND), 1, 3-propenesulfonic acid lactone (PST), sulfonate cyclic quaternary ammonium salt, tris (trimethylsilane) phosphate (TMSP), AND tris (trimethylsilane) borate (TMSB).

The electrolyte may be prepared according to a method generally known in the art. Specifically, the organic solvent, the electrolyte lithium salt and optional additives may be uniformly mixed to obtain the electrolyte. The order of addition of the respective substances is not particularly limited. For example, an electrolyte lithium salt and optional additives may be added to an organic solvent and mixed uniformly to obtain an electrolyte.

In addition, as the electrolyte of the present application, a commercially available product may be used in addition to the electrolyte prepared by the above method. For example, trade name 8950FB manufactured by national wav chemical materials limited, etc. may be cited.

[ Isolation Membrane ]

The separator of the present application is not particularly limited in kind, and any known porous separator having electrochemical stability and chemical stability used in batteries such as lithium ion batteries and lithium metal batteries may be used. For example, the separator may be one or more selected from a glass fiber film, a nonwoven fabric film, a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, and a multilayer composite film containing one or two or more thereof.

In some embodiments, the positive electrode plate, the isolating film and the negative electrode plate are stacked in sequence, so that the isolating film is positioned between the positive electrode plate and the negative electrode plate to play a role of isolation, an electrode assembly is obtained, the electrode assembly is placed in an outer package, electrolyte is injected into the outer package, and the outer package is sealed, so that batteries such as lithium ion batteries or metal lithium batteries are obtained. In addition to the lamination process described above, the positive electrode tab, the separator, and the negative electrode tab may also be obtained by a winding process.

In some embodiments, the outer packaging of the battery, such as a lithium ion battery or a metallic lithium battery, may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the battery may also be a pouch, such as a pouch-type pouch. The soft bag can be made of one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

The shape of the battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. Fig. 2 shows a square lithium ion battery 5.

In some embodiments, referring to fig. 3, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the lithium ion battery 5 may be one or several and may be adjusted according to the needs.

In some embodiments, the lithium ion secondary batteries may be assembled into a battery module, and the number of secondary batteries contained in the battery module may be plural, and the specific number may be adjusted according to the application and capacity of the battery module.

Fig. 4 is a battery module 4 as an example. Referring to fig. 4, in the battery module 4, a plurality of lithium ion batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a housing having an accommodating space in which the plurality of batteries 5 are accommodated.

In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

Fig. 5 and 6 are battery packs 1 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

Device and method for controlling the same

Another aspect of the application provides an apparatus comprising at least one of the battery, battery module, or battery pack provided by the application. The battery may be used as a power source for the device and may also be used as an energy storage unit for the device. The device may be, but is not limited to, a mobile device (e.g., a cell phone, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a watercraft, a satellite, an energy storage system, etc.

The device may select a battery, a battery module, or a battery pack according to its use requirements.

Fig. 7 is an apparatus as one example. The device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the device for the secondary battery, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a lithium ion secondary battery can be used as a power source.

Examples

Hereinafter, embodiments of the present application are described. The following examples are illustrative only and are not to be construed as limiting the application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention. The content of each component in the examples of the present application is by mass unless otherwise specified.

Preparation example 1

3G of polyacrylonitrile (manufactured by basf, number average molecular weight 90000) was dissolved in acetone to prepare a spinning solution. And standing and defoaming the prepared spinning solution for 6 hours. Then, the obtained spinning solution was injected into an electrostatic spinning device, the feeding speed was set to 6ml/min, the receiving distance was set to 10cm, the rotational speed was set to 500rpm/min, the voltage was set to 20kV, and the spinning solution was spun by an electrostatic spinning method to obtain hollow fibers. The obtained hollow fiber and a ferroferric oxide powder (particle diameter: 50 nm) were added to 100g of ethanol, and dispersed by ultrasonic waves to obtain a mixture. The obtained mixture was put into a ball mill and pulverized at 500rpm/min for 6 hours to obtain a pulverized product. The resulting mixture was placed in a vacuum oven and dried at 45 ℃ for 12 hours, thereby obtaining a hollow fiber composite 1.

Preparation examples 2 to 11

Hollow fiber composites 2 to 7 and 20 to 23 were produced in the same manner as in production example 1, except that the types of the polymers used, the types of the organic solvents, the types of the additives used in the step of producing the dope, the spinning method, and the types of the magnetic particles were changed as shown in table 1.

Hollow fiber composites 8 to 19 and 24 to 25 were produced in the same manner as in production example 1, except that production conditions such as the types and amounts of additives were changed.

For each of the hollow fiber composites obtained as described above, the average pore diameter, average fiber length, and average particle diameter of the magnetic particles of the hollow fibers can be measured by the following methods. The results obtained are shown in table 2 below.

