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Lithium batteries explode all the time. Why not use cheap, heavy, safe lead-acid

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2023/10/20 14:34:06

More than half a year did not seriously write popular science answer, science and technology plate is really more and more depraved, how simple question is no one said clearly, sorry.


Interests: Currently involved in the lithium project, the specific direction is secret, there is no need to speculate too much.


One by one.


1, for the battery, is safety the most important?


Yes, there is no security, all kinds of functions are in the water. In fact, lithium batteries can begin to be practical, but also because the safety has reached a level acceptable to the public.


For today's battery products, "lithium battery" is not a very correct name, which I explained many times when the 2019 Nobel Prize in Chemistry was awarded. The "lithium battery" that we commonly use now is actually "lithium-ion battery", and the real lithium battery is currently only used in some special occasions. The difference between the two, from the principle or the difference is relatively large, lithium-ion battery is essentially lithium ion from high concentration to low concentration environment, thus forming a current, this type of battery is a concentration battery, and lithium battery is lithium metal as a negative electrode, REDOX reaction after the formation of current, and the general zinc-manganese dry battery principle is the same.


The energy density of lithium batteries is far higher than that of lithium-ion batteries, but the number of cycles is low. However, in life, almost only lithium-ion batteries and not lithium batteries, the core reason is that lithium batteries are very unsafe, because lithium metal may react when it meets water and oxygen, and then heat, and finally cause an explosion. Maybe the public thinks that lithium-ion batteries are not safe, and blow up every three times, but if we use lithium batteries in the real sense, now this accident is not enough to see.


It is precisely because of poor safety that the cost of developing lithium batteries, even for special uses, is now surprisingly large. Two weeks ago, I just investigated in a factory. In order to design a special lithium battery, the factory needs a full dehumidifier, and the electricity cost is nearly 30,000 yuan per day. Even so, the yield is still very low, only thousands of small cells are produced every day, and the production cost is as high as 20 yuan per watt hour. For comparison, the production cost of conventional lithium-ion batteries is no more than 1 yuan.


Therefore, safety is life, life is gone, money will not earn, in order to safety, the price to pay is also amazing. Lithium-ion batteries can be widely used because their safety problems exist, but they do not threaten their great value.


2. Is the lead-acid battery safe?


Safe by lithium-ion battery standards. For example, many lithium-ion batteries can't go through puncture, a needle down, the battery will explode, but lead acid does not have this problem.


This is because lithium-ion batteries are usually filled with flammable electrolyte, to be precise, conductive salts and flammable solvents, which include carbonate esters, ethers, esters, and so on. Once the battery is pierced, the positive and negative electrodes are directly connected, that is, there is a short circuit, then the battery quickly discharges, the solvent will be ignited, and finally may cause an explosion. The details of this principle is not one or two words clear, if you want to understand the details, it is recommended to learn from the basic structure of the battery, I am here to post a picture, is the recent lithium battery safety conference at Tsinghua University teacher Wang Li courseware.


Lead-acid batteries, of course, do not have this problem, its electrolyte is sulfuric acid, the specific principle of middle school have learned. So, it makes sense to say it's safe to stab, but would we think it's safe to stab a lead-acid battery with a needle?


Obviously not. Can a sulfuric acid leak be a safe thing? What's more, in the normal use process, lead-acid batteries will release sulfur-containing gases, and there is always a part of sulfuric acid that will be reduced to sulfur dioxide, which is also toxic. It doesn't matter on land, but imagine what would happen if these toxic gases couldn't be released in an underwater ship?


Therefore, whether the lead-acid battery is safe is completely said in the context of lithium-ion batteries, but its safety is not imagined to be high.


To give an inappropriate example, for "Yao Ming can play basketball" this proposition, we think it is true, because we default that this is said in the basketball field, but if Yao Ming one day to play that can not play Liu Fatty, Liu Fatty took him to visit the national table tennis training ground, a 17 or 18 years old young general, Wearing a sports T-shirt printed with "China" to Yao big man under the game: "Heard that Chairman Yao is very good at playing?" What do you think Yao Ming would say?


Therefore, safety is not just a dimension, lithium-ion batteries will explode when they are punctured, lead-acid batteries are punctured and corrosive, which are unsafe factors, but the explosion gives people a greater visual impact.


3. Can lithium-ion batteries be safe?


Agreed.


Today's lithium-ion batteries usually add flame retardants to prevent the electrolyte from burning due to short circuit and other reasons, which solves the safety problem to a certain extent.


Of course, there is also a more direct, solid electrolyte, completely non-combustible will not explode.


In the previous picture, our most recent battery puncture test was carried out by a third-party testing institution.


As you can see, the fully charged battery has no reaction at all after the acupuncture.


Because of sensitive industry confidentiality requirements, I can't show more information, but in fact this battery also passed the drop, squeeze and other tests, but it is not the safest, and one can be thrown in the oven fine, so you can imagine what they can be used for.


Now the question is, why do we have the impression that lithium-ion batteries are very unsafe and prone to explosion?


In the past few years, the fire and explosion of mobile phones and cars are indeed memorable, and even industry insiders know that some accidents of energy storage power stations, but it is really fueled by electric bicycles.


In these two days, an electric bicycle tragedy in Hangzhou, posted a link:


There was a loud bang! Hangzhou, an electric car suddenly caught fire while driving, father and daughter were instantly surrounded by fire! Ten seconds later, a group of people rushed over... _ Tencent News


It was a terrible accident, worse than the one that happened in an elevator in Chengdu.


If the accident rate, electric bicycles are much higher than mobile phones and new energy vehicles, and mobile phones and cars are mostly charged when the fire, people may not be at the scene, but electric bicycles are often in the process of use suddenly caught fire.


The reason for this is largely due to cost compression. Taking the Hangzhou accident as an example, the battery of the electric bicycle was replaced, and the price was only 500 yuan. The battery used by the general electric bicycle is 48 volts 20 amps, and the energy is 960 watt-hours, which is nearly 1 KWH of electricity. The production cost of lithium-ion batteries in regular enterprises can be compressed to about 0.5 yuan per watt-hour, so if such a battery is produced by regular manufacturers, the cost of photocells will be at least 500 pieces, and then counting the battery management system, shell, wire and sales expenses and profits, can be controlled at 1000 yuan is very low. The actual price has to be around 1500 yuan. So, what is the origin of the 500 yuan battery?


I was going to go into a little more detail here, but I thought it might encourage criminals to find a way to make money, so forget it. Grey industry chain? Imagine it.


4, since lithium-ion batteries are prone to explosion because of extreme cost control, why not replace them with cheaper lead-acid batteries?


Okay, let's get to the heart of the matter.


Many people do not understand: since lithium-ion batteries are too expensive, and some people cut corners leading to easy fire, it is not good to simply use lead-acid batteries?


It's not impossible, but consumers don't pay.


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