Gouri Cheruvally

Rechargeable Organic Radical Battery with Electrospun, Fibrous Membrane-Based Polymer Electrolyte

An organic radical battery (ORB) operating at room temperature with lithium metal anode and radical polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-ylmethacrylate) (PTMA) cathode with a microporous polymer electrolyte based on electrospun poly(vinylidene fluoride-co-hexafluoropropylene) membrane has been demonstrated. The polymer electrolyte with a fully interconnected pore structure, high electrolyte uptake, and high ionic conductivity is found to be suitable for use in PTMA-based ORBs. The cell with a thin cathode of 17 μm thickness incorporating 40 wt % of PTMA exhibits a discharge capacity of 111 mAh/g at 1 C-rate (0.1 mA/cm 2 ) that corresponds to ∼ 100% theoretical capacity. Good rate capability is shown by the ORB; thus, a specific capacity of 98 mAh/g is delivered even at the very high 50 C-rate. A stable cycle property is obtained at all C-rates, with the cathode structure remaining intact during cycling. The polymer electrolyte shows good compatibility with the electrodes and leads to a decrease of electrode/electrolyte interfacial resistance with cycling. The study indicates the suitability of microporous, polymer electrolyte-based ORB as a safe, lightweight, environmentally benign, flexible battery with high power-rate capability for varied applications.

Lithium/Sulfur Secondary Batteries: A Review

Lithium batteries based on elemental sulfur as the cathode-active material capture great attraction due to the high theoretical capacity, easy availability, low cost and non-toxicity of sulfur. Although lithium/sulfur (Li/S) primary cells were known much earlier, the interest in developing Li/S secondary batteries that can deliver high energy and high power was actively pursued since early 1990’s. A lot of technical challenges including the low conductivity of sulfur, dissolution of sulfurreduction products in the electrolyte leading to their migration away from the cathode, and deposition of solid reaction products on cathode matrix had to be tackled to realize a high and stable performance from rechargeable Li/S cells. This article presents briefly an overview of the studies pertaining to the different aspects of Li/S batteries including those that deal with the sulfur electrode, electrolytes, lithium anode and configuration of the batteries.

Effect of Various Lithium Salts in TEGDME Based Electrolyte for Li/Pyrite Battery

The effect of lithium salts such as LiPF6, LiBF4, LiCF3SO3 and LiN(CF3SO2)2 (LiTFSI) in tetra(ethylene glycol) dimethyl ether (TEGDME) electrolyte on the ionic conductivity, interfacial resistance and discharge properties of Li/pyrite cell at room temperature was studied. The electrolytes had good ionic conductivity at room temperature in the range 0.61 to 1.86 × 10-3 S/. The discharge capacities of Li/pyrite cells with 1M LiPF6 and LiBF4 in TEGDME were lower compared to those of the other two non-HF containing salts. The best cycle performance was exhibited by LiTFSI in TEGDME electrolyte, with a discharge capacity of 438 mAhg-1 after 20 cycles, which is ~49% of FeS2 theoretical capacity (894 mAhg-1). The good performance of LiTFSI-TEGDME electrolyte resulted mainly from its low interfacial resistance in Li/FeS2 cells, which showed a decreasing trend with cycling.

Electrochemical properties of lithium iron phosphate cathode material using polymer electrolyte

Carbon-coated lithium iron phosphate (LiFePO4/C) cathode material was synthesized by mechano-chemical activation method. The performance of LiFePO4/C in lithium battery was tested with an electrospun polymer-based electrolyte. Liquid electrolyte of 1M lithium hexafluorophosphate (LiPF6) in ethylene carbonate/dimethyl carbonate (EC/DMC) (1?:?1vol) was incorporated in electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-HFP)) microfibrous membrane to prepare the polymer electrolyte (PE). The cell based on Li|PE|Li FePO4/C exhibited an initial discharge capacity of 142?mAh?g?1 at 0.1?C-rate at room temperature. Good cycling performance even under the high current density of 2?C could be obtained. Impedance spectroscopy was applied to investigate the material behavior during 0.1?C-rate charge?discharge cycling. When the fresh cell and the cell after different cycles were compared, impedance resistance was found to decrease with cycling. Impedance study indicated good cycle life for the cell when tested at room temperature.

Effect of metal additives (Co and Ni) on the electrochemical properties of lithium/FeS2 batteries

Iron, sulfur and transition metal powders were used as the starting materials to prepare iron disulfide (FeS2) cathode material at room temperature by high energy mechanical alloying. Modified FeS2 were also prepared by incorporation of transition metals like Co and Ni. Li/FeS2 cells with the prepared iron disulfides as cathodes were studied for discharge properties at room temperature using the 0.5M LiTFSI in tetra(ethylene glycol) dimethyl ether (TEGDME). The first discharge capacities of Li/composite FeS2 cell with 5 wt.% Co and 3 wt.% Ni were 571 and 844 mAh/g, respectively, compared to 389 mAh/g for the cell without any additive. The enhanced properties resulted from the better electronic conductivity of the material containing the metallic additive. The initial capacity and cyclic performance were improved when nickel and cobalt were added to prepare the modified iron disulfide.