CN114730966B

CN114730966B - Electrochemical devices and electrical equipment

Info

Publication number: CN114730966B
Application number: CN202180006432.1A
Authority: CN
Inventors: 张益博
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2021-06-22
Filing date: 2021-06-22
Publication date: 2024-12-03
Anticipated expiration: 2041-06-22
Also published as: CN114730966A; WO2022266866A1

Abstract

An electrochemical device (100) and an electrical equipment (200), wherein the electrochemical device (100) comprises a separator (30) and a plurality of electrode assemblies (50) located in a housing (10), wherein the separator (30) comprises a heating element (301). The electrochemical device (100) and the electrical equipment (200) embed the heating element (301) inside the separator (30), thereby realizing the ion insulation function of the separator (30) and ensuring the reliability of the package, and realizing the heating function of the electrochemical device (100) by utilizing the heating element (301) in the middle layer, thereby effectively improving the problems of poor mechanical strength and thermal stability of the separator (30) in the prior art, and at the same time, improving the problems of reduced energy density, serious self-discharge, reliability risk, etc. caused by the internal heating method in the prior art.

Description

Electrochemical device and electric equipment

Technical Field

The application relates to the technical field of batteries, in particular to an electrochemical device and electric equipment.

Background

At present, a multi-battery serial connection method is generally adopted to improve the output voltage, but the multi-battery serial connection has a plurality of problems, such as lower overall Energy Density (ED) caused by capacity difference among battery units, extra electronic resistance introduced by a serial connection lead and contact resistance, energy waste caused by heating, higher voltage requires more batteries, and the difficulty of battery management is improved. In order to solve the above-mentioned problems, a concept of a high-output voltage battery is proposed. The design concept of the high-output voltage battery is realized, the electrode assemblies of the battery are required to be assembled in series, the separator plates in the series structure are required to realize the ion insulation function (ion non-conduction) of the series cavity, internal short circuits of cathodes and anodes with different potentials are avoided, and meanwhile, the decomposition failure of electrolyte under high voltage is avoided. In addition, as a part of the packaging structure, the mechanical strength, thermal stability and other parameters of the separator are required to meet certain requirements.

The lithium ion battery has poor dynamics under the low temperature condition, so that the low temperature charging capability is poor, the high-rate charging in the low temperature environment of the battery causes serious lithium precipitation of an anode to cause safety risk, and meanwhile, the electrode material has lower activity under the low temperature condition, so that the capacity exertion is lower, and the energy density is lost. In a low-temperature environment, the battery chemical system dynamics is improved by heating the battery, so that the problems of low capacity and anode lithium precipitation of the lithium ion battery in the low-temperature environment can be effectively relieved. The common external heating mode has the advantages of low heating rate in the heating process, large temperature difference among all parts of the battery, large influence on electrode materials, deterioration of the battery cycle performance and safety and reliability risks. The heating plate heat source is embedded into the battery, the temperature rise rate is high, the temperature difference among the parts of the battery is small, and the damage to the battery is small. However, the embedding of the heating sheet has the problems of reduced energy density, degraded interface contact, serious self-discharge problem, reliability risk in drop test and the like, and an innovative scheme needs to be developed to solve the problems.

Disclosure of Invention

In view of the above, the present application provides a new electrochemical device and electrical equipment to optimize the separator performance of a high-output voltage battery, and improve the problems of reduced energy density, interface contact degradation, serious self-discharge problem, and reliability risk in drop test caused by the heating element inside the battery.

A first aspect of the present application provides an electrochemical device comprising a separator and a plurality of electrode assemblies within a housing, the separator comprising a heating element. The heating element is embedded into the partition board, so that the ion insulation function of the partition board can be realized, the packaging reliability is ensured, meanwhile, the heating function of the electrochemical device can be realized by utilizing the heating element of the middle layer, the problems of poor mechanical strength and thermal stability of the partition board in the prior art are effectively improved, and meanwhile, the problems of low energy density, serious self-discharge problem, reliability risk and the like caused by an internal heating mode in the prior art are improved.

In some embodiments, the plurality of electrode assemblies are disposed in a plurality of cavities within the housing separated by the separator, respectively.

