Current collector for rechargeable lithium battery, electrode including same, and rechargeable lithium battery

Abstract

A current collector for a rechargeable lithium battery, an electrode including the current collector, and a rechargeable lithium battery including the current collector are disclosed. A current collector for a rechargeable lithium battery includes a first metal layer, a second metal layer, and a functional layer between the first metal layer and the second metal layer, the functional layer including a polymer and a blowing agent.

Description

Technical Field

[0001] A current collector for a rechargeable lithium battery, an electrode including the current collector, and a rechargeable lithium battery including the current collector are disclosed. Background Technology

[0002] Rechargeable lithium batteries can be recharged, and their energy density per unit weight is three times or more than that of conventional lead-acid, nickel-cadmium, nickel-metal hydride, and nickel-zinc batteries. Rechargeable lithium batteries can also be charged at high rates, and are therefore commercially manufactured for use in laptops, cell phones, power tools, electric bicycles, and more.

[0003] Such rechargeable lithium batteries are typically manufactured by injecting an electrolyte into an electrode assembly, which includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode active material capable of inserting / deintercalating lithium ions, and the negative electrode includes a negative electrode active material capable of inserting / deintercalating lithium ions.

[0004] Currently, with the development of technologies to improve the efficiency and capacity of rechargeable lithium batteries, high-energy-density rechargeable lithium batteries are being used across industries such as IT devices, power tools, and electric vehicles.

[0005] However, when a rechargeable lithium battery with high energy density is deformed due to physical and / or chemical factors (e.g., impact, penetration, overcharging, over-discharging, foreign matter mixing, Li dendrite formation on the negative electrode surface, separator shrinkage, etc.), an electrical short circuit can occur, leading to, for example, thermal runaway and / or explosion. Summary of the Invention

[0006] Some example embodiments include a current collector that reduces or suppresses electrical short circuits, thermal runaway, and / or explosions in rechargeable lithium batteries due to physical and / or chemical factors.

[0007] Some example embodiments include an electrode that includes the current collector of the example embodiments described above.

[0008] Some example embodiments include a rechargeable lithium battery that includes the current collector of the above example embodiments.

[0009] Some example embodiments include a current collector for a rechargeable lithium battery, the current collector including a first metal layer, a second metal layer and a functional layer between the first metal layer and the second metal layer, the functional layer including a polymer and a foaming agent.

[0010] Some example embodiments include an electrode that includes the current collector of the example embodiments described above.

[0011] Some example embodiments include a rechargeable lithium battery comprising: a positive electrode including a positive electrode current collector; a negative electrode including a negative electrode current collector; and an electrolyte between the positive and negative electrodes, wherein at least one of the positive and negative electrode current collectors includes a current collector according to some example embodiments.

[0012] According to some example embodiments, the current collector enables safe operation of rechargeable lithium batteries by reducing or suppressing electrical short circuits, thermal runaway, and / or explosions caused by physical and / or chemical factors. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the mechanism of a conventional current collector during a short circuit.

[0014] Figure 2 This is a schematic diagram illustrating the mechanism during a short circuit of a current collector in some example embodiments.

[0015] Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Detailed Implementation

[0016] Example embodiments will be described in detail below. However, this disclosure is not limited thereto, and is defined by the scope of the claims.

[0017] As used herein, unless otherwise specifically defined, 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 said other element or there may be an intervening element.

[0018] As used herein, the singular may also include the plural unless otherwise specifically defined. Additionally, unless otherwise stated, “A or B” may mean “including A, including B, or including both A and B”.

[0019] As used herein, “combination of” can refer to mixtures, stacks, complexes, copolymers, alloys, blends, and reaction products of the components.

[0020] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it means that the relevant numerical value includes a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0021] current collector Some example embodiments include a current collector for a rechargeable lithium-ion battery, the current collector including a first metal layer, a second metal layer, and a functional layer between the first and second metal layers, the functional layer including a polymer and a blowing agent. The functional layer may have a single-layer structure and a multi-layer structure. A single-layer functional layer may include a layer containing a polymer and a blowing agent, and a multi-layer functional layer may include a polymer layer containing a polymer and a blowing agent layer containing a blowing agent, wherein the blowing agent layer may be positioned at at least one of the first metal layer and the polymer layer, and between the polymer layer and the second metal layer.

[0022] The first metal layer and the second metal layer are respectively configured to transmit current to or from the active material during charging and discharging, and can constitute a commonly known current collector (hereinafter referred to as "conventional current collector 1").

[0023] However, when using conventional current collector 1, electrical short circuits, thermal runaway, and / or explosions of rechargeable lithium batteries will inevitably occur when they deform due to physical and / or chemical factors.

[0024] In this regard, another current collector (hereinafter referred to as "conventional current collector 2") has been proposed in which an intermediate layer made of polymer is inserted between the first metal layer and the second metal layer.

[0025] Reference Figure 1 When the conventional current collector 2 is deformed due to physical and / or chemical factors, the conventional current collector 2 can function as described in 1) and 2) below to reduce or suppress electrical short circuits, thermal runaway and / or explosions of the rechargeable lithium battery.

