CN115377346A - Negative pole piece and secondary battery - Google Patents

Negative pole piece and secondary battery Download PDF

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Publication number
CN115377346A
CN115377346A CN202211170664.3A CN202211170664A CN115377346A CN 115377346 A CN115377346 A CN 115377346A CN 202211170664 A CN202211170664 A CN 202211170664A CN 115377346 A CN115377346 A CN 115377346A
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active layer
negative pole
surface density
coating surface
pole piece
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Inventor
刘强
高鹏
蔡芬敏
赵宗奎
韩威风
郭炜渊
黄俊涛
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Huizhou Liwinon Energy Technology Co Ltd
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Huizhou Liwinon Energy Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a negative pole piece and a secondary battery, wherein the negative pole piece comprises a negative pole current collector, a first active layer and a second active layer, the single-side coating surface density of the negative pole piece is A, the percentage of the first-section constant-current constant-voltage charging capacity in the total capacity is a, the single-side coating surface density of the first active layer is B, and the single-side coating surface density of the second active layer is C, so that the single-side coating surface density of the first active layer and the single-side coating surface density of the second active layer satisfy the following relation: b = a%, C = a-B. The negative pole piece is provided with the two coating layers, the surface densities of the two coating layers are set according to the charging mode, the first active layer close to the negative current collector can be rapidly embedded with lithium, so that the charging rate is improved, the second active layer is far away from the negative current collector, the impact of large current is reduced, and meanwhile, the two coating layers are matched for use, so that the cycle capacity retention rate and the thickness expansion rate of the pole piece are improved.

Description

Negative pole piece and secondary battery
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a negative pole piece and a secondary battery.
Background
The storage battery is widely used as an energy storage element of the electric automobile. Compared with traditional lead-acid and cadmium-nickel batteries, the lithium ion battery has the characteristics of high specific energy, long service life, low pollution, high working voltage and the like, and is widely applied. The lithium ion battery is a rocking chair battery which adopts lithium-intercalated compounds with low lithium intercalation potential, such as C and Si elements of graphite, hard carbon, silicon oxide and the like as a negative electrode, and the thickness of the lithium ion battery is correspondingly increased along with the increase of the cycle times in the use process; along with the higher requirement of people on the charging time, the charging multiplying power of the lithium ion battery is continuously increased, the charging mode is continuously iterated, the traditional one-section constant-current constant-voltage charging is upgraded into the multi-section constant-current constant-voltage charging, and the charging rate is greatly increased. The charging rate is increased, the larger the impact on the negative electrode material in the charging process is, the larger the damage is, the cycle capacity retention rate is reduced, the thickness expansion is increased, and the method is particularly obvious for a battery taking silicon carbon as the negative electrode.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the negative pole piece is provided with two layers of coatings, the surface density of the two layers of coatings is designed according to a charging system, so that the negative pole piece can realize quick charge and discharge, and high cycle capacity retention rate and thickness expansion rate are kept.
In order to achieve the purpose, the invention adopts the following technical scheme:
a negative pole piece comprises a negative pole current collector, a first active layer arranged on at least one surface of the negative pole current collector and a second active layer arranged on one side surface of the first active layer far away from the negative pole current collector, wherein the single-side coating surface density of the negative pole piece is A, the percentage of the first-section constant-current constant-pressure charging capacity in the total capacity is a, the single-side coating surface density of the first active layer is B, and the single-side coating surface density of the second active layer is C, so that the single-side coating surface density of the first active layer and the single-side coating surface density of the second active layer meet the following relation: b = a%, C = a-B.
Preferably, the first active layer comprises one or more of artificial graphite, conductive carbon black, coke, carbon fiber, carbon nanotube.
Preferably, the second active layer comprises a carbon material and a silicon material, the carbon material comprises one or more of graphite, conductive carbon black, coke, carbon fiber and carbon nanotube, and the silicon material comprises one or more of silicon monoxide and silicon oxide.
Preferably, the mass ratio of the carbon material to the silicon material in the second active layer is 1-3.
Preferably, the value range of the single-side coating surface density A of the negative pole piece is 0.002g/cm 2 ～0.12g/cm 2 。
Preferably, the value range of the percentage of the first-stage constant-current and constant-voltage charging capacity to the total capacity is a: 30 to 80 percent
Preferably, the single-side coating surface density of the first active layer is B, and the value range is 0.002g/cm 2 ～0.08g/cm 2 。
Preferably, the single-side coating surface density of the second active layer is C, and the value range of the single-side coating surface density is 0.002g/cm 2 ～0.08g/cm 2 。
Preferably, the thickness ratio of the first active layer to the second active layer is 1 to 6.
