Electrolyte Reactivity at the Charged Ni-Rich Cathode Interface and Degradation in Li-Ion Batteries

• DOI: 10.1021/acsami.1c22812
• Publication Date: 2022-03-08T19:01:06Z
• Authors: Wesley M. Dose; Israel Temprano; Jennifer P. Allen; Erik Björklund; Christopher A. O’...; Weiqun Li; B. Layla Mehdi; Robert S. Weatherup; Michael F. L. De ...; Clare P. Grey
• Keywords: Reactivity

The chemical and electrochemical reactions at the positive electrode-electrolyte interface in Li-ion batteries are hugely influential on cycle life safety. Ni-rich layered transition metal oxides exhibit higher interfacial reactivity than their lower Ni-content analogues, reacting via mechanisms that poorly understood. Here, we study pivotal role of electrolyte solvent, specifically cyclic ethylene carbonate (EC) linear ethyl methyl (EMC), determining charged LiNi0.33Mn0.33Co0.33O2 (NMC111) LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes by using both single-solvent model electrolytes mixed solvents used commercial cells. While NMC111 exhibits similar parasitic currents with EC-containing EC-free during high voltage holds NMC/Li4Ti5O12 (LTO) cells, this is not case for NMC811. Online gas analysis reveals solvent-dependent related to extent lattice oxygen release accompanying decomposition, which electrolytes. Combined findings from impedance spectroscopy (EIS), TEM, solution NMR, ICP, XPS reveal solvent has a profound impact degradation cathode electrolyte. Higher coupled impedance, thicker oxygen-deficient rock-salt surface reconstruction layer, more salt breakdown, amounts dissolution. These processes suppressed electrolyte, highlighting incompatibility between conventional solvents. Finally, new mechanistic insights into oxidation pathways and, critically, knock-on further degrade electrodes curtailing battery lifetime provided.