What Is The Difference Between LFP And Ternary Battery?-xmacey.com

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What Is The Difference Between LFP And Ternary Battery?

October 15 , 2024

What is the difference between LFP and ternary battery?

With the rapid development of the new energy market, lithium batteries, as its core power source, are becoming increasingly diverse in types. Among them, lithium iron phosphate and ternary lithium are currently the two most widely circulated batteries in the battery market. Below, we will focus on introducing these two types of batteries and understand their differences.

Lithium Iron Phosphate Materials and Batteries

The cathode material of lithium iron phosphate batteries is lithium iron phosphate(LiFePO4), which has an olivine type structure. This material is inexpensive, environmentally friendly, non-toxic, and highly safe. However, its relatively low electronic conductivity can affect the charging and discharging performance of the battery. The charging and discharging process of LiFePO4 material mainly involves the transition between LiFePO4 and FePO4 phases, with a small volume change rate, making the material extremely stable. Therefore, the safety and stability of lithium iron phosphate materials and batteries are beyond doubt.

Model diagram of lithium iron phosphate material

Figure 1-Model diagram of lithium iron phosphate material

Lithium iron phosphate batteries mainly have the following characteristics:

(1) The cycle performance of lithium iron phosphate batteries is excellent, the cycle life of energy batteries can be as long as 3000 to 4000 times, and the cycles of rate batteries can even reach tens of thousands of times;
(2) The lithium iron phosphate battery has excellent safety performance, and can maintain a relatively stable structure even at high temperatures, making the lithium iron phosphate battery safe and reliable, and even when the battery is deformed and damaged, there will be no smoke, fire, etc. ACCIDENT.

On the other hand, lithium iron phosphate raw material resources are relatively abundant, which greatly reduces the cost of materials and batteries. At the same time, because iron and phosphorus elements are environmentally friendly, lithium iron phosphate materials and batteries do not pollute the environment. However, the structural properties of LiFePO4 material determine that the material has low ionic and electronic conductivity, and as the temperature decreases, both the electron transfer resistance and the charge transfer resistance increase rapidly, resulting in poor low-temperature battery performance.

Ternary materials and batteries

Ternary lithium-ion battery(NCM) refers to a lithium-ion battery that uses three transition metal oxides of nickel, cobalt and manganese as positive electrode materials. Because it combines the advantages of lithium cobalt oxide, lithium nickel oxide and lithium manganese oxide, its performance is better than any single component positive electrode material above. Experimental analysis shows that three elements with different valences form a superlattice structure, and there is an obvious synergistic effect between the three components, making the material more stable, and the discharge platform is as high as 3.7V/3.8V, so it is considered to be one of the most promising positive electrode materials. Ternary batteries have excellent electrochemical properties such as high energy density, good safety and stability, support for high-rate discharge, and moderate cost advantages. They have been widely used in small and medium-sized lithium-ion battery fields such as consumer digital electronic products, industrial equipment, and medical instruments, and have shown strong development potential in power lithium-ion battery fields such as intelligent robots, AGV logistics vehicles, drones and new energy vehicles.

Ternary lithium is mainly divided into these types according to the element ratio of the positive electrode material: NCM111, NCM622, NCM811, NCM523, etc.

Figure 2-Phase diagram of the ternary system between LNO, LCO and LMO

Comparative analysis of two materials and batteries

Energy density

Compared with lithium iron phosphate materials, ternary materials have higher discharge specific capacity and higher average voltage, so the mass specific energy of ternary batteries is generally higher than that of lithium iron phosphate. In addition, due to the low true density, small particle size and carbon coating of the lithium iron phosphate material, the compacted density of the pole piece is about 2.3-2.4 g/cm3, while the compacted density of the ternary pole piece can reach 3.3 ~3.5 g/cm3, so the volume specific energy of ternary materials and batteries is also much higher than that of lithium iron phosphate.

Security

From the point of view of safety, the main structure of the lithium iron phosphate material is PO4, and its bond energy is much higher than the M-O bond energy of the ternary material MO6 octahedron. The thermal decomposition temperature of the fully charged lithium iron phosphate material is about 700 ℃. The thermal decomposition temperature of the corresponding ternary material is 200-300 °C, so the lithium iron phosphate material is safer. From a battery perspective, lithium iron phosphate batteries can pass all safety tests, while ternary batteries cannot easily pass tests such as acupuncture and overcharge, and need to be improved from structural parts and battery design.

Power performance

The activation energy of Li+ of the lithium iron phosphate material is only 0.3-0.5 eV, resulting in a Li+ diffusion coefficient of the order of 10-15-10-12 cm2/s. The extremely low electronic conductivity and lithium-ion diffusion coefficient lead to poor LFP power performance. The Li+ diffusion coefficient of the ternary material is about 10-12 ~ 10-10 cm2/s, and the electronic conductivity is high, so the ternary battery has better power performance.

Temperature suitability

Affected by the low electronic conductivity and ionic conductivity of the lithium iron phosphate material, the low temperature performance of the lithium iron phosphate battery is poor. Compared with normal temperature, the capacity retention rate of lithium iron phosphate battery discharge at -20 ℃ is only about 60%, while the ternary battery of the same system can reach more than 70%.

Cost and Environmental Factors

Ternary materials contain rare metals such as Ni and Co, and their cost is higher than that of lithium iron phosphate. With the improvement of materials and battery technology, the cost of ternary and lithium iron phosphate batteries has dropped significantly. At present, the market price of ternary batteries is higher than that of lithium iron phosphate batteries. At the same time, compared with the environmentally friendly Fe and P elements, the Ni and Co elements in the ternary materials and batteries are more polluting to the environment. Combined with the above factors, the demand for environmental control and waste recycling of ternary materials and batteries is more urgent.

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