An additive for positive electrolyte, electrolyte containing the same and application
By using nitrites or nitroso compounds as additives in lithium-ion batteries to generate a LiNxOy interfacial film on the positive electrode surface, the problem of oxidative decomposition of high-nickel electrolytes is solved, and the high-rate performance and cycle stability of the battery are improved.
Patent Information
- Application Number
- CN202211349000.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-31
- Publication Date
- 2026-01-16
- Estimated Expiration
- 2042-10-31
AI Technical Summary
In existing lithium-ion batteries, the oxidative decomposition of electrolytes containing high-nickel materials leads to the dissolution of transition metals and an increase in the impedance of both positive and negative electrodes, affecting battery performance. Existing film-forming additives cannot effectively construct low-impedance solid electrolyte membranes.
Using nitrites or nitroso compounds as additives in the positive electrode electrolyte generates a dense LiNxOy interfacial film on the positive electrode surface, thereby improving the lithium-ion conduction rate and reducing impedance.
The formed LiNxOy film improves the rate performance and cycle stability of lithium-ion batteries, and enhances the charge-discharge cycle performance and lifespan of the batteries.
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Figure CN115632164B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of secondary batteries, and more particularly to an additive for positive electrode electrolyte, an electrolyte containing the same and application. BACKGROUND
[0002] At present, lithium ion batteries are widely used in portable electronic devices, electric vehicles and other fields. However, there is an urgent need for high-rate performance and high energy density of power batteries in various fields. In order to meet the increasing demand for high energy density and high rate, using high nickel materials such as nickel cobalt manganese or nickel cobalt aluminum is an effective means to improve the energy density of the battery.
[0003] However, with the increase of nickel content, the oxidative decomposition of electrolyte hinders the further application of high nickel materials, and the oxidative decomposition products of electrolyte will lead to problems such as transition metal dissolution and positive and negative electrode impedance increase, resulting in deterioration of battery performance.
[0004] In order to solve the above problems, a solid-state electrolyte film can be generated on the surface of the positive and negative electrodes by adding a film-forming additive to protect the material and inhibit solvent decomposition, thereby solving the problems caused by electrolyte decomposition. However, the solid-state electrolyte film formed by the organic film-forming additive has too high impedance to affect the cycle performance and rate performance of the lithium ion battery, and the inorganic salt component in the solid-state electrolyte needs to be increased to reduce the impedance and improve the performance.
[0005] Although the existing patent CN114927828A uses a slow-release nitrate method to construct a low-impedance solid-state electrolyte film, and the patent CN115051029A uses an ether solvent to dissolve the nitrate to construct a low-impedance solid-state electrolyte film, but lithium nitrate has high oxidative stability and is less decomposed at the positive electrode, which cannot effectively construct a good CEI film. SUMMARY
[0006] Therefore, the first technical purpose of the present application is to provide an additive for positive electrode electrolyte, which is a nitrite or nitroso compound. Nitrite and nitroso are easy to oxidize to form LiNO3, which can effectively form a dense, high ionic conductivity and low impedance interface film on the surface of the positive electrode, thereby improving the rate performance and cycle stability of the battery. x O y , a dense, high ionic conductivity and low impedance interface film is generated on the surface of the positive electrode, thereby improving the rate performance and cycle stability of the battery.
[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:
[0008] An additive for positive electrode electrolyte, the additive is a nitrite or nitroso compound; wherein,
[0009] The general formula of the nitroso compound is R-N=O, which is a kind of organic compound containing a nitroso (-NO) functional group;
[0010] The nitrite has a general formula of M-NO2, and the cation M is an inorganic salt of a metal cation and a non-metal cation.
[0011] Optionally, the nitrite is one or a mixture of lithium nitrite, sodium nitrite, iron nitrite, ferrous nitrite, magnesium nitrite, calcium nitrite, aluminum nitrite, zinc nitrite, copper nitrite, silver nitrite, tin nitrite, and ammonium nitrite.
[0012] The nitro organic compound is one or a mixture of nitramide, 3-nitrophenylboronic acid L-tartrate, sodium p-nitrophenol, 3-(2-methoxy-3-nitrophenyl)-1H-1,2,4-triazole, potassium tetranitroplatinate, nitrosobenzene, nitrosodiisopropylamine, and 4-nitro-3-pyridine carboxaldehyde 1-oxide.
[0013] A second technical purpose of the present application is to provide a positive electrode electrolyte for a lithium battery.
[0014] A positive electrode electrolyte for a lithium battery comprises an electrolyte lithium salt, an organic solvent, and an additive, the organic solvent is a carbonate solvent, and the additive is the additive described above, specifically a nitrite or a nitro compound.
[0015] Optionally, the electrolyte lithium salt is one or a mixture of lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide.
[0016] Optionally, the carbonate solvent is one or a mixture of cyclic ester vinyl carbonate, propylene carbonate, fluorinated vinyl carbonate, and linear ester dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.
[0017] Optionally, the molar concentration of the electrolyte lithium salt in the electrolyte is 1-3 mol / L, and the mass fraction of the additive in the electrolyte is 0.001wt%-10wt%.
