Despite their potential advantages over currently widespread lithium‐ion batteries, lithium–sulfur (Li–S) batteries are not yet in practical use. Here, for the first time bipolar all‐solid‐state Li–S batteries (ASSLSBs) are demonstrated that exhibit exceptional safety, flexibility, and aesthetics. The bipolar ASSLSBs are fabricated through a solvent‐drying‐free, ultraviolet curing‐assisted stepwise printing process at ambient conditions, without (high‐temperature/high‐pressure) sintering steps that are required for inorganic electrolyte‐based all‐solid‐state batteries. Two thermodynamically immiscible and nonflammable gel electrolytes based on ethyl methyl sulfone (EMS) and tetraethylene glycol dimethyl ether (TEGDME) are used to address longstanding concerns regarding the grain boundary resistance of conventional inorganic solid electrolytes, as well as the polysulfide shuttle effect in Li–S batteries. The EMS gel electrolytes embedded in the sulfur cathodes facilitate sulfur utilization, while the TEGDME gel composite electrolytes serve as polysulfide‐repelling separator membranes. Benefiting from the well‐designed cell components and printing‐driven facile processability, the resulting bipolar ASSLSBs exhibit unforeseen advancements in bipolar cell configuration, safety, foldability, and form factors, which lie far beyond those achievable with conventional Li–S battery technologies.

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The forthcoming smart and ubiquitous electronics era presents significant interest in wireless interconnectivity and shape aesthetics. To fulfill this demand, a new class of advanced power sources with various form factors that are different from existing commercial ones is needed. Printed power sources have recently garnered substantial attention because of their design diversity, shape and performance compatibility with electronics, and scalable and low-cost processability. They are fabricated directly on complex-structured objects via application-customized printing techniques, enabling monolithic integration and electrochemical coupling with target devices. In this Perspective, we describe the current status and challenges of printed power sources, focusing on their role as built-in power sources. Various printing techniques and ink materials and chemistry of electrodes and electrolytes are discussed as key enabling factors. Noteworthy progress in printed built-in power sources is reviewed to highlight their design diversity and electrochemical superiority. Finally, development direction and outlook of printed built-in power sources are discussed in conjunction with their application fields.