Design And Synthesis Of Cobalt/Bismuth Based Carbon Composite Materials For Battery

Lithium-ion batteries are widely used in people’s daily lives.With the increasing demand in various fields,the development of lithium-ion batteries is now facing major challenges.At present,the problems that need to be solved include improving the specific capacity of lithium-ion batteries,improving rate performance,enhancing stability in different environments and longer cycle life.Sodium has similar physicochemical properties.such as abundant reserves,obvious cost advantages and suitable oxidation-reduction potential.Currently,Sodium-ion batteries can be used as an alternative to lithium-ion batteries in some conditions.However,due to the larger radius of sodium ions,sodium ions can not be intercalated and extracted on graphite,so the commercially graphite electrodes commonly used as anode material are not suitable for Sodium-ion batteries.Therefore,designing and preparing high-energy-density and long-cycling-life sodium/lithium-ion battery anode materials has become a current issue that needs to be addressed.This article investigates the effect of different material composites and element doping on anode of alkali metal ions through the preparation of cobalt-based and bismuth-based carbon composite materials.CoON material with uniform distribution of nitrogen and oxygen atoms was prepared by solvothermal method.Subsequently,sodium citrate was used as a complexing agent and carbon source to successfully disperse CoON nanoparticles uniformly and form a carbon layer on their exterior.The existence of Co-O-N bond in the material was confirmed by high-resolution transmission electron microscopy,XRD,XPS,and Raman testing.The influence of carbon coating structure and N^3-in the material on lithium storage performance was investigated.The carbon coating structure can effectively disperse CoON nanoparticles and solve the problem of volume expansion during charging and discharging.The theoretical calculation proves that the addition of N element can effectively improve the poor intrinsic conductivity of cobalt oxide materials and enhance lithium storage performance.CoON@C maintains a lithium storage capacity of 1054 mAh g^-1 after 450 cycles at a current density of 0.5 A g^-1.CoNiB nanosheets were prepared by reducing Co²⁺and Ni²⁺with sodium borohydride,and then carbon nanotubes were used as the carbon skeleton to form a three-dimensional conductive network structure with CoNiB nanosheets.The three-dimensional structure can effectively provide more buffer space for the volumetric expansion of CoNiB,while providing more paths for the migration of ions.The bimetallic synergistic effect of Co and Ni can effectively weaken the strong covalent bond of B,which is more conducive to the insertion and extraction of lithium/sodium ions.CoNiB@C exhibits excellent lithium/sodium storage performance.At a current density of0.1 A g^-1,the first cycle charge/discharge specific capacity of sodium storage is 517.7 mAh g^-1/780.6 mAh g^-1.The rod-like Co-Bi MOF material was prepared by one-step hydrothermal method,and its bimetallic selenide heterostructure CoSe₂/Bi₂Se₃@C was obtained by high-temperature selenization.The composite material maintains a rod-like morphology.Bi₂Se₃ can form a bimetallic selenide with CoSe₂ and constitute a heterostructure.Heterostructures can induce stronger built-in electric fields at the two-phase interface to accelerate the migration of sodium ions,providing more reactive sites.In addition,the encapsulation effect of MOF-derived carbon rods has effectively solved the problem of volume expansion of selenide,improving the stability of the electrode.The two-dimensional structure of BiFeO₃ was utilized to prepare a layered heterostructure of bimetallic selenide FeSe₂/Bi₂Se₃@C material through selenization annealing treatment.The introduction of FeSe₂ component can form bimetallic selenide with Bi₂Se₃,while constituting a multi-interface heterostructure.The existence of the layered heterostructure in the material was confirmed by electron microscopy characterization,XRD and XPS.Compared to ordinary heterostructures,the layered heterostructure can expose more heterogeneous interfaces,providing more active sites for sodium storage reactions and faster ionic conductivity.On the one hand,the carbon shell formed by dopamine offered protection to the electrode and mitigated the impact of volume expansion.On the other hand,the synergistic effect of double metal selenides promotes the rapid sodium storage reaction.FeSe₂/Bi₂Se₃@C exhibits excellent lithium/sodium storage performance.At a current density of 1 A g^-1,the sodium storage capacity remained at 359.8 mAh g^-1 after 500 cycles.