[0026] 1) First, the intermediate layer made of polymer has high ductility compared to the first and second metal layers. Therefore, when the conventional current collector 2 deforms due to physical and / or chemical factors, the intermediate layer formed of polymer is physically stretched due to thermal shrinkage, while the first and second metal layers break. As a result, the broken portions of the first and second metal layers are electrically isolated.

[0027] 2) Despite the existence of the first mechanism discussed above, a local short circuit can occur in the conventional current collector 2, generating Joule heating, in which the polymer forming the intermediate layer can thermally deform and / or exhibit increased resistance, thereby blocking current transfer between the first metal layer and the second metal layer and reducing or suppressing electrical short circuits, thermal runaway and / or explosions of the rechargeable lithium battery.

[0028] However, even when using conventional current collector 2, as rechargeable lithium batteries achieve increasingly higher energy densities, electrical short circuits, thermal runaway, and / or explosions occur more rapidly. In other words, as the energy density of rechargeable lithium batteries increases, current collectors with faster responsiveness become advantageous.

[0029] Therefore, some example embodiments include a current collector (hereinafter referred to as "current collector of some example embodiments") comprising an intermediate layer of foaming agent and polymer (hereinafter referred to as "functional layer") inserted between the first metal layer and the second metal layer.

[0030] Compared to conventional current collector 2, the current collectors of some example embodiments not only have the advantages of conventional current collector 2 discussed above (1) and (2) by including a polymer in the functional layer, but also have the following additional advantages discussed below (3) and (4) by further including a foaming agent in the functional layer.

[0031] 3) The current collectors of some example embodiments have a faster responsiveness than conventional current collector 2. When the current collector according to some example embodiments has a local short circuit that generates Joule heating, the blowing agent can be activated (e.g., foaming) much faster than the thermal shrinkage of the polymer. For example, based on the time it takes for Joule heating to occur, the thermal shrinkage of the polymer will begin within minutes, but the activation of the blowing agent can begin within seconds.

[0032] 4) The volume of the material obtained by foaming with a foaming agent (hereinafter referred to as "foam") can be approximately 1.1 to approximately 300 times larger than its volume before foaming with the foaming agent. Such a large foam can remedy or fix deformed portions of the current collector that have experienced partial short circuits, and also prevent or deter potential risks such as electrolyte leakage.

[0033] In short, according to some example embodiments, the current collector can reduce or suppress electrical short circuits, thermal runaway, and / or explosions of rechargeable lithium batteries caused by physical and / or chemical factors by inserting a functional layer comprising a foaming agent and a polymer between two different current collectors (i.e., a first metal layer and a second metal layer).

[0034] Therefore, the current collector according to some example embodiments can enable safe operation of the rechargeable lithium battery when applied to at least one of the positive and negative electrodes. These effects of the current collector according to some example embodiments remain effective even as the energy density of the rechargeable lithium battery increases.

[0035] The current collectors of some example embodiments will be described in more detail below.

[0036] foaming agent The foaming agent in the functional layer is activated (e.g., foamed) by Joule heating generated in the current collector in some example embodiments, thereby remedying or fixing the deformed phase of the current collector that has experienced a partial short circuit, and hindering or preventing potential hazards such as electrolyte leakage.

[0037] The foaming agent in the functional layer may be or include at least one of physical foaming agents, chemical foaming agents, or combinations thereof.

[0038] Physical foaming agents can be activated (e.g., foaming) through phase change, and may include aliphatic hydrocarbons, fluorinated aliphatic hydrocarbons, or combinations thereof.

[0039] Physical foaming agents may include or include expanded graphite, methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, methanol, ethanol, n-propanol, isopropanol, fluoromethane, perfluoromethane, fluoroethane, 1,1-difluoroethane, trifluoroethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, difluoromethane, perfluoroethane, 2,2-difluorobutane, perfluorocyclobutane, chloromethane, dichloromethane, chloroethane, 1,1,1-trichloroethane, 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-dichloroethane, and others. The first of the following: fluoroethane (HCFC-142b), dichlorofluoromethane (HCFC-22), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124), trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trichlorotrifluoroethane (CFC-113), 1,1,1-trifluoroethane, pentafluoroethane, dichlorotetrafluoroethane (CFC-114), heptafluoropropane, dichlorohexafluoropropane, or combinations thereof.

[0040] When forming functional layers by solvent casting, the pre-foaming of physical foaming agents can be reduced or suppressed by using different types of polymers to encapsulate them.

[0041] Chemical foaming agents can be activated through chemical reactions (e.g., foaming) and are classified into inorganic chemical foaming agents and organic chemical foaming agents according to their composition.

[0042] Inorganic chemical foaming agents may include at least one of sodium bicarbonate (NaHCO3), ammonium bicarbonate (NH4HCO3), sodium borohydride (NaBH4), or combinations thereof.

