Negative electrode active materials, negative electrode sheets, batteries, battery modules and electrical equipment

Abstract

The present invention discloses a negative electrode active material, a negative electrode sheet, a battery, a battery module and an electric device. The particle size distribution of the negative electrode active material is A, the defect degree is B, the particle size distribution A is (D90-D10) / D50, and the defect degree B of the negative electrode active material is I D / I G , and the ratio of the particle size distribution A to the defectivity B of the negative electrode active material is 6.0≤A / B≤7.2. By controlling the ratio of the particle size distribution A to the defectivity B of the negative electrode active material within the above range, the cycle performance and storage performance of the battery are significantly improved.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a negative electrode active material, a negative electrode plate, a battery, a battery module and an electrical device. Background Art

[0002] The negative electrode active material is the main body of lithium storage in lithium-ion batteries, and has an important influence on the embedding and extraction of lithium ions during the charging and discharging process. Therefore, the performance of the negative electrode active material directly affects the performance of the lithium battery. However, the current cycle performance and storage performance of lithium batteries are still relatively low, and there is room for improvement. Summary of the Invention

[0003] In order to further improve the storage performance and cycle performance of a battery, embodiments of the present invention disclose a negative electrode active material, a negative electrode plate, a battery, a battery module, and an electrical device.

[0004] In a first aspect, embodiments of the present application provide a negative electrode active material.

[0005] The particle size distribution of the negative electrode active material is A, the defectivity is B, the particle size distribution A is (D90-D10) / D50, and the defectivity B of the negative electrode active material is I D / I G , and the ratio of the particle size distribution A to the defect degree B of the negative electrode active material is 6.0≤A / B≤7.2.

[0006] As an optional implementation, in an embodiment of the present invention, the ratio of the particle size distribution A to the defectivity B of the negative electrode active material is 6.17≤A / B≤6.91.

[0007] As the values ​​of the particle size distribution A and the defect degree B of the negative electrode active material increase, the battery's cycle capacity retention, storage capacity retention rate, and storage capacity recovery rate all show a trend of first increasing and then decreasing. When the ratio of the particle size distribution A and the defect degree B of the negative electrode active material is greater than or equal to 6.17 and less than or equal to 6.91, the battery's cycle capacity retention, storage capacity retention rate, and storage capacity recovery rate are better. Therefore, the ratio of the particle size distribution A and the defect degree B of the negative electrode active material is preferably 6.17≤A / B≤6.91.

[0008] As an optional implementation, in an embodiment of the present invention, the value of the particle size distribution A of the negative electrode active material is 0.8 to 2.0.

[0009] At this time, there are fewer fine particles and larger particles in the negative electrode active material, and the particle size distribution of the negative electrode active material is more moderate, indicating that there are fewer defects on the surface of the negative electrode active material. At this time, the defect degree B is also reduced accordingly, which can effectively reduce the occurrence of side reactions inside the battery and improve the storage performance of the battery.

[0010] When the above-mentioned particle size distribution A is too large, it indicates that the particle size distribution of the negative electrode active material is wider. At this time, there are too many fine particles and large particles in the negative electrode active material. If there are too many fine particles, there will be more defects on the surface of the negative electrode active material, and the value of the defect degree B will increase accordingly. The side reactions inside the battery will increase, and the storage performance of the battery will decrease. If there are too many large particles, the expansion rate of the negative electrode active material during the battery cycle will be greater, resulting in an increased safety risk of the battery during use, and the lithium ion transmission path will be too long, and the battery cycle performance will further deteriorate.

[0011] When the particle size distribution A is too small, it indicates that the particle size distribution of the negative electrode active material is too concentrated, the negative electrode active material can withstand lower compaction, and overpressure is more likely to occur, resulting in decreased cycle performance.

[0012] As an optional implementation, in an embodiment of the present invention, the defectivity B of the negative electrode active material is 0.1 to 0.35.

[0013] When the defectivity B is between 0.1 and 0.35, it can effectively reduce the occurrence of side reactions within the battery cell, improve the storage performance of the battery cell, and at this time, the battery's kinetic performance is better and lithium deposition is less likely to occur. When the defectivity B of the negative electrode active material is too small, the battery's kinetic performance deteriorates and lithium deposition is prone to occur. When the defectivity B is too large, the side reactions within the battery increase and the battery's storage performance decreases.

