Dry binder for rechargeable lithium batteries, electrode for rechargeable lithium batteries comprising the same, and rechargeable lithium battery comprising the same

Abstract

A dry binder for a rechargeable lithium battery, an electrode for a rechargeable lithium battery including the same, and a rechargeable lithium battery including the same are disclosed, the dry binder including a modified polytetrafluoroethylene including carbon (C), fluorine (F), and oxygen (O), wherein the modified polytetrafluoroethylene has a ratio (I OH / I CF2 ) of a peak intensity (I OH ) corresponding to OH to a peak intensity (I CF2 ) corresponding to CF2 in FT-IR spectroscopy measurement of about 0.03 to about 0.3. OH / I CF2 ).

Description

Technical Field

[0001] Embodiments of this disclosure relate to a dry binder for a rechargeable lithium battery, an electrode for a rechargeable lithium battery including the thereof, and a rechargeable lithium battery including the thereof. Background Technology

[0002] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a surprising increase in demand for rechargeable batteries with relatively high capacity and lighter weight. Accordingly, research and development to improve the performance of rechargeable lithium batteries is actively underway.

[0003] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, and an electrolyte, and generates electrical energy through oxidation and reduction reactions if (e.g., when) lithium ions are inserted into and deintercalated into / from the positive and negative electrodes. Summary of the Invention

[0004] One or more embodiments of this disclosure provide a dry binder for rechargeable lithium batteries that can improve the initial efficiency and cycle life characteristics of the battery.

[0005] Another embodiment provides an electrode for a rechargeable lithium battery that includes a dry binder.

[0006] Another embodiment provides a rechargeable lithium battery including electrodes.

[0007] One or more embodiments provide a dry binder for rechargeable lithium batteries, the dry binder comprising: a modified polytetrafluoroethylene containing carbon (C), fluorine (F), and oxygen (O) (e.g., C, F, O, and hydrogen (H)), wherein the modified polytetrafluoroethylene has a peak intensity (IL) of about 0.03 to about 0.3 corresponding to OH (e.g., -OH) in FT-IR spectroscopy measurements. OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 ).

[0008] Another embodiment provides an electrode comprising a dry binder.

[0009] Another embodiment provides a rechargeable lithium battery including electrodes and an electrolyte.

[0010] Dry binders according to one or more embodiments can provide electrodes exhibiting superior initial efficiency and cycle life characteristics, thereby providing rechargeable lithium batteries exhibiting superior electrochemical properties. Attached Figure Description

[0011] The accompanying drawings, together with the specification, illustrate embodiments of the subject matter of this disclosure, and together with the description, serve to explain the principles of embodiments of the subject matter of this disclosure.

[0012] Figures 1-4 A schematic diagram of a rechargeable lithium battery according to some embodiments is shown for illustrative purposes.

[0013] Figure 5 A photograph of the negative electrode according to Comparative Example 3.

[0014] Figure 6 A graph showing the FT-IR spectra of the dry adhesives according to Example 1 and Comparative Example 1.

[0015] Figure 7 A graph showing the FT-IR spectrum of the dry adhesive according to Example 2.

[0016] Figure 8 A graph showing the FT-IR spectrum of the dry adhesive according to Example 3.

[0017] Figure 9 A graph showing the FT-IR spectrum of the dry adhesive according to Example 4.

[0018] Figure 10 A graph showing the FT-IR spectrum of the dry adhesive according to Example 5.

[0019] Figure 11 The graphs show the FT-IR spectra of the dry adhesives according to Comparative Examples 1 to 4.

[0020] Figure 12 To illustrate the charge and discharge curves of the half-cells according to Examples 1 and 5 and Comparative Example 1.

[0021] Figure 13 The diagram shows the dQ / dV of the half-cells according to Examples 1 and 5 and Comparative Example 1 during a single charge and discharge cycle.

[0022] Figure 14 To show the charging and discharging curves of the half-cells according to Comparative Example 1 and Comparative Example 2.

[0023] Figure 15 The diagram shows the dQ / dV of the half-cells from Comparative Example 1 and Comparative Example 2 during a single charge and discharge cycle. Detailed Implementation

[0024] Embodiments of this disclosure will be described in more detail below. However, these embodiments are merely examples, and this disclosure is not limited thereto, and is defined by the appended claims and their equivalents.

[0025] As used herein, unless otherwise specified, it will be understood that when an element (such as a layer, film, region, or substrate) is referred to as being “on” another element, it may be directly on the other element or an intervening element may be present.

[0026] Unless otherwise indicated in this specification, a singular designation may also include a plural designation. In implementation, unless otherwise indicated, “A or B” may mean “including A, including B, or including both A and B”.

[0027] As used herein, “combination of” can refer to mixtures of components, laminates, complexes, copolymers, alloys, blends, reaction products, etc.

