| With the development of society and the progress of industry,the demand for energy is increasing.Excessive consumption of fossil energy and intensified environmental pollution make the development of photovoltaic power generation of great significance.Photovoltaic power generation systems have the problem that sufficient sunlight generates excessive electricity during the day,and lack of sunlight generates insufficient power at night.In order to store excess power during the day for night use and to reasonably distribute electrical energy,lithium-ion batteries are used to store photovoltaic power,which will achieve"peak-cutting and valley-filling" and more reasonable use of the power generated by photovoltaic power generation systems.Photovoltaic power generation systems have two main requirements for energy storage power:(1)they can store more electricity generated by photovoltaic cells;(2)they have a long service life.Because of its large capacity,no heavy metal pollution,and long life,lithium-ion batteries are considered to be the best choice for energy storage power in photovoltaic power generation systems.At present,lithium-ion batteries have high lithium storage capacity,but there is still much room for improvement.Effectively improving the positive and anode electrode materials of lithium-ion batteries is an effective way to increase the capacity of lithium-ion batteries.As for the anode material,due to its large theoretical specific capacity(4200 mAh/g),the silicon anode is considered to be the most promising anode material for lithium ion batteries in the next generation.However,as a anode electrode material of lithium ion batteries,silicon has the problems of volume expansion and low conductivity.In recent years,many methods have been adopted to solve these two problems,and good progress has been made,but the corresponding lithium-ion batteries have not yet been produced and applied on a large scale.This is mainly due to the following two problems:(1)the volume effect of silicon-based anodes in the cycle of lithium insertion and removal has not been resolved;(2)the conductivity of silicon-based anode materials is low.In order to solve the above problems,we used silicon oxide materials with a small lithium-expansion volume expansion as the research object.Commercial silicon oxide was used for high temperature treatment to cause disproportionation reaction,and further mixed with graphite to synthesize silicon oxide/graphite with better conductivity.The composite material greatly improves the conductivity of the silicon-based anode material and effectively reduces the lithium insertion expansion problem,and its battery performance is greatly improved.Synthesized silicon oxide(m-d-SiO)and silicon oxide/graphite composite material(m-d-SiO/C)were used as active materials of the anode electrode to form a button half-cell.The results show that the reversible specific capacity of the m-d-SiO/C material during the first cycle of charging and discharging is 1265 mAh/g.After 100 charging and discharging processes,the specific capacity of the m-d-SiO/C material is still maintained at 1100 mAh/g,and the Coulombic efficiency is not less than 99.7%,has better electrochemical performance.Under the same conditions,the m-d-SiO material has only a reversible specific capacity of 720 mAh/g as the anode electrode active material,and the cycle stability is poor.In addition,we also use a silicon material containing metal impurities to form a porous structure through chemical etching to solve the volume expansion problem of silicon-based anode electrode lithium insertion.The method of corroding silicon aluminum alloy powder with hydrochloric acid and then mixing and milling with graphite in different proportions yields a porous silicon/graphite composite material(p-Si/C),which is used as an active material for a anode electrode.The results show that the porous silicon/graphite composite exhibits excellent electrochemical performance when the mass ratio of silicon is 40%.The reversible specific capacity during the first charging and discharging is 1061 mAh/g,and the Coulombic efficiency reaches more than 80%during the first charging and discharging.After 100 charging and discharging processes,the specific capacity is still maintained at 900 mAh/g,and its Coulombic efficiency is not less than 99.5%,which has better cycle stability. |