[0014] At the same time, the ratio of the particle size distribution A and the defectivity B of the negative electrode active material is controlled to be 6.0≤A / B≤7.2, the value of the particle size distribution A is 0.8~2.0, and the value of the defectivity B is 0.1~0.35. This is the most preferred option. At the same time, the ratio of the particle size distribution A and the defectivity B of the negative electrode active material, the value of the particle size distribution A and the value of the defectivity B are controlled within the above range. These parameters are coordinated with each other to simultaneously make the storage performance and cycle performance of the battery better.

[0015] As an optional embodiment, in an embodiment of the present invention, D90 of the negative electrode active material is 21.0 μm to 32.0 μm, D10 of the negative electrode active material is 4.0 μm to 8.5 μm, and D50 of the negative electrode active material is 12.0 μm to 18.0 μm.

[0016] When the D50 of the negative electrode active material is too small, the specific surface area of ​​the negative electrode active material is large, and more side reactions are likely to occur during battery storage, resulting in a decrease in storage performance; when D50 is too large, the path of lithium ion insertion and extraction becomes longer, and the battery is prone to lithium deposition during the cycle process, resulting in a deterioration of the cycle performance.

[0017] As an optional embodiment, in an embodiment of the present invention, the above-mentioned negative electrode active material includes one or more of a carbon negative electrode material, a tin-based negative electrode material, a lithium-containing transition metal nitride negative electrode material, an alloy negative electrode material and a nanoscale negative electrode material.

[0018] The solution of this application is universally applicable to any negative electrode active material, such as carbon negative electrode materials, tin-based negative electrode materials, lithium-containing transition metal nitride negative electrode materials, alloy negative electrode materials, and nanoscale negative electrode materials, including but not limited to these negative electrode materials. Mixtures of two or more negative electrode materials are also applicable, and the embodiments of this application are not specifically limited here.

[0019] In a second aspect, the present application provides a negative electrode plate, which includes a current collector and a negative electrode active layer stacked on the current collector, and the negative electrode active layer includes the negative electrode active material mentioned in the first aspect.

[0020] In a third aspect, the present application provides a battery, comprising:

[0021] electrolyte,

[0022] a positive electrode sheet, wherein the positive electrode sheet is at least partially immersed in the electrolyte;

[0023] a diaphragm, located on one side of the positive electrode sheet and at least partially immersed in the electrolyte;

[0024] And the negative electrode plate described in the second aspect, the negative electrode plate is arranged on the side of the separator away from the positive electrode plate and is at least partially immersed in the electrolyte.

[0025] In a fourth aspect, the present application provides a battery module, which includes the battery described in the third aspect.

[0026] In a fifth aspect, an embodiment of the present application provides an electrical device, which includes the battery module mentioned in the fourth aspect.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] Through extensive research, the applicant has found that by controlling the ratio of the particle size distribution A to the defectivity B of the negative electrode active material to 6.0≤A / B≤7.2, the battery's cycle performance and storage performance can be significantly improved. It can be seen that by controlling the ratio of the particle size distribution A to the defectivity B, without simultaneously regulating other parameters of the negative electrode active material such as specific surface area, porosity or pore volume, excellent cycle performance and storage performance can be obtained. When the value of A / B is less than 6.0, it means that the particle size distribution of the negative electrode active material is too concentrated or there are too many surface defects. When the particle size distribution of the negative electrode active material is too concentrated, the negative electrode active material can withstand low compaction and is prone to overpressure, resulting in a decrease in the battery's cycle performance. When the surface defects of the negative electrode active material are too many, it will lead to an increase in side reactions inside the battery, thereby reducing the storage performance. When the value of A / B is greater than 7.2, it means that the particle size distribution of the negative electrode active material is too large or there are insufficient surface defects. Lithium plating may occur during the battery cycle, resulting in a decrease in cycle performance. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] The increase in surface defects of negative electrode active materials is beneficial to improving the kinetic performance of the battery, thereby improving the cycle performance. However, the increase in surface defects of negative electrode active materials will also increase side reactions during battery storage, resulting in a decrease in storage capacity retention rate and storage capacity recovery rate. Therefore, when the battery's cycle performance is better, the storage performance is relatively poor, and it is difficult to improve both at the same time.