In some embodiments, the electrochemical device further comprises a first terminal and a second terminal electrically connected to the heating element, wherein a first resistance R1 is provided between the first terminal and the second terminal, such that R1 is greater than or equal to 5mΩ. Further, R1 is not less than 20mΩ. When the temperature of the electrochemical device is lower than the normal operation temperature (e.g., lower than about 5 ℃), the first terminal and the second terminal will be connected to the heating circuit and heat the electrochemical device, since the resistance R1 is much greater than the internal resistance of the electrochemical device when it is operating normally, and the current of the heating circuit can be conveniently increased when it is charged, the internal temperature of the electrochemical device will be rapidly increased, and thus the electrochemical performance of the electrochemical device can be rapidly improved.

In some embodiments, the electrode assembly comprises a first tab and a second tab with opposite polarities, and an internal resistance R is arranged between the first tab and the second tab in the same electrode assembly, so that R1/R is more than or equal to 0.05 and less than or equal to 5000. Further, R1/R1000 is smaller than or equal to 1.

In some embodiments, at least one of the first tabs is electrically connected to the first terminal.

In some embodiments, at least two electrode assemblies are connected in series.

In some embodiments, the separator further comprises an insulating layer located on at least one side of the heating element. The separator adopts the structure, compared with a metal-based current collector, the separator has smaller probability of generating conductive scraps under mechanical abuse conditions (through nails, impact, extrusion and the like), and has better effect of wrapping the surface of mechanical damage, so that the safety boundary under the mechanical abuse conditions can be improved, and the safety test passing rate is improved.

In some embodiments, the heating element comprises a patterned shape.

In some embodiments, the insulating layer comprises at least one of a polymer or an inorganic insulating material.

In some embodiments, the separator further comprises an encapsulation layer on a surface of the insulating layer.

In some embodiments, the interfacial adhesion force F between the separator and the housing satisfies F.gtoreq.10N/cm.

In some embodiments, the patterned shape includes a plurality of first portions arranged in parallel, two adjacent first portions are connected by a second portion, the two adjacent first portions are arranged at intervals, an insulator is arranged between the two adjacent first portions, and the material of the insulator includes at least one of a polymer or an inorganic insulating material.

In some embodiments, the material of the encapsulation layer includes at least one of polypropylene, anhydride modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous alpha-olefin copolymer, and derivatives thereof.

In some embodiments, the polymer comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene naphthalate, polypropylene carbonate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene oxide, polyester, polysulfone, amorphous alpha-olefin copolymer, and at least one of the derivatives of the foregoing.

In some embodiments, the inorganic insulating material comprises at least one of hafnium oxide, strontium titanate, tin oxide, cerium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide, or aluminum hydroxide.

In some embodiments, the material of the heating element comprises at least one of a carbon material or a metal material.

In some embodiments, the thickness H of the separator satisfies that H.gtoreq.2 μm.

In some embodiments, the carbon material comprises at least one of a carbon felt, a carbon film, carbon black, acetylene black, fullerenes, conductive graphite film, or graphene film, and the metal material comprises at least one of nickel, titanium, copper, silver, gold, platinum, iron, cobalt, chromium, tungsten, molybdenum, aluminum, magnesium, potassium, sodium, calcium, strontium, barium, silicon, germanium, tin, lead, indium, zinc, or stainless steel.

The second aspect of the application also provides an electrical consumer comprising an electrochemical device as described above.

In some embodiments, the powered device further comprises a switch. When the temperature is below T1 or above T2, the switch is closed, allowing current to pass through the heating element.

In some embodiments, T1 is 5 ℃ and T2 is 50 ℃.

According to the electrochemical device and the electric equipment, the heating element is embedded into the partition board, so that the ion insulation function of the partition board can be realized, the packaging reliability is ensured, meanwhile, the heating function of the electrochemical device can be realized by utilizing the heating element of the middle layer, the problems of poor mechanical strength and thermal stability of the partition board in the prior art are effectively solved, and meanwhile, the problems of low energy density, serious self-discharge problem, reliability risk and the like caused by an internal heating mode in the prior art are solved.

Drawings

The application will be described in further detail with reference to the drawings and the detailed description.

Fig. 1 is a schematic view of an electrochemical device according to an embodiment of the present application.

