Negative active layer, negative plate, battery, battery device and electric equipment

Abstract

The invention discloses a negative active layer, a negative plate, a battery, a battery device and electric equipment, the negative active layer comprises natural graphite, the natural graphite satisfies T = Lc / La + I (002) / I (111), and T satisfies 1.1 < = T < = 2.7; wherein Lc is the size of the graphite crystal in the C-axis direction; la is the size of the graphite crystal in the a-axis direction; i (002) is the peak height of a 002 peak of natural graphite in an X-ray diffraction pattern; and I (111) is the peak height of the 111 peak of the natural graphite added with the silicon marker in the X-ray diffraction pattern. According to the negative electrode active layer, the orientation and crystallinity integrity of the natural graphite are limited through Lc / La + I (002) / I (111), the electrochemical expansion of the natural graphite is reduced, the polarization of the battery is reduced, and the structural stability of the natural graphite is improved, so that the consumption of an electrolyte active component and active lithium is reduced, the cycle life of the battery is prolonged, and meanwhile, the service life of the battery is prolonged. And a lithium embedding channel of the natural graphite is additionally arranged, so that the quick charging performance of the battery adopting the natural graphite is favorably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode sheet, in particular to a negative electrode active layer, a negative electrode sheet, a battery, a battery device and an electric equipment. BACKGROUND

[0002] Natural graphite has hexagonal phase structure stacking and rhombohedral phase structure stacking, and has higher specific capacity and initial efficiency than artificial graphite. However, the interlayer spacing of natural graphite is small, and after lithium intercalation, the electrochemical expansion is large, and the rhombohedral phase structure stacking has poor thermodynamic stability. During the charging and discharging process, the graphite expands and shrinks, and is easy to break and expose fresh interface, consume active components and active lithium in the electrolyte to generate new SEI film, thereby affecting the service life of the battery. SUMMARY

[0003] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present application is to provide a negative electrode active layer, which is beneficial to reduce the electrochemical expansion of natural graphite, reduce the polarization of the battery, improve the structural stability of the natural graphite, thereby reducing the consumption of active components and active lithium in the electrolyte, and prolonging the cycle life of the battery.

[0004] According to the negative electrode active layer of the first aspect of the present application, the natural graphite satisfies: T = Lc / La + I(002) / I(111), and the T satisfies: 1.1 ≤ T ≤ 2.7; wherein, Lc is the size of the graphite crystal along the C-axis direction; La is the size of the graphite crystal along the a-axis direction; I(002) is the peak height of the 002 peak of the natural graphite in the X-ray diffraction pattern; I(111) is the peak height of the 111 peak of the natural graphite in the X-ray diffraction pattern.

[0005] According to the negative electrode active layer of the present application, the orientation and crystallinity of the natural graphite are limited by Lc / La + I(002) / I(111), which is beneficial to reduce the electrochemical expansion of the natural graphite, reduce the polarization of the battery, improve the structural stability of the natural graphite, thereby reducing the consumption of active components and active lithium in the electrolyte, and prolonging the cycle life of the battery. At the same time, the lithium intercalation channel of the natural graphite is also increased, which is beneficial to improve the fast charging performance of the battery using the above natural graphite.

[0006] According to some embodiments of the present application, the T further satisfies: 1.3 ≤ T ≤ 2.4.

[0007] According to some embodiments of the present application, the Lc and the La satisfy: 0.6 ≤ Lc / La ≤ 1.2.

[0008] According to some embodiments of the present application, the Lc and the La satisfy: 0.8 ≤ Lc / La ≤ 1.2.

[0009] According to some embodiments of the present application, the Lc satisfies: Lc≥40nm.

[0010] According to some embodiments of the present application, the La satisfies: La=1.84×λ / (FWHM101×cosθ101); and / or, the Lc satisfies: Lc=0.89×λ / (FWHM002×cosθ002); wherein, λ is the wavelength of cathode ray used in X-ray diffraction test; θ101 is half of the diffraction angle corresponding to the diffraction peak of (101) crystal plane in the X-ray diffraction spectrum of the negative electrode active layer; θ002 is half of the diffraction angle corresponding to the diffraction peak of (002) crystal plane in the X-ray diffraction spectrum of the negative electrode active layer; FWHM101 is the half-peak width of the diffraction peak of (101) crystal plane; FWHM002 is the half-peak width of the diffraction peak of (002) crystal plane.

