Method for constructing electrolyte interface film of lithium-ion battery by dual-pulse excitation

Abstract

The present invention discloses a method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation. By using dual-pulse excitation, under the conditions of set temperature, magnetic field, electromagnetic wave and particle flow, a lithium-ion battery, an electrode or an independent electrolyte interface film is directly energized, the state of charge of the lithium-ion battery is adjusted, the lithium-ion battery is charged to a full charge state, and then discharged to an empty charge state. Through repeated charge and discharge operations, an electrolyte interface film with uniform composition, thickness, structure, high consistency and controllable process is constructed. By constructing the above electrolyte interface film, the comprehensive performance of the lithium-ion battery is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery research, and particularly relates to a method for constructing an electrolyte interface film of a lithium-ion battery by using a double-pulse excitation. Background Art

[0002] The production process of lithium-ion batteries includes a pre-charging and an aging process. The traditional pre-charging process generally refers to, under different temperature environments, charging and discharging the battery with a low rate after injecting the electrolyte and leaving it for a period of time, and finally stabilizing the battery at a certain state of charge and sending it to the aging process. Specifically, during the charging and discharging process of the battery in the pre-charging process, at the interface where the battery electrode contacts the electrolyte, some components of the electrolyte will undergo electrochemically-driven reduction and oxidation reactions, and the reaction products will initially form an electrode-electrolyte interface on the electrode surface, that is, an electrode protection film. The traditional aging process refers to leaving the battery that has undergone the pre-charging process for a long time under different temperature environments. Specifically, during the placement process of the battery in the aging process, slow non-electrochemically-driven reduction and oxidation reactions occur at the contact interface between the electrode and the electrolyte. Similarly, the reaction products will further form an electrode-electrolyte interface, further developing and improving the electrode protection film. During the formation, development, and improvement of the above electrode protection film, there are accompanied by the generation of gas products, the loss of active lithium acting on the film formation, and the irreversible loss of active lithium sites in the electrode material.

[0003] After the lithium-ion battery has undergone the pre-charging and aging processes, the construction of the electrode-electrolyte interface is completed, that is, the construction of the electrode protection film, and the stabilization of the reversible active sites of the electrode material. This electrode-electrolyte interface can prevent the further decomposition of electrolyte components, reduce the generation of gas products, reduce the loss of active lithium acting on the film formation, and reduce the irreversible loss of active lithium sites in the electrode material. At the same time, this film is an ion-conducting film, and lithium ions can pass through freely. Therefore, the construction of this electrode-electrolyte interface can improve the cycle performance, service life, rate performance, high-temperature tolerance performance, and safety performance of the lithium-ion battery.

[0004] However, the traditional pre-charging process uses a low-rate constant current charge-discharge process, which not only takes a long time and has high charge-discharge energy consumption, but also keeps the electrode surface in the ion diffusion control stage for a long time. The current density is concentrated at the lithium ion concentration advantage sites, the high reaction activity advantage sites on the material surface, the conductivity advantage sites, and the interface film growth edge advantage sites. Therefore, the electrode electrolyte interface film will grow concentratedly at the advantage sites, and the interface film at the advantage sites will be thicker than that at the disadvantage sites, and the proportion of the advantage decomposition products at the advantage sites is larger. Similarly, for the aging process, not only does it take a long time and have high greenhouse energy consumption, but the interface film and the advantage products will still continue to thicken and increase in proportion at the self-reaction advantage sites. Therefore, the electrolyte interface film constructed by the traditional process has uneven distribution, inconsistent composition, large thickness difference, and large structural difference, that is, under the traditional process, the formation and development of the electrolyte interface film is an uncontrollable process, and then the impact on the battery performance is also uncontrollable. At the same time, the difference in the growth of the interface film will lead to the difference in electrode protection, that is, there will be a difference in the degree of protection of the interface film for the positive and negative electrodes; in the traditional process, there is a large amount of gas generation, a large loss of active lithium, and a large loss of active lithium sites in the electrode material. Therefore, the traditional pre-charging and aging process has great limitations in improving the comprehensive performance of the battery.

