共混过渡层对非对称填料复合固态电解质的优化及其性能研究

Optimization and Performance Study of Asymmetric Filler Composite Solid Electrolytes via a Blended Transition Layer

摘要: 针对传统复合固态电解质界面阻抗大、力学性能与界面相容性平衡困难以及抑制锂枝晶能力不足等瓶颈问题，本文提出并构筑了一种具有非对称填料设计的复合固态电解质(T-AFCSE)。该体系以柔韧性更佳的聚偏氟乙烯–六氟丙烯(PVDF-HFP)和聚氧化乙烯(PEO)作为复合聚合物基体，针对正负极不同的界面需求，在负极侧引入PEO/LATP体系以优化界面传导与润湿性，在正极侧采用HFP/LLZTO体系以增强机械强度与抗氧化稳定性。特别地，本文通过构筑一层PVDF-HFP/PEO共混过渡层，结合冷等静压与热压工艺成功消除了异质电解质间的物理界面，实现了分子链段的物理缠结与电化学势的平缓过渡。实验结果表明，T-AFCSE在50℃下的离子电导率高达3.11 × 10⁻⁴ S/cm，显著优于单一填料层及无过渡层的双层结构，同时将电化学稳定窗口扩展至5.1 V。在循环性能方面，组装的锂对称电池在0.1 mA/cm²电流密度下能够平稳循环超过2000小时且无短路迹象，展现出极强的抑制锂枝晶穿透能力。此外，组装的Li|T-AFCSE|LFP电池在50℃、0.1 C倍率下循环100圈后，放电比容量仍维持在136 mAh/g，容量保持率达82%。

Abstract: To address the bottlenecks of conventional composite solid electrolytes, such as high interfacial resistance, the trade-off between mechanical strength and interfacial compatibility, and poor lithium dendrite suppression, this paper proposes and constructs a composite solid electrolyte with an asymmetric filler design (T-AFCSE). Using the highly flexible poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(ethylene oxide) (PEO) as the blended polymer matrix, the system is functionally customized for different electrode interfaces: the PEO/LATP system is introduced on the anode side to optimize interfacial conduction and wetting, while the PHFP/LLZTO system is employed on the cathode side to enhance mechanical strength and antioxidant stability. Specifically, a PVDF-HFP/PEO blended transition layer was designed and combined with cold isostatic pressing and hot pressing processes to successfully eliminate the rigid physical interface between the heterogeneous electrolytes, achieving molecular chain entanglement and smooth electrochemical potential transition. Experimental results demonstrate that the T-AFCSE exhibits a high ionic conductivity of 3.11 × 10⁻⁴ S/cm at 50˚C, significantly outperforming single-filler layers and dual-layer structures without a transition layer, while extending the electrochemical stability window to 5.1 V. Regarding cycling performance, the assembled Li symmetric cells can cycle stably for over 2000 hours at a current density of 0.1 mA/cm² without short-circuiting, showing excellent dendrite suppression capabilities. Furthermore, the Li|T-AFCSE|LFP battery maintains a discharge specific capacity of 136 mAh/g after 100 cycles at 50˚C and 0.1 C, with a capacity retention of 82%.