Facile Construction of Nanofilms from a Dip-Coating Process to Enable High-Performance Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Solid-state electrolytes (SSEs) offer higher energy density and safety compared to liquid electrolytes for next-generation energy storage.
• However, solid-to-solid contact in SSEs leads to interfacial instability, hindering battery performance.
• Controlling the electrode/electrolyte interface is crucial for advancing solid-state battery technology.

Purpose of the Study:

• To develop an efficient surface modification technique for garnet-type Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZT) solid-state electrolytes.
• To investigate the impact of a magnesium oxide (MgO) interlayer on the LLZT/Li interface properties.
• To evaluate the performance of solid-state batteries employing the modified LLZT electrolyte.

Main Methods:

• Utilized a dip-coating technique with polyvinyl pyrrolidone (PVP) to create uniform MgO nanofilms on LLZT pellets.
• Characterized the LLZT/Li interface before and after MgO interlayer formation.
• Assembled and tested symmetrical Li cells and full cells with commercial cathode materials.

Main Results:

• The MgO interlayer dramatically reduced interfacial resistance from 1652 Ω cm² to 6 Ω cm².
• The modified LLZT electrolyte enabled Li symmetrical cells to achieve a high critical current density of 1.2 mA cm^-2 and long-term cycling (>4000 h).
• Full cells demonstrated excellent cyclability and high rate performance at 25 °C.

Conclusions:

• A facile liquid-phase method enables precise and controllable surface modification of solid-state electrolytes.
• The MgO interlayer is highly effective in stabilizing the LLZT/Li interface.
• This interface engineering approach is essential for realizing high-performance solid-state batteries.