Research On High Rata Lithium Titanate Battery

Lithium titanate battery has a wide application prospect in the field of power and energy storage battery with wide temperature,long life and rapid charge and discharge because the excellent properties such as charge and discharge in low temperature,long life and high power.The power density require of hybrid electric vehicle battery is more than 1800W/kg.First,we evaluate and screen the physical and chemical properties of the anode,cathode,separator and electrolyte materials needed for battery,and then explore the mixing and coating process of cathode to ensure no abnormality in the battery manufacturing process.In the aspect of battery design,we improve the cathode formula,electrolyte formula,area density of electrode and structure of cathode material to improve the start-up performance of the battery in low temperature environment;By improving the formation process,the composition of electrolyte and positive electrode LCo O₂doped to reduce the sidereaction,the reaction of gas generation under high temperature storage and high current cycle was inhibited.Finally,factors such as the electrolyte conductivity,electrode thickness,cathode material were considered to improve performance of rate discharge;In order to improve the reliability of battery application,we studied the heat generation of high current discharge and the temperature rise of lithium titanate battery nailed,and used finite element software to simulate.The main research process is as follows:（1）Positive and negative electrode materials with appropriate specific capacity and compaction density were selected,and the surface morphology and crystal structure of the materials were tested by SEM and XRD.The membrane material with proper permeability and porosity was selected and the thermal shrinkage experiment was conducted to test the electron microscope before and after thermal shrinkage.Electrolyte solvent composition optimization,conductivity measurement.The anode material selected for batching,coating process experiment,determine the anode into the electrode process of the optimal process,and the whole experiment program planning.（2）The positive electrode formula,electrolyte formula,area density of activity and structure of positive materials were optimized to reduce the electronic and ion impedance,and improve the cold cranking voltage of the battery.50%SOC,at least 3 consecutive startup times under-30℃environment,and the cut-off voltage is not less than 1.6V;After ensuring the required low temperature performance,the improvement experiments of battery aging process after formation,solvent composition of electrolyte and positive electrode LCo O₂doped were carried out to achieve low gas production,thickness expansion less than 6%and recovery capacity rate greater than 98%under 55℃30 days storage conditions.It cycled more than3000 times at 10C,the rate of retaining capacity is more than 98%,the battery does not produce gas,and the expansion rate of thickness is less than5%.The factors of high current discharge of lithium titanate battery were analyzed and the rate discharge of lithium titanate battery was improved.Under the condition of ensuring the comprehensive performance of the battery,the discharge capacity ratio of 30C to 1C is more than 95%,and the discharge capacity ratio of 40C to1C is more than 92%.（3）The heat generation factors of lithium ion battery were compared,and the 10C discharge temperature rise curve of each scheme was tested for different electrode structure,formula and electrolyte.The temperature rise function in the electrochemical-thermal coupling model was obtained by fitting the temperature rise curve.then the range and mean value of the heat generation rate and the heat generation rate per unit area were calculated.The heat generation rate was substituted into the finite element software to simulate the discharge temperature rise.The experimental results show that the difference of the heat generation rate between multipolar and laminated structure batteries was less than 5%;the content of cathode conductor super-p was reduced from 4.5%to 3.0%,the heat generation rate was increased 112%;the conductivity of electrolyte was reduced by 20%,the heat generation rate was increased by 6.9%.The heat generation rate of the best scheme was in a reasonable range.A short circuit heat generation-heat dissipation balance model of lithium titanate battery was established.The temperature rise and open circuit voltage of lithium titanate battery were get and analysed by nailed short circuit experiment and electrothermal model,the relationship between nailed short circuit current and temperature rise speed was determined.It is found that there is a short-circuit current while lithium titanate battery was nailed.