Negative electrode sheet and preparation method therefor, lithium-ion battery and electric equipment

Abstract

A negative electrode sheet, comprising an active material, wherein the active material comprises graphite. The negative electrode sheet satisfies: 0.4<λ<1600, wherein [Equation 1], [Equation 2], where C is the sphericity of the active material; ρ is the tap density of the active material, with the unit thereof being g / cm3; S2 is the specific surface area of the active material, with the unit thereof being m2 / g; D50 is the value of the median particle size D50 of the active material, with the unit thereof being μm; and [Equation 3], D is the orientation value of the negative electrode sheet, I110 is the peak intensity of peak 110 in an XRD pattern of the negative electrode sheet, and I004 is the peak intensity of peak 004 in the XRD pattern of the negative electrode sheet.

Description

Negative electrode sheet, preparation method thereof, lithium ion battery and electric device

[0001] The present application claims priority to the Chinese patent application No. 202410458423.1, filed on April 16, 2024, entitled "Negative electrode sheet, preparation method thereof, lithium ion battery and electric device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of secondary batteries, in particular to a negative electrode sheet, a preparation method thereof, a lithium ion battery and an electric device. BACKGROUND

[0003] Graphite materials are widely used in battery anodes due to their low cost and high energy density. However, as user demands continue to increase, more and more electronic products need to achieve fast charging and long cycle life functions, which requires research and improvement of the batteries in electronic products. However, the existing battery anodes are limited by the fast charging kinetics at the level of electrode sheets and materials, and the fast charging performance and cycle life of the battery are poor. SUMMARY

[0004] The purpose of the present application is to overcome the problems of difficulty in large-rate charging and poor cycle life of secondary batteries in the prior art, and to provide a negative electrode sheet, a preparation method thereof and applications and a lithium ion battery. The secondary battery prepared by using the negative electrode sheet has the advantages of excellent fast charging performance and cycle performance.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a negative electrode sheet, which satisfies the empirical formula 0.4 < λ < 1600; wherein k is a correction coefficient, k is defined as 100;

[0006] C is the sphericity of the active material; p is the tap density of the active material, unit: g / cm 3 ; S2 is the specific surface area of the active material, unit: m 2 / g; D 50 is the median particle size D 50 value of the active material, unit: μm;

[0007] 0.06 ≤ D < 200; D is the orientation value of the negative electrode sheet, I 110 is the peak intensity of the 110 peak in the XRD pattern of the negative electrode sheet, I 004 is the peak intensity of the 004 peak in the XRD pattern of the negative electrode sheet.

[0008] The second aspect of the application provides a preparation method of a negative electrode sheet, the method comprising:

[0009] (1) preparing a negative electrode active material containing graphite into a slurry, coating on a current collector to form a primary electrode sheet;

[0010] (2) applying a magnetic field and / or an electric field to the primary electrode sheet, drying and rolling to obtain the negative electrode sheet;

[0011] wherein the negative electrode sheet satisfies 0.4 < λ < 1600;

[0012] C is the sphericity of the active material; p is the tap density of the active material, in g / cm 3 ; S2 is the specific surface area of the active material, in m 2 / g; D 50 is the median particle size D 50 value of the active material, in μm;

[0013] 0.06 ≤ D < 200; D is the orientation value of the negative electrode sheet, I 110 is the peak intensity of the 110 peak in the XRD pattern of the negative electrode sheet, I 004 is the peak intensity of the 004 peak in the XRD pattern of the negative electrode sheet.

[0014] The third aspect of the application provides a negative electrode sheet prepared by the preparation method described in the application.

[0015] The fourth aspect of the application provides a lithium ion battery, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode sheet described in the application.

[0016] The fifth aspect of the application provides an electrical equipment comprising the lithium ion battery described in the application.

[0017] Through the above technical solution, the negative electrode sheet described in the application has excellent ion diffusion capacity, good fast charging performance and cycle performance of the secondary battery. The secondary battery (for example, a lithium ion battery) prepared by using the negative electrode sheet described in the application has excellent fast charging performance, and at the same time, meets the demand for long cycle life of the battery.

