The essential need for new lithium-ion battery materials providing higher energy and power densities has triggered an exceptional increase in scientific and industrial research efforts in recent years. Regarding the anode side, the two major research directions to achieve improved energy densities have, so far, focused on materials which can host lithium either by alloying or by a conversion mechanism. Very recently, however, a new class of potential next generation anodes is gaining continuously increasing attention: conversion/alloying materials. Herein, we provide for the first time a comprehensive review on this new materials' class. Initially, we discuss the two possible approaches to realize a combined conversion and alloying mechanism in a single compound, starting either from pure conversion or pure alloying materials. Based on this overview we subsequently highlight the fundamental insights and their potential advantages, which shall provide scientists with some general considerations and principles for the development of new, further enhanced conversion/alloying materials.
