手机电池为何越用越不耐用？
Why Your Phone Battery Gets Worse Over Time
刘立军 供稿
TRANSCRIPT
A drop of gasoline, a match, and a battery, all store energy — but, after each expends its energy, only the battery is recyclable. That’s because, chemically speaking, a dead battery is actually not that different from a fresh one.
Most of the batteries we use today take advantage of the fact that some metals like to release electrons and others like to accept them. For example, in a typical alkaline double-A battery, zinc metal reacts with hydroxide ions, changing into zinc oxide and releasing electrons at the negative terminal. The electrons travel through, say, a light bulb, and then return to the battery at the positive terminal, where they’re accepted by manganese dioxide.
Different batteries use different combinations of metals, and sometimes non-metals like graphite, but the basic idea is to use a pair of chemical reactions to generate a stream of electrons.
Almost all batteries, even single-use batteries, are theoretically rechargeable. That’s because the metals and other chemicals are still right there. That’s very different than in, say, gasoline, where the liquid hydrocarbon molecules are converted to gases. You can’t convert exhaust back into gasoline, but, with some work you can convert, say, zinc oxide back to zinc. So then what’s the difference between these and these?
The short answer is that trying to recharge a single-use battery doesn’t just force these reactions to run in reverse. It also results in a bunch of side reactions that produce useless contaminants, reducing a battery’s capacity; and it could even damage the internal structure of the battery, leading to a loss of electrical contact and failure.
Rechargeable batteries are engineered to avoid these issues. Look at this lithium-ion battery. Both sides have an atomic-level structure that you can imagine as lots of docks. So when the battery is powering something, the lithium “ships” give up their electrons to power the circuit, and then sail over to the other side of the battery, dock in an orderly, organized way, and meet up with their now-lower-energy electrons.
When the battery is being charged, the opposite happens. Over the course of hundreds, sometimes thousands, of charge cycles, some of the lithium ion ships sort of veer off course and engage in side reactions, producing stuff that increases the internal resistance of the battery, which in turn makes it lose efficiency and power until it inevitably dies. Even when that happens, you can bring dead batteries back to life — whether they’re rechargeable or not — by recycling them.
The heart of most battery recycling is a process called smelting, which is basically just melting the metallic parts. This drives off impurities, returning metals back to their initial, orderly state. Unfortunately, in many countries you can’t just toss household batteries in with your regular recycling. You have to take them to a battery collection point or recycling center. Same goes for more complicated rechargeable batteries: you need to bring them to a collection point or send them back to the company you bought them from.
It’s a pain, but absolutely worth the time and effort, because recycling batteries is critical. Not only does it prevent potentially toxic battery metals from leaking into the environment, it conserves scarce and vital resources.
Earth has about 22 million tons of lithium — enough for about 2.5 billion EVs. That sounds like plenty, but it’s only 25% higher than the number of EVs experts believe it’ll take to reach net zero emissions by 2050, and that doesn’t even account for laptops, phones, and anything else that uses a lithium-ion battery. Currently, though, most lithium-ion batteries are not manufactured with recycling in mind. The designs are intricate and non-standard, and the components are held together by almost indestructible glues. So today, less than 5% of lithium-ion batteries are recycled.
Regulations that clearly define who is responsible for a spent battery and what should happen to it can boost recycling dramatically. For example, lead-acid batteries are generally subject to stringent regulations and are recycled at much higher rates than lithium-ion batteries.
Over the next century, we’ll need to recycle huge numbers of EV batteries, so scientists are working on making the battery recycling process cheaper and more environmentally friendly. Smelting uses a lot of energy and, depending on the type of battery, can release harmful by-products.
In addition to regulations, industrial processes, and our own individual choices, battery tech will also continue to evolve. There are proof-of-concept batteries being developed that can convert physical force, ambient sound, and even pee into electricity. But if your top priority is to make your number one source of power, number one, sorry to say, but urine for a long wait.