[0018] The preparation method described in the application controls the sphericity (C) of the active material particles in the negative electrode sheet, and controls the arrangement direction of the crystal structure of the active material in the negative electrode sheet by magnetic-electric induction orientation, changes the orientation degree (D) of the negative electrode sheet, so that the sphericity C of the active particles of the negative electrode sheet and the orientation degree D of the negative electrode sheet satisfy , thereby obtaining a negative electrode sheet with excellent fast charging and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a scanning electron microscope (SEM) image of the negative electrode sheet before the crystal structure is oriented and aligned by applying a magnetic field and an electric field to the negative electrode sheet in Example 1;

[0020] FIG2 is a scanning electron microscope (SEM) image of the negative electrode sheet after the crystal structure is oriented and aligned by applying a magnetic field and an electric field to the negative electrode sheet in Example 1;

[0021] FIG3 is an XRD diagram of the negative electrode before and after applying a magnetic field and an electric field to the electrode to induce directional alignment of the crystal structure in Example 1. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] In this application, the parameters and their test methods are as follows:

[0024] D 50 Refers to the median particle size of the particles, obtained by analysis using a laser force tester.

[0025] The actual specific surface area value S2 of the particles is obtained by analyzing the specific surface area tester. The active material is sampled and analyzed, and the median average value is taken.

[0026] The orientation value D of the crystal structure of the negative electrode can be measured by X-ray diffractometer XRD. 110 is the peak intensity of 110 peak in the XRD pattern of the negative electrode, I 004 The peak intensity of the 004 peak in the XRD pattern of the negative electrode sheet is used to calculate the D value (OI value) of the negative electrode sheet to be I 004 / I 110 , which can characterize the verticality of the active material in the negative electrode. The smaller the D value, the higher the verticality, which is more conducive to the fast charging performance of the electrode.

[0027] In this application, the structure of the negative electrode sheet was characterized using a D / MAX-2500 X-ray diffractometer manufactured by Rigaku Corporation of Japan to obtain an XRD pattern. Cu-Ka radiation (wavelength = 0.15406 nm) was used, with a current of 100 mA and a voltage of 40 kV. The scanning range was 2θ = 5-80°, and the scanning rate was 5° / min.

[0028] The first aspect of the present application provides a negative electrode sheet, which satisfies the empirical formula 0.4 < λ < 1600; wherein k is a correction coefficient, k is defined as 100;

[0029] C is the sphericity of the active material; p is the tap density of the active material, in g / cm 3 ; S2 is the specific surface area of the active material, in m 2 / g; D 50 is the median particle size D 50 value of the active material, in μm;

[0030] 0.06 ≤ D < 200; D is the orientation value of the negative electrode sheet, I 110 I is the peak intensity of the 110 peak in the XRD pattern of the negative electrode sheet, I 004 I is the peak intensity of the 004 peak in the XRD pattern of the negative electrode sheet. The negative electrode sheet described in the present application has excellent resistivity, peel strength, ion diffusion capacity, etc., and the prepared secondary battery has more excellent fast charging performance and cycle life.

[0031] In the present application, in the range of 0.4 < λ < 1600, the fast charging capacity of the secondary battery can be improved, and the optional range of λ value is wide, for example, it can be 0.5, 1, 50, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1500, 1590, according to one preferred embodiment of the present application, 4 < λ < 1600, further preferably 20 < λ < 1600, more preferably 100 ≤ λ ≤ 900; in the foregoing range, the prepared secondary battery has more excellent fast charging performance and cycle life.

[0032] In the present application, the optional range of C is wide, for example, C can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.98; according to one preferred embodiment of the present application, 0.04 < C < 0.96, preferably 0.4 ≤ C ≤ 0.93; in the foregoing range, the prepared secondary battery has more excellent fast charging performance and cycle life.

