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The emerging internet of things requires autonomous and ubiquitous on-chip devices with wireless interconnectivity. On-chip power is required to meet the miniaturization requirement, and an integrated on-chip micro-supercapacitor has enormous potential to meet this requirement owing to its high-power density and long cycle life. However, the two-dimensional expansion of the current co-planer design paradigm of micro-supercapacitors, such as the interdigital layout, hinders the on-chip integration density, resulting in a significant consumption of precious chip footprint and an insufficient energy density. This article reports on the use of a three-dimensional framework along with a hybrid printing strategy to fabricate devices entirely without any post-processing, and highly integrated three-dimensional micro-supercapacitors were printed as proof of concept. The micro-supercapacitors exhibit more than 25 times areal capacitance than the interdigital ones (76 mF/cm2 vs 2.9 mF/cm2) due to their three-dimensional feature. Moreover, it can provide new functions to achieve adjustable voltage and capacitance flexibility within one device's footprint area. This approach can also enable devices on different substrates. An ultraviolet sensor was integrated with and powered by the three-dimensional micro-supercapacitors on polyimide to demonstrate the compact on-chip application. The three-dimensional framework offers a general solution to the on-chip integration challenges of micro-supercapacitors. Moreover, it can be extended to new materials or even other electronics units, highlighting the promise of further miniaturized and powerful micro-electronics.

The electrochemical-mechanical coupling property of solid electrolyte membranes is critical to improving the performance of solid-state energy storage devices. A new phenomenon was observed in which the electrochemical charge-discharge process induced aligned wrinkles on the edge of poly(vinyl alcohol)-HSO gel polymer electrolytes (GPEs), which is attributed to the deformation of polymer chains under electrochemical stimulation according to multiscale simulations. In the reverse direction, by means of modeling and testing, it was proved that the ionic conductivity of GPEs can be tuned by mediating the mechanical properties of GPEs via tailoring the polymer at the nanoscale. This bidirectional correlation reveals the coupling mechanisms between mechanical and electrochemical properties of GPEs and provides an insightful understanding of the origin and regulation of the ionic conductivity of GPEs, which is fundamental to improving the performance of GPEs.

Carbon-based materials have been widely used in energy storage and conversion devices. Among them, graphene oxide (GO) holds much promise for supercapacitor applications due to its high-capacitance, low-cost, etc. Nevertheless, intrinsic characteristics related to the capacitive properties of GO are far from being fully understood. Little attention has been paid to the size effect of raw graphite on the electrochemical characteristics of GO. In order to investigate the relationship between raw graphite size and the capacitive properties of GO, electrochemical performances of GO, prepared from raw graphite of three different sizes using a modified Hummer's method, were compared. Experimental results indicated that the capacitance of a GO electrode was enhanced with the increasing size of the raw graphite. The GO electrode prepared with the largest size of raw graphite achieved a specific capacitance as high as 94.4 F g À1 at 0.1 A g À1 due to a medium-sized specific surface area and smaller charge transfer resistance. It is concluded that more attention should be paid to the prevention of agglomeration or even restacking of the graphene-based material after the heat drying of graphenebased solutions because of residual intercalated water molecules, which contribute to strong hydrogen bonding interactions between layers.