[0028] As used herein, particle size may be the average particle size if (e.g., when) no other definition is provided. In embodiments, particle size may refer to the average particle size (D). 50 The average particle size (D) refers to the diameter of particles that constitute 50% of the cumulative volume in the particle size distribution. 50 The average particle size (D) can be measured by any suitable method commonly used in the art, for example, by using a particle size analyzer and / or by using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). In an embodiment, a dynamic light scattering measurement device can be used for data analysis and can count the number of particles for each particle size range. Thus, the average particle size (D) can be easily obtained by calculation. 50 The average particle size (D) value can be measured using laser diffraction. 50 If the measurement is performed using laser diffraction methods, for example, the particles to be measured can be dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measurement device (e.g., Microtrac MT 3000), and irradiated with ultrasound at approximately 28 kHz with an output of 60 W. The average particle size (D) is then calculated based on the particle size distribution of 50% of the particles in the measurement device. 50 ).

[0029] In some example implementations, the average particle size can be measured by the various suitable methods described above, such as by a particle size analyzer.

[0030] In some example embodiments, the thickness may be measured using cross-sectional scanning electron microscopy (SEM) and / or transmission electron microscopy (TEM) images; however, this disclosure is not limited thereto, and any suitable method in the relevant art for measuring thickness may be used. The thickness may be an average thickness.

[0031] As used herein, soft carbon refers to a graphitizable carbon material that can be graphitized by heat treatment at high temperatures (e.g., 2800°C), and hard carbon refers to a non-graphitizable carbon material that cannot be graphitized by heat treatment. Soft carbon and hard carbon can be any suitable soft carbon and hard carbon commonly used in the art.

[0032] In one or more embodiments, crystalline carbon and amorphous carbon can be classified by X-ray diffraction analysis. Crystalline carbon may include natural graphite and / or artificial graphite. Natural graphite refers to naturally occurring graphite obtained from minerals through separation and has a d002 of about 3.350 Å to about 3.360 Å as determined by X-ray diffraction analysis. Artificial graphite refers to graphite produced through graphitization and has a d002 of about 3.355 Å to about 3.365 Å as determined by X-ray diffraction analysis. Amorphous carbon has a d002 of less than or equal to about 3.34 Å if (e.g., when) determined by X-ray diffraction analysis. X-ray diffraction analysis (XRD) uses CuKα rays as the target line and uses an X-ray diffractometer, such as X'Pert (manufacturer: Malvern Panalytical), and monochromatic instruments may be removed and measurements performed to improve peak intensity resolution. The measurement conditions can be 2θ = 10°~80°, scanning rate (° / s) = 0.044~0.089, and step size (° / step) = 0.013~0.039.

[0033] In one or more embodiments, active mass density refers to the density of active mass. Active mass represents a mixture comprising active material and binder, and optionally further comprising conductive material (e.g., electrically conductive material). For example, it refers to an active material layer on a current collector.

[0034] In one or more embodiments, a dry binder refers to a binder that allows the electrode to be prepared by a dry process without solvents. For example, a binder refers to a binder used in a dry electrode, which is prepared using an active material layer composition formed by mixing an active material and a dry binder, along with optionally a conductive material (e.g., an electrically conductive material), without the use of solvents.

[0035] The dry binder according to one or more embodiments comprises modified polytetrafluoroethylene containing carbon (C), fluorine (F), and oxygen (O) (e.g., C, F, O, and hydrogen (H)), and the modified polytetrafluoroethylene has a peak intensity (IL) of about 0.03 to about 0.3 corresponding to OH (e.g., -OH) in FT-IR spectroscopy measurements. OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 ).

[0036] In one or more embodiments, the peak intensity (I) corresponding to OH (e.g., -OH) OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 It can be approximately 0.05 to approximately 0.3 or approximately 0.1 to approximately 0.2.

[0037] In one or more embodiments, the modified polytetrafluoroethylene may have a peak intensity (I) corresponding to OH (e.g., -OH) within the range above. OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 ).

[0038] Peak intensity refers to absorbance. For example, the peak intensity (I) corresponding to OH (e.g., -OH) is... OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 The absorbance can be expressed as the ratio of the absorbance of the OH (e.g., -OH) peak to the absorbance of the CF2 (e.g., -CF2-) peak. In this modified polytetrafluoroethylene, -OH is present as an electron-donating group, and -F is removed from the surface as an electron-withdrawing group, thereby improving electrochemical stability. This ensures that embodiments of this disclosure provide batteries exhibiting superior discharge capacity and cycle life characteristics.

[0039] If the peak intensity (I) of modified polytetrafluoroethylene corresponding to OH (e.g., -OH) OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 If the peak intensity (Ig) of the modified polytetrafluoroethylene is less than approximately 0.03, the aforementioned effects will not be fully achieved.OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 If the oxygen content exceeds approximately 0.3, it cannot be used to prepare dry negative electrodes. Typically, polytetrafluoroethylene contains very little or no oxygen, and therefore exhibits almost no peaks corresponding to OH (e.g., -OH) in FT-IR spectroscopy measurements (I...). OH Accordingly, if polytetrafluoroethylene exhibits a peak intensity ratio (I... OH / I CF2 If the surface of polytetrafluoroethylene has been modified, then it can be determined that the surface of polytetrafluoroethylene has been modified.

