Sulfur-doped carbon nanosheets as anode materials with high potassium ion storage performance

Potassium-ion batteries (PIBs) are emerging as a viable alternative to lithium-ion batteries due to the abundance of potassium resources and a standard electrode potential of K + /K close to that of Li + /Li. However, the larger ionic radius of K + induce huge volume change of electrode materials and slow electrochemical kinetics, significantly limiting the K + storage capacity and cycling stability of PIBs. Herein, S-doped porous carbon nanosheets (S-PCNs) are prepared by a facile direct sulfuration method. The S-PCNs-500 possesses high sulfur doping level of 9.1 at.% composed of covalent sulfur (C-S-C), oxidized sulfur, and some trapped molecular sulfur. This sample exhibits excellent potassium ion storage performance as anode material of PIBs, such as high capacity of 448 mAh g −1 at 0.05 A g −1 , high-rate capability of 180 at 10 A g −1 , and long cycle life with 252 mA h g −1 at 1 A g −1 after 1200 cycles. A full cell with a S-PCNs-500 anode and K 0.4 Mn 0.9 Li 0.1 O 2 0.33H 2 O cathode delivers a reversible capacity of 160 mAh g −1 at 0.1 A g −1 , responding to an energy density of 306.4 Wh kg −1 . These characteristics are attributed to the reversible intercalation of K + into the expanded carbon layers, pseudocapacitive K + sorption at structural chemical defects, and reversible electrochemical reaction between K + and C-S-C.