[0043] Organic chemical foaming agents may include at least one of acylhydrazide, azodicarbonamide, p,p'-oxobis(benzenesulfonylhydrazide), dinitrospentamethylenetetramine, copolymers thereof, polymers thereof, or combinations thereof.

[0044] For example, expanded graphite can be a foaming agent. Compared with other foaming agents, graphite before expansion has a conductivity of approximately 3.33 Å in d-spacing, and thus, in addition to compensating for the insufficient conductivity of the thin-film coated metal layer, the planar spacing of the graphite layer increases to tens to hundreds of μm during expansion. With high expansion, this has the advantage of inducing a sharp decrease in the conductivity of expanded graphite.

[0045] polymer As a polymer in the functional layer, polymers with desired or advantageous electrical insulation properties and chemical resistance can be used.

[0046] Ideally, the polymer can have an elongation of about 1% to about 2.0% higher than that of the first and second metal layers, but can have a heat distortion temperature lower than that of the electrolyte.

[0047] Polymers possessing the above properties may be or include thermoplastic resins. For example, thermoplastic resins may be or include at least one of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), or combinations thereof.

[0048] The polymer may have a thickness non-uniformity of about 0.01% to about 7.5%, about 0.05% to about 5.0%, or about 0.1% to about 4.0% in the longitudinal (MD direction). When the thickness non-uniformity exceeds the above ranges, there is a risk of insulation breakdown, tearing, and appearance deterioration, which may cause reduced electrode yield, reduced battery capacity, and / or short circuits, thereby reducing the reliability of rechargeable lithium batteries.

[0049] The intrinsic viscosity of the polymer, measured according to ASTM D4603-03, can be from about 0.01 dL / g to about 5 dL / g, from about 0.1 dL / g to about 3 dL / g, or from about 0.6 dL / g to about 1.0 dL / g. Within this range, the functional layers of the polymer can be molded into film form.

[0050] The weight ratio of the blowing agent to the polymer in the functional layer can be in the range of about 0.1:99.9 to about 20:80, about 0.2:99.8 to about 15:85, or about 0.5:99.5 to about 10:90. Within any of these ranges, the effect of the blowing agent and the polymer can be increased.

[0051] plasticizer Plasticizers can be added to the functional layers to control elongation.

[0052] Plasticizers may be or include at least one of glycerol, ethylene glycol, polyethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, propylene, ethylene, ethyl phthalate, copolymers thereof, polymers thereof, or combinations thereof.

[0053] The weight ratio of plasticizer to polymer in the functional layer can be in the range of about 10:90 to about 0.1:99.9, about 5:95 to about 0.2:99.8, or about 2:98 to 0.5:about 99.5. Within any of these ranges, the elongation of the functional layer can be increased compared to before the addition of the plasticizer.

[0054] Metal layers (first metal layer and second metal layer) The first metal layer and the second metal layer can both be conductive layers, which can conduct electricity in the surface direction and can be non-conductive in the thickness direction.

[0055] For example, the first metal layer and the second metal layer may each independently include at least one of aluminum (Al), nickel (Ni), copper (Cu), iron (Fe), or a combination thereof.

[0056] For a more detailed example, when the current collector of some example embodiments is applied to the positive electrode, aluminum (Al) may be a first metal layer and a second metal layer, and when the current collector of some example embodiments is applied to the negative electrode, copper (Cu) may be a first metal layer and a second metal layer.

[0057] The thickness ratio of the first metal layer to the second metal layer can be from about 3:7 to about 7:3, or from about 4:6 to about 6:4. For example, the first metal layer and the second metal layer can have the same thickness.

[0058] The sum of the thicknesses of the first metal layer and the second metal layer can be less than or equal to approximately 70% of the total thickness of the current collector (100%), or less than or equal to approximately 65% ​​of the total thickness of the current collector (100%). Within any of the above ranges, the effects of the first metal layer and the second metal layer, as well as the effects of the functional layer, can be coordinated.

[0059] The sheet resistance of the current collector can vary depending on the thickness of the metal layer. For example, when the current collector has only a metal layer and no functional layer, the sheet resistance of the metal layer can be less than about 0.01 mΩ / sq. On the other hand, the sheet resistance of a current collector including a first metal layer and a second metal layer can be greater than or equal to about 0.01 mΩ / sq, and can increase as the thickness of the first metal layer and the second metal layer decreases to reach about 12.4 mΩ / sq.

[0060] The sheet resistance of a current collector can typically be measured using a 4-point probe device that can measure the sheet resistance of a bulk thin film.

[0061] The first and second metal layers can be formed by deposition, coating, lamination, electroplating, etc.

[0062] Adhesive layer An adhesive layer may also be included at the interface between the first metal layer and / or the second metal layer and the functional layer.

[0063] The adhesive layer can improve the adhesion and weldability between the polymer in the functional layer and the first and / or second metal layers. The high bonding energy of the metal-oxygen at the atomic level can enhance the interfacial adhesion, and the adhesion can be proportional to the atomic content of lone pair electrons in the functional layer (desirably based on metal-OC bonds).

