CN108808006B - Negative pole piece and battery - Google Patents

Negative pole piece and battery Download PDF

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Publication number
CN108808006B
CN108808006B CN201810397553.3A CN201810397553A CN108808006B CN 108808006 B CN108808006 B CN 108808006B CN 201810397553 A CN201810397553 A CN 201810397553A CN 108808006 B CN108808006 B CN 108808006B
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battery
active material
negative electrode
negative
electrode active
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CN108808006A (en
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康蒙
彭天权
申玉良
王家政
何立兵
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • 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

Abstract

The invention provides a negative pole piece and a battery, wherein the negative pole piece comprises a negative current collector and a negative diaphragm which is arranged on at least one surface of the negative current collector and comprises a negative active material. The powder compacted density P of the negative active material under 3000Kg of pressure3kAnd average particle diameter D of negative electrode active materialvThe relationship between 50 satisfies: 0.15 is less than or equal to 1/Dv50+0.2/P3kLess than or equal to 1. The battery provided by the invention has the characteristics of excellent dynamic performance and long cycle life under high-rate quick charging.

Description

Negative pole piece and battery
Technical Field
The invention relates to the field of batteries, in particular to a negative pole piece and a battery.
Background
The rechargeable battery has the outstanding characteristics of light weight, high energy density, no pollution, no memory effect, long service life and the like, so the rechargeable battery is widely applied to new energy automobiles. However, the long charging time is one of the important factors limiting the rapid popularization of new energy vehicles. From the technical principle, the core of the battery quick charging technology is to improve the moving speed of ions between a positive electrode and a negative electrode through chemical system adjustment and design optimization. If the negative electrode can not bear large-current charging, metal can be separated out from the negative electrode during quick charging, and meanwhile, a large amount of byproducts can be generated on the surface of the negative electrode, so that the cycle life and the safety of the battery are influenced. Therefore, the key of the quick charging technology lies in the design of the negative active material and the negative pole piece.
Disclosure of Invention
In view of the problems in the background art, the present invention aims to provide a negative electrode plate and a battery, which have the characteristics of excellent dynamic performance and long cycle life under high-rate quick charge.
In order to achieve the above object, in a first aspect of the present invention, the present invention provides a negative electrode plate, which includes a negative electrode current collector and at least one negative electrode current collector disposed on the negative electrode current collectorA negative electrode membrane on one surface and comprising a negative electrode active material. The powder compacted density P of the negative active material under 3000Kg of pressure3kAnd average particle diameter D of negative electrode active materialvThe relationship between 50 satisfies: 0.15 is less than or equal to 1/Dv50+0.2/P3kLess than or equal to 1. Wherein the average particle diameter Dv50 in μm and a powder compaction density P3kHas a unit of g/cm3。
In a second aspect of the invention, the invention provides a battery comprising a negative electrode tab according to the first aspect of the invention.
Compared with the prior art, the invention at least comprises the following beneficial effects:
according to the invention, through reasonably designing the negative active material, the powder compaction density of the negative active material and the average particle size of the negative active material satisfy a certain relationship, and the battery with excellent dynamic performance and long cycle life under high-rate quick charging is obtained.
Detailed Description
The negative electrode sheet and the battery according to the present invention are described in detail below.
First, a negative electrode sheet according to a first aspect of the present invention is explained, which includes a negative electrode current collector and a negative electrode membrane disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. The powder compacted density P of the negative active material under 3000Kg of pressure3kAnd average particle diameter D of negative electrode active materialvThe relationship between 50 satisfies: 0.15 is less than or equal to 1/Dv50+0.2/P3kLess than or equal to 1. Wherein the average particle diameter Dv50 in μm and a powder compaction density P3kHas a unit of g/cm3。
During the charging process of the battery, the following 3 electrochemical processes are needed for the negative pole piece: (1) active ions (such as lithium ions, sodium ions and the like) removed from the positive active material enter the electrolyte, and enter the inside of the pore passage of the negative membrane along with the electrolyte, so that the liquid phase conduction of the active ions in the pore passage is completed, and the liquid phase conduction comprises liquid phase diffusion and electromigration; (2) the active ions and the electrons complete charge exchange on the surface of the cathode active material; (3) the active ions are conducted from the surface of the negative active material to the inside of the negative active material crystal in a solid phase.
