C. Francis, Senior R&D Engineer, PMB Defence Engineering Pty Ltd, 715 Mersey Road North, Osborne, SA 5017, Australia
K. Bradley, Electrochemist, PMB Battery Technologies Ltd, Units 31 and 32, Rassau Industrial Estate, Ebbw Vale, NP23 5SD, United Kingdom
C. Breach, R&D Manager, PMB Battery Technologies Ltd, Units 31 and 32, Rassau Industrial Estate, Ebbw Vale, NP23 5SD, United Kingdom
A. P. Karpinski, Integrated Battery Technology LLC, Stonington, CT 06379, United States

Abstract — Aqueous Nickel-Zinc rechargeable battery technology has high potential to address the challenging energy storage demands of modern submarines. Offering approximately twice the energy density compared to conventional lead-acid batteries and increased safety due to the non-flammable aqueous electrolyte, NiZn batteries have the potential to offer enhanced operational flexibility and safety in nuclear and conventional submarines. Despite limited public-domain literature on NiZn battery technologies for submarines, recent advancements in chemistry and materials science of electrode materials are enhancing the operational performance of NiZn batteries in submarine applications.

A critical performance consideration for NiZn batteries is the memory effect of recent cell history, also known as voltage depression, which stems from the physical properties of the electrode materials. The underlying causes of memory effects in NiZn cells are not widely discussed in literature. Generally, memory effects in electrochemical cells are the result of morphological changes in active materials during repeated partial discharge cycles that change the electrical properties of the electrodes resulting in voltage depression, reversible capacity loss and reduced power delivery. An increased understanding of the fundamentals behind memory effects in NiZn cells can improve management and mitigation approaches and therefore cell performance.

The memory effect in NiZn cells can be addressed with innovative materials chemistry and electrode processing. This review presents the fundamental electrochemistry of NiZn electrodes in alkaline electrolyte, examines the specific implications of voltage depression for submarine battery architectures, and evaluates established and emerging mitigation strategies in other battery chemistries that could be applied to NiZn. These include optimized charging protocols, electrolyte additives, electrode formulation (doping/alloying), and system level management approaches. Emphasis is placed on the high reliability and long-life requirements of submarines.