怎么使Model S的价格便宜一半？特斯拉有了新计划

    特斯拉生产平价电动汽车的计划似乎总是指向内华达州的里诺市，该公司正在这里兴建价值50亿美元的超级电池厂，它的目标是在2017年底前获得足够的产能，以便将锂离子电池组的每千瓦时成本削减30%以上。

    许多公司都表示要降低电池价格并提高容量，并且正在确立相应的概念。特斯拉的最终目标是推出比Model S豪华电动汽车便宜一半的产品。实际情况表明，该公司有好几条路可走。

    特斯拉的最新方向是硅。不是硅谷，而是硅这种材料，它正在改变电池的生产方式。上周五，特斯拉展示了新的90千瓦时电池组，这种升级产品的容量提高了5%，可以让特斯拉的电动汽车多行驶15英里（约24公里）左右。虽然外观可能没有变化，但它使用了硅，这是锂离子电池技术的一个进步。

    上周，特斯拉首席执行官埃隆·穆斯克在电话里告诉记者，该公司对电池进行了改进，具体方法是在阳极中使用了一些硅材料，进而改变了电池的化学反应过程。

    穆斯克说：“我们的方向是用硅来做阳极，以上做法只是迈出一小步。我们用的主要材料仍是人造石墨，但我们会慢慢地在阳极中加入越来越多的硅。”

    对外行来说，这听起来也许跟镜面加工很像。而实际上，这样做有可能让电池变得更好、更廉价；对特斯拉（和其他电池制造商）来说，它既重要又难度极大。

    加拿大新斯科舍省戴尔豪西大学锂离子电池首席研究员杰夫·达恩教授最近和特斯拉签订了为期五年的独家合作协议。他说：“电池厂商正在争相提高电池中的硅含量。在全球锂离子电池领域，正在进行硅课题攻关的研究人员不计其数。许多学术界和实业界人士也在非常努力地钻研这个问题。”

    锂离子电池小科普

    电池有两端，一端是阳极，另一端是阴极，二者之间是电解液。在充电和放电过程中，离子通过电解液在两极之间移动。

    商用锂离子电池的阳极一般由石墨制成。如果用硅制作阳极，其单位体积锂离子容量可达到前者的10倍左右。理论上，如果用硅大量取代石墨，石墨阴极就可能变细，从而扩大容纳活性材料的空间。这样就可以提高电池的能量密度，也就是单位体积能量存储能力。

    换句话说就是，尺寸不变，能量增多。同时，在锂离子电池中，硅的质量不需要像太阳能电池或集成电路中那么高，这就意味着价格较低。电池中的硅越多，就越容易降低成本。

    这就是所有电池厂商的目标——提高产品质量，降低成本。

    听起来很容易吧？但达恩说，难得很。达恩正在3M或者加拿大自然科学与工程研究理事会资助的一个项目中，这个项目就是要开发持续时间更长、成本更低的锂离子电池。完成了3M的研究项目后，达恩将从2016年6月开始和特斯拉进行独家合作。

    把锂和硅放在一起的难点在于，最终出现的原子数量几乎是初期的五倍，而这会带来各种各样的问题。

    Tesla’s road to a cheaper electric car has always appeared to lead straight to Reno, where the electric automaker is building a $5 billion gigafactory designed with enough capacity to reduce the per-kilowatt-hour cost of its lithium-ion battery packs by over 30% by the end of 2017.

    Many companies are already planning concepts around the promise of cheaper, higher-capacity batteries. But, it turns out that TeslaTSLA 0.40% has more than one path toward its ultimate goal of an electric car that’s 50% cheaper than its luxury Model S.

    The newest direction Tesla is headed toward is silicon—not the Valley, but the material that is changing the way batteries are made. Tesla’s new 90 kilowatt-hour battery pack—an upgrade announced Friday that increases pack energy by 5% and adds about 15 miles of range to its vehicles—might look the same. But the inclusion of silicon is an advance for lithium-ion technology.

    During a call with reporters last week, CEO Elon Musk said the company had improved the battery by shifting the cell chemistry for the pack to partially use silicon in the anode.

    “This is just sort of a baby step in the direction of using silicon in the anode,” Musk said during the call. “We’re still primarily using synthetic graphite, but over time we’ll be increasing silicon in the anode.”

    For the unfamiliar, this might sound like minor tinkering. It’s actually an important and challenging step for Tesla (and other battery manufacturers) that could lead to a better, cheaper battery.

    “It’s a race among the battery makers to get more and more silicon in,” said Jeff Dahn, a leading lithium-ion battery researcher and professor at Dalhousie University in Nova Scotia who recently signed a 5-year exclusive partnership with Tesla. “The number of researchers around the world working on silicon for lithium-ion cells is mindboggling. A large number of academics and industrial folks are working really hard on this problem.”

    Batteries 101

    A battery contains two electrodes: an anode (negative) on one side and a cathode (positive) on the other. An electrolyte, essentially the courier that moves ions between the electrodes when charging and discharging, sits in the middle.

    Graphite is commonly used as the anode in commercial lithium-ion batteries. However, a silicon anode can store about 10 times more (per unit volume) lithium ions. In theory, if you replaced a lot of graphite in the cell with silicon, the thickness of the graphite negative electrode could be reduced. There would be more space to add more active material and you could, in turn, increase the energy density—or the amount of energy that can be stored in a battery per its volume—of the cell.

    In other words, you could pack more energy in the same space. Plus, the silicon used in the battery space doesn’t need to be the same quality as what’s used in solar cells and integrated circuits, which means it’s cheaper. The more silicon you put in the battery, the easier it is to drive costs down.

    That’s the goal of battery makers everywhere: to improve their product while reducing costs.

    Sounds easy enough, right? Hardly, says Dahn, who is currently working on a project funded by 3M and the Natural Sciences and Engineering Research Council of Canada to develop longer lasting, lower cost lithium-ion battery cells. Their exclusive partnership with Tesla will begin in June 2016, once Dahn has completed the 3M research project.

    The trick is that when you add lithium to the silicon you end up with almost five times the original number of atoms you started with. And that causes all kinds of problems.