本帖最后由 zerowing 于 2015-10-31 06:02 編輯 - Q* \8 ^) Y$ ^0 o; Y/ j6 z- o" ^
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呵呵，論壇里蹲了幾年了。一直也沒什么回饋論壇的。從今天起，每周堅持更新一篇來自BBC的關(guān)于前沿科技的新聞。既是一種自我學(xué)習(xí)，也作為對論壇的一種回報吧。7 O, W/ O( M& c( d9 b8 M. H
PS. 文章純手工翻譯，有問題的話，還請指出。
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New Lithium-air battery design shows promise
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) O# G" y, d7 u新設(shè)計展示鋰空氣電池前景 + W' |6 ~( C1 \. U' b: _
) p8 S, P. c$ [2 M+ C) B) }9 J5 WA new design for lithium-air batteries overcomes several big hurdles that have stood in the way of this concept. Lithium-air cells can store energy much more densely than today's lithium-ion batteries, making them particularly promising for electric cars. The design, published in Science, uses a spongy graphene electrode and a new chemical reaction to drive the cell. It loses much less energy and can be recharged many more times than previous attempts at lithium-air batteries. The hope for lithium-air batteries is that they will take in regular air to fuel the chemical reaction that releases electricity: lithium ions move from the positive electrode to the negative one, where they are oxidised. At present the engineers behind the new effort, at the University of Cambridge, have only made laboratory test units which operate in pure oxygen, rather than air. In a first, however, the prototypes can operate when that oxygen is moist. "What we really want is a [true] lithium-air battery - one that just takes in air, without having to remove CO2, nitrogen and water," Prof Clare Grey, the senior author on the study, told BBC News. "And now we have a system that at least tolerates a lot of water." Despite the significant progress made by Prof Grey's team, they say a commercial lithium-air battery is at least 10 years away.
- a" x& s( s8 o- e2 G1 }一直以來擋在鋰空氣電池領(lǐng)域發(fā)展道路上的幾大障礙，在該領(lǐng)域的新設(shè)計下得到克服。相對于現(xiàn)在的鋰離子電池，鋰空氣電池具有更高的能量存儲密度。因此，鋰空氣電池的發(fā)展對于電動汽車行業(yè)影響深遠。這項發(fā)布在科學(xué)網(wǎng)的新設(shè)計，采用海綿狀石墨烯電極技術(shù)和新的化學(xué)反應(yīng)方式以驅(qū)動電池。新技術(shù)使得這種電池相對于早前鋰空氣電池設(shè)計，能量損失大幅降低，充電循環(huán)壽命成倍提高。 鋰空氣電池的工作原理是，吸入自然空氣參與到電池內(nèi)的放電化學(xué)反應(yīng)中，即鋰離子從正極移動到負極處，由自然空氣氧化反應(yīng)。目前，在劍橋大學(xué)，使用舊技術(shù)的工程師僅在實驗室實驗中通過純氧進行氧化反應(yīng)，而非空氣。而格雷小組的首個原形機已經(jīng)能在濕潤氧氣環(huán)境下工作。 “我們真正希望得到的是真正的鋰空氣電池，一個使用不許取出二氧化碳、氮氣和水氣的自然空氣的鋰空氣電池。”該研究的資深學(xué)者——·克萊爾·格雷教授告訴BBC，“而我們現(xiàn)在實現(xiàn)的新系統(tǒng)中至少已經(jīng)可以大量允許水氣的存在。” 盡管格雷教授的研究小組已經(jīng)取得目前的顯著進步，但是他們表示距離真正的商業(yè)使用至少還需要10年的研究時間。
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; e3 S4 V& F; a& d1 Q BTheir demonstration units, for example, are still rather sluggish. "Our batteries take days to charge and discharge, when you want it to happen in minutes and seconds," Prof Grey explained. But the design has major pluses. 'New way of thinking'It packs in energy at a density that is almost the theoretical limit for lithium-air batteries. That energy density is what will eventually send electric cars across countries, rather than cities, on a single charge. It also charges at a voltage of 3.0 and discharges at 2.8 volts - an efficiency of 93% - meaning it loses surprisingly little energy as heat. This is close to the efficiency of current lithium-ion batteries, and a big improvement on previous lithium-air efforts. And crucially, these test batteries can be charged and recharged more than 2,000 times, with little effect on their function. "We've been able to cycle our cells for months, with very little evidence of side reactions," Prof Grey said. 4 l' h* O6 ]) j
