Full-time-domain electrolytic lithium ion battery and preparation method thereof

Abstract

The invention provides a full-time-domain lithium ion battery and a preparation method thereof. The battery is characterized in that the battery comprises a positive electrode, a negative electrode, a diaphragm, an electrolyte, a tab and a packaging material, the battery is prepared in a lamination mode, the positive electrode is made of a nickel-containing ternary system positive electrode material, the negative electrode is made of a silicon-carbon composite system negative electrode material, the electrolyte comprises a solvent, an electrolyte and an additive, the solvent is a mixture of methyl ethyl carbonate, fluoro ether TTE, fluoroethylene carbonate and ethyl trimethylsilyl acetate in different proportions, the electrolyte is a lithium salt solute, and the diaphragm is a high-temperature-resistant diaphragm. Based on material component optimization and electrolyte configuration, the full-time-domain lithium ion battery with the wide-temperature characteristic is prepared, the method has the advantages of being simple in process, good in repeatability, low in cost and convenient for large-scale production, and meanwhile, the lithium ion battery provided by the method has the advantages of being high in specific energy, wide in temperature adaptability and excellent in high-temperature cycle performance.

Description

Technical Field

[0001] The present invention relates to the field of lithium ion batteries, and in particular to a full-time electrolysis lithium ion battery and a preparation method thereof. Background Art

[0002] my country has a vast territory, and the temperature has great temporal and regional differences. In winter, the surface temperature in some areas reaches below -40°C; in summer, due to the influence of solar radiation, the surface temperature in some areas can reach above 70°C. This poses severe challenges to the development of energy storage technology in scenarios such as cross-regional electric vehicles, communication base stations, rail transit, and large-scale energy storage. It is urgent to develop lithium-ion batteries that can be used at all times and in all regions (all time domains) to provide strong energy guarantees for energy storage equipment.

[0003] Due to the limitations of working principles and key materials, battery performance still faces many bottleneck problems in terms of cycle life, energy density, and safety performance under extreme temperature conditions: (1) Under low temperature conditions, the kinetics of positive and negative electrode materials are slow, the negative electrode has a serious safety hazard of lithium deposition, and the electrolyte ion conductivity decreases and the viscosity increases; (2) Under high temperature conditions, the electrode material structure is poorly stable, the interface side reactions are serious, and the SEI film on the electrolyte and negative electrode surface has serious decomposition and gas production problems. To improve the wide temperature performance of lithium-ion batteries, the influence of factors such as the positive electrode, negative electrode, and electrolyte in the battery should be comprehensively considered to meet the battery's electrical performance requirements at high and low temperatures.

[0004] The ternary silicon-carbon battery system has attracted attention due to its components, adjustable capacity and high specific energy characteristics, and is the preferred choice for energy storage batteries. However, for the ternary silicon-carbon system, there are few studies on wide-temperature adaptability batteries that can meet both high and low temperature requirements, and the wide temperature range is relatively narrow.

[0005] A Chinese invention patent document (publication number: CN110212246A) discloses a wide-temperature lithium-ion battery electrolyte and a preparation method thereof. By adopting a suitable ratio of non-aqueous organic solvent, lithium salt and film-forming functional additive, the electrolyte has a wide temperature window, good charge and discharge performance and good cycle stability. The battery containing the electrolyte can have good cycle performance at high temperature (60°C) and electrochemical performance at low temperature (-30°C).

[0006] A Chinese invention patent document (publication number: CN112331917A) discloses a wide-temperature range lithium-ion battery electrolyte and its preparation method. By optimizing the electrolyte components, matching different ester solvents, and improving the interfacial film properties, it can meet the discharge requirements within a wide temperature range of -40°C to 55°C, as well as high-temperature long-cycle performance at 55°C.

[0007] The electrolyte temperature adaptability in the above patent applications is relatively narrow and cannot meet the requirements of full-time operation of lithium-ion batteries. It is necessary to further optimize the electrolyte composition and comprehensively consider the battery system to realize a truly wide-temperature lithium-ion battery. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a full-time lithium-ion battery that can be charged and discharged at all times and in all regional climates (-50°C to 85°C).

