Preparation And Properties Of Coal-based Carbon Anodes Forhigh Performance Potassium Ion Batteries

Potassium ion batteries?PIBs?are expected to be a new type of energy storage device for lithium ion batteries in the field of large-scale energy storage due to their abundant raw material resources and low oxidation-reduction potential.However,due to the large radius of potassium ion,the poor rate performance and cycle stability of PIB anode is a bottleneck hindering the development of PIBs.Designing and creating high-performance,low-cost anode materials suitable for potassium ion storage is of great significance for the development of large-scale energy storage PIBs.In this paper,coal-based carbon anodes were prepared by ball-milling,acid-washing,oxidation,carbonization and liquid phase coating using low-cost and high carbon content coal as precursors.We investigated the effect of the coal ranks and synthesis parameters on the microstructures of coal-based carbons,and their correlation to the electrochemical performances.The main research contents and results are highlighted as follows:?1?Preparation and properties of high performance coal-based carbon anodes.Coal-based carbon anodes for PIBs have been successfully prepared from the medium and low rank coals with different degrees of coalification through ball-milling,acid washing,oxidation and carbonization.Due to the relatively ordered carbon clusters with enlarged interlayer spacing,the middle-rank bituminous coal-based carbon anode?B₁-A-900?delivers a high reversible capacity of 260 mAh g^-1 at 0.05 A g^-1,even at higher current densities of 5.0A g^-1,it maintains high storage capacities of 88 mAh g^-1.When the current density switches back to 0.05 A g^-1,the capacity recovers to 232 mAh g^-1 with the rate capacity retention of89.2%.The capacity retention reaches 68.6%after 1200 cycles at 1 A g^-1.?2?Surface coating modification of coal-based carbon anodes.Phenolic resin and pitch were mixed with coal-based carbon anode B₁-A-900 to prepare coated coal-based carbon anodes.After coating,the specific capacity decreased slightly,but the cycle stability and rate performance were improved.Coated coal-based carbon anode with phenolic resin content of10%?B₁-A-900@PR-10%?delivers a high reversible capacity of 225 mAh g^-1 at 0.05 A g^-1,even at higher current densities of 5.0 A g^-1,it maintains high storage capacities of 85 mAh g^-1.When the current density switches back to 0.05 A g^-1,the capacity recovers to 208 mAh g^-1.The rate capacity retention after coating increased from 89.2%to 92.4%.It maintained 94mAh g^-1 at 1 A g^-1 after 1200 cycles with the capacity retention of 72.3%,even if after 1800cycles,the specific capacity was maintained at 86 mAh g^-1 with the capacity retention of66.2%.The outstanding rate performance and cycle stability of B₁-A-900@PR-10%are attributed to the stable hard carbon coating surface,which can effectively alleviate the deformation and collapse of coal-based anode materials during cycling.