Non-aqueous electrolyte and lithium ion battery

Abstract

The invention provides a non-aqueous electrolyte and a lithium ion battery, the non-aqueous electrolyte comprises a first additive, the first additive is connected with two S = O bonds and two S-O bonds on the same sulfur atom, the formation of a thin (less than 5nm) and compact SEI film is facilitated, the interface impedance is obviously reduced, the lithium ion de-intercalation efficiency under high rate is improved, and the fast charge performance is effectively improved; moreover, the first additive is connected with an S-O bond through a-CH2-CH2-group to form a multi-element ring, and the molecule of the ring structure has certain flexibility, and can cover the active site of the negative electrode active material and inhibit the stripping of the negative electrode active material caused by solvent co-intercalation in the reduction process, so that the stability of the negative electrode is enhanced, and the service life of the negative electrode is prolonged. The high-temperature resistance of the battery is effectively improved, and the cycle life of the battery is remarkably prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a non-aqueous electrolyte and a lithium ion battery. BACKGROUND

[0002] With the development of new energy vehicles, wearable and portable mobile devices, the comprehensive performance requirements of lithium ion batteries are continuously improved, and people expect to develop lithium ion batteries with excellent comprehensive performance to meet people's daily needs.

[0003] At present, the commercial electrolyte mainly includes carbonate organic solvents, lithium hexafluorophosphate salt and additives, wherein the carbonate organic solvents are composed of chain carbonates or cyclic carbonates. Such electrolyte has high ion conductivity characteristics, which can ensure excellent battery performance.

[0004] However, for high voltage (>4.3V) batteries, due to the effect of voltage, the above-mentioned commercial electrolyte is easy to decompose, thereby affecting the battery performance. SUMMARY

[0005] The embodiments of the present application provide a non-aqueous electrolyte and a lithium ion battery, aiming to improve the stability of the non-aqueous electrolyte, so that it is suitable for use in high voltage batteries.

[0006] In order to achieve the above-mentioned purpose, in a first aspect, the embodiments of the present application provide a non-aqueous electrolyte, the non-aqueous electrolyte comprising a first additive;

[0007] The first additive has a general formula as shown in formula I:

[0008]

[0009] wherein,

[0010] n is independently selected from 4 to 6;

[0011] x is independently selected from 1 to 2.

[0012] Optionally, in some embodiments of the present application, the first additive comprises at least one of a sulfate containing a five-membered ring alkenyl group and a sulfate containing a six-membered ring alkenyl group.

[0013] Optionally, in some embodiments of the present application, the sulfate containing a five-membered ring alkenyl group is selected from at least one of the following compounds:

[0014]

[0015] Optionally, in some embodiments of the present application, the sulfate containing a six-membered ring alkenyl group is selected from at least one of the following compounds:

[0016]

[0017] Optionally, in some embodiments of the present application, the mass percentage content of the first additive in the non-aqueous electrolyte ranges from 0.1% to 5%;

[0018] Preferably, the mass percentage content of the first additive in the non-aqueous electrolyte ranges from 0.3% to 2%.

[0019] Optionally, in some embodiments of the present application, the non-aqueous electrolyte further comprises a second additive;

[0020] The second additive comprises at least one of a nitrile compound, a sulfur-containing compound, and a carbonate compound;

[0021] Preferably, the nitrile compound comprises at least one of succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile;

[0022] Preferably, the sulfur-containing compound comprises at least one of 1,3-propanesultone, ethylene sulfate;

[0023] Preferably, the carbonate compound comprises at least one of fluoroethylene carbonate, vinylene carbonate.

[0024] Optionally, in some embodiments of the present application, the non-aqueous electrolyte further comprises a lithium salt, the lithium salt comprising at least one of lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate.

[0025] Optionally, in some embodiments of the present application, the non-aqueous electrolyte further comprises a non-aqueous solvent, the non-aqueous solvent comprising at least one of a carbonate, a carboxylate, and a fluoroether.

