Seven advantages and five disadvantages of lithium iron phosphate batteries

The Full name of lithium iron phosphate battery is lithium iron phosphate lithium-ion batteries. The name was too long, so we can call it as lithium iron phosphate batteries. Because its performance is particularly suitable for power applications, its name includes "power" two words, namely lithium iron phosphate power battery. Some people called it "lithium iron (LiFe) power battery".

The working principle of

Lithium iron phosphate batteries, refers to the use of lithium iron phosphate as the anode material of lithium ion batteries. Lithium ion battery anode materials mainly have cobalt acid lithium, lithium manganese acid lithium, nickel, ternary material, lithium iron phosphate, etc. The cobalt acid lithium is at present most of the lithium ion battery cathode material.

meaning

Metals trading market, cobalt (Co) is the most expensive, and the storage capacity is not much, nickel (Ni), manganese (Mn) cheaper, and more iron (Fe) storage. The price of the anode materials is consistent with the prices of these metals market. Therefore, the use of LiFePO4 cathode material of lithium ion batteries should be quite cheap. Another feature of it is environmental protection free from contamination to the environment.

As the requirements of the rechargeable batteries are: high capacity, high output voltage, good charge and discharge cycle performance, stable output voltage, large current charge and discharge, electrochemical stability, use of safety (did not charge, discharge and short circuit caused by improper operation, such as the combustion or explosion), wide working temperature range, non-toxic or less poison, no pollution to the environment. Adopting LiFePO4 as anode of lithium iron phosphate batteries are good on these performance requirements, particularly in large discharge rate discharge (5 ~ 10 c discharge), stable discharge voltage, security, not burning, not an explosion, and life (cycles), on the environment pollution-free, it is the best, is currently the best large current output power battery.

The structure and working principle

LiFePO4 as the positive pole of the battery, connected to the battery positive electrode by aluminum foil and polymer is among the diaphragm, which separates the positive and negative, but lithium ion Li and electronic e - cannot pass, right is composed of carbon (graphite) battery cathode, the copper foil and negative connection of the battery. Between the top and bottom side is the battery electrolyte battery, the battery by the metal casing airtight packaging.

When charge LiFePO4 battery, the anode of lithium ion Li by polymer membrane to the cathode migration; In the process of discharge, the cathode of lithium ion Li through the diaphragm to the positive transfer. Lithium ion battery is due to the lithium ion migration and named after the back and forth during charging and discharging.

The main performance

LiFePO4 battery's nominal voltage is 3.2 V, termination of charging voltage is 3.6 V, termination voltage is 2.0V. Because of the various manufacturers adopt positive and negative electrode materials and electrolyte material quality and process is different, its performance will be some difference. For example the same models (the same kind of packaging standard cell), the battery capacity has a bigger difference (10% ~ 20%).

Here to explain that different factory production of iron phosphate lithium power battery in various performance parameters will have some difference; In addition, there are some battery performance was not included in, such as battery internal resistance, self-discharge rate, temperature of the charge and discharge, etc.

Lithium iron phosphate power battery capacity has a bigger difference, can be divided into three categories: small zero a few to several mAh, medium of dozens of mAh, large hundreds of mAh. The same parameters of different types of batteries also have some differences.

Over discharge to zero voltage test:

Using STL18650 (1100 mAh) lithium iron phosphate power battery discharge to zero voltage test. Test conditions: 0.5 C charge rate will be filled with 1100 mAh STL18650 batteries, and then use 1.0 C discharge rate discharge to the battery voltage is 0 C. Then to 0V battery is divided into two groups: a group for seven days, another group of 30 days; Deposit matures with 0.5 C charge rate is full, and then use 1.0 C discharge. Finally comparing two zero voltage storage period the difference between different.

Test result, zero voltage battery for seven days without leakage, good performance, the capacity is 100%;For 30 days, no leakage, the performance good, capacity is 98%;For 30 days after the battery to do 3 times charge and discharge cycle, capacity and up to 100%.

This test shows that the lithium iron phosphate battery discharge even seen (or even to 0 v), and deposit a certain time, battery leakage, damage. This is other kinds of lithium ion battery has no features.

1, the improvement of safety performance

Lithium iron phosphate crystals in P - solid O key, difficult to decompose, even in high temperature or overcharge when also won't like cobalt acid lithium structure collapse fever or strong oxidizing substances, thus having good security. A report pointed out that the practice of acupuncture or short circuit experiment found combustion phenomenon in a small number of samples, but no one explosion occurred, and overcharge experiments using several times greatly beyond their discharge voltage of high voltage charging, found that there are explosive. Even so, the overcharge safety than common liquid electrolyte cobalt acid lithium batteries, has been greatly improved.

2, the improvement of the life

lithium iron phosphate battery refers to the use of lithium iron phosphate as the anode material of lithium ion battery.

Long life cycle life of lead-acid battery in around 300, the highest is 500 times, and lithium iron phosphate power battery, cycle life reached more than 2000 times, the standard charging rate (5 hours) to use, can reach 2000 times. With the quality of the lead-acid battery is "new half a year, half a year, maintenance, maintenance and half year old", at most 1-1.5 years, while the lithium iron phosphate batteries used under the same conditions, the theory of life will reach 7 ~ 8 years. Comprehensive consideration, the price performance ratio in theory for lead-acid battery more than four times. Large current discharge can be as big 2 C fast charge and discharge current, under the special charger, 1.5 C can make battery charging 40 minutes, starting current can be up to 2 C, lead-acid battery is the performance.

The page contains the contents of the machine translation.