Dynamic lithium-compensation mechanism for densification of garnet-type Li7La3Zr2O12 electrolyte by Li2O atmosphere buffer pair

Solid-state lithium metal batteries are one of the most promising options for next-generation batteries pursuing high-energy density and high-safety. However, the inevitable volatilization of lithium compounds during sintering leads to low relative density and low ionic conductivity of solid-state electrolytes. Herein, the dynamic lithium-compensation mechanism is proposed to facilitate the densification of Ta-substituted garnet-type electrolyte (Li6.5La3Zr1.5Ta0.5O12 (LLZT)) through the reversible manipulating of Li2O atmosphere. Li2ZrO3 is used as mother powder additive, which reacts with Li2O in sintering atmosphere and forms Li6Zr2O7. Li2ZrO3/Li6Zr2O7 buffer pair manipulates the sintering Li2O atmosphere, which is vital for LLZT, within the Li2O partial pressure range corresponding to Li2ZrO3 and Li6Zr2O7. Furthermore, the reversibility mechanism of buffer pair for Li2O absorption and release is revealed. The obtained LLZT exhibits a relative density of over 96% and an ionic conductivity exceeding 7 x 10(-4) S<middle dot>cm(-1) with no abnormal grain growth. The symmetric cell demonstrates an excellent lithium dendrite suppressing ability (stable cycling at a current density of 0.3 mA<middle dot>cm(-2) for over 1000 h). Such dynamic lithium-compensation strategy has been successfully applied in atmosphere manipulation of LLZT sintering process, which reduces the dependence of LLZT on the Li2O atmosphere, making it conducive to large-scale preparation of electrolyte ceramics.