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High performance flexible batteries are essential ingredients for flexible devices. However, general isolated flexible batteries face critical challenges in developing multifunctional embodied energy systems, owing to the lack of integrative design. Herein, inspired by scales in creatures, overlapping flexible lithium‐ion batteries (FLIBs) consisting of energy storage scales and connections using LiNi0.5Co0.2Mn0.3O2 (NCM523) and graphite electrodes are presented. The scale‐dermis structure ensures a high energy density of 374.4 Wh L−1 as well as a high capacity retention of 93.2% after 200 charge/discharge cycles and 40 000 bending times. A variable stiffness property is revealed that can be controlled by battery configurations and deformation modes. Furthermore, the overlapping FLIBs can be housed directly into the architecture of several flexible devices, such as robots and grippers, allowing to create multifunctionalities that go far beyond energy storage and include load‐bearing and variable flexibility. This study broadens the versatility of FLIBs toward energy storage structure engineering of flexible devices.

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The large volume change of Si has been a roadblock in deploying high-capacity Si-based electrodes in lithium-ion batteries, causing salient structural changes and prominent chemo-mechanical coupled degradation. However, the effects of the volume change of Si-based active materials on the structural parameters have not been fully understood, especially for theoretical prediction through fundamental parameters. In this work, we develop a real-time porosity model featuring volume changes of active materials and electrode dimensions for Si-based anodes, predicting the evolution of porosity and electrode dimensions well through the use of basic electrode parameters. The allowable design space of mass fractions of Si is predicted to be lower than 6% for initial porosity in the range of 26–60% based on the permitted limits of maximum volume change of electrode dimensions and minimum porosity at full lithiation. Subsequently, the effects of changes in porosity and electrode dimensions on the gravimetric and volumetric capacities are emphasized, showing that the accurate estimation of electrochemical performance calls more attention to the effects of structural parameters for Si-based anodes. This study provides a simple and practicable method for the design of electrode parameters, and sheds light on the estimation of electrochemical performance for Si-based anodes.