Batteries are everywhere in everyday life. Everyone can't live without their smartphone these days, but often complains about the battery life. In addition to phones and computers, there are many common power tools, toys or robots for young people and children, and even importantly, electric cars that require batteries at their core.
In addition to these familiar items, every other aspect also requires the use of batteries. For example, there are some patients installed pacemakers, pacemaker battery life and the patient's quality of life has a great relationship, because the battery runs out, you need another surgery specifically to replace the battery; if you want to use wind, solar or other renewable energy, you need to have a good grid energy storage capacity; of course, there are space satellites, these require battery technology.
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The ubiquitous battery
Frog: the big contributor to the invention of batteries
Battery technology is so important, how was it invented?
In 1786, there was an anatomist named Galvani at the University of Bologna, Italy, who found that when the metal scalpel touched the frog's muscles, the frog would jump and its legs would have spasms. This discovery was so surprising that he thought there was bioelectricity here.
In the 18th century AD, people's knowledge of electricity mainly came from frictional electricity and natural lightning, so the previous phenomena related to electricity, such as fur friction and Leyden bottles, were all static electricity. The discovery of the same phenomenon on the frog's leg as frictional electricity was indeed surprising at that time, and after the publication of this result in 1791, it attracted a lot of attention.
For example, it attracted the attention of another Italian university professor Voda. Voda repeated and tested Galvani's experiment, and after repeating it many times, he thought: the phenomenon of frog leg spasm, could it be unrelated to biology? The frog's leg was perhaps just a conductor?
To prove this idea, he removed all factors related to biology and used two different metals to generate electricity. Indeed, eventually he used different metals like active zinc and inactive silver or copper, immersed in cardboard with salt water, to produce a continuous electric current. This was the first battery in human history, the voltaic heap.
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Voda's hand-made "Voda pile", now in the Voda Museum, Italy, photo credit: Wikipedia
This research by Voda in 1800 brought the understanding of electricity from electrostatic to kinetic. Napoleon, who had conquered Italy at that time, recognized the importance of this research work and awarded Voda knighthood. To this day, the unit of voltage in physics, the "volt", is named after him.
Of course, the importance of this work was not only in winning the prize, but it laid the foundation for the emergence and development of electromagnetism. Faraday's electromagnetic induction experiments were done in 1831, and if there was no volt pile, Faraday would not have been able to do electromagnetic induction experiments, and mankind would not have been able to build a body of knowledge about electromagnetism.
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So Galvani is wrong? In fact, Galvani very adhere to their own views, he thought his experiment is no problem, and did a long time experiment to verify. Voda said that the current comes from two different metals, Gavani simply go to do an experiment, without any metal, he used the nerve of the frog to touch the frog leg muscles, found that the frog leg will still spasm, which shows that even if there is no metal, there is no external Voda electric pile, the creature will also respond to the electrical signal, there is still bioelectricity.
So Galvani is also right. This phenomenon, after years of intensive research, eventually gave rise to modern electrophysiology. We go to the hospital to do electrocardiogram, electroencephalogram, all related to electrophysiology, both the United States and China, are studying neuroscience, brain science, these signal transmission is based on the current generated by ions in the human body.
It is conceivable that the academic debate between Galvani and Voda during the turning phase from the eighteenth to the nineteenth century was very significant for the construction of the human knowledge system.
According to Voda's conclusion, as long as there are two different metals and a medium for conducting ions, many things can be used as batteries, and paper dipped in salt water can also be used to make batteries. A more interesting thing, we can also use fruit to make batteries, as shown below.
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Fruit battery
How is a battery charged and discharged?
One important thing since the 19th century is the development of lead-acid batteries, which were invented in 1859 and used in many scenarios such as electric bicycles, etc. The commercialization of lithium-ion batteries in 1990 was also an important milestone. Now there is a large battery family, in addition to the chemical batteries just shown, there are solar cells, temperature difference batteries, nuclear batteries, fuel cells, biological batteries, which like solar cells, temperature difference batteries belong to the energy conversion device, just mentioned chemical batteries if the rechargeable batteries, are storage batteries.
How does the battery work? We understand through the lithium-ion battery. The universal rocking chair lithium-ion battery, its working principle can be done through two diagrams to do some rough understanding.
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The working principle of the "rocking chair" lithium-ion battery
The upper right corner of the left diagram shows the state of the battery is empty, indicating that it is fully discharged, that is, discharged. This video to demonstrate the process of charging in the middle, what happened inside the battery. We pay attention to a few points, the red particles represent lithium ions, the blue particles represent the electrons generated inside. You can see the electrons on the outside of the battery, from the right to the left, lithium ions from the inside of the battery from the right to the left. The process of going to the left is actually the process of charging.
Correspondingly, the diagram on the right shows the process of discharging, where the lithium ions move inside the battery, going from the left to the right, and the electrons move in the external circuit, also going from the left to the right. This is the mechanism of its charging and discharging process.
How can such a process of moving back and forth store energy and how does this energy come about?
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The mechanism of energy storage in a battery
Let's look at the energy space, using a pool as an analogy. The left side is the negative pole, the right side is the positive pole, the green like water is lithium ions or electrons, the initial state is full of energy.
At the beginning is the discharge process, these higher energy electrons or lithium ions to put its energy away, between the two electrodes gradually flattened, energy gradually flattened, which is a spontaneous process.
