Fast Charging Control Of Lithium-ion Batteries Without Lithium Plating Based On Reduced-order Electrochemical Model

New energy vehicles have gained traction.The key technology involves lithium-ion batteries,whose ability to fast charge is limited.Simply increasing the charging power may sacrifice the safety and lifetime of the battery,since the rate-limiting step is due to the battery performance rather than the charger.Safe and fast charging strategy is in demand for protecting the batteriesIn this dissertation,the large-format lithium-ion batteries for vehicle use are focused The safe and fast charging is achieved step by step from mechanism investigation,model reformulation to state estimation and optimal control.The degradation mechanism of the battery under different charging conditions is identified.A lumped-parameter model for anode potential estimation is built and transfer functions are derived to generate a reduced-order model.A step-wise parameter identification strategy based on electrode and frequency decomposition is proposed with the help of a novel long-term electrode potential sensor.Deposition-free fast charging is successfully realized through the use of a closed-loop anode potential observer and an online current modification controller.Firstly,the mechanism accounting for battery degradation under charge abuse is in-vestigated,and the behavior mechanism of lithium deposition is elucidated.The nonlinear aging phenomenon of the battery is analyzed through the low-temperature accelerated life test.Based on in situ analysis and SEM,the major aging mechanism induced by charging is identified as loss of lithium inventory due to lithium deposition.A deeper look at the capacity recovery phenomenon suggests the lithium reintercalation after plating,which is also investigated by voltage differential and electrode potential signal.A comprehensive lithium deposition reaction mechanism is summarized.Controlling the anode potential is crucial to address lithium depositionSecondly,a lumped-parameter anode potential estimation model is established,and a novel parameter identification method is developed.Beginning by the full-order P2D model,the minimum parameter set of the P2D model is obtained by model reformula-tion,and a reduced-order anode potential estimation model is established by deriving the transfer functions of the state variables.A generalized frequency-domain model of solid/electrolyte interface is presented,modified by introducing CPEs to accommodate non-ideal capacitance and particle effects.A long-term electrode potential sensor is in-vented for parameter identification.The inherent blocking effect of the sensor thoroughly examined to ensure measurement accuracy.A novel identification method based on elec-trode decomposition and frequency-domain decomposition is proposed with the help of the sensor.Finally,a safe and non-destructive fast charging strategy using the anode potential observer and current modification controller is proposed.The closed-loop anode potential observer is developed based on the reduced-order model.The current modification controller is developed based on the observed anode potential.Safe and fast charging is realized by coupling control.Fast charging tests are executed on both virtual and real batteries.Durability experiments show that the charging strategy is plating-free.Based on the results of the fast charging,an optimal charging theory of lithium-ion batteries is proposed.The analytical expression of the optimal charging current is provided and the validity of the theory is examined.