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

Fig. 3 is a schematic structural view of a separator according to an embodiment of the present application.

Fig. 4 is a schematic structural diagram of a heating element according to an embodiment of the present application.

Fig. 5 is a schematic structural view of a separator according to an embodiment of the present application.

Fig. 6 is a schematic structural diagram of a separator according to an embodiment of the present application.

Fig. 7 is a block diagram of an electric device according to an embodiment of the present application.

Description of main reference numerals:

electrochemical device 100

Electric equipment 200

Housing 10

Baffle plate 30

Electrode assembly 50

First electrode assembly 51

Second electrode assembly 52

Heating element 301

Insulating layer 302

Encapsulation layer 303

Insulator 304

First tab 501

Second lug 502

First terminal 3010

Second terminal 3014

First portion 3011

Second portion 3012

The following detailed description will further illustrate embodiments of the application in conjunction with the above-described drawings.

Detailed Description

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the application belong. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the application.

It should be noted that all directional indicators (such as up, down, left, right, front, and rear are used in the embodiments of the present application) are merely for explaining the relative positional relationship, movement conditions, and the like between the components in a certain specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicators are changed accordingly.

In addition, descriptions such as those related to "first," "second," and the like in this disclosure are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present application, unless explicitly specified and limited otherwise, the terms "connected," "fixed" and the like are to be construed broadly, and for example, "fixed" may be fixedly connected, detachably connected or integrally formed, mechanically connected, electrically connected, directly connected, indirectly connected through an intervening medium, and may be in communication between two elements or in an interaction relationship between two elements, unless otherwise explicitly specified. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

Referring to fig. 1, the present application provides an electrochemical device 100 including a case 10, at least one separator 30, and a plurality of electrode assemblies 50. The at least one separator 30 divides the interior of the case 10 into a plurality of cavities in which the plurality of electrode assemblies 50 are respectively disposed. In this embodiment, the number of separators 30 is one, and the plurality of electrode assemblies 50 includes a first electrode assembly 51 and a second electrode assembly 52. The first electrode assembly 51 and the second electrode assembly 52 are respectively disposed in two cavities within the case 10 partitioned by the separator 30, and the separator 30 includes a heating element 301 (refer to fig. 2). It is understood that N separators 30 may partition the case 10 to form n+1 chambers, and n+1 electrode assemblies may be respectively located in the formed n+1 chambers. The electrode assembly 50 may be a wound or laminated structure, and the present application is not limited thereto.

As shown in FIG. 1, the electrochemical device 100 further includes a first terminal 3010 and a second terminal 3014 electrically connected to the heating element 301, and a first resistance R1 is provided between the first terminal 3010 and the second terminal 3014, so that R1 is equal to or greater than 5mΩ.

When the temperature of the electrochemical device 100 is lower than the normal operation temperature (e.g., lower than about 5 ℃), the first terminal 3010 and the second terminal 3014 will be connected to the heating circuit and heat the electrochemical device 100, and since the resistance R1 may be much greater than the internal resistance of the electrochemical device when it is operating normally and the current of the heating circuit may be conveniently increased when it is charged, the internal temperature of the electrochemical device 100 will be rapidly increased, so that the electrochemical performance of the electrochemical device 100 may be rapidly improved.

As shown in fig. 1, the first electrode assembly 51 includes a first tab 501 and a second tab 502, which are opposite in polarity. An internal resistance R is arranged between the first tab 501 and the second tab 502, and R1/R is more than or equal to 0.05 and less than or equal to 5000. Further, R1/R1000 is smaller than or equal to 1.

Further, at least one of the first tabs 501 is electrically connected to the first terminal 3010.

In some embodiments, at least two electrode assemblies 50 are connected in series. In fig. 1, a first tab 501 in a first electrode assembly 51 is connected to a second tab 502 in a second electrode assembly 52 to achieve series connection.

Referring to fig. 2, the separator 30 includes a heating element 301 and an insulating layer 302, and the insulating layer 302 is located on at least one side of the heating element 301. In fig. 2, the case is shown where the insulating layer 302 is located on opposite sides (in the thickness direction of the separator 30) of the heating element 301, and the insulating layer 302 may be located on only one side of the heating element 301. By adopting the above structure, compared with the metal-based current collector, the separator 30 has smaller probability of generating conductive scraps under mechanical abuse conditions (through nails, impact, extrusion and the like) and better effect of wrapping the surface of mechanical damage, so that the safety boundary under the mechanical abuse conditions can be improved, and the safety test passing rate is improved.

