Electrode of rechargeable lithium battery and rechargeable lithium battery

Abstract

Disclosed are an electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same, the electrode comprising: a current collector; an electrode active material layer on the current collector; and a functional layer, in which the functional layer comprises a lithium-containing polyoxazoline.

Description

Technical Field

[0001] Disclosed are an electrode for a rechargeable lithium battery and a rechargeable lithium battery. Background Art

[0002] Due to the rapid growth of electric vehicles around the world, the use of efficient renewable energy in response to climate change, the widespread use of Internet of Things (IoT) devices, etc., the demand for rechargeable lithium batteries is growing rapidly. Since the demand for technology for fast charging while ensuring energy density is also growing rapidly, various related studies are actively being conducted. Among these various attempts, research on placing the active material constituting the electrode thicker on the current collector to form a thick film electrode and thus increase the energy storage per unit volume is said to be a relatively easy method. However, how to make such a thick film electrode may not only be a challenge, but how to solve the problem that the thick film electrode makes it more difficult for ions and electrons to move in the thickness direction is another challenge. For example, because the fast charging situation utilizes the rapid movement of lithium ions, lithium precipitation inevitably occurs at the negative electrode due to current concentration and overpotential, which will be effective from the solution. Summary of the invention

[0003] The fast-charge cycle-life characteristics of rechargeable lithium batteries are improved by ensuring the reversibility of lithium deposited on the negative electrode during fast charging, and the cycle-life stability of rechargeable lithium batteries is improved through solid electrolyte interface (SEI) modification.

[0004] In some embodiments, an electrode for a rechargeable lithium battery includes: a current collector; an electrode active material layer on the current collector; and a functional layer, wherein the functional layer includes a lithium-containing polyoxazoline.

[0005] In some embodiments, a rechargeable lithium battery includes the above-described electrodes and an electrolyte.

[0006] According to some embodiments, the reversibility of lithium deposited on fast-charged battery electrodes is improved, thereby improving the cycle life characteristics of rechargeable lithium batteries under fast-charge conditions, and the cycle life stability of rechargeable lithium batteries can be improved through SEI film modification. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The drawings, together with the specification, illustrate embodiments of the presently disclosed subject matter, and, together with the description, serve to explain principles of the embodiments of the presently disclosed subject matter.

[0008] Figure 1 is a perspective view schematically illustrating a rechargeable lithium battery according to some embodiments.

[0009] Figure 2is a cross-sectional view schematically illustrating a rechargeable lithium battery according to some embodiments.

[0010] Figure 3 and Figure 4 is a perspective view schematically illustrating a rechargeable lithium battery according to some embodiments.

[0011] Figure 5 and Figure 6 is the infrared spectrum (IR) of the functional polymer (Li-POX) and POX prepared in Example 1.

[0012] Figure 7 Time-of-flight-secondary ion mass spectrometer (ToF-SIMS) depth analysis results for the rechargeable lithium battery cells of Example 1 and Comparative Example 1 are shown, and are graphs showing changes in the composition of the SEI film before and after formation.

[0013] Figure 8 The cycle-life characteristics of Example 1 and Comparative Example 1 under rapid charging conditions are shown, and are graphs showing discharge specific capacities according to the number of cycles. DETAILED DESCRIPTION

[0014] Hereinafter, the exemplary embodiments will be described in more detail so that those skilled in the art can easily implement the exemplary embodiments. However, the subject matter of the present disclosure may be implemented in many different forms and is not to be construed as limited to the exemplary embodiments set forth herein.

[0015] The terms used herein are for describing the embodiments only and are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, a singular expression includes a plural expression.

[0016] As used herein, "combinations thereof" means mixtures, stacks, composites, copolymers, alloys, blends, and / or reaction products of the components, and the like.

[0017] Here, it should be understood that terms such as “comprises,” “includes,” or “has” are intended to indicate the presence of the presented features, quantities, steps, elements, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0018] In the drawings, the thickness of layers, films, panels, regions, etc. may be exaggerated for clarity, and the same reference numerals represent the same elements throughout the specification. It will be understood that if an element such as a layer, film, region, or substrate is referred to as being "on" another element, the element may be directly on the other element, or there may be intervening elements. Conversely, if an element is referred to as being "directly on" another element, there are no intervening elements.

[0019] In the embodiments, the “layer” herein includes not only a shape on the entire surface when viewed from a plan view but also a shape on a partial surface.

