這個在實驗室裡的發現會不會就此改變了電池的技術呢？蘇格蘭聖安德魯斯大學的彼德布魯斯在研究取代鋰鈷氧化物做為鋰電池正極材料時發現了：可以用環境中的氧氣來充電的特性。
鋰離子(lithum-ion,リチウムイオン)電池充電時（充電器將電流送入鋰電池的正極），電子經由充電器外部進入電池負極（電流方向與電子流方向剛好相反）的活性材料結構中（如碳），同時正極材料（通常為鋰金屬氧化物）中的鋰離子則離開正極，經由電解液通過隔離膜進入負極。在放電時，電子及鋰離子則反向而行。
這個發現是研究團隊以鋰氧化物與多孔碳做為電池的兩極，將多孔碳的一側貼在富含鋰電子的電解液上，另一邊放著網狀的簍空格，讓空氣可以流通，空氣中的氧氣取代了鈷氧化物在鋰電子電池中的位置。
這項設計可以使現在的電池大小和重量所小到現在的1/8或1/10，鋰電子電池中佔成本三成的鋰鈷氧化物也可以省掉。
MonitorAir powerSep 3rd 2009From The Economist print editionEnergy: Batteries that draw oxygen from the air could provide a cheaper, lighter and longer-lasting alternative to existing designs
Illustration by Belle Mellor
MOBILE phones looked like bricks in the 1980s. That was largely because the batteries needed to power them were so hefty. When lithium-ion batteries were invented, mobile phones became small enough to be slipped into a pocket. Now a new design of battery, which uses oxygen from ambient air to power devices, could
provide even an smaller and lighter source of power. Not only that, such batteries
would be cheaper and would run for longer between charges.
cobalt n. 1. [化] 鈷金屬元素,符號 Co, 原子序數27 2. 鈷類顏料;鈷色,深藍色 Lithium-ion batteries have two electrodes immersed in an electrically conductive solution, called an electrolyte. One of the electrodes,
the cathode, is made of lithium cobalt oxide; the other,
the anode, is composed of carbon. When the battery is being charged, positively charged lithium ions break away from the cathode and travel in the electrolyte to the anode, where they meet electrons brought there by a charging device. When electricity is needed, the anode releases the lithium ions, which rapidly move back to the cathode. As they do so, the electrons that were paired with them in the anode during the charging process are released. These electrons power an external circuit.
Peter Bruce and his colleagues at the
University of St Andrews in Scotland came up with the idea of
replacing the lithium cobalt oxide electrode with a cheaper and lighter alternative. They designed an electrode made from porous carbon and lithium oxide. They knew that lithium oxide forms naturally from lithium ions, electrons and oxygen, but, to their surprise, they found that it could also be made to separate easily when an electric current passed through it. They
exposed one side of their porous carbon electrode to an electrolyte rich in lithium ions and put a mesh window on the other side of the electrode through which air could be drawn. Oxygen from the air took the place of the cobalt oxide.When they charged their battery, the lithium ions migrated to the anode where they combined with electrons from the charging device. When they discharged it, lithium ions and electrons were released from the anode. The ions crossed the electrolyte and the electrons travelled round the external circuit. The ions and electrons met at the cathode, and combined with the oxygen to form lithium oxide that filled the pores in the carbon.
Because the oxygen being used by the battery comes from the surrounding air, the device that Dr Bruce’s team has designed can be a mere one-eighth to one-tenth the size and weight of modern batteries, while still carrying the same charge. Making such a battery is also expected to be cheaper. Lithium cobalt oxide accounts for 30% of the cost of a lithium-ion battery. Air, however, is free.
http://www.economist.com/sciencetechnology/tq/displaystory.cfm?story_id=14299690 補充資料: 國科會：Ｅ世代的能源──鋰電池 by 李文雄 臺灣超能源品保部
http://web1.nsc.gov.tw/ct.aspx?xItem=7853&ctNode=40&mp=1維基百科：鋰離子電池
http://zh.wikipedia.org/zh-tw/%E9%94%82%E7%A6%BB%E5%AD%90%E7%94%B5%E6%B1%A0
The story was taken from the website of The Economist. The copyright remains with the Economist. The Economist is not involved, nor endorse the production of this blog.
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