[0040] In one or more embodiments, FT-IR spectral measurements can be performed using FT-IR equipment (FT / IR-8X FV, Jasco) under the following conditions.

[0041] Measurement range: Approximately 4000cm -1 Approximately 600cm -1

[0042] Analysis of the attachment: EasiDiff (Pike technologies)

[0043] Detector: TGS

[0044] Total: 32 times

[0045] In the FT-IR spectrum of modified polytetrafluoroethylene (PTFE) used as a dry binder, peaks corresponding to CF2 (e.g., -CF2-) and OH (e.g., -OH) can be observed. For example, peaks related to CF2 (e.g., -CF2-) and OH (e.g., -OH) will appear in the FT-IR curve obtained by measurements of modified PTFE.

[0046] In the FT-IR spectrum, the peak corresponding to CF2 (e.g., -CF2-) appears at approximately 1280 cm⁻¹. -1 ~approximately 1290cm -1 The peak at [location], and the peak corresponding to OH (e.g., -OH) appears at approximately 3350 cm⁻¹. -1 ~approximately 3450cm -1 The peak at that location.

[0047] The modified polytetrafluoroethylene according to one or more embodiments may be a chemically bonded compound of polytetrafluoroethylene and an amine compound. The amine compound may be methanolamine, ethanolamine, propanolamine, butanolamine, ethylenediamine, or a combination thereof.

[0048] This article will explain in more detail the method for preparing this modified polytetrafluoroethylene.

[0049] Polytetrafluoroethylene (PTFE) can be added to a solvent to prepare PTFE liquid. The solvent can be one that does not dissolve PTFE, but has a chemical affinity for PTFE, allowing it to swell.

[0050] Solvents may be, for example, acetone, diethylene glycol dimethyl ether, tetrahydrofuran, 2,2,2-trifluoroethanol, toluene, ethyl acetate, ethanol, 2-methoxyethanol, methyl acetate, 1-dodecyl mercaptan, butylamine, triethylamine, chloroform, 1-propanol, 1-hexanol, 1-octanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, pyridine, diethyl ether, methyl tert-butyl ether, dimethyl carbonate, diethyl carbonate, or combinations thereof.

[0051] The amount of polytetrafluoroethylene (PTFE) added can be approximately 1g to approximately 50g, approximately 5g to approximately 30g, or approximately 10g to approximately 20g per 100ml of solvent. If the amount of PTFE added is within the aforementioned range, the swelling caused by the solvent can further enhance the reactivity of PTFE with amine compounds.

[0052] Subsequently, an amine compound can be added to the polytetrafluoroethylene liquid to prepare a mixture. The amine compound may be in a liquid state at room temperature, and examples of such compounds may be methanolamine, ethanolamine, propanolamine, butanolamine, ethylenediamine, or combinations thereof.

[0053] The amount of amine compounds can be equal to the amount of solvent.

[0054] The resulting mixture can then be heat-treated. The heat treatment can be carried out at about 60°C to about 300°C, about 60°C to about 200°C, or about 60°C to about 150°C.

[0055] The heat treatment can be carried out for approximately 10 minutes to approximately 30 hours, approximately 10 minutes to approximately 25 hours, or approximately 10 minutes to approximately 24 hours.

[0056] Heat treatment can be carried out in an oxygen (O2) atmosphere, a nitrogen (N2) atmosphere, or a combination thereof.

[0057] The heat-treated product can be rinsed to prepare modified polytetrafluoroethylene.

[0058] Rinsing can be done with water. Rinsing can be done at least once and no more than about ten times.

[0059] Before rinsing, the heat-treated product can be cooled to room temperature (approximately 20°C to 25°C).

[0060] Furthermore, the rinsed product can be dried, and the rinsed product can be further filtered. Filtration can be performed using a polytetrafluoroethylene (PTFE) filter. The filter may have dimensions capable of separating products with an average size of about 0.2 µm to about 0.45 µm. For example, the filter may have pores or openings capable of separating products with an average size of about 0.2 µm to about 0.45 µm.

[0061] The dry adhesive according to one or more embodiments may be applied to the negative electrode or the positive electrode, or both the negative electrode and the positive electrode. In another embodiment, the dry adhesive may be applied to the negative electrode.

[0062] electrode

[0063] An electrode according to one or more embodiments includes a dry binder and an active material. In one or more embodiments, the dry binder and the active material are included in an active material layer. The electrode includes a current collector supporting the active material layer.

[0064] The electrode according to one or more embodiments may be a negative electrode or a positive electrode, or both a negative electrode and a positive electrode.