[0011] According to some embodiments of the present application, the I(002) and the I(111) satisfy: 0.5≤I(002) / I(111)≤1.5.

[0012] According to some embodiments of the present application, the I(002) and the I(111) satisfy: 0.5≤I(002) / I(111)≤1.2.

[0013] According to some embodiments of the present application, the graphitization degree of the natural graphite is G, wherein the G satisfies: 96%≤G<100%.

[0014] According to some embodiments of the present application, the calculation formula of the graphitization degree is G=(3.440-2×d004) / (3.440-3.3354)×100%; wherein, 3.440 is the interlayer spacing of completely ungraphitized carbon; 3.3354 is the interlayer spacing of completely graphitized carbon; d004 is the interlayer spacing corresponding to the (004) peak angle of graphite.

[0015] According to some embodiments of the present application, the Dv50 particle size of the natural graphite satisfies: 5μm≤Dv50≤30μm.

[0016] The negative electrode sheet according to the second aspect of the present application comprises: a current collector; and a negative electrode active layer, wherein the negative electrode active layer is the negative electrode active layer according to the first aspect of the present application, and the negative electrode active layer is arranged on at least one side of the current collector in the thickness direction of the current collector.

[0017] The battery according to the third aspect of the present application comprises: the negative electrode sheet according to the second aspect of the present application.

[0018] The battery device according to the fourth aspect of the present application comprises the negative plate according to the second aspect of the present application or the battery according to the third aspect of the present application, and is any one of a battery module and a battery pack.

[0019] The power consumption device according to the fifth aspect of the present application comprises the negative plate according to the second aspect of the present application or the battery according to the third aspect of the present application or the battery device according to the fourth aspect of the present application.

[0020] Additional aspects and advantages of the present application will be made apparent by the following description and the accompanying drawings. DETAILED DESCRIPTION

[0021] The negative active layer according to the first aspect of the present application is described below.

[0022] The negative active layer according to the first aspect of the present application comprises natural graphite, and the natural graphite satisfies T = Lc / La + I(002) / I(111), and T satisfies 1.1 ≤ T ≤ 2.7. wherein Lc is the size of the graphite crystal along the C-axis direction; the unit is nanometer (nm); La is the size of the graphite crystal along the a-axis direction; the unit is nanometer (nm); I(002) is the peak height of the 002 peak of the natural graphite in the X-ray diffraction pattern; the unit is counts per second (cps); I(111) is the peak height of the 111 peak of the natural graphite in the X-ray diffraction pattern; the unit is counts per second (cps).

[0023] For example, T can be any value in 1.1, 1.5, 2.0, 2.3, 2.5, 2.7 or a range formed by any two of them. The crystallographic parameters La, Lc of the natural graphite and the three-dimensional I(002) of the natural graphite can be obtained by testing the material itself of the natural graphite or testing the powder of the negative active layer after stripping the current collector from the negative plate disassembled from the battery.

[0024] The present application adjusts the size ratio of La and Lc of the natural graphite, increases the lithium intercalation channel of the natural graphite, improves the power performance of the natural graphite, shortens the migration path of lithium ions in the natural graphite, improves the fast charging performance of the natural graphite, reduces the polarization of the battery, and reduces the consumption of active components and active lithium of the electrolyte, which is conducive to prolonging the service life of the battery. In addition, the orientation of the natural graphite can be limited, which improves the fast charging capability and reduces the electrochemical expansion of the natural graphite.

[0025] The present application uses I111 / I002 of natural graphite, wherein the silicon standard ratio can be 1:1. The silicon standard model has high strength and is suitable for reflecting the crystallinity of natural graphite. Thus, the crystallinity of natural graphite is measured by using the I111 / I002 peak intensity ratio, and the natural graphite using the feature improves the capacity initial efficiency, and the negative electrode sheet can not contain a silicon-based material, so that the negative electrode sheet does not have the problem of expansion of lithium intercalation of silicon. The present application limits the peak height ratio of the I(002) peak of natural graphite and the added silicon standard (111) peak, limits the crystallinity of natural graphite, improves the migration rate of lithium ions in the graphite, and further reduces the electrochemical expansion of natural graphite.

