Power battery technology is undergoing a profound change. After lithium iron phosphate batteries and ternary lithium batteries, quaternary lithium batteries have also entered the industry's sight this month.
On March 4, 2020, at GM’s “EV?week” event, GM and its partner LG Chem launched a new battery product Ultium.
▲Universal New Battery Pack
The core of this product is not the battery pack technology that has been praised by the outside world. The key is that the Ultium battery cells will use LG Chem The latest developed NCMA quaternary lithium battery.
The technical principle of this battery is to mix a small amount of aluminum element into the NCM ternary lithium cathode material, so that the originally active high-nickel ternary cathode material can maintain high energy density while also Maintain a more stable state.
It can be considered that NCMA quaternary lithium batteries have solved many of the difficult problems faced by current ternary lithium batteries.
Compared with NCM/NCA ternary cathode materials, NCMA quaternary cathode materials after multiple rounds of charge and discharge cycles, H2-H3 (referring to the increase in micro-cracks in the cathode material to a state that is difficult to recover, causing internal The irreversible phase transition voltage (parameter changes) remains stable, there are fewer microcracks inside the material, and the dissolution of transition metals in the cathode material is not obvious. At the same time, the NCMA cathode material has a higher peak heat release temperature and stronger thermal stability.
It is worth noting that among the NCMA quaternary cathode materials, the content of the most expensive cobalt element has dropped from 20 in NCA/NCM? 622 to 5, further reducing the cost. According to the figures released by LG and GM, the mass production cost of NCMA quaternary batteries is US$100 (approximately RMB 694). Previously, the mass production cost of LG Chem NCM?622 was approximately US$148 (approximately RMB 1,027). .
High energy density, high stability, and low cost are features that were originally difficult to achieve on NCA/NCM ternary lithium batteries, but are achieved on NCMA quaternary lithium batteries. For power battery products, NCMA’s Mass production will set off a wave of technological route upgrades.
In this wave, the products provided by upstream mining and midstream material manufacturers to downstream must be rapidly iterated, and power battery companies must also make new choices in their technical routes, while new energy vehicle manufacturers must It is necessary to adapt vehicle models to new battery technologies, and the entire new energy industry chain will be greatly affected.
1. Decrypt the principle of NCMA battery technology? It has become an effective solution for high energy density batteries
NCMA quaternary lithium battery is not a brand-new power battery technology.
From the perspective of material composition, this technology is based on a mixture of the two current mainstream ternary lithium battery systems, NCM and NCA.
From the perspective of battery structure, it does not change the main structure of the battery like solid-state batteries, lithium-sulfur batteries, and lithium-air batteries.
But this technology has the potential to lead ternary lithium batteries to the next stage.
▲The battery developed by General Motors and LG?
Essentially, the so-called NCMA quaternary lithium battery is a battery system that uses NCMA quaternary cathode material.
The principle is to mix a trace amount of transition metal aluminum into the original NCM ternary cathode material to form a quaternary cathode to ensure the stability and cycle life of the battery while enriching the nickel element in the cathode. Not affected.
During this transformation process, the original Li[Ni-Co-Mn]O2 cathode material system of the NCM ternary system became Li[Ni-Co-Mn-Al]O2 (cathode material chemical composition has changed).
The Al-O chemical bond formed by the addition of the transition metal aluminum element is much stronger than the Ni(Co, Mn)-O chemical bond, which chemically enhances the stability of the positive electrode, thus making the NCMA quaternary battery The voltage of the H2-H3 irreversible phase change remains stable after multiple cycles, and the Li element does not easily release oxygen during the deintercalation process of the cathode, reducing the dissolution of transition metals and improving the stability of the crystal structure.
The stable crystal structure reduces the formation of micro-cracks in the cathode material during the charge and discharge cycle, and the rise rate of the cathode impedance is suppressed.
At the same time, studies have shown that the exothermic peak reaction temperature of NCMA cathode material is 205 degrees Celsius, which is higher than the 202 degrees Celsius of NCA cathode material and the 200 degrees Celsius of NCM cathode material. This means that the NCMA cathode material Thermal stability is better.
This characteristic is very critical for the current high-nickel route of power battery cathodes.
As the market demand for the cruising range of electric vehicles has increased from less than 300 kilometers in the early days to 600 kilometers today, the energy density of ternary lithium batteries continues to increase, and the high-nickel route continues to be clarified.
▲The Model 3 using new batteries will have a range of nearly 600 kilometers
At this stage, in the NCM/NCA 811 ternary lithium battery, the molar ratio of the active material nickel in the positive electrode has been More than 80%, this type of battery is called 8 series ternary lithium battery.
