经济学人下载:一个古老的材料也许能在电池领域发挥新的作用

Science and technology
科学技术

Battery technology
电池技术

A pile of wood
那就是一堆木头

An old material may find a new use in batteries
一个古老的材料也许能在电池领域发挥新的作用

ON A list of cutting-edge materials for high-tech applications, you might not expect to see wood near the top.
对于应用在高新技术的尖端材料名单中，你可不会期待木头能排在前列。

But an experiment by Teng Li and Liangbing Hu of the University of Maryland may soon put it there.
不过马里兰大学的李腾和胡良兵所进行的一项研究可能很快会让木头名列其中。

For Dr Li and Dr Hu, writing in Nano Letters, have just described how wood might be used to make one class of batteries cheaper by permitting the lithium now employed in them to be replaced with sodium.
李博士和胡博士在《纳米快报》上发表的文章描述了如何用木头来降低电池成本—利用钠来取代目前常用的锂。

As any high-school chemist knows, lithium and sodium are chemically similar.
就如高校的化学老师做熟知的那样，锂和钠有化学相似性。

Sodium ions are, however, five times the size of lithium ions.
但是钠离子的大小是锂离子的五倍。

That matters because a battery works by shuttling ions between its anode and its cathode.
因为电池是通过在阳极和阴极之间来回传输离子来工作的，

The bigger the ion, the more damage this shuttling causes—and the shorter, in consequence, is the battery's life.
离子尺寸越大这种运动造成的损耗就越大，这就导致了电池的寿命降低。

Hitherto, that has ruled sodium out as a plausible ingredient of batteries.
因此，电池原料的选取就将钠元素排除在外了。

But engineers would still like to devise a commercially viable sodium battery, because sodium is much more abundant than lithium.
但是钠元素远远要比锂元素丰富，因此工程师们仍旧热衷于设计出商业化的钠电池。

Dr Li and Dr Hu wondered if the problem of electrode damage might be ameliorated by using a more pliant material for the frames on which the electrodes are suspended.
李博士和胡博士希望找到一种更加合适的材料来制作固定电极的框架，并由此来改善电极的磨损问题。

These frames, which also transmit current to and from the electrodes, are normally made of metal, and are therefore rigid.
这个框架同时要在电极之间传输电流，通常是由金属制作的，而且必须是刚性的。

But the two researchers reckoned that suitably treated wood could do the job of conduction equally well while providing more yielding support for an electrode that was continually expanding and contracting as ions moved in and out of it.
不过两位科研人员认为经过适当处理的木材可以起到同样效果，同时，木制框架还能为迁移离子时不断地扩张和收缩的电极供更加弹性的支撑。

To test this idea, they used slivers of wood from yellow pines.
为了验证这个想法，他们采用了黄松木薄片。

First, they coated these with carbon nanotubes, to improve their conductivity.
首先，他们在木片上涂上了一层碳纳米管来提升其传导性。

Then they applied a film of tin to each sliver.
然后，他们再在每层木片上都镀上了一层锡。

This done, they immersed the slivers in an electrolyte containing sodium ions and put the resulting battery through 400 cycles of discharging and recharging.
这些工作完成后，他们将木片浸入含钠离子的电解液中并进行400次的循环充放电实验。

As a control, they built similar batteries using slivers of copper.
他们还用铜片做的电池进行了对比实验。

The wooden battery was not perfect.
木电池并不完美，

Its initial capacity was 339 milliamp hours per gram, but that fell to 145 mAH/g over the course of the 400 cycles.
它的初始电量是339 mAH/g，但是在400次循环充放电后它的电量就降到了145 mAH/g。

This, however, was not bad for a prototype, and far better than the copper-framed batteries managed.
当然，对于初次实验而言，这个数据不赖，而且这个成绩优于铜片电池。

They had an initial capacity of 50 mAH/g.
铜片电池的初始电量为50 mAH/g，

That fell to 22 mAH/g after just 100 cycles.
而且在100次循环充放电之后就降到了22 mAH/g。

Wood, then, seems a plausible candidate for battery frames.
这样来看，木材可算得上是框架的理想候选材料。

Obviously you are not going to see wooden-framed batteries in your phone or laptop anytime soon.
很明显，短期内你不会在你的手机或笔记本电脑里看到木框架电池—这可不是李博士和胡博士的计划。

But that was never the plan for Dr Li and Dr Hu.
他们的巨型钠电池也许会应用在太阳能发电站的夜间电能存储上。

What their work might lead to is giant sodium-ion batteries for the overnight storage of electricity from solar power stations.
便宜的存储方式可是完成太阳能这幅拼图所需要的碎片之一。

Cheap storage is the missing part of the solar-energy jigsaw—for solar cells themselves are now cheap enough to compete with fossil fuels, in sunny climes at least.
—目前太阳能电池本身的成本已然能和化石燃料一较高下，至少在晴天天气下一定可以。

The search for solutions to the solar-energy problem has concentrated on making man-made materials more and more sophisticated.
解决太阳能问题的研究已经集中在了更加复杂精密的人造材料的制备上。

It would be a delicious irony if the jigsaw was completed not by one of these snazzy new substances but by one of the oldest materials around.
如果这块拼图最终是由如此古老原始、唾手可得的材料而非那些时髦的新材料完成的，这会是个不错的讽刺。