The second purpose of the invention is: in view of the disadvantages of the prior art, a secondary battery is provided, which can realize rapid charge and discharge and has good capacity retention rate and thickness expansion rate.
In order to achieve the purpose, the invention adopts the following technical scheme:
a secondary battery comprises the negative pole piece.
Compared with the prior art, the invention has the beneficial effects that: the negative pole piece is provided with the two coating layers, the surface densities of the two coating layers are set according to the charging mode, the first active layer close to the negative current collector can be rapidly embedded with lithium, so that the charging rate is improved, the second active layer is far away from the negative current collector, the impact of large current is reduced, and meanwhile, the two coating layers are matched for use, so that the circulating capacity retention rate and the thickness expansion rate of the pole piece are improved, and the energy density is improved.
Drawings
Fig. 1 is a schematic structural view of a negative electrode tab of the present invention.
Fig. 2 is a graph comparing the capacity retention rates of example 1 of the present invention and comparative example 1.
Fig. 3 is a graph comparing thickness expansion ratios of example 1 of the present invention and comparative example 1.
Wherein: 1. a negative current collector; 2. a first active layer; 3. a second active layer.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.
A negative pole piece comprises a negative pole current collector 1, a first active layer 2 arranged on at least one surface of the negative pole current collector 1 and a second active layer 3 arranged on one side surface of the first active layer 2 far away from the negative pole current collector 1, wherein the single-side coating surface density of the negative pole piece is A, the percentage of the first section constant-current constant-pressure charging capacity in the total capacity is a, the single-side coating surface density of the first active layer 2 is B, and the single-side coating surface density of the second active layer 3 is C, so that the single-side coating surface density of the first active layer 2 and the single-side coating surface density of the second active layer 3 meet the following relation: b = a%, C = a-B.
The negative pole piece is provided with the two coating layers, the surface densities of the two coating layers are set according to the charging system, so that the first active layer 2 close to the negative current collector 1 can realize quick lithium embedding, the charging rate is improved, the second active layer 3 is far away from the negative current collector 1, the impact of large current is reduced, and meanwhile, the two coating layers are matched for use, so that the circulating capacity retention rate and the thickness expansion rate of the pole piece are improved, and the energy density is improved.
The first section of the multi-section constant-current constant-voltage charging system is usually large-current constant-voltage charging, lithium intercalation of the negative electrode is driven by external force, and the lithium intercalation preferentially occurs on the copper foil closer to the current collector 1 of the negative electrode. According to the invention, the coating surface densities of the first active layer 2 and the second active layer 3 are calculated by matching with a charging system through a double-layer coating technology, and the silicon-carbon composite material is embedded with excessive lithium at the bottom layer and is expanded excessively to cause chapping and deactivation of active substances, so that the circulating capacity retention rate of a silicon-carbon composite battery is improved, and the thickness expansion rate is reduced. Through the accurate design, the proportion of the silicon composite material in the negative active material can be improved, and the energy density of the battery is further improved.
In some embodiments, the first active layer 2 comprises one or more of artificial graphite, conductive carbon black, coke, carbon fibers, carbon nanotubes. The first active layer 2 includes a carbon active material, a conductive agent, and a binder, and the carbon active material is mainly artificial graphite, conductive carbon black, coke, carbon fiber, carbon nanotube, or the like, and can achieve rapid lithium intercalation with the negative current collector 1 without causing large expansion.
In some embodiments, the second active layer 3 includes a carbon material including one or more of graphite, conductive carbon black, coke, carbon fiber, carbon nanotube, and a silicon material including one or more of silica, silicon oxide. The second active layer 3 is mainly added with silicon materials relative to the first active layer 2, so that the gram capacity of the negative plate is improved, and the first active layer 2 is arranged between the second active layer 3 and the negative current collector 1, so that the problem that the silicon materials and the silicon-carbon composite materials in the second active layer 3 embed excessive lithium at the bottom layer to cause the inactivation of volume expansion active substances is avoided. The first active layer 2 and the second active layer 3 are used together, so that the circulating capacity of the silicon-carbon composite material battery is improved, the thickness expansion rate is reduced, and the energy density of the battery is improved.
