Abstract
Potassium-ion batteries are a promising alternative to lithium-ion batteries. However, it is challenging to achieve fast charging/discharging and long cycle life with the current electrode materials because of the sluggish potassiation kinetics. Here we report a soft carbon anode, namely highly nitrogen-doped carbon nanofibers, with superior rate capability and cyclability. The anode delivers reversible capacities of 248 mAh g–1 at 25 mA g–1 and 101 mAh g–1 at 20 A g–1, and retains 146 mAh g–1 at 2 A g–1 after 4000 cycles. Surface-dominated K-storage is verified by quantitative kinetics analysis and theoretical investigation. A full cell coupling the anode and Prussian blue cathode delivers a reversible capacity of 195 mAh g–1 at 0.2 A g–1. Considering the cost-effectiveness and material sustainability, our work may shed some light on searching for K-storage materials with high performance.
Highlights
Potassium-ion batteries are a promising alternative to lithium-ion batteries
Liu et al conducted an in situ study of the electrochemically driven potassiation of an individual carbon nanofiber consisting of a bilayer wall with an outer layer of nongraphitic soft carbon enclosing an inner layer of graphitic carbon[20]
The precursor was synthesized by an oxidative template assembly approach[30]
Summary
Potassium-ion batteries are a promising alternative to lithium-ion batteries. it is challenging to achieve fast charging/discharging and long cycle life with the current electrode materials because of the sluggish potassiation kinetics. Jian et al.[16] and Luo et al.[17] demonstrated that electrochemical procedure can be used to achieve KC8 (stage 1) potassiation and reversible depotassiaion in graphite, generating a capacity of ~250 mAh g−1 at a low rate (≤C/10, 1C = 279 mA g −1). Other graphitic materials such as reduced graphene oxide[17] and polynanocrystalline graphite[19] have been examined for K-storage. The N-doped hard carbon microspheres reported by Chen et al exhibited high-rate capability, enabled by the surface-driven K-storage[29]. Given the advantages of soft carbon over graphitic and hard carbon in PIBs16, it is of high importance to study the N-doped soft carbon and the correlation of N-doping species to K-storage performance
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