Overview of lithium iron phosphate battery

Lithium iron phosphate batteries are lithium ion batteries that use lithium iron phosphate as the cathode material. Lithium iron phosphate battery has the advantages of high safety, long cycle life, multiplier discharge, high temperature resistance, etc. It is considered as a new generation of lithium battery.

1、Lithium iron phosphate battery features

 Good safety performance, puncture does not explode, overcharge does not burn or explode;

 good cycle life, lithium iron phosphate battery cycle life up to 2000 times or more;

 good high temperature performance, operating temperature range -20℃ to 70℃;

 high vibration density, higher capacity under the same conditions;

 can realize 1C-5C fast charging capability, greatly reducing charging time.

2、Application fields

Power storage, special equipment, robotics, AGV, rail transportation, medical equipment, emergency backup, power communication, etc.

Advantages of lithium iron phosphate battery

1、Good safety performance

Safety comes from the stability of the cathode material and reliable safety design, lithium iron phosphate battery pack has been rigorous safety testing, even in violent collisions will not produce an explosion.

2, long cycle life

Lithium iron phosphate battery 1C cycle life is generally up to 2,000 times, or even more than 3,500 times, and for the energy storage market requires more than 4,000-5,000 times, higher than other types of lithium batteries.

3, high temperature performance

Lithium iron phosphate battery thermal peak up to 350 ~ 500 ℃, a wide range of operating temperatures (-20 ~ +75 ℃), high temperature (60 ℃) can still put out 100% capacity.

4、Fast charging

Using a special charger, 1.5C charging can make the battery full in 40 minutes.

5、Green

Lithium iron phosphate battery is green, non-toxic, non-polluting, with a wide range of raw materials and cheap.

Lithium iron phosphate battery voltage and capacity

1, lithium iron phosphate battery voltage

The nominal voltage of single lithium iron phosphate battery is 3.2V, charging voltage is 3.6V, and discharge cut-off voltage is 2.0V.

Lithium iron phosphate battery pack through the series combination of cells to achieve the required voltage of the equipment, battery pack voltage = N * number of series connection. Commonly used lithium iron phosphate battery pack voltages are as follows:

12V lithium iron phosphate battery

24V lithium iron phosphate battery

36V lithium iron phosphate battery

48V lithium iron phosphate battery

2, lithium iron phosphate battery capacity

The capacity of lithium iron phosphate battery pack is based on the capacity and number of cells connected in parallel, generally based on the specific requirements of the power equipment to determine, the more lithium iron phosphate cells connected in parallel, the greater the capacity.

Common lithium iron phosphate battery pack capacity of 10ah, 20ah, 40ah, 50ah, 100ah, 200ah, 400ah and so on.

Lithium iron phosphate battery structure and working principle

1, lithium iron phosphate battery structure

As shown in the figure, the left is the olivine structure of LiFePO4 as the positive electrode of the battery, connected with the positive electrode of the battery by the aluminum foil, in the middle of the polymer diaphragm, which separates the positive electrode from the negative electrode, but the lithium ions Li + can pass through the electrons can not be passed, the right is the negative electrode of the battery composed of carbon (graphite), connected with the negative electrode of the battery by the copper foil.

2, lithium iron phosphate battery working principle

LiFePO4 battery in charging, the positive electrode in the lithium ion Li + polymer diaphragm to the negative electrode migration; in the discharge process, the negative electrode in the lithium ion Li + through the diaphragm to the positive electrode migration. Lithium-ion batteries are named for the back and forth migration of lithium ions during charging and discharging.

Lithium iron phosphate battery charger

1.LiFePO4 Battery Charging

It is recommended to use CCCV charging method for charging LiFePO4 battery, i.e. first constant current and then constant voltage. Constant current is recommended to be 0.3 C. Constant voltage is recommended to be 3.65.

2, lithium iron phosphate battery and lithium ion battery charger the same?

Both battery charging method is first constant current and then constant voltage (CCCV), but the constant voltage point is not the same.

The nominal voltage of lithium iron phosphate battery is 3.2V, charging cut-off voltage 3.6V.

Nominal voltage of ordinary lithium batteries is 3.6V, charging cut-off voltage 4.2V.

3, with solar energy to lithium iron phosphate battery charging

Solar panels can not be directly to the lithium iron phosphate battery charging, because the voltage of the solar panel is unstable, can not be directly to the lithium iron phosphate battery charging, the need for voltage regulator circuit, but also to support the corresponding lithium iron phosphate battery charging circuit to charge.