[0033] In the present application, D can be selected from a wide range, for example, D can be 0.06, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 5, 10, 20, 30, 40, 50, 80, 100, 120, 150, 180, 200; according to one preferred embodiment of the present application, 0.06≤D<10, further preferably 0.06≤D<1, more preferably 0.06≤D<0.2; within the aforementioned range, the prepared secondary battery has more excellent fast charging performance and cycle life.

[0034] According to one preferred embodiment of the present application, the specific surface area S2 of the active material is 0.6-30m 2 / g; preferably 8-25m 2 / g.

[0035] According to one preferred embodiment of the present application, D 50 of the active material is 1μm-300μm; preferably 5μm-30μm.

[0036] According to one preferred embodiment of the present application, the tap density ρ of the active material is 0.6-1.7g / cm 3 , preferably 0.6-1.55g / cm 3 .

[0037] According to one preferred embodiment of the present application, the single-sided area density of the negative electrode sheet is 40-300g / m 2 ; preferably 75-200g / m 2 . Generally, the single-sided area density of the electrode sheet is calculated when the slurry is coated on one side of the current collector; the double-sided area density of the electrode sheet is calculated when the slurry is coated on both sides of the current collector.

[0038] In the present application, taking the negative electrode sheet coated with negative electrode active material on both sides as an example, the double-sided density of the negative electrode sheet is 160-600g / m 2 ; preferably 200-500g / m 2 . In the examples of the present application, the double-sided area density of 230g / m 2 is mainly taken as an exemplary illustration of the advantages of the present application, but does not limit the scope of the present application.

[0039] According to one preferred embodiment of the present application, the active material further comprises one or more of titanium oxide, silicon-carbon composite and tin-based composite.

[0040] In the present application, the type of graphite can be selected from a wide range, according to one preferred embodiment of the present application, the graphite is natural graphite and / or artificial graphite.

[0041] The second aspect of the application provides a preparation method of a negative electrode sheet, the method comprising:

[0042] (1) preparing a negative electrode active material containing graphite into a slurry, coating on a current collector to form a primary electrode sheet;

[0043] (2) applying a magnetic field and / or an electric field to the primary electrode sheet, drying and rolling to obtain the negative electrode sheet;

[0044] wherein the negative electrode sheet satisfies 0.4 < λ < 1600;

[0045] C is the sphericity of the active material; p is the tap density of the active material, in g / cm 3 ; S2 is the specific surface area of the active material, in m 2 / g; D 50 is the median particle size D 50 value of the active material, in μm;

[0046] 0.06 ≤ D < 200; D is the orientation value of the negative electrode sheet, I 110 is the peak intensity of the 110 peak in the XRD pattern of the negative electrode sheet, I 004 is the peak intensity of the 004 peak in the XRD pattern of the negative electrode sheet.

[0047] The preparation method described in the application controls the sphericity (C) of the active material particles in the negative electrode sheet, and controls the arrangement direction of the crystal structure of the active material in the negative electrode sheet by magnetic-electric induction orientation, changes the orientation degree (D) of the negative electrode sheet, so that the sphericity C of the active particles of the negative electrode sheet and the orientation degree D of the negative electrode sheet satisfy so as to obtain a negative electrode sheet with excellent fast charging and cycling performance.

[0048] The preparation method described in the application controls the sphericity of the particles by controlling the tap density, specific surface area, particle size range, etc. of the active material. In the application, C is the sphericity of the active material in the electrode sheet, which is calculated by the values of the equivalent spherical specific surface area S1 of the active material and the actual specific surface area S2 of the active material; wherein,

[0049] The volume equivalent diameter of the active material is R1, R1 = 1 / 2D 50 ;

[0050] In the present application, the active material is modified by using the means of magnetic field and electric field induced crystal structure orientation, and then the negative electrode sheet with ordered stacking of crystal structure is prepared through rolling process, so that the battery performance under high surface density and compaction condition can be played favorably, and great effect can be played.

[0051] According to a preferred embodiment of the present application, the orientation of the electrode sheet is induced by applying magnetic field and electric field to the electrode sheet, and the ratio of I 110 and I 004 is adjusted; according to a preferred embodiment of the present application, the strength of the magnetic field is 0.1T-2T; the voltage of the electric field is 0.1V-120V. The voltage of the electric field refers to that the electric field is generated by applying voltage to the current collector, and the size of the electric field is adjusted by adjusting the voltage.