The quick charging capacity of the battery is closely related to the particle size of the negative active material and the pore structure of the negative membrane. Generally, the larger the negative electrode active material particles are, the larger the solid phase conduction resistance of active ions in the negative electrode active material particles is, and the poorer the quick charge capability of the battery is, the smaller the negative electrode active material particles are, the smaller the solid phase conduction resistance of the active ions in the negative electrode active material particles is, and the better the quick charge capability of the battery is. The more developed the pore structure of the negative electrode membrane is, the smaller the active ion liquid phase conduction resistance is, the better the dynamic performance of the battery is, and the faster the charging speed is. The pore structure of the negative electrode diaphragm can be measured by the powder compaction density of the negative electrode active material under 3000Kg pressure, and the smaller the powder compaction density is, the more developed the pore structure of the negative electrode diaphragm obtained after the negative electrode slurry prepared by dispersing the negative electrode active material into a solvent is subjected to the processes of coating, drying, compacting and the like, and the stronger the maintenance capability of the pore structure of the negative electrode diaphragm in the charging and discharging process is.
In the design of the negative pole piece, the powder body of the negative pole active material is compacted to have the density P3kAnd average particle diameter D of negative electrode active materialv50 when considered in combination, the powder compaction density P of the negative electrode active material3kAnd average particle diameter D of negative electrode active materialvThe relation between 50 satisfies 0.15 ≦ 1/Dv50+0.2/P3kWhen the charge ratio is less than or equal to 1, the battery with excellent dynamic performance and long cycle life under high-rate quick charge can be obtained.
Average particle diameter D of negative electrode active materialv50 too small or powder compaction density P of negative active material3kToo small results in 1/Dv50+0.2/P3kWhen the upper limit of (2) is more than 1, the overall performance of the battery is poor. This is because the average particle diameter D of the negative electrode active materialv50 is too small, the adhesion force of the negative pole piece is small, powder falls easily, the electronic conductance of the negative pole piece is greatly influenced, the dynamic performance cannot meet the requirement, and the fast charging speed cannot be borne; powder compacted density P of negative electrode active material3kWhen the size of the membrane is too small, the pore structure of the negative membrane is developed, but the contact surface of the negative active material and the electrolyte is more, so that the negative electrode and the electrolyte are poorThe side reactions among the electrolytes are more, the cycle performance of the battery is greatly influenced, and particularly the cycle performance of the battery in a high-temperature environment is poor.
Average particle diameter D of negative electrode active materialv50 excess or powder compaction density P of negative active material3kToo large to result in 1/Dv50+0.2/P3kWhen the lower limit of (b) is less than 0.15, the overall performance of the battery is also poor. This is because the average particle diameter D of the negative electrode active materialv50, the solid phase conduction of active ions in the battery is difficult, the dynamic performance of the battery is poor, and the use requirement of the battery for higher charging speed cannot be met; powder compacted density P of negative electrode active material3kToo large, the pore structure of the negative membrane is not developed enough, the maintenance capability of the pore structure is poor during circulation, the liquid phase conduction resistance of active ions is large, the dynamic performance of the battery is poor, and the battery cannot bear a fast charging speed.
Preferably, the powder compaction density P of the negative electrode active material3kAnd average particle diameter D of negative electrode active materialvThe relation between 50 satisfies 0.15 ≦ 1/Dv50+0.2/P3k≤0.5。
In the negative electrode sheet of the first aspect of the invention, preferably, the average particle diameter D of the negative electrode active materialv50 is 1.2 to 25 μm, and more preferably, the average particle diameter D of the negative electrode active materialv50 is 3.5 to 21 μm, and more preferably, the average particle diameter D of the negative electrode active materialv50 is 5-15 μm.