[0031] The present application found that by controlling the ratio of the particle size distribution A to the defect degree B of the negative electrode active material within a specific range, the storage performance and cycle performance of the battery can be better balanced, while achieving a significant improvement in the storage performance and cycle performance of the battery, while breaking through the limitations of the original low storage performance and cycle performance. The battery's cycle capacity retention rate is increased to more than 94%, and the storage capacity retention rate and storage capacity recovery rate are both increased to more than 95%, which is of great significance to the research and development of batteries.

[0032] The technical solution of the present invention will be further described below with reference to embodiments.

[0033] In a first aspect, embodiments of the present application provide a negative electrode active material.

[0034] The particle size distribution of the negative electrode active material is A, the defectivity is B, the particle size distribution A is (D90-D10) / D50, and the defectivity B of the negative electrode active material is I D / I G , and the ratio of the particle size distribution A to the defect degree B of the negative electrode active material is 6.0≤A / B≤7.2.

[0035] It should be noted that D10, D50, and D90 are all parameters of the particle size of powder particles. D10 represents the particle size corresponding to when the cumulative particle size distribution percentage reaches 10%, that is, the volume content of particles smaller than this particle size accounts for 10% of all particles.

[0036] D50 represents the particle size at which the cumulative particle size distribution percentage reaches 50%, also known as the median or median diameter. This means that the volume fraction of particles smaller than this diameter accounts for 50% of all particles. This is a typical value for particle size that accurately divides the population into two equal parts: 50% of the particles exceed this value, and 50% of the particles are smaller than this value.

[0037] D90 represents the particle size corresponding to when the cumulative particle size distribution percentage reaches 90%, that is, the volume content of particles smaller than this particle size accounts for 90% of all particles.

[0038] The ratio of (D90-D10) / D50 can reflect the concentration of particles. The larger the (D90-D10) / D50 is, the lower the concentration of particles is and the wider the particle size distribution is. The smaller the (D90-D10) / D50 is, the higher the concentration of particles is and the narrower the particle size distribution is.

[0039] I D The Raman spectrum is located at 1350 cm -1 The peak intensity at I G Located at 1580cm -1 The peak intensity at I D / I G The larger the particle size, the higher the defectivity of the particle. D / I G The smaller it is, the lower the defectivity of the particle.

[0040] Through extensive research, the applicant has discovered that controlling the ratio of the negative electrode active material's particle size distribution A to the defectivity B within a range of 6.0 ≤ A / B ≤ 7.2 significantly improves the battery's cycling and storage performance. This indicates that controlling the ratio of the negative electrode active material's particle size distribution A to the defectivity B is key to achieving excellent cycling and storage performance. Other parameters of the negative electrode active material, such as oil absorption, porosity, or pore volume, have minimal impact on the battery's cycling and storage performance. When the A / B value is less than 6.0, it indicates that the negative electrode active material's particle size distribution is too concentrated or that there are too many surface defects. This concentration reduces the negative electrode active material's ability to withstand compaction and makes it prone to overpressure, resulting in reduced battery cycling performance. Excessive surface defects in the negative electrode active material increase side reactions within the battery, thereby reducing the battery's storage performance. When the A / B value is greater than 7.2, it indicates that the negative electrode active material's particle size distribution is too large or that there are insufficient surface defects. Lithium deposition is likely to occur during cycling, leading to reduced battery cycling performance.

[0041] Illustratively, the ratio of particle size distribution A to defectivity B is 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, etc.

[0042] As the values ​​of the particle size distribution A and the defect degree B of the negative electrode active material increase, the battery's cycle capacity retention, storage capacity retention rate, and storage capacity recovery rate all show a trend of first increasing and then decreasing. When the ratio of the particle size distribution A and the defect degree B of the negative electrode active material is greater than or equal to 6.17 and less than or equal to 6.91, the battery's cycle capacity retention, storage capacity retention rate, and storage capacity recovery rate are better. Therefore, the ratio of the particle size distribution A and the defect degree B of the negative electrode active material is preferably 6.17≤A / B≤6.91.

[0043] Furthermore, the particle size distribution A of the negative electrode active material is 0.8 to 2.0. In this case, the negative electrode active material contains fewer fine and large particles, and the particle size distribution of the negative electrode active material is more moderate, indicating that there are fewer defects on the surface of the negative electrode active material. In this case, the defectivity B is also reduced accordingly, which can effectively reduce the occurrence of side reactions within the battery and improve the battery's storage performance.

