Association characterization method for heat production and Li < + > / Ni < 2 + > mixed arrangement in ternary lithium battery high-temperature cycle process
By constructing a linkage characterization of Li+/Ni2+ mixing degree, lithium-ion diffusion coefficient and heat generation/heat generation power, the problems of capacity decay and safety hazards during high-temperature cycling of ternary lithium batteries are solved, providing scientific data support and modification directions, which are applicable to thermal management optimization of electric vehicles and energy storage systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YANTAI VOCATIONAL COLLEGE
- Filing Date
- 2026-03-27
- Publication Date
- 2026-05-05
AI Technical Summary
Existing technologies have failed to establish a linkage analysis system for the degree of Li+/Ni2+ mixing, lithium-ion diffusion, and heat generation in ternary lithium batteries, thus failing to provide accurate intrinsic correlation data for battery thermal management. This results in capacity decay and safety hazards in ternary lithium batteries during high-temperature cycling.
Through multi-dimensional characterization tests, the correspondence between the degree of Li+/Ni2+ mixing, the lithium-ion diffusion coefficient of ternary lithium batteries, and the heat generation/heat generation power was constructed. XRD was used to test the crystal phase diffraction peak intensity ratio I003/I104. Combined with the LAND-CT2001A battery testing system and an eight-channel isothermal calorimeter, the lithium-ion diffusion coefficient and heat flow parameters were measured, heat flow curves were plotted, and the heat generation and heat generation power were derived.
This study reveals the intrinsic mechanism of Li+/Ni2+ mixing on lithium-ion diffusion and heat generation, providing scientific data support for high-temperature cycling thermal management strategies for ternary lithium batteries. It clarifies the direction of material modification, reduces the rate of heat generation increase, and is applicable to the NCM811 material system and other cathode materials with cation mixing problems, thus optimizing thermal management strategies for electric vehicles and energy storage systems.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of ternary lithium battery technology, and particularly relates to a method for heat generation and Li during high-temperature cycling of ternary lithium batteries. + / Ni 2+ A method for representing the association of mixed-row structures. Background Technology
[0002] With the widespread application of lithium-ion batteries in electric vehicles and energy storage systems, their safety has become an increasing concern. Heat generation during the charging and discharging process is a key factor affecting the safety performance of lithium-ion batteries. Research indicates that, in addition to external factors, the inherent properties of the electrode materials are the main factors influencing heat generation in lithium-ion batteries. In ternary lithium batteries, NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (O2) is widely used due to its high energy density. However, NCM811 suffers from rapid capacity decay and poor safety during use. Studies have shown that the electrochemical performance of ternary lithium batteries is closely related to the changes in the crystal structure of the NCM811 cathode material during charging and discharging.
[0003] Due to Li + (7.6 Å) and Ni 2+ With ionic radii similar to those of (6.9 Å), Ni exhibits similar radii during charge and discharge. 2+ It will migrate from the transition metal layer to the lithium layer, causing Li + / Ni 2+ Mixed arrangement. Li + / Ni 2+ Mixing can lead to the occupation of active lithium sites, thus affecting lithium-ion diffusion within the NCM811 cathode material. This results in capacity decay and reduced rate performance in ternary lithium batteries, and can cause safety issues after multiple cycles. This is especially true under high-temperature conditions in the NCM811 cathode material. + / Ni 2+ The problem of mixed sorting is even more serious.
