Power batteries are widely used in new energy vehicles, which can be divided into secondary batteries (including lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, lithium batteries) and fuel cells.
Lithium batteries are usually divided into two categories according to the different materials used in the positive and negative electrodes.
Lithium metal batteries, that is, the use of manganese dioxide as the positive material, lithium metal or its alloy metal as the negative material battery; lithium ion batteries, the use of lithium alloy metal oxide as the positive material, graphite as the negative material battery.
Lithium metal batteries are not stable enough and cannot be charged, so they do not belong to the secondary battery. For new energy vehicles, we usually say lithium batteries, lithium-ion batteries.
The lithium-ion battery is mainly composed of four parts: positive electrode (containing lithium compounds), a negative electrode (carbon materials), an electrolyte, and diaphragm.
When the battery is charged, the lithium atoms on the positive electrode are ionized into lithium ions and electrons (de-embedding), and the lithium ions move through the electrolyte to the negative electrode, where they get electrons and are reduced to lithium atoms embedded in the micro-pores of the carbon layer (insertion);
When the battery is discharged, the lithium atoms embedded in the carbon layer of the negative electrode lose electrons (desertion) and become lithium ions, which move back to the positive electrode through the electrolyte (embedding);
The charging and discharging process of lithium battery is also the process of lithium-ion embedding and de-embedding between positive and negative electrodes, accompanied by the embedding and de-embedding of equal amounts of electrons. The higher the number of lithium ions, the higher the charge and discharge capacity.
Classification
Due to the different cathode materials, lithium-ion batteries are mainly divided into: lithium iron phosphate (LFP), lithium nickel oxide (LNO), lithium manganate (LMO), lithium cobaltate (LCO), lithium nickel cobalt manganate (NCM), nickel cobalt aluminum acid ternary lithium (NCA), and negative electrode materials mainly use graphite carbon materials.
Lithium cobaltate, as the originator of lithium batteries, of course, may also be used as a power battery to test the water first, first used in the Tesla Roadster, but because of its cycle life and safety are low, it has proved that it is not suitable as a power battery. In order to make up for this shortcoming, Tesla uses the battery management system that claims to be very good to ensure the stability of the battery. Lithium cobaltate currently has a large market share in the 3C field.
The second is lithium manganate battery, mainly first proposed by the battery company AESC, this AESC can not be small, is a joint venture between Nissan and Japan Electric Corporation (NEC). Lithium manganese acid representative model is for the Nissan LEAF, due to its low price, medium energy density, safety is also general, with the so-called better overall performance. As the saying goes, success is also a failure, is also because of this lukewarm characteristic, it's gradually replaced by new technologies.
Next is lithium iron phosphate, as BYD's main, its good stability, long life, and cost advantages, especially for the need for frequent charging and discharging plug-in hybrid vehicles, but its disadvantage is the general energy density.
Finally, the ternary lithium battery, as the rising star, energy density can be very high, but the safety is relatively poor. For pure electric vehicles with range requirements, its prospects are broader and is the mainstream direction of the current power battery.