Charging time, then through the external electricity to store energy into the lithium ions and electron potential energy increases, it will be charged with energy. Such a charging and discharging process, electrons and ions in different positions, but its energy has increased and decreased, this is the entire lithium-ion battery storage energy working principle.
Seven processes to forge the lithium-ion battery
After knowing this principle, and then look at so many lithium-ion batteries, how it is produced?
The first process of lithium-ion battery production is to mix the slurry, mixing the active electrode materials, conductive additives, and adhesives together, where there is a mixer to mix it into a uniformly dispersed slurry. The second step is coating, applying the black slurry to the collector fluid of the electrode sheet. The third step is cutting, where the coated pole piece is cut into the desired shape.
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This is the pole lug, the ear of the pole piece, is the place where the electricity is led out, the pole lug is often the cause of battery problems, as you know, some years ago Samsung cell phone battery explosion, after detailed investigation, found that the problem in the pole lug has the possibility of short circuit, which eventually led to the battery explosion.
The next step is to stack these batteries, just talk about the voltage is not enough when I stacked it a little more, in fact, the same inside the battery, in the internal also need to store more electricity into, so to stack a lot of pieces. The fifth step is to put the stacked pieces into an outer shell and put them into a bag. The sixth step is to fill the bag with electrolyte, which is the medium for ion conduction, just like the medium of lemon in the fruit battery. Finally, the battery is encapsulated and taken to be tested or used.
As you can see, there are many steps involved in the production of batteries in a factory, from materials, equipment, processes to automation control.
Battery life, safety and other dilemmas: Can cutting-edge research solve them?
What is current battery research doing? We have seen that many batteries can be produced through automated factories, so what are some of the problems with the current batteries and why do research?
The first research direction is to improve the energy density of the battery. If you drive your own electric car, you often encounter mileage anxiety, seeing that the battery shows that it is almost dead, but you have not yet reached the next charging station.
Look at a typical example, a five-seater car, the car weighs about 900 kg, if the range needs to reach 500 km, it is estimated that more than 400 kg of batteries are needed, that is to say, the battery will account for one-half to one-third of the weight of the car, for the whole transport, its energy efficiency is not high.
So I hope the energy density of the battery is higher, the more lithium ions can be accommodated per unit volume of material, the higher the voltage between the positive and negative electrodes, the higher the energy density of the battery. The smaller the weight of the body, the longer the range of the electric vehicle, so this is a very important direction.
The second research direction is to improve the safety of the battery. This photo shows Tesla's car in the process of driving, hit a sharp protrusion on the ground, which caused a serious safety accident.
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As you know, Tesla's battery is made on the chassis, although the safety performance protection is done, but in this accident, its battery was pierced by a sharp protrusion, which is equivalent to causing a short circuit of the battery, and eventually the battery caught fire, so the safety of the battery is very important.
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This is a safety test done in the laboratory, using two batteries with the same energy density (205Wh/kg) for pinprick experiments, one is the untreated battery, one is the battery after material improvement, the untreated battery had a serious explosion, the battery is 10Ah, an ordinary passenger car has about 400-500 such batteries.
As you can imagine, if there is a short circuit or impact to sharp objects and other extreme conditions, the battery with poor security is actually very dangerous, which is why it is necessary to continuously improve its energy density, but also improve its safety reasons, which is an important research direction of the battery.
Battery technology, can make human life greener
What kind of battery needs to be developed in the future? Need to make the battery industry greener, more environmentally friendly, more low-cost. The batteries just demonstrated need to use lithium, cobalt and nickel, and the distribution of lithium metal is not high on the periodic table, and cobalt and nickel are rare elements with limited reserves.
Like metallic cobalt, it is mainly produced in the DRC, which is a politically unstable country, so the source of the metal is problematic.
Therefore, the battery field is developing batteries made of materials containing other elements, such as sodium, magnesium, calcium and aluminum, which are more abundantly distributed, and even using organic materials and green biomass materials to make batteries.
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Battery development actually has many high level research tools. China's Scattered Neutron Source is located in Dongguan, Guangdong Province. China is the fourth country to have a Scattered Neutron Source after the United States, Japan, and the United Kingdom, and it is interesting that the first experimental data and the first published paper on the Scattered Neutron Source are related to lithium batteries.
There is also the Shanghai Light Source, including the synchrotron light source and free electron laser, as well as the European synchrotron light source, Suzhou's vacuum interconnection on the large device has a lithium research platform, and Japan's super light source spring-8.
You can see these battery studies and interesting and state-of-the-art tools will be used in the future.
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Electricity needs a more stable load load, both for use and transmission. But wind and solar are intermittent, and sometimes there are clouds drifting over and less power is generated, so how do you make these grids more stable? There is a need for powerful batteries for energy storage for peak and valley reduction (Note: peak and valley reduction is a measure to adjust the electricity load, so that power generation and electricity consumption tend to balance). So the future needs to use energy storage devices, electric vehicles can also be used as distributed energy storage devices, integrated into the entire smart grid.
In addition to renewable energy, the future of human society will also be more intelligent, now everyone is talking about 5G Internet of Things applications, artificial intelligence and supercomputing, etc.. In fact, many mobile devices, smart homes, and cars on the road will communicate with each other and exchange information. Not only the interconnection of energy, but also the interconnection of information, all the objects and devices in the interconnection, need batteries, without batteries can not work, batteries can make the future greener, more intelligent, more mobile.
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