Facile synthesis of spongy NiCo2O4 powders for lithium-ion storage

Spongy NiCo₂O₄ powders were prepared by solution combustion synthesis (SCS) method for lithium ions storage. The effects of combustion parameters including fuel type (L-lysine, glycine, and urea) and fuel amount on the lithium storage performance of NiCo₂O₄ powders were analyzed by various characterization techniques. Single-phase NiCo₂O₄ powders with extremely porous microstructure showed a strong drop of initial specific capacity up to 350 mAhg^-1 which was recovered up to 666 mAhg^-1 following 100 charge/discharge cycles. However, the NiCo₂O₄ powders prepared by the urea and L-lysine fuels with the compacted microstructure showed the capacity loss without any recovery. The spongy NiCo₂O₄ powders showed an acceptable capability rate performance (404 mAhg^-1 @ 400 mAg^-1).

Superstructure MOF as a framework to composite MoS2 with rGO for Li/Na-ion battery storage with high-performance and stability

Metal sulfides, one kind of electrode material with very high theoretical capacity, have been widely studied for use in lithium and sodium ion batteries. However, there are some problems hindering their applications in electrodes, such as low conductivity and volume expansion. The MOF introduces metals with different coordination strengths into an existing MOF structure, which improves the performance of the electrode to a certain extent. In this paper, Fe/Zn bimetallic MOF rod-like superstructure was prepared based on Ostwald theory. Accompanied by sulfuration, the MOF was effectively combined with MoS₂ and GO, and the objective materials Fe₇S₈-C/ZnS-C@MoS₂/rGO composites were successfully prepared. The MOF material provides a good frame and an efficient electron transport path, while the robust rGO wall effectively inhibits the pulverization of materials during the lithium/sodium intercalation/escalation courses. This particular material exhibited excellent cycling and rate capability performance when used in Li/Na-ion batteries. When used in Li-batteries, the electrode material delivered a specific capacity of 1598.3 mA h g^-1 at 0.1 A g^-1 and remained at 1196.7 mA h g^-1 even after about 100 cycles and further exhibited a specific capacity of 368.68 mA h g^-1 at the current rate of 5 A g^-1 even after 1000 cycles, respectively. As for sodium batteries, these electrode materials exhibited an initial reversible capacity of 1053.6 mA h g^-1 at 0.1 A g^-1 and the reversible capacity was still as high as 592.2 mA h g^-1 after 200 cycles. It is perhaps that this composite material with its particular architecture and composition is greatly beneficial for electron transfer and Li/Na ion diffusion. In the repeated physicochemical/nutrifying process, the appropriate distance between adjacent MOFs is of great help in preventing volume changes and thus improving the electrochemical performance.

Synthesis of Porous Ni-Doped CoSe2 /C Nanospheres towards High-Rate and Long-Term Sodium-Ion Half/Full Batteries

Carbon-layer-coated porous Ni-doped CoSe₂ (Ni-CoSe₂ /C) nanospheres have been fabricated by a facile hydrothermal method followed by a new selenization strategy. The porous structure of Ni-CoSe₂ /C is formed by the aggregation of many small particles (20-40 nm), which are not tightly packed together, but are interspersed with gaps. Moreover, the surfaces of these small particles are covered with a thin carbon layer. Ni-CoSe₂ /C delivers superior rate performance (314.0 mA h g^-1 at 20 A g^-1 ), ultra-long cycle life (316.1 mA h g^-1 at 10 A g^-1 after 8000 cycles), and excellent full-cell performance (208.3 mA h g^-1 at 0.5 A g^-1 after 70 cycles) when used as an anode material for half/full sodium-ion batteries. The Na storage mechanism and kinetics have been confirmed by ex situ X-ray diffraction analysis, assessment of capacitance performance, and a galvanostatic intermittent titration technique (GITT). GITT shows that Na⁺ diffusion in the electrode material is a dynamic change process, which is associated with a phase transition during charge and discharge. The excellent electrochemical performance suggests that the porous Ni-CoSe₂ /C nanospheres have great potential to serve as an electrode material for sodium-ion batteries.

Nearly monodispersed MoS2 hierarchical architectures as superior anodes for electrochemical lithium-storage

In this paper, we developed a facile approach to synthesize well-dispersed 3D hierarchical porous MoS₂ architectures with assistance of polyacrylate and demonstrated their applications in lithium ion batteries (LIBs). It was confirmed that the uniform flower-like MoS₂ architectures were assembled by nanosheets comprising about ∼10 stacking layers. Polyacrylate was revealed to have a significant impact on controlling the formation of the uniform hierarchical flower-like architectures with desirable dispersity. It was believed that the polyacrylate could direct assembly of the MoS₂ nanosheets into hierarchical structures and could well stabilize and disperse MoS₂ architectures. Furthermore, a stable cycling capability (839 mAh g^-1 at 0.1 A g^-1 after 120 cycles) and superior rate ability of the MoS₂ architectures were achieved as anodes for LIBs. This remarkably enhanced electrochemical property could be ascribed to their beneficial structural features and surface-dominated capacitive contribution.

Electrochemical exploration of the effects of calcination temperature of a mesoporous zinc vanadate anode material on the performance of Na-ion batteries

As transition metal oxides are attractive candidates for energy storage applications, the spinel-structure of mesoporous ZnV₂O₄ as a potential novel anode for Na-ion storage and the synergetic effects of calcination temperature were studied.

Rational design of NiFe2O4–rGO by tuning the compositional chemistry and its enhanced performance for a Li-ion battery anode

NiFe₂O₄–rGO is reasonably designed; meanwhile, the excellent lithium storage can be readily tuned by tuning the compositional chemistry.

Preparation of mesoporous CoNiO2 hexagonal nanoparticles for asymmetric supercapacitors via a hydrothermal microwave carbon bath process

Mesoporous CoNiO₂ hexagonal nanoparticles prepared via a hydrothermal microwave carbon bath process instead of the conventional calcination method have excellent pseudocapacitance properties.

FeS2 nanosheets encapsulated in 3D porous carbon spheres for excellent Na storage in sodium-ion batteries

FeS₂ nanosheets encapsulated in porous carbon layers were prepared by a facile method, which exhibited excellent performance of Na storage.

Rice-shaped porous ZnMn2O4 microparticles as advanced anode materials for lithium-ion batteries

Novel rice-shaped porous ZnMn₂O₄ microparticles made of nanoparticles were prepared by the calcination of Zn_0.33Mn_0.67CO₃ precursors synthesized using a facile triethanolamine-assisted solvothermal method.

NiCo2O4/MnO2 core/shell arrays as a binder-free catalytic cathode for high-performance lithium–oxygen cells

Li–O₂ cells with the porous core–shell MnO₂@NiCo₂O₄ array-type catalytic cathode exhibit a long cycle life.