Yaqiong Yang

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.

A trilayer poly(vinylidene fluoride)/polyborate/poly(vinylidene fluoride) gel polymer electrolyte with good performance for lithium ion batteries

A composite membrane based on poly(vinylidene fluoride) (PVDF) and lithium polyacrylic acid oxalate borate (LiPAAOB) exhibiting high safety (self-extinguishing) and good mechanical property was prepared. The ionic conductivity of the gel polymer electrolyte (GPE) by saturating with 1 mol L−1 LiPF6 electrolyte at ambient temperature can be up to 0.35 mS cm−1, higher than that of the well-used commercial separator (Celgard 2730), 0.21 mS cm−1. The lithium ion transference in the GPE at room temperature is 0.58, twice that in the commercial separator (0.27). Moreover, the GPE presents a true shut-down behavior, which is quite different from the not-real shut-down behaviour of the commercial separators. Furthermore, the absorbed electrolyte solvent is difficult to evaporate at elevated temperature. Its electrochemical performance is evaluated by using LiFePO4 cathode. The obtained results suggest that this composite GPE is very attractive to large-capacity battery systems requiring high safety and low cost.

Cheap glass fiber mats as a matrix of gel polymer electrolytes for lithium ion batteries

Lithium ion batteries (LIBs) are going to play more important roles in electric vehicles and smart grids. The safety of the current LIBs of large capacity has been remaining a challenge due to the existence of large amounts of organic liquid electrolytes. Gel polymer electrolytes (GPEs) have been tried to replace the organic electrolyte to improve their safety. However, the application of GPEs is handicapped by their poor mechanical strength and high cost. Here, we report an economic gel-type composite membrane with high safety and good mechanical strength based on glass fiber mats, which are separator for lead-acid batteries. The gelled membrane exhibits high ionic conductivity (1.13 mS cm−1), high Li+ ion transference number (0.56) and wide electrochemical window. Its electrochemical performance is evaluated by LiFePO4 cathode with good cycling. The results show this gel-type composite membrane has great attraction to the large-capacity LIBs requiring high safety with low cost.

An environmentally friendly and economic membrane based on cellulose as a gel polymer electrolyte for lithium ion batteries

A green and environmentally friendly polymer, methyl cellulose (MC), is used as a host matrix of a gel polymer electrolyte for lithium ion batteries. It shows good mechanical performance and thermal stability. The ionic conductivity of the gel polymer electrolyte is 0.20 mS cm−1 and it has a higher lithium ion transference number (t+ = 0.29) than the commercial separator (0.27). When evaluated using LiFePO4 as cathode and Li metal as the counter and reference electrode, the LiFePO4 cathode exhibits relatively higher reversible capacity for the gel polymer electrolyte than that for the commercial separator. In addition, the rate capability and cycling performance are also comparable with those for the commercial separator. This provides another direction for gel polymer electrolytes and environmental protection.

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.

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.