The rapid growth of miniaturized electronics has led to an urgent demand for microscale energy storage devices (MESDs) to sustainably power the micro electronic devices. However, most MESDs reported to date have suffered from the limited energy densities and shape versatility compared to conventional large-scale counterparts because of the architectural constraints inherent in microfabrication-based cell manufacturing and cell dimension/structure. This review addresses the cell architecture design for MESDs that can achieve both miniaturization and high energy density. We provide a comprehensive overview of five types of cell architectures of MESDs and their fabrication techniques. In addition, to enable practical applications of MESDs, several cell design approaches are presented with the aim of minimizing the inactive parts of the cell and maximizing the performance metrics of MESDs. Finally, we discuss development direction and outlook of MESDs with a focus on materials chemistry, energy-dense electrochemical systems, and cell performance normalization, which will help to expand their applications and manufacturing scalability.

Challenges facing high-voltage/high-capacity cathodes, in addition to the longstanding problems pertinent to lithium (Li)-metal anodes, should be addressed to develop high-energy-density Li-metal batteries. This issue mostly stems from interfacial instability between electrodes and electrolytes. Conventional carbonate- or ether-based liquid electrolytes suffer from not only volatility and flammability but also limited electrochemical stability window. Here, we report a nitrile electrolyte strategy based on concentrated nitrile electrolytes (CNEs) with co-additives. The CNE consists of high-concentration lithium bis(fluorosulfonyl)imide (LiFSI) in a solvent mixture of succinonitrile (SN)/acetonitrile (AN). The SN/AN solvent mixture is designed to ensure high oxidation stability along with thermal stability, which are prerequisites for high-voltage Li-metal cells. The CNE exhibits interfacial stability with Li metals due to the coordinated solvation structure. Lithium nitrate (LiNO₃) and indium fluoride (InF₃) are incorporated in the CNE as synergistic co-additives to further stabilize solid-electrolyte interphase (SEI) on Li metals. The resulting electrolyte (CNE + LiNO₃/InF₃) enables stable cycling performance in LiLiNi_0.8Co_0.1Mn_0.1 and 4.9 V-class LiLiNi_0.5Mn_1.5O₄ cells. Notably, the LiLiNi_0.5Mn_1.5O₄ cell maintains its electrochemical activity at high temperature (100 ℃) and even in flame without fire or explosion.