[0065] If the electrode according to one or more embodiments is a negative electrode, the negative electrode active material layer may include a dry binder and a negative electrode active material and an optional conductive material (e.g., an electrically conductive material), or may consist of a dry binder and a negative electrode active material and an optional conductive material (e.g., an electrically conductive material), and may not include any additional binders other than the dry binder.

[0066] Based on a 100wt% negative electrode active material layer, the amount of dry binder may be from about 0.5wt% to about 10wt% or from about 0.5wt% to about 5wt%. Based on a 100wt% negative electrode active material layer, the amount of negative electrode active material may be from about 90wt% to about 99.5wt% or from about 95wt% to about 99.5wt%.

[0067] In one or more embodiments, the negative electrode active material layer may include a conductive material (e.g., an electrically conductive material), and herein, the negative electrode active material layer may include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0.5 wt% to about 5 wt% of the conductive material.

[0068] The negative electrode active material may include materials that can reversibly insert / deintercalate lithium ions, lithium metal, lithium metal alloys, materials that can be doped / dedoped with lithium, and / or transition metal oxides.

[0069] Materials capable of reversibly inserting / extracting lithium ions can be carbon-based materials, and for example, crystalline carbon, amorphous carbon, or a combination thereof. Crystalline carbon can be natural graphite and / or artificial graphite of unspecified shape, flakes, sheets, spheres, and / or fibrous, and amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0070] Lithium metal alloys include alloys of lithium with metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0071] Materials capable of doping / dedoping lithium can be Si-based negative electrode materials and / or Sn-based negative electrode active materials. Si-based negative electrode active materials can be silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), or combinations thereof. Sn-based negative electrode active materials can be Sn, SnO k (0 < k ≤ 2), Sn-based alloys, or combinations thereof.

[0072] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to one or more embodiments, the silicon-carbon composite can include silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the secondary particles. Amorphous carbon can also be between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be distributed in an amorphous carbon matrix.

[0073] The silicon-carbon composite can also include a core in which silicon particles are distributed in an amorphous carbon matrix and an amorphous carbon coating on the surface of the core.

[0074] The secondary particles can be at the center of the silicon-carbon composite, so it can be referred to as the core or central part. The amorphous carbon coating can be referred to as the outer part or shell.

[0075] The silicon particles can be nano-silicon particles. The nano-silicon particles can have an average particle size of about 10 nm to about 1,000 nm, and according to one or more embodiments, can be about 20 nm to about 900 nm, about 20 nm to about 800 nm, about 20 nm to about 500 nm, about 20 nm to about 300 nm, or about 20 nm to about 150 nm. If the average particle size of the silicon particles is within the foregoing range, extreme volume expansion caused during charging and discharging can be suppressed or reduced, and breakage of conduction paths (e.g., conductive paths) due to pulverization of the particles during charging and discharging can be prevented or reduced.

[0076] In this embodiment, the mixing ratio of nano-silicon particles and amorphous carbon by weight can be approximately 20:80 to approximately 70:30.

[0077] In one or more embodiments, the silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles, and an amorphous carbon coating on the surface of the core.

[0078] If the silicon-carbon composite comprises silicon particles, crystalline carbon, and amorphous carbon, then based on 100 wt% of the silicon-carbon composite, the amount of amorphous carbon may be about 30 wt% to about 70 wt%, and based on 100 wt% of the silicon-carbon composite, the amount of crystalline carbon may be about 1 wt% to about 20 wt%. Based on 100 wt% of the silicon-carbon composite, the amount of silicon particles may be about 20 wt% to about 69 wt%, or, according to one or more embodiments, about 30 wt% to about 60 wt%.

[0079] The particle size of the silicon-carbon composite can be adjusted appropriately or suitably, and is not limited thereto.

[0080] If amorphous carbon is present around the surface of the secondary particles, its thickness can be adjusted appropriately or suitably, and it can be present, for example, at a thickness of about 5 nm to about 100 nm.

[0081] Si-based and / or Sn-based negative electrode active materials can be used together with carbon-based negative electrode active materials.

[0082] This includes conductive materials to provide electrode conductivity (e.g., electrical conductivity), and any suitable electrically conductive material may be used as a conductive material unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Examples of conductive materials may include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials including metal powders and / or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0083] The negative electrode current collector may include one selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal (e.g., an electrically conductive metal), and combinations thereof. In embodiments, a current collector coated with an aqueous or non-aqueous adhesive on the surface of the substrate may also be used.

[0084] Waterborne adhesives may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acryloyl resin, phenolic resin, epoxy resin, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, or combinations thereof.

[0085] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, (meth)acryloyl resin, polyester resin, nylon, or combinations thereof. The coating thickness of the water-based or non-aqueous adhesive may be appropriately or suitably adjusted.

[0086] If the electrode according to one or more embodiments is a positive electrode, the positive electrode active material layer may include a dry binder, a positive electrode active material and a conductive material, and may further include an aqueous binder, a non-aqueous binder or a combination thereof.

