Bichannel design inspired by membrane pump: a rate booster for the conversion-type anode of sodium-ion battery

Abstract

The sluggish kinetics of Na⁺ in anode limits the rate capability of sodium-ion batteries (SIBs). Herein, pyrophosphate, as a Na⁺ pump in the cell membrane, is integrated with cobalt redox-active center to obtain a new type of anode material for SIBs with a high Na⁺ diffusion rate. After combining with the hierarchical carbon network, bichannel structure is formed to accelerate the transport of electrons and ions, where the carbon network serves as the transport channel for electrons and pyrophosphate for Na⁺. High conductivity of electrons and ions results in the high pseudocapacitance ratio of CPOC@C-700 (95% at 1 mV s⁻¹), indicating a high rate capability (190.3 mA h g⁻¹ at 5 A g⁻¹). A series of ex situ characterizations demonstrate the high reversibility of the redox center and stability of the bichannel structure during cycling. Consequently, CPOC@C-700 maintains 71.1% of the capacity after 1000 cycles at 2 A g⁻¹. This bichannel design concept is anticipated to promote further applications of SIBs.