Utilization of the biowaste-derived carbon and enhancement of its electrochemical performance via doping

Grant Funding 2021-2023
Ministry of Education and Science of the Republic of Kazakhstan

To investigate and improve electrochemical performance and material characterization of biomass-derived hard carbon for sodium ion batteries. Fabrication of anode material with high theoritical capacity that can be achieved by doping, pretreatment and other methods.

Sodium-ion batteries (SIBs) have become the most viable substitute for Lithium-ion batteries (LIBs) due to the following reasons: resource advantages, reasonable cost of employed raw materials and similar electrochemical principle. Among the different anode materials for SIBs , hard carbon has been considered as a promising candidate because of its advantages of high storage capacity and stable long-term cyclability. Currently, many bio-wasted materials are recognized as an abundant and cheap carbon source that has been used to synthesize hard carbon, but the mechanism of doping effect on sodium storage and electrochemical peroformance is not fully understood.

Almond shells, walnut shells and coffee grounds were chosen to prepare hard carbon by pre-oxidation, acid activation, sulphur doping, and pyrolysis (1000-1600 ℃) under an inert (argon / nitrogen) atmosphere. The ion storage mechanisms and anode optimizations are investigated systematically. A strong correlation is discovered between the pretreatment techniques with structural properties. During the acid pretreatment, impurities were removed and the presence of heteroatoms from acids offered extra sites for Na+ adsorption. In addition, the pre-oxidation process increases the content of oxygen atoms to enhance the adsorption capacity. Indeed, increasing carbonization temeperature resulted in carbonized materials with high graphitization and change of the structure from disordered to local ordered. Moreover, biomass - derived hard carbons preserved a semi-stable structure with intergranular and microcracks due to the successive thermal treatments.