Study on interface modification of LATP-based solid electrolyte membrane by PVDF

doi:10.11949/0438-1157.20241436

Abstract

Abstract:

To reduce the impedance between the Li₁₊_x Al _x Ti_2-_x (PO₄)₃ (LATP) electrolyte membrane and the lithium metal anode, suppress the side reactions between LATP and lithium metal and the growth of lithium dendrites, and improve the performance of the LATP electrolyte membrane, PVDF was used to modify the interface of LATP-based electrolyte membrane, and its electrochemical properties were studied. The LATP ceramic powder was mixed uniformly with polyethylene oxide and LIFSI and cast into a film. The PVDF solution was uniformly coated on the surface of the electrolyte membrane and dried to obtain the modified electrolyte membrane. The performance of the modified electrolyte membrane was studied by electrochemical experiments, charge-discharge experiments, and surface characterization methods. The results show that PVDF affects the crystal structure of LATP and optimizes the lithium ion migration channel. The room-temperature ionic conductivity of the modified electrolyte membrane is improved, the electrochemical window at room temperature increases from 3.74 V to 4.10 V, the lithium ion transference number increases from 0.915 to 0.978, and the cycle time of the lithium metal symmetric battery at a current density of 0.05 mA/cm² increases from 45 h to more than 280 h. The growth of lithium dendrites is effectively suppressed, and the stability of the interface between the electrolyte membrane and lithium metal is improved. The polarization voltages at current densities of 0.025, 0.050, 0.100, and 0.200 mA/cm² are 27, 60, 110 and 220 mV, respectively. A good SEI interface is formed in the LFP|SSCEs-1|Li full battery after more than 25 cycles. The capacity retention rate from the 25th cycle to the 100th cycle is 87%, and the Coulombic efficiency remains above 95%. The PVDF modification layer improves the electrochemical performance of the LATP electrolyte membrane and the stability of the interface with lithium metal, which has positive significance for the application of all-solid-state lithium batteries.

Key words: Li₁₊_x Al _x Ti_2-_x (PO₄)₃, solid-state electrolyte, interface, gels, lithium metal batteries, solid state battery

摘要：

为降低Li₁₊_x Al _x Ti_2-_x (PO₄)₃（LATP）电解质膜与锂金属负极之间的界面阻抗，抑制LATP与锂金属之间的副反应以及锂枝晶的生长，提高LATP电解质膜的性能，使用PVDF对LATP基电解质膜界面进行修饰，并研究其电化学性能。将LATP陶瓷粉末与聚氧化乙烯、LIFSI混合均匀后浇筑成膜，将PVDF溶液均匀涂覆在电解质膜表面，干燥得到修饰后的电解质膜。通过电化学实验、充放电实验、表面表征等方法，研究PVDF修饰后电解质膜的性能。结果显示，PVDF影响了LATP的晶体结构，优化了锂离子迁移通道。修饰后电解质膜的室温离子电导率提升，室温下电化学窗口由3.74 V增加到4.10 V，锂离子迁移数由0.915提升到0.978，组装锂金属对称电池在0.05 mA/cm²电流密度下的循环时间从45 h提升到280 h以上，有效抑制了锂枝晶的生长，提升了电解质膜与锂金属界面稳定性。在电流密度0.025、0.050、0.100、0.200 mA/cm²下的极化电压分别为27、60、110、220 mV。在LFP|SSCEs-1|Li全电池中循环超过25圈后形成了良好的SEI界面。从第25圈到第100圈容量保持率为87%，库仑效率始终保持在95％以上。PVDF修饰层提升了LATP电解质膜的电化学性能以及和锂金属界面的稳定性，对全固态锂电池的应用具有积极意义。

关键词: Li₁₊_x Al _x Ti_2-_x (PO₄)₃, 固态电解质, 界面, 凝胶, 锂金属电池, 固态电池

CLC Number:

TB 34

Changyu LI, Qiang ZENG, Jie XIAO, Yangjie ZHANG, zheng ZHANG, Yuanhua LIN. Study on interface modification of LATP-based solid electrolyte membrane by PVDF[J]. CIESC Journal, 2025, 76(6): 2974-2982.

李长宇, 曾强, 肖杰, 张阳杰, 张政, 林元华. PVDF对LATP基固态电解质膜界面修饰研究[J]. 化工学报, 2025, 76(6): 2974-2982.

Figures/Tables 9

Fig.1 SEM images of the SCE-0(a) and SSCEs-1(d) surfaces; SEM images of the SCE-0(b) and SSCEs-1(e) surfaces magnified locally; Cross seetion(c) and enlarged(f) SEM images of SSEs-1; (g) Element distribution map of SCE-0

Fig.2 FTIR spectra of the two electrolyte membranes

Fig.3 XRD patterns of two electrolyte membranes

Table 1 LATP cell parameters in SCE-0 and SSCEs-1

电解质膜	a/Å	b/Å	c/Å
SCE-0	8.50086	8.50086	20.81437
SSCEs-1	8.49483	8.49483	20.80561

Fig.4 Nyquist plots [(a),(b)]; and Arrhenius plots [(c),(d)] of two electrolyte membranes at different temperatures

Fig.5 LSV curves of two types of electrolyte membranes at room temperature

Fig.6 Constant potential DC polarization curve and Nyquist plot before and after polarization

Fig.8 (a) Long cycle curve of LFP|SSCEs-1|Li at 0.2C magnification; (b) Charge discharge curves of LFP|SSCEs-1|Li at different cycle numbers

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