CN118943335A

CN118943335A - Negative electrode active material, preparation method and application thereof

Info

Publication number: CN118943335A
Application number: CN202411093653.9A
Authority: CN
Inventors: 蒋世权; 曾力; 高云雷; 于子龙
Original assignee: Zhejiang Liwei Energy Technology Co ltd
Current assignee: Zhejiang Liwei Energy Technology Co ltd
Filing date: 2024-08-09
Publication date: 2024-11-12

Abstract

The invention discloses a negative electrode active material, and a preparation method and application thereof. The negative electrode active material comprises carbon spheres, wherein the carbon spheres comprise a silicon-based material and a phosphorus-based material, the mass fraction of the silicon-based material in the carbon spheres is M _si%, the mass fraction of the phosphorus-based material in the carbon spheres is M _P%, the electronic conductivity of the silicon-based material is sigma _si S/cm, and the electronic conductivity of the phosphorus-based material is sigma _P S/cm,M_si、M_P、σ_si and sigma _P, and the following conditions are satisfied: the negative electrode active material is used for the electrochemical energy storage device, so that the energy density of the electrochemical energy storage device can be ensured, the electron transmission rate can be improved, and the electrochemical performance can be improved.

Description

Negative electrode active material, preparation method and application thereof

Technical Field

The invention belongs to the technical field of battery materials, and particularly relates to a negative electrode active material, and a preparation method and application thereof.

Background

The lithium and sodium batteries are used as novel secondary batteries, have the advantages of high working voltage, high energy density, long service life, wide working temperature range, environmental friendliness and the like, and become main energy storage devices of mainstream electronic products. With the increasing demands of the market for battery performance, lithium batteries and sodium batteries with excellent performance are required to have higher energy density and excellent charge and discharge capability. In the traditional electrode slice preparation method, the content of active substances coated on the surface of a current collector is increased, so that the aim of improving the energy density of the battery is fulfilled. However, the current battery has poor cycle performance and rate capability, which affects the application of the battery to a certain extent.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides the negative electrode active material which is used for a secondary battery and has good cycle performance and multiplying power performance and good application prospect.

The invention also provides a preparation method of the anode active material.

The invention also provides a cathode material.

The invention also provides a negative electrode.

The invention also provides an electrochemical energy storage device.

The invention further provides electric equipment.

In a first aspect of the present invention, a negative electrode active material is provided, including a carbon sphere, where the carbon sphere includes a silicon-based material and a phosphorus-based material, the mass fraction of the silicon-based material in the carbon sphere is M _si%, the mass fraction of the phosphorus-based material in the carbon sphere is M _P%, the electronic conductivity of the silicon-based material is σ _si S/cm, and the electronic conductivity of the phosphorus-based material is between σ _P S/cm,M_si、M_P、σ_si and σ _P, where: m _Si*σ_P)/(1000*M_P*σ_Si)≤100,1≤M_P/M_Si is more than or equal to 1 and less than or equal to 3.

The anode active material according to the embodiment of the invention has at least the following beneficial effects:

The negative electrode active material is a silicon/phosphorus/carbon composite material, the phosphorus material has higher theoretical specific capacity and excellent conductivity (electronic conductivity), and is used in an electrochemical energy storage device (such as a secondary battery), a lithium (sodium) phosphorus compound formed by phosphorus in a lithium (sodium) process has positive influence on ion diffusion, and both silicon of the silicon-based material and phosphorus of the phosphorus-based material can provide lithium (sodium) intercalation sites. And the content of the silicon-based material and the phosphorus-based material satisfies the relation: m _P/M_Si is more than or equal to 1 and less than or equal to 3, which is favorable for the formation of P-C bonds between the phosphorus-based material and the carbon material, and the formation of the P-C bonds can further improve the conductivity of the anode active material. Meanwhile, since the contents of the silicon-based material, the phosphorus-based material and the conductivity thereof affect the electron transfer rate, when the relation is satisfied: the content of silicon and phosphorus is not less than 1 and not more than 100 (M _Si*σ_P)/(1000*M_P*σ_Si), so that the capacity requirement can be met, and the electronic conductivity of the anode active material can be improved.

