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Lithium-ion battery composition Mar 09, 2018

When it comes to the composition of lithium-ion batteries, we all know that lithium is an integral part, yes, that is, the lithium in the periodic table of our chemical textbooks. But a complete lithium-ion battery is not only the only lithium, the following we come to talk about the lithium-ion battery with those things.


The basic composition of lithium-ion battery


Lithium-ion batteries need to contain several basic materials: positive active material, negative active material, separator, electrolyte. So what are these materials doing?

Positive and negative is not difficult to understand, in order to achieve charge movement, there is a potential difference between the positive and negative materials, then what is the active material? We know that the battery is actually the mutual conversion of electrical energy and chemical energy in order to achieve energy storage and release. To achieve this process, we need positive and negative materials are "easy" to participate in chemical reactions, to be lively, easy to oxidation and reduction, in order to achieve energy conversion, so we need "active material" to do the battery anode and cathode.


Electrolytes is doing? Popular speaking, is the "water" inside the swimming pool, so that lithium ions can swim freely, so, ionic conductivity is high (resistance to swimming small), electronic conductivity is small (insulation), chemical stability Better (stability overwhelm everything), thermal stability is better (all for safety), the potential window should be wide. Based on these principles, after long-term engineering exploration, people have found a certain proportion of electrolytes made from high-purity organic solvents, electrolyte lithium salts, and necessary additives and other raw materials under certain conditions. Organic solvents are PC (propylene carbonate), EC (ethylene carbonate), DMC (dimethyl carbonate), DEC (diethyl carbonate), EMC (ethyl methyl carbonate) and other materials. Lithium electrolyte has LiPF6, LiBF4 and other materials.


Isolation film is to prevent the positive and negative materials in direct contact and added, we hope to make the battery as small as possible, the stored energy as much as possible, so the distance between positive and negative electrodes is getting smaller and smaller, short circuit Become a huge risk. In order to prevent positive and negative material short circuit, resulting in the violent release of energy, you need to use a material to be positive and negative "isolated", and this is the origin of the isolation film. Isolation film needs to have good ion permeability, mainly to open the channel for lithium-ion, allowing it to pass freely, but also an electronic insulator, in order to achieve the insulation between the positive and negative. Currently on the market are mainly single-layer diaphragm PP, single PE, double PP / PE, three PP / PE / PP composite film.


In addition to the four main materials mentioned above, there is a need for other, indispensable materials to turn lithium-ion batteries from a laboratory "labware" into a commercially viable product.


We look at the positive electrode of the battery, in addition to the active material, the conductive agent and binder, as well as the substrate and current collector (positive electrode is usually aluminum foil). The binder should be "active" lithium metal oxide uniformly "fixed" in the positive base, the conductive agent is to enhance the conductivity of the active material and the matrix to achieve greater charge and discharge current, the collector is responsible for the battery Internal and external charge transfer bridge.


In addition to the above materials, a complete lithium-ion battery also includes insulation sheets, covers, pressure relief valves, housings (aluminum, steel, composite films, etc.) and other auxiliary materials.