Stable Anion-Derived Solid Electrolyte Interphase in Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• High-energy lithium metal batteries face challenges from dendritic lithium deposition due to non-uniform solid electrolyte interphase (SEI) formation.
• Anion-derived SEI offers advantages for uniform lithium deposition but often performs poorly under practical conditions.

Purpose of the Study:

• To engineer a stable anion-derived SEI by regulating electrolyte anion structure using anion receptors.
• To enhance the stability and performance of lithium metal batteries.

Main Methods:

• Utilized tris(pentafluorophenyl)borane (TPFPB) as an anion receptor to interact with bis(fluorosulfonyl)imide (FSI-) anions.
• Investigated the effect of TPFPB on FSI- reduction stability and aggregate cluster structure in the electrolyte.
• Analyzed the decomposition pathway of FSI- to form lithium sulfide (Li2S).

Main Results:

• TPFPB decreased FSI- reduction stability and altered FSI- aggregate structures, promoting interaction with more Li ions.
• The decomposition of FSI- to Li2S was enhanced, leading to a more stable anion-derived SEI.
• In Li | LiNi0.5Co0.2Mn0.3O2 batteries, the TPFPB-modified SEI achieved 194 cycles, compared to 98 cycles for the routine SEI.

Conclusions:

• Regulating electrolyte anion structure with anion receptors is a viable strategy for constructing stable anion-derived SEI.
• This approach significantly improves the cycle life of lithium metal batteries under practical conditions.
• The findings offer a new direction for developing advanced SEI layers in next-generation batteries.