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The factor of affecting lithium-ion cell's internal resistance

The factor of affecting lithium-ion cell's internal resistance

The factor of affecting lithium-ion cell includes, design of cell’s cathode piece and tab, raw material, manufacturing process, applications, etc. The article mainly expound that raw material’s effect on lithium-ion cell’s internal resistance of lithium battery.


Active material for positive and negative electrodes: the positive electrode of lithium cell stores the li-ion, it mainly determines the performance of the cell. Positive electrode material mainly improve the electronic conductivity between particles through coating and doping. Doping the Ni enhance the strength of P-O chemical bond, stabilize the structure of LiFePO4/C, optimize the volume of unit cell, effectively reduce the electron transfer resistance of the positive electrode material. Through the simulation analysis of the electrochemical thermal coupling model, it is known that under the condition of high-rate discharge, the activation polarization, especially the significant increase in the activation polarization of the negative electrode, is the main reason for the serious polarization. Reducing the particle size of the negative electrode can effectively reduce the active polarization of the negative electrode. When the solid phase particle size of the negative electrode is reduced by half, the active polarization can be reduced by 45%. Therefore, in terms of battery design, research and improvement of positive and negative materials are essential.


Conductive agent: Graphite and carbon black are widely used in the field of lithium batteries because of their good properties. Compared with graphite-based conductive agent, the positive electrode with carbon black-based conductive agent has better battery rate performance, because graphite-based conductive agent has a flaky particle morphology, which causes a large increase in pore tortuosity at a large rate, and Li liquid phase diffusion is easy to occur The phenomenon that the process limits the discharge capacity. The battery with added CNTs has lower internal resistance, because compared to the point contact between graphite/carbon black and the active material, the fibrous carbon nanotubes are in line contact with the active material, which can reduce the interface impedance of the battery.


Current collector: Reducing the interface resistance between the current collector and the active material and improving the bond strength between the two are important means to improve the performance of lithium batteries. Coating a conductive carbon coating on the surface of the aluminum foil and corona treatment on the aluminum foil can effectively reduce the interface impedance of the battery. Compared with ordinary aluminum foil, the use of carbon-coated aluminum foil can reduce the internal resistance of the battery by about 65%, and can reduce the increase in the internal resistance of the battery during use. The AC internal resistance of corona treated aluminum foil can be reduced by about 20%. In the commonly used 20%~90% SOC range, the overall DC internal resistance is relatively small and the increase is gradually smaller as the depth of discharge increases.


Diaphragm: The ion conduction inside the battery depends on the diffusion of Li ions in the electrolyte through the porous diaphragm. The liquid absorption and wetting ability of the diaphragm is the key to forming a good ion flow channel. When the diaphragm has a higher liquid absorption rate and porous structure, It can improve the conductivity, reduce the battery impedance, and improve the rate performance of the battery. Compared with ordinary base membranes, ceramic diaphragms and rubber-coated diaphragms can not only greatly improve the high temperature shrinkage resistance of the diaphragm, but also enhance the liquid absorption and wetting ability of the diaphragm. The addition of SiO2 ceramic coating on the PP diaphragm can make the diaphragm absorb liquid The volume increased by 17%. Coating 1μm PVDF-HFP on the PP/PE composite diaphragm, the liquid absorption rate of the diaphragm is increased from 70% to 82%, and the internal resistance of the cell is reduced by more than 20%.


PLB has deeply researched the mechanism of the influence of raw materials on the internal resistance of the cells, and optimized the design. The 26650 cells produced have the excellent characteristics of low internal resistance and high consistency.

Statement of the internal resistance of influencing of the lithium cell(electrode and tabs)

Statement of the internal resistance of influencing of the lithium cell(electrode and tabs)

1. The influencing factors that affect the internal resistance of lithium-ion batteries include: cell electrode and tabs, raw materials, manufacturing processes, applications, and many other aspects. This article mainly discusses the influence on the internal resistance of the lithium battery from the design of the cell electrode and tab.


2. In the cell structure design, in addition to the riveting and welding of the cell structure itself, the length of the cell electrode, the material, quantity, size, and location of the tabs directly affect the internal resistance of the cell. To a certain extent, increasing the number of tabs can effectively reduce the internal resistance of the battery. The position of the tab can also affect the internal resistance of the cell. The internal resistance of the winding battery with the tab position at the head of the cathode and anode electrode is the largest, and compared to the winding battery, the laminated battery is equivalent to dozens of small battery in parallel, and its internal resistance is smaller.


3. The 26650 battery cells designed and manufactured by Power Long Battery are optimized in terms of the material, quantity and location of the tabs. The battery cells have obvious advantages of low internal resistance and good consistency.

What is the effect of the SEI film on the battery performance?

What is the effect of the SEI film on the battery performance?

The use of THE SEI should be analyzed from its own characteristics: THE SEI is an interface layer between the electrode material and electrolyte, which separates the two.Has the characteristics of solid electrolyte.Li+ can pass, but electrons can't.


1. The degree of corrosion caused by the reaction between lithium metal and electrolyte components is determined by the passivation performance of the SEI film on its surface.


2. In the dissolution-deposition process of lithium, it must occur through THE SEI film, and the migration of lithium ions through the SEI film is the rate control step of the lithium deposition-dissolution process, which determines the uniformity of the lithium deposition-dissolution process.When the lithium deposition is uniform, the metal lithium can largely prevent corrosion during the cycling process, so that the lithium electrode can achieve better cycling efficiency.


3. lithium, lithium ion can occur through the SEI film deposition and dissolution process, but in the process of dissolution and deposition, because of the important composed of ionic components of SEI is difficult to adapt to the process of lithium surface morphology change, therefore the SEI film ruptures, lead to the emergence of the nude lithium and its further reaction of the electrolyte, so repeated deposition in lithium - solvent thermal process, lithium and electrolyte composition is consumed, lead to lithium electrode cycle performance attenuation.


4, the SEI film breakdown can lead to form some highly active, so as to accelerate the deposition of these sites lithium and solvent speed, leading to lithium electrode surface current distribution inhomogeneity, inhomogeneity and dendrite formation leads to a series of security problems, this is the commercialization of metallic lithium battery application was the important reason for the failure.

What effect does charging time have on the battery?

What effect does charging time have on the battery?

Charging mode is generally fast charge, slow charge.Fast charging Adopts large current to directly charge the battery through the non-vehicle charger, which can be fully charged with 80% capacity in half an hour;Slow charge refers to ac charging, charging process takes 6 hours to 8 hours.

What's wrong with the battery charge?

What's wrong with the battery charge?

This is the existence of safety redundancy in the battery, reserve a part of the power to prevent the battery overcharge and excessive discharge.For example, the original battery capacity is 100%, but the actual battery capacity is about 80%-90%, and the value after the power redundancy is the actual power that the car owner can use.Because during the charging process, the battery can't be too full, nor can it be discharged into space.If the battery is fully charged every time, it will greatly reduce its service life;Charging too full, once the charging system has a fault, it is possible to cause safety accidents because of "overcharging".

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