[0004] Current technologies lack a comprehensive analytical framework linking "mixing degree - lithium-ion diffusion - heat generation," thus failing to provide accurate intrinsic correlation data for battery thermal management. Therefore, there is an urgent need to develop a scientific and reproducible correlation characterization method to quantify the relationship between these three factors. Summary of the Invention
[0005] In view of this, the purpose of this invention is to provide a method for heat generation and Li during high-temperature cycling of a ternary lithium battery. + / Ni 2 + The correlation characterization method of mixed arrangement, through multi-dimensional characterization tests, constructs the NCM811 cathode material Li in ternary lithium batteries.+ / Ni 2+ The correlation between the degree of mixing, the lithium-ion diffusion coefficient of ternary lithium batteries, and the heat generation / heat power of ternary lithium batteries reveals the relationship between Li... + / Ni 2+ The mixing mechanism regulates heat generation by influencing lithium-ion diffusion, providing a reliable characterization method and data support for the formulation of high-temperature cycling thermal management strategies and the optimization of safety performance of ternary lithium batteries.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A ternary lithium battery generates heat during high-temperature cycling and Li + / Ni 2+ The association representation method for mixed-row structures includes the following steps: S1: Assemble ternary lithium batteries and perform charge-discharge cycles; S2: XRD was used to characterize the crystallization state of the ternary lithium battery cathode material during cycling. TOPAS software was used to identify the peak positions and analyze the intensity of the diffraction peaks of the crystal phases. The intensity ratio of the diffraction peaks of the (003) and (104) crystal planes was calculated and denoted as I. 003 / I 104 ; S3: The specific capacity Q and lithium-ion diffusion coefficient D of ternary lithium batteries at 1C charge-discharge rates between 2.8 and 4.3 V were measured using the LAND-CT2001A battery testing system; at the same time, the heat flow parameters of ternary lithium batteries at 50℃ were measured using an eight-channel isothermal calorimeter connected to the LAND-CT2001A battery testing system, and heat flow curves at different cycle numbers were plotted. S4: Based on the heat flow curve plotted in S3, the heat generation and heat generation power are derived.
[0007] Preferably, in step S1, the ternary lithium battery comprises: Positive electrode: NCM811 material; Conductive agent: Acetylene black; Adhesive: Polyvinylidene fluoride; Solvent: 1-Methyl-2-pyrrolidone; Anode: Lithium foil material; Electrolyte: ethylene carbonate / ethyl methyl carbonate / dimethyl carbonate, wherein the volume ratio of ethylene carbonate:ethyl methyl carbonate:dimethyl carbonate in the electrolyte is 1:1:1; the electrolyte contains 1M LiPF6. Current collector: Aluminum foil; Diaphragm: Celgard 2325.
[0008] Preferably, in step S1, the number of charge-discharge cycles is 60 to 210.
[0009] Preferably, in step S2, the XRD is performed using a D8 ADVANCE Da Vinci type X-ray diffractometer.
[0010] Preferably, in step S2, the XRD test uses a Cu target, Kα radiation, and a wavelength λ = 1.55 Å.
[0011] Preferably, in step S2, the XRD test scanning mode is θ-θ continuous scanning, the scanning range is 2θ=10°~90°, and the scanning speed is 2° / min.
[0012] Preferably, in step S2, the positive electrode is a circular electrode sheet, and the thickness of the active material NCM81 on the positive electrode is 40 μm, with an areal density of 3.5 mg / cm². -2 .
[0013] Preferably, in step S3, the formula for measuring and calculating the lithium-ion diffusion coefficient D is as follows: D= ; In the formula, It is the impulse and relaxation time, n m V is the number of moles of active material. m S is the molar volume of the active material, and S is the electrode area. It is the difference between two equilibrium potentials. It is the difference in potential before and after the pulse.
[0014] Preferably, in step S4, the heat flux curve formula is: , in, q ch This is the heat generated during the charging process. q dis This refers to the heat generated during the discharge process. q tot It is the total calories. h (t) is the time corresponding to the charging time. t 1 and discharge time t 2 heat flow; Q tot ,Q ch and Q dis It is the amount of electricity generated during a charge-discharge cycle. i (t) is time t 1 and t The current of 2, F and P These are Faraday constant and heat production power, respectively.
