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CN-121978143-A - Heat generation and Li in high-temperature cycle process of ternary lithium battery+/Ni2+Association characterization method for mixed row

CN121978143ACN 121978143 ACN121978143 ACN 121978143ACN-121978143-A

Abstract

The invention provides a method for relevant characterization of heat generation and Li + /Ni 2+ mixed discharge in a high-temperature cycle process of a ternary lithium battery, which comprises the steps of assembling the ternary lithium battery for charge-discharge cycle, testing and characterizing a crystallization state of a ternary lithium battery positive electrode material in the cycle process by utilizing XRD, carrying out peak position identification and intensity analysis on a crystal phase diffraction peak by adopting TOPAS software, calculating the intensity ratio of the (003) crystal face diffraction peak to the (104) crystal face diffraction peak to be I 003 /I 104 , measuring the specific capacity Q and the lithium ion diffusion coefficient D of the ternary lithium battery under the 1C charge-discharge multiplying power of 2.8-4.3V by utilizing a LAND-CT2001A battery testing system, simultaneously measuring heat flow curves corresponding to the charge-discharge times of the ternary lithium battery under 50 ℃ by utilizing an eight-channel isothermal calorimeter combined with the LAND-CT2001A battery testing system, deducing the heat generation amount and the heat generation power under different cycle times based on the drawn heat flow curves, and achieving relevant characterization of the ternary lithium battery high-temperature cycle heat generation and Li + /Ni 2+ mixed discharge.

Inventors

  • ZHUANG YUNPENG
  • SONG XIAOMEI
  • LI XUEYING
  • LI XIANG
  • SUN YUANZE

Assignees

  • 烟台职业学院
  • 山东(烟台)中日韩产业技术研究院

Dates

Publication Date
20260505
Application Date
20260327

Claims (9)

  1. 1. The associated characterization method for heat generation and Li + /Ni 2+ mixed discharge in the high-temperature cycle process of the ternary lithium battery is characterized by comprising the following steps of: s1, assembling a ternary lithium battery to perform charge and discharge circulation; S2, testing and characterizing the crystallization state of the ternary lithium battery anode material in the circulating process by utilizing XRD, identifying the peak position and analyzing the intensity of a crystal phase diffraction peak by adopting TOPAS software, and calculating the intensity ratio of the (003) crystal face diffraction peak to the (104) crystal face diffraction peak to be I 003 /I 104 ; S3, measuring the specific capacity Q and the lithium ion diffusion coefficient D of the ternary lithium battery under the 1C charge-discharge multiplying power of 2.8-4.3V by using a LAND-CT2001A battery test system, simultaneously measuring the heat flow parameters corresponding to the charge-discharge times of the ternary lithium battery under 50 ℃ by using an eight-channel isothermal calorimeter combined with the LAND-CT2001A battery test system, and drawing heat flow curves under different circulation times; And S4, deducing and obtaining heat generation quantity and heat generation power based on the heat flow curve drawn in the step S3.
  2. 2. The characterization method of claim 1 wherein in step S1, the ternary lithium battery composition comprises: Positive electrode, NCM811 material; a conductive agent, namely acetylene black; a binder, polyvinylidene fluoride; Solvent 1-methyl-2-pyrrolidone; A negative electrode made of lithium sheet material; The electrolyte comprises ethylene carbonate/methyl ethyl carbonate/dimethyl carbonate, wherein the volume ratio of ethylene carbonate to methyl ethyl carbonate to dimethyl carbonate is 1:1:1, and the electrolyte comprises 1M LiPF 6 ; A current collector, namely aluminum foil; Diaphragm Celgard2325.
  3. 3. The characterization method according to claim 1, wherein in the step S1, the number of charge-discharge cycles is 60 to 210.
  4. 4. The characterization method according to claim 1, wherein in step S2, the XRD uses an X-ray diffractometer of the type D8 ADVANCE DA VINCI.
  5. 5. The characterization method of claim 1 or 4 wherein in step S2 the XRD test uses a Cu target, ka radiation, wavelength λ = 1.55 a.
  6. 6. The characterization method according to claim 1or 4, wherein in step S2, the XRD test scan pattern is a θ - θ continuous scan, the scan range is 2θ=10° to 90 °, and the scan speed is 2 °/min.
  7. 7. The characterization method according to claim 2, characterized in that in step S2, the positive electrode is a circular pole piece, and the active material NCM81 on the positive electrode has a thickness of 40 μm and an area density of 3.5mg cm -2 .
  8. 8. The characterization method according to claim 1, wherein in step S3, the measurement calculation formula of the lithium ion diffusion coefficient D is D= ; In the formula, Is the pulse and relaxation time, n m is the moles of active material, V m is the molar volume of active material, S is the electrode area, Is the difference between the two equilibrium potentials, Is the difference between the potentials before and after the pulse.
  9. 9. The characterization method according to claim 1, wherein in S4, the heat flow curve formula is Where Q ch is the heat generated during charging, Q dis is the heat generated during discharging, Q tot is the total heat, h (t) is the heat flow corresponding to charging time t 1 and discharging time t 2 , Q tot 、Q ch and Q dis are the amounts of electricity during the charging and discharging cycles, i (t) is the current at times t 1 and t 2 , and F and P are the faraday constant and the heat generation power, respectively.

