Sandwich shelled TiO2@Co3O4@Co3O4/C hollow spheres as anode materials for lithium ion batteries

Exploration of electrochemical behavior of Sb-based porous carbon composites anode for sodium-ion batteries

Sb-based materials are considered as promising anode materials for sodium-ion batteries (SIBs) due to their excellent sodium storage capacities and suitable potentials. However, the Sb-based anodes usually suffer from intense volume expansion and severe pulverization during the alloying-dealloying process, resulting in poor cycling performance. Herein, a composite anode with Sb/Sb2O3 nanoparticles embedded in N-doped porous carbon is prepared by the gas-solid dual template method. The volume change of the anode material is mitigated by the carbon layer enwrapping and the confinement of the porous structure. Nitrogen doping provides abundant sodium storage sites, thus enhancing the storage capacity of sodium ion. Furthermore, to gain the accurate kinetic interpretation of the electrochemical process, an ex-situ transmission electron microscope (TEM) characterization combined with distribution of relaxation times (DRT) is conducted. The Sb/Sb2O3@NPC-1.0 demonstrates excellent electrochemical performance, achieving 340.3 mAh g-1 at 1A g-1, and maintains a capacity of 86.7 % after 1000 cycles. This work paves the way for the practical application of SIBs with high-performance and long-life Sb-based anodes.

Enhanced photocatalytic ammonia oxidation over WO3@TiO2 heterostructures by constructing an interfacial electric field

WO3 nanorods and xWO3@TiO2 (WO3/TiO2 mass ratio (x) = 1-5) photocatalysts were synthesized using the hydrothermal and sol-gel methods, respectively. The photocatalytic activities of xWO3@TiO2 for NH3 oxidation first increased and then decreased with a rise in TiO2 content. Among them, the heterostructured 3WO3@TiO2 photocatalyst showed the highest NH3 conversion (58 %) under the simulated sunlight irradiation, which was about two times higher than those of WO3 and TiO2. Furthermore, the smallest amounts of by-products (i.e., NO and NO2) were produced over 3WO3@TiO2. The enhancement in photocatalytic performance (i.e., NH3 conversion and N2 selectivity) of 3WO3@TiO2 was mainly attributed to the formed interfacial electric field between WO3 and TiO2, which promoted efficient separation and transfer of photogenerated charge carriers. Based on the results of reactive species trapping and active radical detection, photocatalytic oxidation of NH3 over 3WO3@TiO2 was governed by the photogenerated holes and superoxide radicals. This work combines two strategies of morphological regulation and interfacial electric field construction to simultaneously improve light utilization and photogenerated charge separation efficiency, which promotes the development of full-spectrum photocatalysts for the removal of ammonia.

Fabrication of porous polyimide as cathode for high performance lithium-ion battery

Herein, we report the preparation of porous polyimide (PI) with a cost-effective synthesis process by polycondensation between melamine and dianhydride monomers. The prepared porous PI served as a cathode for lithium-ion batteries (LIBs), and delivers a high discharge platform of 2.1 V and satisfactory electrochemical performance. Thus, the porous PI cathode provides another choice for LIBs.

Regulating the kinetics of zinc-ion migration in spinel ZnMn2O4 through iron doping boosted aqueous zinc-ion storage performance

Spinel ZnMn₂O₄ with a three-dimensional channel structure is one of the important cathode materials for aqueous zinc ions batteries (AZIBs). However, like other manganese-based materials, spinel ZnMn₂O₄ also has problems such as poor conductivity, slow reaction kinetics and structural instability under long cycles. Herein, ZnMn₂O₄ mesoporous hollow microspheres with metal ion doping were prepared by a simple spray pyrolysis method and applied to the cathode of aqueous zinc ion battery. Cation doping not only introduces defects, changes the electronic structure of the material, improves its conductivity, structural stability, and reaction kinetics, but also weakens the dissolution of Mn²⁺. The optimized 0.1 % Fe-doped ZnMn₂O₄ (0.1% Fe-ZnMn₂O₄) has a capacity of 186.8 mAh g^-1 after 250 charge-discharge cycles at 0.5 A g^-1 and the discharge specific capacity reaches 121.5 mAh g^-1 after 1200 long cycles at 1.0 A g^-1. The theoretical calculation results show that doping causes the change of electronic state structure, accelerates the electron transfer rate, and improves the electrochemical performance and stability of the material.