In summary, the negative electrode active material (silicon/phosphorus/carbon composite material) is used for the electrochemical energy storage device, so that the energy density of the electrochemical energy storage device can be ensured, the electron transmission rate can be improved, the electrochemical performance can be improved, the charging temperature rise of the electrochemical energy storage device can be reduced, the polarization of the electrochemical energy storage device can be reduced without damage, the low-temperature discharge and the rate capability of the electrochemical energy storage device can be improved, and the lithium precipitation risk in the rapid charging process can be reduced.

In some embodiments of the invention, 1.ltoreq. (M _Si*σ_P)/(1000*M_P*σ_Si)≤5,2≤M_P/M_Si.ltoreq.3).

Through the embodiment, the obtained anode active material is used in a secondary battery, the low-temperature discharge performance, the charging temperature rise and the cycle performance of the battery are improved well, and the battery performance is better.

In some embodiments of the invention, 1.ltoreq.M _Si*σ_P)/(1000*M_P*σ_Si.ltoreq.4.

In some embodiments of the invention, the carbon spheres have a D ₅₀ of 0.5 to 20 μm, preferably 2 to 6 μm.

By the embodiment, compared with the carbon sphere with the D ₅₀ smaller than 2 mu m, the carbon sphere with the D ₅₀ of 2-6 mu m is more beneficial to the composite effect of the phosphorus-based material and the carbon material in the material preparation process, and the agglomeration phenomenon of the phosphorus-based material and the phosphorus-based material is not easy to cause. Compared with the carbon sphere with the D ₅₀ being larger than 6 mu m, the carbon sphere with the D ₅₀ being 2-6 mu m is less prone to material rupture caused by larger mechanical stress applied to the outside in the subsequent rolling process for preparing the negative electrode plate, and the electrochemical performance of the obtained battery is more stable.

In some embodiments of the invention, the carbon sphere comprises a carbon shell and a porous carbon core disposed within the carbon shell, the silicon-based material being located within the pores of the porous carbon core or/and between the carbon shell and the porous carbon core.

In some embodiments of the invention, the phosphorus-based material is located within the pores of the porous carbon core or/and between the carbon shell and porous carbon core.

In some embodiments of the invention, the carbon shell has a thickness of 10 to 900nm, such as optionally 100 to 300nm.

In some embodiments of the invention, the porous carbon core comprises pores having a pore size of from 5 to 200nm, such as optionally from 50 to 150nm.

In some embodiments of the invention, the carbon shell and the porous carbon core may be connected or partially or fully connected.

In some embodiments of the invention, the silicon-based material comprises silicon. Optionally, the silicon comprises silicon particles.

In some embodiments of the invention, the phosphorus-based material comprises phosphorus. Optionally, the phosphorus comprises phosphorus particles.

In some embodiments of the invention, the phosphorus is black phosphorus.

Through the embodiment, the phosphorus material is black phosphorus, and the black phosphorus has higher specific capacity, good conductivity and interlayer spacing, is favorable for shuttling ions and electrons, and is a fast-charging anode material with great prospect. The black phosphorus with better conductivity is combined with the silicon with high specific capacity, so that the composite material has high capacity and good quick charge capacity. The content proportion and the electronic conductivity of the silicon and phosphorus materials are regulated and controlled to satisfy the relation: in addition, the conductivity of phosphorus is better, lithium ions are preferentially intercalated into the phosphorus material in the lithium intercalation process, the lithium intercalation expansion of the phosphorus material can further limit the lithium intercalation expansion of the silicon material, and the lithium intercalation expansion is further limited by the coating of porous carbon, so that the long-term cycle thickness expansion rate of the battery can be reduced.

In some embodiments of the invention, the M _si% is 1% to 25%, such as optionally 5% to 20%.

By the above embodiment, compared with M _si% being greater than 25%, M _si% is 1% -25% and the resulting negative electrode active material has better conductivity; compared with M _si percent less than 1 percent, M _si percent is 1 to 25 percent, which is more beneficial to the specific capacity exertion of the obtained anode active material.

In some embodiments of the invention, the M _P% to 60%, such as optionally 10% to 50%.

By the above embodiment, the phosphorus-based material has a higher theoretical specific capacity, and its conductivity (electron conductivity) is far superior to that of the silicon material. Compared with M _P percent which is more than 60 percent, M _P percent is more beneficial to P-C bond formation between the phosphorus-based material and the carbon material, thereby further improving the conductivity of the anode active material.

