Since its successful development in 1990, liquid lithium-ion batteries have unique advantages such as high specific energy, no pollution, and high safety. Together with fuel cells and solar cells, they are called the ideal green power source in the 21st century.
In addition to having all the advantages of liquid lithium-ion batteries, polymer lithium-ion batteries can be made into ultra-thin batteries of any shape and size due to their use of non-flowing electrolytes. They are more suitable for use as power sources for micro-electric appliances and have safety performance. Also better. Since the industrialization of polymer lithium-ion batteries in 1999, they have become more widely used and have gradually replaced liquid lithium-ion batteries.
Lithium-ion batteries are widely used. Only in terms of batteries used in mobile phones, more than 80% are lithium-ion batteries. In the future, large-capacity, high-efficiency power lithium-ion batteries will surely become the ideal power source for electric vehicles and electric bicycles.
2. The advantages of lithium ion batteries
(1) Larger than energy. The specific energy of lithium-ion batteries is as high as 460W·h/kg~600Wh/kg. Therefore, the capacity of the lithium-ion battery is 10 times that of the lithium-manganese battery of the same specification.
Compared with nickel-cadmium batteries and nickel-hydrogen batteries, when the capacity is the same, the quality is only half of them; the volume is 20%-30% of nickel-cadmium batteries and 35%-50% of nickel-hydrogen batteries. Therefore, it is often said that lithium-ion batteries have the advantages of small size, small mass, and large capacity.
(2) The average output voltage is high. The rated voltage of a single battery is high, 3.6V or 3.7V, which is 3 times the rated voltage of nickel-cadmium and nickel-hydrogen batteries, which improves the working efficiency of lithium-ion batteries.
(3) The self-discharge rate is extremely low. The annual self-discharge of lithium-ion batteries is less than 10% when they are shelved, so they usually have a long storage time of 5 to 10 years. The self-discharge rate of lithium-ion battery can be judged by its resistance value:
The lower the resistance value, the lower the self-discharge rate. This is because the resistance value of a lithium-ion battery is not directly related to its charge capacity.
(4) No charge-discharge memory effect. Lithium-ion batteries do not need to be discharged before charging, and can be charged and discharged at any time without affecting the service life of the battery.
(5) Long service life. Under normal conditions, the number of cycles of charging and discharging lithium-ion batteries exceeds 500 times, and it can actually reach more than 1200 times. And the charging efficiency is as high as 100%.
(6) Allow high current operation. Lithium-ion batteries allow high-current discharge in a short time. High-current fast charging can also be used to shorten the charging time to 1.5h-2.5h.
(7) It does not contain cadmium, lead, mercury and other heavy metal elements, so it does not pollute the environment and is the most advanced green battery in the contemporary era.
(8) The allowable working temperature range is very wide, ranging from -20°C to 60°C. It can still be used outdoors in winter, but the capacity will be much lower. If it returns to room temperature, the capacity can be restored. This is conducive to the storage and use of lithium-ion batteries.
(9) It has perfect over-charge, over-discharge, ultra-high temperature, over-current, short-circuit protection, lock self-recovery and reliable equalization charging functions, which greatly extend the service life of the battery.
3. Disadvantages of lithium-ion batteries
(1) There is no interchangeability with dry batteries, and the working voltage changes greatly.
(2) The discharge rate is large, and the capacity drops quickly.
(3) Lithium-ion batteries need to be equipped with a protection circuit to prevent the battery from being overcharged or over-discharged.
(4) There are potential safety hazards, because the lithium salt LiPF6 of lithium-ion batteries will decompose hydrofluoric acid (HF) in the air, which has a strong corrosive effect on human bones, so the safety requirements are high and must be strictly followed. For production and use.
(5) The production conditions are high, the cost is high, and the price is more expensive compared with other secondary batteries.
(6) Organic solvents often destroy the structure of graphite during charging, causing it to peel off, and form a solid electrolyte film on its surface, leading to electrode passivation. Organic solvents also bring safety problems such as flammability and explosion.