Facile self-templated synthesis of P2-type Na0.7CoO2 microsheets as a long-term cathode for high-energy sodium-ion batteries

Abstract

Sodium-ion batteries are one of the most promising candidates for large-scale energy storage systems due to the low cost of sodium source and their similar working principle to lithium-ion batteries. However, the demerit of poor cycling stability of the cathode severely restricts the advancement of sodium-ion battery-based practical applications. Herein, we report a facile self-template-directed two-step strategy to fabricate microsheet-like P2-type Na_0.7CoO₂ with greatly enhanced high rate cycling stability when applied as a cathode for SIBs. Specifically, it can deliver a high specific capacity of 137.7 mA h g⁻¹ at a current density of 10 mA g⁻¹ and exhibits impressive long-term cycling stability, with a capacity retention of 94% after 1000 cycles at a high rate of 500 mA g⁻¹; this performance is outstanding compared with previous results for layered metal oxide cathodes. More importantly, a sodium-ion full cell based on the P2-type Na_0.7CoO₂ microsheet cathode was further built to demonstrate its possibilities for practical applications, where inspiring results can be observed, with promising cycling stability and high power/energy densities. This study demonstrates the great potential of layered metal oxide cathodes in practical applications, which can help advance grid-level energy storage systems.