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od **Winshinepower** » 19 dub 2022 07:16

Today, Winshinepower will bring you the relevant content of lithium iron phosphate batteries. It will answer your key questions about how to improve the low-temperature performance of lithium iron phosphate batteries, and will also explore the reasons for the performance degradation of lithium iron phosphate batteries at low temperatures. Next, we will Let's go see it together.

Advantages of lithium iron phosphate batteries
The cathode material is a key part of lithium-ion batteries and must meet the requirements of high capacity, strong stability and low toxicity.

Compared with other cathode materials (such as LiCoO2, LiNiO2 and LiMn2O4), LiFePO4 electrode material has many advantages, such as higher theoretical specific capacity (170mAh/g), stable working voltage (3.5V), stable structure, good cyclability, raw material Low cost and environment friendly etc.

Therefore, this material is an ideal positive electrode material and is selected as one of the main positive electrode materials for power batteries.

Reasons for the accelerated performance degradation of LIBs of lithium iron phosphate batteries at low temperature
Many researchers have studied the mechanism of the accelerated performance degradation of LIBs at low temperatures, and it is believed that the deposition of active lithium and its catalytically grown solid-state electrolyte interface (SEI) leads to the decrease of ionic conductivity and the decrease of electron mobility in the electrolyte. decline,

This decline leads to a reduction in the capacity and power of LIBs and sometimes even battery performance failures. The low-temperature working environment of LIBs mainly occurs in winter and high latitude and high altitude areas, where the low-temperature environment will affect the performance and life of LIBs, and even cause extremely serious safety problems.

Affected by the low temperature, the rate of lithium intercalation in graphite is reduced, and metal lithium is easily precipitated on the surface of the negative electrode to form lithium dendrites, which pierce the diaphragm and cause an internal short circuit in the battery. Therefore, methods to improve the low-temperature performance of LIBs are of great significance for promoting the use of electric vehicles in alpine regions.

Methods to improve low-temperature performance of lithium iron phosphate batteries
This paper summarizes the methods to improve the low-temperature performance of lithium iron phosphate batteries from the following three aspects

1) Pulse current generates heat;

2) Use electrolyte additives to prepare high-quality SEI films;

3) The interface conductivity of surface coating modified LiFePO4 material.

lithium iron phosphate battery

1. Rapid heating of low-temperature batteries by pulse current

During the charging process of Li-ion battery LIBs, the movement and polarization of ions in the electrolyte will promote the internal heat generation of Li-ion battery LIBs. This heat generation mechanism can be effectively used to improve the performance of Li-ion battery LIBs at low temperatures. Pulse current refers to a current whose direction does not change and whose current intensity or voltage changes periodically with time. To rapidly and safely raise the battery temperature at low temperatures, De Jongh et al. used a circuit model to theoretically simulate how a pulsed current heats up LIBs, and verified the simulation results through experimental testing of commercial LIBs. The difference in heat generation between continuous charging and pulsed charging is shown in Figure 1. Microsecond pulse times can promote more heat generation in lithium iron phosphate batteries.

The study shows the excitation effect of pulse current on LiFePO4/MCNB battery. It is found that after the excitation of pulse current, the surface temperature of the battery increases from -10℃ to 3℃, and compared with the traditional charging mode,

The entire charging time is reduced by 36 min (23.4%), and the capacity is increased by 7.1% at the same discharge rate. Therefore, this charging mode is beneficial for fast charging of low-temperature LiFePO4 batteries.

The effect of the pulse current heating method on the low-temperature battery life (state of health) of LiFePO4 power lithium-ion battery, including the effect of pulse current frequency, current intensity, and voltage range on battery temperature, the results show that higher current intensity, lower frequency and A wider voltage range enhances the heat accumulation and temperature rise of LIBs.

Furthermore, after 240 heating cycles (each cycle equal to 1800 s of pulsed heating at -20°C), they evaluated the state of health (SOH) of LIBs after pulsed current heating by studying the cell capacity retention and electrochemical impedance,

The surface morphology changes of the negative electrode of the battery were studied by SEM and EDS. The results show that the pulse current heating will not increase the deposition of lithium ions on the negative electrode surface, so the pulse heating will not exacerbate the risk of capacity decay and lithium dendrite growth caused by lithium deposition.

2. Electrolyte modification of SEI membrane to reduce the charge transfer resistance at the electrolyte-electrode interface

The low-temperature performance of lithium iron phosphate batteries is closely related to the ion mobility in the battery, and the SEI film on the surface of the electrode material is the key link affecting the lithium-ion mobility.

