Bao-Hua Hou

Constructing the optimal conductive network in MnO-based nanohybrids as high-rate and long-life anode materials for lithium-ion batteries

Among the transition metal oxides as anode materials for lithium ion batteries (LIBs), the MnO material should be the most promising one due to its many merits mainly relatively low voltage hysteresis. However, it still suffers from inferior rate capabilities and poor cycle life arising from kinetic limitations, drastic volume changes and severe agglomeration of active MnO particulates during cycling. In this paper, by integrating the typical strategies of improving the electrochemical properties of transition metal oxides, we had rationally designed and successfully prepared one superior MnO-based nanohybrid (MnO@C/RGO), in which carbon-coated MnO nanoparticles (MnO@C NPs) were electrically connected by three-dimensional conductive networks composed of flexible graphene nanosheets. Electrochemical tests demonstrated that, the MnO@C/RGO nanohybrid not only showed the best Li storage performance in comparison with the commercial MnO material, MnO@C NPs and carbon nanotube enhanced MnO@C NPs, but also exhibited much improved electrochemical properties compared with most of the previously reported MnO-based materials. The superior electrochemical properties of the MnO@C/RGO nanohybrid included a high specific capacity (up to 847 mA h g−1 at 80 mA g−1), excellent high-rate capabilities (for example, delivering 451 mA h g−1 at a very high current density of 7.6 A g−1) and long cycle life (800 cycles without capacity decay). More importantly, for the first time, we had achieved the discharging/charging of MnO-based materials without capacity increase even after 500 cycles by adjusting the voltage range, making the MnO@C/RGO nanohybrid more possible to be a really practical anode material for LIBs.

Porous N-doped carbon material derived from prolific chitosan biomass as a high-performance electrode for energy storage

Although a wide variety of biomass, such as human hair, chicken eggshells and ox horns, have been used to prepare carbon electrode materials for energy storage, most of them have very limited production, which restricts their large-scale application. Herein, the very prolific biomass of chitosan is employed as an abundant raw material to successfully prepare one porous N-doped carbon material (PNCM). Structural characterizations demonstrate that this PNCM is hierarchically porous with abundant macro/micropores and 4.19% N-doping. The electrochemical properties of the PNCM as electrode materials for both supercapacitors and lithium ion batteries are also studied. When used in a supercapacitor, the optimized PNCM synthesized at 700 °C can store electrical energy with a specific capacitance of up to 220 F g−1 in 1 mol L−1 H2SO4 electrolyte, exhibit excellent cycle stability with only 1.3% capacitance decay over 11 000 cycles, and deliver high power and energy densities in both aqueous and organic electrolytes. In addition to supercapacitors, the PNCM also exhibits excellent Li-storage properties in terms of high specific capacity (above 460 mA h g−1 at 50 mA g−1) and superior cycle stability (without any capacity decay even after 1100 cycles) when used as an anode material for lithium ion batteries.

A Scalable Strategy To Develop Advanced Anode for Sodium-Ion Batteries: Commercial Fe3O4-Derived Fe3O4@FeS with Superior Full-Cell Performance

A novel core-shell Fe3O4@FeS composed of Fe3O4 core and FeS shell with the morphology of regular octahedra has been prepared via a facile and scalable strategy via employing commercial Fe3O4 as the precursor. When used as anode material for sodium-ion batteries (SIBs), the prepared Fe3O4@FeS combines the merits of FeS and Fe3O4 with high Na-storage capacity and superior cycling stability, respectively. The optimized Fe3O4@FeS electrode shows ultralong cycle life and outstanding rate capability. For instance, it remains a capacity retention of 90.8% with a reversible capacity of 169 mAh g-1 after 750 cycles at 0.2 A g-1 and 151 mAh g-1 at a high current density of 2 A g-1, which is about 7.5 times in comparison to the Na-storage capacity of commercial Fe3O4. More importantly, the prepared Fe3O4@FeS also exhibits excellent full-cell performance. The assembled Fe3O4@FeS//Na3V2(PO4)2O2F sodium-ion full battery gives a reversible capacity of 157 mAh g-1 after 50 cycles at 0.5 A g-1 with a capacity retention of 92.3% and the Coulombic efficiency of around 100%, demonstrating its applicability for sodium-ion full batteries as a promising anode. Furthermore, it is also disclosed that such superior electrochemical properties can be attributed to the pseudocapacitive behavior of FeS shell as demonstrated by the kinetics studies as well as the core-shell structure. In view of the large-scale availability of commercial precursor and ease of preparation, this study provide a scalable strategy to develop advanced anode materials for SIBs.

