Win-Win on both ion-conducting and mechanical properties achieved in PEO-based solid electrolytes through microstructure regulation

Abstract

Solid state electrolytes are of great importance in the design of all-solid-state lithium metal batteries (ASLMBs) that with excellent properties and glorious working stability. And solid polymer electrolytes (SPEs) are the attention-getting candidate, because of its flexibility lightweight and suitable ionic transportation ability. However, current SPEs always need balance between ionic conductivity (σ) and the mechanical strength. To this end, organic-inorganic composite solid-state electrolytes (CSEs) are designed by introduction of BN nanosheets into the polymer matrix, coupled with using the electrospinning technique. It is proved show that the PEO crystallinity in the fibrous electrolyte is significantly suppressed, with only 1 wt% BN adding. And the σ of the designed sample is raised to 1.93×10−4 S∙cm−1 at 40 ℃, on account of that the BN layered structure and three-dimensional fibrous framework help to provide dual channels for Li+ transport. Also better interfacial miscibility with Li metal is realized in the obtained fibrous CPEs and the Galvanostatic cycling of the symmetric Li//Li cell sustains as long as 850 h with 0.1 mA·cm−2 current density. Compared with the solution-casted sample with the same composition, the tensile strength (0.88 MPa) and electrochemical stability of the electrospun membrane (5.1 V) are both significantly enhanced. In addition, the obtained LiFePO4|PEO/LiClO4/BN CSE|Li all solid state coin cells exhibit excellent cycling and rate performances. The initial discharge specific capacity reaches to 144.1 mAhg−1. And coin cells cycled at 1 C current and at 80℃ give a capacity retention ratio of 81.1% after 200 cycles. It demonstrates that thin and flexible CSEs with excellent electrochemical performance can be accomplished through electrospining technique.