Research On Volume Energy Density Of Small And Protable Lithium Ion Battery

As a new type of green secondary battery,Lithium ion battery has been widely applied in mobile communation equipments like smartphone,notebook etc,due to its advantage of high energy density,high power density,wide temprature range,long cycle life.With the development of science & technology,the upgrade of mobile terminal equipments and small digital products,the tendency of the mobile communication device become lighter,thinner and smaller.The end-users put forward more requirments on high capacity and long standby time et al,which means higher requirment on the battery capacity and energy density.In order to meet the customer's requirments of high capacity,long standby time of smartphone and safety,this thesis is focus on the small and portable lithium ion battery,the high energy density battery are prepared and the electrochemical properity and safety are investigated.The battery was fabricated through slurry mixing,coating,assembly,formation process,the electrical property LiCoO2 was studied by charge/discharge machine;the rate performance was tested at different current;the high temperature storage performance was investigated by high temperature chamber;the safety performance was investigated by hotbox and impact test.The result shows that the amount of active material per unit(cm2)increased by 0.0011 g with the increasement of packing density followed by the increasement of energy density raised from 579Wh/L to 601Wh/L at the charge/discharge rate of 0.2C,the energy density increased about 3.8% comparing with comparison cell.The capacity retention rate was 89.7% after 500 cycles;It showed good safety performance by hotbox and impact verification;The process and performance uniformity of mass production were excellent which can meet Z customer requestments(capacity reach to 2460 m Ah with 3.3% increase;safety meet customer and GB requirement,capacity retention rate higher than 80% after 500 cycles).High packing density battery shipout is 300 thousands per month,the direct economic benefit is 2.88 million RMB one month.The composite electrode was prepared by ternary material Li Ni1/3Co1/3Mn1/3O2(NMC)and LiCoO2(LCO)at a certain proportion(1:4)and the battery was fabricated through slurry mixing,coating,assembly,formation process.The battery capacity was 3775 m Ah(657Wh/L)after compositing with NMC at the discharge rate of 0.2C(740m A),the energy density increased 14.9% comparing with none combination NMC electrode(dishcarge capacity was 3289 m Ah(572Wh/L)).The low temperature discharge performance was better than single lithium cobalt oxide battary.Capacity retention rate at-10? was 84.5% and the energy density increased 23%.However the cycle performance(capacity retention rate)was not good as single lithium cobalt oxide battery expecially at high temperature.Although the temperature increasing rate was higher during the impact test,overcharge test and high temperature short test,the battery composited with NMC was still safe without fire and explosion;The process and performance uniformity of mass production are excellent which can meet X customer shipment requirment of 450 thousands per month.The cost saving of composite ternary material of NMC and LCO battery is 795 thousands RMB one month.