Flame-retardant electrolyte for high-voltage battery, high-voltage battery and application

Abstract

The invention belongs to the field of metal / metal ion batteries, and particularly relates to a flame-retardant electrolyte for a high-voltage battery, the high-voltage battery and application, and the electrolyte is composed of alkali metal salt and one or more than two fluorinated sulfonamide compounds. The electrolyte for the battery has a wide electrochemical window exceeding 6.0 V, is well compatible with an alkali metal / graphite negative electrode, remarkably prolongs the cycle life of a high-voltage alkali metal and ion battery, and has higher safety performance due to excellent flame retardance and high boiling point.

Description

Technical Field

[0001] The present invention belongs to the field of metal / metal ion batteries, and particularly relates to a flame-retardant electrolyte for high-voltage batteries, a high-voltage battery and applications thereof. Background Art

[0002] Secondary alkali metal / alkali metal ion batteries have advantages such as high energy density and high voltage, and show increasingly important uses in electronic products, new energy energy storage, etc. However, due to the specific capacity limitations of conventional positive electrodes (lithium iron phosphate) and negative electrodes (graphite), the energy density has gradually reached a bottleneck, and it is necessary to solve the problem by using new high-specific-energy positive and negative electrodes. Among them, the electrolyte design for high-specific-energy batteries is particularly crucial.

[0003] In order to further improve the energy density of alkali metal batteries, the main strategies are: increasing the specific capacity of the positive electrode material, increasing the charging cut-off voltage, and using high-specific-capacity negative electrodes (such as Si negative electrodes, lithium metal negative electrodes) to replace common graphite negative electrodes. Common carbonate solvents are unstable to lithium metal, while ether solvents have poor high-voltage tolerance. Therefore, it is crucial to design new solvents that are stable to lithium metal and have high-voltage tolerance. Sulfone solvents are stable to high voltages. In order to improve the lithium metal stability of sulfone solvents and have the characteristic of being non-flammable, there are still defects such as high viscosity and instability to lithium metal. Therefore, the modification and improvement of the molecular structure of sulfone solvents are urgent.

[0004] CN119297409A discloses a preparation method of an electrolyte for a lithium ion battery. The electrolyte includes an organic solvent, a composite lithium salt and an additive. The additive is a sulfonate compound and a fluorosulfonamide compound. The sulfonate compound includes a cyclic sulfonate compound and / or a chain sulfonate compound; the organic solvent includes diethyl fluoromalonate, fluoroethylene carbonate and dimethyl carbonate. This patent uses a fluorosulfonamide compound as an additive for a lithium ion electrolyte. Among them, compound 7 is N-methyl-2(fluorosulfonyl), with a relatively large molecular weight and no ability to dissolve lithium salts. Therefore, it can only be used as an electrolyte additive, and the application field is not for high-specific-energy lithium metal batteries and cannot have a subversive impact on battery performance.

[0005] EP3050872B1 discloses a lithium ion battery using a fluorosulfonamide as a (co)solvent for an electrolyte. Among them, the 1,1,2,2,3,3,4,4,4-nonafluoro-N.N.bis(2-methoxyethyl)butane-1-sulfonamide compound contains 9 fluorine atoms and still shows a very limited solubility for lithium salts.

[0006] The fluorosulfonamides reported in the above patents have poor lithium salt solubility and cannot be used alone as the sole solvent of the electrolyte. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the present invention provides a flame-retardant electrolyte for high-voltage batteries, a high-voltage battery and its application. Compared with the fluorosulfonamide compounds reported in the prior art and applied to electrolytes, the fluorosulfonamide compounds synthesized in the present invention have different structures, high solubility in alkali metal salts, and do not require the addition of other co-solvents, thus ensuring the high safety of the electrolyte. The electrolyte prepared by using the fluorosulfonamide compound of the present invention as a high-voltage solvent has a wide electrochemical window of >6.0V. At the same time, when applied to the next-generation high specific energy lithium metal battery, the Coulomb efficiency of lithium metal deposition / dissolution exceeds 99%, far exceeding the fluorosulfonamide compounds reported in the existing patents, and having higher safety performances such as flame retardancy and high boiling point.