[0018] A third technical purpose of the present application is to provide the use of the positive electrode electrolyte described above in a lithium ion battery or a lithium metal battery.
[0019] Specifically, it further comprises a positive electrode, a spring, a gasket, a separator, and a negative electrode.
[0020] The material of the positive electrode is lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium cobaltate, or lithium nickelate.
[0021] The material of the negative electrode is natural graphite, artificial graphite, alloy-based negative electrode material, silicon monoxide negative electrode material, silicon-carbon material, or silicon monoxide / carbon material.
[0022] The diaphragm is a single-layer polypropylene diaphragm.
[0023] Compared with the prior art, the positive electrolyte additive, the electrolyte containing the same and the application thereof provided by the present application have the following beneficial effects:
[0024] (1) When the electrolyte containing the electrolyte additive of the present application is formed, the nitrogen contained in the additive is in +3 valence, which is more prone to oxidative decomposition, and can be oxidatively decomposed at about 3.5V to form a CEI film containing LiN x O y on the surface of the positive electrode, which has a fast lithium ion conduction rate, low impedance, thinness and stability, improves the charge-discharge cycle performance of the battery and prolongs the service life;
[0025] (2) The battery electrolyte of the present application is compatible with the current lithium ion battery process technology, and can greatly improve the rate performance and cycle stability of the current single-crystal high-nickel ternary material, and has commercialization potential. BRIEF DESCRIPTION OF DRAWINGS
[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.
[0027] Figure 1 The cycle performance curves of the single-crystal high-nickel ternary half-batteries prepared by the experimental group and the control group electrolyte of Example 1.
[0028] Figure 2 The rate performance curves of the single-crystal high-nickel ternary half-batteries prepared by the experimental group and the control group electrolyte of Example 1.
[0029] Figure 3 The performance curves of the ternary batteries prepared by the experimental group and the control group electrolyte of Example 2.
[0030] Figure 4 The cycle performance curves of the ternary batteries prepared by Example 3.
[0031] Figure 5 The cycle performance curves of the ternary batteries prepared by Example 4.
[0032] Figure 6 The cycle performance curves of the ternary batteries prepared by Example 5.
[0033] Figure 7Cycle performance curves of the ternary battery prepared in Example 6. DETAILED DESCRIPTION
[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.
[0035] The electrolyte prepared by the present application can react on the surface of the positive electrode to generate a layer of lithium-nitrogen oxide-rich inorganic fast-ion solid-state electrolyte protective film, accelerate the transmission of lithium ions in the solid-state electrolyte film, and further improve the rate performance and cycle stability of the lithium ion battery.
[0036] The technical solutions of the present application will be described in detail below in combination with the embodiments.
[0037] Example 1
[0038] In an argon glove box with oxygen pressure and water pressure less than 0.1 ppm, the composition of the reference electrolyte is as follows: lithium salt: 1.0 mol·L -1 lithium hexafluorophosphate; organic solvent: a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7, as a control group;
[0039] The electrolyte obtained by adding 0.1wt% of iron nitrite to the reference electrolyte is used as the experimental group;
[0040] In an argon glove box, 0.5h of heating and stirring at 40℃ until the iron nitrite is completely dissolved;
[0041] The electrolyte is used for half-cell test with metal lithium as the negative electrode and single-crystal lithium nickel cobalt manganese oxide as the positive electrode, and a single-layer polypropylene film is used as the separator. After one cycle of 0.1C (1C=200mAh / g) activation and two cycles of 0.2C activation, the electrolyte additive decomposes to form a lithium-nitrogen oxide-rich inorganic fast-ion solid-state electrolyte film, which reduces the film impedance. The reduction of the battery impedance brings a significant improvement in the rate: the specific capacity of the experimental group is increased from 185mAh / g to 192mAh / g; and the specific capacity at 5C is increased from 118mAh / g to 140mAh / g. The film can well inhibit the decomposition of the electrolyte and improve the cycle stability: the capacities of the single-crystal positive electrode after 0.5C cycle for 100 cycles are 150.5mAh / g and 94mAh / g, and the capacity retention rate is increased from 56% to 82%.
[0042] Example 2
[0043] In an argon glove box with oxygen pressure and water pressure less than 0.1 ppm, the composition of the reference electrolyte is as follows: lithium salt: 1.0 mol·L-1 LiPF6; organic solvent: mixture of ethylene carbonate and dimethyl carbonate in volume ratio of 3:7, as control group;
[0044] The electrolyte obtained by adding 0.1wt% magnesium nitrite to the benchmark electrolyte as the experimental group;
[0045] The electrolyte was prepared in an argon glove box at 40℃ under stirring for 0.5h until the magnesium nitrate was completely dissolved.
[0046] The electrolyte was used for half-cell test with lithium metal as negative electrode and single-crystal lithium nickel cobalt manganese oxide as positive electrode, with single-layer polypropylene film as separator. After three cycles of 0.1C (1C=200mAh / g) activation, the capacities of the experimental group and the control group were 188mAh / g and 193mAh / g respectively, and after 100 cycles of 0.5C, the capacities were 153.6mAh / g and 122.3mAh / g respectively, and the capacity retention rates were 84% and 66.8% respectively.
