Solid polymer electrolytes consisting of poly(propylene glycol) diacrylate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were deposited onto Cu2O-coated 3D Cu nano-pillars through cathodic electropolymerization. Electropolymerization, using constant and pulsed current techniques, was used to produce polymer coatings directly onto 3D substrates with thicknesses down to nano-scale dimensions. SEM confirmed that pulsed current deposition is comparatively beneficial for producing uniform and conformal electrolyte coatings along the nano-pillar structure. ATR/FTIR studies of the electropolymerized electrolytes showed that the degree of polymerization in the electrolyte can be increased by a heating treatment after synthesis. XPS analysis confirmed the presence of co-deposited LiTFSI salt in the polymer layer during electropolymerization. The ionic conductivity of the obtained electrolytes was characterized by EIS and is in the order of 10−6 S cm−1 at room temperature. This work demonstrates that the electrolyte coated on the nano-pillar electrodes may serve as a template for further deposition of electrode materials for the assembly of 3D-microbattery whole-cells.