Abstract:

In order to explore the influence of the N/P ratio on the performance of lithium iron phosphate batteries, four kinds of N/P ratios of lithium-ion batteries were fabricated by using lithium iron phosphate as the cathode material and artificial graphite as the anode material. The effects of the first discharge efficiency; charge and discharge performance at different current intensities; charge and discharge DCR; discharge capacity at high and low temperatures; and cycle performance at 45 ℃ using different N/P ratios were studied by electrochemical technology. The results show that the charge DCRs of lithium-ion batteries at 1.10 and 1.14 are about 4 MΩ smaller than those of N/P ratios (1.02 and 1.06) at 60% and 30% SOC, making them less polarized under high current intensities and low temperature conditions. With the increase of N/P, the charging constant current ratio and capacity retention rate at 0 ℃ are improved. The capacity retention rate is still 91.8% after 1000 cycles at 45 ℃ when N/P is 1.10, which is significantly higher than other groups (N/P ratios at 1.02 and 1.06). This research could provide a theoretical basis for future investigation of the design and use of lithium iron phosphate batteries.

Key words: lithium iron phosphate batteries, N/P ratio, charge and discharge at different current density, DCR, cycle performance