[0064] The adhesive layer can be formed by physically and / or chemically functionalizing the surface of the functional layer using monomers, copolymers, polymers or combinations thereof containing a large number of highly electronegative atoms (e.g., polymethyl methacrylate (PMMA), polycarbonate (PC), polyamide (PA), polyether ether ketone (PEEK), polyether imide (PEI), acrylonitrile-butadiene-styrene (ABS) or combinations thereof, including carbonyl groups).

[0065] In particular, plasma treatment or corona discharge treatment for chemical functionalization enables uniform treatment of the film surface and can improve the effect depending on the type of gas in the treatment atmosphere. Nitrogen, oxygen, argon, silane, carbon dioxide, etc., can be gases used in this atmosphere, but a mixture of gases containing oxygen and / or nitrogen is desirable. Through plasma treatment, at least one of ether, carbonyl, ester, carboxyl, hydroxyl, and amide groups is uniformly functionalized on the film surface, thereby improving the uniform adhesion of various metal and alloy layers, including aluminum and copper, to the electrode and improving the reliability of the electrode.

[0066] For example, a first adhesive layer may be further included between the first metal layer and the functional layer, a second adhesive layer may be further included between the second metal layer and the functional layer, or both the first adhesive layer and the second adhesive layer may be further included.

[0067] Electrodes and rechargeable lithium batteries Some example embodiments provide an electrode that includes the current collector of the above example embodiments.

[0068] Electrodes can be or include positive or negative electrodes.

[0069] Some example embodiments include a rechargeable lithium battery comprising: a positive electrode including a positive electrode current collector; a negative electrode including a negative electrode current collector; and an electrolyte between the positive and negative electrodes, wherein at least one of the positive and negative electrode current collectors includes the current collector of the above example embodiments.

[0070] In other words, in a rechargeable lithium battery, the current collector in some example embodiments can be used as a positive electrode current collector, a negative electrode current collector, or both a positive electrode current collector and a negative electrode current collector.

[0071] In the following text, without repeating descriptions, the electrodes and rechargeable lithium batteries including the current collectors of the above example embodiments will be described in detail.

[0072] Positive electrode active material The positive electrode active material can be or includes compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). Specifically, one or more types of composite oxides of lithium and at least one of metals including cobalt, manganese, nickel, and combinations thereof can be used.

[0073] The composite oxide can be or includes lithium transition metal composite oxides, and specific examples may include at least one of lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof.

[0074] 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 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 eO2 (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); and Li a FePO4 (0.90≤a≤1.8).

[0075] In the above chemical formulas, A is or includes at least one of Ni, Co, Mn, or a combination thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is or includes at least one of O, F, S, P, or a combination thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 It is or includes at least one of Mn, Al, or combinations thereof.

[0076] The positive electrode active material may be or include at least one of the following: lithium nickel oxide represented by chemical formula 11, lithium cobalt oxide represented by chemical formula 12, lithium iron phosphate compound represented by chemical formula 13, cobalt-free lithium nickel manganese oxide represented by chemical formula 14, or combinations thereof.

[0077] Chemical Formula 11: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In chemical formula 11, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.7, 0 ≤ z1 ≤ 0.7, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M1 and M 2 Each of them independently comprises or includes one or more of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X comprises or includes one or more of F, P, and S.

[0078] In chemical formula 11, 0.6≤x1≤1, 0≤y1≤0.4 and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2 and 0≤z1≤0.2.

[0079] Chemical formula 12: Li a2 Co x2 M 3 y2 O 2-b2 X b2 In chemical formula 12, 0.9 ≤ a² ≤ 1.8, 0.7 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.3, 0.9 ≤ x² + y² ≤ 1.1, and 0 ≤ b² ≤ 0.1, M 3 X is or includes one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0080] Chemical formula 13: Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 In chemical formula 13, 0.9 ≤ a³ ≤ 1.8, 0.6 ≤ x³ ≤ 1, 0 ≤ y³ ≤ 0.4, and 0 ≤ b³ ≤ 0.1, M 4 X is or includes one or more of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0081] Chemical formula 14: Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4 In Chemical Formula 14, 0.9 ≤ a4 ≤ 1.8, 0.8 ≤ x4 < 1, 0 < y4 ≤ 0.2, 0 ≤ z4 ≤ 0.2, 0.9 ≤ x4 + y4 + z4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 5 is or includes one or more of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is or includes one or more of F, P, and S.

[0082] As an example, the positive electrode active material may be or include a high-nickel type positive electrode active material. Based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content of the high-nickel type positive electrode active material is 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%. The high-nickel type positive electrode active material can achieve high capacity and can be applied to high-capacity and high-density rechargeable lithium batteries.

[0083] positive electrode The positive electrode for a rechargeable lithium battery may include a current collector and a positive electrode active material layer on the current collector. The positive electrode active material layer may include a positive electrode active material and may also include a binder and / or a conductive material.

[0084] For example, the positive electrode may further include an additive that can be used as a sacrificial positive electrode.