[0008] The technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention is to provide a flame-retardant electrolyte for high-voltage batteries, which is composed of an alkali metal salt and one or more fluorosulfonamide compounds, and the fluorosulfonamide compound is a compound shown in Formula I - Formula II:

[0010]

[0011] Among them, R1 and R2 are methyl, ethyl, n-propyl or isopropyl.

[0012] The high-voltage battery is a battery formed by forming with a high cut-off voltage of >=3.5V.

[0013] Further, the fluorosulfonamide compound is selected from the compounds shown in the following structures:

[0014]

[0015] Further, the alkali metal salt includes one or a combination of more of MFSI, MTFSI, MOTf, MBF4, MClO4, MBOB, MPF6 or MDFOB, and M represents a metal element selected from Li, Na, K. It can be selected from LiFSI, LiTFSI, LiPF6, LiOTf, LiBF4, LiClO4, LiBOB, LiDFOB, or NaFSI, NaTFSI, NaPF6, NaOTf, NaBF4, NaClO4, NaBOB, NaDFOB, or KFSI, KTFSI, KPF6, KOTf, KBF4, KClO4, KBOB, KDFOB. These are all common reagents for battery electrolytes and can be obtained through market procurement.

[0016] Further, the mass percentage content of the fluorosulfonamide compound in the flame-retardant electrolyte for high-voltage batteries is 30%-95%.

[0017] Further, for the electrolyte for alkali metal / alkali metal ion batteries, based on 1 kg, the number of moles of the alkali metal salt is 0.3-5 mol.

[0018] The present invention also provides a preparation method of the electrolyte for high-voltage batteries as described in any one of the above, which includes the following steps:

[0019] Synthesize the fluorosulfonamide compound;

[0020] Add an alkali metal salt to the synthesized fluorosulfonamide compound (single or a mixture of multiple ones), and stir until the electrolyte is completely clear to obtain the product.

[0021] Further, the synthesis method of the fluorosulfonamide compound is: react the corresponding chlorosulfonamide compound of the fluorosulfonamide compound with BiF3 under an inert atmosphere, and stir at 60-110°C for 12-24 h.

[0022] Optionally, the molar ratio of the chlorosulfonamide compound to BiF3 is 2:1.

[0023] The second aspect of the present invention is to provide a high-voltage battery that uses the electrolyte for high-voltage batteries as described in any one of the above.

[0024] Further, the high-voltage battery is an alkali metal or alkali metal ion battery.

[0025] Preferably, the alkali metal battery further includes a positive electrode, a negative electrode, a separator, and a tab.

[0026] More preferably, the active material of the positive electrode includes any one or a combination of two of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium-rich manganese-based material, lithium nickel manganate, lithium nickel cobalt manganese ternary material, sodium / potassium ion layered oxide, sodium / potassium ion polyanion compound, sodium / potassium prussian blue compound, or sodium / potassium organic material.

[0027] More preferably, the negative electrode active material includes any one or a combination of two of lithium, sodium, potassium, and carbon-based alloy materials.

[0028] More preferably, the separator includes any one of a glass fiber separator, a cellulose separator, or a porous polyolefin separator.

[0029] The third aspect of the present invention is to provide the use of the high-voltage battery in new energy vehicles, large-scale energy storage, or electronic products.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention provides an electrolyte for a high-voltage battery containing a fluorosulfonamide compound, which is used as a solvent for an alkali metal / alkali metal ion battery electrolyte, has a high solubility in alkali metal salts (≥3M), and does not require the use of other co-solvents. It effectively improves the antioxidant performance and negative electrode stability of the electrolyte. The electrolyte configured with the fluorosulfonamide compound used in the present invention can form a stable solid electrolyte interface passivation layer on the positive and negative electrodes, thereby achieving excellent cycle stability. In addition, this type of electrolyte has flame retardant properties and a high boiling point, effectively enhancing the safety performance of the battery.

[0032] (2) The present invention composes the lithium salt and the fluorosulfonamide compound in the high-voltage electrolyte for an alkali metal / alkali metal ion battery and further optimizes the concentration and ratio, which can match with a high-voltage positive electrode (such as LiNi 0.8 Co 0.1 Mn 0.1 O2) so that the overall battery has a higher energy density and is more suitable for practical applications.