And because of the certain lithiation expansion rate of the phosphorus material and the silicon material, the invention can better promote the conductivity of the material and better restrict the volume expansion effect caused by ion embedding by compounding the silicon-based material with the M _si percent of 1 to 25 percent and the phosphorus-based material with the M _P percent of 5 to 60 percent with the carbon material.

In some embodiments of the invention, the electronic conductivity of the silicon-based material is 10 ^-6～10^-2 S/cm, such as optionally 10 ^-5～10^-3 S/cm.

In some embodiments of the invention, the phosphorus-based material has an electron conductivity of 0.1 to 10S/cm, such as optionally 1 to 3S/cm.

In a second aspect of the present invention, a method for preparing a negative electrode active material is provided, comprising the steps of: and (3) performing heat treatment on the mixture containing the porous carbon material, the phosphorus-based material and the silicon-based material for 0.5-20 hours at 300-800 ℃ in a vacuum environment, and calcining for 0.5-20 hours at 100-800 ℃ in a hydrogen-containing atmosphere to obtain the anode active material.

In some embodiments of the invention, the mass ratio of the porous carbon material, the phosphorus-based material, and the silicon-based material is (25-94): (1-25): (5-60), such as (40-85): (5-20): (10-40), further alternatively (46-82): (6-18): (12-36).

In some embodiments of the invention, the vacuum environment has a vacuum level of < -0.075Mpa.

In some embodiments of the present invention, the mixture is heat-treated at 400 to 600 ℃ for 3 to 5 hours prior to vacuum environment, and then calcined at 300 to 500 ℃ for 3 to 5 hours in an atmosphere containing hydrogen and inert gas, to obtain the negative electrode active material.

In some embodiments of the invention, the volume ratio of hydrogen to inert gas is 1 (15-18).

In some embodiments of the present invention, the preparation method further comprises preparing a porous carbon material, specifically comprising the steps of: mixing MOF material with monomer, initiator and solvent, performing water bath heat treatment, filtering, grinding, calcining at 150-400 ℃ for 0.5-10 h under the mixed atmosphere of oxygen and inert gas, and pickling to obtain the porous carbon material; wherein the monomer comprises at least one of pyrrole or aniline.

Compared with graphite, the conductivity of silicon and phosphorus is slightly poor, and silicon and phosphorus particles are embedded into a porous carbon material, so that on one hand, the expansion of embedded lithium is limited, and on the other hand, the conductivity is improved; MOFs, in turn, have a rich pore structure, a large specific surface area and excellent chemical stability. The monomer and the initiator generate polypyrrole or polyaniline which can enhance the conductivity of the material, and the MOFs organic unit can synthesize the porous carbon material with high surface area under the influence of the original pore skeleton in the carbonization process, so that a storage space can be provided for silicon and phosphorus, and the conductivity of the material is further improved.

Wherein, like polypyrrole or polyaniline is coated on the surface of MOFs material, and then carbonized, similar to a double-carbon layer structure, the expansion of silicon and phosphorus particles can be better limited, and the conductivity is increased. In addition, the spherical structure of polypyrrole is destroyed by carbonization process, which results in rough material surface, increased rough surface area and porosity, and is favorable for infiltration of electrolyte.

In some embodiments of the invention, the initiator comprises at least one of ammonium persulfate, iron trioxide, or ammonium cerium nitrate.

In some embodiments of the invention, the water bath heat treatment is performed at a temperature of 50 to 90 ℃ for a time of 3 to 15 hours.

In some embodiments of the invention, the solvent comprises ethanol.

In some embodiments of the invention, the volume ratio of oxygen to inert gas is (1-10): 1.

In some embodiments of the invention, the mass ratio of the MOF material to the monomer and the initiator is 1 (20-100): 0.1-1.

In some embodiments of the invention, the acid washing is performed with 0.2 to 0.6mol/L hydrochloric acid at 40 to 70 ℃ for 1 to 3 hours, such as optionally: the pickling is carried out by adopting 0.4mol/L hydrochloric acid at 60 ℃ for 2 hours.

In a third aspect of the present invention, there is provided an anode material comprising the anode active material described above.

In some embodiments of the invention, the negative electrode material further comprises graphite. Optionally, the graphite is natural graphite, artificial graphite or the like.

