Lithium batteries are one of the most commonly used battery types, although not for a long time, since their birth in 1970, with high energy density and long cycle life, they quickly occupied most of the electric vehicle battery market.
At present, electric vehicles equipped with lithium batteries are mainly two kinds of lithium iron phosphate batteries and ternary lithium batteries. So what is the difference between lithium iron phosphate batteries and ternary lithium batteries?
Ⅰ. Structural characteristics of cathode materials for ternary lithium batteries
A ternary polymer lithium battery refers to a lithium battery in which the positive electrode material uses a ternary positive electrode material of nickel cobalt lithium manganate or nickel cobalt lithium aluminate.
The ternary composite positive electrode material is made of nickel salt, cobalt salt and manganese salt as raw materials, and the ratio of nickel, cobalt and manganese in it can be adjusted according to actual needs. The battery with ternary material as the positive electrode is safer than lithium cobalt oxide battery.
1. Layered or tunnel structure to facilitate the deintercalation of lithium ions, and there is no structural change during the deintercalation of lithium ions to ensure that the electrode has good reversible performance;
2. The amount of intercalation and deintercalation of lithium ions in it is large, and the electrode has a high capacity, and the free energy of the electrode reaction does not change much when the ternary lithium battery is deintercalated, so as to ensure the stable charging and discharging voltage of the battery;
3. Lithium iron phosphate UPS should have a large diffusion coefficient in it, so that the battery has good fast charge and discharge performance.
Ⅱ. The advantages of lithium iron phosphate battery
1. Light weight
The volume of the lithium iron phosphate battery with the same specification and capacity is 2/3 of the volume of the lead-acid battery, and the weight is 1/3 of the lead-acid battery.
2. Good high temperature performance
The electric heating peak of lithium iron phosphate can reach 350℃-500℃, while the lithium manganate battery and lithium cobalt oxide are only around 200℃. The working temperature range is wide (-20℃-75℃), and it has the characteristics of high temperature resistance.
3. Large capacity
Rechargeable batteries often work under the condition of being fully charged, and the capacity will quickly drop 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 used at any time without having to discharge it before charging.
4. Improvement of safety performance
The P-0 bond in the lithium iron phosphate crystal is stable and difficult to decompose. Even at high temperature or overcharge, it will not collapse and generate heat or form strong oxidizing substances like lithium cobaltate, so it has good safety.
5. Life expectancy improvement
Lithium iron phosphate battery refers to a lithium ion battery using lithium iron phosphate as a positive electrode material. The cycle life of long-life lead-acid batteries is about 300 times, and the maximum is 500 times, while the cycle life of lithium iron phosphate batteries is more than 2,000 times.
Comprehensive consideration, the performance-price ratio is theoretically more than 4 times that of lead-acid batteries. High current discharge can quickly charge and discharge high current 2C, under the special charger, the rack mount lithium battery can be fully charged within 40 minutes of 1.5C charging, and the starting current can reach 2c, but lead-acid batteries do not have this performance.
6. Environmental protection
Lithium iron phosphate batteries are generally considered to be free of any heavy metals and rare metals (nickel-metal hydride batteries require rare metals), non-toxic (SCS certified), non-polluting, comply with European RoHS regulations, and are an absolute green battery certificate.
Lithium iron phosphate battery cell, the energy density is 120 wh/kg, the rear group is 80 wh/kg; the ternary lithium battery cell, typically an energy density of 180 Wh/kg or a group energy density of 110 Wh/kg.
From the point of view of energy density, the ternary lithium battery is superior to the lithium iron phosphate battery; in terms of cycle life, the cycle life of the single cell is more than 3000 times, after the battery pack, and the battery is complicated by the harsh working conditions. Lifespan will be reduced to a certain extent.
At present, the energy density of lithium iron phosphate batteries has basically reached the theoretical perfection, while the energy density of ternary lithium batteries still has a lot of room for improvement. Comprehensive capacity density, power density, cycle life, low temperature performance, etc., the comprehensive performance of lithium iron phosphate batteries is better than that of ternary lithium batteries.