[0052] According to an embodiment of the present application, the orientation of the electrode sheet is induced by applying magnetic field and electric field to the electrode sheet, and the ratio of I 400 and I 110 is adjusted; according to a preferred embodiment of the present application, the strength of the magnetic field is 0.1T-2T; the voltage of the electric field is 0.1V-120V. The voltage of the electric field refers to that the electric field is generated by applying voltage to the current collector, and the size of the electric field is adjusted by adjusting the voltage.

[0053] In the present application, the relative direction between the magnetic field and the electrode sheet during the process of applying the magnetic field is not particularly limited, for example, the relative direction between the magnetic field and the current collector can be set as parallel, vertical, or any angle between parallel and vertical, and the relative angle between the magnetic field and the current collector includes but is not limited to 1°, 5°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 85°.

[0054] In the present application, the drying condition can be selected in a wide range, according to a preferred embodiment of the present application, the drying condition includes that the temperature is 60-145℃.

[0055] In the present application, the rolling condition can be selected in a wide range, according to a preferred embodiment of the present application, the rolling condition includes that the pressure is 1-20T.

[0056] According to a preferred embodiment of the present application, in the above preparation method, C can be selected in a wide range, for example, C can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.98; according to a preferred embodiment of the present application, 0.04

[0057] According to a preferred embodiment of the present application, in the above preparation method, D can be selected from a wide range, for example, D can be 0.06, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 5, 10, 20, 30, 40, 50, 80, 100, 120, 150, 180, 200; according to a preferred embodiment of the present application, 0.06≤D<10, further preferably 0.06≤D<1, more preferably 0.06≤D<0.2.

[0058] In the preparation method described in the present application, in the range of 0.4<λ<1600, the fast charging capability of the secondary battery can be improved, and the value of λ can be selected from a wide range, for example, λ can be 0.5, 1, 50, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1500, 1590; according to a preferred embodiment of the present application, 4<λ<1600, further preferably 20<λ<1600, more preferably 100≤λ≤900.

[0059] According to a preferred embodiment of the present application, in step (1), the specific surface area S2 of the active material is 0.6-30m 2 / g, preferably 8-25m 2 / g.

[0060] According to a preferred embodiment of the present application, in step (1), the active material D 50 is 1μm-300μm, preferably 5μm-30μm.

[0061] According to a preferred embodiment of the present application, in step (1), the tap density ρ of the active material is 0.6-1.7g / cm 3 , preferably 0.6-1.55g / cm 3 .

[0062] According to a preferred embodiment of the present application, in step (2), after adjusting the D value of the primary electrode sheet, the primary electrode sheet is further rolled to adjust the area density of the negative electrode sheet; according to a preferred embodiment of the present application, the double-sided area density of the negative electrode sheet is 160-600g / m 2 ; preferably 200-500g / m 2 .

[0063] The preparation method described in the present application can be applied to most types of negative electrode sheet materials at present, and has excellent technical popularization; according to a preferred embodiment of the present application, the active material further comprises one or more of titanium oxide, silicon-carbon composite, tin-based composite, hard carbon and soft carbon.

[0064] In the present application, the type of graphite is not particularly limited, and the graphite materials used in the art can achieve the purpose of the present application, for example, including but not limited to artificial graphite, natural graphite and the like.

[0065] In the present application, in step (1), the method for preparing the electrode sheet is a conventional method in the art, for example, dispersing the active material selected in step (1) and optionally an additive into a solvent to obtain a slurry; coating the slurry onto a current collector to form a primary electrode sheet.

[0066] In the present application, the type of the additive is not particularly limited, and the conventional additives in the art are suitable for the present application, according to a preferred embodiment of the present application, the additive is selected from one or more of conductive agents, binders and stabilizers. In the embodiments of the present application, the negative active material containing graphite also contains conductive agents, binders and stabilizers as exemplary description of the advantages of the present application, but this does not limit the scope of the present application.

