Electrochemically-Matched and Nonflammable Janus Solid Electrolyte for Lithium–Metal Batteries

Abstract

Solid-state batteries based on ceramic electrolytes are promising alternatives to lithium-ion batteries with better safety and energy density. While solid electrolytes such as the garnet-type Li 7 La 3 Zr 2 O 12 (LLZO) are chemically stable with lithium metal, their rigidity leads to poor interfacial contact with the cathodes. Nonflammable organic phosphates, however, are characterized by a liquid nature and can immerse the conventional porous cathodes to form a good contact. However, the phosphates are unstable with lithium metal anodes. We design a quasi-solid Janus electrolyte based on the ceramic LLZO and a trimethyl phosphate (TMP) gel which combines the best of both worlds. The electrochemical window of the Janus electrolyte is significantly extended compared with the TMP to accommodate the lithium metal anode. The contact between the cathode and the electrolyte is maintained by the semifluid nature of the TMP gel. A lithium−metal battery with such a Janus electrolyte can stably cycle at room temperature at 1C while still retaining a capacity of 115 mAh g −1 over 100 times. In contrast, the batteries based on LLZO and TMP individually cannot function properly. More importantly, despite the quasi-solid nature, the battery does not contain flammable functional parts and can alleviate the safety concerns of current batteries containing organic-type electrolytes. This work provides a simple but effective strategy for safe, inexpensive, and energy-dense solid-state batteries.

Vertically Heterostructured Solid Electrolytes for Lithium Metal Batteries

“…Due to the flammability of polymers, the SPEs are risked by combustion hazards. Lu and co‐workers designed a quasi‐solid asymmetric LMSSS in which a fire‐retardant trimethyl phosphate (TMP) gel form a good contact by immersing the porous cathode and the ceramic LLZO with modified interface contacts with Li metal [ 95 ] (Figure 9d,e).…”

“…Reproduced with permission. [ 95 ] Copyright 2021, American Chemical Society. f) Strategy of heterogenous SPE with selected electrochemical stability to protect the ceramic SSE.…”

Optimized Interfaces in Anti-Perovskite Electrolyte-Based Solid-State Lithium Metal Batteries for Enhanced Performance

“…Applying pressure to the assembly of electrode and electrolyte was generally used to pursue good contact between the different layers ( Zhang et al, 2017 ). Constructing a polymer–oxide–polymer sandwich composite electrolyte can also improve the interface contact ( Lu et al, 2019 ; Li et al, 2021 ). However, due to the poor mobility of the solid material, the interface of the lithium anode electrolyte and the SSE pellet is unavoidable to become solid–solid point contact ( Janek and Zeier, 2016 ; Zhang et al, 2017 ; Lu et al, 2019 ; Li et al, 2021 ).…”

“…Constructing a polymer–oxide–polymer sandwich composite electrolyte can also improve the interface contact ( Lu et al, 2019 ; Li et al, 2021 ). However, due to the poor mobility of the solid material, the interface of the lithium anode electrolyte and the SSE pellet is unavoidable to become solid–solid point contact ( Janek and Zeier, 2016 ; Zhang et al, 2017 ; Lu et al, 2019 ; Li et al, 2021 ). The limited contact area blocks the Li + transport channel and significantly increases the interface impedance ( Lu et al, 2019 ; Li et al, 2021 ).…”

“…However, due to the poor mobility of the solid material, the interface of the lithium anode electrolyte and the SSE pellet is unavoidable to become solid–solid point contact ( Janek and Zeier, 2016 ; Zhang et al, 2017 ; Lu et al, 2019 ; Li et al, 2021 ). The limited contact area blocks the Li + transport channel and significantly increases the interface impedance ( Lu et al, 2019 ; Li et al, 2021 ). In cycling of the cell, dreadful interface physical contact aggravates the uneven deposition of the Li + , which eventually leads to dendrite growth and battery failure ( Janek and Zeier, 2016 ; Xu et al, 2018 ; Lu et al, 2019 ; Xiao et al, 2020 ).…”