Challenges and Opportunities for Multivalent Metal Anodes in Rechargeable Batteries

Abstract

Lithium metal has been deemed the "Holy Grail" anode for next-generation, high-energy-density metal batteries. However, severe challenges in abundance, cost, and safety concerns have greatly hindered the practical use of Li metal anodes. Alternatively, multivalent metal anodes (Zn, Mg, Ca, Al, etc.) with less reactivity and much higher natural abundance are urgently summoned and increasingly investigated in recent years. The technologies for using multivalent metal anodes are not mature and are still in their infancy for practical applications. To comprehensively understand the challenges and opportunities for multivalent metal anodes, the fundamental mechanism and key issues are discussed here in detail, including electrolytes for reversible anode plating/ stripping, notorious surface passivation, dendrite formation, and anode corrosion. Strategies for tackling these issues are summarized. A general perspective and future research directions are also presented in this review. It is expected that this review will provide a promising opportunity for newly emerging multivalent metal anodes and pave the way for next-generation high-energy-density metal batteries.

A Self‐Regulated Interface toward Highly Reversible Aqueous Zinc Batteries

“…[ 1–6 ] Particularly, the Zn metal anode shows great promising ascendancy in abundant natural resources, high theoretical capacity (820 mAh g −1 , 5855 mAh cm −3 ), low redox potential (−0.76 V vs the standard hydrogen electrode), and nontoxicity. [ 7–11 ] However, there are still critical issues involving severe Zn dendrite growth and side reactions that greatly limit the practical application of Zn metal anodes and the industrialization of AZBs. [ 12–16 ] First, the uneven electric field and inhomogeneous Zn ion distribution during Zn plating, caused by the intrinsic surface imperfections of Zn anodes, inevitably result in nonuniform Zn deposition, which greatly contributes to the notorious Zn dendrite growth and thus causes short‐circuiting of the cell.…”

Building Ohmic Contact Interfaces toward Ultrastable Zn Metal Anodes

“…[ 1 ] However, the Zn anodes are of particular suffering on uncontrollable Zn dendrite growth and severe side reactions (i.e., corrosion and hydrogen evolution reaction (HER)) upon plating/stripping operations, which significantly hinders the practical application. [ 2 ] The dendrite formation may pierce the separator and eventually renders battery failure or even safety hazards. In addition, the continuous accumulation of irreversible by‐products (e.g., Zn 4 SO 4 (OH) 6 · x H 2 O and H 2 ) not only reduces the Coulombic efficiency (CE) of the cell, but also increases the inner pressure that may inflate the cell to failure.…”

Monocarborane cluster as a stable fluorine-free calcium battery electrolyte

“…In particular, Ca has a low reduction potential (− 2.87 V vs. standard hydrogen electrode (SHE)), similar to that of Li (− 3.04 V vs. SHE) but much lower than that of Mg (− 2.37 V vs. SHE). Furthermore, these divalent metals offer higher volumetric capacities (Ca: 2073 mAh cm −3 ; Mg: 3833 mAh cm −3 ) than Li 2 – 5 . Thus, the cell voltage and energy density of Ca batteries are expected to be comparable to and higher than those of Li-ion and Mg batteries, respectively.…”