Author ：Iflowpower – Portable Power Station Supplier
In order to solve this problem, people have studied pre-lithiance technology. By pre-lithiuming the electrode material, the non-reversible lithium loss caused by the formation of the SEI film is canceled to improve the total capacity and energy density of the battery. I.
Negative polar lithium technology is common pre-lithiuming method is negative lithium, such as lithium foil, lithium powder supplement, etc., is a pre-development pre-development. In addition, there is a technique of pre-lithiating using silicided lithium powder and electrolytic lithium saline solution.
1 lithium foil lithium lithium foil compensation is a technique for using the self-discharge mechanism. The potential of metal lithium is the lowest in all electrode materials, and when the electrode material is in contact with the metal lithium foil, the electron is moved to the negative electrode, accompanied by Li + in the negative electrode. Add the electrolytic solution on the silicon nanowire negative electrode grown on the stainless steel substrate, and then directly contact with the lithium metal foil.
The negative electrode test after the lithium is tested, and it is found that the open circuit voltage of no lithium is 1.55V, at 0.01 to 1.
00V first 0.1c discharged lithium-specific capacity of 3800mAh / g; the silicon nanowire after lifting The voltage is 0.25V, the first incense bit is 1600mAh / g.
The tin carbon negative electrode is directly in contact with the lithium foil that is infiltrated by the electrolyte fluid. Testing with semi-battery, the irreversible comparison capacity of tin carbon after lithium is reduced from 680 mAh / g to 65mAh / g. The negative electrode constitutes a whole battery, and the ICE tested at 3.
1 to 4.8V is close to 100% at 3.1 to 4.
8V, and the cycle is stable, and the magnification performance is better. Although it is directly in contact with the lithium foil, the negative electrode pre-lithiuming can be achieved, but the degree of pre-lithiuming is not easy to accurately control. Inadequate lithiation, it is not possible to improve the ICE; and the lithium is over, it may form a metal lithium coating on the surface of the negative electrode.
Z.Y.CAO et al for improving the safety of lithium foil tonics, the design of the active material / polymer / lithium metal three-layer structure negative electrode can be stabilized in the ambient air, sufficiently negative for processing.
The three-layer structure is: the lithium layer is coated with a polymethyl methacrylate protective layer and an active material layer on a lithium layer by electrochemically deposited metal lithium layer on a copper foil. 2 Stabilized lithium metal powder (SLMP) lithium powder supplement is proposed by Fumei, the development of SLMP is as high as 3600mAh / g, and the surface is covered with 2% to 5% lithium carbonate, which can be in a dry environment. use.
Applying SLMP to negative electrode pre-lithiating, there are two ways: add, or directly add to the negative surface surface. Conventional negative propries, use PVDF / NMP or SBR + CMC / deionized water systems, but SLMP is not compatible with polar solvents, only non-polar solvents such as hexane, toluene, so it cannot be combined in conventional Direct addition during pulp. With SBR-PVDF / toluene system, SLMP can be directly mixed in graphite electrode slurry.
After SLMP's pre-lithium, at 0.01 to 1.00 V, 0.
05c, the battery's ICE increased from 90.6% to 96.2%.
SLMP directly loaded into the dry negative surface is simpler than the drying process. The silicon-carbon nanotube negative electrode is used to pre-lithium-carbon nanotube negative electrode, and the mass fraction is 3% SlMP / toluene solution drops on the surface of the silicon-carbon nanotube, after toluene solvent, the tablet, activate. After pre-lithiuming, the first irreversible capacity of the negative electrode is reduced by 20% to 40%.
3 silicided lithium powder nano silicon powder size is small, more conducive to dispersion in the negative. In addition, it is in an expanded state, and the volume change in the cycle will not affect the structure of the entire electrode. At present, there is less research on silicided lithium lithium powder supplement, only J.
ZHAO, etc. The semi-battery system is charged with 0.01 to 1.
00 V at 0.01 to 1.00V, and after adding 15% silicide powder, the ICE of the silicon negative electrode is increased from 76% to 94%; add 9% silicided lithium powder intermediate carbon microspheres from 75 % Increase to 99%; add 7% silicided lithium powder graphite negative ICE increased from 87% to 99%.
4 Electrolytic lithium saline solution to make lithium, whether using lithium foil, SLMP or silicided lithium powder to support lithium,. High metal lithium has high prices, high activity, difficult operation, storage and transportation require high cost for protection. If the lithium process does not involve metal lithium, cost savings, improve safety performance.
The silicon can be carried out by electrolytic Li2SO4 aqueous solution in the electrolytic cell, and the sacrificial electrode is immersed in the copper wire in Li2SO4, and the lithium reaction is shown in the formula (1): Second, the typical positive tensions of the positive tonifying technique is A small amount of high-capacity material is added during the positive electrode seductive process. During the charging process, Li + is detached from high-capacity materials, supplementing the irreversible capacity loss of the first charge and discharge. At present, the material as the positive electrode lithium additive is mainly: lithium compound, nanocomposite and binary lithium compound based on conversion reaction, etc.