[0047] Example 3
[0048] The electrolyte was prepared in an argon glove box at 40℃ under stirring for 0.5h until the magnesium nitrate was completely dissolved. -1 LiPF6; organic solvent: mixture of ethylene carbonate and dimethyl carbonate in volume ratio of 3:7, as control group;
[0049] The electrolyte was used for half-cell test with lithium metal as negative electrode and single-crystal lithium nickel cobalt manganese oxide as positive electrode, with single-layer polypropylene film as separator. After three cycles of 0.1C (1C=200mAh / g) activation, the capacities of the experimental group and the control group were 188mAh / g and 193mAh / g respectively, and after 100 cycles of 0.5C, the capacities were 153.6mAh / g and 122.3mAh / g respectively, and the capacity retention rates were 84% and 66.8% respectively.
[0050] Example 4
[0051] The electrolyte was prepared in an argon glove box at 40℃ under stirring for 0.5h until the magnesium nitrate was completely dissolved. -1 LiPF6; organic solvent: mixture of ethylene carbonate and dimethyl carbonate in volume ratio of 3:7, as control group;
[0052] The electrolyte is used for half-cell test with metal lithium as negative electrode and single crystal lithium nickel cobalt manganese oxide as positive electrode, single layer polypropylene film as separator, 0.1C (1C=200 mAh / g) activation three times, the capacity of the experimental group and the control group is 188 mAh / g and 193 mAh / g respectively, the capacity after 0.5C cycle for 100 times is 153.6 mAh / g and 122.3 mAh / g respectively, and the capacity retention rate is 84% and 66.8% respectively.
[0053] Example 5
[0054] In an argon glove box with oxygen pressure and water pressure less than 0.1 ppm, the electrolyte is prepared with lithium salt: 1.0 mol·L -1 lithium difluorooxalate borate; organic solvent: vinyl carbonate: dimethyl carbonate: methyl ethyl carbonate = 1:1:1 (volume ratio); additive: 1wt% lithium nitrite, heated and stirred in an argon glove box at 40℃ for 0.5h until the lithium nitrite is completely dissolved.
[0055] The electrolyte is used for full-cell test with metal lithium as negative electrode and lithium nickel cobalt manganese oxide as positive electrode, single layer polypropylene film as separator, and the capacity is 207.6 mAh / g after 0.1C (1C=200 mAh / g) activation for three times, the capacity is 137.5 mAh / g after 1.0C cycle for 186 times, and the capacity retention rate is 66.2%.
[0056] Example 6
[0057] In an argon glove box with oxygen pressure and water pressure less than 0.1 ppm, the electrolyte is prepared with lithium salt: 1.0 mol·L -1 lithium difluorooxalate borate; organic solvent: vinyl carbonate: dimethyl carbonate: methyl ethyl carbonate = 1:1:1 (volume ratio); additive and 0.3wt% sodium p-nitrosophenol, heated and stirred in an argon glove box at 40℃ for 0.5h until the sodium p-nitrosophenol is completely dissolved.
[0058] The electrolyte is used for full-cell test with metal lithium as negative electrode and lithium nickel cobalt manganese oxide as positive electrode, single layer polypropylene film as separator, and the capacity is 211 mAh / g after 0.1C (1C=200 mAh / g) activation for three times, the capacity is 188.4 mAh / g after 1.0C cycle for 30 times, and the capacity retention rate is 89.2%.
[0059] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and, while certain modifications are discussed, it is desired to be protected in accordance with the spirit and scope of the application. Therefore, the application is not limited to the specific embodiments shown and described, but only by the scope of the appended claims, unless otherwise specified.
Claims
1. Use of a positive electrolyte in a lithium-ion battery or a lithium-metal battery, characterized in that, The positive electrolyte comprises an electrolyte lithium salt, an organic solvent and an additive; the organic solvent is a carbonate solvent, and the additive is nitroamide or sodium p-nitrosophenol.
2. Use according to claim 1, characterized in that, The molar concentration of the electrolyte lithium salt in the electrolyte is 1-3 mol / L, and the mass fraction of the additive in the electrolyte is 0.001wt%-10wt%.
3. Use according to claim 1 or 2, characterized in that, The electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide.
4. Use according to claim 1 or 2, characterized in that, The carbonate solvent is at least one of cyclic ester vinyl carbonate, propylene carbonate, fluorinated vinyl carbonate and linear ester dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.
5. The use according to claim 1, characterized in that, The lithium ion battery further comprises a positive electrode, a spring, a gasket, a separator and a negative electrode. The material of the positive electrode is lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium cobaltate or lithium nickelate. The material of the negative electrode is natural graphite, artificial graphite, alloy negative electrode material, silicon monoxide negative electrode material, silicon carbon material or silicon monoxide / carbon material. The separator is a single-layer polypropylene separator.