VOCABULARY
1. alkaline adj. (chemistry 化) having the nature of an alkali 碱性的
2. hydroxide ions 氢氧化物离子
3. graphite n. a soft black mineral that is a form of carbon. Graphite is used to make pencils, to lubricate machinery, and in nuclear reactors. 石墨
4. contaminant n. (technical 术语) a substance that makes sth. impure 致污物；污染物。例如：Filters do not remove all contaminants from water. 过滤器无法过滤掉水中的所有污染物。
5. smelt v. to heat and melt ore (= rock that contains metal) in order to obtain the metal it contains 熔炼，提炼（金属）。例如：a method of smelting iron 一种炼铁方法
6. impurity n. a substance that is present in small amounts in another substance, making it dirty or of poor quality 杂质。例如：A filter will remove most impurities found in water. 过滤器会滤掉水中的大部分杂质。
7. indestructible adj. that is very strong and cannot easily be destroyed 不可摧毁的；破坏不了的。例如：an indestructible bond of friendship 坚不可摧的友谊纽带
8. stringent adj. very strict and that must be obeyed 严格的；严厉的。例如：stringent air quality regulations 严格的空气质量管理条例
9. ambient adj. relating to the surrounding area; on all sides 周围环境的；周围的。例如：ambient temperature / light / conditions 周围的温度 / 光线 / 环境
QUESTIONS
Listen to the news and choose the best answer to each question you hear.
1. What is the role of metals in batteries as mentioned in the passage?
A. To physically form the battery structure.
B. To facilitate the release and acceptance of electrons.
C. To change zinc oxide back to zinc.
D. To initiate a chemical reaction with hydroxide ions.
2. According to the passage, what happens when one attempts to recharge a single-use battery?
A. The stored energy cannot be fully recovered.
B. It completely alters its chemical composition.
C. Reactions are forced to run in reverse leading to side reactions that produce contaminants and damage the internal structure.
D. It ceases to function immediately.
3. According to the passage, what prevents household batteries from being disposed of with regular recycling?
A. They contain hazardous chemicals.
B. They do not contain any recyclable materials.
C. Their small size makes them unsuitable for recycling.
D. They necessitate special recycling centers or collection points.
4. Based on the passage, why is the low recycling rate of less than 5% for lithium-ion batteries problematic?
A. Earth's lithium resources are finite and must be conserved.
B. Lithium-ion batteries pose environmental hazards.
C. Disposed lithium-ion batteries occupy significant landfill space.
D. The cost associated with the recycling process of lithium-ion batteries is high.
5. What solution does the passage suggest could increase the rate of battery recycling?
A. An increase in the production of single-use batteries.
B. Implementation of clear regulations defining the responsibility for spent batteries.
C. A decrease in overall battery usage.
D. Innovation in new battery technologies.
KEY
1. What is the role of metals in batteries as mentioned in the passage?
A. To physically form the battery structure.
B. To facilitate the release and acceptance of electrons.
C. To change zinc oxide back to zinc.
D. To initiate a chemical reaction with hydroxide ions.
【答案】B
【解析】细节题。文章中提到，“Most of the batteries we use today take advantage of the fact that some metals like to release electrons and others like to accept them”。
2. According to the passage, what happens when one attempts to recharge a single-use battery?
A. The stored energy cannot be fully recovered.
B. It completely alters its chemical composition.
C. Reactions are forced to run in reverse leading to side reactions that produce contaminants and damage the internal structure.
D. It ceases to function immediately.
【答案】C
【解析】细节题。根据文章的描述，“trying to recharge a single-use battery doesn’t just force these reactions to run in reverse. It also results in a bunch of side reactions that produce useless contaminants, reducing a battery’s capacity; and it could even damage the internal structure of the battery”.
3. According to the text, what prevents household batteries from being disposed of with regular recycling?
A. They contain hazardous chemicals.
B. They do not contain any recyclable materials.
C. Their small size makes them unsuitable for recycling.
D. They necessitate special recycling centers or collection points.
【答案】D
【解析】细节题。该文提到，“in many countries you can’t just toss household batteries in with your regular recycling. You have to take them to a battery collection point or recycling center”。
4. Based on the passage, why is the low recycling rate of less than 5% for lithium-ion batteries problematic?
A. Earth's lithium resources are finite and must be conserved.
B. Lithium-ion batteries pose environmental hazards.
C. Disposed lithium-ion batteries occupy significant landfill space.
D. The cost associated with the recycling process of lithium-ion batteries is high.
【答案】A
【解析】推理题。虽然没有直接提到这个原因，但从“Earth has about 22 million tons of lithium — enough for about 2.5 billion EVs”这段话我们可以推断出只有少量锂离子电池被回收是一个问题，因为地球的锂资源是有限的。
5. What solution does the passage suggest could increase the rate of battery recycling?
A. An increase in the production of single-use batteries.
B. Implementation of clear regulations defining the responsibility for spent batteries.
C. A decrease in overall battery usage.
D. Innovation in new battery technologies.
【答案】B
【解析】细节题。文章提到，“Regulations that clearly define who is responsible for a spent battery and what should happen to it can boost recycling dramatically”，所以明确规定用完的电池的责任人和处理方式的规定可以显著提高电池回收率。
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