In some embodiments of the invention, the mass ratio of the graphite to the negative electrode active material is (60-99): 2-20.

In some embodiments of the invention, the negative electrode material further comprises a negative electrode conductive agent and a negative electrode binder.

In some embodiments of the invention, the negative electrode conductive agent includes at least one of conductive carbon black (SP) or Carbon Nanotubes (CNT).

In some embodiments of the present invention, the mass ratio of the conductive carbon black to the carbon nanotubes in the negative electrode conductive agent is (5 to 20): 1.

In some embodiments of the invention, the negative electrode binder comprises at least one of SBR or PAALi.

In some embodiments of the present invention, the mass ratio of SBR to PAALi in the negative electrode binder is 1 (1 to 10).

In some embodiments of the present invention, the mass ratio of the anode active material, the anode conductive agent, and the anode binder is (80 to 99.8): 0.1 to 5.

In a fourth aspect of the present invention, a negative electrode is provided, comprising the negative electrode material described above.

In some embodiments of the invention, the anode includes an anode current collector and an anode active layer including the anode material.

In some embodiments of the invention, at least one side of the negative electrode current collector is provided with the negative electrode active layer.

In some embodiments of the invention, the thickness of the anode active layer is 10 to 200 μm.

In some embodiments of the invention, the negative electrode current collector has a thickness of 1 to 20 μm.

In some embodiments of the invention, the negative electrode current collector includes, but is not limited to, copper foil, copper foam, nickel foil, nickel foam, stainless steel foil, tin foil, or composite current collector, or the like.

In some embodiments of the invention, the negative electrode further includes, but is not limited to, a negative electrode film-forming additive or cycle and low temperature improving additive, and the like.

In a fifth aspect of the present invention, an electrochemical energy storage device is provided, comprising the above-described anode.

In some embodiments of the invention, the electrochemical energy storage device is a secondary battery.

In some embodiments of the invention, the secondary battery further comprises a positive electrode and a separator.

In some embodiments of the invention, the positive electrode includes a positive electrode current collector and a positive electrode active layer.

In some embodiments of the present invention, the positive electrode active layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The specific types and compositions of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder are not particularly limited.

In some embodiments of the present invention, the positive electrode active material includes, but is not limited to, lithium cobaltate, ternary material, lithium-rich material, or the like.

In some embodiments of the invention, the positive electrode conductive agent includes at least one of acetylene black or carbon nanotubes.

In some embodiments of the invention, the positive electrode binder comprises polyvinylidene fluoride (PVDF).

In some embodiments of the present invention, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (80 to 99.8): (0.1 to 5).

In some embodiments of the invention, the positive electrode further includes, but is not limited to, positive electrode film forming additives or cycle and low temperature improving additives, and the like.

In some embodiments of the invention, the separator includes, but is not limited to, polyethylene, polypropylene, polyvinylidene fluoride, or the like, and may be a single layer film or a multilayer film.

In some embodiments of the invention, the secondary battery further comprises an electrolyte. Alternatively, the electrolyte includes an electrolyte salt and an organic solvent, wherein the specific kinds and compositions of the electrolyte salt and the organic solvent are not particularly limited.

In a sixth aspect of the present invention, an electric device is provided, where the electrochemical energy storage device is used as a power source for the electric device.

Drawings

The invention is further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a schematic structural view of a negative electrode active material according to example 1 of the present invention.

The attached drawings are identified: 1. silicon particles; 2. phosphorus particles; 3. porous carbon.

Detailed Description

The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.

The experimental procedures, which are not specific to the particular conditions noted in the examples below, are generally performed under conditions conventional in the art or according to manufacturer's recommendations; the raw materials, reagents and the like used, unless otherwise specified, are those commercially available from conventional markets and the like.

Pyrrole, ammonium persulfate, hydrochloric acid were purchased from ala Ding Shenghua technologies, inc, and also from other manufacturers.

Artificial graphite: purchased from Jiangxi ultraviolet (CHINESE) science and technology Co., ltd, D ₅₀:10.5±2.0μm,BET：1.30±0.30m²g^-1,TD:≥0.85g/cm³;

Co-MOF is ZIF-67, the metal source is Co, the ligand is dimethylimidazole, and the material is purchased from Ala Ding Shenghua technology Co; MOF materials produced by other manufacturers are also available.

