Improvement of density and electrochemical performance of garnet-type Li7La3Zr2O12 for solid-state lithium metal batteries enabled by W and Ta co-doping strategy

Solid-state lithium metal batteries (SSLMBs) has caught research interest for its desirable safety and energy density. However, low density, poor uniformity of the solid-state electrolytes (SSEs) and dendrite penetration through the SSEs are the major problems that hinders the progress in SSLMB’s development. Herein, a co-doping strategy is proposed for garnet-type electrolyte by utilizing a well-designed lithium-rich additive Li 2 WO 4 (LWO) doping into Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT). LWO addition yields a denser and more uniform material by acting as a sintering aid and providing inner Li 2 O atmosphere. W substitutes the Zr element and form Ta, W-doped LLZO and second phase, which broadens the sintering temperature range of LLZT and avoids abnormal grain growth (AGG). With 2 wt% LWO, LLZT-2LWO has ionic conductivity of 0.6 mS cm -1 and relative density of 98.67%. Moreover, the critical current density (CCD) of LLZT-2LWO reaches 1.0 mA cm −2 . LLZT-2LWO achieves long cycling stability for 300 h at 0.5 mA cm −2 , showing an excellent dendrite-suppression capability. The full cell matched with LiNi 0.6 Co 0.2 Mn 0.2 O 2 and Sulfur cathode display high discharge capacity and cycling stability. This modification strategy has high efficiency, and is conducive to large-scale production, which opens a new opportunity for SSLMBs. • Li 2 WO 4 is a novel additive for high-quality LLZT with pressureless sintering. • W and Ta co-doping strategy broadens sintering temperature range. • Enhanced Li dendrite-suppression ability benefits from strong grain-to-grain bonding. • Full batteries exhibit excellent rate performance and cycling stability.