In the negative electrode sheet of the first aspect of the invention, preferably, the negative electrode active material has a powder compacted density P of 3000Kg under pressure3kIs 0.2g/cm3～2.1g/cm3Further preferably, the negative electrode active material has a powder compacted density P of 3000Kg pressure3kIs 0.5g/cm3～1.9g/cm3Still more preferably, the negative electrode active material has a powder compacted density P of 3000Kg pressure3kIs 1.3g/cm3～1.7g/cm3。
In the negative electrode sheet of the first aspect of the present invention, the specific type of the negative electrode active material is not particularly limited, and may be selected according to actual requirements. Preferably, the negative active material can be selected from one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials and lithium titanate. Wherein, the graphite can be selected from one or more of artificial graphite and natural 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.
In the negative electrode plate of the first aspect of the present invention, the negative electrode diaphragm further includes a conductive agent and a binder, and the kind and content of the conductive agent and the binder are not particularly limited and may be selected according to actual requirements.
In the negative electrode sheet of the first aspect of the present invention, the kind of the negative electrode current collector is not particularly limited, and may be selected according to actual requirements, and preferably, a copper foil may be used.
In the negative electrode sheet of the first aspect of the invention, the particle diameter D of the negative active materialv50 can be measured using a laser diffraction particle size distribution measuring instrument (Mastersizer 3000). Powder compacted density P of negative electrode active material3kThe test can be carried out using an electronic pressure tester (UTM7305) at 3000Kg pressure.
Next, a battery according to a second aspect of the present invention is described, which includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator, wherein the negative electrode sheet is the negative electrode sheet according to the first aspect of the present invention.
In order to ensure the safety of the battery, the battery is usually designed so that the number of the acceptable active ion vacancies of the negative electrode is larger than the number of the extractable active ions of the positive electrode, but the larger the capacity excess coefficient of the battery is, the lower the utilization rate of the acceptable active ion vacancies of the negative electrode is when the battery is fully charged, and the lower the energy density of the battery is.
Meanwhile, the energy density of the battery is closely related to the particle size of the negative active material. Generally, the larger the negative electrode active material particles are, the more sites on the surface of the negative electrode active material for active ion embedding are, the higher the gram capacity of the negative electrode active material is, and the capacity target can be achieved only by a small amount of negative electrode active material during battery design, so that the larger the negative electrode active material particles are, the more the energy density of the battery is improved.
In the battery of the second aspect of the invention, the average particle diameter D of the negative electrode active material is setv50 is considered in combination with the capacity excess coefficient CB of the battery when the relationship between the two satisfies: d is not less than 5vWhen the ratio of 50+6/CB is less than or equal to 30, the dynamic performance of the battery and the cycle life under high-rate quick charge can be further improved, and higher energy density can be considered. Wherein the capacity excess coefficient CB of the battery is the ratio of the negative electrode capacity to the positive electrode capacity in the same area.
Average particle diameter D of negative electrode active materialvToo large of 50 or too small of the capacity excess coefficient CB of the battery results in DvWhen the upper limit of 50+6/CB exceeds 30, the comprehensive performance of the battery is poor. This is because the average particle diameter D of the negative electrode active materialv50 is too large, the negative pole slurry is easy to settle, salient points are easy to appear during coating, the excellent rate of the negative pole piece product is low, and the cycle performance of the battery is also poor; the capacity excess coefficient CB of the battery is too small, the negative electrode is in an excessively high SOC state during full charge, the negative electrode potential caused by polarization is low during high-rate charge, active ions are easily reduced and separated out at the negative electrode, and high potential safety hazards exist.
