本帖最后由 zerowing 于 2015-10-31 06:02 编辑 / w" x1 {& }6 V* D( }* |
; e" h; E6 J3 {( K* I! a呵呵，论坛里蹲了几年了。一直也没什么回馈论坛的。从今天起，每周坚持更新一篇来自BBC的关于前沿科技的新闻。既是一种自我学习，也作为对论坛的一种回报吧。7 @& E3 k& w: x& ?0 z! n
PS. 文章纯手工翻译，有问题的话，还请指出。 N r3 n8 u. i; B
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New Lithium-air battery design shows promise
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8 T$ d/ H+ O! i; j) L+ R9 v新设计展示锂空气电池前景 : d* T' \, D0 W8 w% D' E; `+ i
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A 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. # K3 X1 h/ w2 z+ u; `
一直以来挡在锂空气电池领域发展道路上的几大障碍，在该领域的新设计下得到克服。相对于现在的锂离子电池，锂空气电池具有更高的能量存储密度。因此，锂空气电池的发展对于电动汽车行业影响深远。这项发布在科学网的新设计，采用海绵状石墨烯电极技术和新的化学反应方式以驱动电池。新技术使得这种电池相对于早前锂空气电池设计，能量损失大幅降低，充电循环寿命成倍提高。 锂空气电池的工作原理是，吸入自然空气参与到电池内的放电化学反应中，即锂离子从正极移动到负极处，由自然空气氧化反应。目前，在剑桥大学，使用旧技术的工程师仅在实验室实验中通过纯氧进行氧化反应，而非空气。而格雷小组的首个原形机已经能在湿润氧气环境下工作。 “我们真正希望得到的是真正的锂空气电池，一个使用不许取出二氧化碳、氮气和水气的自然空气的锂空气电池。”该研究的资深学者——·克莱尔·格雷教授告诉BBC，“而我们现在实现的新系统中至少已经可以大量允许水气的存在。” 尽管格雷教授的研究小组已经取得目前的显著进步，但是他们表示距离真正的商业使用至少还需要10年的研究时间。
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Their 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.
, g5 F. I6 o( J6 V: I. Y* L; ~尽管格雷小组的理论样机还十分简陋，比如格雷教授的解释：“我们目前的实验电池仍需要几天的充电和强制放电周期，而人们期望这个过程发生在几分钟之内。”但这已经是巨大的成功了。
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' b4 g: U. I5 v; f& `* @ M" N: \目前的设计使得这种锂空气电池的能量密度已经接近理论上限。这意味着，没充一次电，电动汽车可以穿越一个国家，而非一个城市。同时，新电池的充电电压是3V，放电电压是2.8V，其中，高达93%的效率意味着这款电池仅损失了令人惊讶的一点能量转为发热。而这个效率已经相当接近目前的锂离子电池的水平，而对于早期的锂空气电池来说无疑是巨大的进步。
! r, G$ ~6 e& R- ?, d而更关键的是，这些侧使用的样品在经过2000次充放电循环后，仍只微小地影响其正常工作水平。 “我们已经对我们的电池进行充放电循环旬月有余，几乎没有发现不利的影响。”格雷教授介绍道。 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). ' j" t" {' @' U5 {* n3 |5 X. T
2 Q/ D% u/ ~( _9 i [# } 这项新设计成功的一个原因在于其负极的独特设计——呈海绵状排列的石墨烯。 这种所谓的“奇迹材料”是从一个原子厚的碳片层构建而来。这些负极上的密集孔使得放电反应的产物可以堆积于此，而当充电反应发生时，又将这些堆积物溶解。
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; E8 \( u7 c) M p3 @# Y! V 同样重要的是化学反应本身。格雷教授的研究小组采用一种新的添加剂——碘化锂，以改变电池核心的化学反应。通过替代旧锂空气电池中使用的二氧化二锂，放电反映产生的氢氧化锂囤积在负极处。而当发生充电反映是，所有的氢氧化锂将被全部溶解，锂离子重新回到正极处。
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' |+ q+ p, b4 Y+ Z% p% A"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." + f ]% v0 g: X* u3 d: K9 T! n
“这是一种完全不同的化学反应；它带给我们新的思考。”格雷教授说，“虽然离商业化还远，但它却提供了我们一些有趣的研究方向。”
8 q" t' Q) u4 Y+ N; c; ? 伦敦大学学院的化学工程师保罗·舍灵博士指出，剑桥大学的设计对于将锂空气电池应用于实际中迈出了重要的一步。 “他们干的漂亮！”保罗告诉记者，“锂空气电池曾经饱受各种问题困扰，特别是其低下的循环寿命。而这个新的设计可能可以解决所有问题。”
8 o6 y+ ^% i" a: L( q4 Z “如果成功”，舍灵博士补充道，“锂空气电池将会因为其能量密度几近传统的汽油能量密度（能量/公斤）而给世界带来巨大的变化。” 就像格雷教授说的那样，新电池的能量密度将会让一辆汽车从北京开到上海。（好吧，人家说的是从伦敦到爱丁堡。原谅我的意译） # R5 w8 Q" w) `! d7 I# l" j7 U
. B, R4 v# ~: X" R/ [! U) R6 i全文完。欢迎指正。 W! Q- N% l0 q/ h
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发表于 2015-10-31 06:01:40
发表于 2015-10-31 17:14:37
