The lifetime of lithium ion batteries (LIBs) decreases under continuous cycling due to various degradation processes, such as dissolution of transition metals (TMs) from the electrodes. Therefore, suitable methods to analyze the oxidation states of TMs are mandatory to better understand the dissolution mechanisms of TMs from positive and negative electrodes (LIBs). To investigate the dissolution of Mn²⁺ and Mn³⁺ in electrolytes of LIBs, a previously implemented capillary electrophoresis (CE) method with UV/Vis spectroscopy detection was further developed with the aim of higher sensitivities and additional detection of other dissolved divalent TMs such as Co²⁺, Ni²⁺, and Cu²⁺. Therefore, inductively coupled plasma–mass spectrometry was applied instead of UV/Vis for detection. This also allows the use of Ga³⁺ instead of the previously used Cu²⁺ as an internal standard, which solves the limitation of this method for cycled LIBs due to copper dissolution from the copper-based current collector. The CE buffer based on sodium diphosphate as complexing agent for the stabilization of Mn³⁺ and cetyltrimethylammonium bromide as dynamic capillary wall modifier was optimized in terms of concentrations and pH. Finally, both manganese species and Co²⁺, Ni²⁺, and Cu²⁺ could be analyzed within 15 min. With this improved method, the dissolution of TMs in LIBs for positive electrode materials such as LiNi_0.5Mn_1.5O₄ (LNMO) or LiNi_xCo_yMn_zO₂ (NCM, x + y + z = 1) can be studied in future in more detail.

中文翻译：

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使用毛细管电泳联用电感耦合等离子体质谱法研究 Mn2+/3+、Cu2+、Co2+ 和 Ni2+ 的方法开发

由于各种降解过程，例如过渡金属 (TM) 从电极中溶解，锂离子电池 (LIB) 的寿命在连续循环下会缩短。因此，必须采用合适的方法来分析 TM 的氧化态，以更好地了解 TM 从正极和负极 (LIB) 中的溶解机制。为了研究 Mn ²⁺和 Mn ³⁺在 LIB 电解质中的溶解，进一步开发了先前实施的具有 UV/Vis 光谱检测的毛细管电泳 (CE) 方法，目的是提高灵敏度和额外检测其他溶解的二价 TM，例如作为 Co ²⁺、Ni ²⁺和 Cu ²⁺. 因此，应用电感耦合等离子体质谱法代替 UV/Vis 进行检测。这也允许使用 Ga ³⁺代替以前使用的 Cu ²⁺作为内标，这解决了由于铜基集电器中的铜溶解而导致该方法对循环 LIB 的限制。^{基于二磷酸钠作为稳定 Mn 3+}的络合剂和作为动态毛细管壁改性剂的十六烷基三甲基溴化铵的 CE 缓冲液在浓度和 pH 方面进行了优化。最后，锰物种和 Co ²⁺、Ni ²⁺和 Cu ²⁺可在 15 分钟内完成分析。通过这种改进的方法，可以研究 TM 在 LIB 中对正极材料如 LiNi _0.5 Mn _1.5 O ₄ (LNMO) 或 LiNi _x Co _y Mn _z O ₂ (NCM, x  +  y  +  z  = 1)的溶解情况未来更详细。