Further, the separator 30 further includes an encapsulation layer 303 on the surface of the insulating layer 302. In fig. 2, the encapsulation layer 303 is located at the end edge of the insulating layer 302 for encapsulation, that is, the main surface portion of the insulating layer 302 is exposed outside the separator 30 without being covered by the encapsulation layer 303. The area of the encapsulation layer 303 is reduced as much as possible, and the proportion of inactive substances is reduced, so that the energy density of the electrochemical device can be improved. It is understood that the encapsulation layer 303 may also entirely cover the insulating layer 302 so that the main body surface thereof is not exposed, as shown in fig. 3.

In some embodiments, the material of the encapsulation layer 303 has a low melting point and can be used as a material for packaging the housing, and the materials of the heating element 301 and the encapsulation layer 303 have good ion insulation capability, a certain thermal stability, and other characteristics. The melting point (softening point) of the heating element 301 is greater than 130 ℃, preferably greater than 150 ℃. The melting point (softening point) of the encapsulation layer 303 ranges from 120 ℃ to 240 ℃, preferably 130 ℃ to 170 ℃. Furthermore, the melting point of the heating element 301 is at least 10 ℃, preferably more than 20 ℃, higher than the melting point (softening point) of the encapsulation layer 303, thereby ensuring reliability of the encapsulation and effectiveness of ion isolation.

Further, the material of the encapsulation layer 303 includes at least one of polypropylene, anhydride modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous α -olefin copolymer, and derivatives thereof. The heating element 301 comprises at least one of a carbon material or a metal material. The carbon material comprises at least one of a carbon felt, a carbon film, carbon black, acetylene black, fullerene, a conductive graphite film or a graphene film, and the metal material comprises at least one of nickel (Ni), titanium (Ti), copper (Cu), silver (Ag), gold (Au), platinum (Pt), iron (Fe), cobalt (Co), chromium (Cr), tungsten (W), molybdenum (Mo), aluminum (Al), magnesium (Mg), potassium (K), sodium (Na), calcium (Ga), strontium (Sr), barium (Ba), silicon (Si), germanium (Ge), tin (Sb), lead (Pb), indium (In), zinc (Zn) or stainless steel.

Referring to fig. 4, the heating element 301 includes a patterned shape including a plurality of first portions 3011 disposed in parallel, and two adjacent first portions 3011 are connected by a second portion 3012. In fig. 4, the heating element 301 is shown as a continuous zigzag pattern, but the heating element pattern may be other shapes, for example, two adjacent first portions 3011 are arranged in parallel at a distance, etc. The heating element 301 may not include the patterned shape, and may be a single integral piece of continuous conductive material.

Further, an insulator 304 is provided between adjacent first portions 3011. The material of the insulating layer 302 includes at least one of a polymer and an inorganic insulating material, and the material of the insulator 304 includes at least one of a polymer and an inorganic insulating material. The insulator 304 and the insulating layer 302 may ensure ion insulation on both sides of the separator 30.

Further, the polymer includes polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene naphthalate, polypropylene carbonate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate (EEA), ethylene-acrylic acid copolymer (EAA), ethylene-vinyl alcohol copolymer (EVAL), polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene oxide, polyester, polysulfone, amorphous alpha-olefin copolymer, and at least one of derivatives of the foregoing.

Further, the inorganic insulating material includes at least one of hafnium oxide (HfO ₂), strontium titanate (SrTiO ₃), tin oxide (SnO ₂), cerium oxide (CeO ₂), magnesium oxide (MgO), nickel oxide (NiO), calcium oxide (CaO), barium oxide (BaO), zinc oxide (ZnO), zirconium dioxide (ZrO ₂), yttrium oxide (Y ₂O₃), aluminum oxide (Al ₂O₃), titanium dioxide (TiO ₂), silicon dioxide (SiO ₂), boehmite, magnesium hydroxide (Mg (OH) ₂), or aluminum hydroxide (Al (OH) ₃).

