Lithium-ion batteries do not use lithium in metal form, but if they are repeatedly charged and discharged over a long period of time, whisker-like lithium crystals will form on the surface of the negative electrode. Although the risk of such crystals reaching the positive electrode and short-circuiting is not high, it is not absolutely impossible, and until now, no way has been found to completely suppress the formation of such crystals.

Therefore, even if the battery itself does not have any quality problems, accidents such as gas, heat and fire will occasionally occur.

So this also makes the mobile phone manufacturer very difficult, if I use the mobile phone to catch fire, burn the belly, I must complain to the manufacturer for compensation, the manufacturer's heart must be 10,000 grass mud horses galloping by, he wants to say that this is your own improper use, but he really can't say it. ”

Speaking of this, the next student raised his hand, Liu Yuan nodded,

"Teacher, my family sells mobile phones, I don't agree with what you just said, our family sells major brands of mobile phones, and there are basically no customers from other brands who come to say that the battery explodes, but Samsung, every time a new product is released, it will always blow up several times, how can this be explained?"

Liu Yuan smiled, "That's, that's its own problem, in order to pursue a large screen and ultra-thin, they have put too much burden on the battery, and the battery that has not undergone a complete test can only be applied to the mobile phone, this kind of thing will happen."

In general, lithium-ion batteries are very complex, and the composition and structure of batteries vary greatly depending on different uses and different manufacturers.

For example, the lithium-ion batteries used in hybrid vehicles are very different from the positive and negative electrode materials used in the lithium-ion batteries of mobile phones. In recent years, some lithium-ion batteries used in mobile phones have adopted new negative electrodes such as silicon monoxide and alloys, and the capacity has been significantly improved.

In addition, some batteries for electric vehicles have begun to use nano-scale lithium titanate as the anode, which is lower than the previous carbon anode, although the capacity has decreased, but the safety is higher, after all, car safety is more related to life.

On the other hand, the safety protection of batteries also varies.

Generally speaking, lithium-ion batteries have a built-in electronic circuit, which can detect the voltage during charging and discharging and the internal temperature of the battery, and cut off the circuit when it reaches a certain dangerous value. Therefore, it is dangerous to take the lithium-ion battery to another device that is different from the original equipment and use it repeatedly. In most cases, in order to prevent the mixing of lithium-ion batteries, batteries of different shapes and sizes are designed depending on the device.

Speaking of which, I would like to remind the students not to borrow other people's chargers, but to borrow and use a brand, this is because, in order to charge the battery safely, the charger is generally designed with a check circuit, which can obtain information on the battery status and temperature in time to prevent overcharging, and its function is usually only the best effect on the battery that meets the specifications of each manufacturer.

The trend around the world is now clear, and both solar energy and electric vehicles are bound to be the general trend, but they both face a common problem, that is, the need for a large number of secondary batteries. Without batteries, solar energy can't store electricity, and electric cars can't run.

Of course, lithium-ion batteries can do this job, although its reserves are still relatively rich, but it is a rare metal after all, and the demand for lithium resources is huge, taking traditional lithium-ion batteries as an example, the number of lithium-ion batteries required for an electric vehicle is equivalent to 10,000 mobile phones. Therefore, lithium reserves will seriously hinder the development of solar energy and electric vehicles.

In this case, some scientists have set their sights on sodium, which is similar to lithium.

However, since the ionization tendency of sodium is not as strong as that of lithium, the voltage of the battery will be 0.3V lower than that of lithium, resulting in insufficient starting power, and compared to lithium, the volume of sodium ions is twice that of lithium, and the atomic weight is three times that of lithium, so sodium is not as good as lithium in terms of energy density.

However, sodium also has advantages, that is, it is rich in resources and cheap, and the reserves of sodium are more than 100 times that of lithium, which can be directly extracted from the table salt sodium chloride we use through electrolysis.

Therefore, for the large secondary batteries used in automobiles and natural energy power generation, it is still very attractive to choose sodium as the electrode, of course, the larger the volume of the secondary battery, the stronger the superiority of the sodium-ion battery.

Sodium-ion batteries are "aqueous sodium-ion batteries", that is, aqueous solutions are used in the electrolyte, and iron compounds and organic compounds are used in the positive and negative electrodes.

Sodium-ion batteries are already being developed around the world, and they are being used on a large scale to store the amount of electricity left over at night and to regulate the rapid changes in electricity such as wind and solar power generation.

Next, let's talk about the charging of batteries, the process of battery charging, which is to have a chemical reaction opposite to the discharge reaction inside the battery, and restore the components inside the battery to the original state before use.

