We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verifi ed by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm −2 with a high sulfur loading (4.2 mg S cm −2 ) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm −2 ) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries

We report an aqueous Zn–V2O5 battery chemistry employing commercial V2O5 cathode, Zn anode, and 3 M Zn(CF3SO3)2 electrolyte. We elucidate the Zn-storage mechanism in the V2O5 cathode to be that hydrated Zn2+ can reversibly (de)intercalate through the layered structure. The function of the co-intercalated H2O is revealed to be shielding the electrostatic interactions between Zn2+ and the host framework, accounting for the enhanced kinetics. In addition, the pristine bulk V2O5 gradually evolves into porous nanosheets upon cycling, providing more active sites for Zn2+ storage and thus rendering an initial capacity increase. As a consequence, a reversible capacity of 470 mAh g–1 at 0.2 A g–1 and a long-term cyclability with 91.1% capacity rentention over 4000 cycles at 5 A g–1 are achieved. The combination of the good battery performance, safety, scalable materials synthesis, and facile cell assembly indicates this aqueous Zn–V2O5 system is promising for stationary grid storage applications.

Rechargeable Aqueous Zn–V2O5 Battery with High Energy Density and Long Cycle Life

DOI: 10.1002/aenm.201702463 other secondary batteries.[6–8] However, LIBs are too expensive to scale up for the processing cost resulted from the limited lithium resources, and SIBs are subjected to complicated issues of safety as well as environmental issues.[9–12] So, it is an urgent challenge for exploring new energy storage systems. As an alternative, rechargeable aqueous Zn-ion batteries (ZIBs) have received incremental attention owing to the following advantages, including low cost, safety, and environmentally friendly.[13] Meanwhile, using aqueous electrolyte to replace the organic electrolyte is of great significance for reducing the cost and environmental pollution.[14] However, it is difficult to find suitable cathode material as the host for the intercalation of Zn2+ owing to the high polarization of Zn2+ as well as the narrow applicable voltage range, which is limited by the water splitting in the aqueous battery system.[15] Typically, polymorphs of MnO2 (α-, γ-phase) are highly attractive as the cathode material because of the tunnel structure suiting for the intercalation of Zn2+ and a matched potential within the stable range of water. Some results, based on the reversible intercalation of Zn2+, have been reported in recent years, and they show either limited specific capacity or poor cycling performance.[16–19] Recently, the MnO2 nanofiber electrode, reported by Liu and co-workers, shows high capacity and excellent cycling performance.[20] However, the rate performance is not high enough due to the sluggish reaction dynamics of conversion reaction. Prussian blue analogues, including of zinc hexacyanoferrate and copper hexacyanoferrate, are another class of cathode materials, which show limited specific capacity as well as poor cyclic stability.[21–23] Until very recently, vanadiumbased materials are explored for reversible Zn2+ intercalation.[24] Nazar and co-workers reported a bilayered Zn0.25V2O5·nH2O cathode, which shows a high-capacity and long-life performance.[25] However, the development of ZIBs is in the primary stage, some new cathode materials should also be explored to enhance the energy density as well as cycle life for ZIBs. Over the past decades, layered vanadium oxides have been applied as electrode materials for LIBs or SIBs due to their low cost and high capacities.[26,27] Generally, the bulk vanadium oxides suffer from a rapid capacity fading resulting from low electronic conductivity, poor structural stability during the ion de/intercalation.[28] Recent studies show that interlayer metal ions (MxVnOm, M = metal ion) can act as pillars to increase the Aqueous Zn-ion batteries (ZIBs) have received incremental attention because of their cost-effectiveness and the materials abundance. They are a promising choice for large-scale energy storage applications. However, developing suitable cathode materials for ZIBs remains a great challenge. In this work, pioneering work on the designing and construction of aqueous Zn//Na0.33V2O5 batteries is reported. The Na0.33V2O5 (NVO) electrode delivers a high capacity of 367.1 mA h g−1 at 0.1 A g−1, and exhibits long-term cyclic stability with a capacity retention over 93% for 1000 cycles. The improvement of electrical conductivity, resulting from the intercalation of sodium ions between the [V4O12]n layers, is demonstrated by single nanowire device. Furthermore, the reversible intercalation reaction mechanism is confirmed by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy analysis. The outstanding performance can be attributed to the stable layered structure and high conductivity of NVO. This work also indicates that layered structural materials show great potential as the cathode of ZIBs, and the indigenous ions can act as pillars to stabilize the layered structure, thereby ensuring an enhanced cycling stability. Zinc Ion Batteries

