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Abstract: Approaching state‐of‐the‐art areal and volumetric capacitances while maintaining high‐power characteristic is a big challenge that promotes practical application of flexible solid‐state micro‐supercapacitors (MSCs), which have recently attracted great attention with the rapid development of flexible microelectronics. Herein, it is reported that freestanding extrahigh conductive Ti3C2Tx (MXene) films with excellent flexibility and effectively controlled thickness ranging from 1–21 µm performed as excellently scalable and flexible solid‐state MSCs owing to their ultrahigh underlying electrical conductivity (up to 1.25 × 105 S m−1) and self‐functionalized surfaces (O, OH, and F terminations). Amazingly, freestanding conductive Ti3C2Tx based flexible solid‐state MSCs with interdigital electrodes and polyvinyl alcohol/sulfuric acid (PVA/H2SO4) gel electrolyte display outstanding areal capacitances of 340 mF cm−2 at 0.25 mA cm−2 based on the two working electrodes. Moreover, the maximum corresponding volumetric capacitance and energy density of flexible solid‐state MSCs reach up to 183 F cm−3 and 12.4 mWh cm−3, which is on the topmost level among all the unconventional supercapacitors to date. Compared with materials currently used in MSCs, this freestanding conductive Ti3C2Tx shows potential and scalability in increasing overall micro‐supercapacitor performance, which evidently sheds light on promising application of freestanding conductive MXenes for next‐generation flexible, portable, and integrated MSCs. [ABSTRACT FROM AUTHOR]

Thermodynamically induced tensile stress in the perovskite film will lead to the formation of atomic vacancies, seriously destroying the photovoltaic efficiency stability of the perovskite solar cells (PSCs). Among them, cations and halide anions vacancies are unavoidable; these point vacancies are considered to be a major source of the ionic migration and perovskite degradation at the crystal boundary and surface of the perovskite films. Here, we use choline bromide to modify the perovskite film by occupying the atomic defects in the CsPbBr 3 perovskite film. The results show that the zwitterion quaternary ammonium ions and bromide ions in choline bromide can simultaneously occupy the Cs + cation and Br - anions vacancies in the perovskite film by the ionic bonding effect, for which the defect-state density on the surface of the perovskite film can be significantly reduced, leading to the effective enhancement of carrier lifetime. In addition, the residual stress at the crystal boundary can be effectively reduced by lowering the Young's modulus in the CsPbBr 3 perovskite film. As a result, the optimized device achieves a photoelectric conversion efficiency (PCE) of 9.06% with an increase of 41.1% compared to the control device with a PCE of 6.42%. Most importantly, the newborn thermal stress due to thermal expansion during heat working conditions can be transferred from the polycrystalline perovskite to the carbon layer by the matched Young's modulus, thus resulting in improved stability perovskite film under environmental conditions. The work provides new insights for preparing high-quality perovskite films with low defect-state density and residual stress.

Silicon (Si) anode materials have attracted substantial interest due to their high theoretical capacity. Here, the growth of helical Si@Cu 3 Si nanorod arrays via glancing angle deposition (GLAD) followed by an annealing process is reported. Pre-deposited Cu atoms were driven into Si-nanorods and successfully reacted with Si to form a Si-Cu alloy at a high temperature. By varying the rotation rate and annealing temperature, the resultant Si@Cu 3 Si nanorod arrays showed a reasonably accessible surface area with precise control spacing behavior in favor of accommodating Si volume expansion. Meanwhile, the Si@Cu 3 Si anode materials showed higher electrical conductivity, facilitating Li + ion diffusion and electron transfer. The Si@Cu 3 Si nanorod arrays in half cells exhibited a volumetric capacity as high as 3350.1 mA h cm -3 at a rate of 0.25 C and could maintain 1706.7 mA h cm -3 after 100 cycles, which are superior to those of pristine Si materials. This facile and innovative technology provided new insights into the development of Si-based electrode materials.

Three-dimensional (3D) hybrid networks consisting of reduced graphene oxide (rGO) sheets interconnected by Co 3 O 4 nanowires (rGO/Co 3 O 4 ), followed by the decoration of Fe 2 O 3 nanospheres (NSs) (rGO/Co 3 O 4 @Fe 2 O 3 ), were demonstrated by a facile hydrothermal method, with which the rGO/Co 3 O 4 networks acted as nucleation sites for the in situ synthesis of Fe 2 O 3 NSs. The intimate contacts between rGO, Co 3 O 4 NWs and Fe 2 O 3 NSs, which result in an excellent conductive behavior, provide a unique structure with huge potential for electrochemical property promoted electrochemical supercapacitors. The rGO/Co 3 O 4 @Fe 2 O 3 hybrid networks as electrodes exhibit a high capacitance of 784 F g -1 at 1 A g -1 with 83% retention of the initial capacitance as the current density increases from 1 to 10 A g -1 , which is explained by the graphene-based interconnected structure owing to the advantages of accommodating the volume expansion between Co 3 O 4 NWs and Fe 2 O 3 NSs. The supercapacitor was assembled by applying a nickel aluminum layered double hydroxide (NiAl-LDH) structure and rGO/Co 3 O 4 @Fe 2 O 3 as the electrode materials and yields an energy density of 70.78 W h kg -1 at a power density of 0.29 kW kg -1 . The energy density can maintain 24.24 W h kg -1 with 9.94 kW kg -1 .

Solid-state composite polymer electrolytes (CPEs) usually suffer from intrinsic low ionic conductivity and a solid-solid interface, badly inhibiting their widespread commercial application in all-solid-state Li-metal battery (ASSLMB) energy storage. Herein, a synergetic strategy using strong Lewis acid-base and weak hydrogen bonds was employed for self-assembly in situ construction of three-dimensional (3D) network-structured poly(ethylene oxide) (PEO) and SiO 2 CPEs (PEO@SiO 2 ). Ascribed to this synergistically rigid-flexible coupling dynamic strategy, a harmonious incorporation of monodispersed SiO 2 nanoparticles into PEO could remarkably reduce crystallinity of PEO, significantly enhancing the ionic conductivity (∼1.1 × 10 -4 S cm -1 at 30 °C) and dramatically facilitating solid electrolyte interface stabilization (electrochemical stability window > 4.8 V at 90 °C). Moreover, the PEO@SiO 2 -based ASSLMBs possess excellent rate capability over a wide temperature range (∼105 mA h g -1 under 2 C at 90 °C), high temperature cycling capacity (retaining 90 mA h g -1 after 100 cycles at 90 °C), and high specific capacity (146 mA h g -1 under 0.3 C at 90 °C). Unambiguously, these high ionic conductivity CPEs along with excellent flexibility and safety can be one of the most promising candidates for high-performance ASSLMBs, evidently revealing that this synergistically rigid-flexible coupling dynamic strategy will open up a way to exploit the novel high ionic conductivity solid-state electrolytes.