Development of Bronze Phase Titanium Dioxide Nanorods for Use as Fast-Charging Anode Materials in Lithium-Ion Batteries

Bronze phase titanium dioxide (TiO₂(B)) nanorods were successfully prepared via a hydrothermal method together with an ion exchange process and calcination by using anatase titanium dioxide precursors in the alkali hydrothermal system. TiO₂ precursors promoted the elongation of nanorod morphology. The different hydrothermal temperatures and reaction times demonstrated that the synthesis parameters had a significant influence on phase formation and physical morphologies during the fabrication process. The effects of the synthesis conditions on the tailoring of the crystal morphology were discussed. The growth direction of the TiO₂(B) nanorods was investigated by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The as-synthesized TiO₂(B) nanorods obtained after calcination were used as anode materials and tested the efficiency of Li-ion batteries. This research will study the effects of particle morphologies and crystallinity of TiO₂(B) derived from a modified hydrothermal method on the capacity and charging rate of the Li-ion battery. The TiO₂(B) nanorods, which were synthesized by using a hydrothermal temperature of 220 °C for 12 h, presented excellent electrochemical performance with the highest Li storage capacity (348.8 mAh/g for 100 cycles at a current density of 100 mA/g) and excellent high-rate cycling capability (a specific capacity of 207.3 mAh/g for 1000 cycles at a rate of 5000 mA/g).

Low volume expansion hierarchical porous sulfur-doped Fe2O3@C with high-rate capability for superior lithium storage

Ingenious morphology design and doping engineering have remarkable effects on enhancing conductivity and reducing volume expansion, which need to be improved by transition metal oxides serving as anode materials for lithium-ion batteries. Herein, S_0.15-Fe₂O₃@C nano-spindles with a hierarchical porous structure are obtained by carbonizing MIL-88B@PDA and subsequent high-temperature S-doping. Kinetic analysis showed that S-doping increases capacitive contribution, enhances charge transfer capability and accelerates Li⁺ diffusion rate. Therefore, the S_0.15-Fe₂O₃@C electrode exhibits superior lithium storage performance with a remarkable specific capacity of 1014.4 mA h g^-1 at 200 mA g^-1, ultrahigh rate capability of 513.1 mA h g^-1 at 5.0 A g^-1, and excellent cycling stability of 842.3 mA h g^-1 at 1.0 A g^-1 after 500 cycles. Moreover, the size of S_0.15-Fe₂O₃@C particles barely changed after 50 cycles, indicating an extremely low volume expansion, related to the carbon shell, fine Fe₂O₃ nanoparticles, abundant voids inside, and improved kinetics. This strategy can be applied to other metal oxides for synthesizing anodes with high-rate capability and low volume expansion.

Phytosynthesis of Co3O4 Nanoparticles as the High Energy Storage Material of an Activated Carbon/Co3O4 Symmetric Supercapacitor Device with Excellent Cyclic Stability Based on a Na2SO4 Aqueous Electrolyte

The benign preparation of cobalt oxide nanoparticles (Co₃O₄-NPs) was performed using marine red algae extract (Grateloupia sparsa) as a simple, cost-effective, scalable, and one-pot hydrothermal technique. The nominated extract was employed as an environmental reductant and stabilizing agent. The resultant product showed the typical peak of Co₃O₄-NPs around 400 nm wavelength as ascertained by UV-vis spectroscopy. Size and morphological techniques combined with X-ray diffraction (XRD) showed the small size of Co₃O₄-NPs deformed in a spherical shape. The activated carbon (AC) electrode and Co₃O₄-NP electrode delivered a specific capacitance (C _sp) of 125 and 182 F g^-1 at 1 A g^-1, respectively. The energy density of the AC and AC/Co₃O₄ electrodes with a power density of 543.44 and 585 W kg^-1 was equal to 17.36 and 25.27 Wh kg^-1, respectively. The capacitance retention of designed electrodes was 99.2 and 99.5% after 3000 cycles. Additionally, a symmetric AC/Co₃O₄//AC/Co₃O₄ supercapacitor device had a specific capacitance (C _sp) of 125 F g^-1 and a high energy density of 55 Wh kg^-1 at a power density of 650 W kg^-1. Meanwhile, the symmetric device exhibited superior cyclic stability after 8000 cycles, with a capacitance retention of 93.75%. Overall, the adopted circular criteria, employed to use green technology to avoid noxious chemicals, make the AC/Co₃O₄ nanocomposite an easily accessible electrode for energy storage applications.

