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Micro energy storage devices (MESDs) have emerged as promising energy providers for micro applications due to their integrated performance. However, the limited cycle life and low power density of microbattery, and low energy density of microsupercapacitor have consistently impeded their broader practical implementation. Herein, to obtain a MESD with a long cycle life, excellent power density, and superior energy density, a novel micro battery‐supercapacitor hybrid (MBSH) device is fabricated. Two types of 3D microelectrodes are fabricated, namely, a nanowire network anode based on PEDOT‐TiON and a porous cathode based on Ni(OH)2. Benefiting from the unique hydrophobic characteristics of the PEDOT layer, high electrical conductivity of TiON, and high conductivity, and abundant ion diffusion channels of network microstructure, PEDOT‐TiON NW microelectrodes demonstrate exceptional cycling stability by retaining 70% of their capacity after 40 000 cycles. The achieved MBSH exhibits an extended voltage window ranging from 0 to 1.9 V, impressive power density of 77.5 mW cm−2, and a superior energy density of 55.6 µWh cm−2. Furthermore, it maintains a remarkable capacity retention rate of 71.6% even after undergoing 30 000 cycles. This innovative design paves the way for the developing of high‐performance microdevices with superior electrochemical properties. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) has been recognized as an ideal supporter owning to its abundant hydroxyl groups on the surface. In this work, Keggin-type phosphotungstic acid (H3PW12O40, PWA) is self-anchored on the three-dimensional network of BC by a simple diffusion method at room-temperature. BC fibers can protect the well-dispersed PWA with high transparency, high mechanical strength, and high stability. When PWA/BC serves as a photochromic material, the coloration time and bleaching time are only 3 min and 30 min respectively. After 6 cycles, the photochromic ability of the PWA/BC composite film almost unchanged. At the same time, we convert the coloration and bleaching degree into quantitative data including a color difference calculation of ΔE2000 and the remaining degree of color (RC%). Within the BC system, PWA exhibits a special linear relationship between RC% and bleaching time (0–30 min). The processes of PWA/BC reduction (W6+→W5+) and oxidation (W5+→W6+) are analysed by photo-electrochromic, XPS and ESR characterizations. The revealed excellent photochromic properties of soft PWA/BC films highlight their potential as the photoresponsive materials.

Aqueous zinc‐ion batteries (AZIBs) have become a promising alternative energy storage device due to their lower cost and better safety performance than lithium‐ion batteries (LIBs). However, the biggest challenge is the need to develop electrode materials with higher capacity and longer life than LIBs at present. Herein this work, a tunnel‐structured sodium vanadate (NaV6O15) is synthesized by molten salt method as the cathode materials for AZIBs. The prepared NaV6O15 nanosheets have a high specific capacity of 325 mAh g−1 at a current density of 0.1 A g−1, and the capacity retention rate is as high as 127.08% under 1000 cycling at a current density of 1 A g−1. This excellent performance is mainly attributed to the stable tunneled structure, which provides an effective diffusion path for Zn2+ insertion and avoids structural damage. Herein the subsequent cycles, Zn2+ is mainly inserted/extracted in NaV6O15 and Zn3(OH)2V2O7·2H2O. The preparation of NaV6O15 cathode materials and the molten salt method provide a certain reference value for the development of AZIBs in this work. [ABSTRACT FROM AUTHOR]