Liao et al. studied the effect of carbonate-based electrolyte (1 mol/L LiPF6/EC+DMC+DEC+EMC, with a volume ratio of 1:1:1:3) on the low-temperature performance of LiFePO4 commercial lithium iron phosphate batteries.

When the operating temperature is lower than -20 °C, the electrochemical performance of the battery decreases significantly. Electrochemical impedance spectroscopy (EIS) tests show that the increase in charge transfer resistance and the decrease in lithium-ion diffusion capacity are the main factors for the degradation of battery performance.

Therefore, it is expected to improve the low-temperature performance of LiFePO4 batteries by changing the electrolyte to enhance the reactivity of the electrolyte-electrode interface.

3. Surface coating conductive layer to reduce the surface resistance of LiFePO4 material

One of the important reasons for the degradation of lithium battery performance in low-temperature environment is the increase of impedance at the electrode interface and the decrease of ion diffusion rate. LiFePO4 surface coating conductive layer can effectively reduce the contact resistance between electrode materials, thereby improving the diffusion rate of ions in and out of LiFePO4 at low temperatures.

SEM and EIS analysis show that Sn coating improves the contact between LiFePO4 particles, and the material has lower charge transfer resistance and higher lithium diffusion rate at low temperature, therefore, Sn coating improves LiFePO4/C battery at low-temperature specific capacity, cycle performance and rate performance under

The electrochemical test results show that the AZO coating can also greatly improve the rate capability and low-temperature performance of LiFePO4, which is due to the conductive AZO coating increasing the electrical conductivity of the LiFePO4 material.

Through reading this article, three methods to improve the low-temperature performance of lithium iron phosphate batteries are introduced in detail. Specifically, the heat generation through pulsed current, the preparation of high-quality SEI film using electrolyte additives, and the improvement of the interfacial conductivity of LiFePO4 materials by surface coating.

For more information, please follow the link below: https://www.winshinepower.com/

od **Winshinepower** » 19 dub 2022 07:18

Today, Winshinepower will bring you the relevant content of lithium iron phosphate batteries. It will answer your key questions about how to improve the low-temperature performance of lithium iron phosphate batteries, and will also explore the reasons for the performance degradation of lithium iron phosphate batteries at low temperatures. Next, we will Let's go see it together.

Advantages of lithium iron phosphate batteries
The cathode material is a key part of lithium-ion batteries and must meet the requirements of high capacity, strong stability and low toxicity.

Compared with other cathode materials (such as LiCoO2, LiNiO2 and LiMn2O4), LiFePO4 electrode material has many advantages, such as higher theoretical specific capacity (170mAh/g), stable working voltage (3.5V), stable structure, good cyclability, raw material Low cost and environment friendly etc.

Therefore, this material is an ideal positive electrode material and is selected as one of the main positive electrode materials for power batteries.

Reasons for the accelerated performance degradation of LIBs of lithium iron phosphate batteries at low temperature
Many researchers have studied the mechanism of the accelerated performance degradation of LIBs at low temperatures, and it is believed that the deposition of active lithium and its catalytically grown solid-state electrolyte interface (SEI) leads to the decrease of ionic conductivity and the decrease of electron mobility in the electrolyte. decline,

This decline leads to a reduction in the capacity and power of LIBs and sometimes even battery performance failures. The low-temperature working environment of LIBs mainly occurs in winter and high latitude and high altitude areas, where the low-temperature environment will affect the performance and life of LIBs, and even cause extremely serious safety problems.

Affected by the low temperature, the rate of lithium intercalation in graphite is reduced, and metal lithium is easily precipitated on the surface of the negative electrode to form lithium dendrites, which pierce the diaphragm and cause an internal short circuit in the battery. Therefore, methods to improve the low-temperature performance of LIBs are of great significance for promoting the use of electric vehicles in alpine regions.

Methods to improve low-temperature performance of lithium iron phosphate batteries
This paper summarizes the methods to improve the low-temperature performance of lithium iron phosphate batteries from the following three aspects

1) Pulse current generates heat;

2) Use electrolyte additives to prepare high-quality SEI films;

3) The interface conductivity of surface coating modified LiFePO4 material.

lithium iron phosphate battery

1. Rapid heating of low-temperature batteries by pulse current

During the charging process of Li-ion battery LIBs, the movement and polarization of ions in the electrolyte will promote the internal heat generation of Li-ion battery LIBs. This heat generation mechanism can be effectively used to improve the performance of Li-ion battery LIBs at low temperatures. Pulse current refers to a current whose direction does not change and whose current intensity or voltage changes periodically with time. To rapidly and safely raise the battery temperature at low temperatures, De Jongh et al. used a circuit model to theoretically simulate how a pulsed current heats up LIBs, and verified the simulation results through experimental testing of commercial LIBs. The difference in heat generation between continuous charging and pulsed charging is shown in Figure 1. Microsecond pulse times can promote more heat generation in lithium iron phosphate batteries.

