调控电解液溶剂组分实现LCO/C低温18650电池循环寿命显著提升

doi:10.19799/j.cnki.2095-4239.2024.0374

摘要/Abstract

摘要：

低温18650电池的循环寿命一直是限制其发展的关键因素，为了实现长循环寿命与低温性能的兼顾，通过调控电解液溶剂组分，对比分析了不同电解液对电池倍率性能、高低温放电、荷电保持率、循环寿命、EIS阻抗变化等的影响。结果表明，电解液组分设计对电池性能有显著影响，通过低熔点的长链线性羧酸酯部分取代碳酸酯及短链羧酸酯，既可以实现较好的低温性能，同时又提升了高温稳定性。EP、PP的比例对于LCO/C电极体系循环稳定性有重要作用。其中溶剂组分EC+EP+PP(质量比2∶5∶3)具备最佳的综合性能，研制的LTB电池5C放电容量保持率达99.86%，-40 ℃/1C放电容量保持率达92.84%，循环1000次后低温-40 ℃/1C放电仍然达到初始低温放电容量的90%，常温循环1500次容量保持率达85%，低温-10 ℃循环500次容量保持率82.4%。

关键词: 低温, 18650电池, 电解液, 循环寿命, 锂离子电池

Abstract:

The cycle life of low-temperature 18650 batteries has always been a key factor that limited their development. To achieve a balance between a long cycle life and low-temperature performance, the effects of different electrolytes on rate performance, high- and low-temperature discharge performance, charge retention capacity, cycle life, low-temperature cycle performance, and EIS were compared and analyzed by adjusting the components of the electrolyte solvent. The results demonstrated that the design of the electrolyte composition had a significant impact on the performance of the battery. By partially replacing the carbonate esters and the short-chain carboxylic esters with long, linear carboxylic esters having a low melting point, impressive low-temperature performance as well as high-temperature stability were achieved, which illustrated that EP and PP play an important role in the cyclic stability of the LCO/C electrode system. The solvent component EC+EP+PP (mass ratio 2∶5∶3) exhibited the best comprehensive performance. The developed LTB battery maintained a discharge capacity retention of 99.86% at 5C and a discharge capacity retention of 92.84% at -40 ℃ and 1C. After 1000 cycles, the low-temperature discharge capacity at -40 ℃ and 1C was still 90% of the initial low-temperature discharge capacity. At room temperature, the cycling retention rate reached 85% after 1500 cycles; at a low temperature of -10 ℃, the cycling retention rate was 82.4% after 500 cycles.

Key words: low-temperature, 18650 battery, electrolyte, cycle life, lithium-ion battery

中图分类号:

TM 912.9

程广玉, 刘新伟, 刘硕, 顾海涛, 王可. 调控电解液溶剂组分实现LCO/C低温18650电池循环寿命显著提升[J]. 储能科学与技术, 2024, 13(7): 2171-2180.

Guangyu CHENG, Xinwei LIU, Shuo LIU, Haitao GU, Ke WANG. Controlling electrolyte solvent components to enhance cycle life of LCO/C low-temperature 18650 batteries[J]. Energy Storage Science and Technology, 2024, 13(7): 2171-2180.

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溶剂	熔点/℃	沸点/℃	60 ℃蒸气压/kPa	黏度/(mPa·s)	介电常数
EC	36.4	248	0.04	1.93	89.78
DEC	-74.3	126	9.3	0.753	2.805
EMC	-53	110	21.7	0.648	2.958
EA	-84	77.1	55.8	0.423	6.05
EP	-73	99.2	25.4	0.492	5.717
PP	-75.9	122.5	10.6	0.68	4.7

电解液编号	常温电导率/(mS/cm)	-40 ℃电导率/(mS/cm)
A	11.4	1.43
B	8.61	1.16
C	7.94	1.13

电池型号	相对0.2C容量保持率
电池型号	0.2C	1C	3C	5C	6.8C
LTA	100%	100.73%	100.50%	100.24%	97.82%
LTB	100%	99.98%	99.94%	99.86%	94.95%
LTC	100%	99.94%	99.84%	99.61%	94.70%
DB	100%	99.24%	98.92%	68.71%	—

电池编号	初始容量/mAh	保持容量/mAh	保持率	恢复容量/mAh	恢复率
LTA-1	2178.4	1988.9	91.30%	2139.4	98.21%
LTA-2	2179.9	1988.8	91.23%	2139.2	98.13%
LTB-1	2209.8	2045.0	92.54%	2159.3	97.71%
LTB-2	2213.1	2053.3	92.78%	2166.1	97.88%
LTC-1	2150.3	1978.3	92.00%	2084.8	96.95%
LTC-2	2157.4	1987.6	92.13%	2136.3	96.61%

电池编号	初始容量/mAh	初始交流内阻 /mΩ	循环次数	循环剩余容量 /mAh	循环容量保持率	循环后交流内阻/mΩ	内阻增长率
LTA-1	2271.7	15.45	478	1760.1	77.48%	32.6	111.00%
LTA-2	2274.7	15.41	442	1756.9	77.24%	31.4	103.76%
LTA-3	2272	15.61	431	1756.4	77.31%	33.5	114.61%
LTB-1	2267.1	14.88	1500	1925.7	84.94%	43.2	190.32%
LTB-2	2268.8	14.45	1500	1952.1	86.04%	42.7	195.50%
LTB-3	2259.2	15.02	1500	1934.5	85.63%	43.1	186.95%
LTC-1	2258.4	16.23	1500	1908.7	84.52%	54.9	238.26%
LTC-2	2270.5	15.83	1500	1931.6	85.07%	52.7	232.91%
LTC-3	2262.5	15.96	1500	1923.8	85.03%	53.8	237.09%
DB-1	2258.3	16.54	305	1753.3	77.64%	34.6	109.19%
DB-2	2263	16.78	326	1830.9	80.91%	35.8	113.35%