http://www.technologyreview.com/Energy/20524/page1/?a=f
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The Argonne researchers have improved the performance of the positive electrodes by increasing the chemical and structural stability of the materials already used in laptop batteries. In conventional lithium-ion batteries, which have cobalt oxide electrodes, a small amount of overheating, caused by overcharging the material or by electrical shorts inside a battery, can lead to rapidly increasing temperatures inside the cell and, in some cases, combustion. That's because, as the material overheats, the cobalt oxide readily gives up oxygen, which reacts with the solvent in the battery's electrolyte and generates more heat, feeding the reactions. The Argonne researchers addressed this problem by replacing some of the cobalt oxide with manganese oxide, which is chemically more stable.
The researchers' next step was to replace some of the active metal oxide materials in the electrode with a related but electrochemically inactive material, forming a composite. This material does not store energy, because it does not release and take up lithium ions as the battery is charged and discharged. (Lithium-ion batteries create electrical current as lithium ions shuttle between positive and negative electrodes.) The inactive material makes the composite more stable than conventional electrode materials, which means it can last longer. One version of the material can last for 1,500 charges and discharges without losing much capacity, he says. That's more than double the life of conventional laptop batteries.----
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The Argonne researchers have improved the performance of the positive electrodes by increasing the chemical and structural stability of the materials already used in laptop batteries. In conventional lithium-ion batteries, which have cobalt oxide electrodes, a small amount of overheating, caused by overcharging the material or by electrical shorts inside a battery, can lead to rapidly increasing temperatures inside the cell and, in some cases, combustion. That's because, as the material overheats, the cobalt oxide readily gives up oxygen, which reacts with the solvent in the battery's electrolyte and generates more heat, feeding the reactions. The Argonne researchers addressed this problem by replacing some of the cobalt oxide with manganese oxide, which is chemically more stable.
The researchers' next step was to replace some of the active metal oxide materials in the electrode with a related but electrochemically inactive material, forming a composite. This material does not store energy, because it does not release and take up lithium ions as the battery is charged and discharged. (Lithium-ion batteries create electrical current as lithium ions shuttle between positive and negative electrodes.) The inactive material makes the composite more stable than conventional electrode materials, which means it can last longer. One version of the material can last for 1,500 charges and discharges without losing much capacity, he says. That's more than double the life of conventional laptop batteries.----