[0026] According to the negative active layer of the embodiment of the present application, the orientation and crystallinity of natural graphite are limited by Lc / La+I(002) / I(111), which is beneficial to reduce the electrochemical expansion of natural graphite, reduce the battery polarization, improve the structural stability of natural graphite, thereby reduce the consumption of electrolyte active components and active lithium, prolong the cycle life of the battery, and at the same time, the lithium intercalation channel of natural graphite is increased, which is beneficial to improve the fast charging performance of the battery using the above natural graphite.

[0027] According to some embodiments of the present application, T further satisfies: 1.3≤T≤2.4. Exemplarily, T can be any value in 1.3, 1.6, 1.8, 2.0, 2.2, 2.4 or a range composed of any two thereof. When Lc / La+I(002) / I(111) is within the above range, the fast charging performance of natural graphite is relatively optimal, and the electrochemical expansion of natural graphite is effectively reduced, thereby being beneficial to improve the structural stability and reliability of the negative active layer, the negative electrode sheet using the above natural graphite, and prolong the cycle life of the negative electrode sheet and the battery using the above negative electrode sheet.

[0028] According to some embodiments of the present application, T further satisfies: 1.3≤T≤2.4. Exemplarily, T can be any value in 1.3, 1.6, 1.8, 2.0, 2.2, 2.4 or a range composed of any two thereof. When Lc / La+I(002) / I(111) is within the above range, the fast charging performance of natural graphite is relatively optimal, and the electrochemical expansion of natural graphite is effectively reduced, thereby being beneficial to improve the structural stability and reliability of the negative active layer, the negative electrode sheet using the above natural graphite, and prolong the cycle life of the negative electrode sheet and the battery using the above negative electrode sheet.

[0029] Further, when 0.8≤Lc / La≤1.2, the effect is more optimal.

[0030] According to some specific embodiments of the present application, Lc satisfies: Lc≥40nm. Exemplarily, Lc can be any value or a range consisting of any two values selected from 40nm, 45nm, 47nm, 50nm, 60nm, 70nm, 80nm. The above-mentioned limitation on the size of the graphite crystal along the C-axis direction increases the lithium intercalation channel of the natural graphite along the C-axis direction, which is beneficial to improve the fast-charging performance of the natural graphite.

[0031] Further, when Lc≥60nm, the effect is better.

[0032] According to some specific embodiments of the present application, La satisfies: La=1.84×λ(FWHM101×cosθ101); and / or, Lc satisfies: Lc=0.89×λ / (FWHM002×cosθ002); wherein λ is the wavelength of the cathode ray used in the X-ray diffraction test, in nm; θ101 is half of the diffraction angle corresponding to the diffraction peak of the (101) crystal plane in the X-ray diffraction spectrum of the negative electrode active layer, in °; θ002 is half of the diffraction angle corresponding to the diffraction peak of the (002) crystal plane in the X-ray diffraction spectrum of the negative electrode active layer, in °; FWHM101 is the half peak width of the diffraction peak of the (101) crystal plane converted from the angle scale to the radian scale, in rad; FWHM002 is the half peak width of the diffraction peak of the (002) crystal plane converted from the angle scale to the radian scale, in rad.

[0033] The values of La and / or Lc can be accurately calculated by using the above-mentioned corresponding calculation formula based on various data recorded by the X-ray diffraction experiment of the negative electrode active layer. Therefore, the method for obtaining the values of La and Lc is simple and fast, which is beneficial to improve the accuracy of the limitation of La and Lc of the natural graphite, thereby improving the accuracy of the limitation of Lc / La+I(002) / I(111) of the natural graphite, and further improving the fast-charging performance of the negative electrode active layer while reducing the electrochemical expansion of the negative electrode active layer, improving the structural stability of the negative electrode active layer, and prolonging the cycle life of the negative electrode active layer.

[0034] According to some embodiments of the present application, the ratio of I(002) to I(111) satisfies: 0.5≤I(002) / I(111)≤1.5. For example, the ratio of I(002) to I(111) can be any value selected from 0.5, 0.7, 0.9, 1.0, 1.2, 1.5 or a range defined by any two of the values. The above limitation on the ratio of I(111) to I(002) helps to improve the crystalline integrity of the natural graphite, thereby helping to effectively improve the initial efficiency of the battery with the natural graphite, increase the migration rate of lithium ions in the graphite, and reduce the electrochemical expansion of the natural graphite.