Average particle diameter D of negative electrode active materialvD is caused by too small 50 or too large capacity excess coefficient CB of the batteryvWhen the lower limit of 50+6/CB is less than 5, the overall performance of the battery is also poor. This is because the average particle diameter D of the negative electrode active materialvWhen the content of the active material is over 50, the number of sites for embedding active ions on the surface is small, the gram capacity is low, a large amount of negative electrode active material is needed to achieve the expected capacity target during battery design, and the energy density of the battery is low; if the capacity excess coefficient CB of the battery is too large, the utilization rate of the negative electrode acceptable active ion vacancies during charging becomes low, and the energy density of the battery also decreases.
Preferably, the average particle diameter D of the anode active materialvThe relation between 50 and the capacity excess coefficient CB of the battery satisfies D is more than or equal to 6v50+6/CB is less than or equal to 27, and is further preferredOptionally, the average particle diameter D of the negative electrode active materialvThe relationship between 50 and the capacity excess coefficient CB of the battery satisfies 10 < Dv50+6/CB≤20。
In the battery of the second aspect of the present invention, the capacity excess coefficient CB of the battery is preferably 0.8 to 2.5, and more preferably 1.0 to 1.8.
In the battery of the second aspect of the present invention, the type and composition of the positive electrode plate are not particularly limited, and may be selected according to actual requirements.
In the battery of the second aspect of the present invention, the kind of the separator is not particularly limited, and may be any separator material used in existing batteries, such as polyethylene, polypropylene, polyvinylidene fluoride, and multilayer composite films thereof, but is not limited thereto.
In the battery of the second aspect of the present invention, the specific type and composition of the electrolyte are not particularly limited, and may be selected according to actual requirements.
It should be noted that the battery according to the second aspect of the present application may be a lithium ion battery, a sodium ion battery, or any other battery using the negative electrode sheet according to the first aspect of the present invention.
When the battery is a lithium ion battery:
the positive active material may be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, olivine-structured lithium-containing phosphate, and the like, but the present application is not limited to these materials, and other conventionally known materials that may be used as a positive active material for a lithium ion battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. Preferably, the positive active material may be selected from LiCoO2、LiNiO2、LiMnO2、LiMn2O4、LiNi1/3Co1/3Mn1/3O2(NCM333)、LiNi0.5Co0.2Mn0.3O2(NCM523)、LiNi0.6Co0.2Mn0.2O2(NCM622)、LiNi0.8Co0.1Mn0.1O2(NCM811)、LiNi0.85Co0.15Al0.05O2、LiFePO4、LiMnPO4One or more of them.
When the battery is a sodium ion battery:
the positive electrode active material can be selected from transition metal oxide NaxMO2(M is a transition metal, preferably one or more selected from Mn, Fe, Ni, Co, V, Cu and Cr, 0<x is less than or equal to 1), polyanionic materials (phosphate, fluorophosphate, pyrophosphate, sulfate), Prussian blue materials and the like, but the application is not limited to the materials, and other conventionally known materials which can be used as the positive active material of the sodium-ion battery can be used. These positive electrode active materials may be used alone or in combination of two or more. Preferably, the positive active material may be selected from NaFeO2、NaCoO2、NaCrO2、NaMnO2、NaNiO2、NaNi1/2Ti1/2O2、NaNi1/2Mn1/2O2、Na2/3Fe1/3Mn2/3O2、NaNi1/3Co1/3Mn1/3O2、NaFePO4、NaMnPO4、NaCoPO4Prussian blue material with the general formula AaMb(PO4)cOxY3-xWherein A is selected from H+、Li+、Na+、K+、NH4+M is transition metal cation, preferably one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu and Zn, Y is halogen anion, preferably one or more selected from F, Cl and Br, 0<a≤4，0<b is less than or equal to 2, c is less than or equal to 1 and less than or equal to 3, and x is more than or equal to 0 and less than or equal to 2).
The present application is further illustrated below by taking a lithium ion battery as an example and combining specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.
