Manganese dioxide cathodes are inexpensive and have high theoretical capacity (based on two electrons) of 617 mAh g−1, making them attractive for low-cost, energy-dense batteries. They are used in non-rechargeable batteries with anodes like zinc. Only ∼10% of the theoretical capacity is currently accessible in rechargeable alkaline systems. Attempts to access the full capacity using additives have been unsuccessful. We report a class of Bi-birnessite (a layered manganese oxide polymorph mixed with bismuth oxide (Bi2O3)) cathodes intercalated with Cu2+ that deliver near-full two-electron capacity reversibly for >6,000 cycles. The key to rechargeability lies in exploiting the redox potentials of Cu to reversibly intercalate into the Bi-birnessite-layered structure during its dissolution and precipitation process for stabilizing and enhancing its charge transfer characteristics. This process holds promise for other applications like catalysis and intercalation of metal ions into layered structures. A large prismatic rechargeable Zn-birnessite cell delivering ∼140 Wh l−1 is shown.

Zinc alkaline anodes command significant share of consumer battery markets and are a key technology for the emerging grid-scale battery market. Improved understanding of this electrode is required for long-cycle deployments at kWh and MWh scale due to strict requirements on performance, cost, and safety. Here we give a modern literature survey of zinc alkaline anodes with levelized performance metrics and also present an experimental assessment of leading formulations. Long-cycle materials characterization, performance metrics, and failure analysis are reported for over 25 unique anode formulations with up to 1500 cycles and ∼1.5 years of shelf life per test. Statistical repeatability of these measurements is made for a baseline design (fewest additives) via 15 duplicates. Baseline design capacity density is 38 mAh per mL of anode volume, and lifetime throughput is 72 Ah per mL of anode volume. We then report identical measurements for anodes with improved material properties via additives and other perturbations, some of which achieve capacity density over 192 mAh per mL of anode volume and lifetime throughput of 190 Ah per mL of anode volume. Novel in operando X-ray microscopy of a cycling zinc paste anode reveals the formation of a nanoscale zinc material that cycles electrochemically and replaces the original anode structure over long-cycle life. Ex situ elemental mapping and other materials characterization suggest that the key physical processes are hydrogen evolution reaction (HER), growth of zinc oxide nanoscale material, concentration deficits of OH– and ZnOH4 2–, and electrodeposition of Zn growths outside and through separator membranes.

h i g h l i g h t sZneMnO 2 battery was cycled at shallow DOD for more than 3000 cycles. Relatively low delivered cost of less than $150 per kWh. Mathematical model developed to understand the capacity fade mechanisms. Resistive film formation on the surface of MnO 2 particle during cycling. Change in SOC during cycling was used to measure capacity loss. Keywords:Rechargeable zincemanganese dioxide battery Cycle life ZneMnO 2 battery model Capacity fade model Film resistance a b s t r a c t Batteries based on manganese dioxide (MnO 2 ) cathodes are good candidates for grid-scale electrical energy storage, as MnO 2 is low-cost, relatively energy dense, safe, water-compatible, and non-toxic. Alkaline ZneMnO 2 cells, if cycled at reduced depth of discharge (DOD), have been found to achieve substantial cycle life with battery costs projected to be in the range of $100 to 150 per kWh (delivered). Commercialization of rechargeable ZneMnO 2 batteries has in the past been hampered due to poor cycle life. In view of this, the work reported here focuses on the long-term rechargeability of prismatic MnO 2 cathodes at reduced DOD when exposed to the effects of Zn anodes and with no additives or specialty materials. Over 3000 cycles is shown to be obtainable at 10% DOD with energy efficiency >80%. The causes of capacity fade during long-term cycling are also investigated and appear to be mainly due to the formation of irreversible manganese oxides in the cathode. Analysis of the data indicates that capacity loss is rapid in the first 250 cycles, followed by a regime of stability that can last for thousands of cycles. A model has been developed that captures the behavior of the cells investigated using measured state of charge (SOC) data as input. An approximate economic analysis is also presented to evaluate the economic viability of ZneMnO 2 batteries based on the experiments reported here.