Self-Templated Formation of Fluffy Graphene-Wrapped Ni5P4 Hollow Spheres for Li-Ion Battery Anodes with High Cycling Stability

Transition-metal phosphides have gained great importance in the field of energy conversion and storage such as electrochemical water splitting, fuel cells, and Li-ion batteries. In this study, a rationally designed novel fluffy graphene (FG)-wrapped monophasic Ni₅P₄ (Ni₅P₄@FG) is in-situ-synthesized using a chemical vapor deposition method as a Li-ion battery anode material. The porous and hollow structure of Ni₅P₄ core is greatly helpful for lithium-ion diffusion, and at the same time, the cilia-like graphene nanosheet shell provides an electron-conducting layer and stabilizes the solid electrolyte interface formed on the Ni₅P₄ surface. The Ni₅P₄@FG sample shows a high reversible capacity of 739 mAh g^-1 after 300 cycles at a specific current density of 500 mA g^-1. The high capacity, superior cycling stability, and improved rate capability of Ni₅P₄@FG are ascribed to its unique hierarchical structure. Moreover, the present efficient fabrication methodology of Ni₅P₄@FG has potential to be developed as a general method for the synthesis of other transition-metal phosphides.

Integrated Design of Hierarchical CoSnO3@NC@MnO@NC Nanobox as Anode Material for Enhanced Lithium Storage Performance

Transition-metal oxides (TMOs) are potential candidates for anode materials of lithium-ion batteries (LIBs) due to their high theoretical capacity (∼1000 mA h/g) and enhanced safety from suppressing the formation of lithium dendrites. However, the poor electron conductivity and the large volume expansion during lithiation/delithiation processes are still the main hurdles for the practical usage of TMOs as anode materials. In this work, the CoSnO3@NC@MnO@NC hierarchical nanobox (CNMN) is then proposed and fabricated to solve those issues. The as-prepared nanobox contains hollow cubic CoSnO3 as a core and dual N-doped carbon-"sandwiched" MnO particles as a shell. As anode materials of LIBs, the hollow and carbon interlayer structures effectively accommodate the volume expansion while dual active TMOs of CoSnO3 and MnO efficiently increase the specific capacity. Notably, the dual-layer structure of N-doped carbons plays a critical functional role in the incorporated composites, where the inner layer serves as a reaction substrate and a spatial barrier and the outer layer offers electron conductivity, enabling more effective involvement of active anode materials in lithium storage, as well as maintaining their high activity during lithium cycling. Subsequently, the as-prepared CNMN exhibits a high specific capacity of 1195 mA h/g after the 200th cycle at 0.1C and an excellent stable reversible capacity of about 876 mA h/g after the 300th cycle at 0.5C with only 0.07 mA h/g fade per cycle after 300 cycles. Even after a 250 times fast charging/discharging cycle both at 5C, it still retains a reversible capacity of 422.6 mA h/g. We ascribe the enhanced lithium storage performances to the novel hierarchical architectures achieved from the rational design.

Direct Pre-lithiation of Electropolymerized Carbon Nanotubes for Enhanced Cycling Performance of Flexible Li-Ion Micro-Batteries

Carbon nanotubes (CNT) are used as anodes for flexible Li-ion micro-batteries. However, one of the major challenges in the growth of flexible micro-batteries with CNT as the anode is their immense capacity loss and a very low initial coulombic efficiency. In this study, we report the use of a facile direct pre-lithiation to suppress high irreversible capacity of the CNT electrodes in the first cycles. Pre-lithiated polymer-coated CNT anodes displayed good rate capabilities, studied up to 30 C and delivered high capacities of 850 mAh g⁻¹ (313 μAh cm⁻²) at 1 C rate over 50 charge-discharge cycles.

Nonstoichiometric Cu0.6Ni0.4Co2O4 Nanowires as an Anode Material for High Performance Lithium Storage

Transition metal oxide is one of the most promising anode materials for lithium-ion batteries. Generally, the electrochemical property of transition metal oxides can be improved by optimizing their element components and controlling their nano-architecture. Herein, we designed nonstoichiometric Cu_0.6Ni_0.4Co₂O₄ nanowires for high performance lithium-ion storage. It is found that the specific capacity of Cu_0.6Ni_0.4Co₂O₄ nanowires remain 880 mAh g⁻¹ after 50 cycles, exhibiting much better electrochemical performance than CuCo₂O₄ and NiCo₂O₄. After experiencing a large current charge and discharge state, the discharge capacity of Cu_0.6Ni_0.4Co₂O₄ nanowires recovers to 780 mAh g⁻¹ at 50 mA g⁻¹, which is ca. 88% of the initial capacity. The high electrochemical performance of Cu_0.6Ni_0.4Co₂O₄ nanowires is related to their better electronic conductivity and synergistic effect of metals. This work may provide a new strategy for the design of multicomponent transition metal oxides as anode materials for lithium-ion batteries.

