A Li-substituted hydrostable layered oxide cathode material with oriented stacking nanoplate structure for high-performance sodium-ion battery

Abstract

As one of the most prospective transitional metal oxide cathode materials for sodium-ion batteries (SIBs), P2-type Na2/3Ni1/3Mn2/3O2 layered oxide generally suffers from sluggish Na+ kinetics and complicated structural evolution. Here, a stable Co-free P2-Na2/3Li1/9Ni2/9Mn2/3O2 cathode material with multilayer oriented stacking nanoplates is reported, which exhibits high hydrostability realized by partial Li element substitution for Ni. A prominent rate capability (71.7% capacity retention at 5 C compared to 0.2 C), an excellent cycling stability (78.7% capacity retention at 2 C after 300 cycles) and a promoted performance even at a higher cutoff potential of 4.4 V were displayed owing to bifunctional strategy of chemical substitution coupled with structure modulation, and the as-synthesized material retains its original structure and electrochemical performance after being aged in water. Moreover, dominant Na+ capacitive storage mechanism, high thermostability and complete solid-solution reaction are explicitly elucidated through quantitative calculation of electrochemical kinetics and in-situ X-ray diffraction technique. These findings reveal the importance of rational chemical substitution and structure modulation strategy, and inspire novel design of high-performance cathode materials for rechargeable SIBs.