3‐D Integrated All‐Solid‐State Rechargeable Batteries

Portable society urgently calls for integrated energy supplies. This holds for autonomous devices but even more so for future medical implants. Evidently, rechargeable integrated all‐solid‐state batteries will play a key role in these fields, enabling miniaturization, preventing electrode degradation upon cycling and electrolyte leakage. Planar solid‐state thin film batteries are rapidly emerging but reveal several potential drawbacks, such as a relatively low energy density and the use of highly reactive lithium. Thin film Si‐intercalation electrodes covered with a solid‐state electrolyte are found to combine a high storage capacity of 3500 mAh g^–1 with high cycle life, enabling to integrate batteries in Si. Based on the excellent intercalation chemistry of Si, a new 3D‐integrated all‐solid‐state battery concept is proposed. High aspect ratio cavities and features, etched in silicon, will yield large surface area batteries with anticipated energy density of about 5 mWh μm^–1 cm^–2, i.e. more than 3 orders of magnitude higher than that of integrated capacitors.