Preparation Of Biomass Rice Husk Carbon And ZnO Composites And Their Lithium Storage Performance

The growing demand for sustainable energy storage systems in electric vehicles and portable electronic equipment has promoted the rapid development of high-power performance,long life and green rechargeable lithium-ion batterie.However,the theoretical capacity of graphite anodes for commercial LIB is only 372 mAh g^-1,which severely limits the development of high-performance LIB.In recent years,ZnO has become the research hotspot for lithium-ion battery anode materials,which due to its diverse advantages,such as high lithium storage characteristics(978 mAh g^-1),lithium ion diffusion coefficient and natural storage.And low cost and low environmental pollution.In addition,due to its crystallographic characteristics,ZnO can be easily designed into a variety of nanostructures.However,the poor conductivity,low ion migration kinetics,and the huge volume change of ZnO during cycling make the cycling performance of the electrode unstable and the rate performance poor.Additionally,the volume expansion and contraction of ZnO caused by repeated lithium intercalation extraction processes may also cause continuous deformation and fracture of the solid electrolyte mesophase?SEI?and degradation of the electrode structure,preventing lithium transportation and losing good electrical contact,thereby making the Coulomb efficiency low and the capacity decay severe.In order to solve these problems,compounding ZnO with the highly conductive carbon material will be an effective method,because carbon can not only effectively improve the electronic conductivity and accelerate the electrochemical reaction kinetics,but also suppress the volume expansion.In addition,compared with ordinary carbon materials,biomass materials can reduce environmental pollution.Among many biomass materials,rice husks are abundant and easy to obtain.Therefore,in this paper,the biomass carbon extracted from rice husk is used as a carbon source to compound with different forms of ZnO.The ZnO and rice husk carbon composite materials are used as anodes of lithium ion batteries,and their electrochemical performance tests and microstructure characterization are performed.The main contents are as follows:?1?Rice husk cellulose was prepared by using rice husk as raw material through alkaline treatment and acid washing.Zn?NO₃?₂·6H₂O was used as the zinc sorce and reacted with KOH under hydrothermal conditions to obtain ZnO Solution.The ZnO solution is hydrothermally carbonized with the prepared rice husk cellulose to obtain the flower-like ZnO and rice husk carbon composite material.We explored the effects of hydrothermal time for synthesizing ZnO and hydrothermal carbonization recombination time of ZnO and RHC on the electrochemical performance and microstructure of materials,and analyzed the differences between pure ZnO and composite materials.The composite materials of ZnO and rice husk carbon have good electrochemical and physical properties.The discharge specific capacity after 100cycles at 0.2 C rate reaches 1002.5 mAh g^-1,and the rate performance is good.?2?Zn?NO₃?₂·6H₂O?or ZnCl₂?was used as the zinc precursor,polyvinylpyrrolidone was used as the surfactant,deionized water was used as the solvent,and ammonia was added under ultrasonic conditions to synthesize ZnO by coprecipitation.The ZnO undergoes a hydrothermal compound reaction with prepared rice husk cellulose solution to obtain the porous compound material.We studied the effects of ZnO synthesized from different zinc precursors on the properties of composites,explored the effect of hydrothermal recombination time on the electrochemical properties and microstructure of composite materials,and compared the differences between the properties of pure phases and composite materials.The composite electrode has excellent performance,and the reversible specific capacity is stable at 936 mAh g^-1 after 100 cycles at 0.2 C.