Papers by Keyword: Secondary Battery

Abstract: Lithium-ion batteries have received much attention for their potential use in electric vehicles (EV's) and portable electronic devices. Fabrication of lithium ion (Li-ion) batteries via ecologically sound (green) processes is also of great interest. Typically, in the production of cathode electrodes, organic solvents such as N-methyl-pyrrolidone (NMP) are used, but these chemicals are toxic. Water-based processing of LiNi_0.6Mn_0.2Co_0.2O₂ (NMC) for manufacturing cathode electrodes can provide a more environmental friendly option. In this work, water soluble styrene butadiene copolymer (SBR) and carboxymethyl cellulose (CMC) are used as binders. The active material ratio was set at 90%. The electrochemical performance of water-based NMC electrodes is examined. Additionally, various conductive agents were considered including acetylene black (A) and graphite (B). The particle sizes of conductive agent affect the electrochemical performance of the batteries. Our results show that replacing the conventional organic solvent-based manufacturing route for NMC cathodes with a water-based process is a promising way to fabricate Li-ion batteries with comparable electrochemical behavior, while avoiding toxic process materials and simultaneously reducing the overall manufacturing costs.

Abstract: Lithium secondary batteries have been widely used in the portable electric devices as power source. Recently it is expected that the realm of its applications expands to the markets such as energy storage medium of hybrid electric vehicle (HEV), electric vehicle (EV). Cathode active material is crucial in terms of performance, durability, capacity of lithium secondary batteries. It is urgent to develope the technology for mass production of cathode material to cope with the markets' demands in the near future. In this study, a calcination furnace running in real production line is modelled in 3D, and the thermal flow and gas flow after chemical reaction in the furnace is analyzed through numerical computations. Based on the results, it is shown that large volume of CO2 gas is generated from chemical reaction. High concentration of CO2 gas and it's stagnation is clearly found from the reactant containers in which the reaction occur to the bottom area of the furnace. It is also studied that 15% or more CO2 mol fraction could affect to proper formation of LiCoO2 through TGA-DSC analysis. The solutions to evacuate carbon dioxide from the furnace are suggested through the change of furnace design and operating condition as well. Keywords : Secondary battery, cathode material, calcination furnace, LiCoO2

Abstract: Iron disulfide (FeS2) is attractive as a positive electrode material in lithium batteries because of its low material cost, environmental non-toxicity, and high specific energy density. Furthermore, natural pyrite is a secondary product of the mining extraction of coal. For these reasons, natural and synthetic pyrites have been proposed as active cathode materials in secondary lithium batteries. We investigated the effect of various solvents on the electrochemical properties of lithium-FeS2 batteries. The specific discharge capacity of Li/FeS2 cells varied from 500 to 780mAh/g based on FeS2.

Abstract: Mg2Ni powder was heated up to 880°C which is higher than the melting point of Mg2Ni alloys (760°C) for 30 minutes and immediately cooled into water (14°C). And then, mechanical ball milling was conducted for 1,4,8,10,12,24 hours respectively. As milling time increased discharge capacity was increased to maximum of 700mAh/g at 12hours then decreased with increasing milling time. The best high rate dischargeability (HRD) characteristic also obtain at the 12 hours ball milling time. Therefore, the ball milling time could be shorten to 12 hours by heat treatment and rapid cooling. Praseodymium (0,0.2,0.5,0.7,1.0%Pr) was added to Mg2Ni alloys. These alloys were ground for 12 hours to investigate the improvement of cycle life. The cycle life was remarkably improved with increasing the amount of Pr. The best amount of Pr was 0.7 wt%.