[0005] In summary, if a suitable method can be found to construct the electrolyte interface film, reduce the difference in the growth of the electrolyte interface film, reduce the gas generation amount, reduce the loss of active lithium, and reduce the loss of active lithium sites, making the production of the electrolyte interface film a controllable process, this is of great significance for further improving the comprehensive performance of lithium-ion batteries. Summary of the Invention

[0006] To solve the deficiencies of the above-mentioned prior art, the present invention provides a method for constructing an electrolyte interface film of a lithium-ion battery by double-pulse excitation. By using double-pulse excitation, under the conditions of set temperature, magnetic field, electromagnetic wave, and particle flow, an electric current is directly applied to the lithium-ion battery, the electrode, or an independent electrolyte interface film, the state of charge of the lithium-ion battery is adjusted, the lithium-ion battery is charged to a full charge state, and then it is discharged to an empty charge state. Through repeated charge-discharge operations, an electrolyte interface film with uniform composition, thickness, and structure, high consistency, and a controllable process is constructed. By constructing the above electrolyte interface film, the comprehensive performance of the lithium-ion battery is further improved.

[0007] The technical effects to be achieved by the present invention are realized through the following solutions:

[0008] The present invention provides a method for constructing an electrolyte interface film of a lithium-ion battery by double-pulse excitation, which is characterized by including the following steps:

[0009] S01, under set conditions, perform double-pulse excitation on the lithium-ion battery to adjust the state of charge of the lithium-ion battery;

[0010] S02, adjust the parameters of the double-pulse excitation according to the state of charge;

[0011] S03, repeat S01 - S02 to construct the electrolyte interface film of the lithium-ion battery.

[0012] The present invention provides a method for constructing an electrolyte interface film. Under set conditions, a lithium-ion battery is excited with a double-pulse power supply, and the lithium-ion battery is energized with pulse positive and negative currents or voltages under set waveforms, frequencies, and duty cycles. The construction method in the present invention does not limit the initial state of the lithium-ion battery. For a newly assembled lithium-ion battery, a uniform electrolyte interface film can be formed inside the battery through this method; for an old lithium-ion battery after being used for a period of time, the uniformity of its electrolyte interface film can be improved through this method. The present invention does not limit the state of charge of the battery before and after the double-pulse excitation, and a suitable state of charge can be set according to needs. Preferably, the battery is charged to full charge and then discharged to empty charge through double pulses, and the operation of charging to full charge - discharging to empty charge is repeated, which is beneficial to forming an electrolyte interface film with a more uniform structure.

[0013] In the present invention, the battery electrode or the independent electrolyte interface film can be directly energized to construct the electrode electrolyte interface film or the independent electrolyte interface film. After being energized for a certain period of time, the state of charge of the battery changes, and then the parameters of the double-pulse power supply are adjusted according to the state of charge of the battery, and then the lithium-ion battery is energized. Through repeated charge and discharge operations, an electrolyte interface film with uniform composition, thickness, structure, high consistency, and controllable process is constructed. By constructing the above electrolyte interface film, the comprehensive performance of the lithium-ion battery is further improved.

[0014] In the present invention, the double-pulse current or voltage can reverse the increase in lithium-ion concentration in the interval where the lithium-ion concentration on the surface of the lithium-ion battery electrode material decreases sharply, thereby effectively reducing the rate of decrease in the lithium-ion concentration on the surface of the electrode material and improving the uniformity of lithium ions on the surface of the electrode material; at the same time, the reverse pulse has a certain elimination effect on the dominant sites of the film, can reduce the difference between the dominant sites and the weak sites, avoid the concentrated growth of the interface film at the dominant sites, and improve the uniformity of the interface film. On the other hand, repeated energization operations can update and reconstruct the current conduction and current density network, reduce the active sites of the electrode material, narrow the dominant effect of the high-conductivity sites and the interface film growth edge on the current density, and make the current density evenly distributed to the greatest extent. Repeated energization operations can also inhibit the growth of the dominant sites of the electrolyte interface film, make the proportion of the dominant decomposition products tend to be uniform, and make the overall distribution of the interface film uniform.

[0015] Further, the lithium-ion battery is a commercial lithium-ion battery, a high-temperature lithium-ion battery, a solid-state lithium-ion battery, a lithium-air battery or a lithium-sulfur battery.

[0016] Further, the lithium-ion battery is a cylindrical lithium-ion battery, a soft-pack lithium-ion battery or a prismatic lithium-ion battery.

[0017] The method for constructing the electrolyte interface film in the present invention has wide applicability, and has good applicability to common lithium-ion batteries at present and different specifications and models of common lithium-ion batteries, and can be used to construct the electrolyte interface film of the above-mentioned lithium-ion batteries.

[0018] Preferably, the lithium-ion battery is a lithium-ion battery after adding the electrolyte and standing; the standing time is 1-30 h.

[0019] Further, the set conditions include set temperature parameters, magnetic field parameters, electromagnetic wave parameters, and particle flow parameters.

