Research On Key Technology Of State Of Health Management Of Decommissioned Lithium Battery

In recent years,the second life utilization of decommissioned lithium battery has become a vital approach to maximize the benefit of lithium battery.However,it is highlighted for state of health management of decommissioned lithium battery that the estimation of state of health of decommissioned lithium battery is slow,reliability is lower and historical data is lack.Therefore,this thesis carries out a research based on credibility assessment of decommissioned lithium battery.The main contents of this paper are as follows:Firstly,key performances and parameters of decommissioned lithium-ion battery are tested and analyzed in this paper.The decommissioned lithium-ion battery performance test experiments platform(DLBPTP)based on battery test system is constructed.The decommissioned power lithium battery pack is disassembled with safety.Cells satisfying the standardization are used to test in the DLBPTPT and its parameters like depth of discharge,internal resistance,cycle life,et al.Test results show that the decommissioned lithium-ion battery is useful.Secondly,After building decommissioned lithium battery state of health model based on voltage and capacity data of cycle life tests of decommissioned lithium cells,a rapid state of health estimation method of decommissioned lithium battery based position-feature-voltage is proposed in this thesis.If not meet the condition,state of charge of the cell is under 50%,the tested cell should be discharged until the condition is met.The constant current rate of 1C is used to charging until the cell reaches its charge cut-off voltage for the first time.Obtaining the tested cell's incremental capacity(IC)curve and using moving average smooth filter and Gaussian smooth filter to smooth IC curve in sequence,which can reduce the noises in IC curve.Combining the voltages related to position characters of smoothed IC curve with the model builded to acquire state of health value of tested cell.Eventually,The error of proposed method is within 2.5%,which is validated by the charge and discharge test data of real decommissioned lithium battery.Finally,in order to solve lack and lower credibility of historical data for state of health of decommissioned lithium battery in second use,a decommissioned lithium battery management method based on blockchian is proposed.Blockchain technology and state of health estimation of decommissioned lithium battery in second use are combined in this thesis.At the beginning,battery package key-value structure in block is constructed by identify label and state of health of decommissioned lithium battery.For uniqueness of key,a battery pack identification method based on Merkle tree structure is proposed.To reduce the impact of network failures on the value validation processing in the traceability,a data verification method based on Hoeffding lemma is presented.Building the traceability platform of health of state of decommissioned lithium battery based on blockchain.Verification results show that proposed methods are feasibility and effectiveness.The generation time of the battery pack tree example is less than 700 milliseconds.