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Germanium (Ge) is a promising anode material for lithium-ion batteries due to its large theoretical specific capacity, good electrical conductivity, and fast lithium-ion diffusivity. However, Ge still suffers from huge volume expansion during the delithiation/lithiation process. Herein, using "Mg" as a soft template, a honeycomb-like porous Ge (hp-Ge) anode was successfully synthesized via a facile thermal nitridation of Mg2Ge in N2, followed by an acid-etching process. The obtained hp-Ge presents a typical void-containing micro-/nano-hierarchical porous architecture, which can effectively alleviate the volume expansion of the host Ge. The formation of uniformly distributed voids in hp-Ge is closely related to the etching of Mg3N2, which is the by-product of the reaction between Mg2Ge and N2. Benefiting from the fascinating micro-/nano-hierarchical porous structure, the resulting hp-Ge anode without employing any complex surface modification techniques demonstrated a high specific capacity of 1534.70 mAh g−1 at 0.2 A g−1 with a high initial Coulombic efficiency of 85.0%, and a high capacity of 483.9 mAh g−1 at 8 A g−1. The hp-Ge anode also possesses excellent cyclability and can deliver a satisfying reversible specific capacity of 1375.40 mA h g−1 at 0.5 A g−1 after 200 cycles with a high capacity retention of 96.8%. The proposed facile and scalable void-introducing strategy in this study also provides an alternative route for designing advanced micro-/nano-hierarchical porous materials, especially for anodes with large volume expansion during the lithiation process. [ABSTRACT FROM AUTHOR]

A porous MA–VA–PcNi polymer was prepared by grafting nickel phthalocyanine (PcNi) onto the main chain of a maleic anhydride–vinyl acetate (MA–VA) polymer, and an MA–VA–PcNi electrode is prepared by electrospinning technology to inhibit the agglomeration of the active powder effectively, which produces spherical particles with a diameter of 100–300 nm. The synthesized MA–VA–PcNi polymer is used as the anode for lithium-ion and sodium-ion batteries, exhibiting excellent energy storage behaviors. The MA–VA–PcNi/Li battery displays a high capacity of 610 mA h g−1 and can still remain at 507 mA h g−1 with a retention rate of 83.1% after 400 cycles at a current density of 200 mA g−1. Even at a high current density of 2 A g−1, the specific capacity can remain at 195 mA h g−1. In addition, the MA–VA–PcNi/Na battery displays a high capacity of 336 mA h g−1 and can still remain at 278 mA h g−1 with a retention rate of 82.7% after 400 cycles at a current density of 100 mA g−1. A high specific capacity of 164 mA h g−1 can also be achieved at a high current density of 1 A g−1. After nickel phthalocyanine (PcNi) was grafted onto the MA–VA polymer, aggregation between phthalocyanine rings was effectively prevented, and this exposes more active sites. At the same time, the spherical particles obtained by electrospinning technology further improve the dispersion and increase the number of active sites of the active materials. Finally, the electrode materials show excellent energy storage behavior for lithium-ion and sodium-ion batteries, which provides a new idea for designing high-performance energy storage materials for organic electrodes. [ABSTRACT FROM AUTHOR]

Compared with the cathode materials, the research on the anode materials of the sodium‐ion batteries has lagged behind. Therefore, development of the anode materials with high capacity, long life, and excellent rate properties is the key to unlocking the practical application for sodium‐ion batteries. This study presents the preparation of hierarchical porous hard carbon as an active anode material from rice husks. The as‐synthesized materials are characterized by X‐ray diffraction, N2 adsorption, Raman spectra, scanning electron microscopy and transmission electron microscopy. These porous hard carbon materials exhibit a high specific surface area and are promising for reversible sodium storage. Galvanostatic studies show that the specific initial capacities of all samples were in the range of 130–300 mA h g−1 at a current density of 100 mA g−1 between 0.01 V and 2.3 V. Compared to the other samples, the hard carbon materials prepared at 800 °C from rice husk (RHPC‐800) can deliver a high reversible capacity of 274 mA h g−1 at a current density of 25 mA g−1, maintain a capacity of approximately 260 mA h g−1, and retain 92.7 % of its capacity after 500 cycles. This excellent electrochemical performance of the as‐prepared RHPC‐800 material is attributed to the high specific surface area and low charge transfer resistance. [ABSTRACT FROM AUTHOR]

