Tuning the rate performance in O2-type layered manganese-based oxides through cobalt doping

Lithium-rich manganese-based cathode materials Li[Li_<i>x</i>Ni_<i>y</i>Mn_{1-<i>x</i>-<i>y</i>}]O₂ have received considerable attention. However, severe voltage decay and structural distortion of O3-type layered oxides hinder further practical applications. O2-type layered cathode materials can restrict the movements of transition metals and effectively suppress the voltage decay. However, O2-type layered oxides are fundamentally limited by inferior rate performance. Herein, we introduce cobalt into the TM layer in the O2-type oxide, Li_0.80[Ni_0.25Mn_0.66Co_0.02□_0.07]O₂ (□ represents vacancy, O2-LNMCO), which increases the electronic and ionic conductivity, improving the Li⁺ diffusion kinetics. Significantly, O2-LNMCO exhibits excellent rate properties, delivering a discharge specific capacity of 145 mAh g^-1 at 5 C and 111.6 mAh g^-1 at 10 C. Furthermore, the voltage decay of O2-LNMCO was restrained with an attenuation rate of 2.23 mV per cycle.