[0015] Beneficial effects: This invention is the first to construct "Li + / Ni 2+ A linked characterization system of "mixing degree—lithium-ion diffusion coefficient—heat generation / heat generation power" reveals the intrinsic mechanism of heat generation in ternary lithium batteries during high-temperature cycling. XRD characterization clarifies the role of Li... + / Ni 2+ Mixing is the core factor that causes the lithium-ion diffusion coefficient to decrease, thereby leading to a continuous increase in heat generation and heat generation power, filling the gap in the existing technology that lacks a mechanism linking mixing and heat generation.
[0016] This invention uses XRD diffraction peak intensity ratio I 003 / I 104 As a quantization of Li + / Ni 2+ The core indicator of mixing degree was established, and a quantitative correlation was created between mixing degree, lithium-ion diffusion coefficient, and heat generation characteristics. By comparing test data at different cycle numbers, it was confirmed that the mixing degree increases with increasing mixing degree (I... 003 / I 104 The ratio decreased from 1.18 to 0.22), the lithium-ion diffusion coefficient continued to decline, and the heat generation and heat power increased to 2.85 kJ / mol and 0.99 W / mol, respectively, providing scientific and repeatable data support for the thermal safety assessment of ternary lithium batteries.
[0017] This invention provides a clear direction and theoretical guidance for material modification to suppress high-temperature cycling heat generation, namely, by suppressing Li + / Ni 2+ By mixing cations to lower the lithium-ion diffusion barrier, the rate of heat generation increase can be reduced at its source. This method is not only applicable to the NCM811 material system, but can also be extended to other cathode materials with cation mixing issues, providing accurate characterization evidence and theoretical support for the formulation of thermal management strategies and the optimization of safety performance of ternary lithium batteries in fields such as electric vehicles and energy storage systems. Attached Figure Description
[0018] Figure 1 The specific capacity of the ternary lithium battery in this embodiment of the invention is measured at 50°C and 1C rate during charge and discharge cycles. Figure 2 The heat flow curves and voltage-charge-discharge time curves of the ternary lithium battery in this embodiment of the invention are shown at the 60, 110, 160 and 210 cycles. Figure 3 This refers to the heat generation and heat output power of the ternary lithium battery at different charging and discharging stages in the embodiments of the present invention. Figure 4 The voltage-time curves of the ternary lithium battery in this embodiment of the invention after 60, 110, 160 and 210 charge-discharge cycles are shown. Figure 5 This refers to the diffusion coefficient of the ternary lithium battery at different cycling stages in the embodiments of the present invention; Figure 6 The average value of the lithium-ion diffusion coefficient of the ternary lithium battery in the embodiments of the present invention; Figure 7 The X-ray diffraction patterns of the ternary lithium battery cathode material after 0, 60, 110, 160, and 210 charge-discharge cycles are shown in the embodiments of the present invention. Detailed Implementation
[0019] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0020] This invention provides a method for heat generation and Li during high-temperature cycling of ternary lithium batteries. + / Ni 2+ The association representation method for mixed-row structures includes the following steps: S1: Assemble ternary lithium batteries and perform charge-discharge cycles; S2: XRD was used to characterize the crystallization state of the ternary lithium battery cathode material during cycling. TOPAS software was used to identify the peak positions and analyze the intensity of the diffraction peaks of the crystal phases. The intensity ratio of the diffraction peaks of the (003) and (104) crystal planes was calculated and denoted as I. 003 / I 104 ; S3: The specific capacity Q and lithium-ion diffusion coefficient D of ternary lithium batteries at 1C charge-discharge rates between 2.8 and 4.3 V were measured using the LAND-CT2001A battery testing system; at the same time, the heat flow parameters of ternary lithium batteries at 50℃ were measured using an eight-channel isothermal calorimeter connected to the LAND-CT2001A battery testing system, and heat flow curves at different cycle numbers were plotted. S4: Based on the heat flow curve plotted in S3, the heat generation and heat generation power are derived.