[0009] The present invention also provides a full-time lithium-ion battery, characterized in that it comprises a positive electrode, a negative electrode, a diaphragm, an electrolyte, a tab, and a packaging material, and is prepared by a stacking method. The positive electrode adopts a nickel-containing ternary system positive electrode material, and the negative electrode adopts a silicon-carbon composite system negative electrode material. The electrolyte includes a solvent, an electrolyte, and an additive. The solvent is a mixture of ethyl methyl carbonate, fluoroether TTE, fluoroethylene carbonate, and ethyl trimethylsilyl acetate in different proportions. The electrolyte is a lithium salt solute, and the diaphragm adopts a high temperature resistant diaphragm.

[0010] Furthermore, the lithium salt solute is one or more of LiPF6, LiFSI, LiTFSI, or LiDFOB, and the additive is one or more of ethoxypentafluorocyclotriphosphazene, trimethyl phosphate, and triethyl phosphate.

[0011] Furthermore, the temperature of the entire area is -50°C to 85°C.

[0012] Furthermore, the nickel-containing ternary system positive electrode material is lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide with variable nickel content.

[0013] Furthermore, the silicon-carbon composite system negative electrode material is a silicon-graphite composite material with an adjustable ratio.

[0014] Furthermore, the diaphragm is a polyolefin porous diaphragm or a polyimide diaphragm, and the packaging material is an aluminum-plastic film.

[0015] The present invention also provides a method for preparing the above-mentioned full-time lithium-ion battery, characterized in that it comprises:

[0016] Step 1, determining the nickel content of the ternary positive electrode according to the target battery capacity, preparing the positive electrode material, and determining the composition of silicon and graphite in the negative electrode material according to the positive electrode material;

[0017] Step 2, according to the material composition determined in step 1, the positive electrode material and the negative electrode material are mixed and uniformly coated on the current collector, and then prepared into a pole piece after roller pressing and punching;

[0018] Step 3, under an argon environment, ethyl methyl carbonate, fluoroether TTE, fluoroethylene carbonate and ethyl trimethylsilyl acetate are prepared into a mixed solvent in different proportions, a lithium salt solute is dissolved in the mixed solvent, an additive is added, and the electrolyte is prepared and sealed for storage;

[0019] Step 4, using the positive electrode, negative electrode, separator, electrolyte, tab, packaging material, and other auxiliary materials as raw materials, a full-time lithium-ion battery is prepared by stacking.

[0020] Furthermore, the nickel content of the positive electrode material is 50% to 96%; and the silicon mass ratio of the negative electrode material is 6% to 90%.

[0021] Furthermore, the current collector uses aluminum foil at the positive electrode and copper foil or PET composite copper foil at the negative electrode.

[0022] Furthermore, in step 3, the volume ratio of ethyl methyl carbonate, fluoroether TTE, fluoroethylene carbonate and ethyl trimethylsilyl acetate is 1-4:1-4:1-3:1-3, the addition ratio of the lithium salt solute is 10-18wt%, and the addition ratio of the additive is 1-5wt%.

[0023] Beneficial effects of the present invention:

[0024] The present invention prepares a full-time-domain lithium-ion battery with wide-temperature characteristics based on material component optimization and electrolyte configuration. It has the advantages of simple process, good repeatability, low cost, and convenience for large-scale production. At the same time, the lithium-ion battery provided by this method has the advantages of high specific energy, wide temperature adaptability, and excellent high-temperature cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 1 of the present invention at 25° C. and -50° C.;

[0026] Figure 2 This is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 1 of the present invention at 85°C;

[0027] Figure 3 It is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 2 of the present invention at 25° C. and -50° C.;

[0028] Figure 4 It is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 2 of the present invention at 85°C. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0030] The full-time lithium-ion battery provided by the present invention can be charged and discharged at all times and in all regional climates (-50°C to 85°C), has the characteristics of high ion mobility at low temperatures and stability at high temperatures, and comprises a positive electrode, a negative electrode, a diaphragm, an electrolyte, a tab, a packaging material, etc., and is prepared by lamination of the positive electrode, the negative electrode, the diaphragm, the electrolyte, the tab, the packaging material, etc.

