Traditionally, we say ternary material generally refers to the nickel-cobalt-manganese lithium NCM cathode material (in fact, there are negative ternary materials), Ni, Co, Mn, three kinds of metal elements can be drawn in accordance with different proportions of different types of tris Meta material.

The formula is LiNi1-x-yCoxMnyO2, the common ratio of 111,424,523,622,811, we note that the above ratio is N: C: M, the Chinese and foreign names are not the same.

In addition to say that NCA materials are often mentioned together with the NCM, but accurate to be considered binary Ni material, can not be classified as ternary material.

Chemical coprecipitation method: Generally, the chemical raw materials are mixed in a solution state, and an appropriate precipitating agent is added to the solution so that the components that have been uniformly mixed in the solution are coprecipitated stoichiometrically or precipitated in the solution first An intermediate product, and then calcined and decomposed to prepare a fine powder.

Chemical coprecipitation method is divided into direct chemical coprecipitation and indirect chemical coprecipitation.

The direct chemical coprecipitation method is that the salts of Li, Ni, Co and Mn are simultaneously coprecipitated, filtered, washed and dried, and then calcined at a high temperature. Indirect chemical coprecipitation is the first synthesis of Ni, Co, Mn ternary mixed coprecipitation, and then filtered and washed and dried, mixed with lithium salt sintering, or in the formation of Ni, Co, Mn ternary mixed coprecipitation without filtration The solution containing the lithium salt and the coprecipitation is evaporated or freeze-dried, and then the dried material is calcined at a high temperature.

Compared with the traditional solid-phase synthesis technology, coprecipitation method can make the material reach molecular or atomic linear stoichiometry mixing, easy to get a small size, mixed precursor, and the calcination temperature is low, the synthesis product component Uniform, reproducible, easy to control conditions, simple operation, commercial production using this method.

Solid-phase synthesis: Nickel, cobalt, manganese and lithium hydroxide or carbonate or oxide as a raw material, according to the amount of the corresponding material preparation and mixing, calcined at 700 ~ 1000 ℃, to obtain the product. The method mainly adopts mechanical means for mixing and refining the raw materials, which easily leads to uneven microscopic distribution of the raw materials and makes the diffusion process difficult to be carried out smoothly. Meanwhile, impurities are easily introduced during the mechanical refining process, and the calcining temperature is high and the calcining time is long , The reaction steps and more, energy consumption, serious lithium loss, difficult to control the stoichiometric ratio, easy to form heterophase, product composition, structure, particle size distribution there is a big difference, so the electrochemical performance is not stable.

Sol-Gel Method: The raw material solution is mixed uniformly to form a uniform sol, which is then gelled, shaped during the gel process or after the gel, dried, and then calcined or sintered to obtain the desired powder material. Sol-gel technology requires simple equipment and easy process control. Compared with the traditional solid-phase reaction method, sol-gel technology has lower synthesis and sintering temperature, and can produce materials with high chemical uniformity and high chemical purity. However, the synthesis cycle is relatively long, The synthesis process is relatively complicated, the cost is high, and industrialization is more difficult to produce.

The role of the three elements and advantages and disadvantages

The introduction of 3 + Co: to reduce the mixed cation occupy, stabilize the material layer structure, reduce the impedance value, increase the conductivity, improve cycle and rate performance.

The introduction of 2 + Ni: can improve the material capacity (to improve the volume energy density of the material), and due to the similar radius of Li and Ni, too much Ni will be dislocated with Li Li led to lithium-manganese mixing, lithium layer The greater the nickel ion concentration, the more difficult it is for the lithium to be de-intercalated in the layered structure, resulting in poor electrochemical performance.

The introduction of 4 + Mn: not only can reduce the material costs, but also can improve the material safety and stability. But too high Mn content will be prone to spinel phase and destroy the layered structure, so that capacity reduction, cycle attenuation.

Ternary material modification method?

The surface of the ternary material is modified with metal oxides (Al2O3, TiO2, ZnO, ZrO2, etc.) to mechanically separate the material from the electrolyte, reduce the side reaction between the material and the electrolyte, and inhibit the dissolution of metal ions. The ZrO2, TiO2 and Al2O3 oxides In the process of charge and discharge, the coating can prevent the impedance from increasing and improve the cycling performance of the material. The ZrO2 coating has the least increase of the surface resistance of the material, and the coating of Al2O3 does not reduce the initial discharge capacity.

How to improve the safety of ternary materials?

In terms of energy density, ternary materials have an absolute advantage over LFP and LMO, but safety is a problem that has been limiting its large-scale application.

