LiDFOB Initiated In Situ Polymerization of Novel Eutectic Solution Enables Room‐Temperature Solid Lithium Metal Batteries

Abstract

It is demonstrated that a novel eutectic solution including 1,3,5-trioxane (TXE) and succinonitrile (SN) can be converted into solid-state polymer electrolyte (SPE) via in situ polymerization triggered by lithium difluoro(oxalato)borate (LiDFOB). It is worth noting that all the precursors (LiDFOB, TXE, and SN) of this novel SPE are totally solid and nonvolatile at room temperature, where, LiDFOB works as a lithium salt and an initiator simultaneously to avoid the introduction of impurity. It is noted that such SPE presents a considerable ionic conductivity of 1.14 × 10 −4 S cm −1 and a sufficiently wide electrochemical window of 4.5 V, which is significant for supporting the high-energy lithium batteries. In addition, this dedicatedly designed in situ polymerization is powerful to build kinetically favorable polymer-based protective layers on LiCoO 2 cathode and Li metal anode simultaneously, guaranteeing outstanding cycling stability (capacity retention of 88% after 200 cycles) of 4.3 V LiCoO 2 /lithium metal batteries at room temperature. More intriguingly, soft packed LiCoO 2 /SPE/Li metal batteries can still light a blue light emitting diode (LED) under the harsh conditions of being bent, cut, and stroked by a hammer, demonstrating excellent safety characteristics.

Toward Low‐Temperature Lithium Batteries: Advances and Prospects of Unconventional Electrolytes

“…in 2020, Cui's group demonstrated a new kind of SN-based solid polymer electrolyte via an in situ polymerization of novel eutectic solvent including 1,3,5trioxane (TXE) and SN initiated by lithium difluoro(oxalato) borate (LiDFOB). [47] MD simulations and other characterization verified that there exists a uniform supermolecular structure in this solid-state polymer electrolyte (SPE) (Figure 11), which can significantly suppress the motion of SN and thus prevent the reaction between SN and Li metal. Meanwhile, this SPE is favorable to form robust polymer-based protective layer on LiCoO 2 and Li, simultaneously.…”

“…In addition, the interfacial Reproduced with permission. [47] Copyright 2020, John Wiley and Sons. compatibility of SN with other negative electrode materials (graphite, silicon) remains a challenge.…”

“…b) Radial distribution functions g(r) of Li-SN, Li-POM, and POM-SN pairs calculated from MD simulation trajectories at 353 K. c) 1 H magic angle spinning (MAS) NMR of POM, SN, and POM-SN mixture. d) Comparison of PSL53 and SN-LiDFOB electrolyte.Reproduced with permission [47]. Copyright 2020, John Wiley and Sons.…”

Deep Eutectic Solvents for Boosting Electrochemical Energy Storage and Conversion: A Review and Perspective

“…Several eutectic electrolytes have been designed for Li metal anode to prevent Li dendrite growth. [66,67] For example, Cui et al reported succinonitrile (SN)-based dual-anion DES as a highsafety electrolyte for Li metal batteries. [67] The as-fabricated SNbased DES exhibited a high ionic conductivity of 2.86 mS cm −1 with a large Li transfer number of 0.44 at 25 °C, and good interfacial compatibility toward the Li metal.…”

“…Several eutectic electrolytes have been designed for Li metal anode to prevent Li dendrite growth. [ 66,67 ] For example, Cui et al. reported succinonitrile (SN)‐based dual‐anion DES as a high‐safety electrolyte for Li metal batteries.…”