Solid Electrolyte Interphase (SEI), a boon or a bane for lithium batteries: A review on the recent advances

The inception of an unprecedented commercial and rechargeable lithium-ion battery in 1991 opened doors for enhancement in portable electronics, as well as electric vehicles. Li-ion batteries prove advantageous over other kinds in their high energy density, no memory effect (except lithium iron phosphate cells), and low self-discharge. Despite the promising nature of the battery, its fabrication poses hurdles and there is room for improvement in battery properties such as specific energy, power density, and cyclability. Enhancements in surface morphology and kinetics can play a vital role. A passivation layer, namely the Solid Electrolyte Interphase (SEI) is generated on the anode surface in batteries, which fundamentally decomposes the electrolyte, and regulates the flow of ions. Consequently, it increases the impedance and resistance of the battery. The chemical composition, transport properties, thickness, and mechanical features of the SEI are crucial in refining long-term battery stability. Therefore, having a profound understanding of the interface chemistry and formation mechanism is imperative in amplifying the performance of the battery. This review emphasizes the recent progress at a surface level, specifically the anode. A brief description of the characterization of SEI, its advantages and disadvantages is provided. A concise review on alternatives such as artificial SEI, single-ion electrolytes, electrolyte additives, inlaying a separator between electrode and electrolyte, single and dual-layered surface coatings, downsizing, and alloying metals has been collated in this paper.