关键词: 气相色谱, 对称电池, H₂, R-H⁺, {\mathrm{H}}^{?}

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 (LiNi_0.6Co_0.2Mn_0.2O₂ 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⁺, {\mathrm{H}}^{?}