Fundamentals of Electrolytes for Solid-State Batteries: Challenges and Perspectives

Abstract

Compared with traditional lithium-ion systems, solid-state batteries could achieve high safety and energy density. Although great improvements have been made, especially in solid-state electrolytes, fundamental challenges still remain for the solid-state systems in terms of chemistry and mechanics. This review summarizes the fundamental issues in solid-state batteries with a focus on three critical phenomena: (i) the principles of developing high ionic conductors, (ii) structural evolution at chemically unstable electrolyte-electrode interfaces, and (iii) the effects of manufacturing solid-state batteries, including electrode, and electrolyte design. The future perspectives are also outlined to guide the development of solid-state batteries.

Nano‐Scale Complexions Facilitate Li Dendrite‐Free Operation in LATP Solid‐State Electrolyte

“…From this contrast three regions can be differentiated: the crystalline LATP grains, thin and darker semi-amorphous regions to both sides at the crystalline grain interface, and a brighter amorphous region in the grain boundary center. Both grains are oriented in [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] hex zone axis. The highly symmetric bright reflexes in Figure 1c correspond to a [100] pc pseudocubic sublattice commonly assigned to partially occupied Li positions in the LATP crystal structure.…”

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Over the last two decades, several classes of highly ion-conductive SSEs have been developed which reach or surpass current liquid-state electrolyte conductivity. [5,6] Yet, no ASSB paying in on the above promises has been developed to date. This is mainly due to mechanochemical, chemical, and electrochemical stability issues and interfacial processes that have severely compromised any proposed cell's lifetime.

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Recent advancements in solid electrolytes integrated into all-solid-state 2D and 3D lithium-ion microbatteries

“…Ceramic materials with a crystal structure that can be designed to have high ionic conductivity and thermal stability are promising candidates for all-solid-state battery electrolytes. 19,136 The bulk properties can be better compared to glass and polymer electrolytes. 136 However, to obtain high total ionic conductivity, it is necessary to increase the grain boundary conductivity since the grain boundaries present a large barrier for ions' migration across the interfaces.…”

“…19,136 The bulk properties can be better compared to glass and polymer electrolytes. 136 However, to obtain high total ionic conductivity, it is necessary to increase the grain boundary conductivity since the grain boundaries present a large barrier for ions' migration across the interfaces. 18 As a result, diffusion with a slow ion transfer kinetics in electrolyte becomes the ratedetermining step, decreasing the performance of the microbattery.…”

Ultra-high throughput manufacturing method for composite solid-state electrolytes

“…Curtain coating offers a clear path to address the current bottlenecks associated with solid-state battery manufacturing ( Wang et al, 2020 ): it could enable high-throughput manufacturing compatible with existing infrastructure decreasing the barriers to market adoption and it offers new solutions for interface engineering. The implementation of curtain coating in other industries has proven that it can be carried out as a roll-to-roll process in conjunction with drying units as is currently used in the lithium battery industry for electrode fabrication.…”