In some embodiments, the mass ratio of the carbon material to the silicon material in the second active layer 3 is 1 to 3. The carbon material and the silicon material in the second active layer 3 are set to have a certain mass ratio, so that the pole piece has a certain charge-discharge rate performance and a certain gram capacity. Preferably, the mass ratio of the carbon material to the silicon material is 1: 3. 1. Preferably, the silicon material is arranged to account for 3% -15% of the negative electrode.
In some embodiments, the single-side coating surface density A of the negative pole piece ranges from 0.002g/cm 2 ～0.12g/cm 2 . Preferably, the single-side coating surface density A of the negative pole piece is 0.002g/cm 2 、0.05g/cm 2 、0.06g/cm 2 、0.07g/cm 2 、0.08g/cm 2 、0.09g/cm 2 、0.1g/cm 2 、0.11g/cm 2 、0.12g/cm 2 。
In some embodiments, the percentage of the first-stage constant-current and constant-voltage charging capacity to the total capacity is a, and the value range is as follows: 30 to 80 percent. Preferably, the percentage of the constant-current constant-voltage charging capacity of the first section to the total capacity is 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%.
In some embodiments, the single-coated surface density B of the first active layer 2 is in a range of 0.002g/cm 2 ～0.08g/cm 2 . Preferably, the single-side coating surface density B of the first active layer 2 is in a range of 0.002g/cm 2 、0.008g/cm 2 、0.02g/cm 2 、0.03g/cm 2 、0.04g/cm 2 、0.05g/cm 2 、0.06g/cm 2 、0.07g/cm 2 、0.08g/cm 2 。
In some embodiments, the single-coated-surface density C of the second active layer 3 is in a range of 0.02g/cm 2 ～0.08g/cm 2 . Preferably, the single-side coating surface density of the second active layer 3 is 0.002g/cm 2 、0.008g/cm 2 、0.02g/cm 2 、0.03g/cm 2 、0.04g/cm 2 、0.05g/cm 2 、0.06g/cm 2 、0.07g/cm 2 、0.08g/cm 2 。
In some embodiments, the ratio of the thickness of the first active layer 2 to the second active layer 3 is 1 to 6. Preferably, the thickness ratio of the first active layer 2 to the second active layer 3 is 1.
A secondary battery capable of realizing rapid charge and discharge and having good capacity retention rate and thickness expansion rate.
A secondary battery comprises the negative pole piece.
The secondary battery can be a lithium ion battery, a sodium ion battery, a potassium ion battery, an aluminum ion battery, a magnesium ion battery, a calcium ion battery, and the following secondary batteries are exemplified by the lithium ion battery. Specifically, lithium ion battery includes positive plate, barrier film, negative pole piece, electrolyte and casing, the barrier film separates positive plate and negative pole piece, the casing is used for with encapsulation is installed to positive plate, negative pole piece, barrier film and electrolyte. The negative plate is the negative plate.
Positive electrode
The positive plate comprises a positive current collector and a positive active material layer arranged on at least one surface of the positive current collector, the positive active material layer comprises a positive active material, and the positive active material can be a chemical formula including but not limited to Li a Ni x Co y M z O 2-b N b (wherein 0.95. Ltoreq. A.ltoreq.1.2>0,y is more than or equal to 0, z is more than or equal to 0, and x + y + z =1,0 is more than or equal to b is less than or equal to 1, M is selected from one or more of Mn and Al, N is selected from one or more of F, P and S), the positive active material can also be selected from one or more of LiCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiCoFSO 4 、CuS 2 、FeS 2 、MoS 2 、NiS、TiS 2 And the like. The positive electrode active material may be further modified, and the method of modifying the positive electrode active material is known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, and the like, and the material used in the modification may be one or a combination of more of Al, B, P, zr, si, ti, ge, sn, mg, ce, W, and the like. And the positive electrode current collector is generally a structure or a part for collecting current, and the positive electrode current collector may be any material suitable for use as a positive electrode current collector of a lithium ion battery in the art, for example, the positive electrode current collector may include, but is not limited to, a metal foil and the like, and more specifically, may include, but is not limited to, an aluminum foil and the like.
Negative electrode
The negative plate comprises a negative current collector 1 and a negative active material layer arranged on the surface of the negative current collector 1, wherein the negative active material layer comprises a negative active material, and the negative active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming an alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. The negative electrode current collector 1 is generally a structure or a part for collecting current, and the negative electrode current collector 1 may be any material suitable for use as a negative electrode current collector 1 of a lithium ion battery in the art, for example, the negative electrode current collector 1 may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.