[0020] The average particle size can be measured by any suitable method commonly used in the art, for example, by a particle size analyzer, and / or by a transmission electron microscopic image and / or a scanning electron microscopic image. In an embodiment, the average particle size value can be obtained by measuring using a dynamic light scattering method, performing data analysis, counting the number of particles in each particle size range, and calculating from this. Unless otherwise defined, the average particle size can mean the diameter (D) of particles having a cumulative volume of 50% by volume in a particle size distribution. 50 ) (i.e., the average particle size (D 50 )). As used herein, if no definition is otherwise provided, the average particle diameter means the diameter (D) of particles having a cumulative volume of 50% by volume in a particle size distribution obtained by randomly measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscopic image. 50 ).

[0021] Here, “or” is not to be interpreted as an exclusive meaning, for example, “A or B” is to be interpreted as including A, B, and A+B, etc.

[0022] The term "metal" is interpreted as a concept that includes common metals, transition metals, and metalloids (semimetals).

[0023] Electrodes for rechargeable lithium batteries In some embodiments, an electrode for a rechargeable lithium battery includes a current collector, an electrode active material layer on the current collector, and a functional layer, wherein the functional layer includes a lithium-containing polyoxazoline.

[0024] The functional layer may be on the electrode active material layer and / or between the current collector and the electrode active material layer. As an example, the electrode may include a current collector, an electrode active material layer on the current collector, and a functional layer on the electrode active material layer. The functional layer may be a coating layer of a type (or species) including a functional polymer. By introducing the above-mentioned functional layer into the electrode, the physical strength can be improved, and the shape of the lithium precipitation can be induced to be a uniform (e.g., substantially uniform) film form rather than a dendrite form, and the reversibility of the precipitated lithium can be improved, and the reversibility of the precipitated lithium is the ratio of the desorbed lithium metal to the electrodeposited lithium metal. In addition, the functional polymer of the functional layer can be used as a capture agent for lithium salts and / or anions, and accordingly, the components of the SEI generated during the battery formation process can be affected, for example, a LiF-rich SEI can be induced, and by this, the cycle life stability of the battery can be improved.

[0025] The thickness of the functional layer is not particularly limited, but in some embodiments, it can be as thin as a few microns, or a few nanometers to hundreds of nanometers, so that the reversibility of the precipitated lithium can be improved without increasing the total thickness and total volume of the battery. The thickness of the functional layer can be, for example, about 5nm to about 900nm, about 5nm to about 700nm, about 10nm to about 500nm, or about 20nm to about 300nm. The thickness of the functional layer can be measured by a scanning electron microscope image of a cross-section of the electrode.

[0026] The functional layer can be introduced into the electrode by various suitable methods, for example, it can be introduced by general coating methods, and for example, it can be coated by electrospinning. If the functional layer is coated by electrospinning, a very thin and strong functional layer can be introduced.

[0027] Polyoxazoline that does not include lithium does not have the ability of transmitting lithium ions, therefore, if it is introduced into the functional layer in the electrode plate, it can be used as resistance (for example, it can increase resistance). Polyoxazoline that contains lithium according to some embodiments has excellent lithium ion transmission performance, therefore if it is introduced into the functional layer, it not only improves the reversibility of the lithium deposited during fast charging, and improves lithium ion conductivity, improves battery performance, in some embodiments, can further improve battery performance by SEI component being adjusted to the SEI rich in LiF.

[0028] The lithium-containing polyoxazoline can be, for example, a polyoxazoline initiated with a lithium salt. For example, the lithium-containing polyoxazoline can be polymerized by dissolving a lithium salt in a monomer solution and then treating the solution at about 30° C. to about 100° C. for about 24 hours to about 72 hours.

[0029] Here, the lithium salt may include, for example, LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiAlO 2 、LiAlCl 4 、LiPO 2 F 2 , LiCl, LiI, LiFSI, LiTFSI, LiOTf, LiBOB, LiDFOB, or a combination thereof. In an embodiment, the concentration of the lithium salt added to the monomer solution may be about 1M to about 5M, or about 3M to about 4M.

[0030] The poly-oxazoline that contains lithium can for example comprise poly-(2-alkyl-2-oxazoline) that contains lithium, poly-(2-aryl-2-oxazoline) or their combination.At this, alkyl (for example, alkyl of poly-(2-alkyl-2-oxazoline) that contains lithium) can be substituted or unsubstituted C1 to C10 alkyl or substituted or unsubstituted C1 to C5 alkyl.Aryl (for example, aryl of poly-(2-aryl-2-oxazoline) that contains lithium) can be substituted or unsubstituted C6 to C20 aryl or substituted or unsubstituted C6 to C12 aryl.

