电动汽车面临的最大威胁 - BBC杰克·斯图尔特(Jack Stewart)(2023年7月27日)
(图片来源Thinkstock)
拉荷亚(La Jolla)和山景城(Mountain View)同属于美国加州，一个是富豪聚集地，一个科技味十足，在这两个地方，你都可以瞥见未来——汽车的未来。在这两个地方，每一秒钟都能看到特斯拉、日产Leaf、丰田普锐斯，或者与之类似的车型。这些电动或混动汽车自然地穿梭于车流之中，而很多企业、商场和家庭也都安装了充电桩。
如果汽车厂商果真能让电动汽车梦想成真，眼前的这番景象就将在未来的某一刻普及开来。事实上，这些厂商都在花费大笔资金实现这番愿景。问题在于，如何将电动车的需求从这两座城市扩大到整个美国？
在加州的另一个地方，伊隆·马斯克(Elon Musk)的特斯拉汽车最近提出了一份计划，准备在美国西南部某个尚未披露的地点建设一座巨大的电池工厂(这是最近的热门话题)。这个所谓的“超级工厂”(Gigafactory)预算50亿美元，计划到2020年为50万辆汽车生产锂电池——这比2013年的全球产量还高。
可是，等到工厂建成时，特斯拉的计划是否会过时呢？有人认为很有可能。IHS Automotive高级规划总监菲尔·戈特(Phil Gott)认为，特斯拉这个野心勃勃的计划“很可能过于仓促”。目前正在开发的新技术可能提供更好的选择，解决专家眼中的一大电动汽车发展障碍。
这些汽车面临的一大问题在于，电池又大又重，因此每辆汽车上所能安装的数量非常有限。例如特斯拉Model S的电池组大约2米长，1.2米宽，需要沿着汽车的地板安装。这种顶尖车型单次充电的续航里程约为300英里(482公里)，日产Leaf略高于80英里(128公里)。不仅如此，充电速度也比加油速度慢得多。
由于要定期充电，而且每次充电都耗时长久，以至于电动汽车的发展受到限制。(图片来源Thinkstock)
那么，如何才能生产出更好的电池呢？从本质上讲，电池都包含正负电极、分离器和电解质。很多不同类型的材料都可以充当电极，不同的材料组合所能存储的电量各不相同。然而，电池寿命和安全特性也会随着材料的改变而发生变化，所以必须要做出一些妥协。锂电池很受欢迎，但由于可能在飞机上引发火灾，因此运输时受到一定的限制。比锂电池更易反应或更不稳定的电池都很危险。但找到合适的组合便可获得巨大回报。
电池技术经过了长达数十年的发展。最初使用的是铅酸电池，这种体积巨大的电池至今仍在汽车上广泛使用。之后便是镍镉电池，这种充电电池开启了便携技术的新时代，催生了笔记本电脑、手机等各种设备，甚至还包括你童年记忆中的遥控汽车。然后就轮到了镍氢电池，它的容量(也称能量密度)扩大了一倍。现代化的电子设备和电动汽车都采用了锂电池。
今后的电池技术将会采用更加复杂的名称，例如锂钴镍锰氧化物电池。这些材料的属性非常复杂，而目前的工作不仅是要搞清楚这些材料为什么能起效，还要搞清楚它们起效的方式——电子在材料中移动时遵循的基本物理原理。
“我们正在开发一些材料，可以将目前的能量密度翻番。”芝加哥阿贡国家实验室材料科学家丹尼尔·亚伯拉罕(Daniel Abraham)说，“我们先想象出各种可行的材料，然后再尝试在实验室里合成出来。”
特斯拉汽车这样的公司已经进一步拉近了电动汽车与主流用户之间的距离(图片来源：AFP/Getty Images)
目前最受关注的就是锂氧电池和锂硫电池。如果能够成功，锂氧电池将比目前的锂电池实现一个数量级的跨越。“这是当今的一大热门领域。”亚伯拉罕说。
事实上，大众汽车最近就透露，该公司正在研发锂氧电池。由于开发工作正在进行过程中，所以他们并未披露具体使用的化学和材料成分。该公司的工程师甚至不肯透露这项技术是否已经在汽车上进行过测试，还是仍然没有走出“实验室”。
不过，尽管这项技术颇具革命潜力，但要生产出性能稳定、安全可靠、续航长久的锂氧电池，仍然需要面临很大的技术挑战。目前为止，电极仍然不够稳定。
但世界各地的实验室都在研究这一问题，试图克服种种弊端。随着各大厂商越来越重视这些新颖的电池技术，他们的开发进度也有望进一步加快，并最终为我们生产出速度更快、跑得更远的电动汽车。
（责编：友义）
The electric car’s biggest threat may be its battery - By Jack Stewart
If the electric car-makers have their way, this is the future that we will all experience at some point, and they are pouring a lot of money into making it happen. The question is how easy is it to scale up the demands of small enclaves to an entire country?