[0087] Based on a 100wt% positive electrode active material layer, the amount of dry binder can be approximately 0.5wt% to approximately 5wt% or approximately 0.5wt% to approximately 3wt%. Based on a 100wt% positive electrode active material layer, the amount of positive electrode active material can be approximately 90wt% to approximately 99wt% or approximately 94wt% to approximately 99wt%. The amount of conductive material can be approximately 0.5wt% to approximately 5wt% or approximately 0.5wt% to approximately 3wt%.

[0088] The positive electrode active material can be a lithiated intercalation compound that reversibly inserts and deintercalates lithium ions. In one or more embodiments, one or more composite oxides of lithium and metals selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0089] The composite oxide may be a lithium transition metal composite oxide, and examples may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof.

[0090] As an example, a compound represented by any of the following chemical formulas can be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c Dc (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b- c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0< α <2); Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); Li a FePO4 (0.90≤a≤1.8).

[0091] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 It is Mn, Al, or a combination thereof.

[0092] For example, the positive electrode active material can be a high-nickel positive electrode active material (lithium transition metal composite oxide). Based on 100 mol% of lithium-excluded metals in the lithium transition metal composite oxide, the high-nickel positive electrode active material has a nickel content of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. High-nickel positive electrode active materials can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0093] The binder is used to ensure good adhesion between the positive electrode active material particles and also to the positive electrode current collector. Non-limiting examples of binders may include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resins, (meth)acrylate resins, polyester resins, and nylon.

[0094] Conductive materials may be included to provide electrode conductivity (e.g., electrical conductivity) for the positive electrode, and any electrically conductive material may be used as a conductive material (e.g., electrically conductive material) unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Non-limiting examples of conductive materials may include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials including metal powders and / or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0095] The positive electrode current collector may include, but is not limited to, Al. Positive electrode current collectors with an aqueous or non-aqueous adhesive coated on the surface of an Al substrate may also be used. Aqueous adhesives may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acryloyl resin, phenolic resin, epoxy resin, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, or combinations thereof.

[0096] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, (meth)acryloyl resin, polyester resin, nylon, or combinations thereof.

[0097] The coating thickness of water-based or non-water-based adhesives can be adjusted appropriately or suitablely.

[0098] Rechargeable lithium batteries

[0099] Another embodiment provides a rechargeable lithium battery including electrodes and an electrolyte.

[0100] The electrode comprises a dry binder and an active material according to one or more embodiments, and may be a negative electrode or a positive electrode. If the electrode is a negative electrode, the positive electrode may be a conventional positive electrode or a positive electrode comprising a dry binder according to one or more embodiments. In another embodiment, if the electrode is a positive electrode, the negative electrode may be a conventional negative electrode or a negative electrode comprising a dry binder according to one or more embodiments.

[0101] electrolytes

[0102] Electrolytes include non-aqueous organic solvents and lithium salts.

[0103] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of the battery.

[0104] Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0105] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), etc.

[0106] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, γ-butyrolactone, mevalonate lactone, valproic acid lactone, caprolactone, etc.

[0107] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include nitriles, such as R-CN (where R is a C2~C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, ether groups, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0108] Non-aqueous organic solvents can be used alone or in mixtures of two or more types (or kinds).

[0109] If carbonate solvents are used, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0110] The electrolyte may further include ethylene ethyl carbonate, vinylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, brominated ethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, or combinations thereof as additives.

[0111] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in batteries, ensuring basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Non-limiting examples of lithium salts may include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (where x and y are integers from about 1 to about 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0112] diaphragm

[0113] Depending on the type (or category) of the rechargeable lithium battery, a separator may be present between the positive and negative electrodes. Such a suitable separator may include polyethylene separators, polypropylene separators, polyvinylidene fluoride separators, and their multilayers (such as polyethylene / polypropylene double-layer separators, polyethylene / polypropylene / polypropylene triple-layer separators, and / or polypropylene / polypropylene / polypropylene triple-layer separators).

[0114] The diaphragm may include a porous substrate and a coating, the coating comprising an organic material, an inorganic material, or a combination thereof on one or both surfaces (e.g., two opposing surfaces) of the porous substrate.

[0115] The porous substrate may be a membrane formed from a copolymer or mixture of any one or two or more of the following: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (Teflon).

[0116] Organic materials may include polyvinylidene fluoride polymers and / or (meth)acrylic acid polymers.

[0117] Inorganic materials may include, but are not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof.

