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Power Battery Type And Application Characteristics - Lithium Ion Battery

May 15, 2019

A lithium ion battery is a secondary battery (rechargeable battery) that mainly relies on lithium ions moving between a positive electrode and a negative electrode to operate. During charge and discharge, Li+ is intercalated and deintercalated between the two electrodes: when charging, Li+ is deintercalated from the positive electrode, and the electrolyte is embedded in the negative electrode, and the negative electrode is in a lithium-rich state; The state is opposite when discharging.The electrode materials are all lithium ions that can be intercalated (inserted) /deintercalated (deintercalated).

A lithium battery, such as lithium cobalt oxide, lithium manganate, lithium nickel cobalt manganese oxide (ternary material), lithium iron phosphate, etc., is classified as lithium ion power battery, and each has its advantages, and it is the trend of a new generation. Like all chemical batteries, lithium-ion batteries are also made up of four parts: positive, negative, diaphragm and electrolyte.

(1) Positive electrode - the active material is generally lithium cobalt oxides, lithium manganate, lithium nickel-cobalt manganate(ternary material), lithium iron phosphate material, etc.

Positive electrode reaction: Lithium ions are embedded during discharging, and lithium ions are deintercalated during charging.

Lithium cobalt oxides battery: Its characteristics are stable structure, high capacity ratio, outstanding comprehensive performance, but poor safety and high cost. It is mainly used for small and medium-sized batteries, and is widely used in small electronic devices such as notebook computers, mobile phones and MP3/4.

Lithium manganate battery: Lithium manganate is a positive electrode material with low cost, good safety and low temperature performance, but the material itself is not stable and easily decomposes to generate gas, so it is often used in combination with other materials to reduce the cost of the cell. However, its cycle life decays faster, it is prone to bulging, low temperature performance and relatively short life. It is mainly used for large and medium-sized batteries and power batteries. The parameters are as follows:The nominal voltage is 3.7V, the output voltage range is 2.5~4.2v, the standard continuous discharge current is 0.2C, the maximum continuous discharge current is 1C, the working temperature is: charging: 0~45°C, discharge: -20~60°C.

LiNiCoMn battery: refers to a lithium battery using a lithium nickel cobalt manganese ternary positive electrode material for the positive electrode, the ternary material is Li (NiCoMn) O2, and the battery with the ternary material as the positive electrode has higher safety than the lithium cobalt oxide battery.

Battery cathode material: lithium manganate (LiMn204).

Mixed additive: lithium, nickel, aluminum oxide (Li(Ni-Al)02).

Battery anode material: graphite.

Lithium iron phosphate battery: refers to a lithium ion battery using lithium iron phosphate as a positive electrode material, molecular formula: LiFePO4;The peak temperature of lithium iron phosphate can reach 350 ° C -500 ° C, while lithium manganate and lithium cobalt oxide are only around 200 ° C.

(2) Separator - a specially formed polymer film with a microporous structure that allows lithium ions to pass freely while without electrons passing through;

(3) Negative electrode - the active material is graphite, or carbon similar to graphite structure;

(4) Organic electrolyte - a carbonate solvent in which lithium hexafluorophosphate is dissolved, and the polymer uses a gel electrolyte;

(5) Battery packing - divided into steel shell, aluminum shell, aluminum plastic film (soft packaging).

Lithium-ion power battery voltage is three times of nickel-cadmium battery and nickel-hydrogen battery, twice of lead-acid battery. This is an important reason for the high specific energy of lithium-ion power batteries. When lithium-ion power batteries are composed of power batteries of the same voltage, the number of series connected to lithium-ion power batteries will be much less than that of lead-acid batteries and nickel-hydrogen batteries. If the number of single cells in the power battery is more, the consistency requirement of the single cells in the battery pack is higher, and is harder to keep the cycle life. After the battery pack has problems in actual use, it is generally one or two. The problem with the single cells then caused problems in the entire battery pack, so it is not difficult to understand why the 48V lead-acid battery has higher feedback than the 36V lead-acid battery. From this point of view, lithium battery is more suitable for the use of the power battery. For example, 36V lithium battery only needs 10 battery cells, while 36V lead acid battery requires 18, that is 3 units of 12V battery packs, and each 12V lead acid battery has 6 cells.