[0031] The positive electrode material is a ternary system, specifically, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide with variable nickel content. The negative electrode material is a silicon-carbon composite system, specifically, a silicon-graphite composite material with adjustable proportions. After the positive and negative electrodes are matched, a higher energy density can be achieved.

[0032] The electrolyte includes a solvent, an electrolyte and an additive, and has a wide temperature performance. Specifically, the solvent is a mixture of ethyl methyl carbonate, fluoroether (TTE), fluoroethylene carbonate and ethyl trimethylsilyl acetate in different proportions, the solute (electrolyte) is one or more of LiPF6, LiFSI, LiTFSI, or LiDFOB, and the additive is one or more of ethoxypentafluorocyclotriphosphazene, trimethyl phosphate and triethyl phosphate. Thus, the electrolyte is based on a low melting point, high boiling point ester solvent, introduces a halogenated functional group to reduce low temperature polarization, introduces a silicon-based functional group to inhibit high temperature decomposition, and forms an interface layer with wide temperature range adaptability.

[0033] The diaphragm adopts a high temperature resistant diaphragm, specifically a polyolefin porous diaphragm or a polyimide diaphragm.

[0034] The encapsulation layer is an aluminum-plastic film.

[0035] The battery of the present invention takes into account both high and low temperature charge and discharge capabilities by optimizing the composition of positive and negative electrode materials and adjusting the wide temperature composition of the electrolyte.

[0036] The present invention also provides a method for preparing a full-time lithium-ion battery, which is divided into the following four steps:

[0037] Step 1, determine the nickel content of the ternary positive electrode according to the target battery capacity, and prepare the positive electrode material; determine the material composition of silicon and graphite according to the positive electrode material. The nickel content in the positive electrode material is 50% to 96%. The mass proportion of silicon in the silicon and graphite material is 6% to 90%.

[0038] Step 2: According to the material composition determined in step 1, the positive electrode material and the negative electrode material are mixed and evenly coated on the current collector, and then rolled and punched to prepare a pole sheet. The current collector uses aluminum foil for the positive electrode and copper foil or PET composite copper foil for the negative electrode.

[0039] Step 3, under an argon environment, ethyl methyl carbonate, fluoroether (TTE), fluoroethylene carbonate and ethyl trimethylsilyl acetate are added to a solvent in different proportions to form a mixed solvent; one or two lithium salt solutes of LiPF6, LiFSI, LiTFSI, or LiDFOB are dissolved in a mixed solvent, and one or more of ethoxypentafluorocyclotriphosphazene, trimethyl phosphate and triethyl phosphate are added as additives to form an electrolyte sealed for storage. The volume ratio of the ethyl methyl carbonate, propyl propionate, fluoroethylene carbonate and fluoroether (TTE) is 1-4:1-4:1-3:1-2. The addition ratio of the lithium salt solute is 10 to 18wt%. The addition ratio of the additive ethoxypentafluorocyclotriphosphazene is 1 to 5wt%.

[0040] Step 4, using the positive electrode, negative electrode, separator, electrolyte, tab, packaging material, other auxiliary materials and the like as raw materials, a full-time lithium-ion battery is prepared by lamination.

[0041] Example

[0042] Example 1

[0043] Lithium nickel cobalt manganese oxide with a Ni molar content of 90% was prepared as the positive electrode material, silicon and graphite (mass fractions of 12% and 88%) were mixed as the negative electrode material, the positive and negative electrode materials were mixed and evenly coated on the current collector, and then prepared into pole pieces after roller pressing and punching.

[0044] Under an argon environment, ethyl methyl carbonate, fluoroether (TTE), fluoroethylene carbonate and ethyl trimethylsilyl acetate are added to a solvent in a volume ratio of 4:3:2:2 to prepare a mixed solvent; 16wt% of the mixed lithium salt solute in LiPF6 and LiDFOB is dissolved in the mixed solvent, and 2wt% of the additive ethoxypentafluorocyclotriphosphazene is added to prepare an electrolyte and seal it for storage.