After the 8-series ternary lithium batteries, the 9-series ternary lithium batteries with a nickel content exceeding 90% are gaining momentum. According to Gaogong Lithium Battery, GEM, a well-known lithium battery material supplier, has completed the research and development and mass production of ternary precursor materials such as Ni90, Ni92, and Ni95 with molar ratios of nickel elements reaching 90, 92, and 95 respectively.
However, behind the seemingly bright technological prospects, hidden worries are constantly emerging.
Research has shown that with the enrichment of nickel in the cathode material of ternary lithium batteries, the capacity retention capacity and thermal stability of the battery have declined.
When the nickel content of the NCM ternary lithium battery cathode exceeds 60, and the nickel content of the NCA ternary lithium battery cathode exceeds 80, after a certain number of cycles, the microcracks in the battery cathode material increase significantly. The electrode resistance increases, and the positive electrode begins to release a large amount of oxygen into the cell.
This phenomenon directly leads to the rapid attenuation of the capacity of high-nickel ternary lithium batteries and the increase of safety hazards. In recent years, the spontaneous combustion accidents of electric vehicles that have appeared continuously are mostly related to the safety hazards of power batteries.
Whether it is improving the shape of the battery pack or adjusting the battery management system, it is only a drop in the bucket to alleviate this situation. At such a node, the power battery industry begins to explore more promising power battery solutions based on materials.
NCMA quaternary lithium battery is a technical solution born in this process. Its stable physical and chemical structure can support the future high-nickel route of power batteries.
At the same time, the mixing of relatively cheap aluminum elements greatly reduces the content of expensive cobalt elements in the positive electrode of power batteries, which is also very effective in reducing the cost of power batteries.
Whether it is the technical route or the market level, the future prospects of NCMA quaternary lithium batteries are very broad. It can be considered that quaternary lithium batteries are the most revolutionary battery technology before the birth of all-solid-state batteries, and a new wave of power battery technology will start from this. In this wave, GM and LG, which were the first to come up with finished quaternary lithium batteries, are undoubtedly one step ahead.
2. Korean battery experts prove the three major advantages of NCMA batteries
Currently, Un-Hyuck Kim, a lithium battery expert at Hanyang University in South Korea, has passed experiments to prove that NCMA quaternary lithium batteries have high performance Excellent performance on the nickel technology route.
On April 2, 2019, the Un-Hyuck Kim team published a paper titled "Quaternary Layered Nickel-rich NCMA Cathode for Li-ion Batteries" in the Journal of the American Chemical Society (ACS) .
The paper compares nickel from five aspects: capacity decline, H2-H3 irreversible phase transition voltage change, positive electrode particle microcracks, oxygen release when lithium ions are deintercalated, and thermal stability. Performance of NCM, NCA, NCMA cathode materials with a content of about 90%.
1. The capacity decline of NCMA quaternary lithium batteries is not obvious
In order to prevent errors in the experiment, the Un-Hyuck Kim team conducted a control test on 2032 sets of batteries.
▲Battery capacity fading comparison experimental data
Under the experimental conditions of 30 degrees Celsius and 0.1C, these batteries were placed at a voltage between 2.7V-4.3V for the initial cycle Charge and discharge test.
Among them, the NCM90 battery with a nickel content of 90 has an initial discharge capacity of 229mAh/g, and the NCA89 and NCMA89 batteries with a nickel content of 89 have an initial discharge capacity of 225mAh/g and 228mAh/g respectively.
It can be found that the initial discharge capacities of the three high-nickel batteries are very close, but after 100 charge and discharge cycles, the discharge capacity of the NCMA89 battery dropped to the original 90.6, while the discharge capacities of NCM90 and NCA89 Then they dropped to the original 87.7 and 83.7 respectively.
Under the same temperature and voltage, increase the discharge rate to 0.5C, and then test the same (new) battery pack.
After 100 cycles, the discharge capacities of NCMA89, NCM90, and NCA89 dropped to 87.1%, 82.3%, and 73.3% of the original values ??respectively.
To be closer to the actual situation, the Un-Hyuck Kim team placed the battery in an environment of 25 degrees Celsius, 1C, 3.0V-4.2V and conducted another 1,000 charge and discharge experiments.
The result this time is that the NCMA89 battery maintained its initial capacity of 84.5, while the capacities of the NCM90 battery and NCA89 battery dropped to 68.0% and 60.2% of the initial capacity respectively.
