"Core-shell" cathodes for high performance Li-ion batteries
Li-rich or Ni-rich layered oxides are considered ideal cathode materials for high-energy Li-ion batteries (LIBs) owing to their high capacity (> 200 mAh g–1) and low cost. However, both are suffering from severe structural instability upon high-voltage cycling (> 4.5 V). In this work, “Li-rich Ni-rich” Li1.08Ni0.9Mn0.1O2 oxides with core-shell architecture are designed and synthesized to improve their cyclability at these high-voltages. These oxides are determined to be composed of a less reactive “Li-rich Mn-rich” shell and a high-capacity “Li-rich Ni-rich” core. As Li-ions gradually enter into the core-shell precursor during the high-temperature lithiation reaction, an interdiffusion of elements across the interphase between the Mn-rich shell and the Ni-rich core successively occurs. Such thermally-driven atomic interdiffusion could lead to a thickness- controllable “Li-rich Mn-rich” shell, which can guarantee an exceptional structural reversibility for the layered “Li-rich Ni-rich” core upon long-term cycling. As a consequence, the optimized core-shell Li1.08Ni0.9Mn0.1O2 achieves a capacity retention of 96% at 0.1 C after 100 cycles in the voltage range of 2.7–4.6 V. These findings might open up a new avenue for rational design of advanced cathode materials for LIBs and beyond.