Manganese-based batteries will usher in another peak

Manganese-based cathode materials are ushering in the second wave of peaks. The first time manganese-based batteries were promoted was when the Nissan Leaf was at its peak. As the second-generation product of manganese-based materials, lithium iron manganese phosphate has entered the early stage of mass production and has attracted much attention in the industry.

Companies such as CALB, Gotion Hi-Tech, and REPT have mentioned some progress in lithium iron manganese superphosphate batteries.

For example, from 2023 to 2024, REPT’s lithium iron manganese phosphate energy density will reach 500Wh/L, supporting 800 kilometers of battery life for pure electric models; CALB reduces lithium consumption by 15% through lithium manganese iron phosphate batteries. In addition to the above-mentioned companies, a number of power battery manufacturers such as CATL, BYD, and EVE Lithium Energy in top 10 power battery companies have begun to conduct related research and development and layout of lithium iron manganese phosphate batteries.

Among them, the lithium iron manganese phosphate of many companies has passed the battery pilot test in the first half of this year, and is sending samples to car companies for testing. CATL will mass-produce M3P batteries in the second half of the year. Another potential product, lithium-rich manganese-based batteries, is still in the research and development stage. At present, the laboratory stage of lithium-rich manganese-based materials achieves 400mAh/g, and mass production is also expected to reach 400mAh/g, and the battery energy density can reach 400Wh/kg.

Lithium iron manganese phosphate has obvious advantages and disadvantages

The application of manganese in lithium battery cathode materials is currently mainly based on lithium manganate and nickel cobalt lithium manganate (ternary material). With the advancement of material modification technology, manganese-based cathode materials lithium manganese iron phosphate and lithium-rich manganese-based technologies have developed rapidly.

Lithium iron manganese phosphate has become a transition product between lithium iron phosphate and ternary battery, which is characterized by higher energy density than lithium iron phosphate and lower cost than ternary lithium battery.

Lithium iron manganese phosphate has the same olivine structure as lithium iron phosphate, and the structure is more stable during charging and discharging. Even if all lithium ions are inserted during charging, the structure will not collapse, so it is safer. Specifically, it will be found that the advantages and disadvantages of lithium iron manganese phosphate are very obvious.

First, the energy density is better. The voltage platform of lithium iron manganese phosphate is as high as 4.1V, which is higher than that of lithium iron phosphate of 3.4V, high voltage brings an increase in energy density. The theoretical energy density is 15%-20% higher than that of lithium iron phosphate, which can basically reach the level of ternary battery NCM523.

Second, the low temperature performance is better. Lithium iron manganese phosphate has better low temperature performance than lithium iron phosphate, and the capacity retention rate can reach about 75% at -20 °C. Third, it has the characteristics of lithium iron phosphate battery, which is safer than ternary battery. Lithium iron manganese phosphate has an olivine structure, which has better safety and cycle stability than ternary.

Fourth, manganese ore resources are abundant and the cost is lower. The cost of lithium iron manganese phosphate is only about 5%-10% higher than that of lithium iron phosphate. Considering the increase in energy density of lithium iron manganese, in terms of battery installed cost, the cost per watt-hour of lithium iron manganese phosphate is slightly lower than that of lithium iron phosphate, and significantly lower than that of ternary batteries.

The disadvantage of lithium iron manganese phosphate battery is that its low conductivity and lithium ion diffusion speed will make it difficult to fully exert its capacity advantages and poor rate performance. However, in the opinion of relevant personnel of Guoxuan Hi-Tech, lithium iron manganese phosphate is basically an insulator. “Sony Corporation of Japan has calculated that the band gap of the general lithium iron phosphate material is about 0.3eV, which is a semiconductor, but the lithium iron manganese phosphate is 2eV, basically an insulator, it does not conduct electricity.”

Improvement scheme of lithium iron manganese phosphate material

Compared with lithium iron phosphate batteries, due to the addition of manganese, the dissolution of manganese will lead to a decrease in its cycle life. In view of the above reasons, when manganese is used as a single active material, doping, carbon coating, and nanotechnology modification are often used to improve the performance of lithium iron manganese phosphate materials.

If it is not nanosized, this conductive network cannot be formed. However, once it is nanosized, it is not easy to combine the paste, and the coating is not easy to apply. It is difficult to use it as a lithium manganese iron phosphate battery alone, and many problems need to be solved. ” The solution of China Innovation Aviation is to consider how to make the gradient design of manganese element. It is not necessarily uniform inside and outside. There may be a gradient design. It can be a little more outside and a little less inside, so that the entire conductive path is more smooth.

Second, it is doped with many other transition metal elements to make it achieve a better balance of energy and conductivity. Then, there are problems on the interface, and the coating is done on the interface, which on the one hand solves the conductive problem of the interface. On the other hand, it also effectively solves the problem of life attenuation caused by the phase change of the lithium manganese material itself.

