List of manufacturers of lithium iron phosphate batteries, brand characteristics of lithium iron phosphate batteries

Overview of LiFePO4 battery

LiFePO4 battery is a kind of lithium-ion battery which uses LiFePO4 as cathode material. LiFePO4 battery is considered as a new generation of lithium battery because of its high safety, long cycle life, high rate discharge and high temperature resistance. Juda lithium can provide customized battery solutions with integrated cell, BMS (power management system) and structure to meet customers' personalized power demand.

1. Characteristics of LiFePO4 battery

Good safety performance, no explosion when puncturing, no combustion and no explosion when overcharging;

The cycle life of LiFePO4 battery is more than 2000 times;

High temperature performance, working temperature range - 20 ℃ to 70 ℃;

It has higher tap density and higher capacity under the same conditions;

It can realize 1c-5c fast charging ability and greatly shorten the charging time.

2. Application fields

Power energy storage, special equipment, robot, AGV, rail transit, medical equipment, emergency backup, power communication, etc.

Advantages of LiFePO4 battery

1. Good safety performance

The safety comes from the stability of cathode materials and reliable safety design. The LiFePO4 battery pack has undergone strict safety test, and will not explode even in severe collision.

2. Long cycle life

The 1C cycle life of LiFePO4 battery is generally up to 2000 times, even more than 3500 times, and the energy storage market requires more than 4000-5000 times, which is higher than other types of lithium batteries.

3. High temperature performance

The thermal peak value of LiFePO4 battery can reach 350 ~ 500 ℃, the working temperature range is wide (- 20 ~ + 75 ℃), and it can still release 100% capacity at high temperature (60 ℃).

4. Fast charging

Using a special charger, the battery can be fully charged after charging at 1.5C for 40 minutes.

5. Green environmental protection

LiFePO4 battery is environmental friendly, nontoxic and pollution-free, with a wide range of raw materials and low price.

Voltage and capacity of LiFePO4 battery

1. Lithium iron phosphate battery voltage

The nominal voltage, charging voltage and discharge cut-off voltage of single LiFePO4 battery are 3.2V, 3.6V and 2.0V respectively. The lithium iron phosphate battery pack achieves the required voltage of the equipment through the series combination of the cells. The battery pack voltage = n * series number. The commonly used LiFePO4 battery pack voltages are as follows:

12V lithium iron phosphate battery

24 V LiFePO4 battery

36V LiFePO4 battery

48V lithium iron phosphate battery

2. Lithium iron phosphate battery capacity

The capacity of lithium iron phosphate battery pack is determined according to the capacity and number of cells in parallel, generally according to the specific requirements of electrical equipment. The more lithium iron phosphate cells in parallel, the greater the capacity. Common LiFePO4 batteries have capacity of 10Ah, 20Ah, 40ah, 50ah, 100Ah, 200ah, 400ah, etc.

Structure and working principle of LiFePO4 battery

1. Structure of LiFePO4 battery

As shown in the figure, on the left is the olivine structure LiFePO4 as the positive electrode of the battery, which is connected by aluminum foil and the positive electrode of the battery, and in the middle is a polymer diaphragm, which separates the positive electrode from the negative electrode, but Li + can pass through, but e - can't. on the right is the negative electrode of the battery composed of carbon (graphite), which is connected by copper foil and the negative electrode of the battery.

Internal structure of LiFePO4 battery

2. Working principle of LiFePO4 battery

When LiFePO4 battery is charged, Li + in the positive electrode migrates to the negative electrode through the polymer diaphragm; during discharge, Li + in the negative electrode migrates to the positive electrode through the diaphragm. Lithium ion battery is named because lithium ion migrates back and forth during charging and discharging.

Lithium iron phosphate battery charger

1.LiFePO4 Battery Charging

CCCV charging mode is recommended for lithium iron phosphate battery pack, that is, constant current first and then constant voltage. Constant current 0.3C is recommended. Constant pressure is recommended to be 3.65.

