Hysteresis in electrochemical systems

Abstract Hysteresis is a phenomenon that pervades both the physical and social sciences. While commonly associated with magnetism, it also occurs in a wide variety of other materials, including ferroelectrics and shape memory alloys. Hysteresis emerges when a particular property has a history dependence. It is exploited in microelectronic memory, logic, and neuromorphic devices. In electrochemical systems, such as Li‐ion batteries, hysteresis is undesirable as it leads to energy losses during each round trip charge–discharge cycle. Unfortunately, many new battery concepts that promise significant increases in energy density, including those that rely on displacement and conversion reactions, or on anion‐redox mechanisms, suffer from severe hysteresis that prevents their commercialization. This article surveys different forms of hysteresis in electrochemical systems with a focus on Li‐ion batteries and establishes thermodynamic and kinetic principles with which to understand and rationalize electrochemical hysteresis. The ability to control hysteresis in rechargeable batteries will enable the implementation of promising electrode chemistries. It will also open the door to many new device applications. As on‐chip batteries become more prominent, new possibilities will emerge to incorporate them not only as local energy sources but also as active components of new device concepts that exploit electrochemical hysteresis.