Preparation And Electrochemical Performance Of Hard Carbon Materials Based On Resorcinol Formaldehyde Resin

Hard carbon materials are highly disordered structures,and the graphite-like crystallites stacked have no orientation in disorder,which forming cross-linked structures with a good stability performance.So the hard carbon materials are the good choice for anode materials of lithium ion batteries and sodium ion batteries.This paper uses the resorcinol and formaldehyde with ammonia catalysis as precursors to synthesize resorcinol formaldehyde resin.Then we use resorcinol formaldehyde resin-derived from hard carbon materials as anode materials for sodium ion batteries,investigating the electrochemical performance of sodium ion batteries at different carbonization temperatures,and exploring the storage mechanism of sodium ion batteries.In addition,we also dopes SiO₂ into resorcinol-formaldehyde resin-based hard carbon for modification,then synthesized the RFHC/SiO₂ composite materials to as the anode materials of lithium ion batteries,investigating the electrochemical performance of the composite materials.We used resorcinol-formaldehyde resin-based hard carbon as anode materials for sodium ion batteries,and carbonized the precursors at different temperatures to obtain a series of hard carbon materials?RFHC-x,x is the carbonization temperatures?.The results show that RFHC-1100 has suitable microstructure and interlayer spacing,showing excellent sodium storage performance.The reversible capacity is 321m Ah/g at the current density of 20m A/g with the initial Coulomb Efficiency of 82%.And the remaining capacity is 281m Ah/g after 200 cycles with the capacity retention rate of86%,demonstrating good cycling performance.Moreover,the storage mechanism of sodium ion was discussed through GITT test,which the adsorption of micropores and defects in the slope and the insertion/deinsertion of graphite layers in the platform.In addition,in order to improve the electrochemical performance of resorcinol-formaldehyde resin-based hard carbon materials in lithium-ion batteries,we doped the silicon dioxide to modify the hard carbon materials.Compared with resorcinol-formaldehyde resin-based hard carbon materials,the synthesized composite material?RFHC/SiO₂?has excellent lithium storage properties.When the silica content is 5%,the reversible specific capacity achieves 850m Ah/g at a current density of 50Ma/g,which is more than three times that hard carbon materials,and it also exhibits good cycle stability.