Solid polymer electrolyte coating from a bifunctional monomer for three-dimensional microbattery applications

• A novel bifunctional monomer is synthesized.
• A cross-linked polymer electrolyte is produced from the monomer.
• The electrolyte shows functionality for Li-ion 3D-microbatteries.
• The material is electrochemically characterized.
• Functionality in Li-cells is demonstrated.

This work comprises the synthesis and characterization of a novel solid polymer electrolyte based on oligomeric polyetheramine substituted with a methacrylic group at one of its three chain ends. This modification introduces a bifunctionality to the PEA monomer – it can act both as polymerizable unit and surfactant. Thin and pinhole-free polymer electrolyte layers could be constructed with thicknesses in the order of <1 μm using UV-initiated polymerization. The electrolyte exhibits good electrochemical and chemical stability up to 4 V vs. Li+/Li. LiFePO4 cathode coated with the electrolyte was cycled against lithium at 60 °C, and displayed reasonable capacity values (∼140 mAh g−1) for 10 cycles, where after Li dendrite formation contributed to battery instabilities.