Recent advances in solving Li_(2)CO_(3) problems in garnet-based solid-state battery: A systematic review(2020-2023)

Garnet solid electrolytes are one of the most promising electrolytes for solid-state batteries.However,Li_(2)CO_(3) is a critical issue that hinders the practical application of garnet-based solid-state lithium-ion batteries.There are two sources of Li_(2)CO_(3) contamination.The main one is the aging of garnet electrolytes in the atmosphere.Garnet electrolytes can react with H_(2)O and CO_(2) in the air to form Li_(2)CO_(3),which reduces ion conductivity,increases electrode/garnet electrolyte interface resistance,and deteriorates the electrochemical performance of the battery.Various strategies,such as elemental doping,grain boundary manipulation,and interface engineering,have been suggested to address these issues.The other is the passivation layer(Li_(2)CO_(3),Li_3N,LiOH,Li_(2)O) formed on the surface of the lithium foil after long-term storage,which is ignored by most researchers.To better understand the current strategies and future trends to address the Li_(2)CO_(3) problem,this perspective provides a systematic review of journals published in this field from 2020-2023.

Fast ion-conducting high-entropy garnet solid-state electrolytes with excellent air stability

The garnet-type electrolyte is one of the most promising solid-state electrolytes(SSEs)due to its high ionic conductivity(σ)and wide electrochemical window.However,such electrolyte generates lithium carbonate(Li_(2)CO_(3))in air,leading to an increase in impedance,which greatly limits their practical applications.In turn,high-entropy ceramics(HECs)can improve phase stability due to high-entropy effect.Herein,high-entropy garnet(HEG)Li_(6.2)La_(3)(Zr_(0.2)Hf_(0.2)Ti_(0.2)Nb_(0.2)Ta_(0.2))_(2)O_(12)(LL(ZrHfTiNbTa)O)SSEs were synthesized by the solid-state reaction method.X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),electrochemical impedance spectroscopy(EIS),and scanning electron microscopy(SEM)characterizations indicated that the LL(ZrHfTiNbTa)O electrolyte has excellent air stability.Room-temperature conductivity of LL(ZrHfTiNbTa)O can be maintained at~1.42×10^(-4)S/cm after exposure to air for 2 months.Single-element-doped garnets were synthesized to explain the role of different elements and the mechanism of air stabilization.In addition,a lithium(Li)/LL(ZrHfTiNbTa)O/Li symmetric cell cycle is stable over 600 h,and the critical current density(CCD)is 1.24 mA/cm^(2),indicating remarkable stability of the Li/LL(ZrHfTiNbTa)O interface.Moreover,the LiFePO_(4)/LL(ZrHfTiNbTa)O/Li cell shows excellent rate performance at 30℃.These results suggest that HECs can be one of the strategies for improving the performance of SSEs in the future due to their unique effects.