[0031] For example, the lithium-containing polyoxazoline can be lithium-containing poly(2-methyl-2-oxazoline), lithium-containing poly(2-ethyl-2-oxazoline), lithium-containing poly(2-propyl-2-oxazoline), lithium-containing poly(2-isopropyl-2-oxazoline), lithium-containing poly(2-cyclopropyl-2-oxazoline), or a combination thereof.

[0032] The weight average molecular weight (Mw) of the lithium-containing polyoxazoline may be about 500 g / mol to about 500,000 g / mol, such as about 10,000 g / mol to about 70,000 g / mol. In an embodiment, the polydispersity (PDI; Mw) of the lithium-containing polyoxazoline may be about 100 g / mol to about 70,000 g / mol. w / M n ) can be, for example, from about 1 to about 4, such as from about 1.2 to about 1.8 or from about 3 to about 4.

[0033] The electrode for a rechargeable lithium battery according to some embodiments may be a positive electrode or a negative electrode, for example, it may be a negative electrode. By introducing a functional layer in the negative electrode, the reversibility of lithium precipitated during rapid charging may be improved, and thus the cycle life characteristics under battery charging conditions (or rapid charging conditions) may be significantly improved.

[0034] If the electrode is a negative electrode, the current collector may be a negative electrode current collector and the electrode active material layer may be referred to as a negative electrode active material layer. In an embodiment, as another example, the electrode active material layer may be a negative electrode coating layer used in a precipitation-type negative electrode.

[0035] Negative electrode current collector The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li) and / or alloys thereof, and may be in the form of foil, sheet and / or foam. The thickness of the negative electrode current collector may be, for example, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 7 μm to about 10 μm.

[0036] Negative electrode active material layer The negative electrode active material layer includes a negative electrode active material and may optionally further include a binder, a conductive material (e.g., an electrically conductive material), or a combination thereof.

[0037] Negative electrode active material The negative electrode active material may include a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / de-doping lithium, and / or a transition metal oxide.

[0038] The material that can reversibly intercalate / deintercalate lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be amorphous and / or natural graphite and / or artificial graphite in the form of flakes, platelets, spheres, and / or fibers. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, and / or calcined coke, etc.

[0039] The lithium metal alloy includes an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0040] The material capable of doping / de-doping lithium may be a Si-based negative electrode active material and / or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (where 0 < x < 2), a Si-Q alloy (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 (e.g., Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof)) or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO 2 , a Sn alloy, or a combination thereof.

[0041] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50It can be, for example, from about 0.5 μm to about 20 μm. According to some embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it can include secondary particles (cores) assembled from silicon primary particles and an amorphous carbon coating layer (shells) on the surface of the secondary particles. Amorphous carbon can also be present between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in the amorphous carbon matrix.

[0042] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core. The crystalline carbon can be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon can include soft carbon and / or hard carbon, mesophase pitch carbonized products, and / or calcined coke.

[0043] If the silicon-carbon composite includes silicon and amorphous carbon, based on 100 wt% of the silicon-carbon composite, the silicon content can be from about 10 wt% to about 50 wt%, and the content of amorphous carbon can be from about 50 wt% to about 90 wt%. In an embodiment, if the composite includes silicon, amorphous carbon, and crystalline carbon, based on 100 wt% of the silicon-carbon composite, the silicon content can be from about 10 wt% to about 50 wt%, the content of crystalline carbon can be from about 10 wt% to about 70 wt%, and the content of amorphous carbon can be from about 20 wt% to about 40 wt%.

[0044] In an embodiment, the thickness of the amorphous carbon coating layer can be from about 5 nm to about 100 nm. The average particle diameter (D 50 ) of the silicon particles (primary particles) can be from about 10 nm to about 1 μm, or from about 10 nm to about 200 nm. The silicon particles can exist as elemental silicon, in the form of a silicon alloy, and / or in an oxidized form. The oxidized form of silicon can be represented by SiO x (0 < x < 2). At this time, the atomic content ratio of Si:O representing the degree of oxidation can be from about 99:1 to about 33:67. As used herein, if no other definition is provided, the average particle diameter (D 50 ) represents the diameter of the particles at which the cumulative volume in the particle size distribution is about 50 volume%.