[0026] Optionally, in some embodiments of the present application, the non-aqueous electrolyte comprises the following mass percentages of components:

[0027] The lithium salt is 10% to 15%, the non-aqueous solvent is 70% to 90%, the first additive is 0.1 to 5%, and the second additive is 0.1 to 20%.

[0028] In a second aspect, embodiments of the present application provide a lithium ion battery, the lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte as described above.

[0029] Optionally, in some embodiments of the present application, the positive electrode sheet comprises a positive electrode active material, the positive electrode active material comprising lithium nickel cobalt manganese oxide; and / or

[0030] The negative electrode tab comprises a negative electrode active material, and the negative electrode active material comprises at least one of graphite, a silicon oxide compound, and a silicon carbon compound.

[0031] The non-aqueous electrolyte of the embodiment of the present application comprises a first additive, which connects two S=O bonds and two S-O bonds on the same sulfur atom. During the charging and discharging process, due to the low bond energy and high reactivity, this structure can be preferentially reduced and decomposed on the negative electrode surface to form inorganic-organic compounds such as lithium sulfate and lithium alkyl sulfate, which helps to form a thin (<5 nm) and dense SEI film. Moreover, due to the high ionic conductivity of lithium sulfate, the interfacial impedance of the electrode is significantly reduced. At the same time, the sulfur-oxygen group S=O can optimize the lithium ion solvation structure and accelerate the desolvation process, thereby significantly reducing the interfacial impedance, improving the lithium ion deintercalation efficiency under high rate, and effectively improving the fast charging performance. At the same time, the first additive is connected to the S-O bond through the-CH2-CH2-group to form a multi-ring. This ring structure molecule has a certain flexibility and can cover the active sites of the negative electrode active material during the reduction process, inhibiting the peeling of the negative electrode active material caused by solvent co-intercalation, thereby enhancing the stability of the negative electrode, effectively improving the high-temperature resistance of the battery, and significantly improving the cycle life of the battery. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described below in detail. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0033] High-nickel positive electrode materials are prone to lithium-nickel mixing at high temperatures, leading to the conversion of the layered structure to the rock salt phase, and aggravating the transition metal ions (such as Ni 2+) dissolution, these dissolved ions migrate to the negative electrode interface and will be reduced to metal dendrites, which can cause short circuit risk; at the same time, the dissolved metal ions catalyze the oxidative decomposition of the electrolyte, accelerate the generation of corrosive products such as HF, and cause irreversible consumption of the electrolyte and battery outgassing, which seriously damages the high-temperature cycling and storage performance. In addition, the lattice oxygen activity is enhanced at high temperature, which induces oxygen vacancies and structural collapse, further aggravating the side reaction with the electrolyte, leading to capacity decay. In the high-voltage (> 4.3V) environment, the degradation mechanism of high-nickel positive electrode is significantly aggravated: on the one hand, the surface forms a non-uniformly grown cubic rock salt phase restructuring layer (SRL), which leads to a local current constriction effect, making the charge transfer resistance nonlinearly increase (nearly 50 times in 48 hours), which seriously inhibits the lithium ion diffusion kinetics; on the other hand, the lattice constant (c / a) mismatch between the layered phase and the rock salt phase induces microstrain when deeply delithiated, hindering the H2-H3 phase transition reversibility, even if the bulk structure is complete, the lithium ion diffusion coefficient may still decrease by 3 orders of magnitude, and the high voltage also makes Ni 2+ The dissolution amount is nearly 75 times higher than that at 4.2V, which further catalyzes the decomposition of the electrolyte and aggravates the dendrite risk.

[0034] There are still some problems to be solved in the use of silicon-carbon negative electrodes: compared with graphite negative electrodes, silicon-carbon negative electrodes have relatively poor conductivity and higher requirements for electrolyte in improving fast charging performance; at the same time, the repeated expansion and contraction of silicon-carbon negative electrodes during lithium extraction during fast charging aggravates the pulverization of negative electrode materials, the continuous growth of the surface SEI film, and the irreversible consumption of electrolyte, leading to rapid capacity decay of the battery.

