Preparation And Electrochemical Properties Of TiO₂/Sunflower Seed Husk-Based Carbon Composites

In view of the ongoing depletion of non-renewable energy sources and the environmental problems of global warming,the transition from petroleum-powered vehicles to electric vehicles is an inevitable trend.The first challenge in making the transition is to develop high-performance lithium-ion batteries.Currently,the commercial anode material of lithium-ion batteries is mainly graphite,which has low cost,abundant resources,high structural stability,and good electrical conductivity.But it can only reach a theoretical capacity of 372 m A h g^-1,which is difficult to satisfy the needs of current society.Among carbon anode materials,carbon materials prepared from biomass carbon can not only enable the reuse of agricultural waste but also provide a new direction for the development of new energy sources.Titanium dioxide stands out from many materials due to its non-toxicity,high stability,and superior reversible cycle performance.However,it has low electrical conductivity,slow lithium ion transport rate,and poor lithium storage performance.Therefore,in this paper,waste sunflower seed shells were used as the carbon source and compounded with TiO₂ which have different crystal structures to prepare anode materials for lithium-ion batteries.The use of biomass carbon material as the skeleton can effectively improve the electrical conductivity of TiO₂.The cross-linked structure of the two materials can shorten the transport path of lithium ions and increase their transport rate.The excellent reversible cycle performance was maintained while the theoretical capacity was increased.Meanwhile,the reuse of the agricultural waste had brought double savings in resources and costs.Then,a series of tests were conducted to investigate the micromorphology and electrochemical performance of the produced anode materials.The main research contents and conclusions are as follows:（1）Choose sunflower seed husk as the source of carbon.And（NH₄）₂S₂O₈ was used as catalyst.Sunflower seed husk based carbon nanospheres were prepared by hydrothermal method.Nano-sized hollow TiO₂ was obtained without any additives by using TBT as the titanium source.The hollow titanium dioxide particles were successfully embedded into the carbon sphere skeleton uniformly by hydrothermal composite method to form a stable complex structure.In this paper,the effects of three hydrothermal times and three material ratios on the morphology and properties of the composites were investigated separately.Through analysis,when the hydrothermal time was 36 h and the material ratio was 7:3,after500 cycles at a rate of 5 C(1 C=310.8 m Ah g^-1),the specific discharge capacity of the anode material still steadily maintained at 308 m A h g^-1.（2）Anatase TiO₂ precursor was prepared with TBT as the titanium source,and then compounded with the sunflower seed husk based carbon nanospheres by one-step hydrothermal method so that TiO₂ nanoparticles can grown directly on carbon spheres.In order to verify the effect of hydrothermal time on the material properties,three hydrothermal times were set for comparison in this paper.In addition,comparative experiments were conducted using commercial P25 TiO₂ particles for the preparation of composites,with the aim of investigating the superiority of the one-step hydrothermal method and the necessity of the experimental synthesis of titanium dioxide.Tested and found that when the hydrothermal time was 24 h,the cycling performance of the anatase TiO₂/carbon nanosphere composite was better than that of the P25 TiO₂/carbon nanosphere composite.The specific discharge capacity after 100 cycles at the 0.2 C rate was 895.3 m A h g^-1 with a more stable composite structure.