Preparation And Performance Of Tin Oxide Composite Sunflower Seed Shell Porous Carbon Anode Material

China has put forward the goal of"carbon peaking and carbon neutrality"in 2020.In order to achieve the replacement of petroleum fuels,electric vehicles have developed by leaps and bounds in nearly years,which makes the requirements for all aspects of power storage devices increasingly high.Lithium-ion batteries are applied in a wide range of applications such as grid storage,electric vehicles and portable electronics due to their long cycle life,high power density and high energy density.As an indispensable core component of lithium battery,excellent anode material can greatly improve the performance of lithium-ion battery in all aspects.Graphite as the anode material for traditional lithium-ion batteries is still far from adequate for practical applications,and its theoretical capacity is only 372 m Ah g^-1,which does not comply with the high-capacity requirement for lithium-ion batteries,and the gap is still large.In order to solve this problem,other types of anode materials have been discovered,such as tin oxide（SnO₂）,which has a much higher theoretical specific capacity(782 m Ah g^-1).However,the commercialized of tin oxide anode still faces great challenges,because it is subject to a massive volume expansion caused by lithiation/de-lithiation during cycling,resulting in significant capacity attenuation.To overcome this drawback of SnO₂,the strategy of nanosizing and preparing SnO₂ with a solid morphology is proposed,which greatly improves the structural stability of the material and is helpful to obtain fast reaction kinetics.Meanwhile,the SnO₂ nanomaterials were compounded with porous carbon materials with porous lithium-embeddable sites to further limit the volume expansion and significantly improve the cycling stability of anode electrode materials.In this paper,sunflower seed shell biomaterials from a wide range of sources were introduced as carbon sources to prepare different morphologies of SnO₂ and sunflower seed shell porous carbon composites to construct anode electrode materials for lithium-ion batteries.The main work is as follows:（1）Firstly,the activation ratios of sunflower seed shell porous carbon（SSSC）were studied.Sunflower seed shell porous carbon was prepared after pre-carbonization at 300℃with Na₂CO₃ at the mass ratios of 1:1,1:2 and 1:4.The analysis revealed that the sunflower seed shell porous carbon with the activation ratio of 1:2 had the best structure and the electrochemical performance was more outstanding compared with the other two activation ratios,and its discharge specific capacity could be stabilized at 786.12 m Ah g^-1 after 100 cycles at 0.2 C,thus obtaining the best activation ratio.Secondly,hollow dense SnO₂ hollow balls（SnO₂ HB）were prepared,and SnO₂ HB was compounded with activated SSSC at the ratio of1:2 using the solvothermal method to obtain SnO₂ HB@SSSC,and the electrochemical properties of SnO₂ HB compounded with SSSC at different mass ratios（1:1,1:2,2:1）were investigated.The electrochemical performance of SnO₂ HB@SSSC with a 1:2 composite ratio was found to be the best,and its discharge specific capacity could be stabilized at 1107.63m Ah g^-1 after 100 cycles at 0.2 C.（2）Sn-MOF was calcined in air to obtain tin oxide nanoparticles（MOF-SnO₂ NP）at the size range of 10-20 nm using a tin-based metal-organic framework（Sn-MOF）as a precursor.The MOF-SnO₂ NP was compounded with SSSC to obtain MOF-SnO₂ NP@SSSC at 200℃,and the effect of reaction time and temperature on the performance of the material was investigated.At 0.2 C,the discharge capacity was stabilized after 100 cycles at 1107.5mAh g^-1.