Manganese oxides (MnOx) have been extensively investigated due to their extremely high theoretical capacities for application as conversion anodes in lithium-ion batteries. However, fully performing their theoretical performance still faces poor electric conductivity and serious volume change upon lithium insertion/extraction. Herein, we demonstrate encapsulating manganese oxide nanoparticles within a conducting polymer polypyrrole (PPy) shell as a facile strategy to overcome such flaws through in situ redox reaction and oxidative polymerization process. Such an in situ method combines the redox reaction between potassium permanganate and tetrahydrofuran to form MnOx nanoparticles and the subsequent oxidative polymerization of pyrrole to form a conductive polypyrrole coating shell by the oxidant KMnO4 into one step. For the as-fabricated products (MnOx@PPy), this tenderly introduced conductive PPy shell highly favors the fast electron transfer and preserves the electrode structure integrity upon repeated cycling. As the anode for LIBs, MnOx@PPy exhibits superior lithium storage performance with a high reversible capacity (1538 mAh·g−1), long-life cyclability (747 mAh·g−1 after 1000 cycles at 1.0C) and durable ratability (574 mAh·g−1 at 2.0C). This work demonstrates that the convenient in situ strategy to form conductive polymer coating shell is effective to improve the performance of conversion anodes and can be extended to other materials for energy storage applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Self-anchored PWA on the three-dimensional network of BC with flexible, quick-response and stable cycling performance for photochromic application. • PWA self-anchored through the bridging oxygen interaction with –OH groups of BC. • Quick-response of the coloration time (3 min) and bleaching time (30 min). • A charge transfer bridge of PWA/BC greatly improves the mechanical properties. • 6 cycles test confirms the stable performance with retention rate up to 99.6%. Bacterial cellulose (BC) has been recognized as an ideal supporter owning to its abundant hydroxyl groups on the surface. In this work, Keggin-type phosphotungstic acid (H 3 PW 12 O 40 , PWA) is self-anchored on the three-dimensional network of BC by a simple diffusion method at room-temperature. BC fibers can protect the well-dispersed PWA with high transparency, high mechanical strength, and high stability. When PWA/BC serves as a photochromic material, the coloration time and bleaching time are only 3 min and 30 min respectively. After 6 cycles, the photochromic ability of the PWA/BC composite film almost unchanged. At the same time, we convert the coloration and bleaching degree into quantitative data including a color difference calculation of ΔE 2000 and the remaining degree of color (RC%). Within the BC system, PWA exhibits a special linear relationship between RC% and bleaching time (0–30 min). The processes of PWA/BC reduction (W6+→W5+) and oxidation (W5+→W6+) are analysed by photo-electrochromic, XPS and ESR characterizations. The revealed excellent photochromic properties of soft PWA/BC films highlight their potential as the photoresponsive materials. [ABSTRACT FROM AUTHOR]

ABSTRACT The Li 1.20 [Mn 0.52- x Gd x Ni 0.20 Co 0.08 ]O 2 (x = 0, 0.01, 0.02, 0.03) cathode materials have been synthesized by using the combination of co-precipitation with high temperature sintering method. The XRD, SEM, TEM and galvanostatic charge-discharge tests were carried out to study the influence of Gd3+ doping on the crystal structural, morphology and electrochemical properties of Li 1.20 [Mn 0.52 Ni 0.20 Ni 0.08 ]O 2. The XRD result revealed the Gd3+ doping modification could decrease the cation mixing degree. The galvanostatic charge-discharge tests results showed the improved electrochemical properties were obtained through the Gd3+ doping modification. With the increase of Gd3+ doping content, the capacity retentions enhanced from 88.1% to 90.3% and then decrease to 87.0% after 100 cycles with x = 0.01, 0.02 and 0.03, respectively, while the un-doped sample delivered the capacity retention of 85.1%. The Li 1.20 [Mn 0.50 Gd 0.02 Ni 0.20 Co 0.08 ]O 2 exhibited a discharge capacity of 115.5 mAh g−1 at 5C rate, much larger than that (85.1 mAh g−1) of the un-doped Li 1.20 [Mn 0.52 Ni 0.20 Co 0.08 ]O 2. The cyclic voltammetric analysis has proved that the Gd3+ doping modification can keep the stability of the cathode layer structure and further hold the high working voltage. Graphical abstract Unlabelled Image Highlights • The Li 1.20 [Mn 0.52-x Gd x Ni 0.20 Co 0.08 ]O 2 (x = 0, 0.01, 0.02, 0.03) have been synthesized successfully. • The crystallization property and cation ordering have been improved by the Gd 3 + doping modification. • The discharge capacity of Li 1.20 [Mn 0.50 Gd 0.02 Ni 0.20 Co 0.08 ]O 2 is 24.4 mAh g− 1 than that of the pristine cathode at 5C rate. • Li 1.20 [Mn 0.50 Gd 0.02 Ni 0.20 Co 0.08 ]O 2 delivers the optimal cycling performance. [ABSTRACT FROM AUTHOR]

LiNi 1−x−y Co x Al y O 2 is a commonly used Ni-rich cathode material because of its relatively low cost, excellent rate capability and high gravimetric energy density. Surface modification is an efficient way to overcome the shortcomings of Ni-rich cathodes such as poor cycling stability and poor thermal stability. A high-powered concentration-gradient cathode material with an average composition of LiNi 0.815 Co 0.15 Al 0.035 O 2 (LGNCAO) has been successfully synthesized by using spherical concentration-gradient Ni 0.815 Co 0.15 Al 0.035 (OH) 2 (GNCA)as the starting material. An efficient design of the Al 3+ precipitation method is developed, which enables obtaining spherical GNCA with ∼10 μm particle size and high tap density. In LGNCAO, the nickel and cobalt concentration decreases gradually whereas the aluminum concentration increases from the centre to the outer layer of each particle. Electrochemical performance and storage properties of LGNCAO have been investigated comparatively. The LGNCAO displays better electrochemical performance and improved storage stability than LNCAO. [ABSTRACT FROM AUTHOR]