Referring to fig. 5, the separator 30 includes a heating element 301 and an encapsulation layer 303 on a surface of the heating element 301, i.e., the separator 30 may not include an insulation layer 302. In fig. 5, the encapsulation layer 303 is shown completely covering the surface of the heating element 301, and the encapsulation layer 303 may be located only in the area for encapsulation at the end edges of the insulating layer 302, i.e. the main body surface portion of the heating element 301 is exposed and not covered by the encapsulation layer 303, as shown in fig. 6.

Further, the heating element 301 shown in fig. 5 and 6 may also comprise the patterned shape shown in fig. 4, i.e. comprise a plurality of first portions 3011 arranged in parallel, adjacent two first portions 3011 being connected by a second portion 3012. Further, an insulator 304 is provided between adjacent first portions 3011. Likewise, the heating element 301 may not include the patterned shape, and may be a single integral piece of continuous conductive material.

In some embodiments, the thickness H of the separator 30 ranges from 2 μm to 1000 μm, preferably from 5 μm to 50 μm, more preferably from 5 μm to 20 μm. In some embodiments, the interfacial adhesion force F between the separator 30 and the housing 10 is such that F is greater than or equal to 10N/cm, preferably F is greater than or equal to 15N/cm.

Referring to fig. 7, the present application further provides an electrical device 200, which includes the electrochemical apparatus 100 described above.

In some embodiments, the powered device 200 further comprises a switch. When the temperature is below T1 or above T2, the switch is closed, allowing current to pass through the heating element 301.

Further, T1 is 5 ℃ and T2 is 50 ℃.

The present application will be described in further detail with reference to specific examples.

Example 1

① The preparation of the negative electrode plate comprises the steps of mixing negative electrode active material graphite, conductive carbon black (Super P) and Styrene Butadiene Rubber (SBR) according to a weight ratio of 96:1.5:2.5, adding deionized water, preparing into slurry with solid content of 0.7, and uniformly stirring. The slurry was uniformly coated on a negative current collector copper foil and dried at 110 ℃. After the steps are finished, the single-sided coating of the negative electrode plate is finished. These steps are then completed in a completely uniform manner on the back side of the pole piece. And then cold pressing, cutting and other working procedures are carried out to finish the preparation of the negative electrode plate.

② The preparation of the positive electrode plate comprises the steps of mixing positive electrode active materials of lithium cobaltate (LiCoO ₂), conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) according to the weight ratio of 97.5:1.0:1.5, adding N-methyl pyrrolidone (NMP), preparing into slurry with the solid content of 0.75, and uniformly stirring. The slurry was uniformly coated on an anode current collector aluminum foil and dried at 90 ℃. These steps are then completed in a completely uniform manner on the back side of the pole piece. And then cold pressing, cutting and other working procedures are carried out to finish the preparation of the positive pole piece.

③ In the preparation of the electrolyte, in a dry argon atmosphere, organic solvents of Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) are firstly mixed according to the mass ratio of EC to DEC=30:50:20, and then lithium hexafluorophosphate (LiPF ₆) serving as a lithium salt is added into the organic solvent to be dissolved and uniformly mixed, so that the electrolyte with the concentration of the lithium salt of 1.15M is obtained.

④ And preparing an electrode assembly, namely selecting Polyethylene (PE) with the thickness of 15 mu m as a separation membrane, sequentially stacking the positive electrode plate, the separation membrane and the negative electrode plate, and then rolling the stacked electrode plate and the separation membrane into a coiled electrode assembly.

⑤ Preparing a separator, namely uniformly dispersing polypropylene (PP) into N-methylpyrrolidone (NMP) serving as a dispersing agent to prepare a packaging layer suspension, preparing packaging layers (302 stainless steel serving as a heating element is prepared in advance, the first part is filled with an insulator) on two sides of the heating element by using a glue spreader, drying the NMP serving as the dispersing agent in the packaging layer suspension at 130 ℃, welding two lugs at the outermost end of the 302 stainless steel to serve as terminals for connecting a heating circuit, setting the resistance R1 between the two terminals to be 1.23 omega, and pasting glue paper to complete the preparation of the separator, wherein the structure of the separator is shown in fig. 5. The separator has a thickness of 20 μm, wherein the heating element 302 stainless steel has a melting point (softening point) of 1440 ℃ and the encapsulation PP has a melting point (softening point) of 150 ℃ with a difference of 1290 ℃.

