Preparation And Potassium Storage Performance Of Resorcinol Formaldehyde-based Hard Carbon Spheres

Potassium and lithium are both alkali metal elements,and potassium ion batteries and lithium ion batteries have the same working principle,that is,"rocking chair" batteries.The crust reserves of potassium resources are much higher than those of lithium resources,and the cost of potassium-ion batteries can be well controlled,so it has the potential to be used as a power source for large-scale energy storage systems and electric vehicles.Hard carbon materials have a unique disordered graphite-like sheet-layer stacking structure,so they have a higher specific capacity and better cycle stability than graphite.Therefore,hard carbon materials are also a reliable choice for potassium ion battery anode materials.In recent years of research,researchers have not had a systematic and comprehensive understanding of the potassium storage behavior of hard carbon materials.This paper is based on a series of hard carbon materials with gradual differences in microstructure,characterize the structural parameters of hard carbon materials through detailed analysis and testing techniques,and establish a connection with the electrochemical performance and kinetic process of hard carbon potassium storage,further derive the structure-activity relationship of hard carbon materials for storing potassium,which has great guiding significance for improving the performance of hard carbon-based anodes.At the same time,the commercialization of highquality hard carbon materials is inseparable from the structural design and industrial production of polymer precursors,and its foundation lies in the synthesis mechanism and formulation control of the precursors,and further implementation of pilot production.The details are as follows:1.The pomegranate-like reaction intermediates in the St(?)ber synthesis process were prepared by the ice-bath slow-drop modification and acidification modified St(?)ber method,which proved that the method includes the step of agglomeration of primary particles into secondary particles during the formation of colloidal spheres,and synthesize submicron resorcinol formaldehyde resin colloidal spheres of uniform size;then,by adjusting the reaction conditions during spray drying,the large-particle colloidal spheres with high sphericity can be prepared in a controllable manner.Comparing the colloidal spheres and hard carbon spheres synthesized by the two methods,the results show that the hard carbon spheres prepared by the St(?)ber method have better potassium ion storage performance,which has a stable reversible cycle capacity of 273 m Ah/g at a low current density of 20 m A/g,and a high capacity retention rate of 33.3% at a large current density of 1000 m A/g.2.By designing an ultra-wide carbonization temperature gradient experiment from 800℃ to 2900℃,and adding a comparison of different heating rates and holding time,in this paper,a series of resorcinol-formaldehyde resin hard carbon spheres with different microstructures and structural gradual changes were prepared,and the carbonization evolution process of resorcinol-formaldehyde resin hard carbon spheres was studied based on this;In order to explore the optimal carbonization process of resorcinolformaldehyde colloidal spheres,the morphology and structure of the series of hard carbon were characterized and the performance of the negative electrode of the potassium ion battery was characterized;Then the two are connected with the kinetic process of hard carbon storage of potassium and the change of electrode structure,and the reaction mechanism of hard carbon storage of potassium is further deduced.3.Based on the synthesis principle and carbonization process of resorcinol-formaldehyde resin colloidal spheres synthesized by St(?)ber method in Chapters 2 and 3,the orthogonal experiment method is used to explore the optimal synthesis scheme of phenolic resin colloidal spheres and hard carbon spheres,and solve the problem of product separation.Finally,the stable and controllable synthesis of colloidal balls and hard carbon balls was realized,and the 10-kilogram-level pilot production was completed.The hard carbon spheres have a uniform spherical particle morphology of 700 nm,high tap density,and excellent potassium storage performance,at a current density of 20/200/500/1000/2000mA/g,it has a high reversible cycle specific capacity of 280/218/185/139/69 m Ah/g,respectively.