Multiple heterointerfaces boosted de-/sodiation kinetics towards superior Na storage and Na-Ion full battery

In this article, an effective strategy (viz., constructing multiple heterointerfaces) is proposed to develop superior electrode materials for sodium-ion battery (SIB), which is the most promising alternative to market-dominant lithium-ion battery for stationary energy storage. In the as-prepared heterogeneous-SnO2/Se/graphene (h-SSG) composite, there exists multiple phase interfaces, including heterointerfaces between tetragonal and orthorhombic SnO2 (t-/o-SnO2) in the heterogeneous SnO2 nanojunctions and two phase interfaces between t/o-SnO2 and amorphous Se. These multiple phase interfaces promise the much improved Na storage properties of h-SSG when compared to four controls without such multiple heterointerfaces because the multiple built-in electric fields at the heterointerfaces can significantly boost the surface reaction kinetics and facilitate charge transport as demonstrated by kinetics analyses, theoretical calculations and contrastive electrochemical tests. Moreover, h-SSG also exhibits superior Na-ion full cell performance when coupled with a high-voltage Na3V2(PO4)2O2F cathode. In view of the universality of the heterointerface-based enhancement effect on surface reaction and charge transport kinetics and the facile preparation procedures, the present strategy should be universal to develop other superior electrode materials for high-performance SIBs and other batteries for future energy storage applications.

Ni1.5CoSe5 Nanocubes Embedded in 3D Dual N-Doped Carbon Network as Advanced Anode Material in Sodium-Ion Full Cells with Superior Low-Temperature and High-Power Properties

In this study, the double transition metal selenide Ni1.5CoSe5 with cube-like nanoaggregate morphology was successfully embedded into a three-dimensional (3D) dual N-doped carbon network, developing an advanced anode material for sodium-ion batteries (SIBs). In the prepared composite, Ni1.5CoSe5 nanoparticles were first coated by N-doped carbon (NC), which further aggregated to form nanocubes, and finally embedded into interconnected N-doped reduced graphene oxide (rGO) nanosheets; hence, the material was abbreviated as Ni1.5CoSe5@NC@rGO. It delivered a reversible Na-storage capacity of 582.5 mA h g−1 at a low current density of 0.05 A g−1 and exhibited ultra-fast rate properties (e.g., with the specific capacities of 180.8 and 96.3 mA h g−1 at high current densities of 30 and 50 A g−1, respectively). The much enhanced Na-storage properties were ascribed to the highly conductive 3D network constructed by dual N-doped carbonaceous materials, which acted not only as a highway for ultrafast charge transfer but also as an effective protector for the active Ni1.5CoSe5 material and cube-like nanoaggregates with nanometer-sized primary particles. More significantly, the Ni1.5CoSe5@NC@rGO electrode also exhibited superior energy storage performance in sodium-ion full cells when coupled with a high-voltage Na3V2(PO4)2O2F cathode, making it a promising anode material for practical SIBs.

Hierarchical GeP5/Carbon Nanocomposite with Dual-Carbon Conductive Network as Promising Anode Material for Sodium-Ion Batteries

Due to the Earths scarcity of lithium, replacing lithium with earth-abundant and low-cost sodium for sodium-ion batteries (SIBs) has recently become a promising substitute for lithium-ion batteries. However, the shortage of appropriate anode materials limits the development of SIBs. Here, a dual-carbon conductive network enhanced GeP5 (GeP5/acetylene black/partially reduced graphene oxide sheets (GeP5/AB/p-rGO)) composite is successfully prepared by a facile ball milling method. The dual-carbon network not only provides more transport pathways for electrons but also relaxes the huge volume change of the electrode material during the charge/discharge process. Compared with only AB- or GO-modified GeP5 (GeP5/AB or GeP5/GO) composite, the GeP5/AB/p-rGO composite shows a superior sodium storage performance with an excellent rate and cycle performance. It delivers a high reversible capacity of 597.5 and 175 mAh/g at the current density of 0.1 and 5.0 A/g, respectively. Furthermore, at the current density of 0.5 A/g, the GeP5/AB/p-rGO composite shows the reversible capacity of 400 mAh/g after 50 cycles with a little capacity attenuation. All above results prove that the GeP5/AB/p-rGO composite has a good prospect of application as an anode material for SIBs.