Exploring Anomalous Charge Storage in Anode Materials for Next-Generation Li Rechargeable Batteries

Abstract

To advance current Li rechargeable batteries further, tremendous emphasis has been made on the development of anode materials with higher capacities than the widely commercialized graphite. Some of these anode materials exhibit capacities above the theoretical value predicted based on conventional mechanisms of Li storage, namely insertion, alloying, and conversion. In addition, in contrast to conventional observations of loss upon cycling, the capacity has been found to increase during repeated cycling in a significant number of cases. As the internal environment in the battery is very complicated and continuously changing, these abnormal charge storage behaviors are caused by diverse reactions. In this review, we will introduce our current understanding of reported reactions accounting for the extra capacity. It includes formation/decomposition of electrolyte-derived surface layer, the possibility of additional charge storage at sharp interfaces between electronic and ionic sinks, redox reactions of Li-containing species, unconventional activity of structural defects, and metallic-cluster like Li storage. We will also discuss how the changes in the anode can induce capacity increase upon cycling. With this knowledge, new insights into possible strategies to effectively and sustainably utilize these abnormal charge storage mechanisms to produce vertical leaps in performance of anode materials will be laid out.

Efficient Na‐Ion Storage in 2D TiS2 Formed by a Vapor Phase Anion‐Exchange Process

“…Therefore, we suggest that the ultrathin Ti 0.77 S nanocrystals provide additional active centers for Na + ion accommodation. [40] Besides, given the semi-metallic character of Ti 0.77 S, it could catalyze the formation/decomposition of electrolyte-derived surface layers, which also contributes to the additional capacity at the low potential of 0.4-0.3 V versus Na/ Na + . [40] Furthermore, extra Na + ion could be accommodated in the abundant micropores of the 3D carbon honeycomb with limited values.…”

“…[40] Besides, given the semi-metallic character of Ti 0.77 S, it could catalyze the formation/decomposition of electrolyte-derived surface layers, which also contributes to the additional capacity at the low potential of 0.4-0.3 V versus Na/ Na + . [40] Furthermore, extra Na + ion could be accommodated in the abundant micropores of the 3D carbon honeycomb with limited values. [19,40] In light of this, we deduce that the as-prepared TiS 2 @C nano-honeycombs could work as efficient anode materials involving both intercalation and conversion mechanisms for Na + storage with additional capacity at the potential window of 0.3-3.0 V. In addition, the high conductivity of the in-situ generated intermediates of NaTiS 2 and Ti 0.77 S also contribute to the high rate capability and long-term cycling stability.…”

“…[40] Furthermore, extra Na + ion could be accommodated in the abundant micropores of the 3D carbon honeycomb with limited values. [19,40] In light of this, we deduce that the as-prepared TiS 2 @C nano-honeycombs could work as efficient anode materials involving both intercalation and conversion mechanisms for Na + storage with additional capacity at the potential window of 0.3-3.0 V. In addition, the high conductivity of the in-situ generated intermediates of NaTiS 2 and Ti 0.77 S also contribute to the high rate capability and long-term cycling stability. [20,32] To make a distinction between faradaic and non-faradaic processes involved in the Na + storage process, CV curves of TiS 2 @C nanocomposites were recorded at different scan rates.…”

Multiscale factors in designing alkali-ion (Li, Na, and K) transition metal inorganic compounds for next-generation rechargeable batteries

“…The formation of solid-electrolyte interphase (SEI) layer is well known interfacial phenomenon at the anode because of its mostly inevitable spontaneous reaction environment, i.e., higher lithiated anode energy than lowest unoccupied molecular orbital (LUMO) of electrolyte components, and the electrochemical voltage window of electrolyte is enlarged once proper SEI layers are formed. 244,269 Although irreversible SEI layer formation at the anode entails a noticeable capacity loss by forming inorganic/organic compounds at the initial few cycles, it has been treated as a necessary evil because of its not only passivating and repairing ability 270 but also unexpected additional capacity 271 , so that relevant research largely have been focused on. [272][273][274][275][276][277] Similarly, delithiated cathode energy, which is lower than highest occupied molecular orbital (HOMO) of the electrolyte, induces further decomposition of the electrolytes forming CEI layer at the cathode.…”

Solution‐Processed All‐V2O5 Battery

“…In these batteries, electrode materials are the key component and play a critical role in determining their electrochemical performance. [2,12,13] Vanadium pentoxide (V 2 O 5 ), featured with high theoretical capacity, low cost, and abundant source, has attracted great interest for the rechargeable batteries. [4][5][6][7][8][14][15][16][17] Most of endeavor in V 2 O 5 has been devoted on realizing its capacity as cathodes in rechargeable batteries by constructing micro-/nano-sized, [18,19] hollow, [15,16] composite, [20][21][22] and/or heteroatom-doped structures.…”