[0035] Therefore, the embodiments of the present application provide a non-aqueous electrolyte and a lithium ion battery, aiming to improve the problem of cycle life decline of the battery at high voltage.

[0036] In a first aspect, the present application provides a non-aqueous electrolyte, the non-aqueous electrolyte comprising a first additive, the first additive having a general formula as shown in Formula I:

[0037]

[0038] wherein,

[0039] n is independently selected from 4 to 6;

[0040] x is independently selected from 1 to 2.

[0041] By adopting the above scheme, the first additive connects two S=O bonds and two S-O bonds on the same sulfur atom. In the charging and discharging process, due to the low bond energy and high reactivity, the structure can be preferentially reduced and ring-opened on the negative electrode surface to form inorganic-organic compounds such as lithium sulfate and lithium alkyl sulfate during the decomposition of the conventional solvent (EC), which helps to form a relatively thin (<5 nm) and dense SEI film. Due to the high ionic conductivity of lithium sulfate, it helps to significantly reduce the interfacial impedance of the electrode; at the same time, the high electronegativity of the S=O group can reduce the HOMO energy level of the electrolyte component, preferentially oxidizing and decomposing on the positive electrode surface to form an inorganic-organic composite CEI film containing sulfur / oxygen, inhibiting lattice oxygen release and transition metal dissolution at high voltage, and blocking the continuous decomposition of the electrolyte; the sulfur-oxygen group S=O can optimize the lithium ion solvation structure and accelerate the desolvation process, thereby significantly reducing the interfacial impedance and improving the lithium ion deintercalation efficiency at high rate, effectively improving the fast charging performance.

[0042] At the same time, the first additive is connected to the S-O bond through the -CH2-CH2- group to form a polybasic ring. The molecular structure of this ring has a certain flexibility and can cover the active sites of the negative active material during the reduction process, inhibiting the severe expansion of the negative material and the pulverization caused by the co-intercalation of the solvent at high voltage (>4.3V), and cooperatively maintaining the integrity of the electrode structure, thereby enhancing the stability of the negative electrode and effectively improving the high-temperature resistance of the battery, and the cycle life of the battery is significantly improved; at the same time, the flexibility of the ring structure can relieve the stress cracks of the positive electrode particles caused by high-pressure phase transition (such as H2-H3 phase transition).

[0043] Therefore, the first additive of the embodiments of the present application can optimize the chemical properties of the electrode interface, thereby significantly improving the stability of the battery at high temperature and cycle life.

[0044] In some embodiments of the present application, the additive includes one of a sulfuric acid ester containing a five-membered ring alkenyl group and a sulfuric acid ester containing a six-membered ring alkenyl group.

[0045] By adopting the above scheme, the additive can use at least one of a sulfuric acid ester containing a five-membered ring alkenyl group or a sulfuric acid ester containing a six-membered ring alkenyl group. The bond angle of the five-membered ring is 108°, and the ideal SP 3 The bond angle of the heterocycle is 109.5°, so the ring tension of the five-membered ring is larger and is more prone to ring-opening, which helps to improve the initial cycle performance of the battery; and the bond angle of the six-membered ring is close to 109.5°, and the stability of the ring structure is better, which helps to improve the long-term stability of the battery.

[0046] In some embodiments of the present application, the sulfuric acid ester containing a five-membered ring alkenyl group is selected from at least one of the following compounds:

[0047]

[0048] By adopting the above scheme, I-1, I-2 and I-3 all belong to sulfate esters containing five-membered ring alkenyl groups, the sulfate ester groups form five-membered rings through -CH2-CH2-, the five-membered rings have certain flexibility, can cover the active sites of the negative active material in the reduction process, and inhibit the peeling of the negative active material caused by solvent co-intercalation, thereby enhancing the stability of the negative electrode and helping to significantly improve the high-temperature resistance and cycle life of the battery.

[0049] In some embodiments of the present application, the sulfate ester containing a six-membered ring alkenyl group is selected from at least one of the following compounds:

[0050]

[0051] By adopting the above scheme, I-4, I-5, I-6, I-7 and I-8 all belong to sulfate esters containing six-membered ring alkenyl groups, the sulfate ester groups form six-membered rings, six-membered ring configuration sulfate esters (bond angle close to sp 3 hybridization angle (109.5°), low ring tension, can still maintain the integrity of the molecular configuration at high temperature, avoid the rupture and recombination of the SEI film, thereby improving the high-temperature cycle stability.

[0052] In some embodiments of the present application, the mass percentage content of the additive in the non-aqueous electrolyte is in the range of 0.1% to 5%. Further, the mass percentage content of the additive in the non-aqueous electrolyte is in the range of 0.3% to 2%. Illustratively, the mass percentage content of the additive in the non-aqueous electrolyte can be 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 2% and any value between any two adjacent values in the above range.

[0053] By adopting the above scheme, the amount of the additive in the above range helps to further improve the battery to have excellent high-temperature resistance and cycle performance under high voltage.

[0054] In some embodiments of the present application, the non-aqueous electrolyte further comprises a second additive, and the second additive comprises at least one of a nitrile compound, a sulfur-containing compound and a carbonate compound.

[0055] By adopting the above scheme, the nitrile compound contains a nitrile group, which can complex lithium ions, helping to weaken the binding energy of the solvent carbonate, thereby optimizing the solvation of lithium ions; the sulfur-containing compound helps to generate LiSO4 or polysulfide in the redox process, helping to improve the toughness of the SEI film, thereby repairing the electrode interface; the carbonate compound can generate polycarbonate in the reduction process, i.e., forming a film at the negative electrode to form protection, thereby helping to inhibit solvent co-intercalation.

[0056] Exemplarily, the nitrile compound includes at least one of succinonitrile, adiponitrile, 1,3,6-hexanetristitnitrile.

[0057] Exemplarily, the sulfur-containing compound includes at least one of 1,3-propane sultone, ethylene sulfate.

[0058] Exemplarily, the carbonate compound includes at least one of fluoroethylene carbonate, vinylene carbonate.

[0059] In some embodiments of the present application, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium bisfluorosulfonylimide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), and lithium hexafluoroarsenate (LiAsF6).

[0060] By using the above-mentioned scheme, the lithium salt satisfies the above-mentioned condition, which is helpful for efficient migration and stable transmission of ions in the non-aqueous electrolyte, thereby improving the rate performance and cycle performance of the battery. In addition, it is helpful to maintain the chemical stability of the electrolyte, reduce the side reactions in the charging and discharging process, such as decomposition of the electrolyte and gas generation, which is helpful to prolong the cycle life of the battery and improve its safety.

[0061] In some embodiments of the present application, the non-aqueous electrolyte further includes a non-aqueous solvent, and the non-aqueous solvent includes at least one of a carbonate, a carboxylic acid ester, and a fluoroether.

[0062] Exemplarily, the carbonate includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0063] Exemplarily, the carboxylic acid ester includes at least one of ethyl propionate and propyl propionate.

[0064] Exemplarily, the fluoroether can be 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0065] In some embodiments of the present application, the mass percentage of the non-aqueous solvent in the total mass of the electrolyte is 70% to 90%. Exemplarily, the mass percentage of the non-aqueous solvent is 70%, 75%, 82%, 86%, 88%, 90%, and any value between any two adjacent values.

[0066] According to a second aspect of the present application, a lithium ion battery is provided, which includes a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte as described above.

[0067] By adopting the above-described scheme, the lithium-ion battery possesses all the characteristics and advantages of the aforementioned electrolyte, which will not be repeated here. In summary, it at least has the advantage of maintaining both high-temperature resistance and cycle performance under high voltage.

[0068] In some embodiments of this application, the positive electrode sheet includes a positive electrode active material, which includes lithium nickel cobalt manganese oxide.

[0069] As an example, lithium nickel cobalt manganese oxides can include those with the general formula Li a Ni b Co c M d O e D f One or more of lithium nickel cobalt manganese oxides and their modified compounds, wherein 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0070] In some embodiments of this application, the negative electrode sheet includes a negative electrode active material, which includes at least one of graphite, silicon oxide, and silicon carbide.

[0071] As an example, silicon oxides may include, but are not limited to, at least one of graphite, silicon oxide, and silicon carbon.

[0072] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0073] Example 1

[0074] A lithium-ion battery is prepared using the following method:

[0075] 1. Preparation of the positive electrode sheet:

[0076] The positive electrode active material NCM622, the conductive agent acetylene black, and the binder PVDF were added to the solvent N-methylpyrrolidone (NMP) in a mass ratio of 96.5:1.2:2.3 and stirred thoroughly to obtain a positive electrode slurry. The positive electrode slurry was coated on the upper and lower surfaces of an aluminum foil and dried before being cold-pressed. Then, the foil was trimmed, cut into sheets, and slit to form a positive electrode sheet with a thickness of 70 μm.

[0077] 2. Preparation of the negative electrode sheet:

[0078] The negative electrode active material graphite, conductive agent acetylene black, binder CMC, styrene-butadiene rubber SBR, and carbon nanotubes CNT are dispersed in deionized water at a mass percentage of 96.3:0.5:1.4:1.3:0.5 and thoroughly stirred to prepare a negative electrode slurry. The negative electrode slurry is coated on the upper and lower surfaces of a copper foil and dried. Then, it is cold-pressed, trimmed, cut, and slit to form a negative electrode sheet with a thickness of 106 μm.

[0079] 3. Preparation of non-aqueous electrolytes:

[0080] In a nitrogen-filled glove box (moisture < 0.1 ppm, oxygen < 0.1 ppm), based on the total mass of the electrolyte (100%), 25.2 wt% ethylene carbonate (EC), 42 wt% ethyl methyl carbonate (EMC) and 16.8 wt% diethyl carbonate (DEC) were mixed evenly to prepare a non-aqueous solvent. 13 wt% lithium hexafluorophosphate, 0.5 wt% compound 1.1 and a second additive (lithium difluorophosphate (LiPO2F2), vinylene carbonate (VC), lithium difluorooxalate borate (LiODFB) and ethylene sulfate (DTD)) were added to the above non-aqueous solvent to prepare the electrolyte for a lithium-ion battery.

[0081] 4. Diaphragm:

[0082] A diaphragm was made by coating a 9μm polyethylene membrane as the base membrane with a 3μm nano-alumina coating.

[0083] 5. Preparation of lithium-ion batteries:

[0084] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The cells are then wound to obtain a bare cell. The tabs are welded on, and the bare cell is placed in an outer package. The electrolyte prepared above is injected into the dried cell. The cells are then encapsulated, left to stand, formed, and shaped to complete the preparation of the lithium-ion battery.

[0085] It is understood that in the electrolyte, when the total amount of additives (the embodiments of this application include additives and second additives) changes between different embodiments, the content of solvent also changes accordingly. For example, if the total amount of additives increases by 1%, the content of solvent will decrease by 1%, but the ratio of EC, EMC and DEC in the solvent is still 3:5:2.

[0086] The preparation methods of the lithium-ion batteries in Examples 2-16 and Comparative Examples 1-2 are the same as those in Example 1, except that the composition of the additives in the electrolyte is different, as shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] Performance testing:

[0091] (1) Cyclic performance:

[0092] Lithium-ion batteries were placed in constant-temperature chambers at 25°C and 45°C respectively, and left to stand for 180 minutes to reach a constant temperature. The batteries were then charged at a constant current of 1C to a voltage of 4.45V, followed by constant-voltage charging at 4.45V to a current of 0.05C, and finally constant-current discharging at 1C to a voltage of 2.8V. This constitutes one charge-discharge cycle, which was repeated three times. The discharge capacity of the last cycle was taken as the initial capacity of the lithium-ion battery. Starting from 100% initial capacity, the charge-discharge cycles were repeated until the discharge capacity decreased to 80%. The test was then stopped, and the number of cycles was recorded as an indicator of the lithium-ion battery's cycle performance.

[0093] (2) High-temperature storage performance:

[0094] Place the lithium-ion battery in a constant temperature chamber at 25°C and let it stand for 30 minutes to allow it to reach a constant temperature. Charge it at a constant current of 1C to 4.45V, then charge it at a constant voltage to 0.05C, and then discharge it at a constant current of 1C to 2.8V. Repeat this cycle 3 times, and use the discharge capacity of the last cycle as the initial capacity of the lithium-ion battery.

[0095] The tested lithium-ion batteries were then stored in a 60°C constant-temperature chamber for 60 days. After 60 days of storage, the batteries were transferred to a 25°C constant-temperature chamber and left to stand for 60 minutes. They were then discharged at a constant current of 1C to 2.8V, and the discharge capacity was recorded as the remaining capacity of the lithium-ion battery. The batteries were then charged at a constant current of 1C to 4.45V, and then charged at a constant voltage until the current reached 0.05C. Finally, they were discharged at a constant current of 1C to 2.8V, and the discharge capacity was recorded as the recoverable capacity of the lithium-ion battery, serving as an indicator of the high-temperature storage performance of the lithium-ion battery.

[0096] The overall test results are shown in Table 2:

[0097] Table 2

[0098]

[0099]

[0100] Compared with Examples 1-11 and Comparative Examples 1-2, the non-aqueous electrolytes of Examples 1-11 used 0.5% of the first additive, Comparative Example 1 did not add the first additive, and Comparative Example 2 added the remaining sulfonate compounds. As shown in Table 1, the cycle performance and high-temperature resistance of the batteries in Examples 1-11 were significantly improved. This is because the first additive connects two S=O bonds and two SO bonds on the same sulfur atom, which helps to form a thinner (<5nm) and denser SEI film. Furthermore, the first additive forms a multi-ring structure with SO bonds through the -CH2-CH2- group. This cyclic molecular structure has a certain degree of flexibility and can cover the active sites of the negative electrode active material during reduction, inhibiting the stripping of the negative electrode active material caused by solvent co-intercalation, thereby enhancing the stability of the negative electrode, effectively improving the high-temperature resistance of the battery, and significantly increasing the cycle life of the battery. Combining the data from Examples 1-11, we can also find that, overall, the examples containing six-membered cyclic alkenyl sulfates exhibit superior high-temperature performance and more stable long-cycle performance compared to the examples containing five-membered cyclic alkenyl sulfates. This is mainly because the bond angle of the six-membered ring (approximately 109.5°) is closer to the ideal spline angle of a carbon atom. 3 Hybridization angles significantly reduce ring strain, making the structure more stable at high temperatures. In contrast, five-membered rings, due to bond angle compression (approximately 108°), exhibit higher ring strain and are prone to ring-opening or degradation under high temperatures or stress. The rigid framework of six-membered rings can block transition metal ions (such as Ni) dissolved from the positive electrode. 2+ ) and lattice oxygen radicals (·O2) - It migrates towards the negative electrode, blocking its catalytic oxidation of the electrolyte (e.g., reducing HF generation by 60%) and reducing the risk of metal dendrite formation. Simultaneously, its hydrolytic stability is higher than that of a five-membered ring, which can delay the rise in acid value during battery storage (acid value ≤10ppm) and extend cycle life.

[0101] Compared with Examples 6 and 12-16, I-5, as an electrolyte additive, showed the best effect at an addition amount of 0.8 wt% (mass percentage). At this concentration, it could exert multiple synergistic effects: preferentially reducing and decomposing on the negative electrode surface to form an inorganic-organic composite SEI film containing Li2SO4 (thickness < 5 nm), effectively reducing interfacial impedance and inhibiting graphite exfoliation or silicon negative electrode expansion caused by solvent co-intercalation; at the same time, its ortho-bisphenol hydroxyl groups accelerated the Li + The desolvation process lowers the desolvation energy barrier by approximately 25%, significantly improving fast-charging performance; furthermore, the sulfate groups can chelate transition metal ions (such as Ni) dissolved from the positive electrode. 2+This process blocks the catalytic oxidation of the electrolyte, reducing HF generation. If the amount added is insufficient (<0.8wt%), the SEI film coverage will be incomplete, exposing the negative electrode active sites and causing the electrolyte solvent (such as EC) to continuously decompose, forming a porous and thickened SEI film and exacerbating the increase in interfacial impedance and capacity decay. At the same time, due to insufficient metal ion removal capacity, transition metal migration and dendrite formation are accelerated, high-temperature cycling stability decreases, and the desolvation efficiency is only slightly improved. Conversely, excessive addition (>0.8wt%) will increase electrolyte viscosity due to excessively high additive concentration, causing a decrease in ionic conductivity of up to 30% and impairing low-temperature (-30℃) performance; excessive decomposition will produce organic lithium salts (such as alkyl lithium sulfate) and sulfides, resulting in an excessively thick SEI film and increased impedance, hindering Li+ transport; at high concentrations, catechol is prone to self-polymerization to form high-resistivity products or hydrolysis to generate acidic substances (acid value >10ppm), which corrode the electrode interface and accelerate capacity decay; in high-voltage systems (>4.3V), excessive phenolic hydroxyl groups may also be oxidized to quinones, consuming active lithium and triggering gaseous side reactions.

[0102] The non-aqueous electrolyte and lithium-ion battery provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A non-aqueous electrolyte, characterized in that, The non-aqueous electrolyte includes a first additive; The first additive comprises a compound having the structure shown in Formula I: in, n is independently selected from 4 to 6; x is selected independently from 1 to 2.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The first additive includes at least one of a sulfate ester containing a five-membered cycloalkenyl group and a sulfate ester containing a six-membered cycloalkenyl group.

3. The non-aqueous electrolyte according to claim 2, characterized in that, The sulfate containing a five-membered cyclic alkenyl group is selected from at least one of the following compounds:

4. The non-aqueous electrolyte according to claim 2, characterized in that, The sulfate containing a six-membered cycloalkenyl group is selected from at least one of the following compounds:

5. The non-aqueous electrolyte according to any one of claims 1 to 4, characterized in that, The mass percentage of the first additive in the non-aqueous electrolyte ranges from 0.1% to 5%. Preferably, the mass percentage of the first additive in the non-aqueous electrolyte ranges from 0.3% to 2%.

6. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes a second additive; The second additive includes at least one of nitrile compounds, sulfur-containing compounds, and carbonate compounds; Preferably, the nitrile compound includes at least one selected from butadionitrile, glutaronitrile, adiponitrile, heptanonitrile, octanilide, triglyceride, ethoxypentafluorophosphazene, and 1,3,6-hexanetrionitrile; Preferably, the sulfur-containing compound includes at least one of 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, and vinylene sulfate. Preferably, the carbonate compound includes at least one of fluoroethylene carbonate, vinylene carbonate, and ethylene ethylene carbonate.

7. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes lithium salts, which include at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate.

8. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes a non-aqueous solvent, which includes at least one of carbonates, carboxylic esters, and fluoroethers.

9. The non-aqueous electrolyte according to any one of claims 1 to 8, characterized in that, The non-aqueous electrolyte comprises the following components by mass percentage: Lithium salt 10%–15%, non-aqueous solvent 70%–90%, first additive 0.1%–5%, and second additive 0.1%–20%.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte as described in any one of claims 1 to 9.

11. The lithium-ion battery according to claim 10, characterized in that, The positive electrode sheet includes a positive electrode active material, which includes lithium nickel cobalt manganese oxide; and / or The negative electrode sheet includes a negative electrode active material, which includes at least one of graphite, silicon oxide, and silicon carbide.

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