Li(NiCoMn)O2-material-knowledge-and-safety-improvement

Li(NiCoMn)O2 material knowledge and safety improvement

Lithium-ion battery has developed rapidly in recent years. With its high energy density, good multiplier performance and cycle performance, it has become the main power source of electric vehicles, occupying a very important place in new energy, and also put forward a new development path for global energy and environmental problems.

Nickel cobalt manganese oxide lithium (Li(NiCoMn)O2) ternary battery cathode material is one of the cathode materials with the highest energy density under development, with significant performance advantages, and is one of the most important development directions of vehicle power battery cathode materials in the future.

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What is the Li (NiCoMn) O2?

Ternary nickel-cobalt-manganese materials usually refer to Li (NiCoMn) O2. This material has a ternary synergistic effect, and its electrochemical performance is better than any single material, combining the cycle stability of LiCoO2, the high specific capacity of LiNiO2, and the thermal stability, safety and low price of LiMn2O4.

Increasing the nickel content in the nickel-cobalt-manganese ternary materials can improve the reversible lithium embedding ability of the material. However, the phenomenon of cation mixing is prone. As the nickel content increases, the more severe the mixture of nickel and lithium in the material, the irreversible capacity loss occurs.

It is mainly used in new energy vehicles, electric motorcycles, electric bicycles, electric tools, energy storage, sweeping robots, unmanned aerial vehicles, intelligent wearable devices and other fields.

Advantages and disadvantages of Li (NiCoMn) O2

Advantages of Li (NiCoMn) O2

(1) High energy density, the theoretical capacity reaches 280 mAh / g, and the actual capacity of the product exceeds 150 mAh / g;

(2) Good circulation performance, with excellent circulation stability at room temperature and high temperature;

(3) The voltage platform is high, stable and reliable within the 2.5-4.3/4.4V voltage range;

(4) Good thermal stability, and stable thermal decomposition of the material under the 4.4V charging state;

(5) Long cycle life, 1C cycle life of 800 times to maintain the capacity of more than 80%;

(6) Ideal crystal structure, small self-discharge, no memory effect and other outstanding advantages.

From the characteristics of Li (NiCoMn) O2, ternary lithium battery has high energy density, high voltage, and long life, which is especially suitable for electric motorcycle battery pack.

Disadvantages of Li (NiCoMn) O2

(1) The preparation conditions are very harsh, and the commercial production is difficult.

(2) Poor thermal stability and poor cycle performance.

Advantages-and-disadvantages-of-Li-(NiCoMn)-O2

Price factor of Li (NiCoMn) O2

Raw materials

The lithium salt market is short of ore and raw materials, the output has not yet increased, the spot is difficult to find, the current market demand is weak, considering the downstream tolerance, the price has fallen; the price of nickel sulfate market is still strong and weak; the cobalt salt terminal demand is still depressed, the operator mentality is bearish, and the smelter accompanied the offer price fell.

Demand

Affected by the end demand cathode material production sentiment is strong, downstream battery factory procurement plan slowed down. With the cancellation of state subsidies, the future market uncertainty is still strong.

Production

The output of some enterprises has declined in November, the overall supply month-on-month decline in about 5%, while the downstream procurement demand continues to slow down, the performance in December may be more obvious.

Modification method of Li (NiCoMn) O2

With metal oxide (Al2O3, TiO2, ZnO, ZrO2, etc.) modification Li (NiCoMn) O2 surface, make the material and the electrolyte machinery, reduce material and electrolyte side reaction, inhibit the dissolution of metal ions.

ZrO2, TiO2 and Al2O3 oxide coating can prevent impedance during charging and discharging of lithium ion battery, improve the material cycle performance resistance, including ZrO2 coating caused material surface increase minimum, Al2O3 coating will not reduce the initial discharge capacity.

How-to-improve-the-safety-of-Li-(NiCoMn)-O2

How to improve the safety of Li (NiCoMn) O2?

From the perspective of energy density, Li (NiCoMn) O2 has absolute advantages over LFP and LMO, but safety performance is a problem that has always limited its large-scale application.

It is difficult to want a large capacity pure ternary lithium battery to pass the safety test, so the large capacity battery is generally used together with lithium manganese oxide. According to the collected data, there are mainly the following solutions to solve the ternary safetyy problem:

1. Select the Li (NiCoMn) O2 with the optimal ratio of safety performance

As we all know, the higher the nickel content in Li (NiCoMn) O2, the worse the stability of the material, and the worse the safety. At present, the ratio of the best safe ternary nickel cobalt manganese is 1:1:1, that is, usually called 111 ternary, the 111 ternary has the best stability, mainly because:

1) The proportion of nickel is relatively low (relative to 422 / 523, etc.), so it is easier to form a complete layered structure in the material preparation process, while taking into account the energy density.

2) The proportion of manganese is relatively high (relative to 422 / 523, etc.), and manganese is an important element in the structural stability of Li (NiCoMn) O2.

3) The ratio of nickel and manganese is 1:1, and both nickel and manganese are the positive 2 valence and positive 4 valence with the highest stability.(Here, 111 ternary is the most suitable for high voltage Li (NiCoMn) O2, if the high voltage electrolyte bottleneck breakthrough, its energy density will not be inferior to any high nickel ternary, and the cycle and electrode processing performance are several grades higher.)

In conclusion, 111 ternary in the large capacity pure ternary battery has the best safety.

Improvement-from-Li-(NiCoMn)-O2-itself

2. Improvement from Li (NiCoMn) O2 itself

Li (NiCoMn) O2 itself is a new material developed from doping. If other elements are doped in the ternary, it will not only have an impact on its electrochemical properties, but also put forward more requirements for the preparation process. The increase of cost will also limit the application of ternary in the power.

The coating process will have an impact on the consistency of the product, so the best way to improve the safety performance of the material is based on the premise of making the product suitable for industrialization.

Li (NiCoMn) O2 is a primary particle similar to lithium cobalt oxide. In addition to its great advantages in compaction density and electrode processing performance, it has also improved safety for the following reasons:

1) The micron-level primary particles have a more complete layered structure. The more complete the layered structure, the better the stability of the material, which is reflected in the improvement of cycle performance and safety performance.

2) Primary particles with large particle size have better kinetic stability.

3) Another advantage of making the particle size larger is that it reduces the specific surface area and reduces the side reaction caused by the material contact with the lithium ion battery electrolyte and the destruction of the material structure, which is very helpful to the circulation and the material stability.

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