Binder-free C@NiCo2O4 on Ni foam with ultra-stable pseudocapacitive lithium ion storage

Carbon-coated nickel cobaltate on nickel foam (C@NCO@NF) with stable pseudocapacitive lithium storage capacity was prepared via a two-step strategy. NiCo hydroxide was initially grown on Ni foam via electrodeposition. Subsequent glucose soaking and annealing converted the intermediate into C@NCO@NF. Carbon coating could significantly improve the cycling stability and rate performance of the binder-free anode. The C@NCO@NF electrode could stably deliver a reversible capacity of 513 mAh · g^-1 after 500 cycles at a current density of 500 mA · g^-1. It could even stably cycle at a high current density of 5000 mA · g^-1 for 3000 cycles, with a reversible capacity of 115 mAh · g^-1. Kinetic analysis revealed that surface-controlled pseudocapacitance plays a dominant role in the lithium ion storage. Improved electrochemical performance is attributed to the synergetic effect of pseudocapacitance and carbon coating.

Solvent-Tuned Synthesis of Mesoporous Nickel Cobaltite Nanostructures and Their Catalytic Properties

In this paper, we prepared mesoporous nickel cobaltite (NiCo2O4) nanostructures with multi-morphologies by simple solvothermal and subsequent heat treatment. By adjusting the solvent type, mesoporous NiCo2O4 nanoparticles, nanorods, nanowires, and microspheres were easily prepared. The as-prepared products were systematically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) method. Furthermore, the catalytic activities towards the thermal decomposition of ammonium perchlorate (AP) of as-prepared NiCo2O4 nanostructures were investigated.

Silicon core-mesoporous shell carbon spheres as high stability lithium-ion battery anode

An innovative and simple synthesis strategy of silicon nanoparticle (Si NP) core covered by mesoporous shell carbon (MSC) structure is demonstrated. The Si core@MSC (SCMSC) composite is developed for addressing the issues for Si anode material in lithium ion batteries (LIBs) such as high volume expansion and low electrical conductivity. Significant improvement in the electrochemical performance for the SCMSC anode is observed compared with bare Si anode. The SCMSC composite delivers an initial specific capacity of 2450 mAh g^-1 at 0.166 A g^-1 with Coulombic efficiency of 99.2% for 100 cycles. Compared to bare Si anode, the SCMSC anode exhibits much higher Li storage capacity, superior cyclability, and good rate capability, highlighting the advantages of hierarchical MSC in the SCMSC structure.

Surface phosphation of 3D mesoporous NiCo2O4 nanowire arrays as bifunctional anodes for lithium and sodium ion batteries

A novel surface phosphate strategy was adopted to dramatically improve the charge transport, ion diffusion, electroactive sites, and cycle stability of mesoporous NiCo2O4 nanowire arrays (NWAs), drastically boosting their electrochemical properties. Consequently, the as-prepared phosphated NiCo2O4 NWA (P-NiCo2O4 NWA) electrode achieved excellent energy storage performance as a bifunctional anode material for both lithium ion batteries (LIBs) and sodium ion batteries (SIBs). When evaluated as an anode for LIBs, this P-NiCo2O4 NWA electrode showed a high reversible capacity up to 1156 mA h g-1 for 1500 cycles at 200 mA g-1 without appreciable capacity attenuation, while in SIBs, the electrode could also deliver an admirable initial capacity as high as 687 mA h g-1 and maintained 83.5% of this after 500 cycles at the same current density. Most important, when the current density increased from 100 to 1000 mA g-1, the capacity retention was about 63% in LIBs and 54% in SIBs. This work may shed light on the engineering of efficient electrodes for multifunctional flexible energy storage device applications.

Electrodeposited binder-free NiCo2O4@carbon nanofiber as a high performance anode for lithium ion batteries

Binder-free nickel cobaltite on a carbon nanofiber (NiCo₂O₄@CNF) anode for lithium ion batteries was prepared via a two-step procedure of electrospinning and electrodeposition. The CNF was obtained by annealing electrospun poly-acrylonitrile (PAN) in nitrogen (N₂). The NiCo₂O₄ nanostructures were then grown on the CNF by electrodeposition, followed by annealing in air. Experimental results showed that vertically aligned NiCo₂O₄ nanosheets had uniformly grown on the surface of the CNF, forming an interconnected network. The NiCo₂O₄@CNF possessed considerable lithium storage capacity and cycling stability. It exhibited a high reversible capacity of 778 mAhg^-1 after 300 cycles at a current density of 0.25 C (1 C = 890 mAg^-1) with an average capacity loss rate of 0.05% per cycle. The NiCo₂O₄@CNF had considerable rate capacities, delivering a capacity of 350 mAhg^-1 at a current density of 2.0 C. The outstanding electrochemical performance can be mainly attributed to the following: (1) The nanoscale structure of NiCo₂O₄ could not only shorten the diffusion path of lithium ions and electrons but also increase the specific surface area, providing more active sites for electrochemical reactions. (2) The CNF with considerable mechanical strength and electrical conductivity could function as an anchor for the NiCo₂O₄ nanostructure and ensure an efficient electron transfer. (3) The porous structure resulted in a high specific surface area and an effective buffer for the volume changes during the repeated charge-discharge processes. Compared with a conventional hydrothermal method, electrodeposition could significantly simplify the preparation of NiCo₂O₄, with a shorter preparation period and lower energy consumption. This work provides an alternative strategy to obtain a high performance anode for lithium ion batteries.

