Additive engineering for robust interphases to stabilize high-Ni layered structures at ultra-high voltage of 4.8 V

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. Severe capacity decay at high voltages prevents the application of Ni-rich layered oxide cathodes. Here the authors report an electrolyte additive in a common commercial electrolyte that enables stable cycling at an ultra-high voltage of 4.8 V.