It can be seen that the stability of NCMA quaternary lithium batteries on the high-nickel route is far better than that of NCM and NCA ternary lithium batteries. The closer it is to actual usage, the more obvious this advantage becomes.
2. The structure of NCMA quaternary lithium battery is more stable
The attenuation of battery capacity is in the cathode material, which is mainly reflected in the irreversible phase change of H2-H3 and the micro-cracks in the cathode material .
▲The irreversible phase change of H2-H3 in three batteries
The so-called irreversible phase change of H2-H3 is mainly used to reflect the changes in the cathode lattice and the insertion and detachment of lithium ions. Reversibility of the intercalation process (redox peak).
The process of H1-H2 is usually reversible, but once the H3 phase appears in the electrode, an irreversible change occurs, and the ability of lithium ions to intercalate and deintercalate will be lost. When the voltage exceeds a certain value , or when the discharge rate reaches a certain rate, the H3 phase will appear.
Therefore, the consideration of battery performance will be reflected in the change of voltage value and the change of redox peak when H3 irreversible phase transition occurs.
By conducting 100 charge and discharge cycle tests on NCMA89, NCA89, and NCM90 batteries, the Un-Hyuck Kim team found that only NCMA89’s H2-H3 irreversible phase transition voltage remained almost at the initial level. state, the voltage of the H2-H3 irreversible phase transition of NCM90 and NCA89 batteries both declined to varying degrees, and the redox peak decreased.
That is to say, in multiple cycles, batteries with NCA and NCM cathode materials are more likely to have H3 phase, and the reversibility will decline.
As for the microcracks in the cathode material, the properties of different materials are also different, but the occurrence of microcracks will affect the impedance of the electrode. Once the impedance increases, it will affect the current charging and discharging of the battery.
▲The micro-cracks of the three types of battery cathode materials. The upper and lower rows of pictures from left to right are NCA89 batteries, NCM90 batteries, and NCMA89 batteries?
As mentioned in the above description , NCMA89 electrode is less likely to undergo the irreversible phase transition of H2-H3, and it has strong mechanical stability. Experiments by the Un-Hyuck Kim team also proved this. After multiple charge and discharge cycles, the microcracks in the cathode material of the NCMA89 battery were significantly less than those of the NCM90 and NCA89 batteries.
In addition, the oxygen released during the deintercalation process of lithium ions will also dissolve transition metals, causing the structure of the cathode material to be unstable.
The Un-Hyuck Kim team calculated the oxygen vacancy energies of NCMA89, NCM90 and NCA89 batteries through density functional theory (DFT) and found that the oxygen vacancy energies of the three batteries were 0.80eV and 0.72eV respectively. and 0.87eV.
It can be seen from this value that the NCA89 battery with stable Al-O chemical bonds is least likely to release oxygen, the NCMA89 battery is also relatively stable, and the NCM90 battery requires the least energy to release oxygen, and is the most It is easy to cause changes in the structure of the cathode material.
3. NCMA cathode material has stronger thermal stability
Considering that the thermal stability of electrode materials is also extremely important for battery safety, the Un-Hyuck Kim team also uses poor Display scanning calorimetry (DSC) was used to measure the peak temperature of the exothermic reaction of the cathode material.
The measurement results show that the peak temperature of the exothermic reaction of the positive electrode of the NCA89 battery is 202°C and the calorific value is 1753J/g, while the peak temperature of the NCM90 battery positive electrode is 200°C? and the calorific value is 1561J. /g. In comparison, the peak temperature of the positive electrode exothermic reaction of the NCMA89 battery is 205°C, while the heat generation is only 1384J/g. The thermal stability of the NCMA quaternary lithium battery is significantly better than the other two types of batteries.
Comprehensive testing of five aspects including capacity decline after multiple charge and discharge cycles, irreversible phase change of H2-H3, micro-cracks in the cathode material, oxygen release during lithium ion deintercalation, and thermal stability , the Un-Hyuck Kim team finally proved the excellent performance of NCMA cathode materials on the high-nickel route.
3. Is the short-term mass production cost of NCMA cathode material higher? But the long-term cost is better
But the current NCMA quaternary lithium battery is not completely without shortcomings. First of all, NCMA quaternary The preparation process of the cathode material, the core of lithium batteries, is more complicated than that of NCM and NCA batteries.
The Un-Hyuck Kim team published a paper on Materialstoday in March 2019, "High-energy nickel-rich cathode with redesigned composition and structure for use in next-generation lithium batteries."
