Study On Preparation And Properties Of LiNi_0.8Mn_0.2O₂ Embedded Conductive Carbon

Since the advent of lithium-ion batteries,they have been widely used in various fields.With the increasing environmental problems and the depletion of non-renewable energy sources,the new energy vehicle industry has ushered in a vigorous development.Lithium ion batteries have become the first choice for new energy vehicle power batteries due to their advantages of high open circuit voltage,long cycle life,fast charge and discharge,and no memory effect.The cathode material greatly affects the performance and cost of lithium-ion batteries,so it has been widely studied.Among them,nickel-based cathode materials have become one of the most promising cathode materials on the market due to their higher specific capacity and lower cost,and have good market prospects.Therefore,in this paper,the nickel-based cathode material Ni_0.8Mn_0.2O₂ is taken as the research object,the preparation process is optimized,and the electrochemical performance is improved by embedding conductive carbon materials in the material and doping Co element.The main conclusions are as follows:?1?Ni_0.8Mn_0.2?OH?₂ precursor was synthesized by co-precipitation method,and LiNi_0.8Mn_0.2O₂ cathode material was synthesized by high-temperature solid phase sintering.After a series of test methods,the concentration ratio of ammonia water to metal salt is 0.5,the reaction pH is 11.35±0.05,the reaction kettle temperature is55±2?,the ratio of precursor to lithium hydroxide is 1.08,and the temperature is kept at 800?At 14 h,the crystal form of LiNi_0.8Mn_0.2O₂ cathode material prepared under this condition was fully developed,belonging to the layer structure of?-NaFeO₂.The LiNi_0.8Mn_0.2O₂ cathode material obtained under such preparation conditions has the most excellent electrochemical performance.The discharge specific capacity at the time of formation is as high as 179 mAh/g,the first Coulomb efficiency is 91.62%,and the capacity retention rate is 90.21%after cycling 200 times at 25?,2.75-4.2 V,0.2 C rate.Under 5 C large rate discharge conditions,it still has a specific capacity of 147.87mAh/g,and the capacity retention rate is 79.46%.?2?The positive electrode material is added with conductive carbon materials Li-435 and CNTs in the co-precipitation process.During the co-precipitation reaction,it will adsorb and grow on the surface of the carbon material,and control the growth of precursor particles by controlling the flow rate of the solution.Thus,a precursor of conductive carbon material Ni_0.8Mn_0.2?OH?₂ is obtained.During the sintering process,the conductive carbon material will be oxidized in an oxygen-rich environment,and the generated CO₂ gas escapes from the inside of the particles,making the gap between the primary particles larger,and some primary particles even fall off from the secondary particles.The specific surface area of the material showed an increase from 1.440 m²/g of unadded material to 1.7340 m²/g.The material cycle stability has been greatly increased,200 cycles from 76.61%stability rate increased to 96.38%.?3?During the preparation of the precursor,the addition of Li-435 and Co elements is carried out at the same time,so that the addition of Co-modified embedded conductive carbon is added.The development of the layered structure is promoted,which is common with Li-435 to improve the conductivity of the material Effect,the rate performance has been greatly improved,especially the 5 C rate has been increased from 83.14%capacity retention rate by 7.26%to 90.4%.