[0045] Si-based negative electrode active materials and / or Sn-based negative electrode active materials can be mixed with carbon-based negative electrode active materials. If the Si-based negative electrode active materials and / or Sn-based negative electrode active materials are mixed with the carbon-based negative electrode active materials and used, the mixing ratio can be a weight ratio of from about 1:99 to about 90:10.

[0046] Binder The binder is used to attach the negative electrode active material particles to each other well, and also to attach the negative electrode active material to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0047] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0048] The aqueous binder may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol or a combination thereof.

[0049] If an aqueous binder is used as the negative electrode binder, a cellulose compound capable of imparting or increasing viscosity may be further included. As the cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and their alkali metal salts may be mixed and used. The alkali metal may be Na, K and / or Li.

[0050] The dry binder may be a polymer material that can become fibers (eg, can be fiberized), and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0051] Conductive Materials The conductive material is included to provide electrode conductivity (e.g., to increase conductivity), and any suitable conductive material may be used as the conductive material unless the conductive material causes chemical changes (e.g., causes undesirable chemical changes in a rechargeable lithium battery). Examples of the conductive material include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based 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.

[0052] Based on 100wt% of the negative electrode active material layer, the content of the negative electrode active material may be about 95wt% to about 99.5wt%, and based on 100wt% of the negative electrode active material layer, the content of the binder may be about 0.1wt% to about 5wt%. For example, the negative electrode active material layer may include about 90wt% to about 99wt% of the negative electrode active material, about 0.1wt% to about 5wt% of the binder, and about 0.1wt% to about 5wt% of the conductive material.

[0053] Negative electrode coating The precipitation-type negative electrode does not include a negative electrode active material during battery assembly, but may refer to a negative electrode in which lithium metal or the like is precipitated or electrodeposited on the negative electrode during battery charging, thereby serving as a negative electrode active material.

[0054] The precipitation type negative electrode may include a current collector and a negative electrode coating layer on the current collector. In a rechargeable lithium battery having such a precipitation type negative electrode, initial charging is started in the absence of a negative electrode active material, and during charging, a high density of lithium metal is deposited or electrodeposited between the current collector and the negative electrode coating layer or on the negative electrode coating layer, thereby forming a lithium metal layer that can be used as a negative electrode active material. Therefore, in a rechargeable lithium battery that has been charged once or more times, the precipitation type negative electrode may include, for example, a current collector, a lithium metal layer on the current collector, and a negative electrode coating layer on the lithium metal layer.

[0055] The lithium metal layer may refer to a layer in which lithium metal or the like is precipitated during a charging process of a battery, and may be referred to as a metal layer, a lithium layer, a lithium electrodeposition layer, or a negative electrode active material layer.

[0056] The negative electrode coating layer may be referred to as a lithium electrodeposition inducing layer or a cathode catalyst layer, and may include a metal, a carbon material, or a combination thereof.

[0057] The metal may be a lithiophilic metal and may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one of these and / or alloys of various suitable types (or species) thereof. If the lithiophilic metal is present in the form of particles, its average particle size (D 50 ) may be less than or equal to about 4 μm, for example, about 10 nm to about 4 μm.

[0058] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microspheres, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, superconducting acetylene black (denka black), ketjen black, or a combination thereof.

[0059] If the negative electrode coating layer includes both metal and carbon material, the mixing ratio of the metal and the carbon material can be, for example, a weight ratio of about 1:10 to about 2:1. In an embodiment, the precipitation of lithium metal can be effectively promoted, and the characteristics of the all-solid-state rechargeable battery can be improved. For example, the negative electrode coating layer may include a carbon material on which a catalyst metal is loaded and / or may include a mixture of metal particles and carbon material particles.

[0060] For example, the negative electrode coating layer may include a lithium-philic metal and amorphous carbon, and in an embodiment, the negative electrode coating layer may effectively promote the precipitation of lithium metal. As an example, the negative electrode coating layer may include a composite in which a lithium-philic metal is supported on amorphous carbon.

[0061] The negative electrode coating layer may further include a binder, and the binder may be, for example, a conductive binder (eg, an electrically conductive binder). In an embodiment, the negative electrode coating layer may further include general additives such as a filler, a dispersant, and / or an ion conductive agent.

[0062] The thickness of the negative electrode coating layer may be, for example, about 100 nm to about 20 μm, or about 500 nm to about 10 μm, or about 1 μm to about 5 μm.

