Ta、Ba共掺杂石榴石型Li7La3Zr2O12电解质的制备及性能研究

传统锂离子电池采用有机电解液体系,能量密度难以进一步提升,同时存在一定的安全隐患。采用无机固体电解质构建全固态锂电池,在提高电池能量密度同时可兼顾安全性问题。在众多无机固体电解质中,Li₇La₃Zr₂O₁₂(LLZO)石榴石电解质具有离子电导率高、与金属锂接触稳定等优势,成为受人关注的材料。为了进一步提高该材料的导电性,采用固相法合成Ta、Ba共掺杂LLZO(Li_7-x+yLa_3-yBa_yZr_2-xTa_xO₁₂)电解质,采用X射线衍射、扫描电子显微镜和电化学阻抗法分析样品的物相结构、微观形貌及离子电导率。结果表明,Ta⁵⁺掺杂能够稳定立方相结构,Ba²⁺作为掺杂剂和烧结剂,促进晶粒生长和陶瓷致密化,从而降低总电阻。其中,Li_6.45La_2.95Ba_0.05Zr_1.4Ta_0.6O₁₂样品在室温下的总电导率为1.07×10^-3 S·cm^-1,活化能为0.378 eV。Ta⁵⁺/Ba²⁺共掺杂有利于制备高致密度和高电导率的石榴石型电解质材料。

Preparation and Properties of Ta,Ba Co-Doped Garnet-Type Li7La3Zr2O12 Electrolyte

Conventional lithium-ion batteries using organic liquid electrolytes suffer from limited energy density and safety risks. To improve energy density and safety, all-solid-state lithium battery are developed using solid electrolytes. Among various inorganic solid-state electrolytes, the garnet-type Li₇La₃Zr₂O₁₂ electrolytes have attracted a great deal of attention, owing to high ionic conductivity and the excellent stability against Li metal. In order to further improve the conductivity, the garnet-type electrolytes Ta and Ba co-doped Li₇La₃Zr₂O₁₂ (Li_7-x+yLa_3-yBa_yZr_2-xTa_xO₁₂) were prepared using solid-state synthesis method. The crystal structure, morphology and ionic conductivity of Li_7-x+yLa_3-yBa_yZr_2-xTa_xO₁₂ (0.4≤x≤0.6, 0≤y≤0.05) electrolytes were systematically investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS), respectively. The results show that Ta⁵⁺ doping stabilizes the cubic phase. Meanwhile, Ba²⁺ as dopand and sintering agent can decrease the total resistance by promoting the growth of grains and ceramic densification. Notably, the Li_6.45La_2.95Ba_0.05Zr_1.4Ta_0.6O₁₂ sample presents a total conductivity of 1.07×10^-3 S·cm^-1 at room temperature and an activation energy of 0.378 eV. Ta⁵⁺/Ba²⁺ co-doping strategy is conducive to the preparation of garnet-type electrolyte materials with high density and high conductivity.