Example 1

The embodiment discloses a negative electrode active material, which is a silicon/phosphorus/carbon composite material and comprises a carbon shell, a porous carbon sphere positioned on the carbon shell, phosphorus and silicon (wherein the phosphorus is positioned in a pore canal of a porous carbon core or/and between the carbon shell and the porous carbon core; and the silicon is positioned in a pore canal of a porous carbon core or/and between the carbon shell and the porous carbon core), and the schematic diagram can be shown as shown in figure 1. The preparation process of the anode active material comprises the following steps:

Preparation of porous carbon, comprising: 0.05g of Co-MOF (ZIF-67, mn-MOF or Ni-MOF may also be used), 2.5g of pyrrole and 0.025g of ammonium persulfate are dispersed in 15mL of ethanol and water-bath at 70 ℃ for 8h. The mixture was then filtered, dried and ground. The milled material was placed in a tube furnace and calcined at 280 ℃ for 3 hours under a mixed atmosphere of oxygen and argon (volume ratio 3:1). And (3) pickling the sintered powder with 0.4mol/L hydrochloric acid at 60 ℃ for 2 hours, filtering out solid substances, and drying to obtain the porous carbon spheres. The thickness of the shell of the carbon sphere formed by sintering the MOF material is about 150nm, the inner pore diameter of the carbon core is about 80nm, no gap exists between the shell and the inner core of the prepared carbon sphere, and the shell and the inner core of the carbon sphere are integrated. The D ₅₀ of the carbon sphere was 5. Mu.m. In other embodiments of the invention, the thickness of the shell of the carbon sphere can be 100-300 nm, the pore diameter in the carbon core can be 50-150 nm, and the D ₅₀ of the carbon sphere can be 2-6 μm.

(II) preparation of silicon/phosphorus/carbon composite material: mixing porous carbon with a silicon material (silicon) and a phosphorus material (black phosphorus) according to a mass ratio of 12.7:1:3, placing the mixture into a tube furnace, preserving heat for 3h (3-5 h can be carried out) under the condition that the vacuum degree is less than-0.075 Mpa at 500 ℃, and calcining for 3h (3-5 h can be carried out) under the mixed atmosphere of hydrogen and argon (volume ratio of 1:15) at 300 ℃ (300-500 ℃), thus obtaining the silicon/phosphorus/carbon composite material. Wherein, the volume ratio of the hydrogen to the argon is 1:15-18.

The electronic conductivities of the silicon material and the phosphorus material adopted are respectively 4.23x10 ^-4 S/cm and 1.76S/cm.

The embodiment also discloses a negative electrode material, which comprises the negative electrode active material prepared by the embodiment, artificial graphite, a negative electrode conductive agent and a negative electrode binder. Wherein the negative electrode conductive agent comprises a mixture of SP and CNT, and the mass ratio of SP to CNT is 0.45:0.05. The binder is a mixture of SBR and PAALi, and the mass ratio of SBR to PAALi is 0.5:1.8.

The embodiment also discloses a negative electrode plate, which comprises the following preparation steps:

Mixing SP and CNT in a mass ratio of 0.45:0.05 to obtain a negative electrode conductive agent; mixing SBR and PAALi in a mass ratio of 0.5:1.8 to obtain a negative electrode binder;

The negative electrode active material (containing a negative electrode active material and artificial graphite in a mass ratio of 10:90), a negative electrode conductive agent and a negative electrode binder are mixed according to 97.7:1.1:1.2, preparing a negative electrode active material slurry, uniformly coating the slurry on a negative electrode current collector (copper foil), and then carrying out cold pressing and slitting to obtain a negative electrode plate. Wherein the thickness of the negative electrode plate is 90 mu m, and the thickness of the negative electrode current collector is 5 mu m.

The embodiment also discloses a lithium ion battery, which comprises the negative electrode plate prepared by the embodiment. The lithium ion battery also comprises a positive pole piece, an isolating film and electrolyte. Wherein:

Preparing a positive electrode plate: positive electrode active material LiCoO ₂, conductive agent acetylene black, conductive carbon nano tube and binder polyvinylidene fluoride (PVDF) according to the weight ratio of 97.6:0.5:0.6:1.3 fully and uniformly dispersing the mixture in an N-methyl pyrrolidone solvent system, coating the mixture on an anode current collector (aluminum foil), and then carrying out cold pressing and slitting to obtain an anode plate. Wherein the thickness of the positive electrode plate is 70 mu m, and the thickness of the positive electrode current collector is 8 mu m.