1. Determination of the average pore size of hollow fibers

The obtained hollow fiber composites were photographed at a magnification of 1000 times by a Scanning Electron Microscope (SEM), and the maximum pore diameters of any 30 micropores in the obtained photographs were measured and averaged to obtain average pore diameters of the hollow fiber composites. Since the particle diameter of the magnetic particles is nano-scale, the pore diameter of the hollow fiber composite is substantially equal to the pore diameter of the hollow fibers, and thus the average pore diameter of the obtained hollow fiber composite is taken as the average pore diameter of the hollow fibers.

2. Measurement of average fiber diameter of hollow fiber

The obtained hollow fiber composites were photographed at a magnification of 1000 times by a Scanning Electron Microscope (SEM), and the fiber diameters of any 30 fibers in the obtained photographs were measured and averaged to obtain average fiber diameters of the hollow fiber composites. Since the particle diameter of the magnetic particles is nano-scale, the fiber diameter of the hollow fiber composite is substantially equal to the fiber diameter of the hollow fibers, and thus the average fiber diameter of the obtained hollow fiber composite is taken as the average fiber diameter of the hollow fibers.

3. Measurement of average fiber length of hollow fiber

The respective obtained hollow fiber composites were photographed by a Scanning Electron Microscope (SEM), and the fiber lengths of any 30 fibers in the obtained photographs were measured and averaged to obtain an average fiber length of the hollow fiber composites.

4. Determination of the average particle size of magnetic particles

The average particle diameter D50 of the magnetic particles as a raw material was measured as an average particle diameter of the magnetic particles in the hollow fiber composite by using a laser particle Size analyzer (model: MALVERN MASTER Size 3000) with reference to standard GB/T19077.1-2016.

Example 1

Preparation of positive electrode plate

The positive electrode active material LiNi _0.96Co_0.02Mn_0.02O₂ (NCM 96), the hollow fiber composite 1 prepared as described above, conductive carbon black (Super-P) and carbon nanotubes as a conductive agent, and polyvinylidene fluoride as a binder were added to N-methylpyrrolidone in a mass ratio of 93:5:0.6:0.2:1.2, and sufficiently stirred to prepare a slurry having a solid content of 68%. The obtained slurry was coated on the surfaces of both sides of a 10 μm aluminum foil as a current collector in a state where an external magnetic field was applied by a magnet, and dried and cold-pressed to obtain a positive electrode sheet.

Preparation of negative electrode plate

Mixing a negative electrode active material SiO, conductive carbon black (Super-P), a carbon nano tube and sodium carboxymethylcellulose according to a mass ratio of 96.8:1.04:0.06:2.1, adding into deionized water, fully stirring and mixing to form uniform negative electrode slurry, coating the obtained negative electrode slurry on the surface of a copper foil with the thickness of 4.5 mu m of a negative electrode current collector, and drying, cold pressing, slitting and cutting to obtain a negative electrode plate.

Isolation film

A polyethylene film was used as the separator film.

Preparation of electrolyte

Trade name 8950FB manufactured by national wav chemical materials limited was used as the electrolyte.

Preparation of a Battery

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, so that the isolating film is positioned in the middle of the positive electrode and the negative electrode to play a role in isolation, and winding to obtain the electrode assembly. And placing the electrode assembly in an outer package, injecting the prepared electrolyte, and packaging to obtain the battery.

Examples 2 to 30 and comparative examples 1 to 4

Similar to the preparation of example 1, the difference is that: different hollow fiber composites or different contents of the hollow fiber composites are selected in the membrane, and the specific details are shown in the following table 2.

The following parameter measurements were performed on the diaphragms in examples 1 to 30 and comparative examples 1 to 4, and the obtained results are shown in table 3 below.

1. Determination of the average depth of the through-holes

The obtained hollow fiber composite was cut, the cross section was ion polished, the depth of the through-hole at 10 was measured by a scanning electron microscope, and the average value was taken as the average depth of the through-hole.

2. Determination of the open pore ratio

The aperture ratio of the membrane was calculated using the following equation.

Aperture ratio = N x pi (R/2) ²/S

Wherein N is the number of through holes on the membrane, R is the average pore diameter of the hollow fiber compound in the membrane, and S is the area of the membrane.

The following performance tests were performed on the batteries obtained in examples 1 to 30 and comparative examples 1 to 4, and the obtained results are shown in table 3 below.

