Introduction of Three-way Lithium Power Battery System

It is well known that in recent years, with its high capacity, good cycle stability and moderate cost, the power lithium battery, which is used as a positive electrode material, has gradually occupied an increasingly important position in the power battery industry.

At the Shanghai International Auto Show in 2015, the share of lithium ion batteries in the new energy vehicles exceeded that of lithium iron phosphate batteries. Most domestic mainstream car companies, including Geely, Chery, Chang 'an, Zhongtai, and China, have launched new energy models with three power batteries. For example, Beiqi EV series, Qirui Q, Airuize 3EV, JianghuaiiEV4, Jilidihao 100, including Chen Yuyun EV and so on. So what is the reason for the increasing strength of ternary material batteries?

As mentioned in the previous article "Hand in Hand", the performance of lithium-ion batteries depends mainly on their cathode materials, and lithium-ion batteries are usually named after cathode materials. Most of the ternary material batteries on the market refer to lithium ion batteries with nickel cobalt manganese as the positive material.

It has been found that the ratio of nickel cobalt manganese in nickel cobalt manganese tripole material can be adjusted within a certain range, and its performance varies with the ratio of nickel cobalt manganese. Therefore, in order to further reduce the content of high-cost transition metals such as cobalt nickel and further improve the performance of positive polar materials, countries around the world have done a lot of work on the research and development of nickel cobalt manganese ternary materials, A number of ternary material systems with different ratio of nickel cobalt manganese are proposed, including 333, 523, 811 systems. Some systems have successfully achieved industrial production and application.

Structural characteristics of nickel cobalt manganese ternary positive electrode

Nickel-cobalt manganese ternary materials can usually be expressed as: LiNix Coy MnzO2, where X + Y + Z = 1.

Depending on the molar ratio(X: Y: Z ratio) of the three elements, they are respectively referred to as different systems, such as a ternary material consisting of molar ratios of nickel to cobalt manganese (X: Y: Z) 1:1:1, Referred to as 333; The system with a molar ratio of 5:2:3 is called the 523 system.

The triplet materials of Type 333, Type 523 and Type 811 belong to the α-NaFeO2 layered rock salt structure of the hexagonal system.

In nickel-cobalt manganese ternary materials, the main valence States of the three elements are +2, +3, and +4, respectively, and Ni is the main active element. The reaction and charge transfer when charging are as follows:

Positive reaction: LiMO2-→ Li1-xMO2 + xLi + XE-

Negative reaction: nC+xLi + XE-→ LixCn

Total battery reaction: LiMO2 + nC-→ Li1-xMO2 + LixCn

In general, the higher the content of the active metal component, the larger the material capacity, but when the content of Ni is too high, it will cause Ni2 + to occupy the Li + position, exacerbating the cation mixing, resulting in a decrease in capacity. Co is also an active metal, but it can play a role in inhibiting cation mixing, thereby stabilizing the material's layered structure; Mn does not participate in electrochemical reactions, providing safety and stability while reducing costs.

Characteristics of Different Systems of Nickel Cobalt Manganese Three-phase Lithium-ion Battery

There are many nickel-cobalt manganese ternary system batteries on the market today, such as 523, 111, 811 systems, etc.

As a vehicle powered battery, the market has imposed more and more stringent requirements on its energy density. However, fish and bear Palm can not be obtained at the same time. From Figure 2, it can be seen that if you want to obtain a high-energy density and safe and stable power cell, you must increase the proportion of Ni and Co in the ternary material. Accompanied by the security risks caused by Ni's lively characteristics and the increase in costs caused by the lack of Co resources.

For each system of nickel cobalt manganese ternary batteries, also do a simple introduction here.

LiNi 0.5 Co 0.2 Mn 0.302

Type 523 ternary material is the most used ternary material at present, because it has higher specific capacity and thermal stability, and the maturity and stability of the process continue to increase, and the domestic market share has rapidly expanded. The 523 ternary material pursues high volume and high specific capacity(high compaction density), followed by a balance between cycle performance, rate performance, thermal stability, and self-discharge. As a power battery, it can greatly improve the endurance of power tools. ability.

LiNi1/3Co1/3 Mn1/302

The type 111 ternary material has the advantages of energy, multiplier, recyclability, and safety performance. However, the first charge and discharge efficiency of the 111 material is low, and the mixing of ions in the lithium layer affects the stability of the material and the discharge voltage platform. low. At present, improving the vibration density, high and low temperature, and cycle stability and ratio performance of LiNi1/3Co1/3 Mn1/302 material has become a hot spot in the research of this material. The power cell prepared by type 111 ternary material has a high capacity, circularity, magnification, low temperature discharge, charge retention ability, and safety performance, and can meet the requirements of EV and HEV for power cells.

LiNi 0.8 Co0.1 Mn 0.102

811 This material has the advantages of high capacity and low price because of its high Ni content and low Co content, but it is also more difficult to achieve the same stability as the 111 system. Because Ni content is too high, its manufacturing cost will also increase. This Ni series material also has high environmental requirements for the production of batteries. 811 batteries require the cooperation of high voltage 's electrolyte. Therefore, the manufacturing process of 811 series materials is the focus of current research. At present, 811 is a high Ni-based material that is better done in Japan and South Korea, such as Sumitomo and other companies in Japan. There are many domestic manufacturers, such as Bangpu and Dahua. Most of them are only in the experimental stage, and the scale of mass production has not yet been formed.

2.4 LiNi 0.6 Co 0.2 Mn0.202

When the higher the Ni content than the higher the capacity, the importance of the material gradually appears when the Ni content reaches more than 60 %. The specific capacity of the 622 nickel-cobalt manganese ternary lithium battery is higher than that of the 523 type, the gram capacity can reach 160 mA hours or more, and even in the case of high voltage, it can reach 180 mA, and the processing performance is good. The development of 622 types of materials is the focus of current industrial development and is also very suitable for EV batteries with high energy density.

Present Situation and Development of Three-way Lithium-ion

On a global scale, lithium ion batteries currently account for more than 80 % of the global lithium ion battery market, and occupy more than 81 % of the battery market for electric vehicles that require higher output and safety. In contrast to the domestic market, domestic power battery shipments reached 15.7 GWh in 2015, of which lithium iron phosphate batteries still dominated, accounting for nearly 69 % of the market; Battery shipments of ternary materials accounted for 27 %. In terms of further subdivision, in the passenger car field, battery types are dominated by ternary materials, and battery shipments reach 1.93 GWh; In the passenger car field, it is mainly equipped with lithium iron phosphate batteries, accounting for 84 % of the battery volume of pure electric passenger cars[ 5] And ...

January 24, this year, the ministry of industry and information technology on the ternary battery "suspension subsidy" policy, although the ternary lithium battery manufacturers of the first hit, but also to this market has imposed certain restrictions. At present, the quality of ternary battery products in domestic power battery plants is indeed uneven. The stability of ternary materials itself is weaker than that of lithium iron phosphate, especially with complex process requirements. For security reasons, this "suspension" policy also regulates the industry and the market from a certain angle, which is a certain necessity.

However, in the field of lithium batteries, the energy density, low temperature characteristics, power characteristics, and high temperature storage properties are all superior to other materials, and they will surely become a non-negligible force for lithium battery positive electrode materials. It is expected that its thick and thin hair!

The page contains the contents of the machine translation.