The high-strength and ultra-thin composite electrolyte using one-step electrospinning/electrostatic spraying process for interface control in all-solid-state lithium metal battery

Using solid polymer electrolytes to replace liquid electrolytes is an effective strategy to improve the energy density and safety of lithium metal batteries. Herein, an ultra-thin and fast-ion-conducting composite polymer electrolyte is firstly prepared through novel one-step electrospinning/electrostatic spraying process. Different from the common solution casting method, the preparation process can ensure sufficient contact between the polymer and nanofibers, thereby effectively reducing the existence of internal defects in the electrolyte. Meanwhile, the ultra-thin thickness (∼40 μm) helps to achieve maximized interfacial contact and good compatibility, and the electrostatic spraying process can reduce the crystallinity of Polyethylene oxide (PEO) polymer under the action of electrostatic charge repulsion. Furthermore, multiple hydrogen bonding interactions can not only form a three-dimensional continuous ion conduction path at the polymer interface, but also enhance the mechanical and thermal stability of the composite electrolyte. The prepared Poly-m-phenyleneisophthalamide (PMIA)-PEO composite electrolyte exhibits superior ionic conductivity (2.9 × 10−4 S cm−1 at 30 °C), high mechanical strength (10.4 MPa) and wide electrochemical stability window (5.4 V). In particular, the composite electrolyte-based Li/Li symmetric cell and high-voltage LiNi0·8Mn0·1Co0·1O2 (NMC)/Li cell exhibit superior cycling stability, which verify the practical applicability of the all-solid-state composite electrolyte in Li metal batteries.