[0045] The laminated soft-pack battery was prepared using the high-nickel positive electrode, silicon-based negative electrode, electrolyte and polyimide separator. The charge and discharge performance of the battery was tested at 85°C, 25°C and -50°C. Figure 1 It is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 1 of the present invention at 25° C. and -50° C.;

[0046] Figure 2 This is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 1 of the present invention at 85°C.

[0047] Figure 1 The charge and discharge performance of a full-time lithium-ion battery (90% Ni-12% Si) at 25°C and -50°C is shown. Figure 2The full-time lithium-ion battery (90% Ni-12% Si) charge and discharge performance at 85°C is shown. Figures 1-2 As shown, the charge and discharge retention rates at 85°C are 102.7% and 102.9%, and the charge and discharge retention rates at -50°C are 77.1% and 55.2%.

[0048] Example 2

[0049] Lithium nickel cobalt manganese oxide with a Ni molar content of 94% was prepared as the positive electrode material, silicon and graphite (mass fractions of 40% and 60%) were mixed as the negative electrode material, the positive and negative electrode materials were mixed and evenly coated on the current collector, and then prepared into pole pieces after roller pressing and punching.

[0050] Under an argon environment, ethyl methyl carbonate, fluoroether (TTE), fluoroethylene carbonate and ethyl trimethylsilyl acetate are added to a solvent in a volume ratio of 2:2:1:1 to prepare a mixed solvent; 18wt% of the mixed lithium salt solute in LiPF6 and LiDFOB is dissolved in the mixed solvent, 2wt% of trimethyl phosphate and 1wt% of the additive ethoxypentafluorocyclotriphosphazene are added as additives, and the electrolyte is prepared and sealed for storage.

[0051] The laminated soft-pack battery was prepared by using the high-nickel positive electrode, silicon-based negative electrode, electrolyte and polyolefin porous separator. The charge and discharge performance of the battery was tested at 85°C, 25°C and -50°C. Figure 3 It is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 2 of the present invention at 25° C. and -50° C.; Figure 4 It is a charge and discharge curve diagram of the full-time lithium-ion battery of Example 2 of the present invention at 85°C. Figure 3 The full-time lithium-ion battery (94% Ni-40% Si) charge and discharge performance at 25°C and -50°C is shown. Figure 4 The full-time lithium-ion battery (94% Ni-40% Si) charge and discharge performance at 85°C is shown. Figures 3-4 As shown, the charge and discharge retention rates at 85°C are 100.8% and 100.6%, and the charge and discharge retention rates at -50°C are 72.7% and 50.8%.

[0052] Example 3

[0053] Lithium nickel cobalt aluminum oxide with a Ni molar content of 85% was prepared as the positive electrode material, silicon and graphite (mass fractions of 10% and 90%) were mixed as the negative electrode material, the positive and negative electrode materials were mixed and evenly coated on the current collector, and then prepared into pole pieces after roller pressing and punching.

[0054] Under an argon environment, ethyl methyl carbonate, fluoroether (TTE), fluoroethylene carbonate and ethyl trimethylsilyl acetate are added to a solvent in a volume ratio of 4:4:3:2 to prepare a mixed solvent; 16wt% of the mixed lithium salt solute in LiPF6 and LiDFOB is dissolved in the mixed solvent, and 1wt% of the additive ethoxypentafluorocyclotriphosphazene is added to prepare an electrolyte and seal it for storage.

[0055] The laminated soft-pack battery was prepared by using the high-nickel positive electrode, silicon-based negative electrode, electrolyte and polyolefin porous separator. The charge and discharge performance of the battery was tested at 85°C, 25°C and -50°C.

[0056] Example 4

[0057] Lithium nickel cobalt aluminum oxide with a Ni molar content of 50% was prepared as the positive electrode material, silicon and graphite (mass fractions of 6% and 94%) were mixed as the negative electrode material, the positive and negative electrode materials were mixed and evenly coated on the current collector, and then prepared into pole pieces after roller pressing and punching.

[0058] Under an argon environment, ethyl methyl carbonate, fluoroether (TTE), fluoroethylene carbonate and ethyl trimethylsilyl acetate are added to a solvent in a volume ratio of 3:3:2:2 to prepare a mixed solvent; 14wt% of the mixed lithium salt solute in LiPF6 and LiDFOB is dissolved in the mixed solvent, and 2wt% of the additive ethoxypentafluorocyclotriphosphazene is added to prepare an electrolyte and seal it for storage.