Electrolyte solution
The lithium ion battery also comprises electrolyte, and the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte 6 And &Or LiBOB; or LiBF used in low-temperature electrolyte 4 、LiBOB、LiPF 6 At least one of; or LiBF used in anti-overcharge electrolyte 4 、LiBOB、LiPF 6 At least one of, liTFSI; may also be LiClO 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of (a). And the organic solvent may be a cyclic carbonate including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, control of H in the electrolyte 2 At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.
And the separator may be various materials suitable for lithium ion battery separators in the art, and for example, may be one or a combination of more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like, including but not limited thereto.
Preferably, the material of the shell is one of stainless steel and an aluminum plastic film. More preferably, the housing is an aluminum plastic film.
Example 1
According to a multi-section constant-current constant-voltage charging system, the battery with the same system is fully charged, the full charge capacity is 5000mAh, and the first section constant-current constant-voltage charging capacity is 2000mAh and accounts for 40% of the total charge capacity. The total anode single-side coating surface density is designed according to the user requirements and is A =0.085g/cm 2 Wherein the silicon composite material accounts for 5%; the single-side coating surface density of the first layer of pure graphite coating is B =0.085g/cm 2 *40％＝0.034g/cm 2 And the single-sided coating surface density of the second layer C = A-B =0.051g/cm 2 The silicon composite material accounts for (0.085 x 5%)/0.051= 8.33% in the B, and the content of active substances of the silicon-carbon composite material in the negative electrode plate is controlled to be kept unchanged by 5%.
A preparation method of a negative pole piece for improving the cycle performance of a lithium ion soft package silicon-carbon battery comprises the following steps:
step 1: the density of the coating surface on the two surfaces of the negative current collector 1 is 0.034g/cm 2 The pure graphite layer (i.e. the first active layer 2) contains 96% of active substances, 2% of thickening agent CMC-Na (sodium carboxymethylcellulose) and 2% of adhesive SBR (styrene butadiene rubber latex).
Step 2: the first active layer 2 was coated with an areal density of 0.051g/cm 2 Drying the silicon-carbon composite material to form a second active layer 3 to prepare a negative pole piece, wherein the silicon composite active material accounts for 8.33 percent of the active substance; in the second layer of active material, 96% of active material, 2% of thickening agent CMC-Na (sodium carboxymethylcellulose), and 2% of binder SBR (styrene butadiene latex), wherein the mass ratio of the carbon material to the silicon material is 2.
And step 3: the pole piece is rolled to a thickness of 110 μm.
Preparing a positive plate:
lithium cobaltate, conductive agent superconducting carbon (Super-P) and binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97:1.5:1.5, uniformly mixing to prepare lithium ion battery anode slurry with certain viscosity, coating the slurry on a current collector aluminum foil, drying at 85 ℃, and then carrying out cold pressing; then trimming, cutting into pieces, slitting, drying for 4 hours at 110 ℃ under the vacuum condition after slitting, and welding the tabs to prepare the lithium ion battery positive plate.
Preparing an electrolyte:
mixing lithium hexafluorophosphate (LiPF) 6 ) Dissolving the mixture in a mixed solvent composed of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) (the mass ratio of the three is 1:2: 1) To obtain the electrolyte with the concentration of 1 mol/L.
The release film is selected from a polypropylene based film 8 μm thick.
Preparing a lithium ion battery:
winding the positive plate, the isolating film and the negative plate into a battery cell, wherein the isolating film is positioned between the positive plate and the negative plate, the positive electrode is led out by spot welding of an aluminum tab, and the negative electrode is led out by spot welding of a nickel tab; and then placing the battery core in an aluminum-plastic film shell, injecting the electrolyte, and carrying out processes of packaging, formation and capacity to prepare the lithium ion battery.
Example 2
The difference from example 1 is that: the mass ratio of the carbon material to the silicon material in the second active layer 3 is 1.
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
The difference from example 1 is that: the mass ratio of the carbon material to the silicon material in the second active layer 3 is 1.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
The difference from example 1 is that: the mass ratio of the carbon material to the silicon material in the second active layer 3 is 2.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
The difference from example 1 is that: the mass ratio of the carbon material to the silicon material in the second active layer 3 is 3.
The rest is the same as embodiment 1, and the description is omitted here.
