2023 April HK Spring Electric Fair

TWD Technology Limited Hong Kong Exhibition

Safety of lithium-ion batteries

1、 Pay attention to short circuit Please pay attention to the safety of lithium-ion batteries. Lithium ion batteries are prone to short circuit during charging. Although most lithium-ion batteries now have short-circuit protection circuits and explosion-proof wires. But in many cases, this circuit may not work under various circumstances. Explosion-proof wire can also play a limited role. 2、 Do not overcharge All lithium-ion batteries, whether developed in the past or polymer lithium-ion batteries and lithium-iron batteries developed in recent years, are very afraid of overcharging. If the charging time of lithium-ion battery is too long, the possibility of explosion will increase. Lithium has very active chemical properties and is easy to burn. When the battery is charged and discharged, the internal temperature of the battery continues to rise, and the gas generated in the activation process expands, which increases the internal pressure of the battery. When the pressure reaches a certain level, if the shell is scarred, it will break, causing liquid leakage, fire and even explosion. Therefore, you should pay great attention to safety when using lithium-ion batteries.

Nine advantages of lithium battery

The nine advantages of lithium battery are as follows: 1. The energy is relatively high. It has a high storage energy density, which has reached 460-600Wh, about 6-7 times that of lead-acid batteries; 2. The service life is long, and the service life can reach more than 6 years. The battery with lithium ferrous phosphate as the positive electrode 1C (100% DOD) can be charged and discharged with a record of 10000 times; 3. The rated voltage is high (the single working voltage is 3.7V or 3.2V), which is about equal to the series voltage of three nickel-cadmium or nickel-hydrogen batteries, which is convenient to form the battery power pack; 4. It has high power bearing capacity, among which the lithium ferrous phosphate lithium ion battery for electric vehicles can reach the capacity of 15-30C charging and discharging, which is convenient for high-intensity starting acceleration; 5. The self-discharge rate is very low, which is one of the most prominent advantages of the battery. At present, it can generally achieve less than 1%/month, less than 1/20 of the nickel hydrogen battery; 6. Light weight, about 1/5-6 of lead acid product in the same volume; 7. High and low temperature adaptability, can be used at - 20 ℃ - 60 ℃, and can be used at - 45 ℃ after process treatment; 8. Green environmental protection, no matter how it is produced, used or scrapped, it does not contain or produce any toxic and harmful heavy metal elements and substances such as lead, mercury and cadmium. 9. Production basically does not consume water, which is very beneficial to China, which is short of water. Specific energy refers to the energy per unit weight or volume. Specific energy is expressed in Wh or Wh/L. Wh is the unit of energy, W is the watt and h is the hour; Kg is the kilogram (weight unit) and L is the liter (volume unit).

Positive and negative pole composition of lithium battery

Lithium batteries usually have two types of appearance: cylindrical and square. The inside of the battery is spiral wound structure, which is made of a very fine and highly permeable polyethylene film isolation material between the positive and negative electrodes. The positive electrode includes a current collector composed of lithium cobaltate (or nickel cobalt lithium manganate, lithium manganate, lithium ferrous phosphate, etc.) and aluminum foil. The negative electrode is composed of a current collector composed of graphitized carbon material and copper foil. The battery is filled with organic electrolyte solution. In addition, there are safety valves and PTC elements (some cylindrical elements are used) to protect the battery from damage in case of abnormal state and output short circuit. The voltage of a single lithium battery is 3.7V (3.2V for lithium ferrous phosphate anode), and the battery capacity cannot be unlimited. Therefore, a single lithium battery is often processed in series and parallel to meet the requirements of different occasions.

Main characteristics of lithium ion battery

A. The weight of high energy density lithium ion battery is half of that of nickel cadmium or nickel hydrogen battery with the same capacity, and the volume is 20-30% of nickel cadmium and 35-50% of nickel hydrogen. B. High voltage The working voltage of a single lithium-ion battery is 3.7V (average), which is equivalent to three nickel-cadmium or nickel-hydrogen batteries in series. C. Non-polluting lithium-ion batteries do not contain harmful metal substances such as cadmium, lead and mercury. D. The lithium-ion battery without metal lithium does not contain metal lithium, so it is not subject to the provisions of aircraft transportation on the prohibition of carrying lithium batteries in passenger aircraft. E. High cycle life Under normal conditions, the charge and discharge cycle of lithium ion battery can exceed 500 times, and the lithium ferrous phosphate (hereinafter referred to as ferrophosphate) can reach 1000 times. F. Memory effect without memory effect refers to the phenomenon that the capacity of Ni-Cd battery decreases during the charge-discharge cycle. Lithium ion batteries do not have this effect. G. The constant current and constant voltage charger with rated voltage of 4.2V is used for fast charging, which can make the lithium ion battery fully charged within 1.5-2.5 hours; The newly developed lithium phosphate battery can be fully charged in 35 minutes.