Sodium Ion Stabilized Vanadium Oxide Nanowire Cathode for High-Performance Zinc-Ion Batteries

The development of advanced energy storage devices is at the forefront of research geared towards a sustainable future. Nanostructured materials are advantageous in offering huge surface to volume ratios, favorable transport features, and attractive physicochemical properties. They have been extensively explored in various fields of energy storage and conversion. This review is focused largely on the recent progress in nanostructured Mo-based electrode materials including molybdenum oxides (MoOx, 2 ≤ x ≤ 3), dichalconides (MoX2, X = S, Se), and oxysalts for rechargeable lithium/sodium-ion batteries, Mg batteries, and supercapacitors. Mo-based compounds including MoO2, MoO3, MoO3−y (0 < y < 1), MMoxOy (M = Fe, Co, Ni, Ca, Mn, Zn, Mg, or Cd; x = 1, y = 4; x = 3, y = 8), MoS2, MoSe2, (MoO2)2P2O7, LiMoO2, Li2MoO3, etc. possess multiple valence states and exhibit rich chemistry. They are very attractive candidates for efficient electrochemical energy storage systems because of their unique physicochemical properties, such as conductivity, mechanical and thermal stability, and cyclability. In this review, we aim to provide a systematic summary of the synthesis, modification, and electrochemical performance of nanostructured Mo-based compounds, as well as their energy storage applications in lithium/sodium-ion batteries, Mg batteries, and pseudocapacitors. The relationship between nanoarchitectures and electrochemical performances as well as the related charge-storage mechanism is discussed. Moreover, remarks on the challenges and perspectives of Mo-containing compounds for further development in electrochemical energy storage applications are proposed. This review sheds light on the sustainable development of advanced rechargeable batteries and supercapacitors with nanostructured Mo-based electrode materials.

Nanostructured Mo-based electrode materials for electrochemical energy storage

http://depts.washington.edu/solgel/documents/pub_docs/journal_docs/2015/shuquan_2015.pdf

Template-free synthesis of ultra-large V2O5 nanosheets with exceptional small thickness for high-performance lithium-ion batteries

An efficient and scalable strategy has been developed for the synthesis of MoS2 nanosheets employing PVP as a surfactant. The MoS2 nanosheets exhibit an enhanced lithium intercalation capacity, cyclic stability and rate capability.

PVP-assisted synthesis of MoS2 nanosheets with improved lithium storage properties

The lack of high-performance cathode materials is a great challenge for the development of large-scale energy storage sodium ion batteries. Here, a new resource-rich P2-type Na0.44Mn0.6Ni0.4−xCuxO2 (0 ≤ x ≤ 0.3) sodium-ion battery (NIBs) cathode material was designed and synthesized by a sol–gel method. Na ions occupy the Naf sites and the Nae sites in a proportion of 1 : 1, which maintains the high symmetry and stability of the P2-type structure. The charging/discharging tests show that Na0.44Mn0.6Ni0.3Cu0.1O2 has a high initial capacity of 149 mA h g−1 and 80% capacity retention after 50 cycles at 0.1C, showing a high energy density of 469 W h kg−1. The addition of inactive copper enhances the lattice spacing, obviously reducing the irreversible reaction resistance (Rf) during the intercalation and deintercalation of Na+, thereby reducing the internal resistance of the battery and improving the cycle performance. In order to maintain the P2-type structure, the voltage is controlled at 1.5–4.0 V during charging and discharging, which inhibits the phase transition of P2-O2, leading to the improvement of cycling performance. Therefore, the Cu-substituted Na0.44Mn0.6Ni0.3Cu0.1O2 possibly serves as a promising high capacity, high energy density and stable cathode for sodium ion battery applications.

Tao Chen

Papers

Template-free synthesis of ultra-large V2O5 nanosheets with exceptional small thickness for high-performance lithium-ion batteries

PVP-assisted synthesis of MoS2 nanosheets with improved lithium storage properties

A P2-type Na0.44Mn0.6Ni0.3Cu0.1O2 cathode material with high energy density for sodium-ion batteries

Facile synthesis of Ag/AgVO3 hybrid nanorods with enhanced electrochemical performance as cathode material for lithium batteries

Studies on electrochemical reversibility of lithium tungstate coated Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode material under high cut-off voltage cycling