[0118] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0119] Based on their shape, rechargeable lithium batteries can be classified as cylindrical, prismatic, pouch and / or coin type (or variety). Figures 1-4 A schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 1 A cylindrical battery is shown. Figure 2 A prismatic battery is shown, and Figure 3 and Figure 4 A pouch-type battery is shown. (Reference) Figures 1-4 The rechargeable lithium battery 100 includes an electrode assembly 40 (including a separator 30 between a positive electrode 10 and a negative electrode 20) and a housing (including the electrode assembly 40). The positive electrode 10, negative electrode 20, and separator 30 may be impregnated with an electrolyte. Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 includes electrode terminals 70 that serve as an electrical path to guide current formed in the electrode assembly 40 to the outside. Figure 4 For example, positive electrode terminal 71 and negative electrode terminal 72 ( Figure 3 ).

[0120] Rechargeable lithium batteries according to one or more embodiments can be used in automobiles, mobile phones and / or various suitable types (or kinds) of electronic devices, but this disclosure is not limited thereto.

[0121] The following describes embodiments and comparative examples of this disclosure. However, these examples should not be construed in any way as limiting the scope of this disclosure.

[0122] Example 1

[0123] 1 g of polytetrafluoroethylene powder was added to acetone (5 ml) to prepare a liquid polytetrafluoroethylene. Ethanolamine (5 ml) was added to the liquid polytetrafluoroethylene to prepare a mixture.

[0124] The mixture was heated at 100°C in an oxygen atmosphere for 3 hours, and then cooled to room temperature (25°C). The resulting cooled product was washed twice with water and then filtered using a polytetrafluoroethylene filter (average size: 0.2µm) to obtain a product with a size of 0.2µm.

[0125] The obtained product was then dried to prepare modified polytetrafluoroethylene.

[0126] 97.5 wt% of artificial graphite and 2.5 wt% of the resulting modified polytetrafluoroethylene dry binder were dry-mixed and the mixture was extruded to prepare a sheet-type self-supporting negative electrode active material layer.

[0127] A negative electrode active material layer was bonded to a copper current collector coated with styrene-butadiene rubber to prepare a negative electrode. In the prepared negative electrode, the loading level of the negative electrode active material layer was 21.93 mg / cm³. 2 Furthermore, the active mass density is 1.35 g / cc.

[0128] A negative electrode, a lithium metal counter electrode, and an electrolyte are used to manufacture a half-cell. As the electrolyte, 1M LiPF6 dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate (50:50 by volume) is used.

[0129] Example 2

[0130] Modified polytetrafluoroethylene was prepared in essentially the same manner as in Example 1, except that heating was performed for 6 hours.

[0131] The negative electrode and half cell were manufactured using modified polytetrafluoroethylene in essentially the same manner as in Example 1.

[0132] Example 3

[0133] Modified polytetrafluoroethylene was prepared in essentially the same manner as in Example 1, except that heating was carried out for 12 hours.

[0134] The negative electrode and half cell were manufactured using modified polytetrafluoroethylene in essentially the same manner as in Example 1.

[0135] Example 4

[0136] Modified polytetrafluoroethylene was prepared in essentially the same manner as in Example 1, except that heating was carried out for 24 hours.

[0137] The negative electrode and half cell were manufactured using modified polytetrafluoroethylene in essentially the same manner as in Example 1.

[0138] Example 5

[0139] Modified polytetrafluoroethylene was prepared in essentially the same manner as in Example 1, except that heating was carried out for 24 hours and the acetone solvent was changed to diethylene glycol dimethyl ether.

[0140] The negative electrode and half cell were manufactured using modified polytetrafluoroethylene in essentially the same manner as in Example 1.

[0141] Comparative Example 1

[0142] 97.5 wt% artificial graphite and 2.5 wt% polytetrafluoroethylene dry binder were dry-mixed and the mixture was extruded to prepare a sheet-type self-supporting negative electrode active material layer.

[0143] A negative electrode active material layer was bonded to a copper current collector coated with styrene-butadiene rubber to prepare a negative electrode. In the prepared negative electrode, the loading level of the negative electrode active material layer was 21.93 mg / cm³. 2 Furthermore, the active mass density is 1.35 g / cc.

[0144] A negative electrode, a lithium metal counter electrode, and an electrolyte are used to manufacture a half-cell. As the electrolyte, 1M LiPF6 dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate (50:50 by volume) is used.

[0145] Comparative Example 2

[0146] 1g of polytetrafluoroethylene powder was added to ethanolamine (5ml) to prepare a mixture.

[0147] The mixture was heated at 100°C for 24 hours and then cooled at room temperature (25°C).

[0148] The resulting cooled product was rinsed twice with water and then filtered using a polytetrafluoroethylene filter (average size: 0.2µm) to obtain a product with a size of 0.2µm.

[0149] The obtained product was then dried to prepare modified polytetrafluoroethylene.

[0150] 97.5 wt% of artificial graphite and 2.5 wt% of the resulting modified polytetrafluoroethylene dry binder were dry-mixed and the mixture was extruded to prepare a sheet-type self-supporting negative electrode active material layer.