The vast volume expansion of Si anode during lithiation process leads to poor cyclability and low initial coulombic efficiency (ICE), and thus seriously hampers its applications in lithium-ion batteries (LIBs). To overcome these obstacles, in this study, a double core-shell structure stabilized hierarchical porous Si (p-Si) microsphere was synthesized through a graphene-involved electrostatic self-assembly process coupled with a solvent-confined TiO 2 (sc-TiO 2) monomicelle assembly strategy. The advanced solvent-confined monomicelle assembly process enables the uniform deposition of ultra-thin TiO 2 layer on p-Si@graphene (p-Si@G) microsphere. The G/sc-TiO 2 hybrid double shell layer can significantly consolidate porous structure of p-Si microsphere and simultaneously improve the ICE value of p-Si@G@sc-TiO 2 microsphere. The resulting p-Si@G@sc-TiO 2 composite shows a high capacity value of 2597.9 mAh g−1 at 0.2 A g−1 with a high ICE value of 80.59%. The p-Si@G@sc-TiO 2 composite also demonstrates excellent rate capability with capacity of 802.53 mAh g−1 at 8 A g−1 and outstanding cyclability with capacity retention of 68% (1005.1 mAh g−1) after 300 cycles at 2 A g−1, superior to that of p-Si, p-Si@G as well as p-Si@G@TiO 2 microsphere preparing by traditional sol-gel TiO 2 coating method, suggesting its promising applications in LIBs. [ABSTRACT FROM AUTHOR]

Phthalocyanine-based covalent organic frameworks (NA-NiPc , PPDA-NiPc and DAB-NiPc) with different pore sizes are synthesized by a catalyst-free coupling reaction, which inhibits dissolution in the electrolyte and provides large specific surface area and open mesoporous channels for Li+. As the pore size of the frame increases, the surface area of the material increases accordingly, resulting in improved electrochemical behaviors. The NA-NiPc , PPDA-NiPc and DAB-NiPc electrodes display high capacity, long cycling stability, and excellent rate capability both in LIBs and NIBs. [Display omitted] • Pc-based frameworks with different pore sizes of 1.55, 2.11 and 2.74 nm are synthesized. • No solubility in electrolyte and large specific surface areas are observed. • The surface area increases with the pore size, resulting in improved electrochemical behaviors. • Excellent capacity, cycle stability, and rate capability both in LIBs and NIBs are observed. In this work, three kinds of phthalocyanine-based covalent organic frameworks, NA-NiPc (4-nitronickel phthalocyanine + 4-aminonickel phthalocyanine), PPDA-NiPc (4-nitronickel phthalocyanine + p-phenylenediamine) and DAB-NiPc (4-nitronickel phthalocyanine + 4,4′-diaminobiphenyl), with different pore sizes are synthesized by a catalyst-free coupling reaction. The X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Transmission electron microscopy (TEM) test results indicate that the pore sizes of the NA-NiPc , PPDA-NiPc and DAB-NiPc frameworks are approximately 1.55 nm, 2.11 nm and 2.74 nm, respectively, which is consistent with the simulated results after optimizing the geometric conformation by HyperChem software; additionally, the specific surface areas are 382, 471 and 575 m2 g−1 respectively. As the pore size of the frame increases, the surface area of the material increases accordingly, resulting in different electrochemical behaviors. The initial capacities of the NA-NiPc , PPDA-NiPc and DAB-NiPc electrodes in lithium-ion batteries are 422, 469 and 566 mAh/g, respectively, and after 700 cycles, the capacities remain at 557, 670 and 941 mAh/g, demonstrating capacity retention rates of 131.8%, 142.9% and 166%, respectively, at a current density of 100 mA/g. Even at a high current density of 2 A/g, high specific capacities of 385, 512 and 767 mAh/g can still be observed. Moreover, the use of the NA-NiPc , PPDA-NiPc and DAB-NiPc electrodes in sodium-ion batteries also display excellent behaviors, such as high capacities, stable cycling performances and excellent rate capabilities. With increasing framework porosity, the performances of both lithium-ion and sodium-ion batteries gradually improve, fully indicating that the size of the framework is the key factor in determining the performance of a battery. [ABSTRACT FROM AUTHOR]

