Preparation Of Hollow Tin-based/carbon Composites And Their Lithium Storage Properties

The worldwide interest in sustainable energy is increasing rapidly,which requires the continuous development of stable energy storage devices.In the field of electrochemical energy ’storage,LIBs as a promising advanced technology due to its high volumetric/gravimetric energy density,high stability,and extremely low self-discharge characteristics.However,due to the low theoretical capacity of the traditional LIBs,its practical application still cannot meet the needs of the current long range electric vehicles.Therefore,the improvement of the nanostructure of the anode materials and the design of new LIBs anode materials are the prerequisite to meet the demand of future energy storage applications.Tin-based materials are prospective electrode materials for LIBs due to their high lithiation ability.However,in order to really play its role,tin-based materials must overcome their limitations such as poor electrical conductivity,low Coulombic efficiency,volume expansion during charging/discharging,and easy agglomeration of tin particles.It is found that:（1）the combination of tin-based material and carbon matrix can not only improve the electrical conductivity of the material,but also effectively solve the problem of large volume change during charge/discharge process;（2）different morphology design strategies can be used to increase the structural stability.Therefore,in this paper,hollow tinbased/carbon composites with different morphologies were synthesized by combining the above two strategies for LIBs anode,which overcame the limitations of pure tin-based materials to a certain extent and improved their lithium storage performance.The specific research contents are as follows:1.Develop a type of SnO₂ hollow nanosphere that can be easily synthesized at low temperature,and then conduct dopamine-coated and carbonized treatment to synthesize the N-doped carbon-coated SnO₂ hollow nanospheres（NC@SnO₂ HNSs）composite material,and apply it to the anode of LIBs.The large cavity ratio of the composite（73.8%）can cope with the strain relaxation and the improvement of the conductivity of pure material by the carbon layer,resulting in excellent electrochemical performance.At the same time,the impedance information and reversible capacity distribution of the battery at different stages of the cycle were analyzed,and the capacity contribution mechanism of the composites was clarified.2.Using solid CuSn（OH）₆ nanorods as template,special nanotube-like structure SnO₂ was synthesized by hydrothermal reaction in acetic acid solution,and then dopamine coating and carbonization treatment were carried out to obtain N-doped carbon coated porous SnO₂ nanotube composites（SnO₂/C NTs）.When applied to LIBs,the composites show improved lithium storage properties.The electrochemical performance test showed that the SnO₂/C NT electrode significantly improved the performance of the pure SnO₂ nanotube electrode without destroying the original lithium storage mechanism.3.Using solid CuSn（OH）₆ nanorods as template and thiourea as sulfur source,hollow nanocapsule-like Cu3SnS4/Cu2SnS3 composites（CTS HNCs）were synthesized by solvothermal method,followed by dopamine coating and carbonization treatment,the Ndoped carbon coated Cu3SnS4/Cu2SnS3 composites（CTS/C HNCs）were finally prepared.When test its lithium storage performance,it was found that the electrode has excellent electrochemical performance.To analyze the morphology and structural advantages of products,and combined with the EIS and the characterization results of electrode after cycling,the enhanced lithium storage mechanism of CTS/C HNCs was clarified.