[0020] Preferably, the temperature is -50~1200 °C; the magnetic field strength is 0.01-1000 T; the electromagnetic wave wavelength is 10 -10 ~10 12 m, and the intensity is 0.01~10 15 W / m 2 ; the particle flow wavelength is 10 -20 ~10 -10 m, and the intensity is 0.01~10 15 W / m 2 .

[0021] Further, the waveform of the double-pulse excitation is one or several of sine, circular, square, triangular, exponential, and logarithmic.

[0022] Further, in S03, S01~S02 are repeated, the lithium-ion battery is adjusted to a fully charged state, and then it is adjusted to a discharged state.

[0023] Further, the electrolyte interface includes an electrode-electrolyte interface film and an independent electrolyte interface film.

[0024] Further, the morphology of the electrolyte interface film is one or several of linear, tubular, flaky, spherical or porous.

[0025] In the present invention, the parameters of double-pulse excitation, environmental parameters, magnetic field parameters, electromagnetic wave parameters, and particle flow parameters can be adjusted according to the state of charge of the lithium-ion battery, so as to regulate the generation rate and distribution state of the dominant decomposition products, thereby controlling the composition, film-forming capacity, film-forming thickness, and film-forming structure of the electrolyte interface film. By adjusting the film-forming process, the problem of the difference in the growth of the electrolyte interface film is solved. At the same time, the gas generation amount is reduced, the loss of active lithium is reduced, and the loss of active sites of the electrode material is reduced. Finally, the comprehensive performance of the lithium-ion battery is improved by constructing a uniform electrolyte interface film.

[0026] The present invention has the following advantages:

[0027] 1. In the present invention, the electrolyte interface film is constructed by the method of double-pulse excitation. Compared with the traditional pre-charging and aging process, the operation time is shortened and the energy consumption is greatly reduced.

[0028] 2. The electrolyte interface film constructed by double-pulse excitation in the present invention has good uniformity, and the film-forming composition, film-forming capacity, film-forming thickness, and film-forming structure are uniform.

[0029] 3. In the present invention, the double-pulse excitation parameters, environmental parameters, magnetic field parameters, electromagnetic wave parameters, and particle flow parameters can be adjusted according to the state of charge of the lithium-ion battery, realizing the controllable operation of the construction of the electrolyte interface film.

[0030] 4. The method for constructing the electrolyte interface film in the present invention has a wide range of applications and has good applicability to lithium-ion batteries of different models, different specifications, and different initial states. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the double-pulse current in the present invention.

[0032] Figure 2 It is a working schematic diagram of constructing the electrolyte interface film in the present invention.

[0033] Figure 3 It is a cyclic performance graph of the lithium-ion battery in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described in detail below with reference to the drawings and embodiments.

[0035] 1. Construction of the electrode electrolyte interface film.

[0036] Example 1

[0037] In this embodiment, the lithium-ion battery is an 18650 cylindrical lithium-ion battery. The lithium-ion battery is left standing for 24 h and then subjected to double-pulse excitation under set conditions. The set conditions are as follows: the temperature is 60 °C; the magnetic field strength is 2 T, the magnetic field direction is parallel to the central axis of the cylinder and faces the positive electrode; the electromagnetic wave wavelength is 5×10 -7 m, and the intensity is 10 W / m 2 , the electromagnetic wave direction is parallel to the central axis of the cylinder and faces the positive electrode; the particle flow wavelength is 5×10 -11 m, and the intensity is 100 W / m 2 , and the particle flow direction is parallel to the central axis of the cylinder and faces the positive electrode.

[0038] The positive and negative currents of the double-pulse power supply are as shown in the appendix Figure 1 . The waveform of the double-pulse excitation is triangular, the positive peak value H + is 2C, the negative peak value H - is 1C, the frequency is 1 kHz, and the positive and negative duty cycles are 50% and 30% respectively. During the charging process, the area S + of the charging current waveform is greater than the area S - of the discharging current waveform. During the discharging process, the area S - of the discharging current waveform is greater than the area S + of the charging current waveform.

[0039] The lithium-ion battery is energized using a double-pulse power supply. The schematic diagram of the energization operation is as shown in the appendix Figure 2 . The state of charge of the battery is adjusted to 5% SOC, and then double-pulse excitation is continued (the double-pulse excitation parameters remain unchanged). The battery is charged to the fully charged state of 100% SOC and then discharged to the empty state. The construction of the electrode electrolyte interface film is completed.