4, with a generator to lithium iron phosphate battery charging

Generator can not be directly to the lithium iron phosphate battery charging, because the generator sends out electricity for the alternating current or pulse DC, lithium iron phosphate battery charging must be regulated DC.

Lithium iron phosphate battery cycle life and the factors that affect it

1, lithium iron phosphate battery used at room temperature environment

 small current charge and discharge

In this field of application on the lithium iron phosphate battery normal use, basically more than 2000 times the cycle life; small lithium battery manufacturers, the quality of a little less than a little more than 1000 times the cycle life;

 high rate of stable charge and discharge applications

The application of high rate discharge, most of the power lithium batteries, most of them are applied to provide power to the motor application. As most of the lithium iron phosphate batteries are operated under high load condition, which accelerates the decay time of the battery material, the cycle life is also around 800 times.

 high rate unstable charge/discharge use

Lithium iron phosphate battery used in this case, the life will be even shorter, only about 300 times.

2, lithium iron phosphate batteries used in high temperature environment

Lithium iron phosphate battery high temperature performance is not very mature, the operating temperature -20 ℃ to 125 ℃, the temperature range for the theoretical value, the actual application of the temperature range is smaller.

 small current charge and discharge

In this field of application on the lithium iron phosphate battery normal use, if the battery brand manufacturers are relatively strong, good quality, basically more than 1,000 times the cycle life; small lithium battery manufacturers, the quality of a little less than 500 times the cycle life; because of the use of high temperature, the battery damage is relatively large.

 high rate of stable charging and discharging use

As most of the lithium iron phosphate batteries run under high load conditions, accelerating the decay time of the battery material, cycle life is a sharp decline, the poor quality of the battery cell, may also be about 300 times the cycle; strength of the battery brand manufacturers, in the application of equipment technology and materials will be better, the quality of the battery cell will be better, but the cycle life of about 500 times.

 high multiplicity unstable charging and discharging use

High temperature plus discharge rate unstable operation, more damage to the battery, the cycle life is relatively low, several battery manufacturers electric core test found that 250 to 300 times so, the battery basically can not be used.

3, lithium iron phosphate batteries used in low-temperature environment

Low-temperature environment on the performance of lithium iron phosphate batteries than high but also large, the current market situation, lithium iron phosphate batteries below -20 ° C to -40 ° C work, the life expectancy decreased significantly, the cycle life of about 300 times.

4, lithium iron phosphate battery cycle life influencing factors

 charging and discharging

When choosing a charger, it is best to use a charger with the correct termination charging device cut off, so as not to shorten the service life of lithium iron phosphate batteries due to overcharging. Generally speaking, slow charging is better than fast charging to extend the service life of the battery.

 Depth of discharge

The depth of discharge is the main factor affecting the life of LiFePO4 battery, the higher the depth of discharge, the shorter the life of LiFePO4 battery. In other words, as long as the depth of discharge is reduced, the service life of lithium iron phosphate batteries can be significantly extended. Therefore, we should avoid over-discharging the Li-ion UPS battery to a very low voltage.

 Working Environment

If the lithium iron phosphate battery is used under high temperature for a long time, it will make its electrode activity decay and shorten its service life, so it is a good way to prolong the service life of lithium iron phosphate battery to keep it in the suitable operating temperature as much as possible.

Recycling of lithium iron phosphate batteries

Retired lithium iron phosphate batteries do not have the value of stepwise utilization of the battery and stepwise utilization of the battery will eventually enter the dismantling and recycling stage. Lithium iron phosphate batteries and ternary material batteries are different, does not contain heavy metals, recycling is mainly Li, P, Fe, recycling products with low added value, the need to develop low-cost recycling route. There are mainly two kinds of recovery methods: pyro and wet method.

 Fire Recovery Process

The traditional pyro recovery is generally high temperature incineration of electrode pieces, the carbon and organic matter in the electrode fragments will be burned off, and the remaining ash that can not be burned off will eventually be screened to get the fine powdery materials containing metals and metal oxides.

 Wet Recovery Process

Wet recovery is mainly through the acid and alkali solution to dissolve the metal ions in lithium iron phosphate batteries, and further use of precipitation, adsorption and other ways to extract the dissolved metal ions in the form of oxides, salts and other forms of extraction, most of the reaction process using H2SO4, NaOH and H2O2 and other reagents.