[0085] Based on 100 wt% of the positive electrode active material layer, the amount of the positive electrode active material may be about 90 wt% to about 99.5 wt%, and the amount of each of the binder and the conductive material may be about 0.5 wt% to about 5 wt%.

[0086] The binder is configured to attach the positive electrode active material particles to each other and also attach the positive electrode active material to the current collector. Examples of the binder may include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc., but are not limited thereto.

[0087] A conductive material can be configured to impart conductivity (e.g., electrical conductivity) to an electrode. Any material that does not cause a chemical change (e.g., does not cause an undesirable chemical change in a rechargeable lithium battery) and conducts electrons can be used in a battery. Examples of conductive materials can include: carbonaceous materials such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metallic materials including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof. Al can be a current collector, but is not limited thereto, and the current collector of the above exemplary embodiments can be used. In the latter case, the first metal layer and the second metal layer can use aluminum (Al).

[0088] Negative electrode active material The negative electrode active material can be or include at least one of a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0089] The material that reversibly intercalates / deintercalates lithium ions can include a carbonaceous negative electrode active material, e.g., crystalline carbon, amorphous carbon, or a combination thereof. Crystalline carbon can be or include graphite, such as natural graphite or artificial graphite that is non-shaped, plate-like, flaky, spherical, or fibrous. Amorphous carbon can be or include at least one of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0090] The lithium metal alloy can include lithium and a metal containing at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0091] The material capable of doping / dedoping lithium can be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof). The Sn-based negative electrode active material can include Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0092] Silicon-carbon composites can be or include composites of silicon and amorphous carbon. According to some example 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, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated, and an amorphous carbon coating layer (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the primary silicon particles; for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed within an amorphous carbon matrix.

[0093] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0094] Si-based or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0095] negative electrode The negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0096] For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder and about 0.5 wt% to about 5 wt% of conductive material.

[0097] The binder can be configured to adhere the negative electrode active material particles to each other and also to the negative electrode active material in the current collector. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0098] Non-aqueous adhesives may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0099] The waterborne adhesive may be or include at least one of 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)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0100] When the aqueous binder is a negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. The cellulose-based compound includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or their alkali metal salts. The alkali metal may be or include at least one of Na, K, or Li.

[0101] The dry binder may be or include a polymeric material that can be fibrous, and may be or include at least one of, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0102] Conductive materials are included to provide electrode conductivity, and any conductive material may be conductive unless it causes a chemical change. Examples of conductive materials may include or include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metallic materials, such as at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0103] The negative electrode current collector may include, but is not limited to, at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof, and current collectors according to some example embodiments may be used. In the latter case, the first metal layer and the second metal layer may include copper (Cu).

[0104] electrolyte Electrolytes used in rechargeable lithium batteries include non-aqueous organic solvents and lithium salts.

[0105] Non-aqueous organic solvents constitute the medium for transporting ions that participate in the electrochemical reactions of the battery.

[0106] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0107] Carbonate solvents may include at least one of 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), and butyl carbonate (BC). Ester solvents may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, and caprolactone. Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include at least one of ethanol, isopropanol, etc., and aprotic solvents may include: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may include double bonds, aromatic rings or ether groups); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane or 1,4-dioxolane; sulfolane, etc.

[0108] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0109] In addition, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0110] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(sulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 One or more of the following: (SO2) (x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate) phosphate (LiDFBOP), lithium difluorobis(oxalate) borate (LiDFBOB), and lithium bis(oxalate) borate (LiBOB).

[0111] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer membrane of two or more layers thereof, as well as at least one of mixed multilayer membranes such as polyethylene / polypropylene two-layer membranes, polyethylene / polypropylene / polyethylene three-layer membranes, polypropylene / polypropylene / polypropylene three-layer membranes, etc.

[0112] The membrane may include a porous substrate and a coating layer on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials or combinations thereof.

[0113] The porous substrate may be or include a polymer membrane, which is formed or includes any one or more of the following polymers, copolymers of two or more of them, or mixtures thereof: polyolefins (such as polyethylene or polypropylene), polyesters (such as polyethylene terephthalate or polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and Teflon (polytetrafluoroethylene).

[0114] Organic materials may include polyvinylidene fluoride polymers or (meth)acrylic acid polymers.

[0115] Inorganic materials may include inorganic particles, which include at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but are not limited thereto.

[0116] Organic and inorganic materials can be mixed in a single coating layer, or coating layers comprising organic materials and coating layers comprising inorganic materials can be stacked.

[0117] Rechargeable lithium batteries Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries. Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 3 A cylindrical battery is shown. Figure 4 A prismatic battery is shown, and Figure 5 and Figure 6 A pouch-type battery is shown. (See reference) Figures 3 to 6The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50 therein, wherein the electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50, such as... Figure 3 As shown. Additionally, in Figure 4 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive terminal 12, a negative electrode lead connector 21, and a negative terminal 22. For example... Figure 5 and Figure 6 As shown, the rechargeable lithium battery 100 includes Figure 6 The electrode terminals 70 shown are Figure 5 The positive electrode terminal 71 and negative electrode terminal 72 shown herein form an electrical path for guiding the current generated in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0118] The rechargeable lithium battery according to some example embodiments can be used in automobiles, mobile phones and / or various types of electrical devices, but this disclosure is not limited thereto.

