Joint Charge Storage for High‐Rate Aqueous Zinc–Manganese Dioxide Batteries

Abstract

Aqueous rechargeable zinc–manganese dioxide batteries show great promise for large‐scale energy storage due to their use of environmentally friendly, abundant, and rechargeable Zn metal anodes and MnO2 cathodes. In the literature various intercalation and conversion reaction mechanisms in MnO2 have been reported, but it is not clear how these mechanisms can be simultaneously manipulated to improve the charge storage and transport properties. A systematical study to understand the charge storage mechanisms in a layered δ‐MnO2 cathode is reported. An electrolyte‐dependent reaction mechanism in δ‐MnO2 is identified. Nondiffusion controlled Zn2+ intercalation in bulky δ‐MnO2 and control of H+ conversion reaction pathways over a wide C‐rate charge–discharge range facilitate high rate performance of the δ‐MnO2 cathode without sacrificing the energy density in optimal electrolytes. The Zn‐δ‐MnO2 system delivers a discharge capacity of 136.9 mAh g−1 at 20 C and capacity retention of 93% over 4000 cycles with this joint charge storage mechanism. This study opens a new gateway for the design of high‐rate electrode materials by manipulating the effective redox reactions in electrode materials for rechargeable batteries.

Layered Ca0.28MnO2·0.5H2O as a High Performance Cathode for Aqueous Zinc‐Ion Battery

“…[ 5,13 ] In the first step, the H + ions insert into δ‐MnO 2 and form MnOOH and ZnSO 4 ·3Zn(OH) 2 · x H 2 O, then the Zn 2+ ions intercalate into δ‐MnO 2 and form spinel ZnMn 2 O 4 in the following step. [ 14 ] Moreover, Pan et al also confirm the joint charge storage of Zn 2+ and H + ions of δ‐MnO 2 in 1 m Zn(TFSI) 2 /0.1 m Mn(TFSI) 2 . However, Kheawhom et al suggest that only Zn 2+ ions insert into δ‐MnO 2 and transform into δ‐ZnMnO 2 in 0.5 m ZnSO 4 electrolyte.…”

Toward a Reversible Mn4+/Mn2+ Redox Reaction and Dendrite‐Free Zn Anode in Near‐Neutral Aqueous Zn/MnO2 Batteries via Salt Anion Chemistry

“…[11,12] Different anion species may strongly affect the ion association properties in solution, possible side reactions, and even redox reactions in electrode materials. [13][14][15] Recently, an electrolyte-dependent reaction mechanism has been identified for the high-rate δ-MnO 2 cathode, where the bulky anion bis(trifluoromethane)sulfonimide (TFSI − ) in aqueous electrolytes leads to a joint nondiffusion-controlled Zn 2+ intercalation and H + conversion reaction. [13] It has been shown that the electrolyte media, especially the species of the anion salts, can tailor the reaction mechanism of electrode materials.…”

“…[13][14][15] Recently, an electrolyte-dependent reaction mechanism has been identified for the high-rate δ-MnO 2 cathode, where the bulky anion bis(trifluoromethane)sulfonimide (TFSI − ) in aqueous electrolytes leads to a joint nondiffusion-controlled Zn 2+ intercalation and H + conversion reaction. [13] It has been shown that the electrolyte media, especially the species of the anion salts, can tailor the reaction mechanism of electrode materials. The reaction mechanisms in aqueous Zn/MnO 2 batteries are complicated and still in dispute, however.…”

A Safe Polyzwitterionic Hydrogel Electrolyte for Long‐Life Quasi‐Solid State Zinc Metal Batteries

“…Among various candidates, zinc (Zn) metal with low electrochemical potential (−0.76 V vs SHE), high volumetric capacity (5850 mAh cm −3 ), low‐cost, and high safety shows promising prospect. [ 8–15 ] Nevertheless, the development of Zn metal batteries (ZMBs) is severely impeded by the limited cycling life of Zn stripping/plating, which is mainly attributed to the flagrant Zn dendrite formation, anode corrosion, and side reaction in aqueous electrolyte. [ 16,17 ] First, Zn dendrite, with the high Young modulus of about 108 GPa is probably fractured during cycling, which leads to continuous dead Zn accumulation and short circuit.…”