1. Battery material. Four main materials of the battery, cathode material, anode material (also called cathode, anode material), isolation membrane and electrolyte. From the material level, lithium iron phosphate thermal runaway trigger point is at 800-1000 degrees, ternary material about 300 degrees, which is purely speaking material. But when the battery is made, the temperature of the heat control can not only look at the cathode material.
Graphite material to do the cathode at high temperatures, the thermal runaway negative reaction is also more than 300 degrees, lithium iron phosphate after the full battery also reached less than 800 degrees, may be at 300 degrees will begin to touch the fever out of control. and ternary made full battery, although the temperature of the test heat control is about 300 degrees, but in fact the trigger conditions between 130-150 degrees has begun.
On ternary materials, light material itself, in the temperature reached a certain degree, will touch the heat out of control, produce oxygen and heat, and then with the graphite anode interaction, various side effects. The safety technical condition of electric passenger car after come out, as long as the ternary material battery can pass the heat out of control test, or the real application does not have big problem, I feel can not use the limit value technology route.
2. The package form of the battery. The various packaging forms of batteries, such as cylindrical, square, soft bags. The world's better aluminum-shell batteries, the original good years ago to do the test data is very good, but also measured the more expensive lithium iron phosphate battery. Different batteries, 18650 particularly good advantage is that the group is very flexible, small. Soft Pack battery is also because of thin, group is also very convenient. From the perspective of security measures, the square battery (structure) is better to do, I can not say that the square battery is safer, but its safety measures easier to do.
Inside the battery, the power battery positive and negative pole piece process, has the lamination technology, the winding craft. The lamination process is the same as playing cards, the winding process is the same as the Swiss volume. 18650 is a round winding, square battery is oval, production efficiency will be relatively high, and the accuracy of the requirements of the equipment is not as harsh as laminated, laminated do a good job is Japan and South Korea, generally do very well, the design process requirements are very high.
3. Battery group. The necessity of power battery group is introduced. Why are there so many battery strings, parallel in the bus? Because no matter the voltage or the electricity, the general single battery cannot reach the requirement. To meet the driving voltage requirements, must be in series, to meet the requirements of electricity, must be in parallel. In fact, whether it is passenger cars or buses, in fact, are both in tandem, and parallel, mixed structure.
First in parallel or in series? In this view, whether from the electrical design, or management system design are different, cost and performance are different. Like fast charge, should be in series after the parallel, otherwise the current is not very big.
The group process contains many elements, the most important of which are three. First, mechanical properties. Whether the protection in group mode is in place; The electric connection is connected properly and the third is thermal management.
4. Electric vehicle demand for batteries. Electric cars want to have power batteries that guarantee enough mileage to continue, especially like pure electric cars. The two primary concerns are cost, energy density. As for the convenience of charging, power characteristics, environmental adaptability also need attention. Environmental adaptability requires the battery dustproof, waterproof and adapt to a variety of ambient temperature, but also to ensure that no fire, no explosion, durability, attendance, reliability.