Chemical reaction in lithium ion batteries

The development of digital products and smart devices has brought us a more convenient life, but the increase of these products has also caused some problems. Frequent charging has caused many friends to feel trouble. The burning accidents in the news have also made many users purchase. Products are more cautious.

This article introduces you to the lithium-ion batteries that we are exposed to in our daily lives, and how different lithium-ion batteries work together to analyze their functional and safety performance.

It should be noted that the 18650 battery we often say refers to the external dimensions of the battery, while the polymer battery is classified according to the electrolyte properties of the lithium battery. The two are not the relationship between the two. The way is not in the scope of this article.

A wide variety of lithium batteries (picture from bombayharbor )

Lithium-ion batteries can be mainly divided into nickel-lithium batteries ( LiNiO2 ), nickel-cobalt lithium batteries ( LiNi0.8Co0.2O2 ), manganese-lithium batteries ( LiMn2O4 ), ternary batteries ( LiNi0.3Co0.3Mn0.3O2 ), and phosphoric acid. Iron lithium battery ( LFP ). The anode material of a lithium ion battery is mostly graphite.

Because different cathode materials have different characteristics, different lithium-ion batteries will have different gaps in different aspects. In addition, the difference in cathode materials directly leads to different costs of lithium-ion batteries, which also affects the range of use.

Lithium-ion battery charge and discharge indication (picture from pdbattery )

Taking LiCoO2 as an example, the reaction of a lithium ion battery during charging is:

Positive electrode reaction: LiCoO2==Li(1-x)CoO2+XLi++Xe-
Negative reaction: 6C+XLi++Xe- = LixC6
Total reaction: LiCoO2+6C = Li(1-x)CoO2+LixC6

The working principle of the lithium ion battery is basically the same, and the difference of the positive electrode material does not cause the essential difference in the reaction in the battery. The charging and discharging of the battery are all lithium ions ( Li+ ) moving in the electrolyte, thereby storing electric energy or discharging electric energy.

Embedding and deintercalation of lithium ion batteries

Different batteries are the movement of lithium ions: lithium ions move from the negative electrode to the positive electrode during charging. This process is called “embedding”; during discharge, lithium ions move from the positive electrode to the negative electrode, and this process is “deintercalation”.

Comparison of characteristics of different lithium-ion batteries (Image courtesy of The Current Move of Lithium Ion Batteries Towards the Next Phase. Adv. Energy Mater. 2012, DOI: 10.1002/aenm.201200028
Energy energy, safety, cost, life, power.
NMC/NCA is a ternary battery, LCO is a nickel-cobalt battery, LFP is a lithium iron phosphate battery, and LMO is a manganese lithium battery. )

Comparison of different lithium-ion batteries shows the characteristics of different batteries:

The typical cathode material of the ternary battery is LiNi0.3Co0.3Mn0.3O2 . The energy value of the battery is **, and the cost is also low, but the safety is slightly worse, the life is the longest, and the power is also large.

The typical cathode material of nickel-cobalt lithium battery is LiNi0.8Co0.2O2 . The energy value of the battery is second only to the ternary battery, and the safety is poor. The advantage is long life, low cost and high power.

The typical cathode material of lithium iron phosphate battery is LiFePO4 . The energy value of the battery is relatively **, but the safety **, long life, power **, and higher cost.

The typical cathode material of the manganese lithium battery is LiMn2O4 . The energy value of the battery is low, the safety is good, the power is **, and the shortcoming is short life and high cost.

According to different battery comparisons, we can also find that the difference in the positive electrode materials makes the battery have different performances in different characteristics, and also makes the battery differ in application.

The energy value of the ternary battery**, the longest life, power, and low cost, make it suitable for use in areas requiring high density energy, especially in areas where electric vehicles require higher endurance. .

Tesla electric car uses a ternary battery

The cost of nickel-cobalt-lithium battery is **, the power is also large, the energy value of the battery is second only to the ternary battery, and it has better performance in places where cost control is needed. Many nickel-cobalt-lithium batteries are used in mobile power and flashlight. .

Nickel-cobalt lithium battery commonly used in mobile power and flashlight

The safety of lithium iron phosphate battery **, longer life, but its higher cost, so that lithium iron phosphate battery is mainly used in places where there is a higher requirement on the use time and number of cycles, if the safety requirements**, At the same time, regardless of the cost, the lithium iron phosphate battery can also be preferred.

Lithium iron phosphate battery (picture from directindustry )

The safety of manganese lithium battery is very good, power**, mainly used as power battery, mostly used in electric bicycles and electric models, but the disadvantages of manganese lithium batteries are also more. On the one hand, the energy value of the battery is relatively low, and the life is long. It is also short, and on the other hand, the high cost of the battery also makes it less applicable.

Manganese-lithium battery for use on electric bicycles (picture from theebikemotor )

It should be said that although we mentioned the safety performance of different lithium-ion batteries, this does not mean that batteries with low safety will often have problems. This is only a comparative analysis. At present, the technology of lithium-ion batteries has matured. Security has a good performance, and the huge amount of usage is also confirmed.

In general, different lithium-ion batteries have found a balance between cost and practicability in the existing technology. Different lithium-ion batteries in different fields are also based on actual needs. In addition, the maturity of lithium-ion battery technology makes the finished battery more consistent, can also provide users with better power support, and will also play a role in a larger field.