Effects of Transition Metal Dissolution and Deposition on LI-Ion Batteries:A Multi-Scale Approach.

[摘要] In the past decade, lithium-ion (Li-ion) batteries have become increasingly important components in vehicle electrification due to their high power and energy density. However, Li-ion batteries exhibit degradations especially during long-term cycling or storage at elevated temperatures. One of the key degradation mechanisms of Li-ion batteries is transition metal dissolution of the cathode materials and deposition of transition metals onto the anode. Therefore, this dissertation investigates the fundamental physics underlying degradation mechanisms and presents effective solutions for minimizing metal dissolution and improving battery cell performance. Based on a series of experiments and numerical simulations, this dissertation 1) investigates manganese dissolution and deposition mechanisms, 2) predicts cell degradations, 3) presents an optimized ratio for composite electrodes, and 4) suggests approaches to reduce manganese dissolution. To obtain the results, a number of experiments were conducted to understand degradation phenomena and to provide input parameters for simulations. These experiments included 1) characterizations of both positive and negative electrodes, 2) quantifications of the amount of dissolved and deposited manganese, and 3) electrochemical measurements of the cell behaviors. Multi-scale simulations were implemented on both the cell scale and the atomistic scale. Cell scale simulations were employed to predict the cycle life of battery systems. Atomistic scale simulations were performed to investigate and subsequently minimize manganese dissolution. Moreover, comparisons between experiments and cell scale simulations were conducted to gain an advanced understanding of degradation mechanisms and to validate the simulations. The current study found that both active material loss and electrode degradation due to manganese dissolution critically influence the performance of the cathode. Moreover, by depositing onto the anode, dissolved manganese ions accelerate the formation of the decomposed layer and continuously cause capacity fade. These results suggest that reducing manganese dissolution is necessary to improve battery capacity and cell performance. Finally, the current study suggests several effective solutions for minimizing and preventing manganese dissolution. These solutions include 1) optimization of the composition ratio in composite cathode and 2) surface treatments such as changing surface orientations and doping elements.

[发布机构] University of Michigan

[效力级别] transition metal dissolution

[关键词] Li-ion battery degradation mechanism;transition metal dissolution;li-ion battery multi-scale simulations;Mechanical Engineering;Engineering;Mechanical Engineering