A comprehensive review of pre-lithiation/sodiation additives for Li-ion and Na-ion batteries

Lithium/Sodium-ion batteries (LIB/SIB) have attracted enormous attention as a promising electrochemical energy storage system due to their high energy density and long cycle life. One of the major hurdles is the initial irreversible capacity loss during the first few cycles owing to forming the solid electrolyte interphase layer (SEI). This process consumes a profusion of lithium/sodium, which reduces the overall energy density and cycle life. Thus, a suitable approach to compensate for the irreversible capacity loss must be developed to improve the energy density and cycle life. Pre-lithiation/sodiation is a widely accepted process to compensate for the irreversible capacity loss during the initial cycles. Various strategies such as physical, chemical, and electrochemical pre-lithiation/sodiation have been explored; however, these approaches add an extra step to the current manufacturing process. Alternative to these strategies, pre-lithiation/sodiation additives have attracted enormous attention due to their easy adaptability and compatibility with the current battery manufacturing process. In this review, we consolidate recent developments and emphasize the importance of using pre-lithiation/sodiation additives (anode and cathode) to overcome the irreversible capacity loss during the initial cycles in lithium/sodium-ion batteries. This review also addresses the technical and scientific challenges of using pre-lithiation/sodiation additives and offers the insights to boost the energy density and cycle life with their possible commercial exploration. The most important prerequisites for designing effective pre-lithiation/sodiation additives have been explored and the future directions have been discussed.