2. Is LiFePO4 battery the same as Li ion battery charger

The charging methods of the two batteries are constant current and constant voltage (CCCV), but the constant voltage point is different.

The nominal voltage of LiFePO4 battery is 3.2V and the cut-off voltage is 3.6V.

The nominal voltage of ordinary lithium battery is 3.6V, and the cut-off voltage of charging is 4.2V.

3. Charging LiFePO4 battery with solar energy

Solar panels can't charge LiFePO4 battery directly, because the voltage of solar panels is unstable and can't charge LiFePO4 battery directly. It needs voltage stabilizing circuit and corresponding LiFePO4 battery charging circuit to charge.

4. Charging LiFePO4 battery with generator

The generator can not charge the LiFePO4 battery directly, because the electricity generated by the generator is AC or pulsed DC, and the LiFePO4 battery must be charged with regulated DC.

Comparison of LiFePO4 battery and Li ion battery

System voltage (V) energy density (WH / kg) working temperature (℃) cycle life safety environmental performance cost based on cycle life x wh of SLA

LiFePO4 < 3.2 > 120 - 20-60 > 2000 < 0.15-0.25 lower than SLA

Lead acid > 2.0 > 35 - 20-40 > 200 ﹣ not good ﹣ 1

NiCd < 1.2 > 40 - 20-50 > 1000 > safety < 0.7

NIMH ﹥ 1.2 > 80 - 20-50 > 500 ﹥ safety ﹥ 1.2-1.4

Limnxniycoz02 ﹥ 3.7 > 160 - 20-50 > 500 ﹥ better than LiCo ﹥ 1.5-2.0

LiCoO2 > 3.7 > 200 - 20-50 > 500 > unsafe w / O > 1.5-2.0

Lithium iron phosphate battery and lithium ternary battery

Affected by the structure, LiFePO4 and ASP have their own advantages and disadvantages in performance, ASP has advantages in energy density and fast charging speed, LiFePO4 has advantages in cycle life, safety and economy.

1. Material comparison

The negative electrode, electrolyte and separator of the two batteries are similar, and the biggest difference is the cathode material, which is named after it.

Cathode materials: lithium iron phosphate nickel cobalt manganese

Short for LFP NCM

The rated voltage is ＜ 3.2V ＞ 3.65v

Crystalline olivine structure and layered structure

One dimensional and two dimensional lithium ion deintercalation channels

2. Energy density

From the cell level, the energy density of ternary battery is higher. The rated voltage and theoretical specific capacity (MAH / g) of LiFePO4 cathode material are lower than those of ternary battery, and its energy density has been developed to the "ceiling".

Theoretical specific capacity (MAH / g) of cathode material at rated voltage (V) estimation actual specific capacity (MAH / g) estimation response cell energy density (WH / kg)

LiFePO4 ~ 3.2 ~ 170 ~ 145 ~ 170

Ternary ncm811 ~ 3.65 ~ 274 ~ 195 ~ 240

Ternary ncm523 ~ 170 ~ 210

Ternary ncm111 ~ 145 ~ 180 note: the energy density of the cell should be comprehensively evaluated in combination with the cell design and process, and the value in the table is only for reference.

3. Charging efficiency

Compared with LiFePO4 battery, ternary lithium battery has great advantages in charging efficiency. There is no significant difference in the constant current ratio between the ternary lithium battery and the lithium iron phosphate battery when the charge rate is below 10C. When the charge rate is above 10C, the constant current ratio of the lithium iron phosphate battery decreases rapidly, and the charging efficiency decreases rapidly.

4. Cycle life

Theoretically, LiFePO4 has advantages in life span. Its olivine crystal structure is more stable, the expansion is lower, and the electrochemical reaction is more stable.

5. Security

LiFePO4 battery has incomparable advantages in safety. The results show that the cathode voltage is low and there is no oxygen releasing thermal chain reaction similar to ternary cell. The thermal stability temperature can reach above 300 ℃, while the temperature of ternary cell is about 150-200 ℃.