[0033] (3) The high-voltage electrolyte of the present invention is used for an alkali metal / alkali metal ion battery, can be compatible with both alkali metals and graphite negative electrodes, and has broad application prospects in alkali metal / alkali metal ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a 1H nuclear magnetic resonance spectrum measured by dissolving the solvent synthesized in Example 1 in deuterated chloroform (CDCl3).

[0035] Figure 2 It is the cycle diagram of the Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 coin cell prepared with the electrolytes in Examples 1 - 3 of the electrolyte.

[0036] Figure 3 It is the charge-discharge curve of the Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 coin cell prepared with the electrolyte in Example 1 of the electrolyte.

[0037] Figure 4 It is the charge-discharge curve of the Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 coin cell prepared with the electrolyte in Example 2 of the electrolyte.

[0038] Figure 5 It is the charge-discharge curve of the Li||LiNi0.8 Co 0.1 Mn 0.1 Charge-discharge curves of the Co-Mn-O₂ coin cell.

[0039] Figure 6 Li||LiNi for the electrolyte prepared in Comparative Example 1 0.8 Co 0.1 Mn 0.1 Cycle diagram of the Co-Mn-O₂ coin cell.

[0040] Figure 7 Li||LiNi for the electrolyte prepared in Comparative Example 1 0.8 Co 0.1 Mn 0.1 Charge-discharge curves of the Co-Mn-O₂ coin cell.

[0041] Figure 8 Coulombic efficiency diagram of the Li||Cu coin cell with the electrolyte prepared in Example 1 of the electrolyte.

[0042] Figure 9 Coulombic efficiency diagram of the Li||Cu coin cell with the electrolyte prepared in Example 2 of the electrolyte.

[0043] Figure 10 Coulombic efficiency diagram of the Li||Cu coin cell with the electrolyte prepared in Example 3 of the electrolyte.

[0044] Figure 11 Coulombic efficiency diagram of the Li||Cu coin cell with the electrolyte prepared in Comparative Example 1. Detailed implementation manners

[0045] The present invention will be described below by way of some preferred embodiments in conjunction with the accompanying drawings. Those skilled in the art can obviously make modifications or appropriate combinatorial changes to the present invention without departing from the content, innovative spirit and scope of the present invention, and without paying creative labor to implement and apply the technical solution of the present invention. It should be particularly noted that all technical solutions obtained after such similar substitutions and modifications also fall within the protection scope of the present invention.

[0046] Synthesis Example 1

[0047] Under an argon atmosphere, 70 g of pyrrolidine-sulfonyl chloride and 52 g of bismuth trifluoride were reacted in a single-necked flask at 65 °C for 2 hours. Subsequently, the temperature was gradually raised to 110 °C within 3 hours, and then stirring was maintained for 12 hours. After the reaction was completed, the product was directly distilled out to obtain a crude product of pyrrolidine-sulfonyl fluoride, and then a refined product was obtained by rectification. Its structure is as shown in the following figure.

[0048]

[0049] The reaction principle of the preparation method of pyrroline-sulfuryl fluoride compounds is as follows:

[0050]

[0051] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum measured by dissolving the solvent synthesized in Example 1 in deuterated chloroform (CDCl3). It can be seen from Figure 1 that the peak positions correspond to the target product, and it has the characteristics of high purity.

[0052] Synthesis Example 2

[0053] Under an argon atmosphere, 52 g of N,N-diethyl-sulfuryl chloride and 52 g of bismuth trifluoride were reacted in a single-neck flask at 65 °C for 2 hours. Subsequently, the temperature was gradually raised to 110 °C within 3 hours, and then stirring was maintained for 12 hours. After the reaction ended, the product was directly distilled out to obtain the crude product of N,N-diethyl-sulfuryl fluoride. Immediately afterwards, the refined product was obtained by rectification, and its structure is as follows.

[0054]

[0055] Other products can be prepared by changing the precursors and using BiF3 as the fluorine source under the same reaction conditions under inert gas protection.

[0056] Electrolyte Example 1

[0057] Under an argon atmosphere, 187 mg of lithium bis(fluorosulfonyl)imide (LiFSI) and 635 mg of N,N-dimethyl-sulfuryl fluoride (solvent: LiFSI = 5, molar ratio) were taken and stirred until completely clear to obtain the electrolyte for a high-voltage battery containing a fluorinated sulfonamide compound.