Example 6
The difference from example 1 is that: the density A of the single-side coating surface of the negative pole piece is 0.09g/cm 2 The percentage a of the constant-current constant-pressure charging capacity of the first section to the total capacity is 40%, and the single-side coating surface density B of the first active layer 2 is 0.036g/cm 2 The density C of the one-side coated surface of the second active layer 3 was 0.064g/cm 2 。
The rest is the same as embodiment 1, and the description is omitted here.
Example 7
The difference from example 1 is that: the density A of the single-side coating surface of the negative pole piece is 0.095g/cm 2 The percentage a of the constant-current constant-pressure charging capacity of the first section accounting for the total capacity is 40%, and the single-side coating surface density B of the first active layer 2 is 0.038g/cm 2 The single-side coating surface density C of the second active layer 3 was 0.057g/cm 2 。
The rest is the same as embodiment 1, and the description is omitted here.
Example 8
The difference from example 1 is that: the density A of the single-side coating surface of the negative pole piece is 0.098g/cm 2 The percentage a of the constant-current constant-pressure charging capacity of the first section to the total capacity is 40%, and the single-side coating surface density B of the first active layer 2 is 0.0392g/cm 2 The single-side coating surface density C of the second active layer 3 was 0.0588g/cm 2 。
The rest is the same as embodiment 1, and the description is omitted here.
Example 9
The difference from example 1 is that: the density A of the single-side coating surface of the negative pole piece is 0.1g/cm 2 The percentage a of the constant-current constant-pressure charging capacity of the first section to the total capacity is 40%, and the single-side coating surface density B of the first active layer 2 is 0.04g/cm 2 The one-side coating areal density C of the second active layer 3 was 0.06g/cm 2 。
The rest is the same as embodiment 1, and the description is omitted here.
Example 10
The difference from example 1 is that: the density A of the single-side coating surface of the negative pole piece is 0.07g/cm 2 The percentage a of the constant-current constant-pressure charging capacity of the first section to the total capacity is 40%, and the single-side coating surface density B of the first active layer 2 is 0.028g/cm 2 The single-side coating surface density C of the second active layer 3 was 0.042g/cm 2 。
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 1
Step 1: the density of the coating surface on the two surfaces of the negative current collector 1 is 0.085g/cm 2 The silicon-carbon composite layer of (2), wherein the silicon composite material accounts for 5% of the active material; in the coating, the active substance accounts for 96%, the thickening agent CMC-Na (sodium carboxymethylcellulose) accounts for 2%, and the adhesive SBR (styrene butadiene latex) accounts for 2%.
Step 2: the pole piece is rolled to a thickness of 110 μm.
The lithium ion soft package silicon carbon battery cathode pole piece which is not matched with a charging mode is obtained by adopting the preparation method. A lithium ion soft package silicon carbon battery is obtained by cutting and manufacturing a negative pole piece, winding the manufactured negative pole piece and a positive pole piece to obtain a roll core, and packaging, baking, injecting liquid, forming, secondary sealing and sorting the roll.
Comparative example 2
The difference from example 1 is that: the density A of the single-side coating surface of the negative pole piece is 0.15g/cm 2 The percentage a of the constant-current constant-pressure charging capacity of the first section to the total capacity is 40%, and the single-side coating surface density B of the first active layer 2 is 0.06g/cm 2 The second active layer 3 had a single-coated-surface density C of 0.09g/cm 2 Time of flight
The rest is the same as embodiment 1, and the description is omitted here.
And (4) performance testing: the secondary batteries of examples 1 to 10 and the battery of comparative example 1 were subjected to performance tests, and the test results are reported in tables 1 and 2.