The batteries of examples 1 to 40 and comparative examples 1 to 9 were each prepared as follows.
(1) Preparation of positive pole piece
Mixing a positive electrode active material NCM523, a conductive agent acetylene black and a binder PVDF according to a mass ratio of 96:2:2, adding a solvent NMP, and stirring under the action of a vacuum stirrer until the system is uniform to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil, airing at room temperature, transferring to an oven for continuous drying, and then performing cold pressing and slitting to obtain the positive electrode piece.
(2) Preparation of negative pole piece
Mixing the negative electrode active material, the conductive agent acetylene black, the thickening agent CMC and the binder SBR shown in the table 1 according to the mass ratio of 96.4:1:1.2:1.4, adding solvent deionized water, and stirring the mixture under the action of a vacuum stirrer until the system is uniform to obtain negative electrode slurry; and uniformly coating the negative electrode slurry on a copper foil of a negative current collector, airing at room temperature, transferring to an oven for continuous drying, and then performing cold pressing and slitting to obtain a negative electrode plate.
(3) Preparation of the electrolyte
Mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1 to obtain an organic solvent, and then fully drying lithium salt LiPF6Dissolving the mixture in the mixed organic solvent to prepare electrolyte with the concentration of 1 mol/L.
(4) Preparation of the separator
Selected from polyethylene films as barrier films.
(5) Preparation of lithium ion battery
Stacking the positive pole piece, the isolating film and the negative pole piece in sequence to enable the isolating film to be positioned between the positive pole piece and the negative pole piece to play an isolating role, and then winding to obtain a bare cell; and placing the bare cell in an outer packaging shell, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery.
Next, performance tests of the lithium ion battery are explained.
(1) And (3) testing the dynamic performance: and (3) repeating the lithium ion batteries prepared in the examples and the comparative examples at 25 ℃ for 10 times by fully charging at 4C and fully discharging at 1C, fully charging at 4C, disassembling the negative pole piece and observing the lithium precipitation condition on the surface of the negative pole piece. Wherein, the lithium precipitation area of the surface of the negative electrode of less than 5 percent is considered to be slightly lithium precipitation, the lithium precipitation area of the surface of the negative electrode of 5 percent to 40 percent is considered to be moderately lithium precipitation, and the lithium precipitation area of the surface of the negative electrode of more than 40 percent is considered to be severely lithium precipitation.
(2) And (3) testing the cycle performance: the lithium ion batteries prepared in examples and comparative examples were charged at a rate of 3C and discharged at a rate of 1C at 25C, and full charge discharge cycle tests were performed until the capacity of the lithium ion battery had decayed to 80% of the initial capacity, and the number of cycles was recorded.
(3) Actual energy density test: fully charging the lithium ion batteries prepared in the examples and the comparative examples at a rate of 1C and fully discharging the lithium ion batteries at a rate of 1C at 25 ℃, and recording the actual discharge energy at the moment; weighing the lithium ion battery at 25 ℃ by using an electronic balance; the ratio of the actual discharge energy of the lithium ion battery 1C to the weight of the lithium ion battery is the actual energy density of the lithium ion battery.
Wherein, when the actual energy density is less than 80% of the target energy density, the actual energy density of the battery is considered to be very low; when the actual energy density is greater than or equal to 80% of the target energy density and less than 95% of the target energy density, the actual energy density of the battery is considered to be low; when the actual energy density is greater than or equal to 95% of the target energy density and less than 105% of the target energy density, the actual energy density of the battery is considered to be moderate; when the actual energy density is not less than 105% of the target energy density and less than 120% of the target energy density, the actual energy density of the battery is considered to be high; when the actual energy density is 120% or more of the target energy density, the actual energy density of the battery is considered to be very high.
