Miniaturized energy-storage components are important to self-powered microelectronics. Microbatteries based on 3D electrode architectures hold great potential to meet the demands of high-power and high energy densities. Despite the progress in microelectrode fabrication, reports of high-performance, fully integrated 3D microbatteries are still limited due to strict material requirements and more importantly, significant hierarchical processing complexities. Here, a 3D lithium-ion microbattery made from solvothermally synthesized sub-10 nm LiMn2O4/Li4Ti5O12 nanocrystals and a novel copolymer gel electrolyte is presented and is shown to possess superior capacity retention (40% at 300 C) and high-power density (855.5 μ Wcm−2 μ m−1 ) comparable to some of the best microsupercapacitors. The customized microelectrodes are fabricated by solvent-assisted imprint lithography of well-dispersed nanoparticle ink and the battery cell is integrated vertically through layer-by-layer (LBL) assembly. The fabrication strategy proposed here can be applied to a variety of electroactive materials. This work provides a combinatorial approach and highlights the synergetic effects of material synthesis, processing and device design for achieving high-performance micropower sources.