Electrochemical ion insertion from the atomic to the device scale

Abstract

Electrochemical ion insertion involves coupled ion-electron transfer reactions, transport of guest species, and redox of the host. The hosts are typically anisotropic solids with two-dimensional conduction planes, but can also be materials with one-dimensional or isotropic transport pathways. These insertion compounds have traditionally been studied in the context of energy storage, but also find extensive applications in electrocatalysis, optoelectronics, and computing. Recent developments in operando, ultrafast, and high-resolution characterization methods, as well as accurate theoretical simulation methods, have led to a renaissance in the understanding of ion-insertion compounds. In this Review, we present a unified framework for understanding insertion compounds across time and length scales ranging from atomic to device levels. Using graphite, transition metal dichalcogenides, layered oxides, oxyhydroxides, and olivines as examples, we explore commonalities in these materials in terms of point defects, interfacial reactions, and phase transformations. We illustrate similarities in the operating principles of various ion-insertion devices ranging from batteries and electrocatalysts to electrochromics and thermal transistors, with the goal of unifying research across disciplinary boundaries.

Theory of layered-oxide cathode degradation in Li-ion batteries by oxidation-induced cation disorder

“…Our general theoretical framework for cation disorder driven by electrochemical reactions may find applications in other uses of intercalation materials [102]. For example, blocking cations create fundamental challenges in lithium extraction from multicomponent brines or seawater by ion exchange using battery materials, such as in Li x FePO 4 , where even small amounts of Mn 2+ intercalation can irreversibly poison the material [75,127] and large amounts of intercalated Na + interfere with selectivity for Li + [72].…”

Crystallographic design of intercalation materials

“…The reversible intercalation of active species into a host-electrode often induces an abrupt structural transformation of its crystal lattices. 1 These structural changes range from displacive transformations (in which atoms undergo cooperative movement resulting in changes to lattice parameters [33]) to transformations accompanied by polyhedral rotations that not only generate significant lattice strains but also affect the electronic structure of the host material [6,12]. These structural transformations impede ion migration, nucleate microcracks, and contribute to the irreversible decay of material properties, see Fig.…”

“…Intercalation is the reversible insertion of active ions (or molecules) into a materials' lattice structure. This reversible insertion is often accompanied by a simultaneous change to the host materials' lattice structure and/or its physical properties (i.e., optical, thermal, electronic) [1]. This intrinsic coupling between ionic (or molecular) insertion and physical properties makes intercalation materials well-suited for next-generation applications, such as electrodes in lithium batteries [2], electrochromic materials in smart windows [3,4], and ion-exchange membranes in water desalination devices [5].…”

Interfacial resistive switching by multiphase polarization in ion-intercalation nanofilms

“…Such electrons are often found in mixed-valency transition metal oxides, 27,[61][62][63][64] which include some of the most common ionintercalation materials used in Li-ion batteries and other applications. 65 The fundamental constants we use include the Boltzmann constant k B , temperature T , electron charge e,…”