[0035] Further, when the ratio of I(002) to I(111) satisfies 0.5≤I(002) / I(111)≤1.2, the effect is even better.

[0036] According to some embodiments of the present application, the graphitization degree of the natural graphite is G, wherein G satisfies: 96%≤G<100%. For example, the graphitization degree of the natural graphite can be any value selected from 96%, 97%, 98%, 99% or a range defined by any two of the values. The graphitization degree of the natural graphite is a core index for measuring the order of its crystal structure, and refers to the perfection degree of the graphite-like crystal structure in the natural graphite (i.e. the regularity of the carbon atom hexagonal ring plane and the order of the interlayer arrangement). The graphitization degree of the natural graphite can be obtained by testing the natural graphite material itself or testing the powder of the negative electrode active layer after stripping from the current collector in the negative electrode sheet disassembled from the battery. The above graphitization degree of the natural graphite is reasonable, the structure density of the natural graphite is high, which helps to reduce the electrochemical expansion of the natural graphite and improve the compaction degree of the negative electrode active layer. In addition, the natural graphite with the above graphitization degree has strong oxidation resistance and corrosion resistance, which helps to improve the service life of the negative electrode active layer.

[0037] Further, the calculation formula of the graphitization degree is G=(3.440-2×d004) / (3.440-3.3354)×100%; wherein 3.440 is the interlayer spacing of completely ungraphitized carbon, with the unit of Å; 3.3354 is the interlayer spacing of completely graphitized carbon, with the unit of Å; d004 is the interlayer spacing Å corresponding to the graphite (004) peak angle.

[0038] The calculation method of the above graphitization degree of the natural graphite has small error, high precision, wide applicability, and is convenient and has small error. In addition, the above calculation method has good reproducibility.

[0039] d004=0.5λ / sin[(56.1-θ1+θ2) / 2]; wherein λ is the wavelength (Å) of the cathode ray used in the X-ray diffraction test; θ1 is the angle corresponding to the silicon marker (311) diffraction peak, in °; θ2 is the angle corresponding to the graphite (004) diffraction peak, in °.

[0040] The interlayer arrangement order of the natural graphite is the core embodiment of the graphitization degree. The 004 crystal face diffraction peak of the graphite is distributed relatively wide, and a large number of points can be collected under the scanning step, and the peak shape is relatively accurate. At the same time, the error range of the above-mentioned method for calculating the interlayer spacing through the graphite (004) peak crystal face diffraction peak is relatively small, the diffraction peak intensity of the above-mentioned (004) peak crystal face is high, the peak shape is symmetrical, and the influence of impurities and grain orientation is small, which is beneficial to reflecting the interlayer ordered structure of the natural graphite crystal. The interlayer spacing corresponding to the graphite (004) peak angle can be accurately and standardized understood through the above-mentioned calculation method.

[0041] According to still some embodiments of the present application, the Dv50 particle size of the natural graphite satisfies: 5 μm≤Dv50≤30 μm. Among them, the Dv50 particle size refers to the particle size value corresponding to the cumulative volume of 50% in the cumulative volume distribution curve of the particle group of the natural graphite. Exemplarily, the Dv50 particle size of the natural graphite can be any value or a range formed by any two values in 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm. The contact area of the above-mentioned particles of the natural graphite is relatively reasonable, the electron transmission path is relatively direct, the surface resistivity is relatively low, which is beneficial to improving the conductivity of the natural graphite, and the ion transmission path of the above-mentioned natural graphite is relatively reasonable, which is beneficial to improving the transmission efficiency of the natural graphite.

[0042] The negative electrode sheet according to the second aspect of the embodiments of the present application comprises: a current collector and a negative electrode active layer, and the negative electrode active layer is the negative electrode active layer according to the first aspect of the embodiments of the present application. The negative electrode active layer is arranged on at least one side of the current collector in the thickness direction of the current collector.

[0043] Among them, the negative electrode active layer can be arranged only on one side of the current collector in the thickness direction of the current collector, or the negative electrode active layer can be arranged on both sides of the current collector in the thickness direction of the current collector. The current collector is responsible for electron transmission and structural support, and the negative electrode active layer is responsible for ion intercalation / deintercalation and energy storage, which together guarantees the charge and discharge efficiency, structural stability and energy density of the battery.