[0058] Electrolyte Example 2

[0059] Under an argon atmosphere, 187 mg of lithium bis(fluorosulfonyl)imide (LiFSI) and 775 mg of N,N-diethyl-sulfuryl fluoride (solvent: LiFSI = 5, molar ratio) were taken and stirred until completely clear to obtain the electrolyte for a high-voltage battery containing a fluorinated sulfonamide compound.

[0060] Electrolyte Example 3

[0061] Under an argon atmosphere, 187 mg of lithium bis(fluorosulfonyl)imide (LiFSI) and 765 mg of pyrroline-sulfuryl fluoride (solvent: LiFSI = 5, molar ratio) were taken and stirred until completely clear to obtain the electrolyte for a high-voltage battery containing a fluorinated sulfonamide compound.

[0062] Comparative Example 1

[0063] 187 mg of lithium bis(fluorosulfonyl)imide (LiFSI) and 590 mg of diethyl carbonate were mixed and stirred until clear (solvent: LiFSI = 5, molar ratio) to obtain 1.0 mol L -1 carbonate-based electrolyte as a comparative sample.

[0064] To investigate the electrolyte performance of Examples 1-3 of the electrolyte of the present invention and Comparative Example 1, they were respectively used to prepare the same type of battery. In Examples 1-3 of the electrolyte and Comparative Example 1, Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 coin cells and the manufacturing and testing methods of Li||Cu coin half-cells are as follows:

[0065] Positive electrode sheet: LiNi 0.8 Co 0.1 Mn 0.1 O2, binder PVDF, and conductive carbon black were added in a mass ratio of 94:3:3 to N-methylpyrrolidone (NMP) and mixed evenly to obtain a slurry; then it was coated on an aluminum foil current collector and dried at 80 °C for 12 hours, and after rolling, it was cut into circular pieces with a diameter of 12 mm for use.

[0066] Li negative electrode: A thin metal lithium sheet with a diameter of 14 mm and a thickness of 50 μm was used.

[0067] Cu foil: A smooth copper foil with a diameter of 16 mm and a thickness of about 10 μm was used.

[0068] Separator: A circular polyethylene monolayer separator with a diameter of 19 mm was cut.

[0069] Al foil: An Al foil with a diameter of 19 mm was used.

[0070] Electrolyte: The electrolytes prepared in Examples 1-3 of the electrolyte and Comparative Example 1 were used respectively.

[0071] Battery assembly: In a glove box under an argon atmosphere (O2 < 0.01 ppm, H2O < 0.01 ppm), a coin-type lithium metal battery was assembled in the order of "aluminum-coated positive electrode case - 19 mm aluminum foil - separator circular piece - negative electrode circular piece - stainless steel sheet - spring piece - negative electrode case", and the electrolytes prepared in Examples 1-3 of the electrolyte and Comparative Example 1 were added respectively, and finally sealed to obtain a test battery.

[0072] Battery testing: The electrolytes in Examples 1-3 of the electrolyte and Comparative Example 1 (about 18 μL, 6 gAh -1 ) were used to assemble Li||LiNi 0.8 Co 0.1 Mn 0.1The O2 (2.8 - 4.3V) coin cell and the Li||Cu half-cell are activated at 0.1C rate for 2 cycles at room temperature (25°C), then charged at 0.1C and discharged at 0.3C for long cycles. The tested Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 cell performance data are shown in Table 1, and the performance parameters of the tested Li||Cu coin half-cell are shown in Table 2.

[0073] Table 1

[0074]

[0075]

[0076] Table 2

[0077] Electrolyte Average Coulombic efficiency (%) Electrolyte Example 1 99.75% (1 - 500 cycles) Electrolyte Example 2 99.30% (1 - 500 cycles) Electrolyte Example 3 99.21% (1 - 500 cycles) Comparative Example 1 20.52% (1 - 20 cycles)

[0078] The present invention provides the test result graphs of Examples 1 - 3 and Comparative Example 1 of the electrolyte, so as to more intuitively and clearly understand the solution of the present invention.

