NOVELTY - The device (101) has first and second electrically conductive electrodes (110, 120) comprising channels (111, 121) that contain first and second polymer electrolytes (150) and first and second surfaces (115, 125), where one of the electrodes is a porous silicon electrode. One of the surfaces comprises an electrically conductive passivating layer with bonds provided between silicon and metal. A hydrogen-terminated surface of the electrode is passivated by using hydrosilylation. One of the electrolytes is deposited into the channels of the electrode.    USE - Electrochemical capacitive energy storage device e.g. solid-electrode battery, capacitor such as electrochemical capacitor (EC) e.g. pseudocapacitor, electric double-layer capacitor (EDLC) and hybrid EC, for use in a mobile electronic device (claimed) e.g. personal computer (PC), laptop computer, notebook computer, tablet computer, cell phone, smart phone, music player and mobile internet device. Can also be used for a desktop computer, server, transportation vehicle e.g. automobile, bus, train and airplane, and an energy harvesting device.    ADVANTAGE - The device allows a separator to prevent electrically conductive structures from physically contacting each other, thus preventing electrical short circuit. The device facilitates hydrogen desorption issue by electrochemically treating the surface to remove the hydrogen and passivate the surface with the passivating layer, thus protecting the surface, improving energy storage device's effective series resistance (ESR) and enabling formation of a robust and stable device. The device allows an electrically conductive coating on a portion of the porous structure and some of channels, thus maintaining conductivity of the porous structure, which can lower the ESR, thus improving performance of the device.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a method for manufacturing an energy storage device    (2) a mobile electronic device.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of an energy storage structure.    Energy storage structure (100)    Electrochemical capacitive energy storage device (101)    Electrically conductive support structure (102)    Conductive electrodes (110, 120)    Channels (111, 121)    Openings (112, 122)    Surfaces of electrodes (115, 125)    Separator (130)    Electrically conductive coating (140)    Electrolytes (150)