The dazzling lithium battery black technology, the principle is ever-changing?

The history of human society's use of energy, from 4 billion years ago to 200 years ago, was the use of photosynthesis; Watt invented the steam engine, the internal combustion engine of the second industrial revolution, and humans began to use fossil energy such as coal and oil. Recently, mankind has paid attention to the comprehensive utilization of energy, requiring efficient energy collection, storage, and transportation.

Humans collect all energy and first convert it into electricity. Storage of electrical energy has become a top priority in the use of energy, which is dominated by electrochemical devices, from capacitors to batteries, to fuel cells, to supercapacitors. Different applications use different electrochemical devices.

Professor Luyunfeng said at the International Forum on Smart Energy that the types of batteries are varied, but the purpose is actually the same. They all want to make the power large, the capacity density high, and the life span long. How do you make the battery? Back in nature, because photosynthesis is the most primitive energy conversion process on Earth.

Sunlight decomposes water into electrons and protons in chlorophyll. Electrons have electron channels and protons have proton channels. Carbon dioxide is converted into hydrocarbon material by internal synthesis. The most important thing in this process is to have an independent proton and electronic channels.

This is the same for lithium batteries. Lithium-ion batteries were originally lithium iron phosphate versus graphite. Negative graphite, positive lithium iron phosphate. When discharged, the lithium embedded in the graphite loses electrons, becomes lithium ions, and runs out with iron phosphate to become lithium iron phosphate.

The relationship between lithium ions and electrons is interdependent. There is no ion without electrons, and there is no electron without ions. The slow speed between the two determines the power of the battery. In addition, the stability of lithium-ion channels and conductive lines affects battery life.

From this process, it can be seen that to make lithium-ion batteries into batteries with high energy density, high power, and long life, it is important to establish efficient and stable ion electron channels.

The establishment of an efficient and independent ion electron channel can work from the material. Lithium-ion battery materials are generally poorly conductive, while charcoal can increase conductivity; Lithium-ion conductivity is also not good enough, you can make the particles smaller so that lithium ions do not need to move too long distances, which is why the lithium battery electrode material on the market is smaller and smaller. In addition, small particles can make the structure more stable.

At present, most of the research direction of lithium batteries is also the same. Ions and electrons are required for electrode materials. The scientific solution is to use graphene, carbon tubes, and of course other carbon compounds. The material is then made into nanoparticles, or the nanowires are combined with carbon tubes so that the process of conducting electron ions can be achieved, and the structure can be made very stable.

Take nanowires as an example. Nanowires and composite structures that intersect with carbon tubes have very good conductivity and are excellent materials for supercapacitors. In order to make the ion conductivity faster, vanadium pentoxide is also used. It is a layered material and has a lot of space in itself. We can further expand the layer spacing from 0.35 nanometers to 0.45 nanometers. Lithium-ion runs faster. This complex can be used not only as a material for supercapacitors but also as a material for sodium batteries and sodium capacitors. After all, sodium is cheaper and far more abundant than lithium.

Nanoparticles are also common, but more research is done. In addition to mixing nanoparticles directly with carbon tubes, there is also a way to assemble small nanoparticles into spheres and carbon tubes. This structure allows the battery to have a higher doubling rate and longer life.

It is worth mentioning that nanoparticles are often made into oily, that is, natural water repulsion. The other is hydrophilic, which requires special treatment. Normally, carbon tubes are easy to adsorb acrylic acid, so when the nanoparticles are combined with carbon tubes, the carbon tubes can first adsorb a little acrylic acid.

In addition, there is a simpler method called spray drying. That is, the nanoparticles, carbon tubes, or conductive things are directly sprayed and dried to make particles. One advantage of this is that during the spray process, carbon pipes will be extended and materials such as iron oxide form a special structure so that the outside of the material is not conductive, but the interior has good electrical conductivity. This technical principle is as easy to industrialize as spray milk powder.

Battery materials not only have positive and negative poles, but electrolytes are also extremely critical. At present, researchers have developed an additive that can achieve the immobility of negative ions in the electrolyte, and only positive ions move. In this way, the rate of movement of lithium ions will be increased by geometric multiples, and the battery can be charged and discharged with high magnification to achieve fast charging.

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