a conventional battery, such as good electrochemical performance, affordable price, and high safety.A conventional full cell LIB is a complicated device, composed of a current collector, a cathode, an anode, a separator, an electrolyte, and a proper packaging. To fabricate a stretchable full cell, we need to replace all these components with materials that can provide simultaneously the appropriate electrochemical functionalities as well as the intrinsic mechanical stretchability. Many components that could potentially be used in a stretchable battery have been presented in the literature. For example, several approaches have been reported for fabricating stretchable electrodes by incorporating rigid electrode materials within a porous framework, with a wavy design, or with helically coiled spring configuration. [6] However, these structures are usually complicated and costly to produce and scale-up, and, due to the use of polydimethylsiloxane (PDMS) or other substrates, the cells are thick and heavy. [7] Also, stretchable composite conductors for applications in electronics have been widely investigated. [8] However, there are only very few reports targeting battery current collectors. [7,9] The sheet resistances of the reported materials range from around 150 to 200 Ω □ −1 in the unstretched states and get much higher when stretched, producing significant internal resistance. Polymer gel electrolytes (PGEs) composed of poly(vinylidene fluoride) (PVDF), [10] poly(ethylene glycol) (PEG), [11] poly(ethylene oxide) (PEO), [12] or poly(ionic liquid) [13] are widely accepted as promising solution for flexible LIBs due to their advantageous flexibility, safety, and packaging behavior compared to the liquid electrolytes with a porous separator. Unfortunately, PGEs usually show quite a low room temperature ionic conductivity that ranges from 10 −4 to 10 −3 S cm −1 . Since 2015, "water-in-salt" (WiS) aqueous electrolytes containing extremely concentrated lithium salt have been investigated. [14] Some of these WiS-based gel electrolytes have also been reported to show better safety and robustness compared with the conventional PGE. [15] However, none of these materials exhibited mechanical stretchability.It is interesting to note that although so many stretchable battery components have been reported, their processing into full cells is rarely described, and even in these cases, usually not all the LIB components were made stretchable. [7,16] The reason for this is the diffculty in obtaining robust conductive interfaces between the battery components enabling efficient ion and A solid-state lithium-ion battery, in which all components (current collector, anode and cathode, electrolyte, and packaging) are stretchable, is introduced, giving rise to a battery design with mechanical properties that are compliant with flexible electronic devices and elastic wearable systems. By depositing Ag microflakes as a conductive layer on a stretchable carbon-polymer composite, a current collector with a low sheet resistance of ≈2.7 Ω ...