Explain the basic building blocks of lithium ion batteries

Source: 2020 - 03 - 26 13:04 hits: lithium-ion battery in order to achieve the above functions, the basic component of lithium-ion battery needs to include several basic materials: positive active material, negative active material, electrolyte, isolation film. Let's take a quick discuss about the use of the materials. The positive and negative is not difficult to understand, in order to realize the movement of the charge, you need a potential difference of the positive and negative material, then what is the active material? We know that the battery is, in fact, electricity and chemical energy conversion to store and release energy. To do this, you need a 'easy' react with the material, a kind of easy to oxidation and reduction of material, a kind of can convert the energy of material, so we need a 'active material to do the positive and negative of the battery. As mentioned above, the material of choice for the lithium battery is our production, so why not use lithium metal as the activity of the electrode material? This is not the biggest energy density? As shown in the above, the oxygen ( O) , cobalt, Co) And lithium ( Li) Forming a very stable anode material structure ( Shown in the figure and the proportion of the arrangement is for reference only) Anode graphite, carbon atom also has a very stable layered structure. The positive and negative materials not only lively, but to have a very stable structure, to achieve the orderly and controllable chemical reaction. What is the consequence of unstable? Think of gasoline combustion or release energy when the bomb exploded, this is a kind of almost impossible to precisely control the chemical process, chemical energy into heat energy, therefore, the irreversible release at the same time. Exists in the form of metallic lithium is too 'lively, naughty children not obedient, mostly like to sabotage. Early research on lithium ion batteries are mainly concentrated in lithium metal or its alloy as the cathode, but for security reasons, they have to find better alternatives. In recent years, with the pursuit of energy density, the research direction in the 'resurrection of whole blood' trend, we will discuss later. Chemical stability, in order to achieve the energy storage and release process is the safety of the battery charge and discharge cycle and long life, we need a kind of electrode material, it is in need of reactive, when needed is stable. After long-term research and exploration, found several lithium metal oxides, such as lithium cobalt oxide, lithium manganese, lithium iron phosphate, acid titanate material such as lithium, nickel cobalt manganese three yuan, as the positive or negative of battery active substances, to solve the above problems. As shown, olivine structure of the lithium iron phosphate is also a very stable structure of the anode materials. , in the process of charging and discharging lithium ion in the case of does not cause the collapse of the lattice, stripped. In addition, there are also metal lithium batteries, but trivial compared with lithium ion battery, the development of the technology to serve the market in the end. In solving the problem of stability, of course, at the same time, also brought serious' side effects', the proportion of the lithium as an energy carrier has fallen dramatically, energy density decreased by a majority of orders of magnitude. Negative usually choose graphite or other carbon materials as active substances, which comply with the above principles. Requirement is a good energy carrier, is relatively stable, relatively rich reserves, is advantageous for the mass production. Carbon is a relatively optimal solution. Of course, this is not the only solution, and negative material has been widely studied, will discuss later. What's the electrolyte used for? In layman's terms, is the inside of the swimming pool 'water', lithium ion can swim free, so the higher ionic conductivity, the smaller the resistance ( Swimming) , electronic conductivity ( Insulation) The smaller, chemical stability, Stability) The better, thermal stability, Security) The better, give a person with wide potential window. Based on these principles, after a long time of engineering exploration, it was found that the organic solvent, high purity lithium electrolyte salts and the necessary raw materials such as additives, under certain conditions, according to a certain proportion of the electrolyte. Organic solvent with PC ( Propylene carbonate) 、EC( Ethylene carbonate) 、DMC( Dimethyl carbonate) 、DEC( Diethyl carbonate) 、EMC( Ethyl carbonate) Such as material. Materials such as lithium electrolyte containing LiPF6, LiBF4.