Pore structure and oxygen content design of amorphous carbon toward a durable anode for potassium/sodium-ion batteries

Abstract

Both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are considered as promising candidates in grid-level energy storage devices. Unfortunately, the larger ionic radii of K⁺ and Na⁺ induce poor diffusion kinetics and cycling stability of carbon anode materials. Pore structure regulation is an ideal strategy to promote the diffusion kinetics and cyclic stability of carbon materials by facilitating electrolyte infiltration, increasing the transport channels, and alleviating the volume change. However, traditional pore-forming agent-assisted methods considerably increase the difficulty of synthesis and limit practical applications of porous carbon materials. Herein, porous carbon materials (Ca-PC/Na-PC/K-PC) with different pore structures have been prepared with gluconates as the precursors, and the amorphous structure, abundant micropores, and oxygen-doping active sites endow the Ca-PC anode with excellent potassium and sodium storage performance. For PIBs, the capacitive contribution ratio of Ca-PC is 82% at 5.0 mV s⁻¹ due to the introduction of micropores and high oxygen-doping content, while a high reversible capacity of 121.4 mAh g⁻¹ can be reached at 5 A g⁻¹ after 2000 cycles. For SIBs, stable sodium storage capacity of 101.4 mAh g⁻¹ can be achieved at 2 A g⁻¹ after 8000 cycles with a very low decay rate of 0.65% for per cycle. This work may provide an avenue for the application of porous carbon materials in the energy storage field.