Regulation Strategies For Closed Pores And Sodium Storage Performance Of Wood-based Biomass-derived Hard Carbon

Sodium-ion batteries are considered to be a substitute for lithium-ion batteries in the field of large-scale energy storage system due to the low cost,abundant raw materials,and high safety.However,the larger radius and molar mass of Na ions lead to slow diffusion kinetics and difficulty in intercalating into the graphite layer,limiting the commercial application of Na-ion batteries.At present,there is an urgent need to develop anode materials with a wide range of sources,low cost and excellent performance.Hard carbon has a lower working voltage and larger sodium storage capacity,and is expected to be applied in high-energy-density sodium-ion batteries.However,the structure of hard carbon is highly disordered,and the mechanism of sodium storage is unknown.Waste biomass,as a recyclable material,has potential in the preparation of anodes for high-performance sodium-ion batteries.In this paper,the structure and sodium storage properties of waste wood-based biomass-derived carbon are regulated based on the precursor structure and composition to control the structure of pyrolytic carbon.It is planned to focus on the formation and influencing factors of the closed pore structure in pyrolytic carbon,and the storage mechanism of sodium ions in the closed pore structure.Ultimately,the capacity of waste biomass-derived carbon is increased so that it can meet the requirements of full battery energy density.The specific work is as follows:（1）By removing lignin and hemicellulose components from waste rosewood,the regulation of the closed pore wall thickness and quantity of closed pores in waste rosewood-derived hard carbon was successfully achieved for the first time at a low temperature of 1100°C.When used as an anode material for Na-ion batteries,the optimized sample exhibits a specific capacity of 326 m Ah g^-1 at a current density of 20 m A g^-1,especially the plateau capacity is significantly improved.At a current density of 5000 m A g^-1,the optimized carbon material exhibits better rate capability with a specific capacity of 230 m Ah g^-1,which is significantly higher than that of the untreated sample(only 33 m Ah g^-1at 5000 m A g^-1).The significant improvement in sodium storage performance is believed to be due to the abundant closed pores providing sufficient space for sodium storage,and the thinner closed-pore walls favoring sodium diffusion in the bulk phase.（2）A strategy of sulfuric acid hydrolysis of waste wood-based biomass was designed to hydrolyze cellulose in wood to realize the regulation of precursor and pyrolytic carbon structure.Through analysis and characterization,it is found that the introduction of sulfuric acid hydrolysis will promote the fracture of cellulose,which will reduce the degree of graphitization of the pyrolytic carbon and increase the closed pores content of the pyrolytic carbon.The reversible capacity of the sample with more closed pores is 321 m Ah g^-1 at 50 m A g^-1,an improvement of about 130m Ah g^-1,and the plateau capacity accounts for 74%.When this strategy was extended to other temperatures and species,it was found to be somewhat general.