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About electric vehicle battery repair technology - in addition to vulcanization which method is more suitable for battery repair 

About electric vehicle battery repair technology - in addition to vulcanization which method is more suitable for battery repair 


Repair battery, in addition to vulcanization decomposition.

We've done a lot of hydrotherapy, or lab work.

Or short time effect can, long-term effect is not good.

Since the use of pulse maintenance, the results are very good.

Battery repair technology

I once stored batteries in the warehouse for 2 years, the capacity has dropped to almost zero, and the battery voltage has gone from a few tenths of minus to 2V.

Such cells undergo pulse repair and overcharge repair, restoring capacity to 97% of nominal capacity.

Three percent of the batteries were not repairable.

Battery repair technology

After autopsy, it was found to be a lead short circuit.

After deep cycle charge and discharge test, its life is basically the same as the original battery.

Therefore, it is recommended that you use pulse repair technology.

In particular, sealed batteries have different damage every time they are disassembled. Even if temporary repair is available, it has a great impact on the life of the battery.

So, it is better to repair the battery of electric bicycle by pulse.

In addition, the treatment of rich liquid pot water has great drawbacks and endangers health.

Do not support the so-called teaching harm harm yourself, suggest repair to understand, not blind.

There are many problems in the use of lithium ion battery at low temperature, such as low specific discharge capacity, discharge voltage drop, no charge, poor cycle rate performance, lithium separation and so on.

The study found that restrict lithium ion the root cause of the low temperature performance due to low temperature hinders the lithium ion battery charging and discharging process of Li + and electronic effective transmission, whether the charge transfer process of the electrode/electrolyte interface or Li + in SEI, electrolyte and electrode in the transport process are affected by low temperature, will add the battery polarization, resulting in battery performance becomes poor.

Specific factors are as follows [] :

(1) At low temperature, the viscosity of electrolyte increases, even partial solidification, resulting in low ionic conductivity;

(2) At low temperature, the compatibility between electrolyte, electrode and diaphragm becomes worse;

(3) At low temperature, the precipitated lithium metal reacts with electrolyte, resulting in the increase of the thickness of solid electrolyte interface (SEI).

(4) The diffusion coefficient of lithium ion decreases and the charge transfer impedance (Rct) increases significantly at low temperature.

In recent years, some researchers have decomposed the influence of low temperature on lithium ion batteries through different test methods and experimental designs, and analyzed the important limiting factors affecting low temperature performance.

S.s. Chang et al. [] tested the AC impedance of lithium-ion batteries at different temperatures. Through fitting, they believed that the impedance of the whole battery was composed of three parts, namely, body impedance Rb, solid electrolyte interface membrane impedance RSEI and charge transfer impedance Rct.

The results are shown in FIG. 2. With the decrease of temperature, the three impedance values increase, and Rct changes most obviously, indicating that Rct is more sensitive to temperature. Meanwhile, the author also calculates the proportion of Rct in the impedance of the whole battery.

The Rct/Rcell ratio is close to 100%, indicating that at low temperatures, the performance importance of the battery is limited by the greatly increased Rct of the charge transfer impedance.

Huang et al. [] separated the positive electrode, negative electrode and electrolyte components into separate studies in order to find out the important contradiction affecting their low temperature discharge. The author found that at -20℃, compared with electrolyte and positive electrode, the performance of the negative electrode attenuates the most seriously, and Li+ is easier to extricate from the graphite layer, but harder to embed.

Based on this, the author proposed that an important factor limiting the low temperature performance of the battery is the rapid increase of the diffusion impedance of Li+ in the cathode active material at low temperature. However, the author did not provide specific impedance spectrum and corresponding fitting data of diffusion impedance as described in literature [3].

To sum up, the following conclusions can be drawn:

About most of the system, the low temperature when the charge transfer rate and lithium ion diffusion rate of decline, leading to poor low temperature performance of lithium-ion batteries is important reason, which represents the electrode diffusion impedance and charge transfer impedance Faraday electrolyte interface reaction rate, namely the temperature decrease to lower electrode electrochemical reaction rate, led to a larger electrochemical polarization,

Thus affecting the overall discharge performance of the battery.

Improvement of low temperature performance of electrolyte, anode material and anode material

Electrolyte, positive electrode and negative electrode are three major components of lithium ion battery. Improving the low temperature performance of the battery from the perspective of materials is the most basic way to develop low temperature lithium ion battery.

3.1 Improvement of low temperature performance of electrolyte

Electrolyte is used for Li+ transport between anode and cathode in lithium ion battery, and its ionic conductivity and SEI film forming performance have a significant impact on the low temperature performance of battery.

The performance of the electrolyte depends largely on its constituent materials: solvents, lithium salts and additives.

At present, the important ways to improve the low temperature performance of electrolyte are adding cosolvent, developing new lithium salts and adding additives.

As for traditional solvents, such as EC, DMC, DEC, etc., their freezing point is high, and the conductivity of the electrolyte composed of them will drop sharply at low temperature.

Therefore, many researchers focus on finding suitable co-solvents that can reduce the freezing point and viscosity of electrolyte, in order to obtain electrolyte with low freezing point and high conductivity.

When selecting a cosolvent, its physical and chemical parameters such as viscosity, dielectric constant and freezing point should be considered comprehensively. The physical and chemical parameters of common solvents are shown in Table 1.

From the perspective of Coulomb's law, under the same conditions, the greater the dielectric constant, the stronger the dissociation use, the greater the ionization degree of lithium salt, the higher the ionic conductivity.

From the perspective of ion migration, the higher the viscosity, the slower the ion movement, the lower the ionic conductivity.

From the table, it can be seen that ethyl acetate (EA), methyl formate (MF), methyl acetate (MA) and toluene (TOL) and & Gamma have low freezing point and low viscosity.

-butyrolactone (γ

-BL) are the alternative co-solvents to improve the low temperature performance of electrolyte.

Different lithium electrolytes directly affect the ionic conductivity and SEI properties of electrolyte.

Lithium hexafluorophosphates (LiPF6) is the most widely used commercial lithium salt at present, but LiPF6 is easy to hydrolyze and has poor thermal stability, and can form effective SEI film only in electrolyte with EC. However, the high freezing point of EC (37℃) cannot meet the requirements of low-temperature electrolyte, so LiPF6 is generally not suitable for low-temperature electrolyte as lithium salt.

[1] At present, the important low temperature lithium salt system is borate: lithium tetrafluoroborate (LiBF4), lithium dioxalate borate (LiBOB) and their combination lithium difluoroxalate borate (LiODFB).

In addition, ionic liquid, as a new electrolyte, has been applied in low-temperature batteries because of its wide electrochemical window, high safety and wide temperature range of -81℃~280℃ [].

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