▲A paper released by the Un-Hyuck Kim team
The paper mentioned that the preparation steps of NCMA cathode materials can be roughly divided into six stages:
1. Use nickel sulfate solution and cobalt sulfate solution to prepare spherical NC-NCM[Ni?0.893?Co?0.054?Mn?0.053?](OH)2 precursor through ***precipitation method, which is used to prepare [Ni?0.98? Co?0.02?](OH)2 starting material and added to the batch reactor.
2. Under an inert gas (nitrogen) environment, continuously add a specific amount of deionized water, sodium hydroxide solution, and ammonium hydroxide solution into the batch reactor, and at the same time, add a quantitative amount of sodium hydroxide The solution is pumped into the reactor with a sufficient amount of ammonium hydroxide solution (chelating agent).
3. During the synthesis process, the initially formed [Ni0.98Co0.02](OH)2 particles gradually become spherical.
4. In order to construct the NC-NCM structure, introduce quantitative nickel sulfate solution, cobalt sulfate solution and manganese sulfate solution (Ni:Co:Mn=80:9:11, molar ratio) into the reactor. [Ni?0.80?Co?0.09?Mn?0.11](OH)2 was prepared. By adjusting the amount of raw materials, [Ni?0.893?Co?0.054?Mn?0.053?](OH)2 powder was finally obtained.
5. Filter the powder, wash it, and dry it under vacuum at 110 degrees Celsius for 12 hours.
6. In order to prepare Li?[Ni?0.886?Co?0.049?Mn?0.050?Al?0.015?]?O?2, the precursor ([Ni?0.893?Co?0.054?Mn ?0.053?](OH)2) was mixed with LiOH·H?2?O and Al(OH)3?·3H2O and calcined in pure oxygen at 730 degrees Celsius for 10 hours.
If you are preparing NCM cathode materials, you can omit the step of adding aluminum in step 6; and if you are preparing NCA cathode materials, you can omit step 4.
Therefore, the production process of NCMA cathode materials is more complicated than that of NCM and NCA cathode materials, and its short-term production costs will inevitably be higher.
At the same time, the amount of aluminum also needs to be strictly controlled. Using too much or too little material will affect the energy density of the battery and attenuate the stability. The introduction of this process will undoubtedly bring challenges to the production process. more stringent requirements.
But from a long-term perspective, the introduction of aluminum reduces the use of cobalt. Taking the Ultium battery jointly produced by LG Chem and General Motors as an example, the content of cobalt in the battery has been reduced by 70%.
This situation can reduce the production cost of power batteries. It is understood that the average import price of cobalt hydrometallurgy intermediate products in July 2019 was US$19,707/ton (approximately RMB 137,000/ton) , and the price of high-quality bauxite is about 1,200 yuan/ton.
The complexity of the production process may temporarily delay NCMA batteries from occupying the market, but the long-term benefits will still drive power battery manufacturers and car companies to use NCMA quaternary lithium batteries.
4. Will NCMA batteries be mass-produced in 2021? Material manufacturers, battery factories, and vehicle manufacturers have made arrangements
At present, although NCMA is still in the early stages of industrialization, there are already Many companies have entered this field to make plans. From the perspective of company attributes, they can be divided into three types of players: lithium battery material suppliers, power battery companies, and vehicle manufacturers.
1. Lithium battery material suppliers
According to public information, lithium battery material supply giants Cosmo? T and GEM have taken the lead in laying out their plans in this field.
Cosmo? AM&T is the main supplier of LG Chem NCMA quaternary lithium battery cathode materials. The company said that it is currently studying NCMA high-nickel cathode materials, in which the nickel content reaches 92 and the cathode energy density is 228mAh/g.
The company is expected to achieve mass production of quaternary cathode materials in 2021. After mass production, it will first verify with LG Chem. However, the company has also reached cooperation with Samsung SDI in terms of cathode materials. Therefore, it is also likely to supply NCMA cathode materials to Samsung SDI.
When answering questions from investors, GEM also revealed recently that the company has completed the research and development and mass production of quaternary cathode materials and is in the process of ton-level certification with customers.
In addition, Qichacha shows that the Chinese branch of Linnaeus New Energy, an American new energy materials start-up company, applied for a patent for quaternary cathode materials and made it public on February 5, 2019. Announcement.
2. Power battery companies
The power battery companies currently deploying NCMA quaternary lithium batteries are mainly Chinese and Korean battery companies.
Among Chinese power battery companies, Guoxuan Hi-Tech and Honeycomb Energy took the lead in the layout of quaternary lithium batteries.