Table 1: parameters and test results for examples 1-40 and comparative examples 1-9
Figure BDA0001644937120000081
Figure BDA0001644937120000091
Examples 1 to 8 and examples 9 to 15 give powder compaction densities P of negative electrode active materials3kIs 1.8g/cm3And 1.2g/cm3The cell capacity excess coefficient CB was fixed to 1.2, and the powder compaction density P of the negative electrode active material was determined3kThe average particle diameter D of the negative electrode active material was observed under the same conditions as the capacity excess coefficient CB of the batteryv50 on cell performance. When the average particle diameter D of the negative electrode active materialv50 is relatively too small, and the powder compaction density P of the negative electrode active material3kMismatch, resulting in 1/Dv50+0.2/P3k>1, the negative pole piece has small adhesive force and is easy to fall off, so that the dynamic performance of the battery is poor due to insufficient electronic conductivity of the negative pole piece, lithium is seriously separated during high-rate quick charging, and water is easy to circulate and jump. Comparative example 1 and comparative example 2 were circulated for 430 and 850 cycles respectively for volume diving. When the average particle diameter D of the negative electrode active materialv50 is relatively too large, and has a powder compacted density P with respect to the negative electrode active material3kMismatch, resulting in 1/Dv50+0.2/P3k<At 0.15, the solid phase conduction resistance of lithium ions in the negative active material is too large, so that the dynamic performance of the battery is poor, the negative electrode is seriously separated out lithium during high-rate quick charge, and the battery is easy to cycle and jump; further, the average particle diameter D of the negative electrode active materialv50 is relatively too large, the cathode slurry is easy to settle, and serious salient points are easy to appear on the surface of the cathode membrane, so that the cycle life of the battery is further influenced. Comparative example 3 capacity diving after 300 cycles.
Examples 18 to 22 and examples 23 to 28 give the average particle diameter D of the negative electrode active material, respectivelyv50 are 20 μm and 18 μm, and the capacity excess coefficient CB of the battery is fixed to 1.2, the average particle diameter D of the negative electrode active materialv50 and the capacity excess coefficient CB of the battery, the powder compaction density P of the negative electrode active material is observed3kImpact on battery performance. When the powder body of the negative electrode active material is compacted to a density P3kRelatively too small, and the negative electrode activityAverage particle diameter D of the materialv50 mismatch, resulting in 1/Dv50+0.2/P3k>1, the pore structure of the negative membrane is very developed, the dynamic performance of the battery is good, lithium cannot be separated out from the negative electrode during high-rate quick charging, but the negative electrode active material and the electrolyte have too many contact surfaces, so that the side reaction between the negative electrode and the electrolyte is excessive, the capacity attenuation is fast in the battery circulation process, and the battery is unfavorable for the cycle life of the battery. Comparative example 4 was subjected to volume diving after 1100 cycles, and comparative example 6 was subjected to volume diving after 1200 cycles. When the powder body of the negative electrode active material is compacted to a density P3kRelatively excessively large, and does not match with the average particle diameter Dv50 of the negative electrode active material, resulting in 1/Dv50+0.2/P3k<At 0.15, the pore structure of the negative electrode diaphragm is not developed enough, the pore structure maintaining capability is poor during circulation, the lithium ion liquid phase conduction resistance is too large, so that the dynamic performance of the battery is poor, lithium is seriously separated from the negative electrode during high-rate quick charging, and the cycle water-skipping is easy. Comparative example 5 was run for 460 cycles and comparative example 7 was run for 640 cycles.
While reasonably adjusting the average particle diameter D of the negative electrode active materialv50 and powder compaction density P of negative active material3kThe relationship between them, make both match and 1/Dv50+0.2/P3kWhen the charge capacity is 0.15-1, the battery has the characteristics of excellent dynamic performance and long cycle life under high-rate quick charge. And preferably, 1/Dv50+0.2/P3kBetween 0.15 and 0.5.