The study shows the excitation effect of pulse current on LiFePO4/MCNB battery. It is found that after the excitation of pulse current, the surface temperature of the battery increases from -10℃ to 3℃, and compared with the traditional charging mode,

The entire charging time is reduced by 36 min (23.4%), and the capacity is increased by 7.1% at the same discharge rate. Therefore, this charging mode is beneficial for fast charging of low-temperature LiFePO4 batteries.

The effect of the pulse current heating method on the low-temperature battery life (state of health) of LiFePO4 power lithium-ion battery, including the effect of pulse current frequency, current intensity, and voltage range on battery temperature, the results show that higher current intensity, lower frequency and A wider voltage range enhances the heat accumulation and temperature rise of LIBs.

Furthermore, after 240 heating cycles (each cycle equal to 1800 s of pulsed heating at -20°C), they evaluated the state of health (SOH) of LIBs after pulsed current heating by studying the cell capacity retention and electrochemical impedance,

The surface morphology changes of the negative electrode of the battery were studied by SEM and EDS. The results show that the pulse current heating will not increase the deposition of lithium ions on the negative electrode surface, so the pulse heating will not exacerbate the risk of capacity decay and lithium dendrite growth caused by lithium deposition.

2. Electrolyte modification of SEI membrane to reduce the charge transfer resistance at the electrolyte-electrode interface

The low-temperature performance of lithium iron phosphate batteries is closely related to the ion mobility in the battery, and the SEI film on the surface of the electrode material is the key link affecting the lithium-ion mobility.

Liao et al. studied the effect of carbonate-based electrolyte (1 mol/L LiPF6/EC+DMC+DEC+EMC, with a volume ratio of 1:1:1:3) on the low-temperature performance of LiFePO4 commercial lithium iron phosphate batteries.

When the operating temperature is lower than -20 °C, the electrochemical performance of the battery decreases significantly. Electrochemical impedance spectroscopy (EIS) tests show that the increase in charge transfer resistance and the decrease in lithium-ion diffusion capacity are the main factors for the degradation of battery performance.

Therefore, it is expected to improve the low-temperature performance of LiFePO4 batteries by changing the electrolyte to enhance the reactivity of the electrolyte-electrode interface.

3. Surface coating conductive layer to reduce the surface resistance of LiFePO4 material

One of the important reasons for the degradation of lithium battery performance in low-temperature environment is the increase of impedance at the electrode interface and the decrease of ion diffusion rate. LiFePO4 surface coating conductive layer can effectively reduce the contact resistance between electrode materials, thereby improving the diffusion rate of ions in and out of LiFePO4 at low temperatures.

SEM and EIS analysis show that Sn coating improves the contact between LiFePO4 particles, and the material has lower charge transfer resistance and higher lithium diffusion rate at low temperature, therefore, Sn coating improves LiFePO4/C battery at low-temperature specific capacity, cycle performance and rate performance under

The electrochemical test results show that the AZO coating can also greatly improve the rate capability and low-temperature performance of LiFePO4, which is due to the conductive AZO coating increasing the electrical conductivity of the LiFePO4 material.

Through reading this article, three methods to improve the low-temperature performance of lithium iron phosphate batteries are introduced in detail. Specifically, the heat generation through pulsed current, the preparation of high-quality SEI film using electrolyte additives, and the improvement of the interfacial conductivity of LiFePO4 materials by surface coating.
For more information, please follow the link below:https://www.winshinepower.com/

od **xehoten389** » 25 kvě 2022 10:47

od **xehoten389** » 03 čer 2022 06:04

od **weslo** » 05 črc 2022 23:03

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od **weslo** » 01 úno 2023 22:16

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Modification method of lithium iron phosphate battery

Modification method of lithium iron phosphate battery

Re: Modification method of lithium iron phosphate battery

Re: Modification method of lithium iron phosphate battery

Re: Modification method of lithium iron phosphate battery

Re: Modification method of lithium iron phosphate battery

Re: Modification method of lithium iron phosphate battery

Re: Modification method of lithium iron phosphate battery

Re: Modification method of lithium iron phosphate battery

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