⑥ And (3) assembling the lithium ion battery, namely placing a shell (an aluminum plastic film with the thickness of approximately 90 mu m) formed by punching the pit into the assembling clamp 1, placing the first electrode assembly into the pit with the pit face upwards, then placing the separator above the first electrode assembly, and applying external force to compress the separator.

⑦ And (II) assembling the lithium ion battery, namely placing the assembled semi-finished product obtained in the step I into an assembling clamp 2, enabling the exposed surface of a separator to face upwards, placing a second electrode assembly above the separator, compacting, covering the pit surface of the other shell above the second electrode assembly downwards, and heat-sealing the periphery.

⑧ And (4) filling and packaging, namely filling the two cavities with liquid separately, and packaging the periphery of the two cavities after filling the liquid, wherein the periphery of the partition board is sealed in the sealing process. The two electrode assemblies are separated into two independent sealed cavities by the separator, and no ion exchange is caused between the two electrode assemblies. And all lugs of the two electrode assemblies are led out of the shell for subsequent processing.

⑨ And (3) connecting the positive electrode tab of the first electrode assembly and the negative electrode tab of the second electrode assembly together through welding (laser welding, ultrasonic welding or resistance welding) to realize series connection conduction between the two electrode assemblies, so that the lithium ion battery is assembled.

Example 2

The difference from example 1 is that the material of the encapsulation layer is Polyethylene (PE), the melting point (softening point) of the encapsulation layer is 120 ℃ and the difference from the melting point (softening point) of the heating element is 1320 ℃.

Example 3

The difference from example 1 is that the material of the encapsulation layer is polystyrene, the melting point (softening point) of the encapsulation layer is 240 ℃ and the difference from the melting point (softening point) of the heating element is 1200 ℃.

Example 4

The difference from example 1 is that the heating element is made of copper (Cu), the melting point (softening point) of the heating element is 1080 ℃, the melting point (softening point) of the encapsulation layer PP is 130 ℃, and the difference from the melting point (softening point) of the heating element is 950 ℃.

Example 5

The difference from example 1 is that the heating element is made of aluminum (Al), the melting point (softening point) of the heating element is 660 ℃, the melting point (softening point) of the encapsulation layer PP is 130 ℃, and the difference from the melting point (softening point) of the heating element is 530 ℃.

Example 6

The difference from example 1 is that the heating element is made of carbon film, the melting point (softening point) of the heating element is 3500 ℃, the melting point (softening point) of the encapsulation layer PP is 150 ℃, and the difference from the melting point (softening point) of the heating element is 3350 ℃.

Example 7

The difference from example 1 is that the separator has a structure in which an insulating layer is further provided between the encapsulation layer and the insulator, the heating element is made of aluminum (Al), the melting point (softening point) of the heating element is 660 ℃, the melting point (softening point) of the encapsulation layer PP is 150 ℃, the difference from the melting point (softening point) of the heating element is 510 ℃, and the thickness of the separator is 10 μm, as shown in fig. 3.

Example 8

The difference from example 7 is that the thickness of the separator is 2 μm.

Example 9

The difference from example 7 is that the resistance R1 between the two terminals of the heating element is made 31.22Ω by changing the pitch of the first portions.

Example 10

The difference from example 7 is that the resistance R1 between the two terminals of the heating element is made 7.43 Ω by changing the pitch of the first portions.

Example 11

The difference from example 7 is that the resistance R1 between the two terminals of the heating element is made 0.2 Ω by changing the pitch of the first portions.

Example 12

The difference from example 7 is that the heating element is not textured and the resistance R1 between the two terminals of the heating element is 0.05 omega.

Comparative example 1

The difference from example 1 is that the lithium ion battery is assembled by packing an electrode assembly with an aluminum plastic film, and then forming an electrochemical device by injection molding and side encapsulation.

Comparative example 2

The difference from comparative example 1 is that two lithium ion batteries were fabricated in the same manner as comparative example 1. Welding the positive electrode tab of one lithium ion battery and the negative electrode tab of the other lithium ion battery together through a conducting piece

Comparative example 3

The difference from example 1 is that no separator was included.

