Study On Efficient Purification And Electrochemical Potassium Storage Properties Of Cryptocrystalline Graphite

In response to the cryptocrystalline graphite’s problems of delayed research and development in beneficiation and purification,together with backward deep processing technology,this work adopts a combined physical and chemical purification method:multi-stage grinding-flotation supplemented by a mixed acid leaching method to purify cryptocrystalline graphite,which greatly reduces the process cost,energy consumption and environmental pollution.Furthermore,in the context of today’s growing demand for energy,coupled with the shortage and uneven distribution of lithium resources,the purified cryptocrystalline graphite is used as anode material for potassium ion batteries（PIBs）to enhance the high-value-added application of coal-based mineral resources.To further improve its potassium storage performance,MG will be modified by Fe Cl₃intercalation and biochemical fulvic acid-derived amorphous carbon coating,respectively,and explores the mechanism of potassium storage in composites.It will expand ideas for the development of high performance PIBs anode materials and the application of cryptocrystalline graphite for high added-value products.（1）Based on the cryptocrystalline graphite’s structural characteristics of the disordered stacking of tiny graphite lamellar and the complex symbiosis of impregnated gangue minerals in ore,the tailings were firstly discarded by roughing to reduce the grinding burden,and secondly the concentrate was re-elected in multiple stages to reduce the disturbance of gangue entrainment behavior.Using a two-stage grinding-flotation process,tailings with the yield of 9.29%and ash content of 81.86%were discarded,and the concentrate with the yield of 62.25%and ash content of 11.70%was obtained.After mixed acid leaching,the MG final product has an ash content as low as0.63%.（2）A composite anode material（MG-GIC）with FeCl₃ intercalated MG was designed using the molten salt method.The insertion of Fe Cl₃ between the MG layers can expand the graphite layer spacing,and the distorted carbon layer and isotropic structures of MG can suppress the Fe Cl₃ dissolution shuttle problem.During electrochemical potassium storage,the synthetic MG-GIC material exhibited high multiplicative performance(68.9 m Ah g^-1 specific capacity at a current density of 2 A g^-1)and a much higher K ion diffusion coefficient(10^-2/10^-8 cm² s^-1)than MG,indicating a faster charge transfer capacity and reaction kinetics during the K⁺embedding phase.（3）The low-cost biochemical fulvic acid-derived amorphous carbon（BFAC）is employed to composite modify the cryptocrystalline graphite（BFAC@MG）by a simple mixed carbonization strategy.The BFAC smooths split-layer and fold on the surface of MG and builds the heteroatom-doped composite structure,which effectively alleviates the volume expansion caused by K⁺electrochemical de-intercalation processes,together with improving electrochemical reaction kinetics.As expected,the optimized BFAC@MG-0.5 exhibits superior potassium-ion storage performance,which delivers a high reversible capacity(623.8 m A g^-1),excellent rate performance(147.8 m A g^-1 at 2 A g^-1),and remarkable cycling stability(100.8 m A g^-1 after 1200cycles).As a practical device application,the potassium-ion capacitors（PICs）are assembled using the BFAC@MG-0.5 anode and commercial activated carbon（AC）cathode,which exhibits a maximum energy density of 126.48 Wh kg^-1 and superior cycle stability.The thesis has 52 figures,11 tables,and 137 references.