Application Of Wheat Straw Cellulose Carbon In Anode Materials Of Lithium Ion Batteries

In recent years,the rapid development of the new energy industry has prompted people to put forward higher requirements for the capacity of lithium-ion battery electrode materials.Biomass materials are widely distributed in China and cause very little pollution to the land.It is a low-cost and recyclable resource.Therefore,researchers are trying to use it as a raw material in lithium-ion battery energy storage equipment.Wheat straw is the waste left in the fields after the autumn harvest.In winter in the north,it is consumed as a heating material in most cases.Therefore,if wheat straw can be reasonably applied to the field of lithium-ion batteries,it will not only realize the recycling of biomass waste but also provide a new environmental protection idea for the preparation of high-capacity negative carbon materials.This article takes agricultural waste wheat straw as the starting point and uses simple processing to extract the active ingredients in the laboratory and apply them to the electrode materials of lithium-ion batteries.In the first part of the experiment,wheat straw cellulose was used as a carbon source to coat tin dioxide nanoparticles,which improved the problem of poor structural stability during charge and discharge cycles,and improved the electrochemical performance of tin dioxide as a negative electrode material..In the second part of the experiment,the cellulose was pre-carbonized and activated with the activator KOH.After immersion in a water bath,high-temperature activation,and pickling to remove impurities,a porous activated carbon material with high specific capacity was obtained.All electrode materials synthesized in this research have been tested.The specific content and conclusions of the research are as follows:（1）Wheat straw cellulose is prepared from wheat straw as raw material and used as a carbon source to coat ultrafine nano-tin dioxide particles to form a composite material to improve the structural stability of the material.After the wheat straw is crushed,washed,and dried,a clean straw powder is obtained.The powder was first mixed with 2 mol L^-1NaOH solution according to the mass ratio of solid-to-liquid ratio of 1:20 in a reactor at180℃ for 12 h to remove lignin under high temperature and high-pressure conditions.After washing to neutrality and fully drying,disperse the filtrate into a 4%H₂SO₄ solution in a water bath at 95℃for 3 hours to remove hemicellulose and impurity metal ions.After the reaction is completed,the obtained filtrate is filtered,washed to neutrality,and dried in an oven at 65℃.to obtain white wheat straw cellulose.Afterward,the cellulose was pre-carbonized at 300℃ to obtain cellulose carbon,and then,using urea and tin tetrachloride pentahydrate as raw materials,ultrafine SnO₂nanoparticles were obtained through a one-step hydrothermal method.Mix it with pre-carbonized wheat straw cellulose at a mass ratio of 1:5,grind,and disperse it into 360 m L of water.After the solution is evenly dispersed,pour it into the reaction kettle.At 200℃ Heat at constant temperature for36 hours.After the reaction,the suspension was taken out,washed,and dried.The dried precipitate was fully ground and calcined in a tube furnace at 500℃ for 180 min.Finally,the SnO₂@WCC composite material was obtained.This chapter uses pure SnO₂electrode material as a control group to explore the effect of carbon coating on SnO₂electrode material.The SnO₂@GLU electrode material synthesized with glucose as a carbon source was used as a control group to explore the effects of different carbon sources coated with tin dioxide on the performance and morphology of the electrode material.Finally,the composite SnO₂@WCC electrode material was doped with nitrogen and sulfur to explore the influence of non-metallic elements on the electrochemical performance of SnO₂@WCC material.A large number of experimental tests show that the specific capacity of the nitrogen-rich and sulfur-rich SnO₂@WCC electrode material is stable and can reach 1250m Ahg^-1when cycled at a current rate of 0.2 C.When cycling at a current rate of 1 C,it can reach and stabilize at 1145 m Ahg^-1.The cycling capacity also performed well under variable rate.It showed excellent specific capacity after charging and discharging at high rate,and showed excellent cycling stability when it was restored to low current charge and discharge.（2）Using KOH as the activator,pores are formed on the surface of the pre-carbonized cellulose through high temperature activation treatment to obtain a porous cellulose carbon material.The effect of different activator dosage and activation temperature on the microscopic morphology and capacity performance of the material is explored.In the experiment,the pre-carbonized cellulose and KOH were mixed in mass ratios of 1:0,1:1,1:2,1:3,1:4,and 1:5,and dispersed into an appropriate amount of deionized water after being fully ground.Then put it in a water bath and immerse it in a water bath at 85℃ for 3hours.After the impregnation is completed,the filter material is placed in a constant temperature drying oven for drying,and then the material is activated and pore-made at high temperatures in a tube furnace at activation temperatures of 500℃,600℃ and 700℃.Finally,2 mol L^-1H₂SO₄ solution was used to remove excess metal impurities and washed to neutrality.After sufficient drying,the wheat straw cellulose-based porous activated carbon material was obtained.The data results show that KOH and cellulose carbon are mixed in a mass ratio of 4:1.The sample obtained at the activation temperature of 600℃ has the most abundant pore structure and specific surface area,and its pore volume and specific surface area respectively reach 0.171 cm³g^-1 and 628 m²g^-1,the sample is called PWCC4-600.The sample is tested at a current rate of 0.2 C,and the specific capacity can reach and stabilize at 1380 m Ahg^-1.The charging and discharging performance is still superior under the condition of variable magnification,showing good electrochemical performance.