Minxia Li

Co3O4@MWCNT Nanocable as Cathode with Superior Electrochemical Performance for Supercapacitors

Using a simple hydrothermal procedure, cobalt oxide (Co3O4) with preferred orientation along (220) planes is in situ prepared and coated on MWCNT. The prepared Co3O4@MWCNT nanocable shows superior electrochemical performance as cathode material for aqueous supercapacitors in 0.5 M KOH solution. Its redox peaks retain the well-defined shapes even when the scan rate increases to 200 mV/s. Its specific capacitance is high, 590 F/g at 15 A/g and 510 F/g even at 100 A/g within the potential range from -0.2 to 0.58 V (vs SCE). There is no capacitance fading after 2000 full cycles. This excellent performance is superior to the pristine and the reported Co3O4, which is ascribed to the unique nanocable structure with orientation.

An Aqueous Rechargeable Zn//Co3O4 Battery with High Energy Density and Good Cycling Behavior

An aqueous rechargeable Zn//Co3 O4 battery is demonstrated with Zn@carbon fibers and Co3 O4 @Ni foam as the negative and positive electrodes, respectively, using an electrolyte of 1 m KOH and 10 × 10(-3) m Zn(Ac)2 . It can operate at a cell voltage as high as 1.78 V with an energy density of 241 W h kg(-1) and presents excellent cycling. The battery is also assembled into a flexible shape, which can be applied in flexible or wearable devices requiring high energy.

Green energy storage chemistries based on neutral aqueous electrolytes

Widespread use of fossil fuels has resulted in many environmental problems. There is an urgent need to search for reliable green energy storage technologies. The electrical energy storage systems based on neutral aqueous solutions are attractive candidates compared to the present energy storage systems utilizing flammable and expensive organic electrolytes because of their improved safety, low cost and environmental friendliness. What is more, high-rate performance can be achieved due to the high ionic conductivity of the aqueous electrolytes. However, the lower electrochemical window of water limits the possible high output voltage and high energy density. Recently, many new concepts based on neutral aqueous energy storage chemistries including aqueous rechargeable batteries and supercapacitors have exhibited high power and energy densities, excellent cycling life and high Coulombic efficiency. The present paper reviews the latest advances in these new chemistries based on neutral aqueous electrolytes, and the challenges and outlooks in this field are briefly commented on and discussed.

A Se/C composite as cathode material for rechargeable lithium batteries with good electrochemical performance

A Se/C composite was prepared by a simple combination method of ball milling and low temperature treatment as a cathode material for Li–Se rechargeable batteries. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Its electrochemical performance as a cathode material for lithium rechargeable batteries was tested by cyclic voltammetry (CV) and capacity measurements. Rate capacity and cycling performance of the as-prepared product are very satisfactory. Even at a current density of 500 mA g−1, the composite can deliver a capacity of 187 mA h g−1. The main reason is that the high conductivity of carbon decreases its charge transfer resistance and effectively suppresses the dissolution of oxidation products from the composite cathode.

A Zn–NiO rechargeable battery with long lifespan and high energy density

A Zn–NiO rechargeable battery comprising a NiO nanosheet anchored to CNTs as the positive electrode, a zinc plate as the negative one and an alkaline solution of 1 M KOH and 10 mM Zn(Ac)2 as the electrolyte is reported. It delivers a voltage of ∼1.75 V and a high energy density of 228 W h kg−1 (based on the mass of the positive electrode composite and zinc) with good cycling. It has great promise for practical energy storage applications.

Rechargeable Li//Br battery: a promising platform for post lithium ion batteries

A rechargeable lithium battery, Li//Br, is reported using an aqueous bromide/tribromide redox pair and a coated lithium metal as the positive and negative electrodes, respectively. The positive Br2 electrode shows fast redox kinetics and good stability. This battery presents excellent electrochemical performance with an average discharge voltage up to 3.96 V at 1.7 mA cm−2, an energy density of 1220 Wh kg−1, a power density of 29.7 mW cm−2 at a current density of 12.8 mA cm−2, and a long cycling life. There is no evidence of voltage decrease after 100 cycles at 35% DOD. It would become a good platform between lithium ion batteries and Li//air batteries since the former shows lower energy density and the latter has some challenging problems that need to be solved prior to practical application. This finding presents another promising choice for electrochemical energy storage systems.