[0151] A negative electrode active material layer was bonded to a copper current collector coated with styrene-butadiene rubber to prepare a negative electrode. In the prepared negative electrode, the loading level of the negative electrode active material layer was 21.93 mg / cm³. 2 Furthermore, the active mass density is 1.35 g / cc.

[0152] A negative electrode, a lithium metal counter electrode, and an electrolyte are used to manufacture a half-cell. As the electrolyte, 1M LiPF6 dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate (50:50 by volume) is used.

[0153] Comparative Example 3

[0154] Modified polytetrafluoroethylene was prepared in essentially the same manner as in Example 1, except that heating was carried out for 48 hours.

[0155] Modified polytetrafluoroethylene was used as a dry binder, and the same procedures as in Example 1 were performed. However, as Figure 5 As shown, a broken negative electrode was obtained, which cannot be used as a negative electrode. Therefore, it is impossible to manufacture a half-cell.

[0156] Comparative Example 4

[0157] Modified polytetrafluoroethylene was prepared in essentially the same manner as in Example 1, except that heating was carried out for 120 hours.

[0158] Modified polytetrafluoroethylene was used as a dry binder, and the same process as in Example 1 was performed, but the negative electrode and half cell could not be manufactured.

[0159] Experimental Example 1) Evaluation of FT-IR

[0160] The dry adhesives of Examples 1 to 4 and Comparative Examples 1 to 4 were analyzed by FT-IR equipment (FT / IR-8X FV, Jasco) under the following conditions.

[0161] Measurement range: Approximately 4000cm -1 Approximately 600cm -1

[0162] Analysis of the attachment: EasiDiff (Pike technologies)

[0163] Detector: TGS

[0164] Total: 32 times

[0165] In the obtained measurement spectra, the FT-IR spectra of Example 1 and Comparative Example 1 are as follows: Figure 6 As shown in the image. Figure 6 As shown in the figure, compared with the -OH related peak of Comparative Example 1, the peak of Example 1 is at 3391 cm⁻¹. -1 It exhibits a stronger -OH-related peak.

[0166] The FT-IR spectrum of Example 2 is in Figure 7 As shown, the FT-IR spectrum of Example 3 is in Figure 8 As shown, the FT-IR spectrum of Example 4 is in Figure 9 As shown in the figure, and the FT-IR spectrum of Example 5 is in Figure 10 As shown in the image.

[0167] The FT-IR spectra of Comparative Examples 2 to 4 are in Figure 11 The results are shown in [the diagram]. For comparison, the results of Comparative Example 1 are also shown in [the diagram]. Figure 11 As shown in the image.

[0168] from Figures 7-11 The results shown show that, compared with the -OH related peak of Comparative Example 1, the binders of Examples 2-5, Comparative Examples 3 and 4 have a peak at 3391 cm⁻¹. -1 A stronger -OH correlation peak was observed at 3391 cm⁻¹. The binder in Comparative Example 2 showed a peak at 3391 cm⁻¹. -1 The -OH related peak shown here is almost identical to the -OH related peak observed in Comparative Example 1.

[0169] In the obtained measured spectrum, the absorbance ratio (I) is calculated. OH / I CF2 For example, 3391cm -1 -OH related peak at 1286 cm⁻¹ -1 Peak intensity ratio of -CF2 related peak at (I) OH / I CF2 The results are shown in Table 1.

[0170] Table 1

[0171]

[0172] As shown in Table 1, the dry binders of Examples 1 to 5 exhibit peak intensities (IL) of 0.0392 to 0.2919 corresponding to OH (e.g., -OH). OH ) relative to the peak intensity (I) corresponding to CF2 (e.g., -CF2-). CF2 The proportion of (I) OH / I CF2 ).

[0173] However, the dry binders of Comparative Example 1 and Comparative Example 2 exhibited very low peak strength ratios of 0.0015 and 0.0096, respectively (I0.0015). OH / I CF2 Comparative Examples 3 and 4 show significantly higher values ​​of 0.3138 and 0.5925, respectively.

[0174] Experiment Example 2) Evaluation of Initial Efficiency

[0175] The half-cells according to Examples 1 to 5, as well as Comparative Examples 1 and 2, were charged and discharged once at 0.1C. The measured charge and discharge capacities are shown in Table 2. The ratio of discharge capacity to charge capacity was calculated. The results are shown in Table 2 as the initial efficiency.

[0176] Table 2

[0177]

[0178] As shown in Table 2, the batteries according to Examples 1 to 5 exhibit high charging and discharging capacities as well as excellent initial efficiency.

[0179] However, Comparative Example 1 showed a significantly degraded initial efficiency, and Comparative Example 2 showed a significantly reduced charging and discharging capacity.

