A lithium-ion battery is a secondary battery that uses a lithium-containing compound as the positive electrode. During the charging and discharging process, lithium ions are reciprocally extracted and intercalated between the positive and negative electrodes of the battery to achieve charge and discharge.
Lithium-ion batteries are mainly composed of positive electrodes, negative electrodes, electrolytes, and separators. Lithium-ion batteries rely primarily on the movement of lithium ions between the positive and negative electrodes to function. During the charging and discharging process, Li+ intercalates and deintercalates back and forth between the two electrodes: when charging, Li+ is deintercalated from the positive electrode, intercalated into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge.
Lithium-ion batteries have many notable features, and its advantages are mainly as follows:
1. High voltage: the working voltage of a single battery is as high as 3.7-3.8V (3.2V for lithium iron phosphate, which is 3 times that of Ni-Cd and Ni-MH batteries)
2. Large specific energy: The actual specific energy that can be achieved is about 555Wh/kg, that is, the specific capacity of the material can reach more than 150mAh/g (3-4 times that of Ni-Cd, 2-3 times that of Ni-MH, which is close to about 88% of its theoretical value)
3. Long cycle life: Generally, it can reach more than 500 times, or even more than 1000 times, and the lithium iron phosphate can reach 6000 times.
4. Good safety performance: no pollution, no memory effect. Lithium battery, the predecessor of Li-ion, because metal lithium is easy to form dendrites and cause short circuit, which reduces its application field; Li-ion does not contain cadmium, lead, mercury and other elements that pollute the environment
5. Small self-discharge: the self-discharge rate of fully charged Li-ion at room temperature after storage for 1 month is about 2%, which is much lower than 25-30% of Ni-Cd and 30-35% of Ni-MH
6. Fast charging: 1C charging for 30 minutes can reach more than 80% of the nominal capacity, and phosphorus-iron batteries can reach 90% of the nominal capacity in 10 minutes.
7. Working temperature: The working temperature is -25~45°C. With the improvement of electrolyte and positive electrode, it is expected to be extended to -40~70°C.
Lithium-ion batteries also have some shortcomings, mainly in the following aspects:
1. Aging: Unlike other rechargeable batteries, the capacity of lithium-ion batteries will slowly decline, which is related to the number of times of use and temperature. This decline phenomenon can be expressed by a decrease in capacity or an increase in internal resistance. Because it is related to temperature, it is easier to reflect in electronic products with the high operating currents.
2. Recycling rate: About 1% of new products need to be recycled for various reasons.
3. Intolerance to overcharging: When overcharging, the excessively embedded lithium ions will be permanently fixed in the crystal lattice and cannot be released again, which can lead to short battery life.
4. Intolerance to over-discharge: During over-discharge, the electrodes deintercalation too many lithium ions, which can lead to the collapse of the crystal lattice, thereby shortening the service life.
In recent years, the application range of lithium-ion batteries has become more and more extensive. Lithium batteries are widely used in energy storage power systems such as water power, firepower, wind power, and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, Aerospace, and other fields.
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