[0044] When the above-mentioned particle size distribution A is too large, it indicates that the particle size distribution of the negative electrode active material is wider. At this time, there are too many fine particles and large particles in the negative electrode active material. If there are too many fine particles, there will be more defects on the surface of the negative electrode active material, and the value of the defect degree B will increase accordingly. The side reactions inside the battery will increase, and the storage performance of the battery will decrease. If there are too many large particles, the expansion rate of the negative electrode active material during the battery cycle will be greater, resulting in an increased safety risk of the battery during use, and the lithium ion transmission path will be too long, and the battery cycle performance will further deteriorate.

[0045] When the particle size distribution A is too small, it indicates that the particle size distribution of the negative electrode active material is too concentrated, the negative electrode active material can withstand lower compaction, and overpressure is more likely to occur, resulting in decreased cycle performance.

[0046] Illustratively, the values ​​of the particle size distribution A are 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, and the like.

[0047] Furthermore, the defectivity B of the negative electrode active material is between 0.1 and 0.35. When the defectivity B is between 0.1 and 0.35, it can effectively reduce the occurrence of side reactions within the battery cell, improve the storage performance of the battery cell, and at this time, the battery's kinetic performance is better and lithium deposition is less likely to occur. When the defectivity B of the negative electrode active material is too small, the battery's kinetic performance deteriorates and lithium deposition is more likely to occur. When the defectivity B is too large, the side reactions within the battery increase and the battery's storage performance decreases.

[0048] Illustratively, the value of the defectivity B is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, and the like.

[0049] Furthermore, in some embodiments, the ratio of the particle size distribution A to the defect degree B of the negative electrode active material is controlled to be 6.0≤A / B≤7.2, and the value of the particle size distribution A is 0.8~2.0, and the value of the defect degree B is 0.1~0.35, which is the most preferred solution. At the same time, the ratio of the particle size distribution A to the defect degree B of the negative electrode active material, the value of the particle size distribution A and the value of the defect degree B are controlled within the above range. These parameters cooperate with each other to simultaneously make the storage performance and cycle performance of the battery better.

[0050] In some embodiments, D90 of the negative electrode active material is 21.0 μm to 32.0 μm, D10 of the negative electrode active material is 4.0 μm to 8.5 μm, and D50 of the negative electrode active material is 12.0 μm to 18.0 μm.

[0051] When the D50 of the negative electrode active material is too small, the specific surface area of ​​the negative electrode active material is large, and more side reactions are likely to occur during battery storage, resulting in a decrease in storage performance; when D50 is too large, the path of lithium ion insertion and extraction becomes longer, and the battery is prone to lithium deposition during the cycle process, resulting in a deterioration of the cycle performance.

[0052] In some embodiments, the negative electrode active material includes one or more of a carbon negative electrode material, a tin-based negative electrode material, a lithium-containing transition metal nitride negative electrode material, an alloy negative electrode material, and a nanoscale negative electrode material.

[0053] The solution of this application is universally applicable to any negative electrode active material, such as carbon negative electrode materials, tin-based negative electrode materials, lithium-containing transition metal nitride negative electrode materials, alloy negative electrode materials, and nanoscale negative electrode materials, including but not limited to these negative electrode materials. Mixtures of two or more negative electrode materials are also applicable, and the embodiments of this application are not specifically limited here.

[0054] In a second aspect, the present application provides a negative electrode plate, which includes a current collector and a negative electrode active layer stacked on the current collector, and the negative electrode active layer includes the negative electrode active material mentioned in the first aspect.

[0055] In a third aspect, the present application provides a battery, comprising:

[0056] electrolyte,

[0057] A positive electrode sheet, the positive electrode sheet is at least partially immersed in the electrolyte;

[0058] a diaphragm, located on one side of the positive electrode sheet and at least partially immersed in the electrolyte;

[0059] And the negative electrode plate of the second aspect is arranged on the side of the separator away from the positive electrode plate and is at least partially immersed in the electrolyte.

[0060] In a fourth aspect, the present application provides a battery module, which includes the battery of the third aspect.

[0061] In a fifth aspect, an embodiment of the present application provides an electrical device, which includes the battery module mentioned in the fourth aspect.

[0062] The technical solution of the present invention will be further described below in conjunction with more specific embodiments.

