Solid-state batteries promise greater safety and higher energy density—but their solid electrolytes face a fundamental trade-off.
Most highly conductive inorganic solid-state electrolytes rely on lithium-rich compositions. Adding more lithium can increase the number of potential charge carriers, but not all lithium ions participate in ion transport. Some lithium ions remain bound within the material structure and do not contribute to long-range transport. High lithium content also increases resource use and may lead to greater chemical and electrochemical instability. This raises a central question for solid-electrolyte design: Can a solid electrolyte be designed with lean-lithium content yet high ionic conductivity and high stability?
A research team led by Professor Chunpeng Yang at Tianjin University proposed an interfacial percolation strategy for lean-lithium oxychloride solid electrolytes.
Building a connected interfacial percolation network
The researchers embedded insulating nanocrystals as dispersed phases in an amorphous matrix. The nanocrystals reconstructed the interphase, optimized the interfacial lithium-ion distribution, and formed a continuous interfacial transport network.
At low oxide contents, the interfacial regions remain isolated. As the nanocrystal content increases, neighboring interfacial regions gradually connect. At the optimal composition, the interconnected interfaces form a continuous network throughout the electrolyte, much like local roads merging into a highway system. Beyond the optimal composition, excess oxide reduces the proportion and connectivity of the ion-conducting matrix, resulting in decreased ionic conductivity.
Advanced microscopy, spectroscopy and lithium-isotope tracing showed that lithium becomes enriched near the interfaces and preferentially exchanges and migrates through the interphase. The results support an interfacial transport mechanism that differs from conventional conduction through the bulk phase.
Less lithium, but highly efficient transport
Using this strategy, the researchers developed a representative percolative oxychloride electrolyte containing only 1.46 wt% lithium , while achieving a room-temperature ionic conductivity of 15.2 mS cm −1 . The result shows that highly efficient ion transport does not necessarily require a lithium-rich composition. Instead, conductivity can be enhanced by improving the connectivity of transport pathways and increasing the efficiency with which lithium ions participate in conduction.
High-voltage stability and long-life all-solid-state batteries
The representative electrolyte exhibits high-voltage stability up to 4.8 V . When paired with a high-nickel cathode, the resulting all-solid-state cells retained 85.3% of their capacity after 5,000 cycles at 2 C and 81.5% after 4,000 cycles at 6 C. Under high cathode loading, the cells delivered an areal capacity above 3 mAh cm −2 and retained 80.4% of their capacity after 800 cycles.
Versatility of the strategy
By varying the oxide nanocrystals, metal chlorides, and alkali-metal starting materials, the researchers prepared multiple percolative oxychloride electrolytes, indicating broad compositional and elemental compatibility. The strategy may enable further tuning of interfacial chemistry and transport-network connectivity, providing a route to lean-lithium solid electrolytes with balanced ionic conductivity, electrochemical stability, and electrode compatibility.
The interfacial percolation strategy provides a new design route for inorganic solid-state electrolytes with low lithium content and high ionic conductivity. Its tunability allows electrolyte properties to be further optimized, advancing the development of high-performance all-solid-state batteries.
National Science Review
Experimental study