A Cost-Effective Sulfide Solid Electrolyte Li₇P₃S_7.5O_3.5 with Low Density and Excellent Anode Compatibility

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Commercialization of all-solid-state Li batteries (ASSLBs) requires solid electrolytes with cost-competitiveness, low density, and anode compatibility.
• Existing oxide, sulfide, and chloride solid electrolytes do not simultaneously meet these critical requirements.
• Anode compatibility is crucial, while cathode compatibility can be addressed by established coating techniques.

Purpose of the Study:

• To design and synthesize a novel solid electrolyte material for ASSLBs.
• To evaluate the cost, density, anode compatibility, and electrochemical performance of the new material.
• To assess the potential of the developed solid electrolyte for commercial ASSLB applications.

Main Methods:

• Synthesis of Li7P3S7.5O3.5 (LPSO) solid electrolyte using cost-effective raw materials (excluding expensive Li2S).
• Characterization of LPSO's density and comparison with existing solid electrolytes.
• Electrochemical testing of Li|LPSO|Li symmetric cells and all-solid-state pouch cells with Si anodes.

Main Results:

• LPSO exhibits a low raw material cost of $14.42/kg, significantly below the commercialization threshold.
• LPSO has a low density of 1.70 g/cm³, lower than oxide and chloride electrolytes.
• Stable cycling in Li|LPSO|Li cells for over 4200 hours and 89.29% capacity retention in Si anode pouch cells after 200 cycles at 60°C.

Conclusions:

• The developed Li7P3S7.5O3.5 solid electrolyte simultaneously fulfills cost, density, and anode compatibility requirements for ASSLBs.
• LPSO demonstrates promising electrochemical stability and performance, making it a viable candidate for next-generation solid-state batteries.
• The material's characteristics support its potential for cost-effective commercialization of all-solid-state Li batteries.