PNNL

Abstract

Nickel-rich layered cathode materials promise high energy density for next-generation batteries when coupled with lithium metal anodes. However, the practical capacities accessible are far less than the theoretical values due to their structural instability during cycling, especially when charged at high voltages. Here we demonstrate that stable cycling with an ultra-high cut-off voltage of 4.8?V can be realized by using an appropriate amount of lithium difluorophosphate in a common commercial electrolyte. The Li||LiNi0.76Mn0.14Co0.10O2 cell retains 97% of the initial capacity (235?mAh?g–1) after 200 cycles. The cycling stability is ascribed to the robust interphase on the cathode. It is formed by lithium difluorophosphate decomposition, which is facilitated by the catalytic effect of transition metals. The decomposition products (Li3PO4 and LiF) form a protective interphase. This suppresses transition metal dissolution and cathode surface reconstruction. It also facilitates uniform Li distribution within the cathode, effectively mitigating the strain and crack formation.