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

Abstract

Solid-state lithium metal batteries (SSLMBs) have caught research interest for their 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 hinder 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 Li2WO4 (LWO) doping into Li6·5La3Zr1·5Ta0·5O12 (LLZT). LWO addition yields a denser and more uniform material by acting as a sintering aid and providing an inner Li2O atmosphere. W substitutes the Zr element and forms Ta and 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 an ionic conductivity of 0.6 mS/cm and a 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 LiNi0·6Co0·2Mn0·2O2 and sulfur cathode displays 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.