Boosting the Redox Kinetics of High-Voltage P2-Type Cathode by Radially Oriented {010} Exposed Nanoplates for High-Power Sodium-Ion Batteries

High-voltage P2-type cathode with large capacity, high air stability, and low cost has attracted extensive attention. However, large ionic radius of Na+ and Na+/vacancy ordering result in low reaction kinetics and poor high-rate capability. Herein, cobalt-doped hierarchical structure assembled by radially oriented {010} exposed nanoplates is developed. With radially oriented grains infiltrating from surface to interior, all the {010} exposed surfaces are electrochemically active planes, and Na+ ions diffuse directly into electrolyte without passing through grain boundaries, building up 3D transfer channels. The trivalent cobalt substitution suppresses unwanted Na+/vacancy ordering and increases energy barrier of the phase transition from P2- to O2-type oxide. These synergetic effects remarkably boost the redox kinetics of high-voltage P2-type cathode. Consequently, a large reversible capacity of 112 mAh g(-1) is achieved even at 20 C, indicating excellent high-rate capability. The absence of P2-O2 phase transition also gives rise to superior cycling stability, maintaining a capacity retention of 85% after 200 cycles. In addition, full cells composed of this hierarchical P2-type cathode and hard carbon anode deliver high energy- and power-densities. These achievements offer a new insight into boosting redox kinetics of P2- and O3-type layered cathodes for high-power sodium-ion batteries.

Automated summary

A cobalt-doped hierarchical structure assembled by radially oriented {010} exposed nanoplates has been developed, which significantly boosts the redox kinetics of high-voltage P2-type cathode by enabling direct diffusion of Na+ ions into the electrolyte, building up 3D transfer channels.