Comparative example 4

The difference from example 1 is that a usual single-layer PP (polypropylene) was used directly as separator, with a melting point of 165℃and a thickness of 20. Mu.m. And a heating Ni sheet is embedded in the first electrode assembly.

The interfacial adhesion test comprises the steps of taking off a seal area part from a lithium ion battery to be used as a sample 1, cutting the sample 1 into a test strip with the width of 8mm, ensuring that the test strip completely stores the whole seal area to obtain a sample 2, tearing the separator and the shell at two sides by using a high-speed rail tension machine at an angle of 180 degrees to separate the separator and the shell from each other, recording the stable tension force F (N) during separation, and calculating based on the stable tension force F (N/cm) =f/0.8 to obtain the interfacial adhesion force F (N/cm) =f/0.8 of the separator and the shell.

1.5M drop test, namely disassembling the lithium ion battery with the drop of 1.5m, and independently taking down the sealing area for standby, dripping red liquid medicine in the sealing area, enabling the space dimension red liquid medicine to be above, enabling the sealing area to be below, standing for 12h, then destroying the sealing area through interface adhesion test, observing the condition that the red liquid medicine permeates into the sealing area, and judging that the packaging part is damaged if the depth of the red liquid medicine permeating into the sealing area exceeds 1/2 of the width of the sealing area, otherwise judging that the packaging part is not damaged. And testing 20 lithium ion batteries, and determining the damage proportion.

0.1C discharge energy density test a lithium ion battery was charged from 3.0V to 4.4V at a charge rate of 1C under 25 ℃ conditions, and then discharged to 3.0V at a discharge rate of 0.1C, and a 0.1C discharge capacity was determined, 0.1C discharge energy density = 0.1C discharge capacity/lithium ion battery volume.

And (3) testing the cycle capacity retention rate, namely charging the lithium ion battery from 3.0V to 4.4V at a charging rate of 2 ℃ under the environment of 25 ℃, and then discharging the lithium ion battery to 3.0V at a discharging rate of 0.2 ℃, determining the discharge capacity at the moment as the first discharge capacity, repeating the charge-discharge cycle for 50 times, and measuring the discharge capacity at the 50 th discharge, wherein the cycle capacity retention rate=the 50 th discharge capacity/the first discharge capacity.

3C charging temperature rise test the highest surface temperature of the lithium ion battery is tested when the lithium ion battery is charged from 0% state of charge (SOC) to 100% SOC at a charging rate of 3C in a 25 ℃ environment. 3C charge temperature rise = battery surface maximum temperature-25 ℃.

And (3) a lithium-ion battery is placed in an environment of minus 10 ℃ and an environment of minus 25 ℃ respectively, when the lithium-ion battery is placed in the environment of minus 10 ℃, the lithium-ion battery with a heating element firstly heats the battery to the highest temperature point of the surface of the battery to 25 ℃ with 50W power to start charging, the charging multiplying power when lithium-ion battery begins to be separated is determined, the lithium-ion battery without the heating element does not have the heating step, and the lithium-ion battery without the lithium-separation capability boundary = the charging multiplying power when lithium-separation begins in the environment of minus 10 ℃ and the charging multiplying power when lithium-separation begins in the environment of minus 25 ℃.

And (3) heating the lithium ion battery from minus 10 ℃ to a power of 50W, and testing the maximum temperature Difference (DEGC) of the battery surface when the highest temperature point of the battery surface is 25 ℃.

The parameter settings of the above examples and comparative examples are shown in Table 1, and the test results are shown in Table 2.

TABLE 1

TABLE 2

As can be seen from tables 1 and 2, the lithium ion batteries of examples 1 to 12 have energy densities comparable to that of the single lithium ion battery of comparative example 1, and have significantly improved energy densities compared to that of comparative example 2 (two lithium ion batteries in series), since the separators replace the two-layered case. From the results of comparative example 3, it is understood that the separators in examples 1 to 12 are effective in achieving an ion insulating function. Compared with comparative example 4, the maximum temperature difference of the surfaces of the lithium ion batteries in examples 1-12 is obviously reduced, the lithium-ion battery capacity boundary is obviously improved, the temperature equalizing capacity of the battery is obviously improved, and compared with comparative example 1, the 3C charging temperature rise is reduced, so that the high-rate charging and discharging performance of the battery is improved. In addition, the cycle capacity retention ratio of the lithium ion batteries in examples 1 to 12 was superior to that of comparative example 4, and it was found that the interface contact deterioration inside the lithium ion batteries was improved.

