Inkjet-printable inks for electrochemical energy devices: A review of materials, formulation, and functional-layer engineering

The fabrication of electrochemical energy devices is no longer concerned solely with material functionality, but increasingly with how precisely and flexibly these materials can be patterned and integrated. This trend places higher demands on pattern resolution, structural complexity, multi-material integration, and processing flexibility during device fabrication, while traditional manufacturing methods still suffer from certain limitations in on-demand deposition, fine patterning, and compatibility with complex substrates. To address these challenges, inkjet printing, with its advantages of digitalization, non-contact operation, programmability, and high material utilization, has gradually emerged as a highly promising manufacturing route for electrochemical energy devices. However, the effectiveness of inkjet printing depends not only on the printing equipment itself, but also to a large extent on whether ink formulation and printing behavior can be coordinated with the structural, transport, and processing requirements of different functional layers, so that stable printability can be translated into controllable deposited structures and electrochemical performance. On this basis, this paper presents a review of ink materials for inkjet printing in electrochemical energy devices. First, the basic process of inkjet printing and the fundamental requirements for ink parameters and composition are introduced, with an overview of the effects of physicochemical and rheological properties on ink printability. Subsequently, the material composition, formulation strategies, film-formation characteristics, and application progress of different inkjet ink systems in electrochemical energy devices are systematically summarized, and the intrinsic relationships among ink formulation, droplet evolution, deposition behavior, and device performance are analyzed. Furthermore, cross-system design principles are extracted to guide ink selection and formulation according to the functional-layer, substrate, and processing requirements of electrochemical energy devices. Finally, the major challenges currently faced by inkjet-printed electrochemical inks, including ink stability, printing reliability, deposition efficiency, sustainability, and scalable manufacturing are discussed, and future development directions are proposed.