The difference in charge and discharge efficiency between lithium iron phosphate battery and ordinary lithium battery (such as lithium cobalt oxide, lithium manganese oxide, etc.) is due to the difference in electrode materials. The positive electrode material of lithium iron phosphate battery is lithium iron phosphate, which has a stable olivine structure. The embedding and extraction process of lithium ions in it is relatively stable, which reduces energy loss. Although the theoretical energy density of materials such as lithium cobalt oxide used in ordinary lithium batteries is high, the migration of lithium ions is more likely to cause side reactions during the charge and discharge process, consuming part of the electrical energy, resulting in a decrease in the overall charge and discharge efficiency. For example, under the same test conditions, the initial charge and discharge efficiency of lithium iron phosphate battery can reach 90% - 95%, while some ordinary lithium batteries may only be 85% - 90%.
During the charging process, the polarization phenomenon of lithium iron phosphate battery is relatively weak. Polarization refers to the phenomenon that the electrode potential deviates from the equilibrium potential when the battery is charged and discharged. The higher the degree of polarization, the greater the energy loss. Due to the material characteristics, lithium iron phosphate battery can effectively suppress polarization, making the efficiency of converting electrical energy into chemical energy higher during charging. In the later stage of charging, especially when the ordinary lithium battery is close to full charge, polarization intensifies and more heat is generated. This heat is the embodiment of energy loss. During the discharge process, the lithium iron phosphate battery can also maintain a low voltage drop and output electrical energy stably, while the voltage of ordinary lithium batteries drops faster as the power is consumed, further affecting the discharge efficiency.
As the number of cycles increases, the charge and discharge efficiency of lithium iron phosphate batteries and ordinary lithium batteries will decrease, but there is a significant difference in the degree of decrease. With its stable chemical structure, the lithium iron phosphate battery can still maintain a charge and discharge efficiency of more than 80% after more than 2,000 cycles. Ordinary lithium batteries, especially those with lithium cobalt oxide as the positive electrode material, may drop to 70% - 75% after 500 - 1,000 cycles. This is because during the cycle of ordinary lithium batteries, the electrode material will gradually undergo structural changes, resulting in obstruction of the lithium ion migration channel, thereby reducing the charge and discharge efficiency, and the structural stability of the lithium iron phosphate battery effectively delays this process.
Temperature has a completely different effect on the charge and discharge efficiency of lithium iron phosphate batteries and ordinary lithium batteries. In low temperature environments, the viscosity of the electrolyte of ordinary lithium batteries increases, and the diffusion rate of lithium ions slows down, resulting in a significant decrease in charge and discharge efficiency, and even charging difficulties. However, by optimizing the electrolyte formula and electrode materials, the lithium iron phosphate battery can still maintain a certain charge and discharge efficiency at -20℃. Although it is lower than that at room temperature, the decrease is smaller than that of ordinary lithium batteries. In high temperature environments, ordinary lithium batteries are more likely to suffer from thermal runaway, resulting in reduced efficiency and safety hazards. The lithium iron phosphate battery can maintain a relatively stable charge and discharge efficiency at relatively high temperatures due to the high thermal stability of the material.
In fast charging scenarios, the efficiency difference between lithium iron phosphate batteries and ordinary lithium batteries is more significant. Due to the strong thermal stability and structural stability of lithium iron phosphate batteries, they can withstand large charging currents. During fast charging, the decrease in their charge and discharge efficiency is relatively small. For example, when a 60kW fast charging pile is used to charge a vehicle equipped with a lithium iron phosphate battery, the overall charge and discharge efficiency can still be maintained above 85% during the process of charging from 20% to 80%. When ordinary lithium batteries are charged at high currents, they are not only prone to polarization and severe heat generation, but also cause a significant decrease in charge and discharge efficiency, which will seriously affect the battery life in the long term.
In practical applications, the efficiency advantages of lithium iron phosphate batteries and ordinary lithium batteries have different focuses. In the field of energy storage with high requirements for safety and cycle life, lithium iron phosphate batteries can reduce the operating costs of energy storage systems and increase overall benefits with their high charge and discharge efficiency and long cycle life. In the field of 3C consumer electronics with extremely high requirements for energy density, although ordinary lithium batteries have slightly lower charge and discharge efficiency, their high energy density can meet the needs of miniaturization and thinness of equipment. However, with the continuous advancement of lithium iron phosphate battery technology, its application in some 3C products has gradually increased, showing its competitiveness in efficiency and comprehensive performance.
With the development of battery technology, both lithium iron phosphate battery and ordinary lithium battery have room for improvement in charge and discharge efficiency. For lithium iron phosphate battery, it is expected to further improve its charge and discharge efficiency and energy density by optimizing material preparation process and improving battery structure design. For example, nano-lithium iron phosphate materials and the use of new conductive agents can enhance the transmission speed of lithium ions and electrons and improve charge and discharge efficiency. Ordinary lithium batteries try to reduce polarization and energy loss by developing new electrode materials and optimizing electrolyte formula. In the future, the gap between the two in charge and discharge efficiency may narrow due to technological breakthroughs, but lithium iron phosphate battery will still maintain its leading position in balancing efficiency and safety with its own material advantages.