Hybrid system for rechargeable magnesium battery with high energy density

One of the main challenges of electrical energy storage (EES) is the development of environmentally friendly battery systems with high safety and high energy density. Rechargeable Mg batteries have been long considered as one highly promising system due to the use of low cost and dendrite-free magnesium metal. The bottleneck for traditional Mg batteries is to achieve high energy density since their output voltage is below 2.0 V. Here, we report a magnesium battery using Mg in Grignard reagent-based electrolyte as the negative electrode, a lithium intercalation compound in aqueous solution as the positive electrode, and a solid electrolyte as a separator. Its average discharge voltage is 2.1 V with stable discharge platform and good cycling life. The calculated energy density based on the two electrodes is high. These findings open another door to rechargeable magnesium batteries.

A gel polymer electrolyte based on composite of nonwoven fabric and methyl cellulose with good performance for lithium ion batteries

A new composite gel polymer electrolyte of nonwoven fabric (NWF) and methyl cellulose (MC) with good mechanical properties and outstanding thermal and electrochemical stability is prepared by a simple and green casting process followed by absorbing liquid electrolyte. Its characteristics are investigated by scanning electron microscopy, FT-IR, thermogravimetric analysis (TGA). Due to the synergistic action between MC matrix and the NWF framework, the composite gel polymer electrolyte achieves higher ionic conductivity (0.29 mS cm−1) at ambient temperature and larger lithium ion transference number (0.34) than those for the conventional Celgard 2730 separator (0.21 mS cm−1 and 0.27, respectively) in 1 mol L−1 LiPF6 electrolyte, and their activation energies are similar. In addition, the composite membrane shows better mechanical strength than the pure MC membrane. The evaporation rate of the liquid electrolyte at elevated temperature is much decreased. The assembled Li//LiFePO4 cell using this composite gel membrane exhibits better cycling retention and higher discharge capacity than those based on Celgard 2730 separator and pure MC gel membrane. These fascinating characteristics suggest that this unique composite gel polymer electrolyte can be used for lithium ion batteries with good performance and low cost.

Enhanced capacitive desalination of MnO2 by forming composite with multi-walled carbon nanotubes

The morphology and structure of the prepared MnO2/MWCNTs (multi-walled carbon nanotubes) composite are characterized by XRD, SEM, TEM, and N2 sorption analysis. The electrochemical performance of the composite is studied by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge evaluation. The composite has a specific capacitance of 144 F g−1 at the current density of 1 A g−1. It has higher conductivity which is affirmed by electrochemical impedance spectroscopy (EIS). The capacitive deionization (CDI) test was conducted in a bath mode apparatus by assembling a capacitor. The capacitor made from MnO2/MWCNTs composite shows a higher desalination capacity of (6.65 mg g−1) in NaCl aqueous solution, higher than that made from the virginal MnO2 (1.60 mg g−1) and those of the formerly reported. Furthermore, the MnO2/MWCNTs composite electrode shows excellent recyclability with an efficient and rapid regeneration process.

Atmospheric growth and strong visible luminescence of anatase titanium oxide films with various orientations

At atmospheric pressure, anatase TiO2 films with various nano-morphologies have been grown on quartz substrate by non-thermal TiCl4–O2–Ar reactive plasma vapor deposition. High concentration of oxygen vacancies and undercoordinated Ti atoms are incorporated into the crystal lattice of the deposited films, which can be tuned by changing the discharge conditions such as temperature and vapor flow rate. Strong visible luminescence is found for the deposited films, originating from the radiative recombination of trapped electrons due to uncoordinated Ti atoms and oxygen vacancies. To clarify the growth mechanism, an analytical model is proposed to explain the corresponding discharging process. We find the theoretical predictions agree well with experimental results. By effectively adjusting the morphology and lattice crystallinity, we believe this work can provide an expedient and controllable way to fabricate anatase films with interesting optical properties, which can meet the demands of complex practical situations to the maximum degree.