Reasonable intrinsic microstructure of microcrystalline graphite for high-rate and long-life potassium-ion batteries

Abstract

Carbon materials, including non-graphite carbon and graphite have been extensively studied as anode materials for Potassium-ion batteries (PIBs). However, due to the slow kinetics of potassiation, it is still challenging to obtain anode materials with rate capability, good stability and low price. Microcrystalline graphite (MG) possesses ordered graphene layers and abundant interparticle voids and correspondingly undergoes a surface adsorption behavior at first and then the intercalation of K+ at low potential, which is conductive to high energy density. In addition, the larger interplanar spacing of MG with suitable crystalline size can stand for the fluctuation of interlaminar spacing caused by repeated K+ bombardment because strain in such structure can be relaxed due to sufficiently available free space. When used as anode material of PIBs, microcrystalline graphite can deliver a high reversible capacity of 249 mAh g−1 at 100 mA g−1 after 100 cycles in a readily-available electrolyte of 0.8 M KPF6 in EC/DEC (1:1 vol%), which offer a significant cost-saving opportunity. Furthermore, compared to flake graphite and soft carbon, MG exhibits the highest capacity of 139 mAh g−1 at 500 mA g−1 after 500 cycles. Our investigations will greatly promote the MG's industrial development in China.