In-Depth Analysis of Battery Materials NCM111/523, NCM622

Compared with ternary materials and other positive electrode battery materials for energy storage and power batteries such as lithium manganese oxide and lithium iron phosphate, layered multi-element materials have the characteristics of high specific capacity, high tap density, high energy density and good safety performance. They have been widely used in laptop computers, children’s toys, portable power tools, electric bicycles, drones, electric cars, electric buses and other markets, and have been developed for energy storage and other new application areas.

Layered multi-element materials combine the advantages of high capacity of lithium nickel oxide, high rate of lithium cobalt oxide and high stability of lithium manganese oxide. The atomic structures of transition metals such as Ni, Co, and Mn in Group VIII are similar and their chemical properties are similar. In principle, they can form lithium-containing composite metal oxides in any proportion to form a series of nickel-cobalt-manganese oxide multi-element materials with different properties.

According to their performance characteristics and relative advantages, they can be used in different market segments to meet the special needs of different application scenarios. Common commercial multi-element material grades include NCM111, NCM523, NCM622, NCM811, NCA, etc.

1. NCM111 and NCM523 with medium and low nickel content

Among the layered multi-element materials, NCM111 low-nickel materials are the earliest proposed material composition, and therefore have been studied most deeply.

Among them, transition metal elements such as Ni, Co, and Mn have the same composition ratio, and have the performance advantages of high rate, long cycle, and high safety. Because the content of Ni and Mn is equal, it is generally believed that they exist in the form of Ni2+ and Mn4+ after electron migration, and there is no excess Ni3+, so NCM111 is the easiest to prepare among the multi-element materials.

Its Co content is relatively high, which is beneficial to the high current charge and discharge rate characteristics, but it also brings the problem of high material cost. NCM424 (LiNi0.4Co0.2Mn0.4O2) was also introduced to the market early, which also took advantage of the characteristics of equal Ni and Mn content, but due to the high Mn content, the prepared hydroxide precursor is easy to oxidize, the crystal is not easy to grow and densify, and there is no capacity advantage, so it has not really entered the market in large quantities.

The comprehensive performance of NCM111 is closest to that of LCO. It is relatively easy to prepare and has low environmental requirements for battery pulping. It can be used alone or mixed with other positive electrode materials. It was widely used in the early application markets of mobile phones, laptops, power tools, etc.

Sony Corporation of Japan first used it to replace LCO in 2004 to increase capacity and reduce costs, such as

2.55A·h high-capacity 18650 cylindrical batteries (model US18650G8) used alone as positive electrodes for high-end laptops;
Physically mixed with LMO, used in 1.6A·h US18650V and 2.5A·h US26650VT for power tools;
Mixed with LCO in mobile phone battery Nexelion;

Currently, it is mainly used in special applications such as 48V start-stop systems with high power density requirements.

Compared with NCM111, NCM523 has higher specific capacity, lower cost and similar thermal stability, making it the most widely used ternary material in the market.

Although the Ni content is high (up to 50%), most of it is + 2-valent nickel in the form of LiNi0.5Mn0.5O2, and + 3-valent nickel LiNiO2 accounts for only 20%. Therefore, NCM523 is a typical medium-nickel material, which can be prepared in an air atmosphere like lithium cobalt oxide and NCM111. After nearly ten years of process optimization, various models of NCM523 products designed for different market segments have been developed one after another, and the maturity and stability of the process have been continuously improved. It is widely used in many fields such as laptops, power banks, power tools, electric bicycles, hybrid electric vehicles, and pure electric vehicles.