[0063] Positive electrode active material layer As an example, the above-mentioned electrode for a rechargeable lithium battery may be a positive electrode, the current collector may be a positive electrode current collector, and the electrode active material layer may be a positive electrode active material layer.

[0064] The positive electrode active material layer includes a positive electrode active material, and may optionally include a binder and / or a conductive material (eg, an electrically conductive material).

[0065] Positive electrode active material The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound). For example, at least one selected from composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0066] The composite oxide may be a lithium transition metal composite oxide, and examples thereof may include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free lithium nickel manganese-based oxides, perlithium layered oxides, or combinations thereof.

[0067] As an example, the positive electrode active material may be a high nickel positive electrode active material having a nickel content of greater than or equal to about 80 mol% based on 100 mol% of metals other than lithium in the lithium transition metal composite oxide. Based on 100 mol% of metals excluding lithium, the nickel content in the high nickel positive electrode active material may be 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%. The high nickel positive electrode active material may achieve high capacity and may be applied to high capacity, high energy density rechargeable lithium batteries.

[0068] As an example, a compound represented by any one of the following chemical formulas may 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 D c (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 O 2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NeG b O 2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O 2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O 2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 2 G b O 4 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO 4 (0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe 2 (PO 4 ) 3 (0≤f≤2); and Li a FePO 4 (0.90≤a≤1.8).

[0069] 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, a rare earth element 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.

[0070] The positive electrode active material may be in the form of secondary particles formed by aggregating a plurality of primary particles, or may be in the form of a single particle. In an embodiment, the positive electrode active material may have a spherical or nearly spherical shape, or may have a polyhedral or irregular shape.

[0071] In an embodiment, the positive electrode active material may include a buffer layer on the surface of the particle. The buffer layer may be in the form of a coating layer, a protective layer, etc., and may play a role in reducing the interface resistance (e.g., interface resistance) between the positive electrode active material and the sulfide solid electrolyte particles. As an example, the buffer layer may include a lithium metal oxide, wherein the metal may be, for example, one or more elements selected from Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. Lithium metal oxides excellently improve the performance of the positive electrode active material by promoting the movement of lithium ions and electronic conduction, while reducing the interface resistance (e.g., interface resistance) between the positive electrode active material and the solid electrolyte particles.

[0072] The positive electrode active material may be included in a content of about 55 wt % to about 99.5 wt %, for example, about 65 wt % to about 95 wt %, or about 75 wt % to about 91 wt %, based on 100 wt % of the positive electrode active material layer.

[0073] Binder The binder improves the bonding properties between the positive electrode active material particles and between the positive electrode active material particles and the current collector. Examples of the binder may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but are not limited thereto.

[0074] Conductive Materials The conductive material is included to provide electrode conductivity (e.g., to provide or increase conductivity), and unless the conductive material causes chemical changes (e.g., undesirable chemical changes in a rechargeable lithium battery), any suitable conductive material may be used as the conductive material. Examples of the conductive material may include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based 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.

[0075] The binder and the conductive material may each be included in an amount of about 0.1 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer.

[0076] The positive electrode current collector may include Al and / or stainless steel (SUS), etc., but is not limited thereto.

[0077] Rechargeable lithium battery Some embodiments provide a rechargeable lithium battery including the above-mentioned electrode and an electrolyte. The rechargeable lithium battery may be a lithium ion battery using an electrolyte solution, or as another example, it may be an all-solid-state rechargeable battery using a solid electrolyte. As an example, a rechargeable lithium battery using an electrolyte will be described.

[0078] Rechargeable lithium batteries may be classified according to shape into a cylindrical shape, a prismatic shape, a pouch shape, a coin shape, and the like. Figures 1 to 4 is a schematic diagram showing a rechargeable lithium battery according to some embodiments, wherein Figure 1 It is a cylindrical battery. Figure 2 It is a prismatic battery. Figure 3 and Figure 4 All are pouch-shaped batteries. Figures 1 to 4 , the rechargeable lithium battery 100 includes an electrode assembly 40 having a separator 30 between a positive electrode 10 and a negative electrode 20, and a case 50 accommodating the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in an electrolyte solution. Figure 1 As shown in , the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. Figure 2 In the embodiment, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. Figure 3 to Figure 4 As shown in FIG. 1 , the rechargeable lithium battery 100 includes electrode tabs 70 , ie, a positive electrode tab 71 and a negative electrode tab 72 , serving as an electrical path for extracting current formed in the electrode assembly 40 to the outside.

[0079] Electrolyte For example, the electrolyte for a rechargeable lithium battery may be an electrolyte that may include a non-aqueous organic solvent and a lithium salt.

[0080] The non-aqueous organic solvent is used as a medium for transmitting ions participating in the electrochemical reaction of the battery. The non-aqueous organic solvent can be a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent and / or an alcohol solvent, an aprotic solvent or a combination thereof.

[0081] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC) and / or butylene carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valerolactone and / or caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran and / or tetrahydrofuran, etc. In an embodiment, ketone solvents may include cyclohexanone, etc. The alcohol solvent may include ethanol and / or isopropanol, etc., and the aprotic solvent may include: nitriles such as R-CN (wherein R is a C2 to C20 linear, branched or cyclic hydrocarbon group, a double bond, an aromatic ring and / or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and / or 1,4-dioxolane; and / or sulfolane, etc.

[0082] The non-aqueous organic solvent may be used alone or in a mixture of two or more types (or species), and if two or more types (or species) are used in a mixture, the mixing ratio may be appropriately or properly adjusted according to suitable or desired battery performance, which should be easily understood upon reading the present disclosure.

[0083] If a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed together and used, and the cyclic carbonate and the chain carbonate may be mixed together in a volume ratio of about 1:1 to about 1:9.

[0084] The non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent. For example, a carbonate-based solvent and an aromatic hydrocarbon organic solvent may be mixed together and used in a volume ratio of about 1:1 to about 30:1.

[0085] The electrolyte may further include vinyl ethyl carbonate, vinylene carbonate and / or ethylene carbonate-based compounds to improve the battery cycle life.

[0086] Examples of the ethylene carbonate-based compound may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0087] The lithium salt dissolved in the organic solvent supplies lithium ions in the battery, enables the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt may include LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiAlO 2 、LiAlCl 4 、LiPO 2 F 2 、LiCl、LiI、LiN(SO 3 C 2 F 5 ) 2 、Li(FSO 2 ) 2 N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC 4 F 9 SO 3 、LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2) (wherein x and y are integers of 1 to 20), at least one selected from lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), lithium difluoro(oxalato)borate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0088] The concentration of the lithium salt may be in the range of about 0.1 M to about 2.0 M. If the concentration of the lithium salt is within the above range, the electrolyte has appropriate or proper ion conductivity and viscosity, and thus excellent performance may be achieved and lithium ions may be efficiently moved.

[0089] Diaphragm Depending on the type (or kind) of the rechargeable lithium battery, the separator may be present between the positive electrode and the negative electrode. The separator may include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, and a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, and / or a polypropylene / polyethylene / polypropylene three-layer separator.

[0090] The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof on one or both surfaces of the porous substrate.

[0091] The porous substrate may be a polymer film formed of any polymer selected from polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, Teflon and polytetrafluoroethylene, and / or copolymers or mixtures of two or more thereof.

[0092] The porous substrate may have a thickness of about 1 μm to about 40 μm, for example, about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm.

[0093] The organic material may include a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide and a second structural unit including at least one selected from a structural unit derived from (meth)acrylic acid or (meth)acrylic ester and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0094] Inorganic materials can include Al 2 O 3 、SiO 2 、TiO 2SnO 2 、CeO 2 , MgO, NiO, CaO, GaO, ZnO, ZrO 2 , Y 2 O 3 、SrTiO 3 、BaTiO 3 Mg(OH) 2 The inorganic particles are selected from the group consisting of, but not limited to, boehmite, and combinations thereof. The average particle size (D 50 ) can be about 1 nm to about 2000 nm, for example, about 100 nm to about 1000 nm, or about 100 nm to about 700 nm.

[0095] The organic material and the inorganic material may be mixed together in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be stacked.

[0096] The coating layer may have a thickness of about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm, or about 1 μm to about 5 μm.

[0097] Examples and comparative examples of the present disclosure are described below. However, the following examples are merely examples of the present disclosure, and the present disclosure is not limited to the following examples.

[0098] Example 1 1. Manufacture of functional polymers Lithium-containing poly-(2-ethyl-2-oxazoline) (Li-POX) was polymerized by adding 3M LiFSI lithium salt to 2-ethyl-2-oxazoline as a liquid monomer and completely dissolving the LiFSI lithium salt in 2-ethyl-2-oxazoline, and then heating the solution at 60°C until the polymerization was completed. The functional polymer (Li-POX) polymerized by initiation of the lithium salt was dissolved in a solvent of acetone and isopropyl alcohol (IPA) with a volume ratio of 5:5 at a concentration of 0.5wt%, thereby preparing a polymer solution.