[0180] Example 3) Evaluation of dQ / dV (differential capacity)

[0181] The half-cells from Examples 1 to 5, and Comparative Examples 1 and 2, were charged and discharged once at 0.05C. Graphs showing the voltage (V, x-axis) relative to lithium metal and the values ​​obtained by differentiating the charge and discharge capacity relative to the voltage (dQ / dV, y-axis) are plotted. Among these results, the charge and discharge curves of Examples 1 to 5 and Comparative Example 1 after one cycle are shown in... Figure 12 The charging and discharging curves of Comparative Example 1 and Comparative Example 2 are shown in the figure. Figure 14 The differential capacities (dQ / dV, side reaction regions) of Examples 1 to Comparative Examples 5 and Comparative Example 1 are shown in the figure. Figure 13 In the comparison, the differential capacity (dQ / dV, side reaction region) of Example 2 is shown in Figure 15In order to make a comparison, the results of Comparative Example 1 are also shown in [the table / reference]. Figure 14 and Figure 15 middle.

[0182] like Figure 12 As shown, compared to Comparative Example 1, the batteries according to Examples 1-5 exhibit slightly lower charging capacity, but show similar discharge capacity, indicating excellent initial efficiency. Figure 14 In Comparative Example 2, a significant reduction in charging and discharging capacity is observed, particularly a significant reduction in charging capacity.

[0183] like Figure 13 As shown, compared to Comparative Example 1, the batteries according to Examples 1 to 5 exhibit smaller peak areas (in Figure 13 In the figure, the thickest line at the top represents the results of Example 5. These results show that very few side reactions occurred. Figure 15 As shown in Comparative Example 2, the electrode side reaction occurred at a lower potential, indicating a significant increase in electrode impedance (e.g., electrode resistance).

[0184] While the subject matter of this disclosure has been described in conjunction with embodiments now considered to be practical examples, it should be understood that this disclosure is not limited to the disclosed embodiments. Rather, this disclosure is intended to cover various suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

Claims

1. A dry binder for rechargeable lithium batteries, comprising: Modified polytetrafluoroethylene containing carbon, fluorine, and oxygen. The modified polytetrafluoroethylene thereon has the following characteristics: In FT-IR spectroscopy measurements, the peak intensity I corresponding to OH is 0.03–0.

3. OH Relative to the peak intensity I corresponding to CF2 CF2 Ratio I OH / I CF2 .

2. The dry binder for rechargeable lithium batteries according to claim 1, wherein the peak intensity I corresponding to OH is... OH Relative to the peak intensity I corresponding to CF2 CF2 The ratio I OH / I CF2 The value is 0.05~0.

3.

3. The dry binder for rechargeable lithium batteries according to claim 1, wherein the peak intensity I corresponding to OH OH Relative to the peak intensity I corresponding to CF2 CF2 The ratio I OH / I CF2 It is 0.1~0.

2.

4. The dry binder for rechargeable lithium batteries according to claim 1, wherein the modified polytetrafluoroethylene is a chemically bonded compound of polytetrafluoroethylene and an amine compound.

5. The dry binder for rechargeable lithium batteries according to claim 4, wherein the amine compound comprises methanolamine, ethanolamine, propanolamine, butanolamine, ethylenediamine, or combinations thereof.

6. The dry binder for rechargeable lithium batteries according to claim 1, wherein the peak corresponding to CF2 appears at 1280 cm⁻¹. -1 ~1290cm -1 The peak at that location.

7. The dry binder for rechargeable lithium batteries according to claim 1, wherein the peak corresponding to OH appears at 3350 cm⁻¹. -1 ~3450cm -1 The peak at that location.

8. The dry binder for rechargeable lithium batteries according to claim 1, wherein the modified polytetrafluoroethylene is prepared by: Polytetrafluoroethylene is added to a solvent to prepare a liquid polytetrafluoroethylene; An amine compound is added to the polytetrafluoroethylene liquid to prepare a mixture; The mixture is heat-treated to prepare a heat-treated product; and The heat-treated product is then rinsed.

9. The dry binder for rechargeable lithium batteries according to claim 8, wherein the solvent comprises acetone, diethylene glycol dimethyl ether, tetrahydrofuran, 2,2,2-trifluoroethanol, toluene, ethyl acetate, ethanol, 2-methoxyethanol, methyl acetate, 1-dodecyl mercaptan, butylamine, triethylamine, chloroform, 1-propanol, 1-hexanol, 1-octanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, pyridine, diethyl ether, methyl tert-butyl butyl ether, dimethyl carbonate, diethyl carbonate, or combinations thereof.

10. The dry binder for rechargeable lithium batteries according to claim 8, wherein the heat treatment is performed for 10 minutes to 30 hours.

11. An electrode for a rechargeable lithium battery, comprising: The dry adhesive according to any one of claims 1 to 10; and Active substances.

12. The electrode for a rechargeable lithium battery according to claim 11, wherein the active material is a negative electrode active material.

13. The electrode for a rechargeable lithium battery according to claim 12, wherein the negative electrode active material comprises crystalline carbon.

14. A rechargeable lithium battery, comprising: The electrode according to any one of claims 11 to 13, and Electrolytes.

Images