[0119] Examples and comparative examples of this disclosure are described below. However, these examples should not be construed in any way as limiting the scope of the disclosure.

[0120] Example 1 (1) Manufacturing of positive electrode current collector Polyethylene terephthalate (PET) with an intrinsic viscosity of 0.70 dL / g was used as the polymer, and expanded graphite was used as the foaming agent.

[0121] A polymer and a blowing agent in a weight ratio of 98:2 were mixed in dimethyl sulfoxide (DMSO) solvent and then used to form a functional layer (thickness: 7.8 μm) as a monolayer film by solvent casting. Subsequently, in order to improve the adhesion between each of the first and second metal layers and the polymer in the functional layer, the functional layer was subjected to plasma treatment under a nitrogen atmosphere.

[0122] Reduced to 10 -5 Torr to 10 -6 In the vacuum atmosphere of Torr, an electric field is applied to an aluminum wire to vaporize it, depositing aluminum layers (each layer thickness: 1.1 μm) on one and another surface of the functional layer. The aluminum layer deposited on one surface of the functional layer is called the first metal layer, and the other aluminum layer deposited on the other surface of the functional layer is called the second metal layer.

[0123] While an electric field is applied and the functional layer rotates in the MD direction, the first metal layer and the second metal layer are deposited at deposition rates of 3 Å / s to 4 Å / s, respectively, until the first metal layer and the second metal layer reach their respective target thicknesses.

[0124] On the other hand, pinholes inevitably form in the functional layers. Therefore, to short-circuit the electrical connection between the first and second metal layers through the pinholes, an electric field is applied between the two different metal layers. Furthermore, the electric field is applied to any two points within the same metal layer to strengthen the connection between the metal particles constituting each of the first and second metal layers, thereby improving the reliability of the metal layers.

[0125] (2) Manufacturing of the positive electrode LiNi will be used as the active material for the positive electrode. 0.75 Mn 0.23 Al 0.02 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material are mixed in a weight ratio of 96:3:1 and then dispersed in N-methylpyrrolidone to prepare a slurry of positive electrode active material.

[0126] The positive electrode active material slurry is coated onto the positive electrode current collector, and then dried and pressed at 110°C to manufacture the positive electrode.

[0127] (3) Manufacturing of the negative electrode The negative electrode active material was prepared by mixing artificial graphite and silicon particles in a weight ratio of 93.5:6.5, and the negative electrode active material, styrene-butadiene rubber binder, and carboxymethyl cellulose were mixed in a weight ratio of 97:1:2 and then dispersed in distilled water to prepare a negative electrode active material slurry.

[0128] The negative electrode active material slurry was coated onto a 10 μm thick Cu foil, then dried and pressed at 100 °C to manufacture the negative electrode.

[0129] (4) Preparation of electrolyte An electrolyte was prepared by mixing ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) in a volume ratio of 20:40:40 to prepare a carbonate solvent and dissolving 1.5 M lithium salt (LiPF6) in the carbonate solvent.

[0130] (5) Manufacturing of rechargeable lithium battery cells The positive and negative electrodes are assembled with a 25 μm thick polyethylene separator to manufacture an electrode assembly. The electrode assembly is housed in a prismatic housing and an electrolyte is injected into it to manufacture a rechargeable lithium battery cell.

[0131] Example 2 The positive electrode current collector, positive electrode, and rechargeable lithium battery cell of Example 2 are manufactured in the same manner as in Example 1, except that the thickness of each of the first metal layer and the second metal layer is changed to 1.8 μm, and the thickness of the functional layer in the form of a single-layer film is changed to 6.4 μm.

[0132] Example 3 The positive electrode current collector, positive electrode, and rechargeable lithium battery cell of Example 3 are manufactured in the same manner as in Example 1, except that the thickness of each of the first metal layer and the second metal layer is changed to 1.9 μm, and the thickness of the functional layer in the form of a single-layer film is changed to 6.2 μm.

[0133] Example 4 The positive electrode current collector, positive electrode, and rechargeable lithium battery cell of Example 4 are manufactured in the same manner as in Example 1, except that the thickness of each of the first metal layer and the second metal layer is changed to 2.1 μm, and the thickness of the functional layer in the form of a single film is changed to 5.8 μm.

[0134] Example 5 The positive electrode current collector, positive electrode, and rechargeable lithium battery cell of Example 5 are manufactured in the same manner as in Example 1, except that the thickness of each of the first metal layer and the second metal layer is changed to 3.1 μm, and the thickness of the functional layer in the form of a single-layer film is changed to 3.8 μm.

