Reducing structural degradation of high-voltage single-crystal Ni-rich cathode through in situ doping strategy

摘要

Polycrystalline Ni-rich layered oxide (Li Ni_(x)Co_(y)Mn_zO_(2)(NCM),x>0.8) cathode material with high specific capacity and low cost is considered as one of the most promising candidate materials for lithium-ion batteries (LIBs).However,it suffers from severe structural and capacity degradation during practical cycling,especially under harsh operation condition(ultrahigh cutoff voltage and elevated temperature,etc.).One promising approach to mitigate these issues is to develop a single-crystal Ni-rich NCM cathode,which could enhance structural integrity and improve capacity retention,due to its robust and stable micro-sized primary particles.However,the improved cyclic stability comes at the expense of reversible capacity and rate capability,owing to the relatively low Li^(+) diffusion efficiency for its micron-sized primary particles.Moreover,the structural degradation and exacerbation of interfacial reactions for the Ni-rich NCM cathode under highvoltage (≥4.5 V) would quickly trigger the poor electrochemical performance,limiting its practical applications.Herein,Li Ni_(0.827)Co_(0.11)Zr_(0.003)Mn_(0.06)O_(2)(Zr@SC-N_(83)) cathode material was successfully synthesized via the in situ doping strategy.It could not only effectively maintain the reversibility of phase transition between H2 and H3 after long-term cycling at high voltage (4.6 V),but also enhance lithium-ion diffusion,thus improving the cycling performance and good rate performance for the Zr@SC-N_(83)cathode.As a result,0.3 wt%Zrdoping cathode delivers an initial discharging capacity of 200.1 m Ah·g^(-1)at 1.0C and at the high cutoff voltage of 4.6 V,exhibiting the satisfactory capacity retention of 85.5%after 100cycles.It provides an effective route toward low-cost and higher energy density for lithium-ion batteries with Ni-rich cathode.