Sensitivity of electrodes in a lithium ion cell to temperature and SOC
-
摘要: 采用阻抗譜技術,對2.8 A·h 18650電芯進行拆解解析,單獨分析正負極電極在不同溫度下(25、10和-5℃),不同荷電狀態下的阻抗變化.結果表明:在不同溫度下,在20%~100%荷電狀態下,負極作為控制電極,其反應電化學阻抗是正極的數倍,尤其是在-5℃,達到了4倍,負極是電芯一致性問題中動力學因素的控制主因;在0~20%荷電狀態下,在10和25℃下,正極的反應電化學阻抗要遠遠大于負極,正極成為控制端.結合目前電動車上動力電池的實用荷電狀態一般在20%~95%,針對該2.8 A·h 18650電芯,提高負極電極的一致性是核心所在.同理,對其他類型電芯而言,在電芯設計過程中,在綜合考慮成本的前提下,需要更有針對性地提高正負極的一致性標準,從而更為有效地改善整個電芯產品的一致性.Abstract: In the design and development of electric vehicles (EVs), the variation in lithium ion cells (LICs) is one of the most important safety issues as it can cause a decrease in the life of the battery systems and shorten the mileage range. This problem is rooted in the design accuracy and rationality of the process values for the battery electrodes, and defining the effects of temperature and state of charge (SOC) on the electrodes is a critical step toward improving the variation in LICs. In this paper, the electrochemical impedance spectroscopy (EIS) method was adopted to study the 2.8 A·h 18650 cell. Firstly, the cells was dissembled and then attached the positive/negative electrodes separately to coin cells with an Li plate as the count electrode. Secondly, the impedance changes at different temperatures (25, 10 and-5℃) and the SOCs for these coin cells were studied using EIS. The results show that for 20% -100% state of charge at different temperatures, the negative electrode is the control electrode; electrochemical impedance is several times that of the positive electrode, especially, at-5℃, it reaches 4 times. Therefore, the negative electrode is the control factor in the kinetic variation process. For 0-20% SOC at 25 and 10℃, the electrochemical impedance of the positive electrode is larger than that of the negative electrode and it becomes the control electrode. Regarding EVs:1) the normal SOC usage range is 20% -95%; and 2) the working temperature range is above 0℃ to satisfy cell variations in the pack and benefit the life of the cells. Combined with the above results, it can be concluded that improving the variation in the negative electrodes is most useful to the variation in the 2.8 A·h 18650 cell. Above all, in the design process for LICs, the variation of electrodes should be improved as a target for improving costs and yields.
-
Key words:
- 18650 cell /
- state of charge (SOC) /
- variation /
- electrode /
- electrochemical impedance spectroscopy
-
參考文獻
[1] Goodenough J B, Park K S. The Li-ion rechargeable battery:a perspective. J Am Chem Soc, 2013, 135(4):1167 [2] Scrosati B, Garche J. Lithium batteries:status, prospects and future. J Power Sources, 2010, 195(9):2419 [3] Wu H, Cui Y. Designing nanostructured Si anodes for high energy lithium ion batteries. Nano Today, 2012, 7(5):414 [4] Dai Y L, Srinivasan V. On graded electrode porosity as a design tool for improving the energy density of batteries. J Electrochem Soc, 2016, 163(3):A406 [6] Baumhöfer T, Brühl M, Rothgang S, et al. Production caused variation in capacity aging trend and correlation to initial cell performance. J Power Sources, 2014, 247:332 [9] An F Q, Huang J, Wang C Y, et al. Cell sorting for parallel lithium-ion battery systems:evaluation based on an electric circuit model. J Energy Storage, 2016, 6:195 [10] Jannesari H, Emami M D, Ziegler C. Effect of electrolyte transport properties and variations in the morphological parameters on the variation of side reaction rate across the anode electrode and the aging of lithium ion batteries. J Power Sources, 2011, 196(22):9654 [11] Santhanagopalan S, White R E. Quantifying cell-to-cell variations in lithium ion batteries. Int J Electrochem, 2012, 2012:395838-1 [12] Kenney B, Darcovich K, MacNeil D D, et al. Modelling the impact of variations in electrode manufacturing on lithium-ion battery modules. J Power Sources, 2012, 213:391 [13] An F Q, Chen L F, Huang J, et al. Rate dependence of cell-tocell variations of lithium-ion cells. Sci Rep, 2016, 6:35051 [14] Zhang J B, Huang J, Chen L F, et al. Lithium-ion battery discharge behaviors at low temperatures and cell-to-cell uniformity. J Autom Safety Energy, 2014, 5(4):391 -
點擊查看大圖
計量
- 文章訪問數: 811
- HTML全文瀏覽量: 419
- PDF下載量: 23
- 被引次數: 0
下載:
