A method for injecting electrolyte into a lithium ion battery and a lithium ion battery

Abstract

The present application relates to a kind of for lithium ion battery secondary injection method, the present application adopts secondary injection process path, first injection is before battery formation, electrolyte is coded as A electrolyte, after formation, free A electrolyte in battery is discharged and carries out negative pressure sealing, after formation, electrolyte is generated solid electrolyte film on the surface of negative electrode material.Secondary injection is carried out to battery, electrolyte is coded as B electrolyte, after injection, it is placed at 45 DEG C environment for more than 8h, after standing, free B electrolyte is discharged again, and secondary negative pressure sealing is carried out.Battery can form solid electrolyte film in negative pole by first injection formation, especially perfluorohexanone and C8F 13 NO2 Additive can form solid electrolyte film rich in dense LiF in negative pole.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a method for secondary electrolyte filling of lithium-ion batteries and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and low self-discharge rate, have become a crucial technology in modern energy storage and conversion. Since their commercialization in the 1990s, lithium-ion batteries have seen significant applications in consumer electronics, electric vehicles, and renewable energy storage systems. However, with increasingly stringent performance requirements, such as fast charging capability, cycle stability, and safety, the optimization of battery materials has become increasingly important. Among these, the electrolyte plays a key role in improving battery performance.

[0003] Electrolytes are an indispensable component of lithium-ion batteries, and their performance directly affects the battery's energy density, charge / discharge efficiency, and safety. Since the 1990s, the widespread application of lithium-ion batteries has driven in-depth research into electrolytes, especially in consumer electronics, electric vehicles, and renewable energy storage systems. However, with increasingly stringent battery performance requirements, traditional electrolytes face numerous challenges in terms of high-temperature stability, low-temperature performance, and safety, particularly under high voltage and high-rate conditions.

[0004] To address these issues, researchers have begun exploring novel electrolyte formulations, including solid-state electrolytes. However, these new electrolyte materials still suffer from problems such as low conductivity and poor safety. Furthermore, optimizing the chemical composition and additives of the electrolyte is a current research focus, aiming to achieve higher electrochemical performance and better environmental compatibility.

[0005] Dimethyl glycol ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4-Me-DOL), acetonitrile, and fluoroacetonitrile are important solvents for electrolytes. Due to their low viscosity and high lithium salt solubility, they are considered ideal electrolyte solvents. However, due to their strong solvation ability, they have the problem of co-intercalation with graphite, which destroys the graphite anode structure, thus preventing their application in electrolytes. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for secondary electrolyte injection into lithium-ion batteries and its application, solving the problem of co-intercalation of graphite with strong solvation solvents such as dimethyl glycol ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4-Me-DOL), acetonitrile, and fluoroacetonitrile. The primary function of the initial electrolyte injection is to form a solid electrolyte film at the battery's negative electrode. Furthermore, the initial electrolyte injection must contain perfluorohexanone and 2,2,3,3-tetrafluoro-3-[[1,1,1,2,3,3-hexafluoro-3-[(1,2,2-trifluorovinyl)oxy]propane-2-yl]oxy]propionitrile (C8F... 13 Two additives (NO2) can form a lithium fluoride-rich solid electrolyte membrane, which can prevent the co-intercalation of highly solvating solvents with graphite. The secondary electrolyte contains highly solvating solvents, whose main function is to provide the battery with a high-conductivity electrolyte, improve the battery's power performance, and also improve the battery's low-temperature performance.

[0007] This invention employs a two-stage electrolyte injection process. The first injection occurs before battery formation, and the electrolyte is designated as electrolyte A. After formation, the free electrolyte A is drained from the battery, and a negative pressure seal is performed. Following formation, a solid electrolyte film forms on the surface of the negative electrode material. The battery then undergoes a second electrolyte injection, designated as electrolyte B. After injection, the battery is allowed to stand at 45°C for at least 8 hours. After standing, the free electrolyte B is drained again, and a second negative pressure seal is performed.

[0008] The electrolyte A consists of three parts: a solvent, a lithium salt, and a first additive. The solvent comprises one or more of carbonate solvents or carboxylic acid ester solvents; the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; the carboxylic acid ester solvent includes one or more of methyl acetate, ethyl acetate, methyl butyrate, ethyl butyrate, and methyl propionate. The lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorooxalato)borate, and lithium bis(fluorosulfonyl)imide, preferably lithium hexafluorophosphate; the first additive must be perfluorohexanone and / or 2,2,3,3-tetrafluoro-3-[[1,1,1,2,3,3-hexafluoro-3-[(1,2,2-trifluorovinyl)oxy]propane-2-yl]oxy]propionitrile (C8F 13 The first additive may contain one or two of the following: NO2, wherein the first additive accounts for 0.1%-5% of electrolyte A by weight, preferably 1.5%-2%. Furthermore, the first additive may also contain one or more of the following: ethylene sulfate, 1,3-propanesulfonate lactone, lithium difluorophosphate, vinylene carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate.