Wherein the average particle diameter D of the negative electrode active materialv50 is preferably in the range of 1.2 to 25 μm, and the powder compaction density P of the negative electrode active material3kIs preferably in the range of 0.22g/cm3～2.1g/cm3. And the applicant intends to say that when the average particle diameter D of the negative electrode active material isv50. Powder compacted density P of negative electrode active material3kDo not fall within the above preferred ranges, but satisfy 1/Dv50+0.2/P3kBetween 0.15 and 1, the battery has the characteristics of excellent dynamic performance and long cycle life under high-rate quick charge, such as example 16 and example 17, althoughThe negative electrode active material has a larger average particle diameter Dv50, but with a suitable powder compaction density P3kMake 1/Dv50+0.2/P3kWhen the content is 0.15-1, the battery still has good dynamic performance and cycle performance. Although the average particle diameter D of the negative electrode active material was in comparative examples 8 and 9v50. Powder compacted density P3kBoth fall within the preferred ranges, but are not of the same size, 1/Dv50+0.2/P3kThe value of (A) is not between 0.15 and 1, and the dynamic performance and the cycle performance of the battery are poor.
Examples 29 to 33 give average particle diameters D of negative electrode active materialsv50 was fixed at 1.2 μm, and the powder compacted density P3k was fixed at 1.6g/cm3Test result of (1/D) at this timev50+0.2/P3kThe fixation is 0.958, lithium is not seriously precipitated when the battery is rapidly charged at a high multiplying power, the dynamic performance of the battery is excellent, the design requirement of the rapid charging of the battery can be met, the performance of the battery can be further improved by adjusting the capacity excess coefficient CB of the battery at the moment, but when the capacity excess coefficient CB of the battery is relatively overlarge, D isv50+6/CB<5, but the actual energy density of the battery is low.
Examples 34 to 37 show the average particle diameter D of the negative electrode active materialv50 fixed at 25 μm and powder compacted density P3kFixed at 1.2g/cm3Test result of (1/D) at this timev50+0.2/P3kFixed at 0.207, where the capacity excess coefficient CB of the battery is adjusted, the performance of the battery can be further improved, but when the capacity excess coefficient CB of the battery is relatively too small, Dv50+6/CB>At 30, although the energy density of the battery is high, the negative electrode is in an excessively high SOC state during full charge, and the negative electrode potential due to polarization during high-rate charge is low, which tends to cause reductive precipitation of lithium ions at the negative electrode, and the dynamic performance and cycle performance of the battery are relatively deteriorated.

Claims (4)

1. A battery comprises a positive pole piece, a negative pole piece, electrolyte and an isolating film, wherein the negative pole piece comprises a negative current collector and a negative diaphragm which is arranged on at least one surface of the negative current collector and comprises a negative active material;
it is characterized in that the preparation method is characterized in that,
the negative active material is selected from graphite;
the powder compacted density P of the negative active material under 3000Kg of pressure3kAnd an average particle diameter D of the negative electrode active materialvThe relationship between 50 satisfies: 0.15 is less than or equal to 1/Dv50+0.2/P3k≤0.211；
The average particle diameter D of the negative electrode active materialv50 is 10-21 μm;
the powder compacted density P of the negative active material under 3000Kg of pressure3kIs 1.8g/cm3～2.1g/cm3，
Wherein the content of the first and second substances,
average particle diameter DvThe unit of 50 is μm;
powder compacted density P3kHas a unit of g/cm3。
2. The battery according to claim 1, wherein the graphite is selected from one or more of artificial graphite and natural graphite.
3. The battery according to claim 1, wherein a capacity excess coefficient CB of the battery and an average particle diameter D of the negative electrode active materialvThe relationship between 50 satisfies: d is more than or equal to 10v50+6/CB is less than or equal to 20; wherein the capacity excess coefficient CB of the battery is the ratio of the negative electrode capacity to the positive electrode capacity under the same area.
4. The battery according to claim 3, wherein the capacity excess coefficient CB of the battery is 1.0-1.8.
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