What are the characteristics of lithium batteries?

(1) High energy density

Lithium-ion batteries are half the weight of nickel-cadmium or nickel-metal hydride batteries of the same capacity, 20-30 % of nickel-cadmium and 35-50 % of nickel-metal hydride.

(2) Gaodianya

The operating voltage of a lithium-ion battery monomer is 3.7 V(average), which is equivalent to three series nickel-cadmium or nickel-metal hydride batteries.

(3) No pollution

Lithium-ion batteries do not contain harmful metal substances such as cadmium, lead, and Mercury.

(4) No lithium metal

Lithium-ion batteries do not contain metallic lithium and are therefore not subject to restrictions on aircraft transportation regulations prohibiting the carrying of lithium batteries on passenger aircraft.

(5) High cycle life

Under normal conditions, lithium-ion batteries can charge and discharge more than 500 times, and lithium ferrous phosphate(hereinafter referred to as phosphate iron) can reach 2,000 times.

(6) No memory effect

Memory effect refers to the decrease in the capacity of nickel-cadmium batteries during the charging and discharging cycle. Lithium-ion batteries do not have this effect.

(7) Quick charging

Using a Constant-Current Constant-Voltage charger with a rated voltage of 4.2 V, lithium-ion batteries can be fully charged within 1.5 to 2.5 hours; The newly developed lithium phosphate iron has been fully charged within 35 minutes.

(8) Security

In order to avoid overdischarge or overcharging of the battery due to improper use, there is a triple protection mechanism in the single lithium ion battery. One is the use of switching components. When the temperature in the battery rises, its resistance rises. When the temperature is too high, the power supply will automatically stop. The second is to select an appropriate partition material. When the temperature rises to a certain value, the micron microholes on the partition will automatically dissolve, so that lithium ions can not pass and the internal reaction of the battery will stop; The third is to set up a safety valve(that is, the air release hole at the top of the battery). When the internal pressure of the battery rises to a certain value, the safety valve automatically opens to ensure the safety of the battery.

Sometimes, although the battery itself has safety control measures, due to certain reasons, the control failure, the lack of a safety valve, or the gas can not be released through the safety valve, the internal pressure of the battery will rise sharply and cause an explosion.

Under normal circumstances, the total energy stored in lithium-ion batteries is inversely proportional to its safety. With the increase in battery capacity, the battery volume is also increasing, and its heat dissipation performance is deteriorating, and the possibility of an accident will increase significantly. For lithium ion batteries for mobile phones, the basic requirement is that the probability of a safety accident is less than one millionth, which is the lowest standard that the public can accept. For large-capacity lithium-ion batteries, especially large capacity lithium-ion batteries such as automobiles, it is particularly important to use forced heat dissipation.

The selection of safer electrode materials and the selection of lithium manganate materials ensure that in the full state of the molecular structure, the positive lithium ion has been completely embedded in the negative carbon hole, thus fundamentally avoiding the generation of dendrites. At the same time, the solid structure of lithium manganese acid makes its oxidation performance much lower than that of lithium cobalt acid, and the decomposition temperature exceeds lithium cobalt acid 100 °C, even if the external external external short-circuit(acupuncture) occurs due to external forces, the external short-circuit, and overcharging, It is also possible to avoid the danger of combustion and explosion caused by the precipitation of metallic lithium.

In addition, the use of lithium manganese acid materials can also significantly reduce costs.

To improve the performance of the existing safety control technology, it is necessary to improve the safety performance of the lithium ion battery core, which is particularly important for large-capacity batteries. Select a diaphragm with good thermal closure performance. The diaphragm's role is to separate the positive and negative poles of the battery while allowing the passage of lithium ions. When the temperature rises, it is closed before the diaphragm melts, so that the internal resistance rises to 2000oumu and the internal reaction stops.

When the internal pressure or temperature reaches the preset standard, the blast Valve will open and begin to discharge to prevent the accumulation of too much internal gas and deformation, which will eventually cause the shell to burst.

Improved control sensitivity, more sensitive selection of control parameters and joint control using multiple parameters(this is particularly important for large-capacity batteries). For large-capacity lithium ion batteries, which are composed of series/parallel multiple cores, for example, the voltage of a notebook computer is more than 10V, and the capacity is large. Generally, 3 to 4 single cells can be used in series to meet the voltage requirements. Then two to three series batteries are connected in parallel to ensure a larger capacity.

The large-capacity battery itself must be equipped with a relatively complete protection function. Two circuit substrate modules should also be considered: the Protection Framework PCB module and the SmartBatteryGaugeBoard module. The battery protection design of the entire set includes: Level 1 protection IC(prevention of battery overcharge, overdischarge, short circuit), Level 2 protection IC(prevention of second overpressure), Fuse, LED indication, temperature adjustment and other components.

Under the multi-level protection mechanism, even in the case of abnormal power chargers and notebook computers, notebook batteries can only be turned into automatic protection. If the situation is not serious, they can often work normally after replugging and unexploding.

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