TABLE 1
Figure BDA0003861569180000101
Figure BDA0003861569180000111
TABLE 2
Number of weeks 100 200 300 400 500 600 700 800
Example 1 4.1％ 5.1％ 5.8％ 6.2％ 6.8％ 7.1％ 7.5％ 7.7％
Example 2 4.3％ 5.3％ 5.9％ 6.4％ 6.9％ 7.2％ 7.6％ 7.9％
Example 3 4.2％ 5.4％ 6.1％ 6.3％ 7.0％ 7.3％ 7.7％ 7.8％
Example 4 4.4％ 5.3％ 5.9％ 6.4％ 6.9％ 7.3％ 7.6％ 7.9％
Example 5 4.3％ 5.2％ 5.9％ 6.5％ 6.9％ 7.4％ 7.6％ 7.9％
Example 6 4.3％ 5.3％ 5.9％ 6.4％ 7.0％ 7.3％ 7.6％ 8.2％
Example 7 4.4％ 5.4％ 5.9％ 6.3％ 6.9％ 7.2％ 7.6％ 7.8％
Example 8 4.3％ 5.2％ 5.9％ 6.4％ 6.9％ 7.3％ 7.7％ 7.9％
Example 9 4.4％ 5.3％ 5.9％ 6.5％ 6.9％ 7.3％ 7.8％ 8.0％
Example 10 4.3％ 5.3％ 6.1％ 6.3％ 6.9％ 7.3％ 7.7％ 7.9％
Comparative example 1 5.7％ 7.2％ 8.3％ 9.2％ 10.4％ 11.8％ 13.2％ 14.6％
Comparative example 2 5.8％ 7.1％ 9.6％ 10.2％ 11.8％ 12.6％ 14.7％ 16.5％
As can be seen from table 1, the secondary battery of the present invention has better performance than the battery of comparative example 1, the capacity retention rate after 800 times of charge and discharge is more than 88.3%, and the thickness expansion rate after 800 times of charge and discharge is less than 8.2%. As can be seen from comparison of examples 1 to 5, when the mass ratio of the carbon material to the silicon material in the second active layer 3 was set to 2. From comparison of examples 1, 6 to 10, when the single-side coating surface density A of the negative electrode sheet is set to be 0.085g/cm 2 The percentage a of the constant-current constant-pressure charging capacity of the first section accounting for the total capacity is 40%, and the single-side coating surface density B of the first active layer 2 is 0.034g/cm 2 The single-side coating surface density C of the second active layer 3 was 0.051g/cm 2 The prepared secondary battery has better performance. With reference to FIGS. 1 and 2, it can be seen from a comparison of example 1 and comparative example 1 that only one layer is provided when an active coating is providedIn the process, the active coating is easy to expand in multiple cycles, so that the volume change is large and reaches 14.6%, the pressure between the electrode plates is increased due to the volume expansion, the capacity retention rate is further influenced, the capacity retention rate is low and is only 82%, as can be seen from fig. 1 and fig. 2, compared with comparative example 1, the capacity retention rate of the invention is increased by 8%, the thickness expansion rate is reduced by 47.2%, and the performance is obviously improved.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious modifications, substitutions or alterations based on the present invention will fall within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. A negative pole piece is characterized by comprising a negative pole current collector, a first active layer arranged on at least one surface of the negative pole current collector and a second active layer arranged on one side surface of the first active layer far away from the negative pole current collector, wherein the single-side coating surface density of the negative pole piece is A, the percentage of the first-section constant-current constant-pressure charging capacity to the total capacity is a, the single-side coating surface density of the first active layer is B, and the single-side coating surface density of the second active layer is C, so that the single-side coating surface density of the first active layer and the single-side coating surface density of the second active layer meet the following relation: b = a%, C = a-B.
2. The negative electrode sheet of claim 1, wherein the first active layer comprises one or more of artificial graphite, conductive carbon black, coke, carbon fiber, carbon nanotubes.
3. The negative electrode plate as claimed in claim 1 or 2, wherein the second active layer comprises a carbon material and a silicon material, the carbon material comprises one or more of graphite, conductive carbon black, coke, carbon fiber, carbon nanotube, and the silicon material comprises one or more of silica and silica.
4. The negative electrode plate as claimed in claim 3, wherein the mass ratio of the carbon material to the silicon material in the second active layer is 1-3.
5. The negative pole piece of claim 1, wherein the single-coated surface density A of the negative pole piece is in a range of 0.002g/cm 2 ～0.12g/cm 2 。
6. The negative electrode plate of claim 1, wherein the first section of constant-current and constant-voltage charging capacity accounts for a total capacity, and the value range of a is as follows: 30 to 80 percent.
7. The negative electrode sheet of claim 1, wherein the single-side coating surface density of the first active layer is B, and the value range is 0.002g/cm 2 ～0.08g/cm 2 。
8. The negative electrode sheet of claim 1, wherein the single-side coating surface density of the second active layer is C, and the value range is 0.002g/cm 2 ～0.08g/cm 2 。
9. The negative electrode plate as claimed in claim 1, wherein the thickness ratio of the first active layer to the second active layer is 1-6.
10. A secondary battery comprising the negative electrode sheet according to any one of claims 1 to 9.
CN202211170664.3A 2022-09-23 2022-09-23 Negative pole piece and secondary battery Pending CN115377346A (en)

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