Effect of Ni content in Ni Mn1-CO3 (x = 0, 0.20, 0.25, 0.33) submicrospheres on the performances of rechargeable lithium ion batteries

The direct growth of Mn0.6Ni0.4CO3 nanosheet assemblies on Ni foam for high-performance supercapacitor electrodes

Mn0.6Ni0.4CO3 nanosheet assemblies have better electrochemical properties than previously reported MnCO3, mainly because of the doping and foamed nickel substrate.

Surfacing amorphous Ni-B nanoflakes on NiCo2O4 nanospheres as multifunctional bridges for promoting lithium storage behaviors

Transition metal oxides (TMOs) have gained enormous research interests as negative materials of next generation lithium-ion batteries due to their higher energy density, lower cost, and better eco-friendliness. However, they are prone to low electronic conductivities and dramatic volume change during charge/discharge and there is also a great challenge in realizing TMO electrodes with satisfactory LIB performances. In this study, for the first time, amorphous nickel-boride (Ni-B) was introduced into porous NiCo2O4 nanospheres by an in situ solution growth route to overcome the existing issues. The coated Ni-B component could not only function as anchors for NiCo2O4 nanospheres to suppress the severe volume expansion but could also act as effective electron-conducting bridges to promote fast electron/charge transfer. Furthermore, the existence of abundant mesopores centered at ∼6.5 nm in this composite could effectively suppress the severe volume variations in the lithiation/delithiation process. As expected, the NiCo2O4@Ni-B composites delivered a high reversible capacity of 1221 mA h g-1 at 0.2 A g-1 and 865 mA h g-1 at 0.5 A g-1 over 500 cycles; more impressively, at the high rate of 5 A g-1, a capacity of 648 mA h g-1 could be also obtained, showing its good rate capability. As a result, these results demonstrated an effective and facile way to design conversion-type negative electrode materials with superior lithium storage properties.

Co0.8Zn0.2MoO4/C Nanosheet Composite: Rational Construction via a One-Stone-Three-Birds Strategy and Superior Lithium Storage Performances for Lithium-Ion Batteries

CoMoO₄ has gained great attention as an anode material for lithium-ion batteries owing to its high theoretical capacity of 980 mAh g^-1 and relatively high electrochemical activity. Unfortunately, CoMoO₄ anode also has some drawbacks such as low electronic/ionic conductivity, inferior cyclic stability, and relative severe volumetric expansion during the lithiation/delithiation process, greatly inhibiting its further development and application. Herein, we report Co_0.8Zn_0.2MoO₄/C nanosheet composite constructed via a novel and facile one-stone-three-birds strategy. The preparation of the Co_0.8Zn_0.2MoO₄/C nanosheet is based on the following two-step process: the formation of Co/Zn nanosheet precursors derived from Co/Zn-ZIF rhombic dodecahedra via solvothermal pretreatment, followed by a calcination treatment with molybdic acid (H₂MoO₄) in air. The as-prepared Co_0.8Zn_0.2MoO₄/C is monoclinic crystal structured composite with the in situ formed active carbon, which is well-defined nanosheet with a rough surface and mean thickness of 60-70 nm for a single sheet. This Co_0.8Zn_0.2MoO₄/C nanosheet composite possesses a larger surface area of 37.60 m² g^-1, showing a mesoporous structure. When used as anode materials, the as-obtained Co_0.8Zn_0.2MoO₄/C composite can deliver as high as a discharge capacity of 1337 mAh g^-1 after 300 cycles at 0.2C and still retain the capacity of 827 mAh g^-1 even after 600 cycles at 1C, exhibiting outstanding lithium storage performances. The higher capacity and superior cyclic stability of the Co_0.8Zn_0.2MoO₄/C composite should be ascribed to the synergistic effect of the substitution of Zn²⁺, in situ composited active carbon and the as-constructed unique microstructure for the Co_0.8Zn_0.2MoO₄/C composite. Our present work provides a facile one-stone-three-birds strategy to effectively construct the architectures and significantly enhance electrochemical performances for other transition metal electrode materials.

Construction of Mn-Zn binary carbonate microspheres on interconnected rGO networks: creating an atomic-scale bimetallic synergy for enhancing lithium storage properties

Transition metal carbonates (TMCs), as promising anode materials for high-performance lithium ion batteries, possess the advantages of abundant natural resources and high electrochemical activity; however, they suffer from poor Li+/e- conductivities and serious volume changes during the charge/discharge process. Constructing multicomponent carbonates by introducing binary metal atoms, as well as designing a robust structure at the micro and nanoscales, could efficiently address the above problems. Therefore, single-phase MnxZn1-xCO3 microspheres anchored on 3D conductive networks of reduced graphene oxide (rGO) are facilely synthesized via a one-pot hydrothermal method without any structure-directing agents or surfactants. Due to the well-designed architecture and atomic-scale bimetallic synergy, the MnxZn1-xCO3/rGO composites show superior lithium storage capacity, good rate capability and ultra-long cycling performance. Specifically, the Mn2/3Zn1/3CO3/rGO composites could deliver a high capacity of 1073 mA h g-1 at 200 mA g-1. After 1700 cycles at a high rate of 2000 mA g-1, a stable capacity of 550 mA h g-1 can be maintained with the capacity retention approaching 88.6%. Density functional theory (DFT) calculations indicate that the partial Zn substitution in MnCO3 could significantly decrease the band gap of the crystal, resulting in great improvement of electric conductivity. Moreover, the commercial potential of the MnxZn1-xCO3/rGO composites is investigated by assembling full cells, suggesting good practical adaptability of the composite anodes. This work would provide a feasible and cost-efficient method to develop high-performance anodes and stimulate many more related research studies on TMC-based electrodes.

Engineering Na-Mo-O/Graphene Oxide Composites with Enhanced Electrochemical Performance for Lithium Ion Batteries

Sodium molybdate (Na−Mo−O) wrapped by graphene oxide (GO) composites have been prepared via a simple in‐situ precipitation method at room temperature. The composites are mainly constructed with one dimension (1D) ultra‐long sodium molybdate nanorods, which are wrapped by the flexible GO. The introduction of GO is expected to not merely provide more active sites for lithium‐ions storage, but also improve the charge transfer rate of the electrode. The testing electrochemical performances corroborated the standpoint: The Na−Mo−O/GO composites delivers specific capacities of 718 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹, and 570 mAh g⁻¹ after 500 cycles at a high rate of 500 mA g⁻¹; for comparison, the bare Na−Mo−O nanorod shows a severe capacity decay, which deliver only 332 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹. In view of the cost‐efficient and less time‐consuming in synthesis, and one‐step preparation without further treatment, these Na−Mo−O nanorods/GO composites present potential and prospective anodes for LIBs.