浓度梯度PEO-LLZTO-LATP固态电解质的制备及性能研究

Preparation and Properties of Concentration Gradient PEO-LLZTO-LATP Solid Electrolyte

复合固态电解质因其兼具一定的柔性与机械强度,能够发挥无机固态电解质与有机固态电解质各自的优点使得整体性能得到提升,且可以通过调节各组分的比例使其具备不同的性能。然而,仅靠调节各组分的比例得到的浓度单一的复合固态电解质难以同时满足复合电解质对于负极|电解质与正极|电解质界面的不同需求。因此,为克服单一浓度复合固态电解质存在的局限性,本文通过简单的堆叠与热压工艺,合成得到了无机填料具有浓度梯度分布的PEO-LLZTO-LATP复合固态电解质(GCSE-20LLZTO-50-70LATP),使复合电解质两侧具备不同的电化学性能以分别满足与负极和正极的不同界面需求。梯度结构的设计使复合电解质实现了低无机填料含量的负极侧与Li金属良好的界面接触以及较高的离子电导率(1.01 × 10−4 S∙cm−1),LLZTO在负极侧的采用确保了与Li负极良好的化学相容性,同时高无机填料含量的正极侧提供了良好的枝晶抑制能力,采用电化学稳定性相对更高的LATP作为正极侧的无机填料进一步有效地提升了复合电解质的电化学窗口(5.0 V vs. Li/Li )。GCSE-20LLZTO-50-70LATP能够在0.1 mA·cm−2和50℃下稳定锂剥/镀循环超过1900 h。组装的Li|GCSE-20LLZTO-50-70LATP|LFP全电池在0.1 C电流密度下的放电比容量为157.3 mAh∙g−1,进行70次循环后容量保持率为90.1%。

The composite solid electrolyte has a certain flexibility and mechanical strength at the same time, which can play the respective advantages of inorganic solid electrolyte and organic solid electrolyte to improve the overall performance, and can have different performance by adjusting the proportion of each component. However, the single concentration of composite solid electrolyte obtained by adjusting the proportion of each component cannot meet the different requirements of composite electrolyte for the interface between cathode | electrolyte and anode | electrolyte at the same time. Therefore, in order to overcome the limitations of single concentration composite solid electrolyte, PEO-LLZTO-LATP composite solid electrolyte (GCSE-20LLZTO-50-70LATP) with concentration gradient distribution of inorganic filler was synthesized by simple stacking and hot pressing process, so that the two sides of the composite electrolyte can have different electrochemical properties to meet the different interface requirements with cathode and anode respectively. The gradient structure design enables the composite electrolyte to achieve good interface contact with Li metal at the anode side with low inorganic filler content and high ionic conductivity (1.01 × 10−4 S∙cm−1). The use of LLZTO at the anode side of the electrolyte ensures good chemical compatibility with the Li anode. While the cathode side of the electrolyte with high inorganic filler content provides good dendrite inhibition ability. Using LATP as the inorganic filler at the cathode side with relatively higher electrochemical stability further effectively improves the electrochemical window of the composite electrolyte (5.0 V vs. Li/Li ). GCSE-20LLZTO-50-70LATP can stabilize the lithium stripping/plating cycle for more than 1900 h at 0.1 mA∙cm−2 and 50˚C. The specific discharge capacity of Li|GCSE-20LLZTO-50-70LATP|LFP battery at 0.1 C current density was 157.3 mAh·g−1, and the capacity retention rate was 90.1% after 70 cycles.