Mixed NiO/NiCo2O4 Nanocrystals Grown from the Skeleton of a 3D Porous Nickel Network as Efficient Electrocatalysts for Oxygen Evolution Reactions

Mixed NiO/NiCo₂O₄ nanocrystals grown in situ from the skeleton of a 3D porous nickel network (3DPNN) were prepared with a simple hydrothermal method followed by a low temperature calcination, exhibiting outstanding electrocatalytic efficiencies toward oxygen evolution reactions (OER). The 3DPNN was prepared with a novel leaven dough method and served as both the nickel source for growth of the mixed NiO/NiCo₂O₄ nanocrystals and the charge transport highway to accelerate the sluggish kinetics of the OER. The mixed NiO/NiCo₂O₄ nanocrystals exhibited pronounced synergistic effects to achieve a high mass activity of 200 A g^-1 at the catalyst mass loading of 0.5 mg cm^-2, largely outperforming the corresponding single component nanocrystal systems, NiO (5.87) and NiCo₂O₄ (9.35). The NiO/NiCo₂O₄@3DPNN composite electrocatalyst achieved a low overpotential of 264 mV at the current density of 10 mA cm^-2 and 389 mV at the practically high current density of 250 mA cm^-2, which compete favorably among the top tier of previously reported OER electrocatalysts. Moreover, it exhibited good stability even at the high current density of 250 mA cm^-2, showing only 9.40% increase in working applied potential after a continuous 12 h operation. The present work demonstrates a new design for highly efficient OER catalysts with in situ growth of mixed oxide nanocrystals of pronounced synergistic effects.

Bicontinuous Spider Network Architecture of Free-Standing MnCoO X @NCNF Anode for Li-Ion Battery

Herein, a smart strategy is proposed to tailor unique interwoven nanocable architecture consisting of MnCoO _x nanoparticles embedded in one-dimensional (1D) mesoporous N-doped carbon nanofibers (NCNFs) by using electrospinning technique. The as-prepared network mat of N-doped carbon nanofibers with embedded MnCoO _x nanoparticles (MnCoO _x @NCNFs) is tested as a current collector-free and binder-free flexible anode, which eliminates slurry preparation process during electrode fabrication in the Li-ion battery (LIB). The MnCoO _x @NCNFs possess versatile structural characteristics that can address simultaneously different issues such as poor conductivity, low cycling stability, volume variation, flexibility, and binder issue associate with the metal oxide. The free-standing mat electrode shows not only high initial discharge and charge capacities but also reversible discharge cycling stability of almost 80% retention up to 100 cycles and 60% retention up to 500 cycles at 1.0 A/g. Such high Li storage capacity and excellent cycling stability are attributed to the unique flexible and free-standing spider network-like architecture of the 1D MnCoO _x @NCNFs that provides the platform for bicontinuous electron/ion pathways for superior electrochemical performance. Along with excellent electrochemical performance, simple synthesis procedure of unique binder-free MnCoO _x @NCNFs can achieve cost-effective scalable mass production for practical use in a flexible mode, not merely in LIBs but also in a wide spectrum of energy storage fields.

Hierarchical flower-like NiCo2O4@TiO2hetero-nanosheets as anodes for lithium ion batteries

Flower-like NiCo₂O₄consisting of nanosheets are synthesized by hydrothermal technique and subsequently surface-modified with a TiO₂ultrathin layer by a hydrolysis process at low temperature.

Fabrication of Binder-Free Pencil-Trace Electrode for Lithium-Ion Battery: Simplicity and High Performance

A binder-free and solvent-free pencil-trace electrode with intercalated clay particles (mainly SiO2) is prepared via a simple pencil-drawing process on grinded Cu substrate with rough surface and evaluated as an anode material for lithium-ion battery. The pencil-trace electrode exhibits a high reversible capacity of 672 mA h g(-1) at 100 mA g(-1) after 100 cycles, which can be attributed to the unique multilayered graphene particles with lateral size of few micrometers and the formation of LixSi alloys generated by interaction between Li(+) and an active Si produced in the electrochemical reduction of nano-SiO2 in the clay particles between the multilayered graphene particles. The multilayered graphene obtained by this process consists of 1 up to 20 and occasionally up to 50 sheets and thus can not only help accommodating the volume change and alleviating the structural strain during Li ion insertion and extraction but also allow rapid access of Li ions during charge-discharge cycling. Drawing with a pencil on grinded Cu substrate is not only very simple but also cost-effective and highly scalable, easily establishing graphitic circuitry through a solvent-free and binder-free approach.