[0044] The negative electrode active layer can comprise natural graphite, a binder, a thickening agent and / or a conductive agent.

[0045] The current collector can be a copper foil, preferably a carbon-coated copper foil.

[0046] The binder, the conductive agent and the thickening agent are not limited.

[0047] The negative plate according to the embodiment of the present application, by adopting the negative active layer, is beneficial to improve the structural integrity of the negative plate, maintain the long-term stability of the three-dimensional structure of the negative plate, reduce the performance decay caused by the damage of the negative plate, and maintain the continuity of the electronic and ionic transmission path, and ensure the stable conductivity and ionic conductivity efficiency of the negative plate.

[0048] The battery according to the third aspect of the embodiment of the present application comprises the negative plate according to the second aspect of the embodiment of the present application.

[0049] The battery according to the embodiment of the present application, by adopting the negative plate, is beneficial to prolong the cycle life of the battery, improve the operation safety and electrochemical stability of the battery, and improve the production consistency and reliability of the battery.

[0050] The battery can comprise a negative plate, a positive plate, a separator and an electrolyte.

[0051] The positive plate comprises a positive active layer and a positive current collector, and the positive active layer can be arranged on one surface or two surfaces of the positive current collector.

[0052] The current collector is preferably an aluminum foil, and further preferably, the current collector is a carbon-coated aluminum foil. The positive active layer comprises one or a combination of several of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and lithium-containing phosphate with olivine structure.

[0053] The separator and the electrolyte are not limited and can be selected according to actual conditions.

[0054] The battery device according to the fourth aspect of the embodiment of the present application comprises the negative plate according to the second aspect of the embodiment of the present application, or the battery according to the third aspect of the embodiment of the present application, and the battery device is any one of a battery module and a battery pack.

[0055] The battery device according to the embodiment of the present application, by adopting the negative plate, is beneficial to improve the cycle stability of the battery, prolong the cycle life of the battery, and thus improve the market competitiveness of the battery.

[0056] The power-consuming device according to the fifth aspect of the embodiment of the present application comprises the negative plate according to the second aspect of the embodiment of the present application, or the battery according to the third aspect of the embodiment of the present application, or the battery device according to the fourth aspect of the embodiment of the present application.

[0057] The power-consuming device can be a vehicle, an aircraft, a ferry, a computer or an energy storage cabinet, which is not limited here.

[0058] According to the power utilization device provided in the embodiments of the present application, the above negative plate, battery or battery device is adopted, so that the energy supply stability of the power utilization device is improved, the user experience is improved, and the market competitiveness of the power utilization device is improved.

[0059] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and should not be construed as limiting the present application. In addition, if not specifically stated, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods, and the reaction conditions not listed are also easily obtained by those skilled in the art.

[0060] Preparation method of battery The natural graphite (the specific parameters of the natural graphite are shown in Table 1), the conductive agent (superP-Li), the thickening agent (CMC) and the binder (SBR) are mixed in a ratio of 96:0.5:1:2 with deionized water to form a slurry, and the slurry is coated on a copper foil by using a coating machine to form a negative active layer, so as to prepare a negative plate.

[0061] The positive active material lithium iron phosphate (LiFePO4), the conductive agent (EP) and the binder (PVDF) are mixed in a ratio of 96:1:3 with NMP, and are coated on an aluminum foil to form a positive active layer, so as to prepare a positive plate.

[0062] A 2Ah laminated battery is prepared in the order of positive plate-separator-negative plate, and the initial efficiency, 4C rate performance, 1C cycle performance and cell expansion thickness of the battery are tested.

[0063] Table 1 Parameters of natural graphite of examples and comparative examples

[0064] Performance test method (1) XRD related test The XRD test is under the conventional condition: copper Kα ray is used as the cathode ray, 40kV and 20mA are used to excite the cathode ray source to generate X rays, the test scanning speed is 5° / min, the scanning step is 0.01°, and the scanning range is 10°-80°; a Kβ filter is used to remove the influence of Kβ ray on the peak shape and peak position of the spectrum; The following test data can be obtained from the natural graphite powder or by disassembling the negative plate of the battery.