According to the electrochemical device and the electric equipment, the heating element is embedded into the partition board, so that the ion insulation function of the partition board can be realized, the packaging reliability is ensured, meanwhile, the heating function of the electrochemical device can be realized by utilizing the heating element of the middle layer, the problems of poor mechanical strength and thermal stability of the partition board in the prior art are effectively solved, and the problems of low energy density, serious self-discharge problem, reliability risk and the like caused by an internal heating mode in the prior art are also solved.

Claims

1. An electrochemical device, comprising at least one separator and a plurality of electrode assemblies located in a shell, wherein the at least one separator divides the interior of the shell into a plurality of cavities, the plurality of electrode assemblies are respectively arranged in the plurality of cavities, the separator comprises a heating element and a packaging layer, the packaging layer at least covers an area for packaging at an end edge of the heating element, and the packaging layer is packaged with the shell;

The electrochemical device also includes a first terminal and a second terminal electrically connected to the heating element, and a first resistance R1 is provided between the first terminal and the second terminal, satisfying: R1 ≥ 5 mΩ; the electrode assembly includes a first pole ear and a second pole ear with opposite polarities, and at least one of the first pole ears is electrically connected to the first terminal.

2. The electrochemical device according to claim 1, wherein an internal resistance R is provided between the first electrode tab and the second electrode tab in the same electrode assembly, and satisfies: 0.05≤R1/R≤5000.

3. The electrochemical device as claimed in claim 1, characterized in that at least two electrode assemblies are connected in series.

4. The electrochemical device according to claim 1, wherein the separator further comprises an insulating layer, and the insulating layer is located on at least one side of the heating element.

5. The electrochemical device according to claim 4, characterized in that at least one of the following conditions is satisfied:

i) the heating element comprises a patterned shape;

ii) The material of the insulating layer includes at least one of a polymer and an inorganic insulating material.

6. The electrochemical device according to claim 5, characterized in that at least one of the following conditions is satisfied:

a) The interfacial bonding force F between the partition and the shell satisfies: F ≥ 10 N/cm;

b) the patterned shape comprises a plurality of first parts arranged in parallel, two adjacent first parts are connected by a second part, and two adjacent first parts are arranged at intervals; an insulator is arranged between the adjacent first parts, and the material of the insulator comprises at least one of a polymer and an inorganic insulating material;

c) the material of the encapsulation layer includes at least one of polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous α-olefin copolymer and derivatives thereof;

d) the polymer includes at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylenenaphthalene, polyvinylidene fluoride, polyethylene naphthalate, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polysulfone, amorphous α-olefin copolymer and derivatives thereof;

e) the inorganic insulating material includes at least one of hafnium dioxide, strontium titanate, tin oxide, cerium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium dioxide, yttrium oxide, aluminum oxide, titanium dioxide, silicon dioxide, boehmite, magnesium hydroxide or aluminum hydroxide;

f) the material of the heating element includes at least one of a carbon material or a metal material;

g) The thickness H of the separator satisfies: H ≥ 2 μm.

7. The electrochemical device as described in claim 6 is characterized in that the carbon material includes at least one of carbon felt, carbon black, fullerene, conductive graphite film or graphene film; the metal material includes at least one of nickel, titanium, copper, silver, gold, platinum, iron, cobalt, chromium, tungsten, molybdenum, aluminum, magnesium, potassium, sodium, calcium, strontium, barium, silicon, germanium, tin, lead, indium, zinc or stainless steel.

8. An electrical equipment, characterized in that it comprises the electrochemical device according to any one of claims 1 to 7.

9. The electrical device according to claim 8, characterized in that the electrical device further comprises a switch; when the temperature is lower than T1 or higher than T2, the switch is closed to allow current to pass through the heating element.

10. The electrical equipment according to claim 9, characterized in that T1 is 5°C and T2 is 50°C.