Analysis on the performance difference between lithium iron phosphate and ternary lithium ion batteries
This article uses the same battery case cover, anode material and internal structure design to make lithium iron phosphate and ternary cathode materials respectively, and compare the specific energy, specific power, cycle, high and low temperature characteristics of the two batteries, etc. Performance, compare and analyze the performance differences between the two batteries.
1 experiment
1.1 Experimental material selection
Anode material A ternary material with a ratio of lithium iron phosphate and nickel-cobalt-manganese of 1:1:1. The negative electrode is MCMB, the electrolyte is a mixed solvent composed of EC, PC, EMC and DEC, the electrolyte is LiPF6 as the lithium salt, and the diaphragm is a single layer. PP25μm.
1.2 Preparation of porous membrane electrode and composite membrane electrode
Using square aluminum shell LP2770102 battery shell, cover and interior With the same multi-pole winding structure, two batteries with lithium iron phosphate and ternary material as the positive electrode material are respectively manufactured according to the battery manufacturing process. The average capacity, internal resistance, and mass of the lithium iron phosphate battery are 7.2Ah, 1.06m, and 361g, respectively; the average battery of ternary material is 8.6Ah, 1.12m, and 360g.
1.3 Analysis and testing
The test conditions are: the charge and discharge voltage control range of the ternary material battery is 2.5~4.2V , 1Cu003d7.5A, the charging and discharging voltage control range of lithium iron phosphate battery is 2.0~3.65V, 1Cu003d6.5Ah, and the test temperature is (252)℃ without special instructions.
2 Results and discussion
2.1 Discharge performance test
From Figure 1 and Table 1, it can be concluded that the use of ternary materials for the positive electrode of the battery with the same volume is 19.4% higher than the lithium iron phosphate material, the specific energy is 37.5% higher, and the discharge specific power is 39.7% higher. Since the specific capacity and compaction density of ternary materials are higher than those of lithium iron phosphate materials, the use of ternary materials for battery discharge has greater advantages.
2.2 Comparison of charging performance
It can be seen from Figure 2 and Table 2 that the ternary material battery and the lithium iron phosphate material battery When charging under 10C, there is no significant difference in the ratio of constant current charging capacity/total capacity. When charging at a rate above 10C, the ratio of constant current charging capacity/total capacity of lithium iron phosphate batteries is smaller. The greater the charging rate, the constant current charging capacity. The difference between the total capacity ratio and the ternary material battery is more obvious. This is mainly related to the small voltage change of lithium iron phosphate at 30% to 80% SOC. For example, the negative electrode uses soft carbon or hard carbon, and the lithium iron phosphate battery is charged at a high rate. Performance can reach the level of a ternary battery.
In Figure 3, the remaining capacity of the ternary material battery is 66% after 3900 cycles, and the remaining capacity of the lithium iron phosphate battery is 84% u200bu200bafter 5000 cycles. The cycle life is longer than that of the ternary material battery. Lithium iron phosphate batteries have obvious advantages. According to the remaining capacity/initial capacityu003d80% as the end point of the test, the current 1C cycle life of the ternary material battery laboratory is about 2500 times, and the 1C cycle life of the lithium iron phosphate battery laboratory is more than 3500 times, and some have reached more than 5000 times.
2.4 Discharge test at different temperatures
The discharge comparison of batteries at different temperatures is shown in Figure 4. When discharged at 55℃, there is no difference in discharge capacity between ternary material battery and lithium iron phosphate at room temperature. When discharged at -20℃, the ratio of discharge capacity/normal temperature capacity of ternary material battery is higher than that of lithium iron phosphate battery. 15%, as shown in Table 3.
3 Conclusion
In this paper, by making a battery with the same structure, it is concluded that ternary materials and lithium iron phosphate materials are used in HEV Advantages and disadvantages of battery applications, ternary materials have advantages in battery specific energy, specific power, high rate charging, low temperature performance, etc. In terms of cycle performance, lithium iron phosphate materials have obvious advantages, and lithium iron phosphate batteries are also superior in terms of safety. Ternary materials. When choosing a battery, you can choose according to different purposes. For example, the space of a bus is relatively large, and the specific energy and specific power requirements of the battery are relatively low. Lithium iron phosphate battery can be selected to give full play to its good cycle performance. The space of the car is limited. If the amount is small, it is more appropriate to choose a ternary battery with high specific energy and high specific power.
