Yang Ke, Ma Jiabin, Li Yuhang, Jiao Junyu, Jiao Shizhe, An Xufei, Zhong Guiming, Chen Likun, Jiang Yuyuan, Liu Yang, Zhang Danfeng, Mi Jinshuo, Biao Jie, Li Boyu, Cheng Xing, Guo Shaoke, Ma Yuetao, Hu Wei, Wu Shichao, Zheng Jiaxin, Liu Ming, He Yan-Bing, Kang Feiyu
Shenzhen All-Solid-State Lithium Battery Electrolyte Engineering Research Center, Institute of Materials Research (IMR), Tsinghua Shenzhen International Graduate School, Shenzhen 518055, China.
School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
J Am Chem Soc. 2024 Apr 1. doi: 10.1021/jacs.4c00976.
Poly(vinylidene fluoride) (PVDF)-based solid electrolytes with a Li salt-polymer-little residual solvent configuration are promising candidates for solid-state batteries. Herein, we clarify the microstructure of PVDF-based composite electrolyte at the atomic level and demonstrate that the Li-interaction environment determines both interfacial stability and ion-transport capability. The polymer works as a "solid diluent" and the filler realizes a uniform solvent distribution. We propose a universal strategy of constructing a weak-interaction environment by replacing the conventional ,-dimethylformamide (DMF) solvent with the designed 2,2,2-trifluoroacetamide (TFA). The lower Li binding energy of TFA forms abundant aggregates to generate inorganic-rich interphases for interfacial compatibility. The weaker interactions of TFA with PVDF and filler achieve high ionic conductivity (7.0 × 10 S cm) of the electrolyte. The solid-state Li||LiNiCoMnO cells stably cycle 4900 and 3000 times with cutoff voltages of 4.3 and 4.5 V, respectively, as well as deliver superior stability at -20 to 45 °C and a high energy density of 300 Wh kg in pouch cells.
具有锂盐-聚合物-少量残留溶剂结构的聚偏氟乙烯（PVDF）基固体电解质是固态电池的有前途的候选材料。在此，我们在原子水平上阐明了PVDF基复合电解质的微观结构，并证明锂相互作用环境决定了界面稳定性和离子传输能力。聚合物起到“固体稀释剂”的作用，填料实现了溶剂的均匀分布。我们提出了一种通用策略，即通过用设计的2,2,2-三氟乙酰胺（TFA）取代传统的N,N-二甲基甲酰胺（DMF）溶剂来构建弱相互作用环境。TFA较低的锂结合能形成大量聚集体，以产生富含无机成分的界面相以实现界面相容性。TFA与PVDF和填料之间较弱的相互作用使电解质具有高离子电导率（7.0×10⁻⁴ S cm⁻¹）。固态锂||LiNiCoMnO₂电池在截止电压分别为4.3 V和4.5 V时稳定循环4900次和3000次，并且在-20至45°C下具有优异的稳定性，在软包电池中具有300 Wh kg⁻¹的高能量密度。