[0079] Figure 2 is the cycle life curve graph of the Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 cell using Examples 1 - 3 of the electrolyte, where the areal capacity of the positive electrode is 3.885 mAh cm -2 , and the negative electrode is a 50-μm-thick thin lithium. It can be Figure 2 seen that after 260 cycles, the capacity retention rate of the above electrolyte is still as high as 80%, and the average Coulombic efficiency is greater than 99%. Compared with the traditional carbonate-based electrolyte (Comparative Example 1), both the cycle capacity retention rate and the Coulombic efficiency have been greatly improved.

[0080] Figure 3 、 Figure 4 、 Figure 5 are the charge-discharge curve graphs of the Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 cell using Examples 1 - 3 of the electrolyte.

[0081] Figure 6 is the cycle life curve graph of the Li||LiNi 0.8 Co 0.1 Mn 0.1 O2 cell using Comparative Example 1 of the electrolyte, where the areal capacity of the positive electrode is 18.5 mg cm -2 (3.885 mAh cm -2), the negative electrode is a 50-μm-thick thin lithium, and after 10 cycles, the capacity retention rate is <10%.

[0082] Figure 7 For the Li||LiNi of Comparative Example 1 0.8 Co 0.1 Mn 0.1 Charge and discharge curve diagram of the O2 battery.

[0083] Figure 8 , Figure 9 , Figure 10 For the cycle life curve diagram of the Li||Cu coin-type half-cell using the electrolytes of Examples 1-3. The test conditions are 0.5 mA cm -2 , 1 mAh cm -2 . The average Coulombic efficiencies are 99.75%, 99.30%, and 99.21% respectively.

[0084] Figure 11 For the cycle life curve diagram of the Li||Cu coin-type half-cell using Comparative Example 1, the test conditions are 0.5 mA cm -2 , 1 mAh cm -2 . The average Coulombic efficiencies are 20.52% respectively.

[0085] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims

1. A flame-retardant electrolyte for high-voltage batteries, characterized in that, It consists of an alkali metal salt and one or more than two fluorosulfonamide compounds, and the fluorosulfonamide compound is a compound represented by Formula I or Formula II. Wherein, R1 and R2 are methyl, ethyl, n-propyl or isopropyl.

2. The flame-retardant electrolyte for high-voltage batteries according to claim 1, wherein, The fluorosulfonamide compound is selected from the compounds represented by the following structures:

3. The flame-retardant electrolyte for high-voltage batteries according to claim 1, characterized in that, The alkali metal salt is one or more than two of MFSI, MTFSI, MOTf, MBF4, MClO4, MBOB, MPF6 or MDFOB, and M represents Li, Na or K.

4. The flame-retardant electrolyte for high-voltage batteries according to claim 1, characterized in that, The mass percentage content of the fluorosulfonamide compound in the electrolyte is 30%-95%.

5. The electrolyte for a high-voltage battery with flame retardancy according to claim 1, wherein Each kg of the electrolyte contains 0.3-5 mol of the alkali metal salt.

6. The flame-retardant electrolyte for high-voltage batteries according to claim 1, characterized in that, The synthesis method of the fluorosulfonamide compound is: stirring the corresponding chlorosulfonamide compound of the fluorosulfonamide compound and BiF3 at 60-110 °C for 12-24 h in an inert atmosphere, and the molar ratio of the chlorosulfonamide compound to BiF3 is 2:

1.

7. A high-voltage battery, characterized in that, Use the electrolyte for high-voltage batteries described in any one of claims 1-6.

8. The high-voltage battery according to claim 7, characterized in that, The high-voltage battery is an alkali metal or ion battery, and the alkali metal battery further includes a positive electrode, a negative electrode and a separator.

9. The high-voltage battery according to claim 8, characterized in that, The active material of the positive electrode is one or more than two of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium-rich manganese-based material, lithium nickel manganate, lithium nickel cobalt manganese ternary material, sodium / potassium ion layered oxide, sodium / potassium ion polyanion compound, sodium / potassium prussian blue compound or sodium / potassium organic material; The active material of the negative electrode includes one or more than two of lithium, sodium, potassium, carbon-based alloy materials The separator is one of a glass fiber separator, a cellulose separator or a porous polyolefin separator.

10. Application of the high-voltage battery according to claim 8 or 9 in new energy vehicles, large-scale energy storage or electronic products.

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