Zheng Jingxu, Garcia-Mendez Regina, Archer Lynden A
Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States.
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02129, United States.
ACS Nano. 2021 Dec 28;15(12):19014-19025. doi: 10.1021/acsnano.1c08719. Epub 2021 Dec 13.
Coupled electron/ion transport is a defining characteristic of electrochemical processes, for example, battery charge/discharge. Analytical models that represent the complex transport and electrochemical processes in an electrode in terms of equivalent electrical circuits provide a simple, but successful framework for understanding the kinetics of these coupled transport phenomena. The premise of this review is that the nature of the time-dependent phase transitions in dynamic electrochemical environments serves as an important design parameter, orthogonal to the intrinsic mixed conducting properties of the active materials in battery electrodes. A growing body of literature suggests that such phase transitions can produce divergent extrinsic resistances in a circuit model (.., , describing electron transport from an active electrode material to the current collector of an electrode, and/or , describing ion transport from a bulk electrolyte to the active material surface). It is found that extrinsic resistances of this type play a determinant role in both the electrochemical performance and long-term stability of most battery electrodes. Additionally, successful suppression of the tendency of extrinsic resistances to accumulate over time is a requirement for practical rechargeable batteries and an important target for rational design. We highlight the need for battery electrode and cell designs, which explicitly address the specific nature of the structural phase transition in active materials, and for advanced fabrication techniques that enable precise manipulations of matter at multiple length scales: (i) meso-to-macroscopic conductive frameworks that provide contiguous electronic/ion pathways; (ii) nanoscale uniform interphases formed on active materials; and (iii) molecular-level structures that promote fast electron and/or ion conduction and mechanical resilience.
电子/离子耦合传输是电化学过程的一个决定性特征，例如电池的充电/放电过程。用等效电路来表示电极中复杂的传输和电化学过程的分析模型，为理解这些耦合传输现象的动力学提供了一个简单但成功的框架。本综述的前提是，动态电化学环境中随时间变化的相变性质是一个重要的设计参数，与电池电极中活性材料的固有混合导电特性相互独立。越来越多的文献表明，这种相变会在电路模型中产生不同的外在电阻（例如，描述从活性电极材料到电极集流体的电子传输，和/或描述从本体电解质到活性材料表面的离子传输）。研究发现，这种类型的外在电阻在大多数电池电极的电化学性能和长期稳定性中都起着决定性作用。此外，成功抑制外在电阻随时间累积的趋势是实用可充电电池的一个要求，也是合理设计的一个重要目标。我们强调需要设计电池电极和电池，明确解决活性材料中结构相变的具体性质，还需要先进的制造技术，能够在多个长度尺度上对物质进行精确操控：（i）提供连续电子/离子通道的介观到宏观导电框架；（ii）在活性材料上形成的纳米级均匀界面；以及（iii）促进快速电子和/或离子传导及机械弹性的分子级结构。
