Carbon-based current collectors for stable aqueous Zn anodes

Abstract

Aqueous Zn metal batteries (AZMBs) have emerged as promising energy-storage systems owing to their inherent safety, environmental compatibility, and cost-effectiveness. However, their practical application is severely hindered by critical challenges pertaining to Zn anodes, including uncontrolled dendrite growth and parasitic side reactions at this anode. Although employing excess Zn foil can mitigate anode failure, this strategy inevitably compromises the energy density of full batteries. Recent advances have demonstrated that current collector design coupled with controlled electrodeposition can generate high-quality Zn deposits, which effectively suppress dendrite formation and side reactions. Carbon-based materials featuring favorable electrical conductivities, tunable architecture, and exceptional chemical stabilities have shown unique advantages in constructing/modifying current collectors. This review systematically summarizes the recent progress in the design of carbon-based current collectors for AZMBs, categorizing their functional roles and elucidating the structure–performance relationships that govern Zn deposition behaviors. Mechanistic insights into how carbon materials regulate the Zn plating/stripping processes are provided. Finally, future research directions are proposed to guide the development of advanced current collectors for high-performance AZMBs.

1. Introduction

Aqueous Zn metal batteries (AZMBs) have emerged as a promising alternative to lithium-ion batteries owing to their economic benefits, high theoretical capacities (820 mAh·g−1 and 5855 mAh·cm−3), and favorable redox potential (−0.76 V vs. standard hydrogen electrode). The inherent safety and superior ion transport kinetics of aqueous electrolytes further underscore the potential of AZMBs. Commercial Zn foil remains the predominant anode material; however, Zn metal anodes face substantial challenges that impede broad application, including surface and internal defects, dendrite formation, and parasitic side reactions.

To address these issues, a common strategy is to use excess metal in the anode, resulting in a negative-to-positive (N/P) ratio exceeding 20. This approach, however, can cause low metal utilization and depth of discharge below 5%, reducing overall energy density. Hence, achieving fully reversible Zn plating/stripping during cycling is imperative. Recent strategies have focused on electrolyte engineering, separator optimization, and interfacial manipulation. A critical yet relatively underexplored strategy is the design of current collectors (CCs), which facilitate electron transfer and support active material loading. Effective integration of CCs reduces the risk of perforation caused by repeated cycling, improves Zn utilization, and enhances energy density.

Carbon-based materials have gained increasing attention for CC applications. Three-dimensional (3D) carbon structures, characterized by high surface area and electrical conductivity, effectively reduce local current density, suppress the tip effect, and promote uniform Zn deposition, while mitigating volume changes. Two-dimensional (2D) materials, such as graphene, MXene, and others, serve as modified layers to induce directed Zn deposition or as carriers to regulate deposition behavior through functional groups or single atoms. Despite significant progress, systematic design guidelines remain scarce, as the fundamental mechanisms by which carbon materials influence Zn deposition are not fully understood. This review summarizes the latest advances in carbon-based current collectors for stable aqueous Zn anodes.