[0067] In the present application, the ratio of the amount of active material to additive is not particularly limited and can be determined according to conventional technical means in the art.

[0068] In the present application, the type and amount of solvent are not particularly limited and can be determined according to conventional technical means in the art.

[0069] In the preparation of the electrode sheet, the current collector can be coated on both sides or on one side, when the current collector is coated on both sides, each parameter (such as the orientation value D) is determined for a single-sided electrode sheet.

[0070] The third aspect of the present application provides a negative electrode sheet prepared by the preparation method described in the present application.

[0071] The negative electrode sheet described in the present application or prepared according to the preparation method of the present application can be applied to various secondary batteries, and the structure and preparation method of these secondary batteries are known per se.

[0072] Generally, a secondary battery mainly consists of a negative electrode sheet, a positive electrode sheet, a separator and an electrolyte. The positive and negative electrode sheets are immersed in the electrolyte, and the active ions move between the positive and negative electrodes with the electrolyte as the medium, realizing the charging and discharging of the battery. In order to avoid short circuit between the positive and negative electrodes through the electrolyte, a separator is needed to separate the positive and negative electrodes. The form of the secondary battery can be, for example, a square or cylindrical hard shell outer package (such as aluminum shell material), or a soft package (such as aluminum plastic film material).

[0073] The secondary battery can be a lithium ion battery, a sodium ion battery, etc. Preferably, the negative electrode sheet according to the present application or prepared by the method according to the present application is particularly suitable for the electrode sheet of a lithium ion secondary battery, and particularly suitable for the negative electrode sheet of a lithium ion secondary battery.

[0074] In the secondary battery according to the present application, the specific type and composition of the separator and the electrolyte are not specifically limited, and can be selected according to actual needs.

[0075] The fourth aspect of the present application provides a lithium ion battery, comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode sheet according to the present application.

[0076] In the lithium ion battery according to the present application, the specific type and composition of the separator and the electrolyte are not specifically limited, and can be selected according to actual needs.

[0077] The fifth aspect of the present application provides a power consumption device comprising the lithium ion battery according to the present application.

[0078] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations on the claims of the present application.

[0079] In order to more clearly illustrate the present application, the following examples are listed with graphite as the negative electrode active material and lithium iron phosphate (LFP) as the positive electrode active material, but the implementation of the present application is not limited to the scope of the examples.

[0080] Example 1

[0081] (1) Preparation of the negative electrode sheet:

[0082] At room temperature 25℃, according to the mass ratio 100:1:3.5:1.5, the artificial graphite, conductive agent (carbon black), binder (SBR), stabilizer (CMC) and water are stirred uniformly to make slurry, then coated on the copper foil by coating equipment and baked, at the same time, a 25V voltage and a 0.8T magnetic field are applied to the current collector copper foil for magnetic-electric induced crystal structure directional arrangement, the magnetic field is kept uniform and stable, then normal baking is started, then the above negative electrode is rolled to prepare a double-sided density of 230g / m 2 The tap density p, specific surface area S2, D 50 value of the graphite particles, and the structure orientation value of the negative electrode sheet, thereby preparing a graphite negative electrode sheet with a λ value, see Table 1.

[0083] (2) Positive electrode tab preparation: under the condition of room temperature 25℃, according to the mass ratio of 100:1:4, LFP, conductive agent (carbon black), binder (PVDF) and solvent (NMP) are stirred uniformly to prepare slurry, then coated on aluminum foil by coating equipment, and then baked. The above negative electrode is cut to prepare a lithium iron phosphate positive electrode tab with a double-sided area density of 500 g / m 2 .