[0063] Example 1

[0064] The present application provides a lithium-ion battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator, wherein the separator is disposed between the positive and negative electrode sheets. The negative electrode sheet comprises an aluminum foil and a negative electrode active layer on the surface of the aluminum foil. The negative electrode active layer comprises graphite, and the graphite has a D90 of 21.5 μm, a D10 of 7.6 μm, a D50 of 17.0 μm, a particle size distribution A of 0.82, a defectivity B of 0.12, and a ratio of particle size distribution A to defectivity B of 6.91.

[0065] The present invention also provides a method for preparing the lithium-ion battery, comprising the following steps:

[0066] Preparation of negative electrode sheet:

[0067] The above-mentioned graphite, conductive carbon black, styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) are mixed uniformly in an appropriate amount of water in a mass ratio of 96%:1%:2%:1% to prepare a negative electrode slurry. The negative electrode slurry is coated on the surface of an aluminum foil and dried to obtain an unrolled negative electrode sheet. The sheet is then rolled using a roller press according to a designed compaction density to obtain a negative electrode sheet with a specific thickness.

[0068] Preparation of lithium-ion batteries:

[0069] Lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed uniformly in an appropriate amount of N-methylpyrrolidone in a mass ratio of 96%:2%:2% to prepare a positive electrode slurry, which was coated on the surface of a copper foil, and the slurry was coated on an aluminum foil of the positive electrode current collector, dried, and cold pressed to obtain a positive electrode;

[0070] Take the above-mentioned negative electrode sheets respectively, put the positive electrode sheets and negative electrode sheets into a press for pressing, and then use a sheet cutter to cut the positive and negative electrode sheets of a certain size respectively, wind the cut positive and negative electrode sheets with a polyethylene separator, and then weld the positive and negative electrode ears, and then use aluminum-plastic film to encapsulate the cells after drying.

[0071] 1 mol / L lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate with a molar ratio of 1:1. The resulting solution is injected into the battery cell as an electrolyte, and finally packaged to form a lithium-ion battery.

[0072] Example 2

[0073] The embodiment of the present application provides a lithium-ion battery, which differs from the first embodiment in that: the D90 of the graphite is 23.5 μm, the D10 is 5.7 μm, the D50 is 15.8 μm, the particle size distribution A value is 1.13, the defectivity B value is 0.16, and the ratio of the particle size distribution A to the defectivity B is 7.06.

[0074] Example 3

[0075] The embodiment of the present application provides a lithium-ion battery, which differs from the first embodiment in that: the D90 of the graphite is 24.4 μm, the D10 is 6.2 μm, the D50 is 14.2 μm, the particle size distribution A value is 1.28, the defectivity B value is 0.19, and the ratio of the particle size distribution A to the defectivity B is 6.73.

[0076] Example 4

[0077] The embodiment of the present application provides a lithium-ion battery, which differs from the first embodiment in that: the D90 of the graphite is 28.3 μm, the D10 is 6.5 μm, the D50 is 15.4 μm, the particle size distribution A value is 1.42, the defectivity B value is 0.23, and the ratio of the particle size distribution A to the defectivity B is 6.17.

[0078] Example 5

[0079] The embodiment of the present application provides a lithium-ion battery, which differs from the first embodiment in that: the D90 of the graphite is 26.8 μm, the D10 is 7.1 μm, the D50 is 16.3 μm, the particle size distribution A value is 1.21, the defectivity B value is 0.26, and the ratio of the particle size distribution A to the defectivity B is 6.19.

[0080] Example 6

[0081] The embodiment of the present application provides a lithium-ion battery, which differs from the first embodiment in that: the D90 of the graphite is 31.2 μm, the D10 is 4.5 μm, the D50 is 13.2 μm, the particle size distribution A value is 2.019, the defectivity B value is 0.3, and the ratio of the particle size distribution A to the defectivity B is 6.73.

[0082] Example 7

[0083] The embodiment of the present application provides a lithium-ion battery, which differs from the first embodiment in that: the D90 of the graphite is 30.6 μm, the D10 is 4.9 μm, the D50 is 12.9 μm, the particle size distribution A value is 2, the defectivity B value is 0.3, and the ratio of the particle size distribution A to the defectivity B is 6.0.

[0084] Example 8

[0085] The embodiment of the present application provides a lithium-ion battery, which differs from the first embodiment in that: the D90 of the graphite is 23.1 μm, the D10 is 6.8 μm, the D50 is 16.3 μm, the particle size distribution A value is 1, the defectivity B value is 0.139, and the ratio of the particle size distribution A to the defectivity B is 7.19.

