Robust interfaces enabled by chemically stable Li₃PO₄ buffer layer toward high-performance thin-film all-solid-state...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium phosphate (Li₃PO₄) is a key buffer layer for stabilizing interfaces in thin-film all-solid-state supercapacitors (ASSSCs).
• The P-O-P bonds in Li₃PO₄ are susceptible to dissociation, causing interfacial degradation and limiting device performance.
• Improving the chemical stability of Li₃PO₄ is crucial for advanced ASSSCs.

Purpose of the Study:

• To investigate the impact of oxygen partial pressure (P<0xE2><0x82><0x92>) during sputtering on Li₃PO₄ film bonding.
• To enhance the chemical stability and ionic conductivity of Li₃PO₄ buffer layers.
• To optimize Li₃PO₄ for improved electrochemical and electrochromic performance in ASSSCs.

Main Methods:

• Systematic investigation of Li₃PO₄ film deposition under varying oxygen partial pressures.
• Analysis of chemical bonding configurations using sputtering techniques.
• Electrochemical characterization of Li₃PO₄-coated ASSSCs, including capacitance, rate capability, and cycling stability tests.
• Evaluation of electrochromic properties.

Main Results:

• Controlled P<0xE2><0x82><0x92> effectively converted unstable P-O-P bonds to stable PO and Li-O-P configurations.
• Optimized Li₃PO₄ films exhibited enhanced ionic conductivity and interfacial stability.
• Li₃PO₄-coated ASSSCs showed significantly higher specific capacitance (22.5 vs. 9.0 mF cm⁻²), superior rate capability (11.2 vs. 0.9 mF cm⁻²), and better cycling stability (92.9% vs. 77.8% retention).
• The optimized films also demonstrated superior electrochromic functionality.

Conclusions:

• Oxygen partial pressure is a critical parameter for tailoring Li₃PO₄ film properties.
• Enhanced Li₃PO₄ buffer layers improve ASSSC performance and stability.
• These findings offer a pathway for developing high-performance energy storage devices and smart windows.