Research On Evaluation Method And Secondary Utilization Of Retired Lithium Batteries

With the gradual replacement of fuel-fueled vehicles by new energy vehicles and the development of lithium-ion battery energy storage technology,the problem of power lithium battery recycling and secondary utilization has become increasingly prominent.In response to global warming,countries around the world have proposed a variety of new energy vehicles to replace fuel vehicles.If the retired ternary lithium-ion batteries in new energy vehicles are not properly selected and used in the future,they will cause pollution to the environment.The remaining capacity of decommissioned batteries still has a lot of room for utilization.The division of state and echelon utilization of them was of great significance for improving their energy efficiency utilization and reducing the pressure of environmental pollution caused by decommissioned batteries.In this paper,how to efficiently use retired batteries of different capacities,and different working conditions had different requirements for the utilization performance of retired lithium batteries.This paper studied how to divide the intervals of different health states to achieve the maximum efficiency of retired lithium battery utilization.Based on the selection of the equivalent circuit of the decommissioned lithium-ion battery,the three main factors affecting battery degradation was analyzed by simulation,and the state of health of the decommissioned battery is divided according to the output attenuation characteristics,and defined the operating lower limit of the state of charge at practical work.According to the working characteristics of the decommissioned lithium ion battery,analyzed the specific applicable scenarios of the decommissioned ternary lithium ion battery and divided the health status interval.The typical scene of ice melting on transmission lines was selected and applied to DC ice melting power sources to conduct research on the secondary utilization of decommissioned lithium batteries.Firstly,compared the equivalent circuit models of different lithium batteries,and selected the first-order RC equivalent circuit for simulation modeling and testing under different ambient temperatures and different degrees of polarization reactions;analyzed the effects of ambient temperature,polarization degree and discharge depth on decommissioned batteries’ process of recession.Secondly,compared the different status,ran parameters under the condition of simulated HPPC test,by analyzing the different relationship between open circuit voltage,discharge ratio down depth will be retired the health status of lithium battery by recycled into 80% ～ 60%,60% ～ 45%,45% ～ 30% three interval,defined the scope charged state run at the same time,on the pilot used lithium batteries,realized the retired battery recycling and secondary utilization efficiency maximization.Finally,in view of the frequent ice-covering of transmission lines in southern China,northeast China and mountain and forest regions,the application of direct current melting ice was selected as the actual working scenario of the ladder utilization to prove that the recycled ternary lithium ion battery can be effectively used in the power grid for secondary use.Considering the impact of the cost of the DC ice-melting device,the output power and capacity of the decommissioned lithium-ion battery energy storage unit and the heat loss of the transmission line,the calculation formula for the relevant parameters of the decommissioning lithium battery ice-melting has been improved on the premise of ensuring the efficiency of the icemelting.A short-distance interval ice-melting scheme suitable for actual working conditions to achieve non-stop ice-melting;PSCAD simulation test proves that when decommissioned lithium-ion batteries are recombined into ice-melting power supply,the harmonic content generated by the ice-melting line section is small.The impact of power transmission was negligible.Using COMSOL physical environment simulation software,the simulation results of the temperature field during the ice-melting process of the overhead line show that the line temperature will not exceed the limit during the ice-melting process,which proved that the recycled ternary lithium ion battery can be used in the power grid for secondary use.