[0021] This invention first assembles a ternary lithium battery and performs charge-discharge cycles; in this invention, the ternary lithium battery comprises: Positive electrode: NCM811 material; Conductive agent: Acetylene black; Adhesive: Polyvinylidene fluoride (PVDF); Solvent: 1-Methyl-2-pyrrolidone (NMP); Anode: Lithium foil material; Electrolyte: Ethyl carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) containing 1M LiPF6, wherein the volume ratio of EC:EMC:DMC in the electrolyte is 1:1:1; Current collector: Aluminum foil; Diaphragm: Celgard 2325.
[0022] In this invention, the assembly steps of the ternary lithium battery are as follows: 1) Using NCM811 material as the positive electrode active material, acetylene black and polyvinylidene fluoride (PVDF) are ground and mixed evenly in a quartz mortar at a mass ratio of 8:1:1 to obtain a mixed powder. 2) Using 99.0% pure 1-methyl-2-pyrrolidone (NMP) as a solvent, the above mixed powder is mixed with the solvent to obtain a slurry; 3) Using aluminum foil as a substrate, the above slurry is uniformly coated on the substrate surface (the thickness of the scraper is set to 100 μm), and pre-dried at 110℃ for 2 h; then the pre-dried substrate is transferred to a vacuum drying oven, the oven temperature is set to 110℃, and the temperature is maintained for 12 h to obtain the electrode material.
[0023] The NCM811 material on the electrode has a thickness of 40 μm and an areal density of 3.5 mg / cm². -2 The electrode material was cut into pieces with an area of 1.131 cm². 2 Circular electrodes are used as backup electrodes.
[0024] 4) In an argon-filled glove box, a ternary lithium battery is assembled using the above-mentioned circular electrode as the positive electrode, a lithium sheet with a diameter of 15.6 mm and a thickness of 0.45 mm as the negative electrode, a Celgard 2325 membrane as the separator, and a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) containing 1 M LiPF6 (volume ratio of 1:1:1) as the electrolyte.
[0025] In this invention, the ternary lithium battery is preferably subjected to 60 to 210 charge-discharge cycles, and more preferably 60, 110, 160 or 210 cycles. During charge-discharge cycles, this invention utilizes XRD to characterize the crystallization state of the cathode material in a ternary lithium battery during cycling. TOPAS software is used to identify the peak positions and analyze the intensity of the diffraction peaks on the crystal phases, calculating the intensity ratio of the diffraction peaks on the (003) and (104) crystal planes, denoted as I. 003 / I 104 ; This invention uses I 003 / I 104 Numerical quantization characterization of Li + / Ni 2+ The degree of mixing; the lower the value, the more severe the mixing.
[0026] In this invention, the XRD is preferably performed using a D8 ADVANCE Da Vinci type X-ray diffractometer; The XRD test preferably uses a Cu target, Kα radiation, and a wavelength λ = 1.55 Å; The XRD test scanning mode is θ-θ continuous scanning, the scanning range is 2θ=10°~90°, and the scanning speed is 2° / min.
[0027] In a specific embodiment of the present invention, the XRD testing and characterization process includes: 1. Sample preparation: The NCM811 cathode material is made into a powder sample to ensure that the sample is uniform and free from contamination; the particle size of the powder sample is controlled within the range of 10~20μm to ensure the accuracy of XRD test.
[0028] 2. XRD testing equipment and parameter settings Using a D8 ADVANCE Da Vinci X-ray diffractometer (Germany); X-ray source: Cu target, Kα radiation, wavelength λ=1.55 Å; Scanning range: 2θ angle range of 10° to 90°, covering the main diffraction peaks of the material; Scanning speed: 2° / min, ensuring signal-to-noise ratio and resolution of data acquisition; Filter: Ni filter is used to reduce stray radiation and improve the clarity of diffraction peaks; Voltage and current: The voltage of the X-ray generator is 40 kV and the current is 30 mA, suitable for Kα radiation of Cu target.