That being the case, then why are there disposable batteries?

In fact, they are not completely chargeable, for alkaline dry batteries and zinc-manganese dry batteries, the current input to the battery can also make the primary battery also recharge, which can charge part of the battery.

However, in the process of charging reaction, hydrogen or chlorine and gas will be produced, and because disposable batteries are designed according to disposable light, its structure can not withstand the pressure of the gas generated after charging, and the result is that a series of unexpected problems such as explosion and heat release caused by the increase in internal pressure are likely to occur after charging.

I still remember when I was a child, there was a very fun toy called a four-wheel drive, I don't know if you know?

Four-wheel drive vehicles are driven by motors, and the motors are driven by batteries.

If the rechargeable battery is very expensive, I was 1 yuan a day pocket money, if you buy a battery, this must not be beaten to death, so you can only buy a cheap 555, but 555 will be finished in a while, so I often borrow the charger of rich classmates, charge for half an hour, the four-wheel drive car can be galloping again, but basically the second time to recharge it will not work. ”

Speaking of this, Liu Yuan magically took out a beautifully shaped four-wheel drive car, took out two dry batteries and installed them, pressed the switch, and the toy car immediately made a whining mechanical friction sound, scurrying under the students' chairs.

These post-10 children have hardly played with this kind of retro toy, one by one, their eyes are wide-eyed, as if they are full of interest in discovering a new continent, the motor of the four-wheel drive car has been modified, and the dry battery is exhausted after a few minutes of running, and the more they run, the slower they run, and finally stop.

Seeing this, Liu Yuan took out the dry battery charger he picked up from Xianyu, verified the theory just mentioned on the spot, and combined practice with theory to deepen the children's understanding.

"Let's talk about the capacity of the battery, if I guess correctly, everyone should have a mobile phone and a power bank, and they have an intuitive impression of the capacity described above.

The capacity of the battery is expressed in terms of how many milliamps of current flows through how many hours, the unit is recorded as mAh, mA stands for milliamps, and h stands for hours.

NiMH batteries are generally marked with the words 1000mAh or 2500mAh, and this 1000mAh means that it can be discharged for 10 hours with a current of 100 mAh.

The capacity of lithium-ion batteries installed in today's smartphones is generally 2000-3000mAh, however, the standby time felt when using the mobile phone is not only determined by the capacity of the battery, but also a very important point, which is how to start the unit inside the mobile phone energy-saving, which depends on the wisdom of different brands of mobile phones.

As for what the future battery will look like, this is the direction that X company is researching, and I can tell you that environmentally friendly batteries will be a major trend, so the future battery may abandon metal, as for what materials to replace, it is likely to be polymers, or it may be substances that we can't think of now.

Finally, batteries have their limits, and that limit is the heat energy of fossil fuels when they are burned. At the same time, batteries will also be eliminated in the future, because in the future, through various external stimuli such as light, heat, and pressure, we can completely achieve the use of electrical energy, just like the legendary Atlantis, the entire city-state uses a solar-like device.

Now it seems like a myth, but Arthur C. Clarke tells us that any advanced technology is nothing like magic at first glance. ”

Liu Yuan spoke for more than an hour in a forty-five-minute class, but the students did not have the slightest dissatisfaction with the class, and listened with great interest, and finally when the class ended, a sturdy student with a sturdy physique and a childish face raised his hand and asked: "Teacher Liu, I often surf the Internet, and I saw a report that Maple Leaf Country detained you to rob you of the super battery technology in your hand, I want to ask, what should I do?"

Liu Yuan smiled, "Do you like their movies?"

The strong guy nodded.

"But we can't compare at this stage, what should we do?"

The strong guy thought for a while, "Study hard, innovate, and then surpass them." ”

"No, just smash them and grab people. ”

——

After work that day, Yang Pingfan saw Wu Qifeng standing at the door of the company and looking around, so he stepped forward to say hello, it turned out that the car was broken.

"Get in the car, I'm fine anyway, I'll give you a ride. ”

"How embarrassing is this, I've already called Didi......"

"Let's go, let's go, besides, I haven't gone to your house yet!"

Wu Qifeng was not hypocritical, got in the car, and told Yang Pingfan an address.

Wu Qifeng's house is in the suburbs, following the map navigation, Yang Pingfan's car stopped in front of a small auto repair shop, "Yo, I didn't expect you to open an auto repair shop." ”

Wu Qifeng scratched his head, "The old man opened it, and the daughter-in-law is also here to help, come in and sit down and have a cup of tea." ”