Advantages and Disadvantages of Lithium Iron Phosphate Batteries

Advantages and Disadvantages of Lithium Iron Phosphate Batteries

I. Overview of Lithium Iron Phosphate Batteries
Lithium iron phosphate batteries belong to the category of lithium-ion secondary batteries. One of their main applications is as power batteries, which have significant advantages over NI-MH and Ni-Cd batteries. The charge-discharge efficiency of lithium iron phosphate batteries is relatively high, ranging from 85% to 90%, while that of lead-acid batteries is only about 80%.

 

II. Details of the Advantages and Disadvantages of Lithium Iron Phosphate Batteries

 

(A) Seven Advantages

 

  1. Improved Safety Performance
    The P-O bonds in the lithium iron phosphate crystal are very stable and not easy to break down. Even under high temperatures or overcharging conditions, it will not experience structural collapse, heat generation, or the formation of strongly oxidizing substances like lithium cobaltate, thus possessing good safety. According to relevant reports, in actual needle puncture or short-circuit experiments, only a small number of samples showed combustion phenomena, and no explosion incidents occurred. However, in overcharging experiments, when charged with a high voltage several times higher than its own discharge voltage, explosion situations still occurred. Even so, its overcharging safety has been greatly improved compared to ordinary liquid electrolyte lithium cobaltate batteries.
  2. Extended Lifespan
    The cycle life of long-life lead-acid batteries is about 300 times, with a maximum of 500 times. In contrast, the cycle life of lithium iron phosphate power batteries can reach more than 2000 times. When using standard charging (at a 5-hour rate), it can reach 2000 cycles. Lead-acid batteries of the same mass are usually "new for half a year, old for half a year, and maintained for another half a year", and can be used for a maximum of 1 - 1.5 years. Under the same conditions, the theoretical lifespan of lithium iron phosphate batteries can reach 7 - 8 years. Overall, the theoretical performance-to-price ratio is more than four times that of lead-acid batteries. In addition, it can also perform high-current discharge and achieve 2C rapid charge-discharge. With a dedicated charger, the battery can be fully charged within 40 minutes at a 1.5C charging rate, and the starting current can reach 2C, which is a performance that lead-acid batteries do not have.
  3. Excellent High-Temperature Performance
    The thermal peak value of lithium iron phosphate can reach 350°C - 500°C, while that of lithium manganate and lithium cobaltate is only about 200°C. Its working temperature range is wide, from -20°C to 75°C, and it has high-temperature resistance characteristics. The thermal peak value of lithium iron phosphate can reach 350°C - 500°C, while that of lithium manganate and lithium cobaltate is only about 200°C.
  4. Large Capacity
    It has a larger capacity compared to ordinary batteries (such as lead-acid batteries), with a single-cell capacity range of 5AH - 1000AH.
  5. No Memory Effect
    When rechargeable batteries are frequently used in a state of being fully charged but not fully discharged, their capacity will quickly drop below the rated capacity value. This phenomenon is called the memory effect. Nickel-metal hydride and nickel-cadmium batteries have memory effects, while lithium iron phosphate batteries do not have this problem. Regardless of the state of the battery, it can be charged and used at any time without the need to be fully discharged first.
  6. Light Weight
    The volume of a lithium iron phosphate battery with the same specification and capacity is two-thirds of that of a lead-acid battery, and its weight is only one-third of that of a lead-acid battery.
  7. Environmental Protection Characteristics
    This type of battery is generally considered to contain no heavy metals or rare metals (nickel-metal hydride batteries require rare metals). It has passed the SGS certification, is non-toxic and pollution-free, and complies with the European RoHS regulations. It is an absolute green and environmentally friendly battery. For this reason, lithium batteries are favored by the industry, mainly due to environmental considerations.

 

(B) Disadvantages

 

  1. During the sintering process of lithium iron phosphate preparation, there is a possibility that iron oxide may be reduced to elemental iron under a high-temperature reducing atmosphere. Elemental iron will cause micro-short circuits in the battery, which is a highly undesirable substance in battery manufacturing.
  2. Lithium iron phosphate has some performance defects. For example, its tap density and compacted density are relatively low, resulting in a relatively low energy density of lithium-ion batteries. Its low-temperature performance is poor, and even after being nano-sized and carbon-coated, this problem has not been solved.
  3. The preparation cost of materials and the manufacturing cost of batteries are relatively high, the yield of finished batteries is low, and the consistency is poor. Although the nano-sizing and carbon-coating of lithium iron phosphate have improved the electrochemical performance of the materials, they have also brought about other problems, such as a reduction in energy density, an increase in synthesis cost, poor electrode processing performance, and strict environmental requirements. Although the chemical elements Li, Fe, and P in lithium iron phosphate are abundant and have relatively low costs, the cost of the prepared lithium iron phosphate products is not low. Even without considering the previous research and development costs, the process cost of this material plus the relatively high cost of manufacturing batteries will result in a relatively high cost per unit of stored electrical energy.
  4. Poor Product Consistency
    From the perspective of material preparation, the synthesis reaction of lithium iron phosphate is a complex multiphase reaction involving solid-phase phosphates, iron oxides, and lithium salts, plus carbon precursors and reducing gas phases. In such a complex reaction process, it is difficult to ensure the consistency of the reaction.

 

III. Advantages and Disadvantages of Lithium Iron Phosphate Batteries Compared with Ternary Batteries
Compared with ternary batteries, lithium iron phosphate batteries have only one disadvantage: insufficient energy density.
(1) Low Cost: Since cobalt metal is not required, the cost of lithium iron phosphate batteries is much lower than that of ternary batteries. However, both costs have room for decline in the future.
(2) Excellent Safety Performance: Lithium iron phosphate batteries rarely experience explosion incidents and other situations, so they are widely used in buses with a large number of passengers.
(3) Rapid Technological Progress: By utilizing the safety redundancy of lithium iron phosphate to make up for the insufficient energy density, and making full use of its excessive safety characteristics to enlarge the battery volume, so as to make up for the insufficient energy density.

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