Electrolyte design implications of ion-pairing in low-temperature Li metal batteries

Abstract

Lithium metal batteries are capable of pushing cell energy densities beyond what is currently achievable with commercial Li-ion cells and are the ideal technology for supplying power to electronic devices...

Low‐Temperature High‐Areal‐Capacity Rechargeable Potassium‐Metal Batteries

“…These areal capacities outperform the most previous works about alkalimetal batteries at the same temperatures (Figure 1e). [22,[33][34][35][36][37][38][39][40][41][42][43][44][45][46] Furthermore, a K-Te pouch cell (4 cm × 6 cm) with a mass loading of 3 mg cm −2 was successfully fabricated (Figure 1f), and it delivered a high capacity of 14.2 mAh and retained 88% of the initial capacity after 30 cycles at −40 °C (Figure 1g,h), demonstrating its great potential for practical low-temperature applications.…”

“…[19,20] Meanwhile, the drastically increased desolvation energy at low temperatures also causes large electrode polarization and deteriorates the rate performance of the batteries. [21][22][23] So, it is necessary to adopt an electrolyte with both high ionic conductivity and low desolvation energy to overcome the unfavorable conditions at decreased temperatures. Notably, potassium ions (K + ) possess a smaller Stokes radius compared to lithium/sodium ions due to their weaker Lewis acidity, which endow K + electrolytes with high ionic conductivity and fast ion diffusion.…”

A −60 °C Low‐Temperature Aqueous Lithium Ion‐Bromine Battery with High Power Density Enabled by Electrolyte Design

“…Nevertheless, seldom rechargeable ALIBs or non‐aqueous lithium‐ion batteries (LIBs) can achieve high power density at low temperatures. [ 6 ] Compared with non‐aqueous electrolytes, aqueous electrolytes with low viscosity and high safety have intrinsic advantages under low temperatures and high rate circumstances. [ 2,7 ] Therefore, ALIBs have the potential to maintain excellent capacity and power densities at low temperatures, as long as the following two problems are settled: i) the high freezing point of aqueous solutions causing the dramatic decline in the conductivities of electrolytes at low temperatures; ii) the sluggish kinetics derived from both de‐solvation and bulk diffusion steps impeding lithium ions fast de‐/intercalation in the electrode materials.…”

“…On the other hand, adding salts with high solubilities, such as LiCl and LiTFSI, is considered a safe, effective, and promising route for building low‐temperature electrolytes of ALIBs. [ 6d,11 ] However, the unsatisfactory specific capacity of electrode materials even at the low current density (≤0.2 A g –1 ), such as LiMn 2 O 4 (63 mAh g –1 , −40 °C), [ 11b ] LiCoO 2 (65 mAh g –1 , −40 °C), [ 11a ] LiTi 2 (PO 4 ) 3 (65 mAh g –1 , −50 °C), [ 10 ] and LiFePO 4 (36 mAh g –1 , −20 °C), [ 8 ] greatly limits the rapid development of ALIBs. Even though some strategies (nanosize and surface modification) to improve the low‐temperature kinetics of electrode materials in non‐aqueous LIBs are worth referring and trying, [ 12 ] significant progress is rarely reported, which should be attributed to the sluggish electrochemical reaction nature of intercalation compounds at low temperatures.…”

High Entropy Electrolytes for Practical Lithium Metal Batteries

“…As will be discussed extensively in this study, we hypothesize that conductivities are intricately related with mesoscopic solvation structures including Li + clusters; increased clustering of ions due to poor ion dissociation in weakly solvating electrolytes 34,35 is expected to increase the hydrodynamic radius and hinder transport. 27 These weakly solvating electrolytes that form ion clusters possess improved electrochemical stability at the cost of ion conductivity, while strongly solvating electrolytes have high conductivity but poor stability, implying a trade-off in tuning solvation strength (Supplementary Fig. 3).…”