[0029] 3. Data Collection The sample was placed on the sample stage of the XRD instrument, ensuring that the sample was perpendicular to the X-ray beam. During the ternary lithium charge-discharge cycle, the XRD diffraction pattern of the NCM811 cathode material was collected periodically, and the intensity ratio of the diffraction peaks of the (003) and (104) crystal planes was calculated and denoted as I. 003 / I104 Used to characterize Li in NCM811 cathode material + / Ni 2+ Degree of mixing.
[0030] In this invention, TOPAS software is an existing software tool specifically used for X-ray diffraction (XRD) data analysis and crystal structure refinement. Its main function and purpose is to extract the crystal structure information of the material by fitting and analyzing the experimentally measured XRD diffraction pattern, thereby achieving accurate characterization of key properties such as phase composition, lattice parameters, and crystallinity of the material.
[0031] This invention utilizes the LAND-CT2001A battery testing system to measure the specific capacity Q and lithium-ion diffusion coefficient D of ternary lithium batteries at a 1C charge / discharge rate between 2.8 and 4.3 V. In this invention, the formula for measuring and calculating the lithium-ion diffusion coefficient D is as follows: D= ; In the formula, It is the impulse and relaxation time, n m V is the number of moles of active material. m S is the molar volume of the active material, and S is the electrode area. It is the difference between two equilibrium potentials. It is the difference in potential before and after the pulse.
[0032] Meanwhile, this invention utilizes an eight-channel isothermal calorimeter connected to the LAND-CT2001A battery testing system to measure the heat flow parameters corresponding to the number of charge-discharge cycles of ternary lithium batteries at 50℃, and plots heat flow curves for different cycle numbers. Finally, based on the plotted heat flow curve, the present invention derives the heat generation and heat generation power.
[0033] In this invention, the heat flow curve formula is as follows: , in, q ch This is the heat generated during the charging process. q dis This refers to the heat generated during the discharge process. qtot It is the total calories. h (t) is the time corresponding to the charging time. t 1 and discharge time t 2 heat flow; Q tot , Q ch and Q dis It is the amount of electricity generated during a charge-discharge cycle. i (t) is time t 1 and t The current of 2, F and P These are Faraday constant and heat production power, respectively.
[0034] Example 1: Ternary lithium-ion battery test samples based on NCM811 cathode material were prepared and subjected to 60 charge-discharge cycles at 50℃ and 1C rate. The Li-N ratio of the NCM811 cathode material in the ternary lithium-ion battery was analyzed by XRD. + / Ni 2+ Characterization of mixing degree, characterization of heat generation and heat power of ternary lithium battery, and characterization of lithium ion diffusion coefficient.
[0035] Example 2: Ternary lithium-ion battery test samples based on NCM811 cathode material were prepared and subjected to 110 charge-discharge cycles at 50℃ and 1C rate. The Li-N ratio of the NCM811 cathode material in the ternary lithium-ion battery was analyzed by XRD. + / Ni 2+ Characterization of mixing degree, characterization of heat generation and heat power of ternary lithium battery, and characterization of lithium ion diffusion coefficient.
[0036] Example 3: Ternary lithium-ion battery test samples based on NCM811 cathode material were prepared and subjected to 160 charge-discharge cycles at 50℃ and 1C rate. The Li-N ratio of the NCM811 cathode material in the ternary lithium-ion battery was analyzed by XRD. + / Ni 2+ Characterization of mixing degree, characterization of heat generation and heat power of ternary lithium battery, and characterization of lithium ion diffusion coefficient.
[0037] Example 4: Ternary lithium-ion battery test samples based on NCM811 cathode material were prepared and subjected to 210 charge-discharge cycles at 50℃ and 1C rate. The Li-N ratio of the NCM811 cathode material in the ternary lithium-ion battery was analyzed by XRD. + / Ni 2+ Characterization of mixing degree, characterization of heat generation and heat power of ternary lithium battery, and characterization of lithium ion diffusion coefficient.
