Anode in lithium ion battery-as the main feature of the battery

During the charging and discharging process of lithium ion battery, electrochemical oxidation/reduction reaction of anode in lithium ion battery will occur, and lithium ions are repeatedly intercalated and extracted in the material.

In lithium ion battery structure, the anode material is very important. At the same time, there are many types of anode materials. This article will take you through anode in lithium ion battery.

Material requirements for anode in lithium ion battery

Not all materials can be used as anode in lithium ion battery. In order to ensure good electrochemical performance, the requirements foranode materials are as follows:

● The metal ions in the positive electrode material have a high redox potential, so that the battery has a high working voltage;

● The mass specific capacity and volume specific capacity are high, so that the battery has high energy density;

● The change of redox potential during charge and discharge should be as small as possible, so that the battery has a longer charge and discharge platform;

● There is no or little change in the structure during charging and discharging, so that the battery has good cycle performance;

● It has high electronic conductivity and ionic conductivity, reduces electrode polarization, and makes the battery have good rate discharge performance;

● Good chemical stability, no side reactions with electrolytes;

● It has the characteristics of low price and environmental friendliness;

Types of anode materials

There are many kinds of anode in lithium ion battery. The following is a detailed introduction of various anode in lithium ion battery.

Lithium cobalt oxide

The appearance of lithium cobaltate(LiCoO2) is gray-black powder. It has the advantages of high voltage, stable discharge, high filling density, good cycle performance and suitable for large current discharge.

However, its anti-overcharge and high temperature safety performance is not good. In addition, Co resources are scarce, costly, and somewhat toxic.

Due to its high mass specific energy, lithium cobalt oxide is currently mainly used in small high-energy batteries, such as mobile phones and notebooks.

NCM

Ternary materials have higher capacity and lower cost than LiCoO2, are safer and easier to synthesize than LiNiO2, are more stable than LiMnO2 and have the advantages of price and environmental friendliness.

Therefore, ternary materials have good market prospects and are currently mainly used in small lithium-ion batteries and power lithium-ion batteries. Typical ternary materials include nickel-cobalt-aluminum ternary material NCA (LiNi0.8Co0.15Al0.05O2 ).

LiMn2O4

The advantages of spinel structure lithium manganese oxide (LiMn2O4) are high voltage, good anti-overcharge performance, good safety performance, and easy preparation. At the same time, Mn is rich in resources, cheap, non-toxic and pollution-free.

The disadvantage is that the specific capacity is low and the space for improvement is small, and the lattice distortion is serious under deep charge and discharge and high temperature conditions, resulting in poor cycle performance. At present, LiMn2O4 is mainly used in power lithium-ion batteries.

Lithium iron phosphate

Lithium iron phosphate (LiFePO4) has an olivine crystal structure, excellent stability, cycle performance and safety performance, easy to obtain raw materials, cheap price, non-toxic and non-polluting, etc.

Its disadvantages are low specific capacity, low voltage, low filling density, poor high-current performance, poor low-temperature performance, and poor product consistency because it cannot be synthesized in air. At present, lithium iron phosphate is mainly used for large-scale energy storage lithium-ion batteries.

Lithium-ion battery anode material production process

The following is the general preparation method of anode in lithium ion battery.

Solid phase method

Generally, lithium salts such as lithium carbonate and cobalt compounds or nickel compounds are ground and mixed for sintering reaction. The advantage of this method is that the process flow is simple and the raw materials are easy to obtain.

The disadvantage is that the prepared positive electrode material has limited capacitance, poor mixing uniformity of raw materials, and poor performance stability of the prepared material.

Complex method

The complex method uses organic complexes to prepare complex precursors containing lithium ions and cobalt or vanadium ions, and then sinters them.

The advantages of this method are molecular scale mixing, material homogeneity and property stability. At present, there have been experimental methods for industrialization of lithium-ion batteries, but the technology is not yet mature.

Sol-gel method

Using the method of preparing ultrafine particles developed in the 1970s, the positive electrode material was prepared. The method has the advantages of the complex method, and the capacitance of the prepared electrode material is greatly improved.

The disadvantage is that the cost is high, and the technology is still in the development stage.

Ion exchange method

The LiMnO2 prepared by the ion exchange method has obtained a high reversible discharge capacity of 270mAh/g. This method has become a new research hotspot. It has the characteristics of stable performance and high capacitance of the electrode.

However, the process involves energy-consuming and time-consuming steps such as solution recrystallization and evaporation, and there is still a considerable distance from practical application.

Anode material market

From the perspective of the product structure ofanode materials, the shipment of lithium iron phosphateanode materials reached 1.11 million tons, an increase of 132%, accounting for 59% of the market; the shipment of ternaryanode materials was 640,000 tons, a year-on-year increase of 47%, accounting for 34% of the market ;

The shipments of lithium manganese oxide and lithium cobalt oxide were 69,000 tons and 77,000 tons respectively, both showing a significant decline compared with before.

The main reasons for the rapid growth of lithium iron phosphate material shipments are:

● The improvement of the comprehensive technical performance of batteries and modules will drive the cost-effectiveness of lithium iron phosphate batteries, and drive the penetration rate of corresponding batteries to increase, which in turn will drive the increase in shipments of corresponding materials.

● China’s energy storage batteries basically use lithium iron phosphate batteries, driving the increase in shipments of lithium iron phosphateanode materials.

● Ternary lithium battery technology still needs to be improved.