[0086] Comparative Example 1

[0087] Comparative Example 1 of the present application provides a lithium-ion battery, which differs from Example 1 in that: the D90 of the graphite is 29.3 μm, D10 is 4.6 μm, D50 is 13.4 μm, the value of the particle size distribution A is 1.85, the value of the defectivity B is 0.32, and the ratio of the particle size distribution A to the defectivity B is 5.78.

[0088] Comparative Example 2

[0089] Comparative Example 1 of the present application provides a lithium ion battery, which differs from Example 1 in that: the D90 of the graphite is 30.5 μm, D10 is 4.2 μm, D50 is 12.5 μm, the value of the particle size distribution A is 2.1, the value of the defectivity B is 0.29, and the ratio of the particle size distribution A to the defectivity B is 7.25.

[0090] Experiment 1

[0091] Particle size distribution test

[0092] The lithium-ion battery was discharged to 0% SOC (or 2.5V), and the negative electrode sheet (x / 32cm, x is the total length of the negative electrode sheet) was disassembled. A 3cm*3cm negative electrode sheet was taken and soaked in a DMC solution for 3 hours. After drying in an oven for 1 hour, the negative electrode sheet was immersed in deionized water to peel the negative electrode active material from the copper foil. The obtained aqueous solution of the negative electrode active material of the negative electrode sheet was ultrasonicated for 15 minutes to 30 minutes and then filtered. The aqueous solution was dried in an oven for 1 hour to obtain a block of negative electrode active material. The block of negative electrode active material was ground and the particle size distribution was measured using a laser diffraction particle size analyzer (Malvern Mastersizer3000) according to GB / T According to the provisions of 19077-2016 "Particle Size Distribution Laser Diffraction Method", the particle size distribution of the negative electrode active material is measured, the D10, D50, and D90 of the negative electrode active material are recorded, and the particle size distribution A is calculated using the following method: D90-D10 / D50.

[0093] Experiment 2

[0094] Raman spectroscopy test

[0095] A LabRAM HR Evolution laser microscope Raman spectrometer was used. The Raman spectrum was located at 1350 cm -1 The intensity of the peak at is recorded as I D , the Raman spectrum is located at 1580cm -1 The intensity of the peak at is recorded as I G , and calculate the defect degree B, the calculation method is: I D / I G .

[0096] Experiment 3

[0097] Capacity retention test

[0098] At room temperature (25°C), the lithium-ion batteries prepared in the comparative examples and examples were charged to 3.65V at a constant power rate of 0.5P (P is power, P = nominal capacity × 3.2V), left for 5 minutes, and then discharged to 2.5V at a rate of 0.5P. The discharge capacity was measured, and this was considered one cycle. The capacity retention rate (%) was calculated as follows:

[0099] Capacity retention (%) = current discharge capacity / initial discharge capacity.

[0100] It can be understood that one cycle of the battery is called one charge and discharge process, and the 2000-cycle capacity retention rate refers to the capacity retention rate of the battery after 2000 charge and discharge processes at a test temperature of 25°C.

[0101] Example 4

[0102] Storage performance test

[0103] At room temperature (25°C), the lithium ion batteries obtained in the above comparative examples and embodiments were charged to 3.65V at a constant power rate of 0.5P (P is power, P = nominal capacity × 3.2V), left for 5 minutes, and then discharged to 2.5V at a rate of 0.5P to measure the discharge capacity. The cycle was repeated three times, and the average of the three discharge capacities was taken as the capacity before storage (C1); after being placed at 25°C for 28 days, the battery was further placed for 6 hours, and then discharged to 2.5V at a rate of 0.5P to measure the discharge capacity, and the capacity was determined as the capacity after storage (C2); the battery was then charged to 3.65V at a constant power rate of 0.5P, left for 5 minutes, and finally discharged to 2.5V at a rate of 0.5P to measure the discharge capacity, and the capacity was determined as the capacity after storage recovery (C3).

[0104] Capacity retention rate after storage (%) = capacity after storage (C2) / capacity before storage (C1);

[0105] Capacity recovery rate after storage (%) = capacity recovered after storage (C3) / capacity before storage (C1).

[0106] The test results of Experiments 1 to 4 and the ratio of particle size distribution A to defectivity B are detailed in Table 1.

