Li–Na-based hybrid battery

Li battery has been widely used in mobile electronic devices such as mobile phones and laptop computers and is currently expected as a power source for electric vehicles. Due to high cost and limited supply of Li sources, post-Li batteries like Na, K, Mg and Zn batteries have been researched intensively. However, the post-Li batteries face issues of low-energy density in monovalent ion (Na, K) batteries and slow ion diffusion in multivalent ion (Mg, Zn) batteries. The hybrid metal ion battery (HMIB) contains two different cations which can combine the benefits of fast ion diffusion of monovalent ions and high capacity of multivalent ions. Various types of HMIBs such as Na–Mg, Li–Mg, Li–Zn and so on have been studied. Among them, Li–Na HMIBs composed of Li-based cathodes and Na metal anode are the most promising as the post-Li battery owing to the application of matured Li technology and electrochemical/chemical similarity of Li to Na. In addition, dendric deposition of Na metal is suppressed by the shielding effect, allowing to employ Na metal anode in the Li–Na HMIB system. Na metal anode can provide higher capacity and reduce the material cost. Additionally, commercial Li cathode does not require further investment for manufacturing cathode materials, resulting in a significant reduction of development cost and rapid commercialization of the Li–Na HMIBs. Thus, in this review article, studies on the Li–Na HMIBs are summarized and analyzed, then future challenges for the development of Li–Na HMIBs are suggested.