Research On Lithium-rich Manganese-based Lithium-ion Battery Materials At Room Temperature Electrochemical Performance And Safety Performance

5Ah lithium ion power battery was manufactured by lamination technique withLithium-rich manganese based cathode material and MCMB anode material. And The effects ofpress density and the charging and discharging voltage range on the performance of Li-ionbattery were studied.The bulk density,the content of conductive agent of cathode, the ratio ofcathode and anode capacity and the composition of liquid electrolytes were studied to improvethe rate performance of the battery, The safe performance of the battery was tested.The results show that the rate performance of battery is improved and then worse with theincreasing of the press density. It is found that the discharge capacity at10C was82.9%of that at1C rate when the press density is3.0g/cm3. The capacity retention ratio is101.3%at1C after500cycles at the voltage range of2.75-4.2V.The first irreversible capacity loss increases with the increasing of the limited chargevoltage，And The first irreversible capacity losses are11.63%、17.21%、22.91%、26.62%、27.38%respectively at the voltage range of2.75-4.2V、2.75-4.3V、2.75-4.4V、2.75-4.5V and2.75-4.6V.The capacity retention ratios are still92.6%、97.9%、88.8%respectively at1C after1100cyclesat the voltage range of2.75-4.2V、2.75-4.3V、2.75-4.4V; But the capacity retention ratio is only60.9%at1C after500cycles in the voltage window2.75-4.5V. The capacity retention ratio isonly52.9%at1C after100cycles in the voltage window2.75-4.6V.The rate performance of battery is improved with the area density diminishing. It is foundthat the retention of discharge capacity at3C，5C，8C，10C is94.9%、93.5%、82.3%、81.7%of that at1C respectively when the area density is240g/m~2. The capacity retention ratio is still108.1%at1C after800cycles. The capacity retention ratio is still106.6%when battery ischarged at1C and discharged at5C after590cycles.The rate performance of battery is improved and then worse with the increasing of thecontent of conductive agent. It is found that the retention of discharge capacity at3C，5C，8C，10C is93.3%、91.3%、89.1%、83.4%of that at1C respectively when the content of conductiveagent is4%wt. The capacity retention ratio is still106.5%when battery is charged at1C anddischarged at5C after600cycles.Besides, The rate performance of battery is improved with the decreasing of the anode andcathode capacity.When the ratio of anode and cathode capacity is1.1, the battery shows excellentdischarge ability. Discharged at3C、5C、8C、10C，the retention of discharge capacity is about89.6%、86.5%、84.6%、84.0%of that at1C respectively. The capacity retention ratio is still116.6%when battery is charged at1C and discharged at5C after1200cycles.The rate performance of battery is strongly influenced by electrolyte.The electrolyte Bhaving the highe conductivity（11.42mS/cm）in the experiment shows excellent rate performance. Discharged at3C、5C、8C、10C，the retention of discharge capacity is about91.2%、89.0%、88.7%、88.3%of that at1C respectively. The capacity retention ratio is still100.4%when batteryis charged at1C and discharged at5C after1000cycles.The above studies show that the optimized process conditions of improving the rateperformance are as follows: the area density is240g/m~2, the content of conductive agent is4%wt, the ratio of anode and cathode capacity is1.1, the electrolyte B having the highestconductivity（11.42mS/cm）. Discharged at3C、5C、8C、10C，the retention of discharge capacityis about96.2%、94.5%、93.4%、92.1%of that at1C respectively. The capacity retention ratio isstill104.9%at1C after956cycles，The capacity retention ratio is still99.5%when battery ischarged at1C and discharged at5C after1000cycles. The results show that the battery has goodrate performance.The battery shows good safety performance through the needle punching, short circuit,3C-10V overcharge, free fall, weight shockand heat tests.