Preparation And Lithium Storage Performance Of One-dimensional Perovskite Stannate/Carbon Composites As Anode Materials For Lithium Ion Batteries

In recent years,low-energy density lithium-ion batteries?LIBs?have been inadequate to satisfy the people's needs with the increasing demands of the social.Exploring novel anode electrode materials with green-environmentally friendly and high-performance has become the focus of attention in the world,due to anode materials as one of the key elements to improve the lithium storage performance of LIBs.As a new type of anode electrode material,perovskite structure stannates are regarded as potential anode materials for LIBs because of their high specific capacity,low working potential,and abundant storage capacity.However,they still face many challenges,such as agglomeration,electrode powdering and shedding caused by the large volume variation during the process of delithiation and lithiation,making the electrode unable to maintain a long cycle life.A lot of research shows that the carbon materials have high electronic conductivity,good stability,and the carbon matrix can be used as an electronic channel to enhance electrical contact,which optimizes the electrochemical performance of the electrode.In addition,a cross-linked conductive network formed by one-dimensional carbon nanostructures could contribute to enhance electron transport capabilities,and can also effectively reduce the stress caused by the volume effect during Li-insertion/extraction,greatly improving the stability of the electrode structure.Herein,CaSnO₃@C core-shell nanofibers?CaSnO₃@C NFs?and flexible ZnSnO₃/C nanofibers?ZnSnO₃/CNFs?composite membranes could be used as anode material electrodes for lithium-ion batteries.These effects of carbonization temperature,carbon content or particle content on the electrochemical performance of the nanocomposite electrode were emphatically investigated.The above composite electrodes all exhibit excellent electrochemical lithium storage capacity,benefiting from the one-dimensional nanostructure and the synergistic effect between the high conductivity of carbon materials and the large theoretical specific capacity of perovskite stannate materials.The specific research results are as follows:1.CaSnO₃ nanofibers?CaSnO₃ NFs? were first prepared by electrospinning,and CaSnO₃@C NFs were fabricated by in-situ polymerization and carbonization.CaSnO₃@C NFs exhibit excellent electrochemical performance compared with pure CaSnO₃ NFs,possibly attributing to the interaction of perovskite stannates and carbon material,which inherit the high specific capacity of one-dimensional CaSnO₃ core,the good conductivity and stability of carbon shell.With increasing the temperature of the carbonization or the carbon content in the composite fibers,the specific capacity of the CaSnO₃@C NFs electrode first increases and then decreases.CaSnO₃@C NFs with carbon content of about 28 wt% prepared by carbonization at 600? have the best electrochemical performance,the initial discharge specific capacity can reach 1102.2 mAh g^-1and the specific capacity remains at 548.8 mAh g^-1after 100 charge-discharge cycles at a current density of 100 mA g^-1.When the current density increases to 2 A g^-1,the specific capacity can still be maintained at 331.9 mAh g^-1.2.ZnSnO₃ nano-cubes?ZnSnO₃ NCs? have been first synthesized by the aqueous solution method,and a facile strategy is designed for the fabrication of ZnSnO₃/CNFs composite membranes through electrospinning,followed by carbonization.The material could be directly used as a binder-free negative electrode due to its flexible self-supporting characteristics.At the same time,ZnSnO₃ NCs are well dispersed in CNFs.The composite structure can not only form a three-dimensional conductive channel for the transportation of electrons and lithium ions,it also can increase the contact area of the electrode material and the electrolyte,shorten the diffusion path of lithium ions,and effectively alleviate the volume effect,which enhances the capacity retention rate and cycle stability of the ZnSnO₃/CNFs composite membranes electrode.With increasing the ZnSnO₃ NCs content,the specific capacity of ZnSnO₃/CNFs electrode first increases and then decreases.When its content is about 34 wt%,the corresponding composite electrode exhibits relatively good cycle and rate performance.The initial discharge specific capacity is as high as 1183.1 mAh g^-1,and it delivers a specific capacity of 582.6 mAh g^-1at the current density of 100 mA g^-1after 100 cycles.Even at a higher current density of 2 A g^-1,the specific capacity of sample can stabilize at 349.5 mAh g^-1.