1. Determination of energy Density

The resulting battery was allowed to stand at a high temperature of 45℃for 24 hours. The battery after standing at high temperature is kept stand for 12 hours, then is charged to 3.5V by constant current of 0.02C, is discharged to 4.6V by constant current of 0.1C, is charged to 0.02C by constant voltage of 4.6V, is kept stand for 3 minutes, is discharged to 2.5V by constant current of 0.1C again, and is depressurized, pumped and sealed, so that the formation and the separation of the battery are realized. The battery after completion of the formation of the capacity was allowed to stand for 5 minutes, charged to 4.25V at a constant current of 0.5C, then charged to 0.05C at a constant voltage, and after the standing for 5 minutes, discharged to 2.5V at a constant current of 0.5C, the actual capacity at that time was recorded, and the obtained value was divided by the mass of the battery to obtain the energy density (unit: W.h/kg).

2. Determination of rate capability

After the battery after completion of the formation of the components was allowed to stand at 25℃for 30 minutes, it was discharged to 2.0V at a constant current of 0.1C, after 1 hour of standing, it was charged to 4.25V at a constant current of 0.1C, then it was allowed to stand for 30 minutes, it was discharged to 2.0V at a constant current of 0.1C, it was charged to 4.25V at a constant current of 0.1C, it was charged to 0.02C at a constant voltage of 1 hour of standing, and the actual capacity thereof was recorded as C0. Then, the mixture was discharged to 2.0V at a constant current of 0.2C, allowed to stand for 1 hour, charged to 4.25V at a constant current of 0.1C, charged to 0.02C at a constant voltage, allowed to stand for 30 minutes, discharged to 2.0V at a constant current of 0.33C, and the actual capacity thereof was recorded as C1, and C1/C0 was taken as a rate characteristic at 0.33C. Then, the mixture was allowed to stand for 1 hour, charged to 4.25V at a constant current of 0.1C, charged to 0.02C at a constant voltage, and allowed to stand for 30 minutes, discharged to 2.0V at a constant current of 0.5C, and allowed to stand for 1 hour. Then, the mixture was charged to 4.25V at a constant current of 0.1C, charged to 0.02C at a constant voltage, left to stand for 30 minutes, discharged to 2.0V at a constant current of 1C, left to stand for 1 hour, charged to 4.25V at a constant current of 0.1C, charged to 0.02C at a constant voltage, left to stand for 30 minutes, discharged to 2.0V at a constant current of 2C, left to stand for 1 hour, and the actual capacity C2 at that time was recorded, and C2/C0 was taken as the rate characteristic at 2C.

3. Determination of the wetting time of an electrolyte to a pole piece

And for the battery which is just injected with the electrolyte, measuring the internal resistance of the battery every other hour by using a battery internal resistance tester, and taking the time when the internal resistance of the battery is not changed as the soaking time of the electrolyte to the pole piece.

TABLE 3

As is clear from the results of table 3, in the case of not having the hollow fiber composite of the present application, although the active material is not lost and the energy density is high, the rate characteristics at 0.33C and the rate characteristics at 2C are both poor, and the wetting time of the electrolyte to the electrode sheet is too long, which is not advantageous for industrial production. In addition, in the case where the hollow fiber composite does not contain magnetic particles, although the wetting time of the electrolyte to the pole piece is shortened, the rate characteristics at 0.33C and 2C are both poor. Further, in the case where the average pore diameter of the hollow fiber composite is smaller than the range of the present application, the rate characteristics at 0.33C and the rate characteristics at 2C are also poor, and the wetting time of the electrolyte to the pole piece becomes excessively long. In the case where the average pore diameter of the hollow fiber composite exceeds the range of the present application, the wetting time of the electrolyte increases, but the rate characteristics at 0.33C and the rate characteristics at 2C remain poor. On the other hand, in the case of having the hollow fiber composite of the present application, it is possible to achieve both high energy density and excellent rate characteristics and to shorten the wetting time of the electrolyte to the pole piece.

Example 31

A battery was produced in the same manner as in example 1, except that the hollow fiber composite 3 was not added to the positive electrode separator and 5% of the hollow fiber composite 3 was added to the negative electrode separator. In addition, parameters of the membrane and performance of the battery were evaluated in the same manner as in example 1. The results obtained are shown in table 4 below.

TABLE 4

From the results of table 4, it is clear that when the hollow fiber composite of the present application is contained in the negative electrode sheet, the high energy density and excellent rate characteristics can be simultaneously achieved, and the wetting time of the electrode sheet with the electrolyte can be shortened, as compared with the case where the negative electrode sheet does not contain the hollow fiber composite.

It will be understood by those of ordinary skill in the art that the foregoing embodiments are merely illustrative of some of the embodiments that the application may be practiced with various changes and modifications in form and detail that are within the scope of the application.

Claims

1. The pole piece is characterized by comprising a current collector and a membrane arranged on at least one surface of the current collector, wherein the membrane comprises a hollow fiber composite, a through hole is formed in the membrane by the hollow fiber composite, and the average depth of the through hole is 20-200 mu m;

wherein the hollow fiber composite comprises:

Hollow fiber; and

Magnetic particles distributed on at least a part of the surface of the hollow fibers,

The average pore diameter of the hollow fiber is 3-40 mu m.

