Potential-Controlled Pre-SEI Regulation for Improved Lithium Reversibility in Anode-Free Solid-State Lithium Metal...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Anode-free solid-state lithium metal batteries (AF-SSLMBs) offer high safety and energy density.
• Low Coulombic efficiencies (CEs) due to undesirable solid electrolyte interface (SEI) formation and irreversible lithium (Li) deposition/dissolution hinder AF-SSLMB performance.

Purpose of the Study:

• To develop a pre-SEI strategy to mitigate Li loss and improve Li deposition/dissolution behavior in AF-SSLMBs.
• To enhance the Coulombic efficiency and cycling stability of AF-SSLMBs.

Main Methods:

• A pre-SEI was engineered using a potentiostatic electrolyte decomposition method with ethoxy-pentafluoro-cyclotriphosphazene (PFPN) as an additive.
• The potentiostatic holding at 0.5 V induced simultaneous decomposition of PFPN and lithium salts, forming a dense, double-layered pre-SEI.
• The performance of AF-SSLMBs with and without the pre-SEI was evaluated using Li|Cu cells and Cu||LFP pouch cells.

Main Results:

• The pre-SEI exhibited high ionic conductivity, facilitating fast Li+ transport and suppressing Li loss during SEI formation.
• A high initial CE (ICE) of 95.5% and a stable CE of 98.7% were achieved in Li|Cu cells, representing significant improvements over the control.
• The cycling life of the AF-SSLMB pouch cell (Cu||LFP) was extended fivefold, maintaining 44.9% capacity retention after 100 cycles.

Conclusions:

• The pre-SEI strategy effectively reduces Li loss associated with SEI formation and Li plating/stripping processes in AF-SSLMBs.
• This method offers a scalable approach to enhance the Coulombic efficiency and cycle life of high-safety, high-energy-density AF-SSLMBs.