6. Economy

In terms of price, LiFePO4 has obvious advantages, raw materials are relatively cheap, and domestic industrial chain is relatively mature. Cobalt is the key to reduce the price of ternary NCM battery. Cobalt is mainly associated ore with low output and uneven distribution, and its price has been rising continuously in recent years.

Cycle life and influencing factors of LiFePO4 battery

1. LiFePO4 battery used at room temperature

Low current charge and discharge

In this field, if LiFePO4 battery is used normally, it has a cycle life of more than 2000 times; small lithium battery manufacturers, whose quality is a little lower, also have a cycle life of more than 1000 times;

High rate stable charge and discharge

Most of the applications of high rate discharge are power lithium batteries, most of which are used to provide power for motors. Because most of the LiFePO4 batteries operate under high load, the decay time of the battery material is accelerated, and the cycle life is about 800 times.

High rate unstable charge and discharge

In this case, the life of LiFePO4 battery will be shorter, only about 300 times.

2. LiFePO4 battery used in high temperature environment

At present, the high temperature performance of LiFePO4 battery is not very mature. The operating temperature range is from - 20 ℃ to 125 ℃, which is the theoretical value. The practical application temperature range is smaller.

Low current charge and discharge

In this field, if the lithium iron phosphate battery is used normally, if the battery brand manufacturers are relatively strong and of good quality, they basically have a cycle life of more than 1000 times; if the small lithium battery manufacturers are slightly inferior in quality, they also have a cycle life of more than 500 times; because they are used at high temperature, the damage to the battery is relatively large.

High rate stable charge and discharge

As most LiFePO4 batteries operate under high load, the decay time of battery materials is accelerated, and the cycle life is sharply reduced. The poor quality battery cell may have about 300 cycles. The strong battery brand manufacturers will have better equipment technology and material application, and the quality of battery cell will be better, but the cycle life is about 500 cycles.

High rate unstable charge and discharge

The unstable operation of high-temperature plus discharge rate will cause more damage to the battery, and the cycle life is relatively low. The test on the household electrical appliance core of several battery factories shows that the battery can't be used after 250 to 300 times.

3. LiFePO4 battery used at low temperature

Low temperature environment has a greater impact on the performance of LiFePO4 battery than high temperature environment. According to the current market situation, LiFePO4 battery working below - 20 ℃ to - 40 ℃ has a significantly reduced life and a cycle life of about 300 times.

4. Influencing factors of LiFePO4 battery cycle life

When selecting the charger for charging and discharging, it is better to use the charger with the correct cut-off device to avoid overcharging and shortening the service life of lithium iron phosphate battery. Generally speaking, slow charging can extend the service life of battery more than fast charging. The higher the discharge depth, the shorter the life of LiFePO4 battery. In other words, as long as the discharge depth is reduced, the service life of lithium iron phosphate battery can be greatly extended. Therefore, we should avoid over discharging the lithium battery ups to a very low voltage. If LiFePO4 battery is used at high temperature for a long time in working environment, its electrode activity will decline and its service life will be shortened. Therefore, it is a good way to prolong the service life of LiFePO4 battery to keep the operating temperature as appropriate as possible.

Recovery of LiFePO4 battery

The batteries that do not have the value of echelon utilization and the batteries after echelon utilization will eventually enter the stage of dismantling and recycling. The difference between LiFePO4 battery and ternary material battery is that it does not contain heavy metals, and the main recovery products are Li, P and Fe. The added value of the recovery products is low, so it is necessary to develop a low-cost recovery route. There are mainly two kinds of recovery methods: fire method and wet method. Pyro recovery process the traditional pyro recovery process is to burn the electrode pieces at high temperature to burn off the carbon and organic matter in the electrode pieces. The residual ash that can not be burned off is finally screened to obtain fine powder materials containing metal and metal oxides. The wet recovery process is mainly to dissolve the metal ions in lithium iron phosphate battery by acid-base solution, and further extract the dissolved metal ions in the form of oxides and salts by precipitation, adsorption and other means. In the reaction process, most of the reagents such as H2SO4, NaOH and H2O2 are used.