One of the top 10 lithium marine battery manufacturers in China REPT also mentioned lithium iron manganese phosphate. Their goal is to achieve an energy density of 500Wh/L and a driving range of 800 kilometers for lithium iron manganese phosphate batteries in 2023-2024. In addition to the above companies, the M3P battery of CATL is also a lithium iron manganese phosphate battery, which is called the ternary of the phosphate system. CATL will invest in Lithitech in November 2021 with a stake of 60%. Among them, Lithitech’s main business is lithium iron manganese phosphate materials, and it has a production capacity of 2,000 tons per year.

The researcher of China Electronics Technology Group, the direction given for the application of lithium iron manganese phosphate is that it is hoped that it can be mixed with ternary materials to improve the safety of ternary material batteries; Or mixed with lithium iron phosphate to increase the energy density of lithium iron phosphate.

The past and future of manganese-based batteries

Lithium iron manganese phosphate, which is currently being hotly fried, is the second-generation manganese-based battery, which is a transitional product through material modification. The first generation of manganese-based batteries is the lithium manganate battery. Lithium manganate cathode material was invented as early as 20 years ago, and was once used in the first generation of new energy vehicles in Japan and South Korea.

Lithium manganate batteries in Japan and South Korea are mainly doped with single crystal particles. Among them, the master is the Japanese battery company AESC at that time. The early model Nissan Leaf was known for its battery safety. But the shortcomings are also obvious. Due to the low energy density, the driving range is only 200 kilometers. However, the current AESC is based on the ternary battery as the mainstream development direction.

Lithium iron manganese phosphate is not a new direction either. As early as 2013, BYD took lithium iron manganese phosphate as an upgrade route for lithium iron phosphate and began to apply for related patents. However, due to the subsidy policy tilting towards ternary materials with higher energy density, and BYD’s failure to solve the problems of low cycle life and excessive internal resistance of lithium manganese iron phosphate batteries,this route has not become mainstream, and BYD once stopped the exploration of lithium iron manganese phosphate.

However, since 2020, BYD has begun to have related patent application records. Guoxuan Hi-Tech is also an early company that developed lithium iron manganese phosphate batteries. According to Xu Xingwu, in 2013, Guoxuan Hi-Tech was also developing lithium iron manganese phosphate batteries, and obtained new product certificates for lithium iron manganese phosphate batteries in 2014 and 2017 respectively. as early as 2014, CALB started to try and explore on the road of high manganese.

In 2014, CALB had already used lithium iron manganese phosphate and ternary battery as a composite material system, which had been mass-produced. At that time, it was a station wagon, and there were actually a lot of shipments. Starting from 2021, the price of raw materials has skyrocketed. In the context, lithium iron manganese phosphate batteries have once again attracted the attention of enterprises, and there have been more reports on related layouts.

The next highly anticipated cathode material is lithium-rich manganese-based. Lithium-rich manganese-based materials have high specific capacity, low cost and better safety. The lithium-rich manganese-based cathode material can be considered to be composed of two components, Li2MnO3 and LiMO2, which are uniformly compounded at the atomic scale to form a lithium-rich manganese-based material.

Lithium-rich manganese-based materials are mainly based on cheaper manganese elements and contain less precious metals. Compared with the commonly used lithium cobalt oxide and nickel-cobalt-manganese ternary cathode materials, they are not only lower in cost, but also better in safety. The advantages are prominent, and there are also many disadvantages. Lithium-rich manganese-based materials have disadvantages such as initial irreversible capacity loss, poor rate performance, and voltage decay during cycling.

Regarding manganese-rich lithium-based materials, there are great advantages and great difficulties. It can achieve 400mAh/g, but there is a problem of voltage decay. There is no better way to lose oxygen during the cycle, and the challenge is still relatively large. Professionals believe that the lithium-rich manganese-based material battery can achieve a level of 300mAh/g after mass production, and it can achieve a battery of 400Wh/kg when matched with silicon carbon.

At present, it is seen that many companies are making arrangements in the field of lithium-rich manganese-based materials. According to relevant company announcements, Rongbai Technology, Dangsheng Technology and other cathode material companies have all laid out the research and development of lithium-rich manganese-based materials in advance.

At present, it has entered the small test stage, and actively cooperates with relevant customers to carry out product performance optimization and process scale-up experiments in the company’s existing production lines.

In addition, Zhenhua New Materials, Zhongwei, Kungong Technology, Tianyuan Group, DFD and other companies have also carried out research and development projects of lithium-rich manganese-based materials (precursors), and are currently actively exploring the feasibility of their commercialization.

Final thought

New manganese-based cathode materials are rapidly emerging, and the increase in their permeability is expected to increase the amount of manganese used in the lithium battery industry by more than 10 times between 2021 and 2035, and is expected to become one of the main cathode materials for power batteries.