Analyze the advantages and disadvantages of lithium iron phosphate batteries and their improvement

The full name of lithium iron phosphate battery is lithium iron phosphate lithium ion battery, this name is too long, referred to as lithium iron phosphate battery. Because its function is particularly suitable for power applications, the word "power" is added to the name, that is, lithium iron phosphate power battery. Some people call it a "lithium iron power battery."

Lithium iron phosphate battery refers to a lithium ion battery that uses lithium iron phosphate as a positive electrode material. There are many kinds of cathode materials for lithium-ion batteries, mainly lithium cobalt oxide, lithium manganate, lithium nickelate, ternary materials, lithium iron phosphate, etc. Among them, lithium cobalt oxide is currently the cathode material used in most lithium-ion batteries, while other cathode materials have not been widely consumed in the market due to various reasons. Lithium iron phosphate is also one of the lithium ion batteries. From the material principle, lithium iron phosphate is also an intercalation/deintercalation process, which is completely opposite to lithium cobaltate and lithium manganate.

Lithium iron phosphate batteries are lithium-ion secondary batteries. One of the main uses is as power batteries, which have great advantages over lead-acid batteries.

The charging and discharging efficiency of lithium iron phosphate batteries is relatively high, between 85% and 95%. The lead-acid battery is about 80%.

Advantage

1. Improvement of safety function

The P-O bond in lithium iron phosphate crystal fluctuates and is difficult to decompose. Even at high temperature or overcharge, it will not collapse and generate heat like lithium cobalt oxide or form a strong oxidizing substance, so it has good safety. A report pointed out that a small number of samples were found to be extinguished in the theoretical operation of the acupuncture or short circuit experiment, but no explosion occurred. In the overcharge experiment, high voltage charging that was several times higher than the self-discharge voltage was used, and it was found that there were still Explosion phenomenon. Nevertheless, its overcharge safety has been greatly improved compared with ordinary liquid electrolyte lithium cobalt oxide batteries.

2. Improvement of life span

Lithium iron phosphate battery refers to a lithium ion battery that uses lithium iron phosphate as a positive electrode material.

The cycle life of a short-lived lead-acid battery is about 300 times, and the highest is 500 times, while the cycle life of a lithium iron phosphate power battery reaches more than 2000 times, and the standard charge (5 hour rate) can reach 2000 times. Lead-acid batteries of the same quality are "new half a year, half a year old, and half a year for maintenance", which can take up to 1 to 1.5 years, while lithium iron phosphate batteries are used under abnormal conditions and their practical life will reach 7 to 8 years. Based on comprehensive thinking, the utility price is more than 3 times that of lead-acid batteries in practice. High-current discharge can quickly charge and discharge high-current 2C. Under a public charger, the battery can be overcharged within 40 minutes of 1.5C charging. The starting current can reach 2C, but lead-acid batteries have no such function.

3. Good high temperature function

The peak value of lithium iron phosphate electric heating can reach 350℃-500℃, while lithium manganate and lithium cobaltate are only around 200℃. The duty temperature range is wide (-20C-- 75C), with high temperature resistance, the peak value of lithium iron phosphate electric heating can reach 350℃-500℃, while lithium manganate and lithium cobaltate are only around 200℃.

4. Large capacity

Rechargeable batteries are often under the condition of being overcharged, and the capacity will quickly fall below the rated capacity. This phenomenon is called the memory effect. Like nickel-metal hydride and nickel-cadmium batteries, there is memory, but lithium iron phosphate batteries do not have this phenomenon. No matter what shape the battery is in, it can be charged and used as soon as it is charged.

5. Light weight

The volume of the lithium iron phosphate battery of the same specification and capacity is 2/3 of the volume of the lead-acid battery, and the weight is 1/3 of the lead-acid battery.

6. Environmental protection

Lithium iron phosphate batteries are generally considered to be free of any heavy metals and rare metals (the nickel-hydrogen battery requires rare metals), non-toxic (SGS certified), non-polluting, in line with European RoHS regulations, and an absolute green battery certificate. Therefore, the reason why lithium batteries are favored by the industry is mainly due to environmental considerations. Therefore, the battery has been included in the "863" national high-tech development plan during the "Tenth Five-Year Plan" period, and has become a key national support and encouragement project. With China's participation in the WTO, China's export of electric bicycles will rapidly increase, and electric bicycles entering Europe and the United States have been required to be equipped with pollution-free batteries.

However, some experts said that the environmental pollution caused by lead-acid batteries mainly occurred in the company's irregular consumption process and recycling and disposal links. In the same way, lithium batteries are a good part of the new power industry, but they cannot avoid the results of heavy metal pollution. In the processing of metal materials, lead, arsenic, cadmium, mercury, chromium, etc. can be released into dust and water. The battery itself is a kind of chemical substance, so two kinds of pollution may occur: one is the pollution of process excrement in the consumer engineering; the other is the pollution of the battery after it is scrapped.

Lithium iron phosphate batteries also have their drawbacks: for example, poor low-temperature performance, low tap density of the cathode material, and the volume of the lithium iron phosphate battery of equal capacity is larger than that of lithium-ion batteries such as lithium cobalt oxide, so it has no advantage in micro-batteries. When used in power batteries, lithium iron phosphate batteries are the same as other batteries.