Nanocomposite polymer electrolytes for solid‐state lithium‐ion batteries with enhanced electrochemical properties

Solid‐state polymer electrolytes (SPEs) have attracted significant attention owing to their improvement in high energy density and high safety performance. However, the low lithium‐ion conductivity of SPEs at room temperature restricts their further application in lithium‐ion batteries (LIBs). Herein, we propose a novel poly (ethylene oxide) (PEO)‐based nanocomposite polymer electrolytes by blending boron‐containing nanoparticles (BNs) in the PEO matrix (abbreviated as: PEO/BNs NPEs). The boron atom of BNs is sp2‐hybridized and contains an empty p‐orbital that can interact with the anion of lithium salt, promoting the dissociation of the lithium salts. In addition, the introduction of the BNs could reduce the crystallinity of PEO. And thus, the ionic conductivity of PEO/BNs NPEs could reach as high as 1.19 × 10−3 S cm−1 at 60°C. Compared to the pure PEO solid polymer electrolyte (PEO SPEs), the PEO/BNs NPEs showed a wider electrochemical window (5.5 V) and larger lithium‐ion migration number (0.43). In addition, the cells assembled with PEO/BNs NPEs exhibited good cycle performance with an initial discharge capacity of 142.5 mA h g−1 and capacity retention of 87.7% after 200 cycles at 2 C (60°C). A nanocomposite polymer electrolyte with PEO as the matrix, BNs as the functional fillers was prepared by solution casting method, which has excellent ionic conductivity and battery performance, showing application potential in lithium ion batteries.