[0065] The sample processing of disassembling the battery is as follows: after the secondary battery is completely discharged, the negative electrode sheet is obtained by disassembling; the negative electrode sheet is soaked in a solvent dimethyl carbonate (DMC) for 10 min to 20 min to clean the residual electrolyte, and then the negative electrode sheet is dried. The negative electrode active layer powder is obtained by scraping the negative electrode active layer on one side of the negative electrode current collector with a ceramic scraper (or polishing with sandpaper).

[0066] (2) Test of crystallographic parameters La and Lc of the negative electrode active layer The natural graphite powder or the negative electrode active layer powder obtained according to the method provided above is weighed by using an analytical balance, and then is added into a sample groove and is compressed flat by using a glass sheet. The sample needs to be kept horizontal with the upper surface of the sample groove. The sample is placed into an XRD instrument for testing according to the scanning speed step and the scanning range provided above. The wavelength λ (in nm) of the cathode ray used in the XRD test is recorded. From the obtained XRD spectrum of the negative electrode active layer, the diffraction angle 2θ (in °) of the diffraction peak corresponding to the (101) crystal face of the carbon material and the half-peak width (in rad) of the diffraction peak can be read. The La and Lc of the active material layer are calculated according to the above formula.

[0067] (3) Test of graphitization degree of the negative electrode active layer and I(002) / I(111) The natural graphite powder or the negative electrode active material layer powder obtained according to the method provided above is weighed by using an analytical balance, and then is added into a sample groove and is compressed flat by using a glass sheet. The sample needs to be kept horizontal with the upper surface of the sample groove. The sample is placed into an XRD instrument for testing according to the scanning speed step and the scanning range provided above. The XRD spectrum is obtained. From the obtained XRD spectrum of the negative electrode active layer, the peak position (°) of the diffraction peak corresponding to the (004) crystal face of the carbon material and the peak position (°) of the diffraction peak corresponding to the (311) crystal face of the silicon marker can be read. The graphitization degree of the negative electrode active layer is calculated according to the above formula.

[0068] (4) Test method of Dv50 particle size of natural graphite The test equipment is Mastersizer 3000, the dispersing agent is Triton X-100, and the test method refers to the national standard GB / T 24533-2019.

[0069] (5) Test of initial efficiency of the battery The assembled battery is charged at 25℃ with a charge rate of 0.05C and a cut-off voltage of 4.0V, and the formation capacity is recorded. After aging for 24 hours in an environment at 45℃, the battery is left to stand at room temperature for 2 hours and is discharged at 0.2C to record the capacity. According to the calculation formula: initial efficiency of the battery = capacity × 100% / formation capacity, the initial efficiency of the battery is obtained.

[0070] (6) Charge-discharge capacity test 25℃, charge the battery to 100% SOC state at 0.1C, record the 0.1C charge capacity, stand for 30min, discharge the battery to 0% SOC state at 0.1C, record the 0.1C discharge capacity; then charge the battery to 100% SOC state at 0.1C, discharge the battery to 0% SOC state at 4C, record the 4C discharge capacity. According to the formula: discharge ratio = discharge capacity at 4C rate / 0.1C discharge capacity, calculate the discharge efficiency.

[0071] At 25℃, charge the battery to 100% SOC state at 4C, stand for 30min, according to the formula: charge ratio = charge capacity at 4C rate / 0.1C charge capacity, calculate the charge efficiency.

[0072] (7) Cycle performance test 45℃, charge-discharge at 1C, calculate the capacity retention rate, capacity retention rate = cycle discharge capacity at the nth cycle / cycle discharge capacity at the first cycle, compare the capacity retention rate of the battery at 1000 cycles (8) Electrochemical expansion test Before the cycle test, measure the thickness of the battery, 45℃, charge-discharge at 1C, measure the thickness of the battery after 1000 cycles, electrochemical expansion thickness = thickness of the battery after cycle - thickness of the battery before cycle. Compare the thickness increase of the battery after 1000 cycles.

[0073] The performance test results of the examples and comparative examples are shown in Table 2.