We report the outstanding electrochemical performance of LiNi 0.5 Mn 1.5 O 4 porous microellipsoids with a core–shell configuration synthesized by a simple self-template method. The structure and electrochemical properties of the products are investigated via X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller method and various electrochemical analysis techniques. LiNi 0.5 Mn 1.5 O 4 porous microellipsoids have a discharge capacity of 110.3 mA h g −1 after 400 cycles at a rate of 5C (735 mA g −1 ). The capacity retention ratio is 93.7% of the maximum capacity (142.3 mA h g −1 ) after 150 cycles under 5C rate at elevated temperature (55 °C). The porous ellipsoidal product could be a promising cathode material for high-performance lithium ion batteries. [ABSTRACT FROM AUTHOR]

• The pine needles as the sandwich material have a hollow structure similar to carbon nanotubes, and cherry wood veneer as the external cladding layer has abundant pore channels. • Cobalt nanoparticles are covered by carbon nanospheres to avoid corrosion by electrolyte. • The sandwich structure is more stable, which can reduce dopant shedding, and the service life is long. • Thin block electrodes do not require fluid collection and multiple cell sheets are stacked to store more energy. [Display omitted] In order to improve the electrochemical performance of biomass electrodes and prolong their service life, the Co2+ doped sandwich structure woodceramics composite electrode is prepared by utilizing cherry wood veneer and pine needle carbon powder as external cladding layer and core layer, respectively, accompanying with catalyst and dopant Co(NO 3) 2.6H 2 O. Scanning electron microscopy (SEM) reveals that a three-dimensional network can be obtained by an external cladding layer which maintains natural pore structures and pine needle toner core layer which possesses the hollow tubular structure attach with the transverse holes tube wall. Transmission electron microscopy (TEM) results exhibit that the doped Co nanoparticles are wrapped by graphitized carbon which improves the corrosion retardancy and prolongs the service life of electrodes. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) analysis indicates that the doped Co2+ exists mainly as metallic cobalt (Co) after a series of reactions, but also with a small amount of Co2+. The electrochemical measurements presents that the specific capacitance of the resultant electrodes can reach 319 F g−1 specific capacitance and capacitance retention rate can maintain 98.7% after 15,000 cycles under 0.1 A g−1 current density in the inorganic system (6 mol L−1 KOH). The practical assembled in symmetrical capacitor with the energy density of 33.86 Wh kg−1 has been performed at a power density of 100 W kg−1. Those enhanced performances explain that this novel sustainable sandwich electrode has a good potential for practical application with a long cycle life. [ABSTRACT FROM AUTHOR]

• Decahedral Cu1.8Se@C nano-composites were fabricated using Cu-BTC templates. • The synergistic effects of nanomaterials improved the reversible capacity of anode. • We provides a new strategy to improve the lithium storage performance. Transition metal selenides (TMSs) are potential high-power lithium-ion batteries (LIBs) electrode materials because of its considerable theoretical capacity and high electrical conductivity. However, through the electrochemical conversion reaction, the structure of TMSs may be easily destroyed due to its terrible volume effect, which thereby greatly reducing the electrode's capacitance and cycle life. In this paper, we have synthesized carbon-encapsulated Cu 1.8 Se decahedron nano-composites (Cu 1.8 Se@C) using a metal–organic framework Cu-BTC as template. When applied in anode for LIBs, due to the synergistic effects of tiny copper selenide, integral porous decahedron and exceptional carbon-encapsulated structure, the Cu 1.8 Se@C nano-composites exhibit improved specific capacity, superior rate capability and exceptional cycling stability. The initial discharge specific capacity of Cu 1.8 Se@C-500 °C is 1186.6 mAh g−1 at a current density of 0.1 A g−1, and after 200 cycles, the specific capacity drops to 824.4 mAh g−1. What's more, at a current density of 1 A g−1, the Cu 1.8 Se@C-500 °C electrode still possesses a considerable specific capacity of 320.3 mAh g−1 after 1000 cycles. In light of our findings, we propose a metal–organic frameworks (MOFs) templates strategy to synthesize in situ carbon-encapsulated TMSs electrode materials with outstanding electrochemical performance for LIBs. [ABSTRACT FROM AUTHOR]