電池之死

為什么電池會死?并且，為什么它們一生只能被充電有限的次數(shù)?

My young son asked me about that years ago when his battery-powered toy car stopped moving, wondering about what he called an "everlasting battery".

幾年前，當裝有電池的玩具車停止移動時，我的小兒子問我，他想知道為什么不買一塊 “永恒的電池”。

And this same question has probably crossed the mind of every cellphone user trying to send one last text before the screen blinks off.

同樣的問題可能經(jīng)常閃過那些趕在手機屏幕變黑前發(fā)出最后一條信息的用戶的腦海里。

Research, like mine, continues around the world to make batteries that charge faster, last longer, and can be recharged and discharged many more times than today's.

在世界各地，都有像我這樣的人從事著類似的研究，目的是使電池充電更快，使用壽命更長，充電和放電的次數(shù)比現(xiàn)在多很多倍。

But as much as you and I would like, it's impossible to make a truly everlasting battery. I have taught thermodynamics for more than 30 years. So far, there is nothing that suggests we can break the fundamental laws of science to get that elusive battery.

但是，就像你和我所知道的那樣，制造一塊真正永恒的電池是不可能的。我在課堂上講授熱力學的時間已有30多年，到目前為止，沒有任何跡象表明我們能夠打破最基本的科學定律制造出神奇的電池。

Battery scientists and engineers call the main problem "capacity fade".

電池科學家和工程師將主要問題稱之為“容量衰減”。

Regular people wonder about it with questions like "Why won't my battery hold a charge?" and complaints like "I just recharged this thing and it's already out again!"

普通人或許會對這個問題感到疑惑，發(fā)出這樣的疑問：“為什么我的電池不能充電了?”或者投訴：“我剛剛充好，它就又用光了!”

It's a result of the second law of thermodynamics, which states that whenever some real process happens, it creates a certain amount of wasted energy along the way that can never be recovered.

這是熱力學第二定律的結(jié)果，該定律支配著事件萬物，無論何時發(fā)生的現(xiàn)實過程，都會浪費掉一定量的能量，而這些能量是絕無可能被回收利用的。

Any time a battery is charged or discharged, there's a little bit of wasted energy – a little bit of wasted capacity in the battery that cannot be recovered.

電池充電或放電，都會浪費一點能量，而這一點點浪費對于電池而言，是無法恢復的。

To envision how this works, think about battery use like transferring water between two cups. Using a battery is like emptying the water from one cup into the other, and charging the battery involves pouring the water back into the first cup.

為了設(shè)想它們的工作機理，考慮一下電池的使用情景，類似于在兩個杯子之間轉(zhuǎn)移水。使用電池就像將水從一個杯子倒入另一個杯子中，給電池充電就是將水倒回到第一杯子里。

Even if you do it one or two times without spilling a drop, there's always just a little tiny bit left in each cup that you can't pour out.

即使你連續(xù)好幾次都沒有在杯子外掉落一滴水，但是每個杯子里總會殘留下你無法倒出來的一點點水。

Now imagine pouring back and forth hundreds or even thousands of times over a period of two or three years (for a cellphone battery) or 10 to 20 years (for an electric car).

現(xiàn)在想象一下，在2、3年(手機電池)或10到20年(電動汽車)中來回傾倒數(shù)百次甚至數(shù)千次。

Over time, all the thousands of little and big things that go wrong add up to quite a bit of water going missing.

隨著時間的推移，所有的陰差陽錯都會導致相當多的水流失到杯子外面。

Even spilling a barely visible drop – say one-tenth of a milliliter – adds up to an entire liter if it happens 10,000 times. That doesn't even include the possibility of one cup failing in some way that loses even more water – like springing a leak or heating up and causing evaporation.

即使只是溢出幾乎不可見的水滴——比如十分之一毫升——如果發(fā)生了10000次，就會變成一升。這甚至還沒有計算進蒸發(fā)之類的影響。

Just as water inevitably goes missing when pouring from one cup to another, more energy is required to charge the battery than it actually stores, and less energy comes out than is stored in it. The proportion of wasted energy to stored energy grows over time.

就像把水從一個杯子倒到另一個杯子時，水不可避免地會有損失一樣，為電池充電所需的能量比實際存儲的更多，并且電池可用的能量比儲存在其中的更少。浪費掉的能量與儲存能量的比例隨著時間的推移而增長。

The ConversationIn fact, the more you use a battery, the more energy gets wasted, and the sooner the battery will reach a point where it's dead and can't usefully be recharged.

換句話說，你使用電池的次數(shù)越多，浪費的能量就越多，電池就會越早進入僵死狀態(tài)，無法進行充電。

I and others are studying ways to have those discharging-recharging cycles run more smoothly to reduce the amount of waste, but the second law of thermodynamics will always make sure that there's no way to get rid of it entirely.

我和其他人正在研究如何讓電池放電—充電循環(huán)得更為順暢地以減少浪費，但熱力學第二定律確保了沒有人能夠一勞永逸地解決這一問題。