Power batteries include lithium-ion power batteries, metal hydride/nickel power batteries, etc. Lithium-ion power battery is often referred to as lithium-ion battery, lithium-ion battery is an important category of new energy vehicles that powers lithium battery, and the market share is also the largest.
New energy vehicle market, lithium-ion batteries are commonly lithium-iron phosphate batteries and ternary lithium-ion batteries. Today, I'll take stock for you
Ternary lithium-ion batteries and lithium-iron phosphate batteries have important features, their respective advantages, and disadvantages.
Lithium iron phosphate ion batteries: long cycle life and good safety
Lithium-ion batteries with lithium iron phosphate as the cathode material. It features no precious elements such as cobalt, low raw material prices, and abundant resources of phosphorus and iron. Its working voltage is moderate (3.2V), high capacity per unit weight (170mAh/g), high discharge power, fast charging, and long cycle life, and high stability in high temperature and high heat environments.
- lithium iron phosphate ion batteries are characterized by high safety, high rate charge, and discharge characteristics, and long cycle life. Literature shows that in the charging conditions for 1C times the rate of charge to 3.65V, then turn constant voltage until the current drops to 0.02C, followed by 1C times the rate of discharge to the cut-off voltage of 2.0V, after 1600 cycles battery capacity is still 80% of the initial capacity.
- lithium iron phosphate ion batteries have good fast charging characteristics, 3C times the charging conditions, 15 minutes can be charged 55%, and 30 minutes to charge a capacity of more than 95%.
- in addition to long life, excellent charge and discharge performance, lithium iron phosphate ion battery's biggest advantage is its good safety, lithium iron phosphate chemical stability, high-temperature stability, 700-800 ℃ before decomposition will begin, and in the face of impact, pinprick, short circuit, and other circumstances will not release oxygen molecules, there will be no violent combustion, high safety performance.
- the disadvantage of lithium iron phosphate ion battery is that its performance is greatly affected by temperature, especially in low-temperature environments, the discharge capacity and capacity will be significantly reduced. In addition, lithium iron phosphate energy density is low, only counting the weight of the battery energy density of only 120Wh/kg.
Ternary lithium-ion batteries: low-temperature resistant energy density
Ternary lithium-ion batteries, that is, ternary polymer lithium-ion batteries, cathode material using lithium nickel cobalt manganate ternary cathode material lithium-ion batteries, that is, containing nickel, cobalt, manganese three elements of transition metal embedded lithium oxide in line with the material anode lithium-ion batteries. This material combines the advantages of lithium cobaltate, lithium nickelate, and lithium manganate, forming a three-phase eutectic system of three materials, and its comprehensive performance is better than any single combination of compounds due to the ternary synergistic effect, and the weight energy density can reach 200Wh/kg.
- Unlike lithium iron phosphate, the ternary lithium-ion battery voltage platform is very high, which means that in the same volume or weight, the ternary lithium-ion battery's specific energy, and specific power is greater. In addition, in terms of large multiplier charging and low-temperature performance, ternary lithium-ion batteries have great advantages. The northern winter temperature range is more suitable for the low-temperature performance of ternary lithium-ion batteries, while the importance of the high-temperature performance of lithium-iron phosphate batteries in the northern winter will seem a little weak.
- Ternary lithium-ion battery safety is relatively slightly worse. Ternary lithium-ion battery thermal stability is poor, 250-300 ℃ will decompose, encounter the battery in the combustible electrolyte, carbon materials, a little bit on the spot, the emergence of heat to further intensify the decomposition of the anode, in a very short time will burst into flames. In a car accident, the external impact will damage the battery diaphragm, which will lead to a short circuit, and the heat emitted during the short circuit will cause the battery to thermal runaway, and quickly raise the temperature to more than 300 ℃, there is a risk of spontaneous combustion. Therefore, the ternary lithium-ion battery, its battery management system, and the heat dissipation system are critical.
To improve the safety of the product, the use of materials with strong heat resistance, the use of pressure relief valves to control the pressure in the battery, active control of the battery current, and real-time monitoring of the battery charging status, and the ability to force cut off the current circuit to improve safety. These are all feasible measures to improve the safety of ternary lithium-ion batteries.
Comprehensive comparison: lithium-iron phosphate ion batteries are better
With the improvement of the battery pack structure development technology, lithium iron phosphate group energy density has reached the level of ternary NCM523 and is still improving. At present, GoTion has completed the upgrade of the lithium iron phosphate monomer energy density 180Wh/kg production line, and the system energy density in passenger cars is close to 130Wh/kg, which can meet the range of about 400 km. Gordon plans to increase the energy density of lithium iron phosphate monomer cells to nearly 200Wh/kg in 2019.
Compared with ternary lithium-ion batteries, low raw material prices, high safety, and long service life of lithium iron phosphate ion batteries are more advantageous, many battery manufacturers are also confident in the larger scale market for lithium iron phosphate.
HZT said in the performance briefing: the company's lithium iron phosphate is to continue to expand production. BYD Lithium Division has also publicly expressed the belief that lithium iron phosphate ion batteries in a certain local strong return.
The analysis points out that after the real market, lithium iron phosphate's low-cost, long life, and high safety advantages in passenger cars, commercial vehicles, and special vehicles will gradually appear.