Near-surface reconstruction in Ni-rich layered cathodes for high-performance lithium-ion batteries

The instability of the Ni-rich layered cathode materials in lithium-ion batteries is attributed to their labile surface reactivity. This reactivity induces the formation of residual lithium impurities on the cathode surface and severe side reactions with the electrolyte. Here we propose a washing process using Co-dissolved water for simultaneously removing residual lithium and forming a protective coating on Ni-rich layered cathodes. The washing induces the reconstruction of the near-surface structure through reactions with the residual lithium compounds, thereby preventing direct contact between the electrolyte and the Ni-rich surface. An additional fluorine coating on the washed cathode impedes the decomposition of salts, preventing the by-products from triggering autocatalytic side reactions at the electrolyte–cathode interface and thereby suppressing gas generation during cycling. The combination of these near-surface reconstructions synergistically extends the cycle lives of Ni-rich cathodes and satisfies the requirements concerning energy density, durability and safety for next-generation batteries in practical applications.