NCM523 material developed by a company for market segmentation (for reference only)
Product model	5YN	5Y3	5ES	5E12	5E5	5EB-10	5SC
Application field	Laptop	Power tools	Energy storage	Pure electric vehicles	Hybrid electric vehicle	Pure electric/plug-in hybrid	Pure electric vehicles
Product type	Single Distribution Reunion	Dual distribution reunion	Dual distribution agglomeration	Single distribution reunion	Single distribution reunion	Dual distribution reunion	Single crystal
Doping	None	None	Yes	Yes	Yes	Yes	Yes
Coating	None	None	Yes	Yes	Yes	Yes	Yes
D50/um	12.0	9.5	15.6	12.0	4.4	9.5	5.2
Tap density/(g/cm3)	2.52	2.56	2.64	2.50	1.75	2.55	2.27
Powder compaction density/(g/cm3)	3.38	3.39	3.63	3.25	3.20	3.34	3.30
Li2CO3 content/%	0.09	0.10	0.08	0.05	0.07	0.08	0.08
LiOH content/%	0.11	0.10	0.10	0.07	0.08	0.10	0.06
0.2C specific capacity/(mA·h/g)	169.1	169.7	164.9	168.8	169.5	169.0	169.3
1.0C specific capacity/(mA·h/g)	158.7	159.6	154.2	158.7	159.6	159.0	156.8
1.0 C capacity retention rate (button type, 100 cycles @4.5~3.0V)/%	91.6	93.2	96.8	95.5	95.0	95.3	95.2

2. NCM622, NCM811 and NCA with high nickel content

The 0.1C specific capacity of NCM622 multi-element material is about 180mA·h/g, which is nearly 10mA·h/g higher than that of NCM523. The proportion of LiNiO2 in NCM622 has reached 40%, and its preparation difficulty is much higher than that of NCM111 and NCM523.

This material has a high specific capacity and good processing performance. It has been industrialized and used in cylindrical batteries for high-end laptops and batteries for pure electric vehicles with high energy density.

The 0.1C specific capacity of NCM811 multi-element material is more than 200mA·h/g, which is 30mA·h/g higher than NCM523. The increase in nickel content and the decrease in cobalt content make NCM811 expected to get rid of the raw material cost dilemma caused by the shortage of cobalt resources. However, LiNiO2 in NCM811 has become the main component, accounting for up to 70%, and must be prepared in a pure oxygen atmosphere to ensure that more nickel exists in + 3 valence.

In addition, the material is sensitive to environmental humidity. It is easy to absorb moisture during production, transportation, storage, and use, resulting in cation mixing and precipitation of excessive residual lithium compounds on the surface of particles. These residual lithiums make the pH higher, which is easy to increase the viscosity of the slurry during battery slurrying, and even become jelly-like, making it difficult to adjust the slurry and coat the pole piece.

Unlike the previous multi-component materials, most of the NCM811 sold on the market is not strictly prepared according to the composition of Ni∶Co∶Mn = 8∶1∶1. The Ni content may be 78%, 83%, 85% or 88%, etc., in order to pursue higher specific capacity and relatively stable structure, and finally achieve comprehensive indicators such as good processability, high energy density, long cycle life, high safety, and high cost performance.

The 0.1C specific capacity of NCA layered battery materials reaches more than 200mA·h/g, which is close to NCM811. Al can effectively stabilize the structure of the material and inhibit the common metal ion mixing of high-nickel materials, but the content in the material cannot be too high, otherwise it will cause a lot of capacity reduction. LiNiO2 in NCA is the main component of the solid solution, accounting for more than 80%, and must also be prepared in a pure oxygen atmosphere to ensure that all nickel exists in + 3 valence. In addition, the material is also easy to absorb moisture, and more residual lithium compounds are easily precipitated on the surface of the particles, which has an adverse effect on battery pulping and high-temperature storage.

Similar to NCM811, most NCAs sold on the market are not strictly prepared according to the composition of Ni∶Co∶Al = 80∶15∶5. When the nickel content is the same as NCM811, since the Al content cannot be too high, more Co can only be added, resulting in higher material costs and no market competitive advantage. Therefore, NCA is suitable for high-capacity battery applications with higher nickel compositions, such as nickel content reaching 89%, 92% or 95%, in order to achieve application development goals such as high energy density, high safety, long life, and high cost performance. In recent years, NCM/NCA products with different nickel contents have been developed one after another to meet the needs of various segmented application markets in multiple fields such as power tools, hybrid electric vehicles, and pure electric vehicles.