[0009] The electrolyte B consists of two parts: a solvent and a lithium salt. The solvent must contain one or more of the following: dimethyl glycol ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4-Me-DOL), acetonitrile, and fluoroacetonitrile. The solvent may also contain one or more of the following: carbonate solvents or carboxylic acid ester solvents. The carbonate solvents include one or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The carboxylic acid ester solvents include one or more of the following: methyl acetate, ethyl acetate, methyl butyrate, ethyl butyrate, and methyl propionate. The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate)borate, and lithium bis(fluorosulfonyl)imide, preferably lithium hexafluorophosphate.

[0010] Beneficial effects: The battery of the present invention, through initial liquid injection formation, can form a solid electrolyte film at the negative electrode, especially perfluorohexanone and C8F. 13 The NO2 additive can form a dense LiF-rich solid electrolyte film at the negative electrode. This solid electrolyte film can effectively prevent the co-intercalation of lithium ions with dimethyl glycol ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4-Me-DOL), acetonitrile, and fluoroacetonitrile in the secondary electrolyte solution into the graphite during charging. Simultaneously, the small molecule compounds such as dimethyl glycol ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4-Me-DOL), acetonitrile, and fluoroacetonitrile contained in the electrolyte solvent in the secondary electrolyte solution have high dielectric constants and low viscosity. These characteristics of the solvent can increase the conductivity and reduce the viscosity of the electrolyte, thereby increasing the battery's power performance and low-temperature performance. Detailed Implementation

[0011] The specific implementation path of the invention is as follows:

[0012] 1) After preparing the unfilled battery cells, perform a first electrolyte filling. The electrolyte for the first filling is electrolyte A. In addition to solvents, lithium salts, and conventional additives, electrolyte A must also contain perfluorohexanone and C8F. 13 NO2 is used as a functional additive in perfluorohexanone and C8F. 13The NO2 content in the electrolyte is 0.1%-5% by weight, preferably 1.5%-2%, and the initial electrolyte injection coefficient is between 2.0 and 4.0, where the electrolyte injection coefficient is the weight of the injected electrolyte divided by the battery capacity.

[0013] 2) After electrolyte injection, the battery is placed in a high-temperature static environment to allow the positive and negative electrode plates and separator to be fully wetted by electrolyte A. The high-temperature static environment temperature is 30℃~50℃, preferably 35-45℃, and the static environment time is 8 hours-48 hours, preferably 12-16 hours.

[0014] 3) After being left to stand at high temperature, the battery undergoes formation (the first charge of the battery is called formation). During the formation process, a solid electrolyte film will form on the negative electrode. The ambient temperature during battery formation is 40℃~50℃, preferably 45-48℃, and the charging rate is ≤0.2C, preferably 0.1-0.15C.

[0015] 4) Drain the free electrolyte (free-flowing electrolyte that has not been adsorbed or attached to the positive and negative electrodes and the separator) from the battery after formation. At the same time, seal the battery under negative pressure. After sealing, let the battery stand at 40℃~50℃, preferably 45-48℃ for 8 hours to 24 hours, preferably 12-16 hours.

[0016] 5) The battery is refilled with electrolyte (referred to as secondary electrolyte filling), and electrolyte B is injected into the casing so that both the positive and negative electrodes separated by the separator are immersed in the injected electrolyte B. The electrolyte B consists of two parts: a solvent and a lithium salt. The solvent must contain dimethyl ethylene glycol (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), 1,3-dioxolane (DOL), and 4-methyl...

[0017] One or more of -1,3-dioxolane (4-Me-DOL), acetonitrile, and fluoroacetonitrile.

[0018] 6) After the second electrolyte injection, the battery should be left to stand at 30℃~55℃, preferably 35-45℃, for 8 hours to 48 hours, preferably 12-16 hours.

[0019] 7) Drain the free electrolyte from the battery after it has been left to stand, and then seal the battery under negative pressure to obtain the finished battery.

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] The following are specific examples.

