Garnet Nb-Doped Li7La3Zr2O12 Ceramic Electrolyte and Its Composite Electrolyte for Solid-State Lithium Batteries

Lithium ion batteries (LIBs) have world-widely emerged as energy storage devices for electronic products, electric vehicles, energy storage systems and special purpose devices. LIBs are increasingly expected to be provided with a shorter battery charging time, a longer battery life and the better battery security for industrial development and social demand. However, most conventional LIBs with active organic liquid electrolytes have suffered from several issues, especially high safety risk and low energy density. Therefore, continuously improving conventional LIBs and designing new-type lithium batteries are extremely urgent. Solid-state lithium batteries (SSLBs) are recognized as the promising candidates of next generation lithium batteries with good safety and high energy density. Solid-state electrolytes (SSEs) as the most critical component in SSLBs largely lead the future battery development. To obtain the SSEs with good overall performance is a prerequisite to realize the potential of SSLBs. Garnet Li 7 La 3 Zr 2 O 12 (LLZO) ceramic SSEs have the great potential for SSLBs, owing to high ionic conductivity, wide stable potential window and good electrochemical stability against lithium metal. However, so far, LLZO ceramic SSEs still suffer from critical issues of poor air stability and hard machinability, greatly limiting their practical application. Hence, in this work, the cubic garnet Nb-doped LLZO, Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 , ceramic electrolyte is synthesized by a simple sol-gel process. Stability and mechanical properties of as-synthesized Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 ceramics are explored in detail. Directly polishing and assembling Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 ceramic pellets in analog batteries are applied to investigate electrochemical behaviours. In addition, the flexible composite membrane composed of Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 particles and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer matrix is successfully prepared through tape casting method. The composite membrane shows good machinability. When the composite membrane as electrolyte is applied in the lithium metal cell, good electrochemical performances are exhibited. The composite membrane integrating hard inorganic Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 ceramics with soft polymer achieves a gain effect of “1+1 > 2”. This work may be helpful for next forward-looking studies of garnet LLZO family SSEs and their extensions.