LNMO‐Graphite Cells Performance Enhancement by the Use of Acid Scavenging Separators

The performance of cells with high‐voltage LiNi0.5Mn1.5O4 positive electrodes and graphite negative electrodes is affected most adversely by the decomposition of LiPF6‐based electrolyte solutions components and the dissolution of transition metal (TM) ions. Novel approaches to overcome the severe degradation of performance are crucial for the successful design and commercialization of LNMO‐based cells, which are very advantageous due to their high voltage (4.7 V). Acid‐scavenging separators based on poly(divinylbenzene‐4‐vinylpyridine) were tested as a mean for enhancing the stability of LNMO/graphite cells with an additives‐free standard 1 M LiPF6/EC : EMC (3 : 7 v/v) electrolyte solution. Improved cycling performance was demonstrated over reference cells containing commercial polypropylene separators during prolonged cycling at both 30 and 45 °C. Electrochemical impedance spectroscopy, inductively coupled plasma optical emission spectroscopy, high‐resolution scanning electron microscopy, and X‐ray diffraction were used to gain insights into the reasons for the cells performance improvement that is reported herein. Acid traps: High‐voltage LiNi0.5Mn1.5O2 is a promising material for high energy density Li‐ion batteries. At high operating voltages, the major problem occurs mainly due to the instability of electrolyte components. Here, we demonstrate a new approach based on the use of functional separators that include poly(DVB‐4VP) acid‐scavenging resin. The fact that acidic species are trapped by the active separator enables formation of thin, compact, and highly passivating surface films on the graphite anodes, resulting in enhancement of LNMO/graphite cells performance.