• Tremella-like porous SnO 2 Microsphere and its CNTs hybrids are first constructed controllably under microwave radiation. • They express superior lithium storage performances as anode materials. • SnO 2 -S/CNTs hybrids remain 470.16 mAhg–1 after 550 cycles at the current density of 1.0 Ag–1. • Synergistic effects on morphologies, structures and properties for both SnO 2 -S and SnO 2 -S/CNTs are illustrated. To improve the electrochemical performance of SnO 2 -based electrode materials, a simple and efficient method was developed for constructing porous SnO 2 microsphere (p-SnO 2 MS) and its carbon nanotube hybrids (p-SnO 2 MS/CNTs), for the first time, by only changing solvent kinds under microwave-radiation conditions. After their microstructures and electrochemical properties were investigated, it is noted to find that the proposed p-SnO 2 MS assembled by nano plates is mainly composed of rutile phase with a little orthorhombic phase. Among all single SnO 2 materials with different morphologies, p-SnO 2 MS displays a charge capacity of 860.59 mAhg–1 after 50 cycles, and a charge capacity of 593.37 mAhg–1 at the current density of 4.0 Ag–1. Once hybridized with CNTs, the corresponding charge capacity of p-SnO 2 MS/CNTs would improve to 926.58 mAhg–1 and 625.50 mAhg–1 respectively under the same conditions. Importantly, p-SnO 2 MS/CNTs could deliver quite a stable charge capacity of 478.53 mAhg–1 after 600 cycles at 1.0 Ag–1 in Li/p-SnO 2 MS/CNTs half cells and a high specific capacity of 738.03 mAhg–1 after 100 cycles in p-SnO 2 MS/CNTs/LiNi 0.5 Co 0.2 Mn 0.3 O 2 full cells. The relationship between micro-structure and improved electrochemical performance is investigated in detail for both p-SnO 2 MS and p-SnO 2 MS/CNTs. This work will offer a promising insight into constructing some practical anode materials with improved lithium storage performances. [ABSTRACT FROM AUTHOR]

• Binder free electrode composed of Cu 2 O/CuO/Cu/Carbon-polymer fibers are synthesized by a facile anodic electrochemical deposition method. • The Cu 2 O/CuO are uniformly dispersed on the surface of polymer fibers with fluffy morphology, which is very beneficial to the transport of Li+. • The Cu 2 O/CuO/Cu/Caron-polymer electrode exhibits excellent properties such as high capacities, good cycling stabilities and rate capacities. • The facile anodic electrochemical deposition method adopted in this work is simple, green and inexpensive. ga1 Design of Cu 2 O/CuO nanocomposites as anode materials for lithium-ion batteries has attracted extensive attention because of their potential applications in the energy field. Herein, in this work, the coordination polymers of Cu2+ and flexible chain-like α, ω-dicarboxylate (succinate and sebacate) are synthesized by a facile anodic electrochemical deposition method, in which succinic acid/sebacic acid is used as electrolyte and the copper foil is used as electrodes. The obtained Cu(α, ω-dicarboxylate) polymers grown on copper foil substrate are decomposed and oxidized to prepare a Cu 2 O/CuO/Cu/Carbon-polymer composite fibers, in which the nanoparticles of Cu 2 O/CuO/Cu are uniformly incorporated into a fibrous carbon-polymer, which can facilitate Li+ ion diffusion to active sites in the electrodes and alleviate the volume expansion during the charge and discharge process. As a result, the Cu 2 O/CuO/Cu/Carbon-polymer composite fibers can be used as novel binder free anode materials for lithium-ion batteries, which displays high capacity, excellent cycle stability and rate performance. The initial discharge capacity of composite fibers electrode derived from Cu (sebacate) polymers (Cu-C10) is as high as 508.9 mAh/g at the current densities of 50 mA·g−1. After 150 cycles, the capacity can still remain at 479.9 mAh/g with capacity retention rate of 94.3%. The preparation of electrodes by novel electrochemical deposition in this work would provide a new insight for preparing advanced binder free metal oxide/carbon-based anodes for LIBs with environmental friendliness and inexpensive. [ABSTRACT FROM AUTHOR]