Study On Construction And Electrochemical Performance Of Carbon-antimony Nanostructures As Anode Materials For Medical Lithium Ion Batteries

Lithium-ion batteries（LIBs）are widely used in various portable electronic medical equipment and large-scale medical equipment which is a clean,efficient and green new generation of energy storage devices.As an important part of lithium-ion batteries,negative electrode materials are crucial to the performance of the overall battery.At present,due to their low theoretical specific capacity(372 m Ah g^-1)and lithium intercalation potential（0.1V）,commercial graphite anodes for medical lithium-ion batteries have been unable to meet the rapid development of daily medical electronic products and large-scale medical equipment industries in energy density,power density,cycle life and safety.So it is urgent to find negative materials with low cost,high capacity,high safety and long cycle life.Biomass materials have a natural microstructure and are rich in carbon elements.Carbon materials and composite materials derived from biomass have been widely used in various energy storage devices with the advantage of low cost,low environmental protection costs,and high electrochemical performance.Therefore,by adjusting the morphology and structure of biomass carbon materials and combining with high-capacity active materials,it is of great significance to promote the development of biomass carbon materials.Among the many metal materials,antimony（Sb）is considered to be a promising negative electrode material due to its high specific capacity(660 m Ah g^-1),but the volume expansion problemit is caused by repeated deintercalation of Li⁺during the charging and discharging process,which causes the electrode material to be powdered and the structure to be destroyed,eventually the battery fails.In response to the above problems,this article designs anode materials by combining antimony with biomass-derived carbon materials,it can combine the advantages of biomass carbon and antimony,and utilize biomass carbon to solve the instability of antimony anode.Hollow porous carbon microspheres（HPCMs）,dendritic Sb nanocrystals and Sb@C composite nanotubes are designed,and the hollow structure,dendritic structure gaps and nano-sized structures are used to buffer the volume expansion and cyclic stress during the charging and discharging process.The biocompatibility and molecular chemical inertness of the negative electrode material in medical button lithium-ion battery are increased by the use of carbon-coated technology,and then to improve the stability of structure and cycle.（1）Using carbon-rich yeast cells that are low in cost and easy to cultivate as a bio-carbon template,carbon microspheres（HPCMs）obtains hollow and porous structures by high temperature carbonization.By designing the electrode material into a micron spherical structure with uniform mechanical properties,it can effectively buffer the volume expansion of the negative electrode material during charging and discharging,prevent the anisotropy during lithiation from causing structural damage to the electrode,and improve the electrode stability.The test results of the lithium ion half-cell show that the HPCMs-600 anode material has a reversible capacity of 220 m Ah g^-1after 500 cycles at a high current density of 2 A g^-1,and the reversible capacity decays are very little during the cycle（the average capacity attenuation per cycle is 0.9%）,showing good cycle performance,which provides a strong reference for the development of environmentally friendly and low-cost carbon materials.（2）Nano dendritic Sb was prepared by reducing antimony trichloride with zinc powder.The phase structure is a rhombus structure.The size of the entire dendritic structure is 300-700 nm,and the size of a single dendrite is about 50-100 nm.Both the dendritic structure and the crossing of branches form more porous voids,which can alleviate the structural expansion of the Sb nanocrystals during the process of deintercalating lithium,thereby improve the stability of the electrode.The dendritic Sb nanocrystals are used as the negative electrode material to assemble a lithium ion half-cell.The results show that after 100 cycles of current density of 0.1 A g^-1and 0.5 A g^-1,the reversible specific capacities are 517.4 m Ah g^-1and306.8 m Ah g^-1,respectively.After different cycling current densities return to the initial current density,the capacity recovery rate was 93%,indicating that dendritic Sb nanocrystals have good rate performance.This is due to the fact that the dendritic structure of Sb nanocrystals is not only conducive to the rapid transmission of ions,but also the branches of the clearance can provide a buffer space for the volume change of the antimony-lithium alloying.With LiNiCoMnO₂as the positive electrode active material,a medical button-type lithium-ion full battery is assembled,which can make small medical thermometer work to synthesize Sb₂S₃nanorods by hydrothermal reduction of biomolecule L-cystine as sulfur source with Sb Cl₃in DMF solvent at different temperatures and reaction times.The morphology,structure and electrochemical performance of nanorods was discussed under the effect of reaction temperature and time.The results show that the Sb₂S₃nanorods synthesized under the reaction conditions of 170°C and 12 h have the best morphology.The length of the nanorods is about 3-6μm,the average diameter is about 150 nm,and the structure is orthogonal phase.The battery data shows that the Sb₂S₃nanorods prepared under different conditions have low capacity and cycle stability.On this basis,the nanorods by calcining and coating carbon using polydopamine were used to successfully obtain Sb@C nanotubes with a size range of 160-240 nm and a porous carbon layer with an outer wall of 20-40 nm.And using Sb@C composite nanotubes as the negative electrode material assemble lithium-ion half-cells and full-cell batteries,the results show that the lithium-ion battery with Sb@C exhibits excellent cycle stability and high rate performance.At the current density of 100 m A g^-1after 100 cycles,it still maintains 415.2 m Ah g^-1.When the current density is 500 m A g^-1,there is still a reversible capacity of 407.3 m Ah g^-1after 100 cycles,showing excellent cycle stability and the high rate performance.This is attributed to the outer porous carbon layer can buffer effect of on volume expansion.Sb@C nanotubes are used as the negative electrode active material,and LiNiCoMnO₂is used as the positive electrode active material to assemble a medical button-type lithium ion battery,which can be used in small medical thermometer.（3）The biocompatibility study of Sb@C//LiNiCoMnO₂assembled medical button lithium-ion battery is carried out.It is concluded that the experimental group was cultured for48 h and 72 h,and the absorbance was measured by a microplate reader,the cell morphology was observed by scanning electron microscope,and the number was observed by fluorescent inverted microscope.Compared with the 24 h cell viability and number,the cells proliferated significantly,indicating that the battery has good biocompatibility.