[0022] Example 1

[0023] This embodiment uses a 5Ah lithium-ion battery to test the electrolyte performance. The 5Ah lithium-ion battery is a pouch battery. The positive electrode active material is lithium cobalt oxide (LCO), the binder is polyvinylidene fluoride (PVDF), and the conductive agent is conductive carbon black (SP). The positive electrode formulation is 95% LCO + 2% PVDF + 3% SP (by weight). The positive electrode is prepared into a positive electrode sheet through stirring, coating (coating onto 13μm aluminum foil), rolling, and die-cutting processes. The dimensions of the positive electrode sheet are width * length = 74mm * 106mm, the thickness of the prepared electrode sheet is 51μm, and the areal density is 7.2mg / cm³. 2 The main material of the battery negative electrode is graphite, the binders are styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC), and the conductive agent is conductive carbon black (SP). The negative electrode formulation is 95% graphite + 1% CMC + 2% SBR + 2% SP (by weight). The negative electrode is prepared into a negative electrode sheet through stirring, coating (coating onto a 6μm copper foil), rolling, and die-cutting processes. The prepared electrode sheet has a thickness of 97μm and an areal density of 4.68mg / cm³. 2 The negative electrode sheet measures 776mm x 108mm (width x length). The battery has 27 positive electrode layers and 28 negative electrode layers. The battery separator is a 12μm PE separator with a width of 89mm. The positive and negative electrodes are alternately stacked and arranged through the separator, and placed within the space enclosed by the battery casing, which is made of aluminum-plastic film. This constitutes the battery to be filled with electrolyte (i.e., the cell without electrolyte filling).

[0024] Electrolyte A is prepared, and the electrolytes are divided into six groups: A1, A2, A3, A4, A5, and A6. The solvents for electrolytes A1, A2, A3, A4, A5, and A6 are ethylene carbonate (EC) and ethyl methyl carbonate (EMC), with EC accounting for 30% of the solvent by weight and EMC accounting for 70% by weight. The lithium salt is 1 mol / L lithium hexafluorophosphate. Additives for electrolytes A1, A2, A3, A4, A5, and A6 include vinylene carbonate (VC) and fluoroethylene carbonate (FEC), with VC and FEC each accounting for 2% of the total weight of the electrolyte. Electrolyte A1 also includes perfluorohexanone additive, accounting for 2% of the total weight of the electrolyte. Electrolyte A2 also contains C8F... 13 NO2, the C8F 13 NO2 accounts for 2% of the total weight of the electrolyte, and the A3 electrolyte additive also contains perfluorohexanone and C8F. 13 NO2 additives, including perfluorohexanone and C8F 13 NO2 accounts for 2% of the total weight of the electrolyte. A4 does not contain perfluorohexanone or C8F. 13 NO2, A5 electrolyte additive is 2% hexanone + 2% C8F 13The electrolyte additives for NO2 and A6 are 2% perfluorohexanone and 2% 2-perfluoropropoxyperfluoropropyltrifluorovinyl ether. The specific electrolyte parameters are shown in Table 1.

[0025] Table 1

[0026]

[0027] Prepare electrolyte B, using ethylene glycol dimethyl ether as the solvent and 1 mol / L lithium hexafluorophosphate as the lithium salt. Specific electrolyte formulation parameters are shown in Table 2.

[0028] Table 2

[0029] serial number solvent lithium salts Electrolyte B Ethylene glycol dimethyl ether 1 mol / L lithium hexafluorophosphate

[0030] Finished batteries were prepared using the aforementioned batteries and electrolytes, and were divided into seven groups: a1, b1, c1, d1, e1, f1, and g1. First, 15g (filling coefficient 3.0) of electrolytes A1, A2, A3, A4, A3, A5, and A6 were injected into each of the seven groups of batteries. After filling, the batteries underwent a settling process (45℃, 12h), formation (charging rate 0.1C, temperature 45℃, charging cut-off voltage 3.9V), discharge of free electrolytes A1, A2, A3, A4, A3, A5, and A6, and sealing under negative pressure (-98kPa). Except for battery e1, batteries a1, b1, c1, d1, f1, and g1, after being sealed, were left to stand at 45°C for 24 hours. After standing, the seals were opened, and 10g (injection coefficient 2.0) of electrolyte B was injected into each battery. The batteries were then left to stand at 45°C for 12 hours to drain the free electrolyte B. After sealing again under negative pressure (-98kPa), the batteries were made into finished batteries a1, b1, c1, d1, f1, and g1. The battery capacity retention rates at 20C discharge rate (100A) and at -30°C, 5C discharge rate were tested at room temperature (25°C). The test results are shown in Table 3.