2. The pole piece of claim 1,

The average pore diameter of the hollow fiber is 5-30 mu m.

3. The pole piece of claim 1,

The average fiber diameter of the hollow fiber is 4-60 mu m.

4. The pole piece of claim 1,

The average fiber diameter of the hollow fiber is 5-30 μm.

5. The pole piece of any of claims 1 to 4,

The average fiber length of the hollow fibers is 30-100 mu m.

6. The pole piece of any of claims 1 to 4,

The average fiber length of the hollow fibers is 40-80 mu m.

7. The pole piece of any of claims 1-4, wherein,

The hollow fiber is composed of a polymer, and the electrical conductivity of the polymer is 5X 10 ^-5S/m ~ 5×10^-3 S/m.

8. A pole piece according to claim 7, characterized in that the polymer is selected from one or more of polyacrylonitrile, polyurethane, polypropylene.

9. The pole piece of any of claims 1-4, wherein,

The magnetic material constituting the magnetic particles is one or more selected from the group consisting of ferroferric oxide, alnico, iron-chromium-cobalt alloy, and iron-silicon alloy.

10. The pole piece of any of claims 1-4, wherein,

The average particle diameter of the magnetic particles is 1 nm-100 nm.

11. The pole piece of any of claims 1-4, wherein,

The average particle diameter of the magnetic particles is 1 nm-50 nm.

12. The pole piece of any of claims 1-4, wherein,

The mass ratio of the magnetic particles to the hollow fibers is 1:20-2:10.

13. A pole piece according to any of claims 1-4, characterized in that the average depth of the through holes is 30 μm to 100 μm.

14. The pole piece of any of claims 1 to 4,

The aperture ratio of the membrane is 1% -10%.

15. The pole piece of any of claims 1 to 4,

The aperture ratio of the membrane is 2% -5%.

16. The pole piece of any of claims 1 to 4,

The thickness of the membrane is 200-1000 mu m.

17. The pole piece of any of claims 1 to 4,

The thickness of the membrane is 250-600 mu m.

18. The pole piece of any of claims 1 to 4,

The mass percentage of the hollow fiber compound in the membrane is 1% -10%.

19. The pole piece of any of claims 1 to 4,

The mass percentage of the hollow fiber compound in the membrane is 3% -5%.

20. The pole piece of any of claims 1 to 4,

The pole piece is a pole piece for a positive electrode or a pole piece for a negative electrode.

21. The pole piece of any of claims 1 to 4,

The pole piece is a pole piece for the positive electrode.

22. A method of manufacturing a pole piece according to any of claims 1 to 21, wherein the pole piece comprises a current collector and a membrane disposed on at least one surface of the current collector, the membrane comprising a hollow fiber composite; wherein the method for producing the hollow fiber composite comprises the steps of,

spinning the prepared spinning solution to obtain the hollow fiber;

And drying the obtained pulverized product to obtain a hollow fiber composite.

23. The method of manufacturing a pole piece of claim 22,

The spinning solution also comprises an additive, wherein the additive is an organic additive and/or an inorganic additive, and the organic additive and/or the inorganic additive are/is selected from one or more of polyethylene glycol, polyvinylpyrrolidone, potassium chloride, calcium chloride, sodium chloride, lithium bromide and lithium nitrate.

24. A method of manufacturing a pole piece as claimed in claim 22 or 23, wherein,

The organic solvent in the spinning solution is a solvent that dissolves the polymer.

25. A method of manufacturing a pole piece as claimed in claim 22 or 23, wherein,

The organic solvent in the spinning solution is selected from one or more of acetone, tetrahydrofuran, N-dimethylformamide and N, N-dimethylacetamide.

26. A method of manufacturing a pole piece as claimed in claim 22 or 23, wherein,

The spinning method is a wet spinning method.

27. A method of manufacturing a pole piece as claimed in claim 22 or 23, wherein,

The spinning method is an electrostatic spinning method.

28. A method of manufacturing a pole piece as claimed in claim 22 or 23, wherein,

The solvent in which the hollow fibers and the magnetic particles are dispersed is a solvent in which the hollow fibers and the magnetic particles are not dissolved and are uniformly dispersed, and the solvent is one or more selected from water and alcohol.

29. A method of manufacturing a pole piece as claimed in claim 22 or 23, wherein,

The solvent in which the hollow fibers and the magnetic particles are dispersed is water and/or ethanol.

30. A battery, comprising: a pole piece according to any one of claims 1 to 21, or produced by the method of manufacturing a pole piece according to any one of claims 22 to 29.

31. A battery module comprising the battery of claim 30.

32. A battery pack comprising the battery module of claim 31.

33. An apparatus comprising at least one of the battery of claim 30, the battery module of claim 31, or the battery pack of claim 32.