[0107] Table 1

[0108]

[0109] It can be seen from the data in Table 1 that the A / B values ​​in Examples 1 to 8 are between 6.0 and 7.2, and the cycle capacity retention rate of Examples 1 to 8 is improved to more than 94%, and the storage capacity retention rate and storage capacity recovery rate are simultaneously improved to more than 95%, breaking through the bottleneck that has been difficult to further improve the cycle performance and storage performance of batteries in the past. In addition, the cycle performance and storage performance of the schemes in the above embodiments are improved at the same time, which is of great significance for promoting the research and development of batteries. It can be seen that controlling the A / B of the negative electrode active material is of great significance for further improving the cycle performance and storage performance of the battery.

[0110] Compared with Examples 1 to 8, the value of A / B in Comparative Example 1 is 5.78, and the value of A / B in Comparative Example 2 is 7.3. It can be seen that the cycle capacity retention rate, storage capacity retention rate, and storage capacity recovery rate of the batteries of Examples 1 to 8 are significantly improved compared with Comparative Example 1 and Comparative Example 2, indicating that the value of A / B increases, and the cycle capacity retention rate, storage capacity retention rate, and storage capacity recovery rate of the battery show a trend of first increasing and then decreasing. The difference in the cycle capacity retention rate, storage capacity retention rate, and storage capacity recovery rate of the battery is very obvious when the value of A / B is different. The value of A / B is between 6.0 and 7.2, which is a better range. At this time, the cycle performance and storage performance improvement effect of the battery are very excellent. When the value of A / B exceeds 6.0-7.2, the cycle capacity retention rate, storage capacity retention rate, and storage capacity recovery rate of the battery all decrease.

[0111] By comparing the data of Example 3 and Example 6, it can be seen that the value of the particle size distribution A of Example 6 is 2.019, which exceeds the range of 0.8 to 2.0, and the value of the defectivity B is 0.3, which is within the range of 0.1 to 0.35. The cycle capacity retention rate, storage capacity retention rate and storage capacity recovery rate of the battery also decrease to a certain extent, which proves that the size of the particle size distribution A or the defectivity B also affects the cycle capacity retention rate, storage capacity retention rate and storage capacity recovery rate of the battery to a certain extent. At the same time, controlling the size of A / B, particle size distribution A and defectivity B is beneficial to further improve the cycle capacity retention rate, storage capacity retention rate and storage capacity recovery rate of the battery.

[0112] The above is a detailed introduction to the negative electrode active materials, negative electrode sheets, batteries, battery modules and electrical equipment disclosed in the embodiments of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the negative electrode active materials, negative electrode sheets, batteries, battery modules and electrical equipment of the present invention and their core ideas: At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A negative electrode active material, characterized in that: The particle size distribution of the negative electrode active material is A, and the defectivity is B. The particle size distribution A is (D90-D10) / D50, and the defectivity B of the negative electrode active material is I D / I G , and the ratio of the particle size distribution A to the defect degree B of the negative electrode active material is 6.17≤A / B≤7.2, and the particle size distribution A is 0.8~2.0; The negative electrode active material includes a carbon negative electrode material, and the D50 of the negative electrode active material is 12.0 μm to 18.0 μm.

2. The negative electrode active material according to claim 1, characterized in that: A ratio of the particle size distribution A to the defect degree B of the negative electrode active material is 6.17≤A / B≤6.

91.

3. The negative electrode active material according to any one of claims 1-2, characterized in that: The defect degree B is 0.1~0.

35.

4. The negative electrode active material according to claim 1, wherein: The D90 of the negative electrode active material is 21.0 μm to 32.0 μm, and the D10 of the negative electrode active material is 4.0 μm to 8.5 μm.

5. A negative electrode plate, characterized in that: The invention comprises a current collector and a negative electrode active layer stacked on the current collector, wherein the negative electrode active layer comprises the negative electrode active material according to any one of claims 1 to 4.

6. A battery, characterized in that: include: electrolyte, a positive electrode sheet, wherein the positive electrode sheet is at least partially immersed in the electrolyte; A diaphragm located on one side of the positive electrode plate and at least partially immersed in the electrolyte, and a negative electrode plate according to claim 5, wherein the negative electrode plate is arranged on the side of the diaphragm away from the positive electrode plate and at least partially immersed in the electrolyte.

7. A battery module, characterized in that: Comprising the battery according to claim 6.

8. An electrical device, characterized in that: Comprising the battery module according to claim 7.

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