[0031] Table 3

[0032]

[0033] As shown in Table 3, group C1 exhibits the highest 20C discharge capacity retention rate and the highest 5C discharge capacity retention rate at -30℃. Compared to group C1, group E1 batteries have not undergone secondary electrolyte filling and do not contain ethylene glycol dimethyl ether solvent. Therefore, their electrolyte lacks the characteristics of low viscosity and high conductivity, resulting in poor rate performance and low-temperature performance. Compared to group C1, group D1 electrolyte does not contain 2% perfluorohexanone or 2% C8F. 13With both NO2 additives, the d1 group of batteries failed to form a denser solid electrolyte film on the negative electrode surface, resulting in a reduced battery capacity retention. Compared to the c1 group, the a1 and b1 groups contain only one strong film-forming additive, and their film-forming effect is not as good as the synergistic effect of the two additives. Therefore, the rate capability and low-temperature performance of the a1 and b1 groups are inferior to those of the c1 group. Compared to the c1 group, the f1 group uses non-fluorinated hexanone and C8F as the initial electrolyte additives. 13 With NO2, the discharge capacity retention rate of group F1 at both room temperature and low temperature was lower than that of group C1, mainly because perfluorohexanone and C8F... 13 NO2 can form a dense solid electrolyte film on the electrode surface, effectively preventing electrolyte from embedding into the electrode layer during secondary electrolyte injection. Similarly, the low-temperature and room-temperature performance of the C1 group battery is better than that of the G1 group, indicating that only perfluorohexanone and C8F... 13 When combined with NO2, the battery achieves optimal performance.

[0034] Example 2

[0035] This embodiment uses the same battery as in Example 1, and the battery preparation process and conditions are the same as in Example 1. Perfluorohexanone and C8F were tested. 13 The effect of NO2 functional additive weight content on battery performance. The electrolyte is divided into eight groups: A7, A8, A9, A10, A11, A12, A13, and A14. The specific electrolyte formulation parameters are shown in Table 4.

[0036] Table 4

[0037]

[0038] Prepare electrolyte B, using ethylene glycol dimethyl ether as the solvent and 1 mol / L lithium hexafluorophosphate as the lithium salt. The electrolyte formulation parameters are shown in Table 5.

[0039] Table 5

[0040] serial number solvent lithium salts Electrolyte B Ethylene glycol dimethyl ether 1 mol / L lithium hexafluorophosphate

[0041] Finished batteries were prepared using the above-mentioned batteries to be injected with electrolyte and electrolytes, and were divided into eight groups: a2, b2, c2, d2, e2, f2, g2, and h2. The batteries to be injected with electrolytes in the eight groups a2, b2, c2, d2, e2, f2, g2, and h2 were injected with 15g of electrolytes of type 7, A8, A9, A10, A11, A12, A13, and A14 respectively (injection coefficient 3.0). After injection, the batteries were subjected to a settling process (45°C, 12 hours), formation process (charge rate 0.1C, temperature 45°C, charging cut-off voltage 3.9V), discharge of free electrolytes of type 7, A8, A9, A10, A11, A12, A13, and A14 respectively, and sealing process under negative pressure (-98kPa). After sealing, the battery was left to stand at 45℃ for 24 hours. After standing, 10g of electrolyte B (filling coefficient 2.0) was added, and the battery was left to stand at 45℃ for 12 hours. The free electrolyte B was then drained, and the battery was sealed under negative pressure (-98kPa) to produce a finished battery. The discharge capacity retention rate of the battery was tested at room temperature (25℃) at a discharge rate of 20C (100A), and at -30℃ at a discharge rate of 5C. The test results are shown in Table 6.

[0042] Table 6

[0043]

[0044] As shown in Table 6, the additives perfluorohexanone and C8F in electrolyte A of group e2 are... 13 All samples contain 2% NO2 and exhibit optimal 20C discharge capacity retention and low-temperature discharge capacity retention. The f2 group contains perfluorohexanone and C8F... 13 The NO2 content was 3%, and the additives in group b2 were perfluorohexanone and C8F. 13 The NO2 content was 5%, and the additives in group h2 were perfluorohexanone and C8F. 13 With NO2 content of 7%, comparisons of e2, f2, b2, and h2 revealed that when the additive content exceeded 2%, the battery's 20C discharge capacity retention and low-temperature capacity retention gradually decreased with increasing additive content. Therefore, the optimal upper limit for the additive content is 2%. Simultaneously comparing g2, a2, c2, and d2 groups with additive contents of 0.05%, 0.1%, 1%, and 1.5%, respectively, the battery's 20C discharge capacity retention and low-temperature capacity retention gradually increased with increasing additive content. When the additive content reached 1.5%, the battery's 20C discharge capacity retention and low-temperature capacity retention were comparable to those achieved with an additive content of 2%. Therefore, the optimal addition amount in electrolyte A is 1.5%–2%.