[0059] The laminated soft-pack battery was prepared by using the high-nickel positive electrode, silicon-based negative electrode, electrolyte and polyolefin porous separator. The charge and discharge performance of the battery was tested at 85°C, 25°C and -50°C.

[0060] The full-time lithium-ion battery of the present invention is a square battery, which has the advantages of simple process, good repeatability, low cost and convenient large-scale production. At the same time, the present invention achieves the high and low temperature compatibility of the full-time lithium-ion battery by optimizing the composition of positive and negative electrode materials and adjusting the wide temperature electrolyte.

[0061] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A full-time lithium-ion battery, characterized in that: It comprises a positive electrode, a negative electrode, a separator, an electrolyte, a tab and a packaging material, and is prepared by lamination. The positive electrode adopts a nickel-containing ternary system positive electrode material, the negative electrode adopts a silicon-carbon composite system negative electrode material, the electrolyte comprises a solvent, an electrolyte and an additive, the solvent is a mixture of ethyl methyl carbonate, fluoroether TTE, fluoroethylene carbonate and ethyl trimethylsilyl acetate in different proportions, the electrolyte is a lithium salt solute, and the separator adopts a high temperature resistant separator.

2. The full-time lithium-ion battery according to claim 1, characterized in that: The lithium salt solute is one or more of LiPF6, LiFSI, LiTFSI, or LiDFOB, and the additive is one or more of ethoxypentafluorocyclotriphosphazene, trimethyl phosphate, and triethyl phosphate.

3. The full-time lithium-ion battery according to claim 1, characterized in that: The entire area includes temperatures ranging from -50°C to 85°C.

4. The full-time lithium-ion battery according to claim 1, characterized in that: The nickel-containing ternary system positive electrode material is lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide with variable nickel content.

5. The full-time lithium-ion battery according to claim 1, characterized in that: The silicon-carbon composite system negative electrode material is a silicon-graphite composite material with an adjustable ratio.

6. The full-time lithium-ion battery according to claim 1, characterized in that: The diaphragm is a polyolefin porous diaphragm or a polyimide diaphragm, and the packaging material is an aluminum-plastic film.

7. A method for preparing a full-time lithium-ion battery according to any one of claims 1 to 6, characterized in that: include: Step 1, determining the nickel content of the ternary positive electrode according to the target battery capacity, preparing the positive electrode material, and determining the composition of silicon and graphite in the negative electrode material according to the positive electrode material; Step 2, according to the material composition determined in step 1, the positive electrode material and the negative electrode material are mixed and uniformly coated on the current collector, and then prepared into a pole piece after roller pressing and punching; Step 3, under an argon environment, ethyl methyl carbonate, fluoroether TTE, fluoroethylene carbonate and ethyl trimethylsilyl acetate are prepared into a mixed solvent in different proportions, a lithium salt solute is dissolved in the mixed solvent, an additive is added, and the electrolyte is prepared and sealed for storage; Step 4, using the positive electrode sheet, the negative electrode sheet, the separator, the electrolyte, the tabs, the packaging materials, and other auxiliary materials as raw materials, a full-time lithium-ion battery is prepared by stacking.

8. The method for preparing a full-time lithium-ion battery according to claim 7, characterized in that: In step 1, the nickel content of the positive electrode material is 50% to 96%; the silicon mass ratio of the negative electrode material is 6% to 90%.

9. The method for preparing a full-time lithium-ion battery according to claim 7, characterized in that: The current collector adopts aluminum foil at the positive electrode and copper foil or PET composite copper foil at the negative electrode.

10. The method for preparing a full-time lithium-ion battery according to claim 7, characterized in that: In the step 3, the volume ratio of ethyl methyl carbonate, fluoroether TTE, fluoroethylene carbonate and ethyl trimethylsilyl acetate is 1-4:1-4:1-3:1-3, the addition ratio of the lithium salt solute is 10-18wt%, and the addition ratio of the additive is 1-5wt%.

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