[0099] 2. Fabrication of Negative Electrode 97wt% of graphite negative electrode active material, 1.7wt% of carboxymethyl cellulose, 0.8wt% of styrene butadiene rubber and 0.5wt% of acetylene black were mixed together in an aqueous solvent to prepare a negative electrode active material layer slurry. The negative electrode active material layer slurry was coated on a copper foil current collector, and then dried and pressed to form a graphite-based negative electrode active material layer on the current collector.

[0100] On the surface of the negative electrode active material layer, the prepared polymer solution was applied by electrospinning. Subsequently, drying was performed at 60°C for 12 hours to manufacture a negative electrode having a functional layer formed on the negative electrode active material layer. The electrospinning method was set as follows. The TCD (tip to current collector distance) was 9 cm, the tip size was 21, a voltage of 25 kV was applied, the flow rate was 4 mL / hr, and the spinning time was 2 minutes.

[0101] 3.Manufacturing of rechargeable lithium battery cells After manufacturing a unit cell by using lithium metal as a counter electrode and inserting a polytetrafluoroethylene separator between the negative electrode and the counter electrode, the unit cell is inserted into a case and 1.15M LiPF 6 An electrolyte solution prepared by dissolving in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 2:4:4 was injected into the case, thereby manufacturing a rechargeable lithium battery cell (half-cell) in a common method.

[0102] Comparative Example 1 A negative electrode and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that the functional layer was not formed on the negative electrode active material layer.

[0103] Evaluation Example 1: IR Analysis of Functional Polymers In order to examine the characteristics of the functional polymer (Li-POX) polymerized by lithium salt according to Example 1, infrared spectroscopy was performed on Li-POX and poly-(2-ethyl-2-oxazoline) (POX) polymerized in a conventional manner without Li-POX and lithium salt, respectively. Figure 5 The peaks corresponding to C=O stretching are shown in Figure 6 The peak corresponding to CN stretching is shown in .

[0104] Reference Figure 5 Compared with POX, the Li-POX according to this example shows a red shift phenomenon in the peak corresponding to C=O stretching, which is understood to be due to the bonding between oxygen and lithium cations. Figure 6 , Li-POX according to this example exhibits a blue shift phenomenon in the peak corresponding to CN stretching compared to POX, which is understood to be caused by the bonding between nitrogen and the anion of the lithium salt.

[0105] Evaluation Example 2: Analysis of changes in SEI components after the formation process At 25°C, the rechargeable lithium battery cells of Example 1 and Comparative Example 1 were charged to 0.01V at a constant current of 0.1C and discharged to 1.5V at a constant current of 0.2C, respectively, to perform initial charging and discharging, i.e., the formation process. The surface of each negative electrode before and after the formation process was subjected to a time-of-flight-secondary ion mass spectrometry (ToF-SIMS) in-depth analysis to analyze the compositional changes of the SEI, and the results were shown in Table 1. Figure 7 Shown in. Figure 7 The curves show that the fluoride ion (F - ) strength. Figure 7 In the figure, the gray curve shows the comparative example 1 before the formation, and the black curve shows the comparative example 1 after the formation. The light yellow curve shows the example 1 before the formation, and the orange curve shows the example 1 after the formation. The example 1 in which the functional layer according to some embodiments is introduced to the surface of the negative electrode shows a strong F on the surface of the negative electrode after the formation process. - Therefore, it is confirmed that the introduced functional layer forms a LiF-rich SEI after the formation process.

[0106] Evaluation Example 3: Evaluation of Rapid Charge Cycle-Life Characteristics In Example 1 and Comparative Example 1, a positive electrode manufactured as follows was used instead of lithium metal. By mixing 96 wt % of LiNi 0.78 Co 0.2 Al 0.02 O 2 A positive electrode active material, 2.0 wt % of a polyvinylidene fluoride binder and 2.0 wt % of an acetylene black conductive material were added to prepare a positive electrode active material layer slurry, the positive electrode active material layer slurry was coated on an aluminum foil current collector, and then dried and pressed to manufacture a positive electrode.

