Research On Preparation And Surface Coating Modification Of Spinel Lithium Manganese Oxide Cathode Materials

The lithium-ion battery,as a type of green and eco-friendly secondary power supply with high energy density,high power density,high operating voltage,long life,no memory effect and no-pollution,has been developing rapidly and widely used in daily life.It has become the main power of the portable mobile electronic devices such as cellphone,cameras and computers and its application is continuous expanding.In general,the choice of lithium-ion battery cathode material was crucial for the performance?such as electrochemical performance,stability and safety performance,etc.?and the cost,which means that the performance and the cost is mainly affected by properties of cathode materials.The spinel lithium manganese oxide?LiMn₂O₄?cathode material with three-dimensional lithium-ion diffusion channels has attracted extensive attention because of its high operating voltage,high thermal stability,excellent security,low cost and environment-friendly,and it is one of the potential cathode materials in the lithium-ion battery industry.However,the fast decaying of specific capacity of the spinel LiMn₂O₄ has severely limited its large-scale commercial application and promotion.Thus,the spinel LiMn₂O₄was selected as the research object in this paper,and the paper firstly prepared the spinel LiMn₂O₄ cathode material by high temperature solid phase method,and secondly surface coated the coating materials,and the research work is as follows:This paper,firstly,researched the different lithium contents on the properties of the spinel LiMn₂O₄ cathode material prepared by high temperature solid phase method.Based on the experiments,the following conclusions had been arrived at.When the amount of lithium is 5%,the prepared spinel LiMn₂O₄ cathode material got the best excellent electrochemical performance.The initial specific capacity was 123.6mAh/g,the capacity retention rate is 92.6%after 100 cycles,and the high current discharge performance at 3C and 5C is better than other materials,while the discharge capacity were 102.8mAh/g and 94.8mAh/g respectively.This paper had researched the performance of the spinel LiMn₂O₄ cathode materials by coating different metal oxide?NiO,ZnO and Al₂O₃?,and the following conclusions had been reached.The cycle performance and high current charge/discharge performance of the spinel LiMn₂O₄ modified by metal oxide were all superior to the unmodified spinel LiMn₂O₄,and the spinel LiMn₂O₄ modified with ZnO showed the most excellen electrochemical performance.The initial specific capacity was 133.7mAh/g,and the capacity retention rate is 94.0%after 100 cycles,as well as the high current discharge specific capacity were 114.4mAh/g and 104.1mAh/g at 3C and 5C respectively.Furthermore,the properties of the spinel LiMn₂O₄ cathode materials by coating different nano-carbon materials?CNT and HGO?have also been studied,and the following conclusions had been obtained.The initial charge/discharge specific capacity,cycle performance and high current charge/discharge performance of the spinel LiMn₂O₄ modified by nano-carbon materials were all superior to the unmodified spinel LiMn₂O₄,and the spinel LiMn₂O₄ modified with HGO possess the highest initial specific capacity?139.9mAh/g?,while the the spinel LiMn₂O₄ modified with CNT displays the best cycle performance and high current charge/discharge performance.And the initial specific capacity was relatively high?133.7mAh/g?,the discharge specific capacity was decayed from 137.2mAh/g to 129.2mAh/g with the 5.8%attenuation,while the high current discharge specific capacity were 115.0mAh/g and 106.1mAh/g respectively at 3C and 5C.The spinel LiMn₂O₄ cathode materials modified with CNT by ball milling showed the better electrochemical performance.It has the higher initial specific capacity?139.9mAh/g?,the better cycle stability?95.9%?and the more excellent high current discharge performance?the specific capacity at 3C and 5C were 128.1mAh/g and 124.2mAh/g?.The spinel LiMn₂O₄ cathode materials modified with ZnO and CNT showed the relatively high initial specific capacity and the best cycle performance.The initial specific capacity was 138.8mAh/g,and the specific capacity increased first and then decreased during the cycling,and the cycle stability was 102.7%after 100 cycles.