One-step side-by-side 3D printing constructing linear full batteries

A one-step side-by-side 3D printing method is proposed to construct linear lithium-, sodium-, and zinc-ion full batteries with high electrochemical performance. The inks of the battery components present shear thinning characteristics and can be printed on different substrates. This approach to design high performance linear full batteries is a general strategy.

Titanate-derived Nb-doped TiO2 nanoparticles displaying improved lithium storage performance

In the present work, a facile synthetic method has been used to prepare Nb-doped TiO₂ nanoparticles with titanate as the precursor. The synthesized electrode materials were characterized using X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, inductively coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. Furthermore, the Nb-doped TiO₂ nanoparticles were used as anode materials for lithium-ion batteries and exhibited improved lithium-ion storage properties. For instance, Nb-doped TiO₂ showed a high capacity of 134.1 mA h g^-1 at 30 C, while undoped TiO₂ exhibited a low capacity of 76.8 mA h g^-1. These improvements may be associated with enhanced conductivity due to Nb doping.

A small molecule organic compound applied as an advanced anode material for lithium-ion batteries

We choose copper(II) ions to salinize maleic acid, then form a layered copper maleate hydrate and apply this as an anode material for LIBs for the first time. The as-prepared material exhibits admirable electrochemical performance (404.6 mA h g^-1 at 0.2 A g^-1). A new hypothesis is developed for a better understanding of the unusual in situ XRD results and reaction mechanism.

Constructing an interspace in MnO@NC microspheres for superior lithium ion battery anodes

In this work, silica nanospheres were introduced into nitrogen-carbon (NC) coated MnO microspheres and filled the gap between NC and MnO. After etching, an interspace was formed between the coating layer and the MnO microspheres. The structure not only provides a conductive NC layer, but also constructs a space to mitigate the volume effect of MnO. As expected, the specific capacity remained at 1143.93 mA h g^-1 after 200 cycles at a current density of 0.2 A g^-1, and 726.96 mA h g^-1 after 450 cycles at a high current density of 1 A g^-1. The superior performance can be attributed to the unique structure with an internal void space and the excellent protection of MnO microspheres by the surface NC layer.

Co0.85Se particles encapsulated in the inner wall of nitrogen-doped carbon matrix nanotubes with rational interfacial bonds for high-performance lithium-ion batteries

Cobalt selenides based on the conversion reaction have been widely applied in lithium-ion batteries (LIBs) due to their high conductivity and high specific capacity. However, effectively suppressing the fast capacity fade caused by the irreversible Se/Co dissolution and serious volume change during the cycling process is still a challenge. Herein, a facile and efficient self-generated sacrificial template method is used to prepare Co_0.85Se nanoparticles encapsulated in the inner wall of N-doped carbon matrix nanotubes (Co_0.85Se@NCMT). In this strategy, the formation of stable Co-N/C and Se-C as well as enhancing the mechanical strength between active materials and N-doped carbon matrix nanotubes can critically affect the performance through suppressing the dissolution of Se/Co, decreasing energy band, promoting the shuttling of the ions/e^- moving and mitigating the volume expansion during the charge-discharge process, which play a key role in improving the structure stability and electrochemical performance. Besides, Co_0.85Se nanoparticles encapsulated in the robust carbon matrix inner wall can ensure good electron transfer and prevent the aggregation of nanoparticles, leading to superior electrochemical reversibility. Finally, carbon matrix nanotubes can provide sufficient space to effectively accommodate the volume changes of encapsulated Co_0.85Se nanoparticles, thereby improving the cyclic stability. Based on the above advantages, as expected, the electrochemical investigations exhibited that the Co_0.85Se@NCMT anode performs a stable reversible capacity of 462.9 mA h g^-1 at a large current density of 5 A g^-1 and a remarkable capacity retention of 99.5% after 800 cycles, suggesting its promising potential for the anode of LIBs.