zinc ion batteries

Keywords: Aqueous zinc-ion battery Sodium manganese oxide Mixed phase High energy density Aqueous zinc-ion batteries have been regarded as a promising alternative to large-scale energy storage, due to associated low-cost, improved safety and environmental friendliness. However, a high-performance cathode material for both rate capability and specific capacity is still a challenge. One kind of the more promising candidates are sodium manganese oxide (NMO) materials, although they suffer from individual issues and need to be further improved. Herein, we present a novel mixed phase NMO material composed of nearly equal amounts of Na 0.55 Mn 2 O 4 and Na 0.7 MnO 2.05. The structured configuration with particle size of 200-500 nm is found to be beneficial towards improving the ion diffusion rate during the charge/discharge process. Compared with Na 0.7 MnO 2.05 and Na 0.55 Mn 2 O 4 , the mixed phase NMO demonstrates an enhanced rate capability and excellent long-term cycling stability with a capacity retention of 83% after 800 cycles. More importantly, the system also delivers an impressive energy density and power density, as 378 W·h·kg −1 at 68.7 W·kg −1 , or 172 W·h·kg −1 at 1705 W·kg −1. The superior electrochemical performance is ascribed to the fast Zn 2+ diffusion rate because of a large ratio of capacitive contribution (63.9% at 0.9 mV·s −1). Thus, the mixed phase route provides a novel strategy to enhance electrochemical performance, enabling mixed phase NMO as very promising material towards large-scale energy-storage applications.

Aqueous zinc-ion batteries (ZIBs) are considered as a promising energy storage system due to their low cost and high safety merits. However, they suffer from the challenge of uncontrollable dendrite growth due to a non-uniform zinc deposition, which increases internal resistance and causes battery failure. Herein, Ag coating fabricated by a facile surface chemistry route on zinc metal was developed to guide uniform zinc deposition. Ag-coated Zn shows improved electrolyte wettability, a small zinc deposition overpotential, and fast kinetics for zinc deposition/dissolution. Direct optical visualization and scanning electron microscopy images show uniform zinc deposition due to the introduction of Ag coating. As a result, the Ag-coated Zn anode can sustain up to 1450 h of repeated plating/stripping with a low overpotential in symmetric cells at a current density of 0.2 mA cm −2 , while an improved performance is realized for full cells paired with a V 2 O 5-based cathode. This work provides a facile and effective approach to improve the electrochemical performance of ZIBs.

Aqueous zinc-ion batteries (ZIBs) have obtained increasing attention owing to the high safety, material abundance, and environmental benignity. However, the development of cathode materials with high capacity and stable cyclability is still a challenge. Herein, the polypyrrole (PPy)-wrapped V 2 O 5 nanowire (V 2 O 5 /PPy) composite was synthesized by a surface-initiated polymerization strategy, ascribing to the redox reaction between V 2 O 5 and pyrrole. The introduction of PPy on the surface of V 2 O 5 nanowires not only enhanced the electronic conductivity of the active materials but also reduced the V 2 O 5 dissolution. As a result, the V 2 O 5 /PPy composite cathode exhibits a high specific capacity of 466 mAh g −1 at 0.1 A g −1 and a superior cycling stability with 95% capacity retention after 1000 cycles at a high current density of 5 A g −1. The superior electrochemical performance is ascribed to the large ratio of capacitive contribution (92% at 1 mV s −1) and a fast Zn 2+ diffusion rate. This work presents a simple method for fabricating V 2 O 5 /PPy composite toward advanced ZIBs.