[0135] Example 6: Functional layer with multi-layer structure The positive electrode current collector, positive electrode, and rechargeable lithium battery cell of Example 6 are manufactured in the same manner as in Example 1, except that the polyethylene terephthalate (PET) with an intrinsic viscosity of 0.70 dL / g is replaced with a polymer monolayer with a thickness of 3.8 μm, and a 1 μm thick foamed functional layer including expanded graphite is disposed between the first metal layer, the second metal layer, and the polymer monolayer.

[0136] A foamed functional layer (thickness: 1 μm) was formed by mixing a polymer and a foaming agent in a dimethyl sulfoxide (DMSO) solvent at a weight ratio of 20:80 and then using a solvent casting method. The obtained foamed functional layer was laminated with a plasma-treated polymer monolayer to form a multilayer structure of foamed functional layer / PET film / foamed functional layer.

[0137] Example 7: Cases that also include an adhesive layer The positive electrode current collector, positive electrode, and rechargeable lithium battery cell of Example 7 are manufactured in the same manner as in Example 1, except that a separate organic-metal adhesive layer is added to the functional layer.

[0138] Organometallic adhesive layers are formed by preparing a 2 wt% acrylonitrile-butadiene-styrene (ABS) solution using acetone as a solvent, and coating the 2 wt% acrylonitrile-butadiene-styrene (ABS) solution onto a plasma-treated functional layer to form each organometallic adhesive layer with a thickness of 0.8 μm.

[0139] Compare with Example 1 (for reference) A 14 μm thick Al foil was used as the positive electrode current collector.

[0140] Under the aforementioned differences, the positive electrode and rechargeable lithium battery cell of Comparative Example 1 are manufactured in the same manner as in Example 1.

[0141] Comparison Example 2 The positive electrode current collector, positive electrode, and rechargeable lithium battery cell of Comparative Example 2 were manufactured in the same manner as in Example 1, except that a foaming agent was not used. For reference, the thickness ratio of the first metal layer:functional layer:second metal layer and the sheet resistance of the positive electrode current collector of Examples 1 to 7, as well as Comparative Examples 1 and 2, are summarized in Table 1.

[0142] The sheet resistance of the positive electrode current collector was measured using a four-point probe setup typically used for measuring sheet resistance of bulk thin films. Here, the four-point probe consists of a single row of four probes spaced 1 mm apart, and the measurement temperature is 25°C.

[0143] Table 1:

[0144] In Table 1, * indicates the foamed functional layer (PET: expanded graphite = 20:80 (wt:wt)). ** indicates an organic-metal adhesive layer.

[0145] Evaluation Example 1: Evaluation of Positive Electrode Current Collector The characteristics of the positive electrode current collectors of Examples 1 to 7, as well as Comparative Examples 1 and 2, were evaluated using the following method, and the results are shown in Table 2.

[0146] (1) Elongation Elongation was measured using a UTM 6800 device manufactured by Instron, in accordance with the standard test method ASTM D882.

[0147] (2) Puncture strength Puncture strength was measured using a UTM 6800 device manufactured by Instron, according to the standard test method ASTM F1306.

[0148] Evaluation Example 2: Evaluation of Rechargeable Lithium-ion Battery Cells The lifetime characteristics of the rechargeable lithium battery cells of Examples 1 to 7, as well as Comparative Examples 1 and 2, were evaluated using the following method, and the results are shown in Table 2.

[0149] The rechargeable lithium battery cells were subjected to 200 charge-discharge cycles under the conditions of 0.33C charging (constant current (CC) / constant voltage (CV), 4.45V, 0.025C cutoff) / 1.0C discharging (constant current (CC), 2.5V cutoff) and 25°C to calculate the capacity retention rate according to Equation 1.

[0150] Equation 1: Capacity retention [%] = (Discharge capacity after 200 cycles / Discharge capacity after the first cycle) × 100 Table 2:

[0151] Referring to Table 2, and based on Comparative Examples 1 and 2, there appears to be a trade-off between elongation, puncture strength, and volume retention. However, compared to Comparative Examples 1 and 2, Examples 1 through 7 exhibit appropriate volume retention (95% or greater) while simultaneously demonstrating elongation and puncture strength that meet their respective desired ranges (7.0% or greater elongation and 660% or greater puncture strength, respectively).

[0152] Therefore, the current collectors according to some example embodiments, represented by Examples 1 to 7, reduce or suppress electrical short circuits, thermal runaway, and / or explosions caused by physical and / or chemical factors by inserting a functional layer comprising a foaming agent and a polymer between two different current collectors (e.g., a first metal layer and a second metal layer).

[0153] On the other hand, Examples 1 to 7 exhibit capacity retention, elongation, and puncture strength that vary depending on the thickness of each of the metal layer and the functional layer, the structure of the functional layer, etc. Therefore, various desired properties of current collectors and rechargeable lithium batteries can be achieved by adjusting the capacity retention, elongation, and puncture strength according to the thickness of each of the metal layer and the structure of the functional layer, etc.

[0154] Here, for convenience, the current collector is manufactured as a positive electrode current collector, but even when manufactured as a negative electrode current collector, the same desired or advantageous performance as in Examples 1 to 7 can be achieved.

