"Lithium iron phosphate is good, but not as good as ternary batteries."
The power batteries of new energy vehicles can be divided into secondary batteries (including lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, lithium batteries) and fuel cells.
1. Working Principle
Firstly, the concept of lithium batteries is corrected. Lithium batteries are usually divided into two categories according to the materials used for positive and negative electrodes.
Lithium metal batteries are batteries that use manganese dioxide as cathode material and lithium or its alloy metal as cathode material. Lithium ion batteries use lithium alloy metal oxide as cathode material and graphite as cathode material.
Lithium metal batteries are not secondary batteries because their properties are not stable enough and they can not be charged. For new energy vehicles, what we usually call lithium-ion batteries is lithium-ion batteries.
Lithium-ion batteries are mainly composed of four parts: positive electrode (containing lithium compounds), negative electrode (carbon materials), electrolyte and diaphragm.
When the battery is charged, lithium atoms on the positive electrode ionize into lithium ions and electrons (deintercalation). Lithium ions move to the negative electrode through the electrolyte to obtain electrons, which are reduced to lithium atoms and embedded in the micropore of the carbon layer (insertion).
When the battery discharges, the lithium atom embedded in the carbon layer of the negative electrode loses electrons (unplugged) and becomes lithium ion, which moves back to the positive electrode (embedded) through the electrolyte.
The charging and discharging process of lithium batteries is the process of lithium ion embedding and de-embedding between positive and negative electrodes, accompanied by the embedding and de-embedding of equivalent electrons. The more lithium ions are, the higher the charge-discharge capacity will be.
Due to the different cathode materials, lithium-ion batteries are mainly divided into: lithium iron phosphate (LFP), nickel acid (LNO), lithium manganate (LMO), lithium cobalt oxide (LCO), lithium nickel cobalt manganate (NCM), lithium nickel cobalt aluminate (NCA), and graphite-carbon materials are mainly used as cathode materials.
3. Technical route
First of all, lithium cobalt oxide, as the originator of lithium batteries, of course, may also be used as power batteries to try water first, first used in Tesla Roadster, but because of its low cycle life and safety, it has been proved that it is not suitable for power batteries. To compensate for this shortcoming, Tesla uses what is known as the world's top battery management system to ensure the stability of batteries. At present, lithium cobalt has a large market share in 3C field.
The second is lithium manganate battery, which was first proposed by battery company AESC. This AESC is a joint venture of Nissan and Japan Electric Co., Ltd. (NEC). Lithium manganate is the representative of Nissan Leaf. Because of its low price, medium energy density and general safety, it has so-called better comprehensive performance. The so-called "success or failure" or "failure" is also due to this tepid nature, which is gradually replaced by new technologies.
Secondly, lithium iron phosphate, as the main battle of BYD, has good stability, long life and cost advantages, especially for plug-in hybrid electric vehicles which need regular charging and discharging, but its disadvantage is the general energy density.
Finally, the ternary lithium battery, as a rising nova, has the highest energy density, but its safety is relatively poor. Pure electric vehicles with required range have a broader prospect and are the mainstream direction of power batteries at present.
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