A strong Lewis acid imparts high ionic conductivity and interfacial stability to polymer composite electrolytes towards all-solid-state Li-metal batteries

Abstract

The development of high-performance solid polymer electrolytes is crucial for producing all-solid-state lithium metal batteries with high safety and high energy density. However, the low ionic conductivity of solid polymer electrolytes and their unstable electrolyte/electrode interfaces have hindered their widespread utilization. To address these critical challenges, a strong Lewis acid (aluminum fluoride (AlF 3 )) with dual functionality is introduced into poly(ethylene oxide) (PEO)-based polymer electrolyte. The AlF 3 facilitates the dissociation of lithium salt, increasing the iontransfer efficiency due to the Lewis acid-base interaction; further the in-situ formation of lithium fluoride-rich interfacial layer is promoted, which suppresses the uneven lithium deposition and continuous undesired reactions between the Li metal and PEO matrix. Benefiting from our rational design, the symmetric Li/Li battery with the modified electrolyte exhibits much longer cycling stability (over 3600 h) than that of the pure PEO/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte (550 h). Furthermore, the all-solid-state LiFePO 4 full cell with the composite electrolyte displays a much higher Coulombic efficiency (98.4% after 150 cycles) than that of the electrolyte without the AlF 3 additive (63.3% after 150 cycles) at a large voltage window of 2.4-4.2 V, demonstrating the improved interface and cycling stability of solid polymer lithium metal batteries.

Thermal‐Stable Separators: Design Principles and Strategies Towards Safe Lithium‐Ion Battery Operations

“…Blending modification uniformly disperses separator substrates with functional elements into precursors, which are processed to produce a separator. Inorganic materials have good thermal stability and excellent ionic conductivity (sulfide superionic separator) even exceeding that of liquid electrolytes [164–168] . However, the preparation of inorganic separators by high‐temperature sintering leads to high energy consumption.…”

“…Inorganic materials have good thermal stability and excellent ionic conductivity (sulfide superionic separator) even exceeding that of liquid NCM/ Li 161, 155.6, 140, 135 mAh g À 1 @ 0.1, 0.2, 0.5, 1 C; 94.9 % @ 0.1-0.5 C after 80th cycle (25 °C) [157] [a] MOD: modification; THK: thickness; TS: tensile strength; EC: electrochemical; σ i : ionic conductivity; P/N: positive/negative; LMFP: LiMn 0.8 Fe 0.2 PO 4 ChemSusChem electrolytes. [164][165][166][167][168] However, the preparation of inorganic separators by high-temperature sintering leads to high energy consumption. At the same time, poor mechanical strength and flexibility on account of brittleness hinder practical applications.…”

Opportunities of Flexible and Portable Electrochemical Devices for Energy Storage: Expanding the Spotlight onto Semi-solid/Solid Electrolytes

“…Lithium metal batteries (LMBs) employing Li metal as the anode electrode are regarded as the important lithium batteries because Li metal can provide high theoretical specific capacity of 3860 mAh g –1 , which is about 10 times that of commercially used graphite anode (372 mAh g –1 ). Li metal also provides low negative electrochemical potential (−3.04 V vs the standard hydrogen electrode), which can maximize the capacity density and voltage window for increasing energy density. − However, different from graphite anodes in LIBs, LMBs rely on the stripping and plating of Li metal anodes . One important practical barrier of using the Li metal anodes is their tendency to form uneven and unstable needle-like Li crystals that are known as the Li dendrites during charge–discharge cycles .…”

A sulfur-containing polymer-plasticized poly(ethylene oxide)-based electrolyte enables highly effective lithium dendrite suppression

“…23 To overcome this issue, some special llers have been developed to stabilize the interface of Li metal anode and solid electrolyte, such as Li 2 S, 24 LiNO 3 , 25 LiF, 26 Li 2 S 6 , 27 and AlF 3 . 28 These additives can be involved in SEI generation, or promoting the decomposition of Li salts, and nally, robust SEIs can be formed to suppress the Li dendrite. An alternative strategy has been developed to eliminate Li dendrite by introducing active materials, e.g., Si 29 and I 2 , 30 into CPEs, because the growth of Li dendrites is inevitable and will eventually pierce the SEI lm.…”