Isolation film: and coating ceramic mixed materials on two side surfaces of the PE layer to serve as a separation film, wherein the ceramic mixed materials comprise PVDF and alumina. The thickness of the separator was 6 μm and the thickness of the PE layer was 4. Mu.m. Purchased from Huizhou lithium-Weber electronic technologies Co., ltd (YC-SCD-6814F 4-004);

Electrolyte solution: ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC) and Propyl Propionate (PP) are mixed according to the volume ratio of 1.2:1:4:4: the mixture was then dissolved in a mixed organic solvent at a ratio of 1mol/L to prepare an electrolyte.

Full cell preparation: and winding or laminating the negative electrode plate, the isolating film and the positive electrode plate to manufacture a bare cell, and then packaging and injecting electrolyte to manufacture the finished lithium ion battery.

The embodiment also discloses a sodium ion battery, which comprises the negative electrode plate prepared by the embodiment.

Examples 2 to 8 and comparative examples 1 to 7

Examples 2 to 8 and comparative examples 1 to 7 disclose a series of anode active materials, which are different from example 1 in that: the electronic conductivities of the silicon material and the phosphorus material adopted are different (the lattice defect and impurity concentration of the silicon material can influence the conductivity of the material, the purity and nanocrystallization of the phosphorus material can influence the conductivity of the material), the mass fractions of the silicon material and the phosphorus material in the anode active material are different, and whether pyrrole and ammonium persulfate are added in the preparation process; specific information is shown in Table 1 below, wherein the electron conductivity is measured using a four probe measurement method.

Wherein the silicon material is available from Lanxi De energy materials Co., ltd:

Examples 1 to 5/8, comparative examples 1/3/5 to 7: YP-APS-0090-0000;

Examples 6 to 7: YP-APS-0083-0000; comparative example 4: YP-APS-0121-0000;

phosphorus materials were purchased from solid lithium new energy technologies limited:

Examples 1 to 6/8, comparative examples 2 to 5/7: YP-APG-0058-0000;

Example 7: YP-APG-0014-0000; comparative example 6: YP-APG-0021-0000;

Examples 2 to 8 and comparative examples 1 to 7 also disclose a series of negative electrode materials differing from example 1 only in that: the negative electrode active materials corresponding to examples 2 to 8 and comparative examples 1 to 7 were used, respectively.

Examples 2 to 8 and comparative examples 1 to 7 also disclose a series of negative electrode sheets differing from example 1 only in that: the negative electrode materials corresponding to examples 2 to 8 and comparative examples 1 to 7 were used, respectively.

Examples 2 to 8 and comparative examples 1 to 7 also disclose a series of lithium ion batteries, which differ from example 1 only in that: the negative electrode sheets corresponding to examples 2 to 8 and comparative examples 1 to 7 were used, respectively.

Examples 2 to 8 and comparative examples 1 to 7 also disclose a series of sodium ion batteries differing from example 1 only in that: the negative electrode sheets corresponding to examples 2 to 8 and comparative examples 1 to 7 were used, respectively.

TABLE 1

Test examples

The lithium ion batteries prepared in the examples and comparative examples were subjected to performance test in this test example, and specifically include:

low temperature performance test: in the environment of 25 ℃, the charging test is carried out according to the following method, charging system: 0.5C CC to 4.5V,CV to 0.02C; -10 ℃ environment, carrying out discharge test according to the following method, wherein the discharge mode is as follows: 0.2C DC to 3.2V.

And (3) multiplying power performance test: in the environment of 25 ℃, the charging test is carried out according to the following method, charging system: 0.5C CC to 4.5V,CV to 0.02C; discharge system: 1.5C DC to 3.0V;

Temperature rise test: in the environment of 25 ℃, the charging test is carried out according to the following method, and the charging standard ：2.8C CC to 4.27V,2.5CCC to 4.35V,CV to 1.8C,1.8C CC to 4.4V,CV to 1.5C,1.5C CC to 4.5V,CV to 1.2C,1.2CCC to 4.55V,CV to 0.26C; is the discharging standard: 0.2C DC to 3.0V. A temperature rise tester was used to monitor the temperature at the center of the battery surface.