[0040] Example 2

[0041] In this embodiment, the lithium-ion battery is a 2614891 square lithium-ion battery. The lithium-ion battery is left standing for 24 h and then subjected to double-pulse excitation under set conditions. The set conditions are as follows: the temperature is 60 °C; the magnetic field strength is 3 T, the magnetic field direction is perpendicular to the plane of the square electrode plate and faces the positive electrode; the electromagnetic wave wavelength is 8×10 -7 m, and the intensity is 50 W / m 2 , the electromagnetic wave direction is perpendicular to the plane of the square electrode plate and faces the positive electrode; the particle flow wavelength is 3×10 -11 m, and the intensity is 90 W / m 2 , and the particle flow direction is perpendicular to the plane of the square electrode plate and faces the positive electrode.

[0042] The waveform of the double-pulse excitation is square, the positive peak value H + is 3C, the negative peak value H -is 1.5C, the frequency is 1KHz, and the positive and negative duty cycles are 40% and 45% respectively.

[0043] A dual-pulse power supply is used to energize the lithium-ion battery. The state of charge of the battery is adjusted to 15% SOC, and then the dual-pulse excitation is continued. The dual-pulse excitation is adjusted to a positive peak value H + of 2C and a negative peak value H - of 1C, the frequency is 1KHz, and the positive and negative duty cycles are 55% and 35% respectively. The battery is charged to a fully charged state of 100% SOC and then discharged to an empty state. The construction of the electrode-electrolyte interface film is completed.

[0044] Example 3

[0045] In this example, the lithium-ion battery is a 2014891 soft-pack lithium-ion battery. The lithium-ion battery is left standing for 24h and then subjected to dual-pulse excitation under set conditions. The set conditions are: temperature 60°C; magnetic field strength 2T, magnetic field direction perpendicular to the plane of the soft-pack electrode and facing the positive electrode; electromagnetic wave wavelength 4×10 -7 m, intensity 30W / m 2 and the electromagnetic wave direction is perpendicular to the plane of the soft-pack electrode and facing the positive electrode; particle flow wavelength 7×10 -11 m, intensity 120W / m 2 and the particle flow direction is perpendicular to the plane of the soft-pack electrode and facing the positive electrode.

[0046] The waveform of the dual-pulse excitation is square, the positive peak value H + is 5C, the negative peak value H - is 3C, the frequency is 1KHz, and the positive and negative duty cycles are 50% and 40% respectively.

[0047] A dual-pulse power supply is used to energize the lithium-ion battery. The state of charge of the battery is adjusted to 10% SOC, and then the dual-pulse excitation is continued. The dual-pulse excitation is adjusted to a positive peak value H + of 3.5C and a negative peak value H - of 2.5C, the frequency is 1KHz, and the positive and negative duty cycles are 60% and 30% respectively. The battery is charged to a fully charged state of 100% SOC and then discharged to an empty state. The construction of the electrode-electrolyte interface film is completed.

[0048] Example 4

[0049] Compared with Example 1, the difference in this example is that during the energization operation, the state of charge of the battery is adjusted to 10% SOC, and then the dual-pulse excitation is continued (the dual-pulse excitation parameters remain unchanged). The battery is charged to a state of 110% SOC and then discharged to a state of 8% SOC. The construction of the electrode-electrolyte interface film is completed.

[0050] Example 5

[0051] Compared with Example 1, the difference in this example is that during the power-on operation, the state of charge of the battery is adjusted to 10% SOC, and then the double-pulse excitation is continued (the double-pulse excitation parameters remain unchanged), the battery is charged to 115% SOC state, and then discharged to 15% SOC state. The construction of the electrode-electrolyte interface film is completed.

[0052] Example 6

[0053] Compared with Example 1, the difference in this example is that during the power-on operation, the state of charge of the battery is adjusted to 10% SOC, and then the double-pulse excitation is continued (the double-pulse excitation parameters remain unchanged), the battery is charged to 80% SOC state, and then discharged to 15% SOC state. The construction of the electrode-electrolyte interface film is completed.

[0054] Comparative Example 1

[0055] In this comparative example, the lithium-ion battery is a 18650 cylindrical lithium-ion battery. The battery is subjected to a traditional pre-charge aging process, constantly charged at a current of 0.5C to 4.2V at 60 °C, then constantly voltage-charged at 4.2V until the cut-off current is 0.01C, and then discharged at a current of 1C until the battery is empty. The construction of the electrode-electrolyte interface film is completed.