Pure ternary battery capacity larger difficult to pass safety tests such as acupuncture and overcharge, which is also commonly used in high-capacity batteries mixed lithium manganese oxide together. From what I have learned, there are mainly several solutions to solve the ternary security problem:

1. Select the best safety performance of the ternary material

As we all know, the ternary material in the higher nickel content, the worse the stability of the material, the safety is also worse, the current best security of the mainstream ternary nickel cobalt cobalt and manganese ratio of 1: 1: 1, Said 111 ternary, 111 Ternary The reason why the stability of the best, mainly because:

1) The low proportion of nickel (relative to 422/523, etc.) makes it easier to form a complete layered structure during material preparation, taking into account the energy density.

2) a higher proportion of manganese (relative to 422/523, etc.), manganese is an important element of its structural stability in ternary materials.

3) The ratio of nickel to manganese is 1: 1. Nickel and manganese are simultaneously the most stable positive 2-valent and 4-valent. (Here to say, 111 ternary is the most suitable for high-voltage ternary material, if the high-voltage electrolyte bottleneck breakthrough, its energy density will not be inferior to any high-nickel ternary, cycle and electrode processing performance should High several grades.)

In summary, in the high-capacity pure ternary battery, 111 ternary with the best security.

2. From the ternary material itself to improve

Ternary material itself is a new material developed from the doping, we believe that if the ternary doped with other elements, not only will have an impact on the electrochemical properties so far, but also on the manufacturing process to make more requirements, costs Of the same will limit the application of ternary in power, and the coating process will have an impact on the consistency of the product, so we believe that to ensure that the product is suitable for industrialization of the material to improve the safety performance is able to make the three Yuan really applied to the best way in the battery.

So here only to talk about our improvement program, said many times before, our ternary material is a particle similar to lithium cobalt oxide, in addition to the compaction density and electrode processing performance has a great advantage, There is also an increase in security for the following reasons:

1) The micron-sized primary particles have a more complete lamellar structure. The more complete the lamellar structure, the better the stability of the material, which is manifested by the improvement of cycle performance and safety performance.

2) a larger particle size has a better dynamic stability of the particle, before I heard that a joint venture company claimed that with Japan's nano-ternary material to make the battery safety how the performance of what, at least in my opinion To propagandize the effect is negative, since the publicity of nanomaterials should focus on promotion of rate performance to circumvent safety, because the nanoscale material itself has a high activity, nanomaterials make the material stability and safety to varying degrees Reduction, I mentioned the micron level, is different from the nanoscale.

3) Another advantage of increasing the primary particle size is to reduce the specific surface area and reduce the material damage due to the side reaction caused by the contact with the electrolyte, which is very helpful for the circulation and material stability.

Nonetheless, we consider the ternary material's safety in batteries as its own nature. Like the high temperature of lithium manganate, the morphology control has been done even though the 3V platform of lithium manganese oxide is completely eliminated by thorough modification A lot of optimization, still need to match the electrolyte and anode to fully meet the high temperature performance requirements.

Reduce the battery charge cap voltage At present, a domestic enterprise has solved the safety problem of pure 35Ah pure ternary battery, the upper limit voltage of the charge is 4.1V, so that the stability of the entire battery system has a very good improvement.

By making polymer pure ternary battery to improve battery safety Here is the true sense of the solid polymer electrolyte lithium-ion battery, rather than the usual sense of the soft battery

①, ceramic alumina coating, Al2O3 through the formation of Al-O-F and Al-F layer can consume HF in the battery system, the charging voltage can be increased to 4.5V;

②, control the content of Ni in a reasonable range (811, of course, more stable than 622);

③, to participate in the miscellaneous other metal elements (Al, Mg, Ti, Zr) These appropriate miscellaneous cladding materials can improve the structural stability, thermal stability and cycle stability.

Second, in conjunction with other materials in the battery system also work hard to study:

①, the electrolyte added high boiling point and flash point of the flame retardant additives, common organic phosphorus, fluorinated phosphate series;

②, the choice of ceramic membrane to improve the thickness of the membrane substrate and coating, the use of new high temperature shrinkage of non-woven materials.

In addition, there are common mixed use of different cathode materials to achieve complementary effects, such as ternary hybrid lithium manganese oxide to improve battery safety. Personally think that the domestic short-term large-scale application of the ternary material for the 622 system, a higher system and even the NCA power battery system with the existing state of the art is difficult to control

Each lithium battery material and lithium battery itself is complicated, so there is no perfect material, there is no perfect process, only continuous optimization and continuous improvement of communication.