A capacity-recoverable zinc-ion micro-supercapacitor with high energy and power density is developed.

The inherently formed liquid crystals (LCs) of graphene oxide (GO) in aqueous dispersions severely restrict the fabrication of large-size and structure-intact graphene aerogel bulk by an industry-applicable method. Herein, by developing a surfactant-foaming sol−gel method to effectively disrupt and reconstruct the inherent GO LCs via microbubbles as templates, we achieve the large-size and structure-intact graphene hydrogel bulk (GHB). After simple freezing and air-drying, the resulting graphene aerogel bulk (GAB) with a structure-intact size of about 1 m 2 exhibits a superelasticity of up to 99% compressive strain, ultralow density of 2.8 mg cm −3 , and quick solar-thermal conversion ability. The modified GAB (GABTP) shows a high decomposition temperature (T max ) of 735 °C in air and a low heat storage capacity. These excellent performances make the GABs suitable for many practical applications, as proven in this work, including as high compressive force absorbers, high absorption materials for oils or dangerous solvents, superior solar-thermal management materials for rapid heater or controlled shelter, and high-efficiency fire-resistant and thermal insulation materials. The whole preparation process is easily scalable and cost-effective for mass production of structureintact multifunctional graphene aerogel bulk toward practical applications.

The emerging flexible electronic devices have stimulated the development of flexible batteries, in which flexible electrodes are indispensable components. Graphene, known for its excellent electrical conductivity and mechanical stability, can be used as an ideal flexible substrate. Recently, many efforts have been devoted to graphene-based electrodes for flexible batteries. Herein, this review summarizes recent advances in the development of graphene-based electrodes for various flexible batteries, including metal-ion batteries (ions of Li, Na, Zn, Al, etc.), lithiumsulfur batteries, and metal-air batteries (Li-and Zn-air batteries). Besides, major challenges and future developments of flexible batteries are also discussed. K E Y W O R D S flexible batteries, flexible electrodes, graphene

Potassium-ion batteries (KIBs) are emerging as one of the most promising candidates for large-scale energy storage owing to the natural abundance of the materials required for their fabrication and the fact that their intercalation mechanism is identical to that of lithium-ion batteries. However, the larger ionic radius of K + is likely to induce larger volume expansion and sluggish kinetics, resulting in low specific capacity and unsatisfactory cycle stability. A new Ni/ Mn-based layered oxide, P2-type K 0.44 Ni 0.22 Mn 0.78 O 2 , is designed and synthesized. A cathode designed using this material delivers a high specific capacity of 125.5 mAh g −1 at 10 mA g −1 , good cycle stability with capacity retention of 67% over 500 cycles and fast kinetic properties. In situ X-ray diffraction recorded for the initial two cycles reveals single solid-solution processes under P2-type framework with small volume change of 1.5%. Moreover, a cathode electrolyte interphase layer is observed on the surface of the electrode after cycling with possible components of K 2 CO 3 , RCO 2 K, KOR, KF, etc. A full cell using K 0.44 Ni 0.22 Mn 0.78 O 2 as the cathode and soft carbon as the anode also exhibits exceptional performance, with capacity retention of 90% over 500 cycles as well as superior rate performance. These findings suggest P2-K 0.44 Ni 0.22 Mn 0.78 O 2 is a promising candidate as a high-performance cathode for KIBs.

An aqueous rechargeable micro-Zn–MnO2 battery with high voltage output and good cycling performance is fabricated via simple laser-assisted machining and electrochemical deposition technology.

In this work, a new type of hybrid energy storage device is constructed by combining the zinc-ion supercapacitor and zinc–air battery in mild electrolyte. Reduced graphene oxide with rich defects, large surface area, and abundant oxygen-containing functional groups is used as active material, which exhibits two kinds of charge storage mechanisms of capacitor and battery simultaneously. Apart from the physical adsorption/desorption of anions on the surface of graphene, the zinc ions in electrolyte will be electrochemically adsorbed/desorbed onto the oxygen-containing groups of graphene during the charge/discharge process, contributing extra capacitance to the device. Moreover, the defects in graphene will further improve the electrochemical performance of the energy storage device via catalyzing the oxygen reduction reaction with exposure to air. Consequently, the synergistic effect leads to a record high capacitance of 370.8 F g–1 at a current density of 0.1 A g–1, which is higher than that of zinc-ion supercapacitors reported previously. Furthermore, the hybrid device exhibits a superior cycling stability with 94.5% capacitance retention even after 10000 charge/discharge cycles at a high current density of 5 A g–1. Interestingly, the developed hybrid device can be self-charging automatically after the power is exhausted in the ambient atmosphere. Other electrode materials, such as carbon nanotube paper, are also used to build a hybrid device to verify the feasibility of this strategy. This facile, green, and convenient strategy provides new insight for developing a high performance storage device, showing great application prospect in other hybrid energy storage devices in mild electrolyte.

This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record.

Flexible aqueous rechargeable batteries that integrate excellent mechanical flexibility and reliable safety hold a great promise for next‐generation wearable electronics. Unfortunately, currently available options are unsatisfactory due to their low specific capacity, limited energy density, and unstable voltage output. Herein, to overcome these challenges, high theoretical specific capacity zinc and sulfur as the anode and cathode are selected, respectively. Furthermore, a strategy is proposed, that decoupling charge carriers in anolyte and catholyte to simultaneously endow the zinc anode and sulfur cathode with optimal redox chemistry, maximizes the energy storage of flexible aqueous batteries. The new zinc–sulfur hybrid battery possesses merits of ultrahigh theoretical specific capacity (3350 mAh gS−1) and volumetric energy density (3868 Wh L−1), low cost, ecofriendliness, and ease of fabrication and is a promising next‐generation aqueous energy storage system. The fabricated flexible aqueous zinc–sulfur hybrid battery delivers a stable output voltage (release 92% of its full capacity within a small voltage drop of 0.15 V) and an ultrahigh reversible capacity of 2063 mAh gS−1 at 100 mA gS−1, thus setting a new benchmark for flexible aqueous batteries and is promising to play a part in future flexible electronics.