Study On Stability Of Antimony/Biomaterial Carbon Microsphere As Anode Materials For Lithium/Sodium Ion Batteries

As a clean and efficient energy storage device,lithium ion battery（LIB）has been widely used in various portable electronic devices.However,the theoretical specific capacity of commercial LIB with graphite-based carbon materials as anode materials is only 372 mA h g^-1,which cannot meet the development requirements of electric vehicles in the future.Therefore,the development of LIB anode materials with excellent electrochemical performance and study of its mechanical mechanism are of great significance for the development of LIB.In addition,the lack of lithium resources in the crust and the uneven distribution limit the application of LIB in large-scale energy storage equipment.As a new energy storage device,sodium ion battery（SIB）is expected to become a substitute for LIB in large energy storage equipment because of its wide range of raw materials and similar energy storage mechanism.Unfortunately,the anode material（graphite）of commercial LIB currently has a small interlayer spacing,and it is impossible to reversibly and efficiently deintercalate sodium ions,which limits the development of SIB.Therefore,the development of SIB anode materials with high energy density and long cycle life is necessary for the shortage of LIB in the field of large energy storage equipment.Antimony（Sb） has been widely studied as a promising anode material in LIB/SIB because of its high theoretical specific capacity(660 mAh g^-1)and a mild reaction platform.However,during the insertion and extraction of lithium/sodium ions,internal stress caused by a large volume change causes battery capacity to be attenuated,and life is shortened and eventually fails.Aiming at a series of problems in the Sb anode materials,Sb coated hollow carbon microspheres（Sb@HCMs）is designed.The effect of the hollow structure on the cyclic stress and the effectiveness of the nanomaterials to limit the stress,improve the cycle stability of the Sb anode material of the LIB/SIB,and further study the electrochemical performance of the battery under the load,and the local mechanical behavior of the anode copper before and after the cycle,it is expected to further understand the failure mechanism of the Sb anode material and enhance the electrochemical performance of the Sb-based anode material.1.Design and synthesis of Sb-anchored hollow carbon microspheres（Sb@HCMs）as anode for high-capacity and long-cycle performance of lithium-ion half-cells and lithium-ion full-cell.The material is formed by calcination of cultured yeast cells to form hollow carbon microspheres and synthesis of a Sb carbon composite on the surface thereof by reduction of SbCl₃in ethylene glycol.The anodes of the full-cells are made of Sb@HCMs and the positive electrode is composed of LiCoO₂.The energy density of Sb@HCMs//LiCoO₂ lithium-ion full cells is 47 and 118 W kg^-1 at power densities of 59 and 118 W kg^-1,respectively,and the energy density is 281.1 and146.9 W h kg^-1 at high power densities of 236 and 472 W kg^-1.The lithium-ion half-cell with Sb@HCMs as the negative electrode exhibits excellent cycle stability and high rate performance,and still has a capacity of 605 mAh g^-1 by circulating 100 times at a current density of 100 mA g^-1.The high capacity and high cycle performance of lithium ion half-cells with Sb@HCMs as anode electrodes are attributed to the morphological transition from Sb-anchored hollow carbon microspheres to yarn-spherical microspheres and one-step delithiation of Li₃Sb and Sb during the charging phase.At the same time,the effects of different types of applied loads on the stability of the battery are studied.The results show that when the applied load is plate load,the battery case acts as a protective layer,which protects the battery;when the applied load is the contact load,the battery performance is greatly affected in a very short time.2.The Na⁺ storage properties of the Sb@HCMs composites with different bio-carbon contents were studied.Available from experimental data,the Sb@HCMs-50 electrode exhibits better cycling and rate stability than Sb@HCMs-0 and Sb@HCMs-100 electrode,which can be attributed to the carbon frame（compared with Sb@HCMs-0）and the high content of Sb（compared with Sb@HCMs-100）.After 150 cycles,the Sb@HCMs-50 delivers the high reversible capacity of 464 and 454 mA h g^-1 at a current density of 0.1and 0.5 A g^-1,respectively.Even the current density reaches up to 3.2 A g^-1,the reversible capacity of 311.5 mAh g^-1 can be retained.The outstanding cycling and rate performance of Sb@HCMs-50 are associated with two aspects.One is the porous carbon frame,which can enhance the conductivity of the active material,prevent the agglomeration of Sb nanoparticles,and provide the void to buffer the large volume changes.Another is the Sb nanocrystals,which can decrease the stress during cycling and allow for more Na storage.3.The structural degradation/damage of the negative Cu current collector of different charge/discharge cycles in the Sb-based LIB is studied.The results show that the negati1ve Cu current collector will form a porous structure composed of Li、Sb and Cu crystal after electrochemical cycles,which leads to the capacity degradation of Sb anode electrode,and the local mechanical behavior of the Cu current collector is also changed:the nominal contact modulus of the porous layer formed after 1,10 and 30 electrochemical cycles is greater than that of the original Cu current collector,possibly due to the finite effect of the porous structure and the strengthening effect of the alloy.For a porous layer formed after 50 or more electrochemical cycles,the nominal contact modulus is slightly larger than the original Cu current collector,indicating that the thicker the porous structure,the smaller the nominal contact modulus.