Hybrid sodium-/zinc-ion battery systems: emerging approaches for low-cost and safe energy storage

Abstract

Hybrid sodium–zinc ion battery systems represent one of the next-generation energy storage technologies with potential for safely delivering affordable and sustainable performance. These hybrid batteries exploit the high natural abundance of sodium and the excellent electrochemical stability of zinc, enabling the advantages of sodium-ion and zinc-ion chemistries to be combined in a single device. A combination of the two types of charge storage enables sodium–zinc ion batteries to surpass certain limits of individual sodium-ion and zinc-ion batteries, in particular with regard to cycle life, material cost and even operational safety to some extent. The latest studies on hybrid sodium–zinc ion batteries have revolved around the implementation of new cell architectures, including not only new electrode materials but also dual-ion transport schemes, as a way of exploiting better overall electrochemical performance. Such design solutions have led to an increase in energy density, rate capability and cycling stability. The synergistic approaches to materials like Prussian blue analogue cathodes combined with sodium-rich electrolyte environments and zinc metal components have proved effective in reducing certain degradation pathways, including the growth of zinc dendrites and dissolution of the active material. The key aspect which makes the sodium–zinc battery so distinct in the present scenario compared to other batteries such as the lithium-ion battery and the individual sodium-ion or zinc-ion battery lies within its cost, lifespan, and inherent safety features. It has entered the limelight as one of the most preferred contenders for the storage of grid energy and renewable energy integration, along with being applied for the utilization of portable devices owing to its sustainability. Challenges persist at the interfaces of electrode and electrolyte optimization, long-term operational stability, and scalable manufacturing processes. This review summarizes recent progress and outlines the major research directions towards the advancement of hybrid sodium–zinc ion batteries as a reasonable alternative energy storage technology in the post-lithium era.