Lithium batteries characteristics
Lithium battery is one of the representatives of modern mainstream batteries. Its advantages are quite obvious. So what are the characteristics of lithium batteries? As one of the representatives of modern mainstream batteries, lithium batteries have many advantages that other batteries cannot match. So what are the characteristics of lithium batteries? ?
1. High energy. Specific energy refers to energy per unit weight or unit volume. Specific energy is expressed by Wh/ko or Wh. Wh is the unit of energy, W is watts, h is hours, and ko is grams (weight side, L It is a liter (volume unit). Energy density is the standard for measuring a battery. Lithium batteries have high storage energy density, which has reached 460-600W/kg, which is about 6-7 times that of lead-acid batteries.
2. Good safety performance and long cycle life
The reason why batteries using metallic lithium as the anode are unsafe is that repeated charging and discharging cause the structure of the positive electrode of the lithium-ion battery to change, forming porous dendrites. When the temperature rises, it undergoes a violent exothermic reaction with the electrolyte, and the dendrites It can pierce the diaphragm and cause an internal short circuit. However, lithium batteries do not have this problem and are very safe. In order to avoid the presence of metallic lithium in the battery, the voltage must be controlled during charging. For safety reasons, lithium batteries are equipped with multiple safety devices.
During the charging and discharging process of lithium batteries, lithium ions are inserted and deintercalated on the cathode and anode without any structural changes (there will be some expansion and contraction of the crystal lattice during the insertion and deintercalation process), and because the chimeric compound is more durable than metallic lithium It is stable and does not form lithium dendrites during the charge and discharge process, thus significantly improving the safety performance of the battery and greatly increasing the cycle life. The service life can reach more than 6 years. The battery with lithium iron phosphate as the positive electrode can be charged and discharged at 1C (100%DOD), and has a record of being used 10,000 times.
3. High rated voltage. The single working voltage is 3.7V or 3.2V, which is approximately equal to the series voltage of three nickel-chromium or nickel-metal hydride rechargeable batteries, making it easy to form a battery power pack. The lithium battery can pass a new type of battery voltage regulator technology to adjust the voltage to 3.0V to suit the use of small electrical appliances.
Replacing metallic lithium with graphite or petroleum coke lithium compounds as the negative electrode will cause the battery voltage to drop, but due to their low lithium insertion potential, the voltage loss can be reduced to a minimum. At the same time, selecting a suitable lithium-embedded compound as the battery cathode and selecting an appropriate electrolyte system (which determines the electrochemical window of the lithium battery) can enable the lithium battery to have a higher operating voltage (4V), which is much higher than the aqueous solution system battery.
4. High power endurance
Among them, the lithium iron phosphate battery used in electric vehicles can achieve a charge and discharge capacity of 15-30C, which facilitates high-intensity starting and acceleration.
5. The self-discharge rate is very low
This is one of the most prominent advantages of lithium batteries. Generally, it can achieve less than 1%/month, which is less than 1/20 of nickel-metal hydride batteries. The battery uses a non-aqueous electrolyte system. The lithium-embedded carbon material is thermodynamically unstable in the non-aqueous electrolytic system. During the first charge and discharge process, a layer of solid electrolyte interphase (SEI) film will be formed on the surface of the carbon negative electrode due to the reduction of the electrolyte. , allows lithium ions to pass but does not allow electrons to pass, and makes the electrode active materials of different charge states in a relatively stable state, so it has a low self-discharge rate.
6. Light weight
The weight of the same volume is about 1/6-1/5 of the lead-acid product.
7. Low temperature resistance
It can be used in the environment of -20°-60°. After processing, it can be used in the environment of -45°. Both lithium and lead batteries lose useful energy capacity in cold weather conditions. However, with lead batteries, the effects are much more severe. At a temperature of -20C, the useful energy of lead batteries is reduced to 30%, and under the same discharge conditions, lithium batteries retain 82% of their energy capacity. Not only do lithium batteries last longer in hot countries, but they also last longer in very cold areas in mountainous areas.
8. Green and environmentally friendly
Regardless of production, use or disposal, it does not contain or produce any lead, mercury, bromine and other toxic and harmful heavy metal elements and substances.
At the same time, because the battery must be well sealed, very little gas is released during use and does not cause pollution to the environment. The solvents used to debond during the manufacturing process can also be fully recycled.
9. High turnover efficiency
Cycle efficiency shows how efficient a battery is over a complete charge and discharge cycle. For lead batteries, this is typically around 75%. This means that if you charge a 1000Wh lead battery, you will only get 750Wh to actually power your device. So you lose 25% of your system efficiency with the batteries alone! In solar system usage, this means you need at least 25% more PV panels to power the same load. Under these conditions, the system will inevitably become more expensive (or perform worse with the same configuration). However, for lithium batteries, the cycle efficiency is about 98%. It’s no wonder we’re seeing an increase in the use of this battery technology.
10. Large specific capacity
Although replacing metal hammers with carbonaceous materials will reduce the material mass specific capacity, in fact, in order to ensure that the battery has a certain cycle life in metallic lithium secondary batteries, the negative electrode metal lithium is usually overdosed by more than three times, so the quality of the lithium battery The actual reduction in specific capacity is not large, and the volumetric specific capacity is almost not reduced.
11. High current efficiency
Unlike any previous aqueous solution system secondary battery, lithium batteries do not produce gas during normal charge and discharge processes, and the current efficiency is close to 100%. This property is particularly suitable for use as a battery pack for power storage and conversion.