[0074] Table 2 Performance test results of examples and comparative examples

[0075] Test result analysis According to the findings of examples 1-19 and comparative examples 1-4, when the natural graphite satisfies 1.1≤Lc / La+I(002) / I(111)≤2.7, in addition, the electrochemical expansion of the battery using the above natural graphite is small, and the structural stability of the battery is high. In addition, compared with the comparative examples, examples 1-19 have the following improvements: the battery first efficiency is greatly improved, indicating that the initial performance of the battery is relatively stable; the 4C charge ratio and 4C discharge ratio of the battery are both high, indicating that the rapid charge-discharge performance of the battery is good; the 1000 cycle capacity retention rate of the battery is relatively high, indicating that the cycle life of the battery is long.

[0076] Other configurations and operations of the negative electrode sheet, battery, battery device and electric equipment according to the examples of the present application are known to those skilled in the art and will not be described in detail here.

[0077] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily mean the same embodiment or example.

[0078] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, alternatives, and variations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the claims and their equivalents.

Claims

1. A negative electrode active layer characterized by comprising: The natural graphite satisfies: T = Lc / La + I(002) / I(111), and the T satisfies: 1.1 ≤ T ≤ 2.

7. The Lc is the size of the graphite crystal along the C-axis direction. The La is the size of the graphite crystal along the a-axis direction. The I(002) is the peak height of the 002 peak of the natural graphite in the X-ray diffraction pattern. The I(111) is the peak height of the 111 peak of the natural graphite in the X-ray diffraction pattern. The T further satisfies: 1.3 ≤ T ≤ 2.

4.

2. The negative electrode active layer according to claim 1, characterized by The Lc and the La satisfy: 0.6 ≤ Lc / La ≤ 1.

2.

3. The negative electrode active layer according to claim 1, characterized by The Lc and the La satisfy: 0.8 ≤ Lc / La ≤ 1.

2.

4. The negative electrode active layer according to claim 1, characterized by The Lc satisfies: Lc ≥ 40 nm.

5. The negative electrode active layer according to claim 1, characterized by The La satisfies: La = 1.84 × λ(FWHM101 × cosθ101); and / or, 6. The negative electrode active layer according to any one of claims 1 to 5, characterized by, The Lc satisfies: Lc = 0.89 × λ / (FWHM002 × cosθ002); The λ is the wavelength of the cathode ray used in the X-ray diffraction test. The θ101 is half of the diffraction angle corresponding to the diffraction peak of the (101) crystal face in the X-ray diffraction spectrum of the negative electrode active layer. The θ002 is half of the diffraction angle corresponding to the diffraction peak of the (002) crystal face in the X-ray diffraction spectrum of the negative electrode active layer. The FWHM101 is the half peak width of the diffraction peak of the (101) crystal face. The FWHM002 is the half peak width of the diffraction peak of the (002) crystal face. The I(002) and the I(111) satisfy: 0.5 ≤ I(002) / I(111) ≤ 1.

5.

7. The negative electrode active layer according to claim 1, characterized by The I(002) and the I(111) satisfy: 0.5 ≤ I(002) / I(111) ≤ 1.

2.

8. The negative electrode active layer according to claim 1, characterized by The graphitization degree of the natural graphite is G, wherein the G satisfies: 96% ≤ G < 100%.

9. The negative electrode active layer according to claim 1, characterized by The calculation formula of the graphitization degree is G = (3.440 - 2 × d004) / (3.440 - 3.3354) × 100%; 10. The negative electrode active layer according to claim 9, characterized by The 3.440 is the interlayer spacing of completely ungraphitized carbon. The 3.3354 is the interlayer spacing of completely graphitized carbon. The d004 is the interlayer spacing corresponding to the (004) peak angle of graphite. The Dv50 particle size of the natural graphite satisfies: 5 μm ≤ Dv50 ≤ 30 μm.

11. The negative electrode active layer according to claim 1, characterized by The negative electrode active layer according to any one of claims 1-11 is provided on at least one side in the thickness direction of the current collector.

12. A negative electrode sheet characterized by comprising: The negative electrode sheet according to claim 12. The negative electrode sheet according to claim 12; or the battery device according to claim 13, which is any one of a battery module and a battery pack. The negative electrode sheet according to claim 12, or the battery according to claim 13; 13. A battery, characterized by Or the battery device according to claim 14. ​ 14. A battery device characterized by comprising: ​ ​ 15. An electrical device, comprising: ​ ​ ​

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