And (3) cyclic test: in a 45 ℃ environment, a charging test is carried out according to the following method, and a charging system ：2.8C CC to 4.27V,2.5CCC to 4.35V,CV to 1.8C,1.8C CC to 4.4V,CV to 1.5C,1.5C CC to 4.5V,CV to 1.2C,1.2CCC to 4.55V,CV to 0.26C; is a discharging system: 0.7C DC to 3.2V.

300 Week capacity retention = 300 weeks full capacity/initial full capacity;

300 weeks thickness expansion= (300 weeks full electrical thickness-initial half electrical thickness)/initial half electrical thickness; the cell thickness was measured using 600 PPG.

The test results are detailed in table 2 below:

TABLE 2

As can be seen from examples 1 to 8 and comparative examples 1 to 7, the anode material of the present invention clearly has superior electrochemical properties; according to low-temperature discharge and rate performance, the electrochemical energy storage device has obviously improved conductivity and still has good performance under the condition of low temperature or high current density. From the result of temperature rise, the electrode polarization of the electrochemical energy storage device is reduced, and the temperature rise is reduced, thereby being beneficial to improving the performance of the electrochemical energy storage device in a high-temperature environment.

The term "about" as used herein, unless otherwise specified, means that the tolerance is within + -2%, for example, about 100 is actually 100 + -2%. Times.100. The "normal temperature" and "room temperature" of the present invention are about 20 to 30℃unless otherwise specified.

Unless otherwise specified, the term "between … …" in the present invention includes the present number, e.g. "between 2 and 3" includes the end values 2 and 3.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.

Claims

1. The negative electrode active material is characterized by comprising carbon spheres, wherein the carbon spheres comprise a silicon-based material and a phosphorus-based material, the mass fraction of the silicon-based material in the carbon spheres is M _si%, the mass fraction of the phosphorus-based material in the carbon spheres is M _P%, the electronic conductivity of the silicon-based material is sigma _si S/cm, and the electronic conductivity of the phosphorus-based material is sigma _P S/cm,M_si、M_P、σ_si and sigma _P, and the requirements are met: m _Si*σ_P)/(1000*M_P*σ_Si)≤100,1≤M_P/M_Si is more than or equal to 1 and less than or equal to 3.

2. The anode active material according to claim 1, wherein 1.ltoreq.m _Si*σ_P)/(1000*M_P*σ_Si)≤5,2≤M_P/M_Si.ltoreq.3.

3. The anode active material according to claim 1, wherein D ₅₀ of the carbon sphere is 0.5 to 20 μm; and/or the carbon sphere comprises a carbon shell and a porous carbon core arranged in the carbon shell, wherein the silicon-based material is positioned in pore channels of the porous carbon core or/and between the carbon shell and the porous carbon core.

4. The anode active material according to claim 1, wherein the silicon-based material comprises silicon; and/or, the phosphorus-based material comprises phosphorus; and/or, the M _si% is 1% -25%; and/or, the M _P% to 60%; and/or the electronic conductivity of the silicon-based material is 10 ^-6～10^-2 S/cm; and/or the electron conductivity of the phosphorus-based material is 0.1-10S/cm.

5. A method for preparing a negative electrode active material, comprising the steps of: and (3) performing heat treatment on the mixture containing the porous carbon material, the phosphorus-based material and the silicon-based material for 0.5-20 hours at 300-800 ℃ in a vacuum environment, and calcining for 0.5-20 hours at 100-800 ℃ in a hydrogen-containing atmosphere to obtain the anode active material.

6. A negative electrode material comprising the negative electrode active material according to any one of claims 1 to 4 or the negative electrode active material produced by the method according to claim 5.

7. The anode material according to claim 6, wherein the anode material further comprises graphite;

preferably, the mass ratio of the graphite to the negative electrode active material is (60-99): 2-20.

8. A negative electrode comprising the negative electrode material according to any one of claims 6 to 7.

9. An electrochemical energy storage device comprising the negative electrode of claim 8.

10. An electrical consumer, wherein the electrochemical energy storage device of claim 9 is used as a power source for the electrical consumer.