An overview of lithium batteries you must know

An overview of lithium batteries you must know

Lithium battery is referred to as lithium battery. Lithium battery mainly refers to a type of battery that uses lithium element as the main active material in the electrode material. Lithium batteries are divided into lithium primary batteries (primary batteries) and lithium secondary batteries. The inventor of the lithium battery was Edison. As shown in Figure 1 is a lithium battery product.

Figure 1-18650 lithium battery
Figure 1-18650 lithium battery
  1. The structure of lithium battery

In a broad sense, a rechargeable lithium battery is composed of graphite as the negative electrode and cobalt, manganese or iron phosphate as the positive electrode and an electrolyte for transporting lithium ions. The electrolyte in the lithium battery can be gel, polymer Or a mixture of gel and polymer, the positive or negative electrode must have a sponge-like physical structure to release or receive lithium ions.

The structure of lithium battery
The structure of lithium battery
  1. Advantages and disadvantages of lithium batteries

(1) Advantages of lithium batteries Compared with nickel-metal hydride batteries, lithium batteries have the following significant advantages:
①High working voltage, high energy density, low self-discharge rate, no memory effect;
②The lithium battery can be made thinner (the thinnest polymer lithium battery is only 0.5mm), and it can be made smaller:
③The area and shape can be changed at will, thus greatly improving the flexibility of battery design. Manufacturers can make batteries of any shape and capacity according to the needs of users:
④ Compared with lead-acid batteries, lithium batteries are light and durable, and have relatively less environmental pollution; , will not cause additional loss to the battery. (click here to open to buy high-quality lithium battery products)

(2) Disadvantages of lithium batteries
①Lithium battery is neither resistant to high temperature nor low temperature. Due to some defects in the manufacturing process, there is a possibility of explosion when the ambient temperature is high.
②It is easily damaged by overcharging.
Long-term charging of lithium batteries will keep the battery at the edge of danger for a long time, because long-term charging will degrade the characteristics of the battery’s charge-discharge protection circuit.
After the lithium battery is charged for a certain period of time, if the charger is not removed, the system will not only stop charging, but will also start a discharge-charge cycle, and the life of the charger will decrease.
It takes a long time to charge for a long time, and it often needs to be carried out at night. According to the situation of China’s power grid, the voltage at night in many places is relatively high and fluctuates greatly. Lithium batteries are much less resistant to fluctuations in charge and discharge than nickel batteries, so the life of lithium batteries will be further reduced.

③ Due to the very active chemical properties of lithium metal, the processing, storage, use and environmental requirements of lithium metal are very high. Therefore, when not in use for a long time, the lithium battery should be taken out and placed in a cool and dry place. Do not freeze to avoid water vapor erosion.
④ It is rarely used in the market of large-scale energy storage and power batteries (which require a large current in an instant), the main reason is that lithium batteries use lithium and cobalt as cathode materials, which are not resistant to high current, high voltage, high torque, collision and In special environments such as high temperature and low temperature, safety is not guaranteed.
⑤Lithium-cobalt batteries cannot be charged quickly and completely avoid secondary pollution. A protection circuit must be designed to prevent overcharging or overdischarging, otherwise it will cause dangers such as explosion.
⑥ The price of diamonds is getting higher and higher. The largest producer of diamond elements in the world, the Congo, has many wars and turmoil, resulting in the rising price of diamond elements.
⑦ Avoid buying spare lithium batteries for storage, because even if the battery is not used, its service life is naturally degraded.

  1. Improvement of lithium battery

(1) Improve the charging process The charging rate is usually not more than 1C, and the minimum discharge voltage is 2.7~3.0V. If you continue to discharge, the battery will be damaged. Lithium batteries are charged in a constant current to constant voltage mode. When using 1C current to charge to 4.1V, the charger should immediately switch to constant voltage charging, and the charging current will gradually decrease. When the battery is fully charged, it will enter the trickle charging process.

(2) Setting up a safety mechanism In order to avoid overcharging or overdischarging, the lithium battery not only has a safety mechanism inside, but the charger also takes safety protection measures to monitor the charging and discharging status of the lithium battery. In order to avoid battery damage caused by improper use, there are three safety mechanisms inside the lithium-ion battery.

① Positive temperature coefficient element (PTC) When the temperature in the battery is too high, the resistance of the PTC will rise, and the circuit between the cathode lead and the cathode will be automatically cut off.
②Separator of special material When the temperature in the battery rises to a certain value, the micropores on the separator will automatically dissolve, thereby stopping the reaction in the battery.

③Safety valve When the internal pressure of the battery rises to a certain value, the safety valve will automatically open. However, the newly developed solid-state polymer (electrolyte) lithium-ion battery and lithium metal battery not only solve the problem of liquid leakage, but also have a larger capacity, smaller volume, and more safety and reliability. They will surely become a new generation of battery products with great potential.

  1. The working principle of lithium battery

During charging, lithium ions are moved from the negative electrode material to the electrolyte, and then into the positive electrode material, while the discharge process is completely reversed.

  1. The advantages and disadvantages of various lithium batteries

The choice of cathode materials for lithium batteries depends on the capacity, safety and aging characteristics of the battery.
(1) Lithium-nickel-cobalt battery Lithium-nickel drill battery is a new type of battery composed of lithium-nickel battery and lithium drill battery, which combines the advantages of lithium-nickel and lithium drill battery. Among them, the drill has excellent capacity and aging characteristics, but the positive electrode of the drill often forms metallic lithium during the discharge process. Because of the flammable nature of metallic lithium, if safety measures fail, metallic lithium tends to ignite. In order to improve the safety of the battery, manganese or iron phosphate is used to replace cobalt as the positive electrode material, resulting in lithium nickel batteries, lithium nickel cobalt batteries, lithium manganese batteries, lithium nickel diamond manganese batteries and lithium iron phosphate batteries. Although these batteries improve the safety of the battery, the battery capacity is slightly reduced, and the aging speed of the battery is accelerated.

(2) Lithium-manganese battery Lithium-manganese battery has low cost and better safety than lithium drill battery, but its cycle life is not good, especially in high temperature environment. At high temperature, the phenomenon of manganese ion dissolution will occur, resulting in serious high temperature self-discharge and poor battery energy storage characteristics.

(3) Lithium-nickel battery Lithium-nickel battery has lower cost and higher electric capacity, but it is difficult to manufacture, has poor material consistency, and cannot guarantee safety.
(4) Lithium iron phosphate battery Lithium iron phosphate battery also has the main advantages of lithium diamond, lithium nickel and lithium manganese batteries. The lithium iron phosphate battery has a moderate working voltage (3.2V), a large capacity (170mA·h/g), high discharge power, fast charging and long cycle life. It is a battery that meets the requirements of environmental protection and high performance. However, compared with lithium batteries, the dangers that are prone to occur have not been completely changed.

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