[0084] (3) In an argon-filled glove box, 1 mol of lithium salt LiPF6 is dissolved in 1 L of organic solvent (volume ratio of ethylene carbonate and diethyl carbonate is 1:1) to obtain an electrolyte;

[0085] (4) In the glove box, under Ar gas atmosphere, the positive electrode tab prepared in step 1), the separator (PP), and the negative electrode tab are alternately stacked, and the electrolyte is injected to prepare a soft pack battery. The battery design capacity is 1.8 Ah;

[0086] The scanning electron microscope (SEM) image of the graphite before the crystal structure is directionally arranged by applying a magnetic field and an electric field to the negative electrode tab is shown in Figure 1; the scanning electron microscope (SEM) image of the graphite after the crystal structure is directionally arranged by applying a magnetic field and an electric field to the negative electrode tab is shown in Figure 2; the XRD image of the graphite before and after the crystal structure is directionally arranged by applying a magnetic field and an electric field to the tab is shown in Figure 3.

[0087] Examples 2-8

[0088] The same as example 1, the active material type, tap density, specific surface area, and D50 are kept unchanged in terms of material selection, except that the gradient adjustment of the magnetic field strength and the voltage size is different, so as to realize different D values, and thus the λ value of the negative electrode tab is made, as shown in Table 1.

[0089] Examples 9-10

[0090] The same as example 1, except that the C value is adjusted by selecting a suitable negative electrode active material, and then the D value is adjusted by selecting a suitable voltage size and magnetic field strength, so as to make the λ value of the negative electrode tab, as shown in Table 1.

[0091] Examples 11-16

[0092] The same as example 1, except that the C value is adjusted by selecting a suitable negative electrode active material, and then the D value is adjusted by selecting a suitable voltage size and magnetic field strength, so as to make the λ value of the negative electrode tab, as shown in Table 1.

[0093] Examples 17-19

[0094] The same as example 1, by increasing the coating amount of the active material in the negative electrode tab, the different area densities of the negative electrode active material layer are adjusted, as shown in Table 1.

[0095] Comparative Example 1

[0096] The same as Example 1, except that the parameters of the graphite active material were adjusted; at the same time, the magnetic field strength was set to 0.1 T, the electric field voltage was 0.1 V, the magnetic field direction was parallel to the current collector direction, and the specific parameters are shown in Table 1.

[0097] Comparative Example 2

[0098] The same as Example 1, except that a material with a sphericity of more than 0.96 was selected and an electric field and a magnetic field were set for orientation, and the specific parameters are shown in Table 1.

[0099] Comparative Example 3

[0100] The same as Example 1, except that only a magnetic field was used for orientation, and the specific parameters are shown in Table 1.

[0101] Comparative Example 4

[0102] The same as Example 1, except that the parameters of the graphite active material were adjusted; at the same time, the magnetic field strength was set to 0.3 T, the electric field voltage was 0.5 V, and the magnetic field direction was perpendicular to the current collector direction; and the specific parameters are shown in Table 1.

[0103] Table 1

[0104] Table 1 (continued)

[0105] In Table 1, the magnetic field direction refers to the relationship with the setting direction of the current collector, for example, the magnetic field direction perpendicular means that the current collector is perpendicular to the direction of the magnetic field.

[0106] Test Example, the batteries prepared in Examples 1-19 and Comparative Examples 1-4 were tested, and the results of the resistivity test, discharge rate, and cycle capacity retention rate are shown in Table 2.

[0107] Resistivity test: four-probe method was used to test the resistivity of the negative electrode sheet.

[0108] Discharge specific capacity ratio: at 25°C, the change of discharge gram capacity of each battery at different rates such as 0.2C, 5C, etc. with cycle number was tested, and the voltage range was 2.0-3.8V. The ratio of the first cycle discharge capacity at 5C rate to the first cycle discharge capacity at 0.2C was calculated.

[0109] Cycle life test: at 25°C, the change of discharge gram capacity of each battery at 0.2C / 2C rate with cycle number was tested, and the voltage range was 2.0-3.8V.