[0155] Therefore, the current collector according to some example embodiments is applied to at least one of the positive and negative electrodes, which enables the rechargeable lithium battery cell to operate safely. This effect of the current collector according to some example embodiments remains effective even when the energy density of the rechargeable lithium battery increases.

[0156] In addition, referring to Examples 1 to 7, the effect can be controlled by adjusting the weight ratio of foaming agent to polymer in the functional layer, the thickness ratio of the first metal layer to the functional layer to the second metal layer, etc.

[0157] While this disclosure has been described in conjunction with what are now considered to be exemplary embodiments, it will be understood that the disclosure is not limited to the disclosed exemplary embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0158] Description of reference numerals in the attached figures 100: Rechargeable lithium battery 10: Positive electrode 11: Positive electrode lead connector 12: Positive extreme 20: Negative electrode 21: Negative electrode lead connector 22: Negative extreme 30: Diaphragm 40: Electrode assembly 50: Casing 60: Sealing component 70: Electrode connector 71: Positive electrode connector 72: Negative electrode connector.

Claims

1. A current collector for a rechargeable lithium battery, the current collector comprising: First metal layer; Second metal layer; as well as A functional layer, located between the first metal layer and the second metal layer, comprises a polymer and a foaming agent.

2. The current collector according to claim 1, wherein, The functional layer has one of a single-layer structure or a multi-layer structure.

3. The current collector according to claim 2, wherein, The functional layer having a single-layer structure includes a layer comprising the polymer and the foaming agent.

4. The current collector according to claim 2, wherein, The functional layer having a multi-layered structure includes: Polymer layer, comprising the polymer; and The foaming agent layer includes the foaming agent. The foaming agent layer is located at at least one of the first metal layer and the polymer layer and the polymer layer and the second metal layer.

5. The current collector according to claim 1, wherein, The foaming agent includes at least one of physical foaming agents, inorganic chemical foaming agents, and organic chemical foaming agents.

6. The current collector according to claim 5, wherein, The physical foaming agent includes expanded graphite, methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, methanol, ethanol, n-propanol, isopropanol, fluoromethane, perfluoromethane, fluoroethane, 1,1-difluoroethane, trifluoroethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, difluoromethane, perfluoroethane, 2,2-difluorobutane, perfluorocyclobutane, chloromethane, dichloromethane, and chloroethane. At least one of 1,1,1-trichloroethane, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoroethane, dichlorofluoromethane, 1,1-dichloro-2,2,2-trifluoroethane, 1-chloro-1,2,2,2-tetrafluoroethane, trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, 1,1,1-trifluoroethane, pentafluoroethane, dichlorotetrafluoroethane, heptafluoropropane, and dichlorohexafluoropropane.

7. The current collector according to claim 5, wherein, The inorganic chemical foaming agent includes at least one of sodium bicarbonate, ammonium bicarbonate, and sodium borohydride.

8. The current collector according to claim 5, wherein, The organic chemical foaming agent includes at least one of acylhydrazide, azodicarbonamide, p,p'-oxobis(benzenesulfonylhydrazide), dinitrospentamethylenetetramine, copolymers thereof, and polymers thereof.

9. The current collector according to claim 1, wherein, The polymer includes thermoplastic resins.

10. The current collector according to claim 9, wherein, The thermoplastic resin includes at least one of polypropylene, polyethylene, and polyethylene terephthalate.

11. The current collector according to claim 1, wherein, The weight ratio of the foaming agent to the polymer in the functional layer is in the range of 0.1:99.9 to 20:

80.

12. The current collector according to claim 1, wherein, Both the first metal layer and the second metal layer independently comprise at least one of aluminum, nickel, copper, and iron.

13. The current collector according to claim 1, wherein, The thickness ratio of the first metal layer to the second metal layer is 3:7 to 7:

3.

14. The current collector according to claim 1, wherein, The sum of the thicknesses of the first metal layer and the second metal layer is less than or equal to 70% of the total thickness of the current collector.

15. The current collector according to claim 1, wherein, The current collector has a sheet resistance in the range of 0.01 mΩ / sq to 12.4 mΩ / sq.

16. The current collector according to claim 1, wherein, An adhesive layer is further included at least at one of the interfaces between the first metal layer and the functional layer and between the second metal layer and the functional layer.

17. The current collector according to claim 16, wherein, The adhesive layer comprises at least one of polymethyl methacrylate, polycarbonate, polyamide, polyetheretherketone, polyetherimide, and acrylonitrile-butadiene-styrene containing carbonyl groups.

18. An electrode comprising the current collector according to claim 1.

19. A rechargeable lithium battery, said rechargeable lithium battery comprising: Positive electrode, including positive electrode current collector; Negative electrode, including negative electrode current collector; as well as Electrolyte, located between the positive and negative electrodes. Wherein, at least one of the positive electrode current collector and the negative electrode current collector includes the current collector according to claim 1.

20. The rechargeable lithium battery according to claim 19, further comprising: A diaphragm is impregnated with the electrolyte between the positive electrode and the negative electrode.

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