1 lithium compound uses lithium material Li1 + XNi0.5Mn1.5O4 to compensate for the irreversible capacity loss of Si-C | lini0.
5Mn1.5O4 full battery. The battery with a mixed positive electrode is 75% in a capacity retention ratio of 0.
33c at 3.00 to 4.78V, while the battery using pure lini0.
5 mn1.5O4 positive electrode is only 51%. Li2NiO2 can also be used as a positive supplementary lithium additive, but the stability in the air is poor.
Aluminum aluminum can be used to modify Li2NiO2, synthesized the Li2NiO2 material coated in air, and the lithium-lithium effect is excellent. 2 Nanocomposites based on transformation reactions Although a lithium compound has achieved a certain effect as a lithium-lithium additive, the first lithium effect is still limited to a lower specific capacity. Based on the nanocomposite of the conversion reaction, a large amount of lithium can be contributed during the first charging process of the battery during the battery, and the lithium reaction can not occur during the discharge process.
Y.m. SUN et al.
Studied M / Lithium oxide, M / fluorine, M / vulcanized (M = Co, Ni and Fe) as a positive electrode lithium additive. Through the synthetic nano-Co / lithium oxide composite material at 50 mA / g of 4.1 ~ 2.
5V cycle, the first charge is 619mAh / g, the discharge ratio is only 10mAh / g; after exposing 8h in the ambient air, remove Lithium is only 51mAh / g less than that of the initial value, and after 2D, the dehydric ratio is still 418mAh / g, which has good environmental stability, which can be compatible with the production process of commercial batteries. Lithium fluorinated lithium lithium content is high, good stability, is a potential positive tonic lithium material. With the m / LIF nanomaterials configured by the conversion reaction, it can overcome the problem of LIF conductivity and low ionic guidelines, high electrochemical decomposition potential, and harmful to decomposition products such that lithium fluoride is a superior positive electrode resolution additive.
The theoretical capacity of lithium sulfide reaches 1166 mAh / g, but as a lithium-lithium additive, there are still many problems need to be solved, such as compatibility, insulation, environmental stability, etc. Although there is a higher lithium-lithium capacity, the nanocomposites based on the conversion reaction are residual without activity of metal oxides, fluorides, and sulfides, etc., reduce the energy density of the battery.
3 binary lithium compound binary lithium compound theory is much higher than the capacity. The theoretical specific capacity of Li2O2, Li2O and Li3N reaches 1168mAh / g, 1797mAh / g and 2309mAh / g, respectively, and only a small amount of addition is required, similar to the lithium effect can be achieved. In theory, the residue of these materials after the lithium is O2, N2, etc.
, can form a gas discharged during the SEI film in the battery. The commercial Li3N is grinded into a powder having a particle size of 1 to 5 μm, which is used as a lithium additive. Under the semi-battery system, 1% and 2% Li3N of LiCoO2 electrode were added, and the first charge ratio capacity of 0.
1c at 3.0 to 4.2V was 167.
6mAh / g and 178.4mAh / g, respectively, and the pure LiicoO2 rose by 18.0mAh / G, 28.
7mAh / g. Mix commercial Li2O2 with NCM, compensate for lithium loss during the first charging process of graphite negatives. NCM in the mixed electrode serves as a double effect of active materials and catalysts.
In order to efficiently catalyze the decomposition Li2O2, 1% ball milling for 6 h was added to the NCM obtained in the positive electrode. The whole battery is 2.75 ~ 4.
60V charge and discharge, 0.3c can be reversible than 165.4mAh / g, more than 20.
5% of the ink | NCM full battery. Test showed that the oxygen released by Li2O2 decomposes consumes limited Li + in all batteries, resulting in a significant capacity attenuation of the total battery of the addition of Li2O2, but after the gas is discharged, the capacity can be recovered. The first charging of the battery in the actual production process is carried out in an open system, and it is discharged to form a SEI film and some side reactions generated before the sealing, so that the effect of O2 release can be reduced.
Third, conclusions and prospects compare two lithium-lithium methods, negative lithium-lithium-lithium reagents (lithium foil, lithium powder, and silicide lithium lithium powder) have high capacity, but complex operation, high environmental requirements; to add lithium in the positive electrode The positive rectification of the additive is high in safe stability, and has good compatibility with existing battery production technology. The research of the future negative lithium-lithium technology should focus on the stability, development and industrial production of the battery, and the simple technical solution, and the positive complement should focus on the development of high blood lithium capacity, small use. Additive system with small residual amount of lithium.
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