Thermal Simulation of Discharge Process of Soft-packed Lipo Battery

Studies have shown that temperature has an important effect on the performance of energy storage devices. Excessive temperature causes electrolyte decomposition, performance degradation, shortened life, and excessive temperature can even burn the device. In addition, in actual use, a large battery pack is formed in the form of a plurality of cells in series and parallel, and the internal heat is rapidly accumulated due to poor heat dissipation performance, resulting in rapid temperature rise and safety problems. Therefore, studying the thermal characteristics of lithium ion capacitors is of great significance for its future wide application.


Research Background


With the increase of car ownership, the traditional fossil energy is depleting, and the energy problems and climate problems have become an urgent problem for all countries. For this reason, countries have vigorously developed new energy industries and vigorously promoted the development of new energy vehicles. As a core component of electric vehicles, energy storage devices have become a research hotspot in recent years. Lithium-ion batteries have been widely used in electric vehicles due to their high energy density. Supercapacitors are widely used in aerospace, defense technology and other fields due to their high power density, good safety performance and long cycle life. However, their low energy density still cannot meet the needs of electric vehicles. Lithium-ion capacitor (LIC) is a hybrid energy storage device developed in recent years. It combines the long life of traditional supercapacitor, high power density, high energy density of lithium ion battery and low self-discharge rate. Its energy density is 3 to 5 times of double-layer capacitors, power density up to 20 kW / kg, so in the field of new energy electric vehicles, low temperature start power, wind power, urban rail transit, braking energy recovery, smart grid, UPS uninterruptible power supply, etc. It shows a broad application prospect. 


Studies have shown that temperature has an important effect on the performance of energy storage devices. Excessive temperature causes electrolyte decomposition, performance degradation, shortened life, and excessive temperature can even burn the device. In addition, in actual use, a large battery pack is formed in the form of a plurality of cells in series and parallel, and the internal heat is rapidly accumulated due to poor heat dissipation performance, resulting in rapid temperature rise and safety problems. Therefore, studying the thermal characteristics of lithium ion capacitors is of great significance for its future wide application.


Innovation and problem solving


As a new type of electrochemical energy storage device, the thermal performance of lithium ion capacitors has not been paid attention to. Therefore, it is important to study the temperature field distribution of lithium ion capacitors during discharge lipo batteries. By establishing a three-dimensional finite element model, the workbench finite element software was used to simulate the temperature field of the soft-package lithium-ion capacitor discharge process under different environmental temperatures and different discharge rates. The results show that during the discharge process, the temperature gradually rises and the highest temperature appears in the central region of the cell, and the higher the discharge rate, the higher the temperature rise; the internal temperature difference of the lithium ion capacitor monomer is less affected by the external environment temperature. The comparison with the experimental results shows that the heat generation model can better reflect the temperature rise of the lithium ion capacitor during the actual discharge process, which is helpful to its performance optimization and structural design.


in conclusion


The HPPC test of lithium ion capacitors is used to obtain open circuit voltage and ohmic internal resistance under different temperature conditions. The heat generation rate of lithium ion capacitors is determined by Bernardi heat generation model. Then, the three-dimensional thermal effect model is established according to the knowledge of thermodynamics and heat transfer. The finite element software was used to simulate the temperature field of the lithium ion capacitor, and compared with the experimental results, the results show that:


(1) The temperature of the lithium ion capacitor gradually increases during the discharge process. After the discharge, the cell center temperature is the highest, and increases with the discharge rate, and the lowest temperature appears at the ear.


(2) After the end of discharge, the internal temperature difference of the lithium ion capacitor monomer increases with the increase of the discharge rate. When the discharge rate is the same, the temperature difference of the monomer at different ambient temperatures is close.


(3) The model can better simulate the temperature change and heat generation rate of lithium ion capacitor under different conditions, and accurately display the temperature field distribution of lithium ion capacitor during discharge process.

Polarizing Cube Beamsplitters from Siaon Optoelectronic

Siaon Optoelectronic provide a series of precision optical components


Polarizing Cube Beamsplitters split randomly polarized beams into two orthogonal,linearly, polarized components-S-polarizedlight is reflected at a 90deg. Angle while P-polarized light is transmitted. Each beamsplitter consists of a pair of precision high tolerance right angle prisms cemented together with a dielectric coating on the hypotenuse of one of prisms.

Siaon Optoelectronic precision optical component Right Angle Prisms

Fuzhou Siaon Optoelectronic Technology Co., Ltd. provide Right Angle Prisms


Right angle prisms are used to deviate light by 90 degree or 180 degree. Depending on the orientation of the prisms, right angle prisms produce the inverted left handed image. Utilizing the character of critical angle, highly-efficient reflection inside is one of basic function of right angle prisms. Right angle prisms are easy to be mounted, have better stability and hardness for mechanical stress, are used in telescope and other optical system.
Material: BK7 A Grade Optical Glass
Dimension Tolerance:+0.0, -0.2mm
Clear Aperture: >80%
Flatness: λ/4 632.8nm 
Surface Quality:60-40
Bevel:0.2mm to 0.5mm x 45°
Coating :Uncoated


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