SMM May 21: at the "2021 China International Nickel-Cobalt-Lithium Summit Forum" sponsored by SMM Information & Technology Co., Ltd., Li Jigang, general manager of Tianjin Skoland Technology Co., Ltd., expounded the current development and application status of lithium ferromanganese phosphate materials.
Summary of Lithium Manganese Iron Phosphate Materials
The theoretical capacity of lithium ferromanganese phosphate is the same as that of lithium iron phosphate, which is 170mAhpog, but its electrode potential relative to Li+/Li is 4.1V, which is much higher than 3.4V of lithium iron phosphate, and it is located in the stable electrochemical window of organic electrolyte system. The high potential of 4.1V makes lithium ferromanganese phosphate have the advantage of potential high energy density, which is its biggest advantage over lithium iron phosphate.
It is worth mentioning that when the actual capacity of lithium ferromanganese phosphate is the same as that of lithium iron phosphate, its energy density is 15% higher than that of lithium iron phosphate, and compared with lithium manganate with the same voltage, its mass energy density can also be increased by more than 25%. In addition, lithium ferromanganese phosphate has the advantages of low cost, environment-friendly and broad market prospect.
In order to solve the problem of electrical conductivity of lithium ferromanganese phosphate, the company prepared lithium ferromanganese phosphate material with high electrochemical activity by coating carbon and combining phase iron doping and lithium site doping. On the one hand, carbon coating inhibits the growth of particles and reduces the diffusion distance of lithium ions, on the other hand, carbon has excellent conductivity, which is conducive to electron transport and improve the electronic conductivity of materials. Manganese phase doping iron plasma can improve the electrical conductivity of lithium manganese phosphate materials, thus obtaining higher reversible capacity, charge-discharge efficiency and cycle performance. The doping of high valence metal ions at lithium site improves the diffusion channel of lithium ions and increases the diffusion rate of lithium ions in the process of charge and discharge.
Physical properties of lithium ferromanganese phosphate:
The finished product of lithium ferromanganese phosphate is irregular spherical, most of which have a particle size of 100-200nm, and the carbon coating of lithium ferromanganese phosphate is uniform with a thickness of 3-5nm.
Electrochemical performance:
Through button battery test and high temperature cycle test at 55 ℃, it is found that the specific capacity of lithium ferromanganese phosphate is 154.8 mAh Discharge g, which is similar to that of lithium iron phosphate, and lithium ferromanganese phosphate has excellent high temperature performance. In addition, lithium ferromanganese phosphate has excellent thermal stability, and the safety performance of NCM can be improved when compounded with NCM.
Specific application
When LMFP is used alone, the compaction density of the material can reach 2.3g / cm ~ 2.5g / cm ~ 3. The specific capacity of 0.2C Discharge can reach more than 140mAh/g, and the median voltage of 0.2C Discharge can reach 3.75V. The material has higher energy density than lithium iron phosphate and better safety performance than ternary material.
Take the full battery capacity test as an example:
The 14500 test of the whole battery showed that the specific capacity of 0.2C Discharge was 142.3 mAh/g,0.5C Discharge specific capacity 140.4 mAh/g,0.5C Discharge specific capacity 1C Discharge specific capacity 137.8mAhCPG, and the electrochemical performance was similar to that of lithium iron phosphate.
LMFP composite 20% ternary 523 material, the compaction density can reach 2.5-2.8g pico cm30.2C Discharge specific capacity can reach 150mAh / g, after compounding a small amount of ternary material Discharge curve can be turned into a smooth curve, the pressure drop slope of the two platforms can be reduced, the impact on electrical appliances can be reduced, and the existing ternary battery management system can be used, so that lithium ferromanganese phosphate can be used in large quantities.
The compaction density of the whole battery test is 2.5-2.8 g Discharge cm3.The specific capacity of 0.2C Discharge is 150.3 mAh / cm, the specific capacity of 0.5C Discharge is 147.4 mAh / cm, the specific capacity of 1C Discharge is 144.7 mAh / g, and the composite material has higher energy density after 20% ternary 523.
LMFP composite 80% ternary 523 material, the compaction density can reach 3.2-3.4g, the specific capacity of 0.2C Discharge can be up to 166mAhmax g, which has little effect on the energy density of the ternary material, but the addition of a small amount of LMFP to the ternary material not only improves the safety performance of the ternary material, but also reduces the overall cost of the ternary battery system.
Full battery performance test:
The compaction density of the whole battery test was 3.33g hand cm3.0.2C Discharge specific capacity was 166.8mAhpencer 0.5C Discharge specific capacity 160.6mahqqqqq1C Discharge specific capacity 156.3mahpg. The ternary material composite with a small amount of lithium ferromanganese phosphate still has a very high energy density.
It is worth mentioning that the needle test of ternary and lithium ferromanganese phosphate composite battery shows that it does not burn, does not explode and the temperature is below 70 ℃, and the safety is good; while the ternary and lithium ferromanganese phosphate composite battery is overcharged, does not burn, does not explode, and the highest temperature is below 150 ℃, the safety is good.
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