Description

Associated characterization method for heat generation and Li +/Ni2+ mixed discharge in high-temperature cycle process of ternary lithium battery Technical Field The invention belongs to the technical field of ternary lithium batteries, and particularly relates to a method for associated characterization of heat generation and Li +/Ni2+ mixed discharge in a ternary lithium battery high-temperature circulation process. Background With the wide application of lithium ion batteries in electric vehicles and energy storage systems, the safety problem of lithium ion batteries is increasingly concerned. The heat generation of the lithium ion battery during the charge and discharge processes is a key factor affecting the safety performance, and researches show that the inherent characteristics of the electrode material are main factors affecting the heat generation of the lithium ion battery, in addition to external factors. In ternary lithium batteries, NCM811 (LiNi 0.8Co0.1Mn0.1O2) is widely used due to its high energy density. However, NCM811 has problems of rapid capacity decay and poor safety during use. Research shows that the electrochemical performance of the ternary lithium battery is closely related to the change of the crystal structure of the NCM811 cathode material in the charge-discharge process. Since the ionic radii of Li + (7.6A) and Ni 2+ (6.9A) are similar, ni 2+ migrates from the transition metal layer to the lithium layer during charge and discharge, resulting in mixed discharge of Li +/Ni2+. The Li +/Ni2+ mixed discharge can cause the occupation of active lithium sites, thereby affecting the lithium ion diffusion in the NCM811 positive electrode material, causing the capacity attenuation and the rate capability reduction of the ternary lithium battery, causing the safety problem after the ternary lithium battery is recycled for a plurality of times, and especially causing the Li +/Ni2+ mixed discharge phenomenon in the NCM811 positive electrode material to be more serious under the high temperature condition. The prior art does not establish a linkage analysis system of 'mixed emission degree-lithium ion diffusion-heat generation amount', and cannot provide accurate internal associated data for battery thermal management. Therefore, development of a set of scientific and repeatable association characterization methods is needed to quantify the correspondence of the three. Disclosure of Invention Therefore, the invention aims to provide a correlation characterization method for heat generation and Li +/Ni2+ mixed discharge in a high-temperature cycle process of a ternary lithium battery, and a multi-dimensional characterization test is used for constructing a corresponding relationship between the Li +/Ni2+ mixed discharge degree of a positive electrode material Li +/Ni2+ of the ternary lithium battery, the lithium ion diffusion coefficient of the ternary lithium battery and the heat generation quantity/heat generation power of the ternary lithium battery, revealing an internal mechanism of Li +/Ni2+ mixed discharge for regulating and controlling the heat generation by influencing the lithium ion diffusion, and providing a reliable characterization method and data support for the formulation of a high-temperature cycle thermal management strategy and the optimization of safety performance of the ternary lithium battery. In order to achieve the above object, the present invention provides the following technical solutions: a method for associated characterization of heat generation and Li +/Ni2+ mixed discharge in a ternary lithium battery high-temperature cycle process comprises the following steps: s1, assembling a ternary lithium battery to perform charge and discharge circulation; S2, testing and characterizing the crystallization state of the ternary lithium battery anode material in the circulating process by utilizing XRD, identifying the peak position and analyzing the intensity of a crystal phase diffraction peak by adopting TOPAS software, and calculating the intensity ratio of the (003) crystal face diffraction peak to the (104) crystal face diffraction peak to be I 003/I104; S3, measuring the specific capacity Q and the lithium ion diffusion coefficient D of the ternary lithium battery under the 1C charge-discharge multiplying power of 2.8-4.3V by using a LAND-CT2001A battery test system, simultaneously measuring the heat flow parameters corresponding to the charge-discharge times of the ternary lithium battery under 50 ℃ by using an eight-channel isothermal calorimeter combined with the LAND-CT2001A battery test system, and drawing heat flow curves under different circulation times; And S4, deducing and obtaining heat generation quantity and heat generation power based on the heat flow curve drawn in the step S3. Preferably, in step S1, the ternary lithium battery composition includes: Positive electrode, NCM811 material; a conductive agent, namely acetylene black; a binder, polyvin