[0107] At 25° C., the full batteries of Example 1 and Comparative Example 1 were charged to 4.25 V at a constant current of 0.1 C and charged to 0.05 C at a constant voltage, and then discharged to 2.8 V at 0.1 C for initial charge and discharge, and then charged and discharged 400 times or more at 1 C / 1 C in the voltage range of 2.8 V to 4.25 V at 25° C. to evaluate the cycle life characteristics, and Figure 8 The results are shown in FIG. 1 as a change in discharge specific capacity according to the number of cycles.

[0108] Reference Figure 8, Example 1 exhibits improved long-term cycle life characteristics compared to Comparative Example 1. Therefore, the rechargeable lithium battery cell incorporating the functional layer according to some embodiments exhibits improved cycle life characteristics under fast charging conditions, which is understood to be because fast charging increases the reversibility of lithium precipitated in the electrode and causes a change in the composition of the SEI, thereby reducing the side reactions between the electrode and the electrolyte solution.

[0109] While the subject matter of the present disclosure has been described in conjunction with what are presently considered to be practical example embodiments, it will be understood that the present disclosure is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

[0110] Description of Reference Numerals 100: Rechargeable lithium battery 10: Positive electrode 11: Positive electrode lead lug 12: Positive electrode terminal 20: Negative electrode 21: Negative electrode lead lug 22: Negative electrode terminal 30: Diaphragm 40: Electrode assembly 50: Shell 60: Sealing component 70: Electrode terminal 71: Positive electrode terminal 72: Negative electrode terminal.

Claims

1. An electrode for a rechargeable lithium battery, the electrode comprising: current collector; An electrode active material layer, on the current collector; as well as Functional layer, Wherein, the functional layer comprises lithium-containing polyoxazoline.

2. The electrode according to claim 1, wherein: The functional layer is on the electrode active material layer and / or between the current collector and the electrode active material layer.

3. The electrode according to claim 1, wherein: The functional layer has a thickness of 5 nm to 900 nm.

4. The electrode according to claim 1, wherein: The functional layer is applied by electrospinning.

5. The electrode according to claim 1, wherein: The lithium-containing polyoxazoline is a polyoxazoline initiated by a lithium salt.

6. The electrode according to claim 5, wherein: The lithium salt includes LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiFSI, LiTFSI, LiOTf, LiBOB, LiDFOB or a combination thereof.

7. The electrode according to claim 1, wherein: The lithium-containing polyoxazoline includes lithium-containing poly(2-alkyl-2-oxazoline), lithium-containing poly(2-aryl-2-oxazoline) or a combination thereof. wherein the alkyl group is a substituted or unsubstituted C1 to C10 alkyl group, and the aryl group is a substituted or unsubstituted C6 to C20 aryl group.

8. The electrode according to claim 1, wherein: The lithium-containing polyoxazoline includes lithium-containing poly(2-methyl-2-oxazoline), lithium-containing poly(2-ethyl-2-oxazoline), lithium-containing poly(2-propyl-2-oxazoline), lithium-containing poly(2-isopropyl-2-oxazoline), lithium-containing poly(2-cyclopropyl-2-oxazoline) or a combination thereof.

9. The electrode according to claim 1, wherein: The lithium-containing polyoxazoline has a weight average molecular weight M of 500 g / mol to 500,000 g / mol. w .

10. The electrode according to claim 1, wherein: The lithium-containing polyoxazoline has a polydispersity M of 1 to 4. w / M n .

11. The electrode according to claim 1, wherein: The electrode is a negative electrode, and The electrode active material layer is a negative electrode active material layer or a negative electrode coating layer.

12. The electrode according to claim 11, wherein: The electrode active material layer is a negative electrode active material layer, and the negative electrode active material layer includes lithium metal, lithium alloy, carbon-based negative electrode active material, silicon-based negative electrode active material or a combination thereof.

13. The electrode according to claim 11, wherein: The electrode active material layer is a negative electrode coating layer, The negative electrode coating layer comprises a lithium-philic metal, a carbon material, or a combination thereof, and A lithium metal layer is formed between the current collector and the negative electrode coating layer by charging. 14 . A rechargeable lithium battery comprising the electrode according to claim 1 and an electrolyte.

15. The rechargeable lithium battery according to claim 14, in: The electrode according to claim 1 is a negative electrode, and The rechargeable lithium battery also includes a positive electrode facing the negative electrode.

16. The rechargeable lithium battery of claim 14, wherein: The electrode according to claim 1 is a negative electrode, and The rechargeable lithium battery also includes a separator between the positive electrode and the negative electrode.

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