[0045] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for injecting electrolyte into a lithium-ion battery, the lithium-ion battery comprising a positive electrode and a negative electrode separated by a separator, wherein the negative electrode uses graphite as the active material, characterized in that: 1) Single electrolyte injection: After the positive and negative electrodes separated by the diaphragm are placed inside the shell, electrolyte A is injected into the shell so that both the positive and negative electrodes separated by the diaphragm are in the injected electrolyte A. Electrolyte A comprises a solvent, a lithium salt, and a first additive; the first additive is perfluorohexanone and / or 2,2,3,3-tetrafluoro-3-[[1,1,1,2,3,3-hexafluoro-3-[(1,2,2-trifluorovinyl)oxy]propane-2-yl]oxy]propionitrile (C8F) 13 One or two of NO2); 2) After electrolyte injection, the battery is subjected to high-temperature standing. The high-temperature standing temperature is 30℃~50℃, preferably 35-45℃, and the standing time is 8 hours~48 hours, preferably 12-16 hours. 3) After being left to stand at high temperature, the battery is formed. The ambient temperature during battery formation is 40℃~50℃, preferably 45-48℃, and the charging rate is ≤0.2C, preferably 0.1-0.15C. 4) Drain the free electrolyte from the battery after formation, and at the same time, seal the battery under negative pressure. After sealing, let the battery stand at 40℃~50℃, preferably 45-48℃, for 8 hours to 24 hours, preferably 12-16 hours. 5) Secondary electrolyte injection: The battery is injected with electrolyte again, and B electrolyte is injected into the casing so that both the positive and negative electrodes separated by the separator are in the injected B electrolyte. The electrolyte B consists of two parts: a solvent and a lithium salt. 6) After the second electrolyte injection, the battery is placed in a high-temperature standing environment at a temperature of 30℃ to 55℃, preferably 35-45℃, for a time of 8 hours to 48 hours, preferably 12-16 hours. 7) Drain the free electrolyte from the battery after it has been left to stand, and then seal the battery under negative pressure to obtain the finished battery.

2. The injection method according to claim 1, characterized in that: The first additive accounts for 0.1% to 5% of the weight of electrolyte A, preferably 1.5% to 2%.

3. The injection method according to claim 1, characterized in that: The injection coefficient for a single injection is between 2.0 and 4.

0.

4. The injection method according to claim 1, 2, or 3, characterized in that: In electrolyte A, the solvent comprises one or more of carbonate solvents or carboxylic acid ester solvents; The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; the carboxylic acid ester solvents include one or more of methyl acetate, ethyl acetate, methyl butyrate, ethyl butyrate, and methyl propionate. In electrolyte A, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate)borate, and lithium bis(fluorosulfonyl)imide, preferably lithium hexafluorophosphate; its concentration range is 0.8 mol / L to 1.5 mol / L, preferably 1-1.2 mol / L.

5. The injection method according to any one of claims 1-4, characterized in that: The electrolyte A further contains a second additive, which is one or more of the following: ethylene sulfate, 1,3-propanesulfonate lactone, lithium difluorophosphate, vinylene carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate; the second additive accounts for 0.1% to 5% of the weight of the electrolyte, preferably 0.5% to 3%.

6. The injection method according to claim 1, characterized in that: The solvent in electrolyte B includes one or more of the following: ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, acetonitrile, and fluoroacetonitrile.

7. The injection method according to claim 6, characterized in that: The solvent in electrolyte B may or may not contain one or more of carbonate solvents or carboxylic acid ester solvents as a second solvent. The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The carboxylic acid ester solvents include one or more of methyl acetate, ethyl acetate, methyl butyrate, ethyl butyrate, and methyl propionate. The second solvent accounts for 0% to 10% of the total weight of electrolyte B, preferably 0-3%. In electrolyte B, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate)borate, and lithium bis(fluorosulfonyl)imide, preferably lithium hexafluorophosphate, with a concentration range of 0.8 mol / L to 1.5 mol / L, preferably 1-1.2 mol / L.

8. The injection method according to claim 1 or 6, characterized in that: The injection coefficient for secondary injection is between 2.0 and 4.

0.

9. A lithium-ion battery obtained by the liquid injection method according to any one of claims 1-8.

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