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Journal of Electrochemistry ›› 2020, Vol. 26 ›› Issue (6): 777-788.  doi: 10.13208/j.electrochem.200507

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Degradation and Thermal Characteristics of LiNi0.8Co0.15Al0.05O2/Graphite Lithium Ion Battery after Different State of Charge Ranges Cycling

WANG Cun1#, ZHANG Wei-jiang1,5#, HE Teng-fei1#, LEI Bo2, SHI You-jie2, ZHENG Yao-dong3, LUO Wei-lin4, JIANG Fang-ming1,*()   

  1. 1. Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, CAS Key Laboratory of Renewable Energy, Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development, Guangzhou 510640, China
    2. State Key Laboratory of HVDC, Electric Power Research Institute, China Southern Power Grid, Guangzhou 510063
    3. China Southern Power Grid,Guangzhou 510063
    4. Shanghai Power& Energy Storage Battery System Engineering Technology Co. Ltd., Shanghai 200241;
    5. University of Chinese Academy of Sciences, Beijing 100049
  • Received:2020-05-07 Revised:2020-06-12 Online:2020-12-28 Published:2020-06-15
  • Contact: JIANG Fang-ming E-mail:jiangfm@ms.giec.ac.cn

Abstract:

The LiNi0.8Co0.15Al0.05O2 (NCA) cathode exhibits high energy density and large reversible capacity, which plays an essential role in the field of electric vehicles (EVs). However, low capacity retention and poor thermal stability limit its application. Few literatures are found for the capacity degradation mechanism of NCA/graphite batteries at home and abroad. The different state of charge (SOC) ranges cycle degradation behaviors of 18650-type NCA/graphite (2.4 Ah) battery were studied in this paper. The SOC ranges considered were 0% ~ 20% (low), 20% ~ 70% (medium), 70% ~ 100% (high), and 0% ~ 100% (whole). To obtain the states of the batteries being cycled in different SOC ranges, the basic characteristics of the four batteries, including capacity, incremental capacity (IC), internal resistance, and electrochemical impedance spectroscopy (EIS), were tested at 25 oC before and after every 100-cycle up to 400 cycles. At the same time, the surface temperature of the batteries during discharging was monitored to analyze the thermal characteristics. A detailed analysis for the IC curve of NCA/graphite was performed, making the mechanism of capacity degradation more clear. The results show that the battery life would be shortened after the whole SOC range cycling and the battery aging rate would be reduced to a certain extent upon cycled in the partial range. In addition, the battery thermal characteristic became the worst after the whole SOC range cycling, but the battery thermal performance became the best after the medium SOC range cycling. Analyzing IC data reveals that the main reason for the performance degradation of batteries in the high, medium and low SOC ranges cycling may be the loss of active lithium ions, and that in the high SOC range cycling may also include the loss of active materials and the increase of reaction internal resistance.

Key words: Key Words: lithium ion battery, nickel-cobalt-aluminum ternary cathode material, cycle interval, incremental capacity analysis, electrochemical impedance spectroscopy, degradation mechanism

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