锰酸锂离子电池容量衰减机理及多物理场耦合分析

Capacity Fading Mechanism of Lithium Manganese Oxide Lithium-Ion Batteries and Multiphysics Coupling Analysis

摘要: 本研究旨在揭示锰酸锂离子电池容量衰减的内在机制，为延长电池寿命及提升安全性提供关键策略。利用COMSOL软件建立了尖晶石型锰酸锂(LiMn₂O₄)-石墨(LiC₆)电池的一维电化学–热耦合模型。在模型验证基础上，开展了长达2000次的循环充放电仿真，系统研究了不同循环周期下的电流、电位响应及容量演变规律，并进行了热特性分析。研究结果表明，电池容量衰减呈现出循环初期较快，后期衰减速率趋缓的阶段性特征。宏观上，高倍率放电(4C)导致浓差极化显著增加，实际容量仅为额定容量的70%，同时，其导致的高温环境也会导致容量衰减的发生；微观上，固体电解质界面膜(SEI)的持续生长与负极析锂是导致活性锂损失(LLI)的核心机制。明确了SEI膜增厚导致的阻抗上升与析锂引发的死锂积累是容量衰减的主因，据此提出了材料改性、充放电策略优化和改进散热环境的寿命延长方案。

Abstract: This study aims to elucidate the intrinsic mechanisms underlying capacity decay in lithium manganate-ion batteries, providing critical strategies for extending battery life and enhancing safety. Using COMSOL software, a one-dimensional electrochemical-thermal coupling model was established for spinel lithium manganate (LiMn₂O₄)-graphite (LiC₆) batteries. Based on model validation, 2000 cycling charge-discharge simulations were conducted to systematically investigate current and potential responses, capacity evolution patterns under various cycling conditions, and thermal characteristics. The results demonstrate that battery capacity decay exhibits a phased pattern: rapid initial rate followed by a decelerated subsequent phase. Macroscopically, high-rate discharge (4C) significantly increases concentration polarization, reducing actual capacity to merely 70% of the rated capacity, while the resulting high-temperature environment contributes to capacity degradation. Microscopically, the continuous growth of the solid electrolyte interfacial membrane (SEI) and lithium deposition at the anode are the primary mechanisms driving lithium loss in active material (LLI). The study identifies SEI film thickening-induced impedance increase and lithium deposition-triggered dead lithium accumulation as the main causes of capacity decay, proposing solutions including material modification, optimized charge-discharge protocols, and improved thermal management for extended battery life.