Metal sulfides have attracted significant attention in sodium-ion battery research owing to their high theoretical capacity. However, their practical application is hindered by volume fluctuations and low conductivity caused by conversion reactions. In this study, hollow cobalt disulfide/nitrogen-doped carbon (CoS₂/NC) nanoboxes were synthesized from cobalt-based Prussian blue analogues (PBA) through a sulfidation process. The resulting nanoboxes, approximately 500 nm in size, possess hollow interiors constructed from interconnected primary nanoparticles (~ 50 nm). The unique hierarchical structure provides abundant void space to accommodate volume changes and shortens transport pathways. Furthermore, the integration of nitrogen-doped carbon matrix significantly enhances the electronic conductivity. When employed as an anode material for sodium-ion batteries, hollow CoS₂/NC nanoboxes delivered an outstanding desodiation capacity of 619.4 mAh·g⁻¹ at 5 A·g⁻¹ over 400 cycles with an average capacity loss of only 0.04% per cycle. This study highlights the potential of PBAs as precursors for synthesizing nanoscale metal sulfides with nitrogen-doped carbon matrices, offering a promising approach to enhance electrochemical performance in energy storage systems.

Cobalt sulfide catalysts (CoS and CoS₂) with different phases, electrical conductivities, porosities, and specific surface areas are synthesized and loaded on a carbon paper (CP) interlayer which has a role to support an electrically conductive network for maximizing the catalytic activity of cobalt sulfide. Based on the detailed diagnosis about electrochemical results, cobalt sulfides reveal their electrocatalytic activity to promote both polysulfide reduction and Li₂S nucleation during discharge. We propose a new interpretation about the capacity vs. voltage profiles of Li–S cells, which can elaborate on the reduction reaction of sulfur during the discharge reaction. Through the electrochemical examination, we determine the role of cobalt sulfide catalysts as well as CP interlayer and the critical factors of cobalt sulfides for the enhanced performances of Li–S batteries. Our work provides new insights for understanding about the catalytic activity of cobalt sulfides and designing advanced catalysts for the high utilization of sulfur in Li–S batteries.

The lithium (Li) metal anode is regarded as the upcoming generation of battery anodes due to its high theoretical capacity (3860 mAh g⁻¹) and low standard reduction potential (−3.04 vs SHE). Addressing challenges related to the formation of Li metal dendrites, such as short circuits and low Coulombic efficiency, is crucial for the practical implementation of Li metal anodes. Previous research on Li metal has primarily focus on the Li plating process for achieving homogeneous growth. However, our study highlights the significance of pit formation variations, which significantly influence Li growth behavior in subsequent cycles. Expanding on this understanding, we formulated electrochemical activation conditions to promote uniform pit formation, thereby doubling the cycle life in a symmetric cell, and increasing the capacity retention of NCM622||Li full-cell from 68.7% to 79.5% after 500 cycles.

Lithium metal is commonly regarded as the "Holy Grail" anode material for high energy density rechargeable batteries. However, the uncontrollable growth of Li dendrites has posed safety concerns and thus greatly hindered its large-scale application. Here we have modified the surface of a commercial anode current collector, Cu foil, with a thin layer of Zn by a facile electroplating method, in order to regulate the Li nucleation and the following growth processes. Because of the formation of a solid solution buffer layer and Li-Zn alloy phases, the Li nucleation overpotential was dramatically reduced, realizing a uniform Li nucleation and a smooth Li plating morphology. As a result, significantly improved long-term cycling performance with a high Coulombic efficiency was achieved by the lithiophilic Zn coated Cu foil as a current collector. Full cells of Li-LiFePO₄ and Li-S using the Li deposited on the Zn modified Cu as the anode, showed increased capacity with low voltage hysteresis and greatly enhanced cycling stability, ascribed to the uniform Li deposition and formation of a stable solid electrolyte interphase (SEI) layer. This work demonstrates the feasibility of employing lithiophilic modified Cu foils as Li metal current collectors for practical applications.