Elsewhere in California Elon Musk’s Tesla Motors recently proposed plans for an enormous battery factory at an as-yet-undisclosed south western United States location (which is the subject of much fevered discussion). This so-called “Gigafactory” is set to cost $5 billion, and slated to produce lithium-ion batteries for 500,000 cars by 2020 – which is more produced annually than were produced worldwide in 2013.
But will Tesla’s plan seem out of date by the time the factory starts up? Some think so. Phil Gott, the senior planning director at IHS Automotive, believes Tesla’s ambitious plan is “probably premature”. New technologies are being developed that could offer better alternatives to address what experts say is one of the biggest limiting factors for electric vehicles.
The problem these cars face is that batteries are big and heavy, and as a consequence only a limited number can be installed. The Tesla Model S for example, has a battery pack approximately two metres long by 1.2 metres wide, which is installed flat along the floor of the car. In the top-spec car, that gives a range of about 300 miles (482km) before plugging in and recharging is required. The Nissan Leaf achieves more like 80 miles (128km). On top of that, charging is a much slower process than just filling up with petrol.
How can you make a better battery, then? At its most basic a battery contains a positive and negative electrode, a separator and an electrolyte. Many different types of materials can be used as electrodes, the different combinations of materials allowing different amounts of energy to be stored. However battery life and the safety characteristics change as the materials change, so a compromise is always necessary. Lithium-ion batteries are popular, but have been implicated in fires on board planes, and their transport is restricted . Anything more reactive or unstable could be a hazard. Get the combination right, though, and the payoff could be huge.
The latest efforts follow a long line of improvements over the decades. First we had lead-acid batteries, the type that is still commonly used in cars; they are huge. Then, you might remember NiCad (nickel-cadmium) batteries – they were the rechargeable batteries that heralded a new era of portable technology – laptops, phones, and the like, as well as the remote control cars of our childhoods. Then came NiMH (nickel metal hydride) batteries, with about twice the capacity, or energy density. Now modern devices and electric cars are powered by lithium ion, or Li-ion, batteries.
Going forward, get ready for battery technology to have increasingly complicated names; LiNiMnCo (lithium–nickel-manganese-cobalt-oxides) for example. These materials have complex properties, and work is now going on to figure out not only why these materials work, but also exactly how they work - the basic physics of the electrons moving around the materials.
“There are materials we are working on at Argonne which can double the current energy density available for batteries,” says Daniel Abraham, a material scientist at Argonne National Laboratory, outside Chicago in the US. “We dream up or imagine the types of materials we would like to work with, then we attempt to synthesize the materials in the laboratory.”
Currently the batteries getting all the buzz are lithium-air, or more properly lithium-oxygen, as well as lithium-sulphur batteries. Li-oxygen batteries, if they can be made to work, under all conditions, will be an order of magnitude improvement over the current Li-ion batteries. “It’s a very hot field at this time” says Abraham.
Indeed Volkswagen has recently hinted that it is investigating lithium-air batteries. The precise chemical/ material combination that they are using has not been revealed as development work continues. The company’s engineers will not even say if the technology has been tested in a car, or if it is still at the ‘lab bench’ stage.
But although the technology has revolutionary potential, the technical challenges of making a Li-air battery work consistently, reliably, and safely – and crucially for extended durations – are large. So far the electrodes have proven unstable.
Labs around the world are working on the problem though, trying to overcome the drawbacks. The hope is that greater emphasis on these “beyond lithium-ion” technologies, will ensure faster progress in their development, and in the long-run faster cars that travel farther.