盡管格雷小組的理論樣機還十分簡陋，比如格雷教授的解釋：“我們目前的實驗電池仍需要幾天的充電和強制放電周期，而人們期望這個過程發(fā)生在幾分鐘之內(nèi)。”但這已經(jīng)是巨大的成功了。
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目前的設(shè)計使得這種鋰空氣電池的能量密度已經(jīng)接近理論上限。這意味著，沒充一次電，電動汽車可以穿越一個國家，而非一個城市。同時，新電池的充電電壓是3V，放電電壓是2.8V，其中，高達93%的效率意味著這款電池僅損失了令人驚訝的一點能量轉(zhuǎn)為發(fā)熱。而這個效率已經(jīng)相當(dāng)接近目前的鋰離子電池的水平，而對于早期的鋰空氣電池來說無疑是巨大的進步。
& S* d, E& ?" a# z7 a' j/ W3 Z而更關(guān)鍵的是，這些側(cè)使用的樣品在經(jīng)過2000次充放電循環(huán)后，仍只微小地影響其正常工作水平。 “我們已經(jīng)對我們的電池進行充放電循環(huán)旬月有余，幾乎沒有發(fā)現(xiàn)不利的影響。”格雷教授介紹道。 Part of the reason for this success is the design of the negative electrode (or cathode), which is made from a sponge-like arrangement of graphene. This so-called "wonder material" is built up from one-atom-thick sheets of carbon. The holes in the porous cathode allow reaction products to build up, as the battery discharges, and then dissolve away again as it gets recharged. Also critical is the chemical reaction itself. Prof Grey's team has used an additive, lithium iodide, to change the chemistry at the heart of the battery. Instead of lithium peroxide (Li2O2), as in most other lithium-air designs, the discharging reaction produces lithium hydroxide (LiOH) at the cathode. And that lithium hydroxide can be completely dissolved away again, when the battery is recharged and the lithium ions return to the positive electrode (anode). ; Q% d! a' l! o+ Q, G" t; t
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這項新設(shè)計成功的一個原因在于其負極的獨特設(shè)計——呈海綿狀排列的石墨烯。 這種所謂的“奇跡材料”是從一個原子厚的碳片層構(gòu)建而來。這些負極上的密集孔使得放電反應(yīng)的產(chǎn)物可以堆積于此，而當(dāng)充電反應(yīng)發(fā)生時，又將這些堆積物溶解。' f& O/ g+ r$ C {3 a% Y
7 e: o+ c, {+ d5 q: H* T% o* N* H/ j 同樣重要的是化學(xué)反應(yīng)本身。格雷教授的研究小組采用一種新的添加劑——碘化鋰，以改變電池核心的化學(xué)反應(yīng)。通過替代舊鋰空氣電池中使用的二氧化二鋰，放電反映產(chǎn)生的氫氧化鋰囤積在負極處。而當(dāng)發(fā)生充電反映是，所有的氫氧化鋰將被全部溶解，鋰離子重新回到正極處。, Q1 \6 z4 o2 l: u" G' d0 [, v
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, d& w8 f$ V. j5 ^ O1 D+ K"It's a very different chemistry; it gives a new way of thinking about it," said Prof Grey. "It's a way off being commercial, but it does provide some interesting new directions to study." Dr Paul Shearing, a chemical engineer at University College London, said the Cambridge design was "an important step" towards taking lithium-air batteries out of the lab. "It's very impressive work," he told the BBC. "Lithium air batteries [have been] plagued with problems, particularly around poor cycle life. This potentially could address those problems." If successful, Dr Shearing added, lithium-air batteries could make a huge difference because their energy density very nearly matches the energy-per-kg packed by petrol. As Prof Grey put it: "It's the energy density that's going to make that car battery that gets [from London] to Edinburgh." & O' q1 e2 g, {, h* _" z
“這是一種完全不同的化學(xué)反應(yīng)；它帶給我們新的思考。”格雷教授說，“雖然離商業(yè)化還遠，但它卻提供了我們一些有趣的研究方向。”
+ K8 Y9 `7 l4 P% g9 ? 倫敦大學(xué)學(xué)院的化學(xué)工程師保羅·舍靈博士指出，劍橋大學(xué)的設(shè)計對于將鋰空氣電池應(yīng)用于實際中邁出了重要的一步。 “他們干的漂亮！”保羅告訴記者，“鋰空氣電池曾經(jīng)飽受各種問題困擾，特別是其低下的循環(huán)壽命。而這個新的設(shè)計可能可以解決所有問題。”- c# Z! h; }: x2 \; E* L
“如果成功”，舍靈博士補充道，“鋰空氣電池將會因為其能量密度幾近傳統(tǒng)的汽油能量密度（能量/公斤）而給世界帶來巨大的變化。” 就像格雷教授說的那樣，新電池的能量密度將會讓一輛汽車從北京開到上海。（好吧，人家說的是從倫敦到愛丁堡。原諒我的意譯）
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全文完。歡迎指正。; Z% g1 c& u a1 h7 h& P
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