High‐Capacity Anode Materials for Lithium‐Ion Batteries: Choice of Elements and Structures for Active Particles

Abstract

. IntroductionSignifi cant research effort has been devoted to novel electrodes for Li-ion batteries in recent years due to its high potential impact on energy storage for electric vehicles (EVs) and portable electronics. Li-ion batteries have already become the battery of choice for portable electronics and EVs due to their high energy density and decreasing cost. However, they are also often a limiting factor. Li-ion batteries often make up a large portion of the mass and volume of portable electronics and still limit their available energy, thus requiring frequent recharging. Currently, battery-powered EVs either offer a small driving range or are expensive due to the high price tag of Li-ion batteries. An increase in battery energy density, particularly volumetric energy density, can greatly improve and expand the possibilities of portable electronics. If similar production expenses per unit cell, and thus a lower cost per unit energy, is achieved at the same time, higher range and more affordable EVs can be produced.In order to address the market needs of reduced cost and improved energy density, many researchers have aimed to improve volumetric capacity of anodes and cathodes. High-capacity anode research, in particular, has been extremely active, and materials such as silicon (Si), silicon oxide (SiO x ), tin (Sn), and tin oxides (SnO x ) have received enormous attention, while many other, sometimes more exotic materials, have appeared in literature as well. This review is an attempt to provide a general overview of high-capacity anode materials and to develop a broader understanding of the scientifi c explorations in the fi eld of high-capacity Li-ion anodes. A detailed and comprehensive review is not attempted, and there are no doubt topics and groups of publications, which we will inevitably overlook. However, the greatest effort is made to cover the entire periodic table, and to review the various innovations in electrode architecture and chemistry, which can dramatically improve anode capacity.A traditional high-capacity Li-ion battery is made from a lithium cobalt oxide (LiCoO 2 often called LCO) cathode and a graphite (C) anode. Both electrodes are produced from active (Liion storing) powders mixed with a small content (3-5 wt%) of a polymer binder (mostly polyvinylidene fl uoride, PVDF) and a small content (1-5 wt%) of conductive carbon additives (mostly carbon black, but on occasion, vapor grown carbon fi bers or multi-walled carbon nanotubes, MWCNTs) and casted on both sides of metal current collector foils (an aluminum, Al, foil for a cathode and a copper, Cu, foil for an anode). A typical thickness of an electrode layer ranges from 60 to 100 μ m on each side of a foil. In a battery, the electrodes are separated with a porous electrically insulated membrane with a typical thickness of 15-25 μ m. By using higher capacity active materials and/or designing a structure/material that obviates/reduces the need for a separator membrane, binders, conductive additives, or current collectors, the overall ...

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