[0110] Table 2

[0111] From the 5C discharge conditions of Comparative Example 1, Comparative Example 3 and Comparative Example 4, it can be seen that when λ is less than 0.4, the rate performance will have a significant decrease, which is due to the fact that the particles with low sphericity have a high degree of arrangement parallel to the current collector, which significantly hinders the diffusion of lithium ions. From the cycle retention of Comparative Example 2, it can be seen that when λ is greater than 1600, the cycle performance will have a significant decrease, which is due to the fact that the particles with high sphericity have a high degree of arrangement perpendicular to the current collector, which causes the contact between the particles to deteriorate, the side reactions to increase, and the electronic conduction to be easily affected during the repeated charge and discharge process, thereby causing the cycle performance to have a significant decrease.

[0112] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A negative electrode sheet characterized by comprising: The negative electrode sheet includes an active material; the active material includes graphite; the negative electrode sheet satisfies 0.4 < λ < 1600; wherein, C is the sphericity of the active material; p is the tap density of the active material in g / cm 3 ; S2 is the specific surface area of the active material in m 2 / g; D 50 is the median particle diameter D 50 value of the active material in pm; 0.06≤D＜200； D is the orientation value of the negative electrode sheet, I 110 I is the peak intensity of the 110 peak in the XRD pattern of the negative electrode sheet 004 I is the peak intensity of the 004 peak in the XRD pattern of the negative electrode sheet 2. The negative electrode sheet according to claim 1, wherein 20 < λ < 1600, preferably 100 < λ < 900; and / or 0.04 < C < 0.96; and / or 0.06 < D < 10; preferably 0.06 < D < 1.

3. The negative electrode sheet according to claim 1 or 2, wherein The specific surface area S2 of the active material is 0.6-30 m 2 / g; and / or D 50 is 1 μm to 300 μm; and / or tap density p is 0.6-1.7 g / cm3 3 .

4. The negative electrode sheet according to claim 1 or 2, wherein The double-sided area density of the negative electrode sheet is 160-600 g / m 2 ; preferably 200-500 g / m 2 .

5. The negative electrode sheet according to claim 1 or 2, wherein the active material further comprises one or more of titanium oxide, silicon-carbon composite, tin-based composite, hard carbon and soft carbon; and / or the graphite is natural graphite and / or artificial graphite.

6. A method for producing a negative electrode sheet, characterized by The method comprises: (1) preparing a negative electrode active material comprising graphite into a slurry, coating on a current collector to form a primary electrode sheet; (2) applying a magnetic field and / or an electric field to the primary electrode sheet, drying and rolling to obtain the negative electrode sheet; The negative electrode sheet satisfies 0.4 < λ < 1600. C is the sphericity of the active material; p is the tap density of the active material in g / cm 3 ; S2 is the specific surface area of the active material in m 2 / g; D 50 is the median particle diameter D 50 value of the active material in pm; 0.06≤D＜200； D is an orientation value of the negative electrode sheet, I 110 I is a peak intensity of the 110 peak in the XRD pattern of the negative electrode sheet 004 I is a peak intensity of the 004 peak in the XRD pattern of the negative electrode sheet 7. The preparation method according to claim 6, wherein in step (2), the strength of the magnetic field is 0.1 T-2 T; the voltage of the electric field is 0.1 V-120 V; and / or the drying condition comprises: temperature is 60-145 °C; and / or the rolling condition comprises: pressure is 1-20 T.

8. The preparation method according to claim 6 or 7, wherein in step (1), The specific surface area S2 of the active material is 0.6-30 m 2 / g; and / or The active material D 50 from 1 μm to 300 μm; and / or The active material tap density p is 0.6-1.7 / cm 3 .

9. The preparation method according to claim 6 or 7, wherein the active material further comprises one or more of titanium oxide, silicon-carbon composite, tin-based composite, hard carbon and soft carbon; and / or the graphite is natural graphite and / or artificial graphite.

10. The preparation method according to claim 6 or 7, wherein The double-sided area density of the negative electrode sheet is 160-600 g / m 2 ; preferably 200-500 g / m 2 .

11. A negative electrode sheet prepared by the preparation method according to any one of claims 6-10.

12. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, characterized in that, The negative electrode is the negative electrode sheet according to any one of claims 1-5, 11.

13. An electrical device comprising the lithium ion battery according to claim 12.

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