Li Libo, Shan Yuhang, Wang Furi, Chen Xiaochuan, Zhao Yangmingyue, Zhou Da, Wang Heng, Cui Wenjun
School of Materials Science and Chemical Engineering, Harbin University of Science and Technology, Harbin 150040, China.
ACS Appl Mater Interfaces. 2021 Oct 20;13(41):48525-48535. doi: 10.1021/acsami.1c11489. Epub 2021 Oct 8.
Solid-state lithium batteries using solid polymer electrolytes can improve the safety and energy density of batteries. Smoother lithium-ion channels are necessary for solid polymer electrolytes with high ionic conductivity. The porosity and channel structure of the polymer film affect the transfer of lithium ions. However, their controllable synthesis remains a big challenge. Here, we developed a simple synthesis approach toward wrinkled microporous polymer electrolytes by combining the amphoteric (water solubility and organic solubility) polymer in three polymer blends. The homogeneous blend solution spontaneously wrinkled to vertical fold channels as the solvent evaporated. Two minor polymers, poly(vinyl pyrrolidone) (PVP) and polyetherimide (PEI), formed close stacks, and Janus PVP was dispersed in the poly(vinylidene fluoride) (PVDF) matrix. The interfacial tensions between the three polymers were different, so stress was produced when they solidified. The solvent was evaporated to the top layer of the polymers when the temperature increased. The bottom layer wrinkled owing to the stress during solidification. The evaporation of the solvent generated micropores to form the lithium-ion channel. They helped Li transference and created a wrinkled microporous PVDF-based polymer electrolyte, which achieved an ionic conductivity of 5.1 × 10 S cm and a lithium-ion transference number of 0.51 at room temperature. Meanwhile, the good flame retardancy and tensile strength of the polymer electrolyte film can improve the safety of the battery. At 0.5C and room temperature, the batteries with a LiFePO cathode and the wrinkled microporous LiTFSI/PEI/PVP/PVDF electrolyte reached a high discharge specific capacity of 122.1 mAh g at the 100th cycle with a Coulombic efficiency of above 99%. The results of tensile and self-extinguishing tests show that the polymer electrolyte film has good safety application prospects.
使用固体聚合物电解质的固态锂电池可以提高电池的安全性和能量密度。对于具有高离子电导率的固体聚合物电解质来说，更平滑的锂离子通道是必要的。聚合物膜的孔隙率和通道结构会影响锂离子的传输。然而，它们的可控合成仍然是一个巨大的挑战。在此，我们通过在三种聚合物共混物中结合两性（水溶性和有机溶性）聚合物，开发了一种制备皱纹状微孔聚合物电解质的简单合成方法。随着溶剂蒸发，均匀的共混溶液自发地形成垂直褶皱通道。两种次要聚合物，聚乙烯吡咯烷酮（PVP）和聚醚酰亚胺（PEI），形成紧密堆积，而两性离子PVP分散在聚偏氟乙烯（PVDF）基体中。三种聚合物之间的界面张力不同，因此固化时会产生应力。温度升高时，溶剂蒸发到聚合物的顶层。底层由于固化过程中的应力而产生皱纹。溶剂的蒸发产生微孔以形成锂离子通道。它们有助于锂离子传输，并制备出一种皱纹状微孔PVDF基聚合物电解质，其在室温下的离子电导率为5.1×10 S cm，锂离子迁移数为0.51。同时，聚合物电解质膜良好的阻燃性和拉伸强度可以提高电池的安全性。在0.5C和室温下，采用LiFePO正极和皱纹状微孔LiTFSI / PEI / PVP / PVDF电解质的电池在第100次循环时达到了122.1 mAh g的高放电比容量，库仑效率高于99%。拉伸和自熄测试结果表明，该聚合物电解质膜具有良好的安全应用前景。