[0038] Comparative Example 1: The difference from Example 1 is that the ternary lithium battery composed of NCM811 cathode material has not undergone charge-discharge cycles.
[0039] To investigate the root cause of the variation in the lithium-ion diffusion coefficient in ternary lithium batteries at different charge-discharge cycle stages, this invention conducted XRD tests on the NCM811 cathode material of the ternary lithium batteries in Examples 1-4 and Comparative Example 1 after different charge-discharge cycle numbers, obtaining X-ray diffraction (XRD) patterns. The results are as follows: Figure 7 As shown.
[0040] After 60, 110, and 160 charge-discharge cycles, the ratio in Examples 1-3 of this invention decreased to 0.56, 0.29, and 0.22, respectively. In Example 4, when the number of charge-discharge cycles reached 210, the (003) crystal plane diffraction peak of the NCM811 cathode material almost completely disappeared. In contrast, the NCM811 cathode material in Comparative Example 1, which had not undergone charge-discharge cycles, showed that its I... 003 / I 104 The ratio is approximately 1.18, which means that Li is not present in the cathode material that has not undergone charge-discharge cycles. + / Ni 2+ Cation mixing phenomenon. The results of Examples 1-4 and Comparative Example 1 above show that during charge-discharge cycling, the NCM811 cathode material underwent severe Li-ion mixing. + / Ni 2+ Cation mixing.
[0041] This invention utilizes the LAND-CT2001A battery testing system to measure the specific capacity Q and lithium-ion diffusion coefficient D of ternary lithium batteries at a 1C charge / discharge rate between 2.8 and 4.3 V. like Figure 1 The figure shows the specific capacity Q curves of the ternary lithium battery of this invention at 50°C and 1C rate for different numbers of charge-discharge cycles. The curves show multiple decay intervals at different cycling stages, indicating that the composition and structure of the NCM811 cathode material have changed, resulting in Li... + / Ni 2+ Mixed arrangement phenomenon.
[0042] This invention measured the lithium-ion diffusion coefficient D of a ternary lithium battery after 60, 110, 160, and 210 charge-discharge cycles at 50°C. Figure 5 and 6 As shown, Figure 4 The constant current intermittent titration potential-test time curve obtained in this invention is used to calculate the diffusion coefficient values at different cycle stages, as shown in the figure. Figure 5 As shown, its average diffusion coefficient is as follows: Figure 6As shown, the formula for calculating the lithium-ion diffusion coefficient Ds at different cycling stages is as follows: D s = ; In the formula, It is the impulse and relaxation time, n m V is the number of moles of active material. m S is the molar volume of the active material, and S is the electrode area. It is the difference between two equilibrium potentials. It is the difference in potential before and after the pulse.
[0043] Figures 4-6 Experimental results show that the lithium-ion diffusion coefficient in ternary lithium batteries gradually decreases as charge-discharge cycles proceed; the lithium-ion diffusion coefficient at different cycle stages remains the core factor affecting the heat generation and heat output of ternary lithium batteries.
[0044] Furthermore, this invention utilizes an eight-channel isothermal calorimeter connected to the LAND-CT2001A battery testing system to measure the heat flow parameters corresponding to the number of charge-discharge cycles of a ternary lithium battery at 50°C, and plots heat flow curves for different number of cycles. like Figure 2 The figure shows the heat flow curves and voltage-charge-discharge time curves of a ternary lithium battery at 60, 110, 160, and 210 cycles. Figure 2 It can be seen that as the charge-discharge cycle proceeds, the intensity of the exothermic peak of the heat flow curve gradually increases, which means that the heat generated by the ternary lithium battery is continuously increasing.
