Preparation Of Biomass-derived Carbon-based Materials And Its Electrochemical Energy Storage Properties

Commercialized lithium-ion batteries usually use graphitized carbon material as the negative electrode.Due to their shortcomings such as low theoretical capacity,poor rate performance,and small diffusion coefficient,they have been unable to meet the rapid development of electronic equipment and electric vehicles.The transition metal phosphide has attracted much attention due to its advantages such as high theoretical specific capacity and low redox voltage.But there are also shortcomings such as large volume expansion,poor conductivity and complicated preparation process.Generally,carbon-coated metal phosphide nanoparticles are an effective method to solve the above problems.Biomass is widely used in the preparation of carbon/carbon-based materials due to its advantages of abundant natural resources,low cost,and environmental friendliness.In this paper,soybean and silkworm cocoons are used as carbon sources to prepare heteroatom-doped herarchical porous carbon materials and silk fibroin-based porous carbon nanosheets supporting core-shell structure Ni₂P and Co P nanoparticle composite materials,respectively,and use them for lithium?sodium?ion battery negative electrode material.The details are as follows:1)Biomass soybean milk is chosen as the precursor to construct N,O co-doped interconnected 3D porous carbon framework via two approaches by using soluble salts?Na Cl/Na₂CO₃ and Zn Cl₂/Mg₅?OH?₂?CO₃?₄,respectively?as hard templates.This heteroatom doped hierarchical porous nanostructure expands the interlayer spacing of the carbon material,provides more active sites,and is more conducive to lithium/sodium storage.For HPHC-a,the specific capacity for lithium storage is710 m Ah·g^-1 and 210 m Ah·g^-1 for sodium storage,at 0.1 A·g^-1;as for HPHC-b,the specific capacity of lithium storage is 600 m Ah·g^-1 at 0.1 A·g^-1.Compared with HPHC-b,HPHC-a has more excellent lithium and sodium storage electrochemical performance mainly due to the honeycomb-like structure containing graphene-like nanosheets and high nitrogen content in the porous structures.2)Using the unique self-assembly characteristics of silk fibroin and the chelation between Ni/Co ions and silk fibroin chain,a silk fibroin-based porous carbon nanoplate supporting core-shell structure nanoparticle composite was successfully prepared?Ni₂P?NPPCP/Co P?NPPCP?.This preparation method is simple and economical and does not require secondary phosphating.When it is used as the negative electrode of a lithium ion battery,the Ni₂P?NPPCP electrode material has a specific capacity of 609 m Ah·g^-1 after 120 cycles at of 0.1 A·g^-1.However,the Ni₂P electrode without porous carbon nanoplate derived from silk fibroin decays rapidly after the initial cycle,indicating that Ni₂P?NPPCP has very good cycle stability.Meanwhile,at 0.1?0.2?0.5?1 and 2 A·g^-1,their specific capacities are 567?450?395?341 and 283 m Ah·g^-1,respectively,and when the current density is from 2 A·g^-1 returns to 0.1A·g^-1,the discharge specific capacity reaches 623 m Ah·g^-1,which indicates that the material has excellent rate performance.Co P?NPPCP electrode material,the specific capacity is stable at 685m Ah·g^-1 after 270 cycles at 0.1 A·g^-1,and at 0.1?0.2?0.5?1 and 2 A·g^-1,the specific capacity is 729?546?440?369 and 304 m Ah·g^-1,when the current density returns from 2 A·g^-1 to 0.1 A·g^-1,the discharge specific capacity reaches 625 m Ah·g^-1,which shows that the Co P?NPPCP has excellent cycle and rate performance.