????特斯拉生產(chǎn)平價(jià)電動(dòng)汽車的計(jì)劃似乎總是指向內(nèi)華達(dá)州的里諾市，該公司正在這里興建價(jià)值50億美元的超級電池廠，它的目標(biāo)是在2017年底前獲得足夠的產(chǎn)能，以便將鋰離子電池組的每千瓦時(shí)成本削減30%以上。

????許多公司都表示要降低電池價(jià)格并提高容量，并且正在確立相應(yīng)的概念。特斯拉的最終目標(biāo)是推出比Model S豪華電動(dòng)汽車便宜一半的產(chǎn)品。實(shí)際情況表明，該公司有好幾條路可走。

????特斯拉的最新方向是硅。不是硅谷，而是硅這種材料，它正在改變電池的生產(chǎn)方式。上周五，特斯拉展示了新的90千瓦時(shí)電池組，這種升級產(chǎn)品的容量提高了5%，可以讓特斯拉的電動(dòng)汽車多行駛15英里（約24公里）左右。雖然外觀可能沒有變化，但它使用了硅，這是鋰離子電池技術(shù)的一個(gè)進(jìn)步。

????上周，特斯拉首席執(zhí)行官埃隆·穆斯克在電話里告訴記者，該公司對電池進(jìn)行了改進(jìn)，具體方法是在陽極中使用了一些硅材料，進(jìn)而改變了電池的化學(xué)反應(yīng)過程。

????穆斯克說：“我們的方向是用硅來做陽極，以上做法只是邁出一小步。我們用的主要材料仍是人造石墨，但我們會慢慢地在陽極中加入越來越多的硅。”

????對外行來說，這聽起來也許跟鏡面加工很像。而實(shí)際上，這樣做有可能讓電池變得更好、更廉價(jià)；對特斯拉（和其他電池制造商）來說，它既重要又難度極大。

????加拿大新斯科舍省戴爾豪西大學(xué)鋰離子電池首席研究員杰夫·達(dá)恩教授最近和特斯拉簽訂了為期五年的獨(dú)家合作協(xié)議。他說：“電池廠商正在爭相提高電池中的硅含量。在全球鋰離子電池領(lǐng)域，正在進(jìn)行硅課題攻關(guān)的研究人員不計(jì)其數(shù)。許多學(xué)術(shù)界和實(shí)業(yè)界人士也在非常努力地鉆研這個(gè)問題。”

????鋰離子電池小科普

????電池有兩端，一端是陽極，另一端是陰極，二者之間是電解液。在充電和放電過程中，離子通過電解液在兩極之間移動(dòng)。

????商用鋰離子電池的陽極一般由石墨制成。如果用硅制作陽極，其單位體積鋰離子容量可達(dá)到前者的10倍左右。理論上，如果用硅大量取代石墨，石墨陰極就可能變細(xì)，從而擴(kuò)大容納活性材料的空間。這樣就可以提高電池的能量密度，也就是單位體積能量存儲能力。

????換句話說就是，尺寸不變，能量增多。同時(shí)，在鋰離子電池中，硅的質(zhì)量不需要像太陽能電池或集成電路中那么高，這就意味著價(jià)格較低。電池中的硅越多，就越容易降低成本。

????這就是所有電池廠商的目標(biāo)——提高產(chǎn)品質(zhì)量，降低成本。

????聽起來很容易吧？但達(dá)恩說，難得很。達(dá)恩正在3M或者加拿大自然科學(xué)與工程研究理事會資助的一個(gè)項(xiàng)目中，這個(gè)項(xiàng)目就是要開發(fā)持續(xù)時(shí)間更長、成本更低的鋰離子電池。完成了3M的研究項(xiàng)目后，達(dá)恩將從2016年6月開始和特斯拉進(jìn)行獨(dú)家合作。

????把鋰和硅放在一起的難點(diǎn)在于，最終出現(xiàn)的原子數(shù)量幾乎是初期的五倍，而這會帶來各種各樣的問題。

????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.