[0045] pass Figure 2 Calculated from Figure 2 The specific values of heat generation and heat power were derived from the heat flow curve. The relationship between the heat generation and heat power during the cycling process of the ternary lithium battery and the number of cycles is as follows: Figure 3 As shown.
[0046] Figure 2 and Figure 3 The experimental results show that both the heat generation and the heat generation power increase with the increase of the number of charge-discharge cycles, reaching the maximum value at the 210th cycle, which are 2.85 kJ / mol and 0.99 W / 6 mol, respectively.
[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for heat generation and Li during high-temperature cycling of a ternary lithium battery + / Ni 2+ The association representation method for mixed-rowsing is characterized by, Includes the following steps: S1: Assemble ternary lithium batteries and perform charge-discharge cycles; S2: XRD was used to characterize the crystallization state of the ternary lithium battery cathode material during cycling. TOPAS software was used to identify the peak positions and analyze the intensity of the diffraction peaks of the crystal phases. The intensity ratio of the diffraction peaks of the (003) and (104) crystal planes was calculated and denoted as I. 003 / I 104 ; S3: The specific capacity Q and lithium-ion diffusion coefficient D of ternary lithium batteries at 1C charge-discharge rates between 2.8 and 4.3 V were measured using the LAND-CT2001A battery testing system; at the same time, the heat flow parameters of ternary lithium batteries at 50℃ were measured using an eight-channel isothermal calorimeter connected to the LAND-CT2001A battery testing system, and heat flow curves at different cycle numbers were plotted. S4: Based on the heat flow curve plotted in S3, the heat generation and heat generation power are derived.
2. The characterization method according to claim 1, characterized in that, In step S1, the ternary lithium battery comprises: Positive electrode: NCM811 material; Conductive agent: Acetylene black; Adhesive: Polyvinylidene fluoride; Solvent: 1-Methyl-2-pyrrolidone; Anode: Lithium foil material; Electrolyte: ethylene carbonate / ethyl methyl carbonate / dimethyl carbonate, wherein the volume ratio of ethylene carbonate:ethyl methyl carbonate:dimethyl carbonate in the electrolyte is 1:1:1; the electrolyte contains 1M LiPF6. Current collector: Aluminum foil; Diaphragm: Celgard 2325.
3. The characterization method according to claim 1, characterized in that, In step S1, the number of charge-discharge cycles is 60 to 210.
4. The characterization method according to claim 1, characterized in that, In step S2, the XRD is performed using a D8 ADVANCE Da Vinci type X-ray diffractometer.
5. The characterization method according to claim 1 or 4, characterized in that, In step S2, the XRD test uses a Cu target, Kα radiation, and a wavelength λ = 1.55 Å.
6. The characterization method according to claim 1 or 4, characterized in that, In step S2, the XRD test scanning mode is θ-θ continuous scanning, the scanning range is 2θ=10°~90°, and the scanning speed is 2° / min.
7. The characterization method according to claim 2, characterized in that, In step S2, the positive electrode is a circular electrode sheet, and the thickness of the active material NCM81 on the positive electrode is 40 μm, with an areal density of 3.5 mg / cm². -2 .
8. The characterization method according to claim 1, characterized in that, In step S3, the formula for measuring and calculating the lithium-ion diffusion coefficient D is as follows: D= ； In the formula, It is the impulse and relaxation time, n m V is the number of moles of active material. m S is the molar volume of the active material, and S is the electrode area. It is the difference between two equilibrium potentials. It is the difference in potential before and after the pulse.
9. The characterization method according to claim 1, characterized in that, In S4, the heat flow curve formula is: in, q ch This is the heat generated during the charging process. q dis This refers to the heat generated during the discharge process. q tot It is the total calories. h (t) is the time corresponding to the charging time. t 1 and discharge time t 2 heat flow; Q tot , Q ch and Q dis It is the amount of electricity generated during a charge-discharge cycle. i (t) is time t 1 and t The current of 2, F and P These are Faraday constant and heat production power, respectively.