The main components of lithium-ion batteries:
(1)Positive electrode-the active material mainly refers to lithium cobaltate, lithium manganate, lithium iron phosphate, lithium nickelate, lithium nickel cobalt manganate, etc. The conductive current collector generally uses aluminum foil with a thickness of 10--20 microns;
(2) Diaphragm-a special plastic film that allows lithium ions to pass through, but it is an electronic insulator. At present, there are mainly two types of PE and PP and their combination. There is also a type of inorganic solid diaphragm, such as alumina diaphragm coating is a kind of inorganic solid diaphragm;
(3) Negative electrode-active material mainly refers to graphite, lithium titanate, or carbon materials with a similar graphite structure. The conductive current collector generally uses copper foil with a thickness of 7-15 microns;
(4) Electrolyte-generally an organic system, such as a carbonate solvent with Lithium Hexafluorophosphate dissolved in it, and some polymer batteries use gel-like electrolyte;
(5) Battery case-mainly divided into hard case (steel case, aluminum case, nickel-plated iron case, etc.) and soft case (aluminum plastic film).
When the battery is charged, lithium ions are extracted from the positive electrode and inserted in the negative electrode, and vice versa during discharge. This requires an electrode to be in a lithium-intercalation state before assembly. Generally, a lithium-intercalation transition metal oxide with a potential greater than 3V relative to lithium and stable in the air is selected as the positive electrode, such as LiCoO2, LiNiO2, LiMn2O4.
As the material of the negative electrode, choose the intercalable lithium compound whose potential is as close as possible to the lithium potential. For example, various carbon materials include natural graphite, synthetic graphite, carbon fiber, mesosphere carbon, etc. and metal oxides, including SnO, SnO2, and SnO2. Tin composite oxide SnBxPyOz (x=0.4~0.6, y=0.6~0.4, z=(2+3x+5y)/2) etc.
The electrolyte adopts a mixed solvent system of LiPF6 ethylene carbonate (EC), propylene carbonate (PC) and low-viscosity diethyl carbonate (DEC) and other alkyl carbonates.
The diaphragm adopts polyolefin microporous membranes such as PE, PP or their composite membranes, especially the PP/PE/PP three-layer membrane not only has a lower melting point, but also has a higher puncture resistance, which plays a role in heat insurance.
The shell is made of steel or aluminum, and the cover assembly has the function of explosion-proof and power-off.
Characteristics of lithium iron phosphate batteries
1. Super long life
The cycle life of a long-life lead-acid battery is about 300 times, the highest is 500 times, while the cycle life of a lithium iron phosphate power battery is more than 2000 times, and the standard charge (5 hour rate) use can reach 2000 times. Lead-acid batteries of the same quality are "new half a year, half a year old, and half a year for maintenance", which can take up to 1 to 1.5 years, while lithium iron phosphate batteries will reach 7 to 8 years when used under the same conditions. Comprehensive consideration, the performance-price ratio will be more than 4 times that of lead-acid batteries.
2. Safe to use
Lithium iron phosphate completely solves the safety hazards of lithium cobalt oxide and lithium manganese oxide. Lithium cobalt oxide and lithium manganese oxide will explode in a strong collision and pose a threat to consumers` life and safety, while lithium iron phosphate has undergone strict The safety test will not produce an explosion even in the worst traffic accidents.
High current 2C can be quickly charged and discharged. With a dedicated charger, the battery can be fully charged within 40 minutes of 1.5C charging, and the starting current can reach 2C. Lead-acid batteries do not have this performance now.
3. High Temperature Resistance
The peak value of lithium iron phosphate electric heating can reach 350 ℃-500 ℃, while lithium manganese oxide and lithium cobalt oxide are only around 200 ℃. Wide operating temperature range (-20C--+75C), with high temperature resistance, lithium iron phosphate electric heating peak can reach 350 ℃-500 ℃, while lithium manganate and lithium cobalt oxide are only around 200 ℃.
4. Capacity
It has a larger capacity than ordinary batteries (lead-acid, etc.). Rechargeable batteries work under conditions that are often fully charged and not discharged, and their capacity will quickly fall below the rated capacity. This phenomenon is called the memory effect. Like nickel-metal hydride and nickel-cadmium batteries, there is memory, but lithium iron phosphate batteries do not have this phenomenon. No matter what state the battery is in, it can be charged and used at any time without having to discharge it before charging.
The volume of a lithium iron phosphate battery of the same specification and capacity is 2/3 of the volume of a lead-acid battery and its weight is 1/3 of that of a lead-acid battery. The battery does not contain any heavy metals and rare metals (the nickel-hydrogen battery requires rare metals), non-toxic (SGS certification), non-polluting, in line with European RoHS regulations, and is an absolute green battery certificate.
5. No memory effect
The performance of lithium power batteries mainly depends on the anode and cathode materials. Lithium iron phosphate has only appeared in recent years as a lithium battery material. The domestic development of large-capacity lithium iron phosphate batteries was in July 2005. Its safety performance and cycle life are unmatched by other materials, and these are also the most important technical indicators of power batteries. 1C charging and discharging cycle life is up to 2000 times. Single-cell battery will not burn or explode when overcharged at 30V. Lithium iron phosphate cathode materials make large-capacity lithium batteries easier to use in series. To meet the needs of frequent charging and discharging of electric vehicles. It has the advantages of non-toxic, non-polluting, good safety performance, wide source of raw materials, low price and long life. It is an ideal cathode material for a new generation of lithium batteries.
The positive electrode of the lithium battery is lithium iron phosphate material. This new material is not the previous lithium battery cathode material LiCoO2; LiMn2O4; LiNiMO2. Its safety performance and cycle life are unmatched by other materials, and these are also the most important technical indicators of power batteries. 1C charging and discharging cycle life is up to 2000 times. Single-cell battery will not burn or explode if the overcharge voltage is 30V. Piercing does not explode. Lithium iron phosphate cathode material makes it easier to connect in series to make large-capacity lithium batteries.
Adopting a new generation of electric vehicles with a new type of lithium iron phosphate battery as its power core has many characteristics and advantages:
1. The security is high
The lithium iron phosphate battery will not explode even if it is thrown into the fire. The high temperature stability can reach 400-500°C, which ensures the inherent high safety of the battery; it will not explode or burn due to overcharge, high temperature, short circuit, or impact. After strict safety testing, there will be no explosion even in the worst traffic accidents.
2. Long life and low cost
As a power battery, the service life (cycle performance) is closely related to the overall cost of use. Compared with the cycle life of an ordinary lithium battery of about 500 times, the lithium iron phosphate battery can be charged and discharged for 1500 cycles at room temperature, and the capacity retention rate is 95%. Above, and the cycle life of 50% capacity has reached more than 2000 times, the battery's continuous mileage life is more than 500,000 kilometers, and it can be used for about five years, which is 8 times that of lead-acid batteries and 3 times that of nickel-hydrogen batteries, which is cobalt. About 4 times that of lithium-acid batteries. In addition, the manufacturing cost itself is lower than that of ordinary lithium batteries, which will undoubtedly greatly reduce the use and maintenance costs of electric vehicles.
