Energy Storage Science and Technology ›› 2021, Vol. 10 ›› Issue (1): 150-155.doi: 10.19799/j.cnki.2095-4239.2020.0222

• Energy Storage Materials and Devices • Previous Articles     Next Articles

Exploration of the cause of hydrogen generation in NCM lithium-ion batteries

Xueqin YUAN(), Lei YANG   

  1. West Anhui University, Liu'an 237012, Anhui, China
  • Received:2020-06-23 Revised:2020-07-14 Online:2021-01-05 Published:2021-01-08
  • Contact: Xueqin YUAN E-mail:22000023@wxc.edu.cn

Abstract:

In this work, gas chromatography (GC) and rechargeable symmetrical lithium-ion batteries were used to explore the causes of H2 generation in NCM lithium-ion batteries (LIBs). In addition to determining whether H2 is produced by the reduction of trace water in the battery, this paper explores whether the H2 generation mechanisms for NCM LIBs are best described as arising from the proton electrolyte oxide (R-H+) or carbonate dissociation into H?. Considering that R-H+ deposited on the negative electrode is the related product between the positive and negative electrodes, the graphite/graphite negative symmetrical cell (NSC), the NCM/NCM (LiNi0.6Co0.2Mn0.2O2 is defined as NCM) positive symmetrical cell (PSC), and graphite/NCM pouch cell (PC) with charge and discharge capacity were prepared. After a room temperature cycling test and an overcharge test, the GC results indicated that H2 was produced in the soft package full cell and the negative symmetrical battery, but not in the positive symmetrical battery. This result supports the R-H+ mechanism, where H2 is produced by the reduction of the R-H+ deposited on the negative electrode, so in the positive symmetrical cell, no H2 is produced. In order to eliminate any interfering signal of H2 produced by the reduction of trace water in the battery, the positive symmetrical battery without H2 generation after cycles was selected. After adding trace water to the system, H2 was indeed detected in the GC results. Therefore, H2 production from trace moisture in the original cells can be ignored. Finally, the mechanism of H2 production by the dissociation of carbonate to H? was tested using the positive symmetric cell. The influence of R-H+ and water on the final H2 production can be ignored according to the previous experimental results. After a high temperature storage and a high temperature overcharge test, no H2 was detected in the cathode symmetry battery after cycling, so the mechanism of H2 production by dissociation of carbonate to H? is not the active mechanism.

Key words: gas chromatography, symmetric cells, H2, R-H+, H?

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