[0056] Comparative Example 2

[0057] In this comparative example, the lithium-ion battery is a 2614891 square lithium-ion battery. The battery is subjected to a traditional pre-charge aging process, constantly charged at a current of 0.5C to 4.2V at 60 °C, then constantly voltage-charged at 4.2V until the cut-off current is 0.01C, and then discharged at a current of 1C until the battery is empty. The construction of the electrode-electrolyte interface film is completed.

[0058] Comparative Example 3

[0059] In this comparative example, the lithium-ion battery is a 2014891 soft-pack lithium-ion battery. The battery is subjected to a traditional pre-charge aging process, constantly charged at a current of 0.5C to 4.2V at 60 °C, then constantly voltage-charged at 4.2V until the cut-off current is 0.01C, and then discharged at a current of 1C until the battery is empty. The construction of the electrode-electrolyte interface film is completed.

[0060] 2. Testing of the electrode-electrolyte interface film.

[0061] The porosity of the electrode-electrolyte interface films constructed in Examples 1-6 and Comparative Examples 1-3 was measured; the uniformity of the interface films was observed. The test results are shown in Table 1.

[0062] Table 1

[0063]

[0064] 3. Performance test of lithium-ion batteries.

[0065] The lithium-ion batteries in Examples 1-6 and Comparative Examples 1-3 were subjected to a cycle performance test. The lithium-ion batteries were cycled 100 times at a current of 0.5C. The cycle test results are as shown in the appendix Figure 3 as follows.

[0066] 4. Analysis of test results.

[0067] As can be seen from Table 1, compared with the traditional pre-charge aging process, the interfacial film constructed in the present invention has a higher porosity and a uniform thickness. From the results of Examples 1, 4, 5, and 6, it can be seen that during the double-pulse excitation process in the present invention, when the battery is charged to full charge and then discharged to empty charge, the obtained interfacial film has a higher porosity. The higher porosity can improve the adsorption capacity of the electrolyte interfacial film, increase its liquid absorption rate and wettability to the electrolyte, make it fully contact with the electrolyte, and improve the electrochemical performance of the battery.

[0068] As can be seen from the appendix Figure 3 By comparing Examples 1, 4, 6, and Comparative Example 1, for the same lithium-ion battery, after constructing the interfacial film by the method in the present invention, the cycle performance of the battery is improved. By comparing Example 1 with Examples 4, 5, and 6, it further shows that during the double-pulse excitation process in the present invention, the charge-discharge excitation of charging the battery to full charge and then discharging it to empty charge is most beneficial to improving the comprehensive performance of the lithium-ion battery.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the embodiments of the present invention can still be modified or equivalently replaced, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation, characterized in that, It includes the following steps: S01, under set conditions, perform double-pulse excitation on the lithium-ion battery to adjust the state of charge of the lithium-ion battery; S02, adjust the parameters of the double-pulse excitation according to the state of charge; S03, repeat S01~S02 to construct the electrolyte interface film of the lithium-ion battery; The set conditions include setting temperature parameters, magnetic field parameters, electromagnetic wave parameters, and particle flow parameters; The temperature is -50 to 1200 °C; the magnetic field strength is 0.01 - 1000 T; the specific parameters of the electromagnetic wave are as follows: the wavelength is 10 -10 ~10 12 m, the intensity is 0.01 - 10 15 W / m 2 ; the specific parameters of the particle flow are as follows: the wavelength is 10 -20 ~10 -10 m, the intensity is 0.01 - 10 15 W / m 2 .

2. The method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation according to claim 1, characterized in that: The lithium-ion battery is a commercial lithium-ion battery or a solid-state lithium-ion battery.

3. The method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation according to claim 1, characterized in that: The lithium-ion battery is a cylindrical lithium-ion battery, a soft-pack lithium-ion battery, or a square lithium-ion battery.

4. The method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation according to claim 1, characterized in that: The lithium-ion battery is a lithium-ion battery after adding the electrolyte and standing; the standing time is 1-30 h.

5. The method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation according to claim 1, characterized in that: The waveform of the double-pulse excitation is one or several of sine, circle, square, triangle, exponential, and logarithmic.

6. The method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation according to claim 1, characterized in that: In S03, repeat S01~S02, adjust the lithium-ion battery to a fully charged state, and then adjust it to an empty charged state.

7. The method for constructing an electrolyte interface film of a lithium-ion battery by dual-pulse excitation according to claim 1, characterized in that: The morphology of the electrode electrolyte interface film of the electrolyte interface is one or several of linear, tubular, sheet-like, spherical, or porous.

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