Hive Energy released the NCMA quaternary lithium battery product at a press conference in July 2019. It is understood that the product was launched within the Hive in March 2018 and went through 16 months of research and development. Available.
▲Honeycomb Energy Press Conference
However, at present, Honeycomb Energy does not have the mass production capacity of quaternary lithium batteries. Yang Hongxin, general manager of Honeycomb Energy, said that the company will launch the first batch of quaternary lithium batteries in 2019. In the fourth quarter, the production capacity layout of NCMA quaternary cathode materials was completed, with an initial production capacity of 100 tons per year. By 2021, Honeycomb Energy will officially mass-produce NCMA quaternary lithium batteries.
Guoxuan Hi-Tech is not so high-profile. Qichacha information shows that in 2016, Guoxuan Hi-Tech applied for two patents for the preparation method of quaternary lithium batteries. The two patents were issued in 2018 and 2019 respectively. Obtain invention authorization.
However, Guoxuan Hi-Tech’s technical route is relatively niche. It has applied for patents for the preparation of NCAT (nickel cobalt aluminum titanium) and NCMT (nickel cobalt magnesium titanium) cathode materials.
CATL has not announced that it will conduct research and development of NCMA batteries for the time being, but considering that GEM is one of its suppliers of cathode materials, it is also possible that CATL is secretly conducting research and development of NCMA batteries.
Among Korean battery companies, LG Chem is the first to announce that it will mass-produce NCMA quaternary lithium batteries and apply them to the Ultium battery pack in cooperation with General Motors. Lg Chemical stated that the energy density of this battery will reach 200mAh/g (it did not disclose whether it is the energy density of the battery cell).
3. OEMs
Currently, the only OEM that has made it clear that it will use NCMA quaternary lithium batteries is General Motors. The company’s “EV?week” opened on March 4 " announced a project to cooperate with LG Chem to develop batteries, and the core of the project is NCMA batteries and Ultium battery pack technology.
It is understood that GM will use this battery in its latest electric vehicle platform to provide 50kWh-200kWh battery packs for different models. The cost of the battery pack will drop to US$100/kWh ( Approximately 693 yuan/kWh).
▲GM’s new electric vehicle platform
If the plan goes well, GM will launch 20 electric vehicles in the next three years and reach sales of 1 million electric vehicles in 2025.
Once GM achieves a successful electrification transformation with the help of NCMA batteries, major car companies will also rush to follow suit, and the number of car companies deploying NCMA quaternary lithium batteries will increase significantly.
The entry of lithium battery material manufacturers, power battery companies, and vehicle manufacturers means that the NCMA quaternary lithium battery solution is likely to become one of the alternatives for future power batteries.
If it is successfully commercialized on a large scale, this product will have an impact on upstream mining, midstream power battery companies, and downstream vehicle manufacturers.
For upstream mining, the demand for cobalt mines has dropped significantly, and cobalt prices, which were once at a high level, are likely to decline sharply.
For power battery companies, a new round of technology iterations will bring benefits to leading power battery companies. The companies that deploy first will be able to seize the first batch of markets, while the companies that deploy later will be able to seize the first batch of markets. You may face falling behind or being eliminated.
For OEMs, the cost of NCMA quaternary lithium batteries has been significantly reduced due to the reduced use of cobalt, and the cost pressure on automakers to produce electric vehicles has dropped. Moreover, NCMA batteries have better cycle life and stability, and the reliability of electric vehicle products will be improved.
Conclusion: Is the era of quaternary batteries coming?
The quaternary lithium battery jointly developed by GM and LG is likely to set off a revolution in the power battery industry. Compared with NCM/NCA ternary lithium battery products, the quaternary lithium battery has a longer cycle life and is safer. Excellent performance and lower cost. For car companies and battery manufacturers, these advantages mean that quaternary lithium batteries are an option that is difficult to refuse.
However, until large-scale mass production, the fate of quaternary lithium batteries cannot be determined. There are many subsequent development routes for ternary lithium batteries, and new technologies have emerged in terms of production processes, materials, etc. change.
From the perspective of materials alone, lithium nickel manganese oxide "cobalt-free" batteries, lithium-sulfur batteries, and lithium-air batteries are all potential competitors for quaternary lithium batteries. Compared with the current ternary batteries, these battery products Lithium batteries also have considerable performance advantages.
It can only be said that quaternary lithium batteries are an alternative to ternary lithium batteries that are currently relatively close to mass production, and we still need to wait and see what happens next.
This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.