Negative current collector for lithium-free battery, electrode assembly including the same, and lithium-free battery

Abstract

The negative electrode current collector for a lithium-free battery according to an embodiment of the present disclosure is a negative electrode current collector for a lithium-free battery, and the negative electrode current collector includes: a metal current collecting substrate; a conductive layer formed on at least one surface of the metal current collecting substrate and including a conductive material; and an auxiliary layer formed on the conductive layer and increasing the electrodeposition density of lithium.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application Nos. 10-2020-0055156, filed on May 8, 2020, and 10-2021-0008512, filed on January 21, 2021, the disclosures of which are incorporated herein by reference in their entireties.

[0003] The present disclosure relates to a negative electrode current collector for a lithium-free battery, an electrode assembly including the negative electrode current collector for a lithium-free battery, and a lithium-free battery. Background Art

[0004] Due to the rapid increase in the use of fossil fuels, there is an increasing demand for using alternative or clean energy, and the most active research area is the field of power generation and power storage using electrochemistry.

[0005] Currently, secondary batteries are representative examples of electrochemical devices that utilize this electrochemical energy, and their range of use tends to gradually expand.

[0006] In recent years, with the increase in the development of technologies and demands for mobile devices such as laptop computers, mobile phones, and cameras, the demand for secondary batteries as an energy source has increased rapidly. Among such secondary batteries, many studies have been conducted on lithium secondary batteries that exhibit high energy density and working voltage, have a long cycle life, and a low self-discharge rate, and they have been commercialized and widely used.

[0007] Generally, a lithium secondary battery has a structure in which a non-aqueous electrolyte is impregnated into an electrode assembly including a positive electrode, a negative electrode, and a porous separator. In addition, generally, the positive electrode is prepared by coating a positive electrode mixture including a positive electrode active material on an aluminum foil, and the negative electrode is prepared by coating a negative electrode mixture including a negative electrode active material on a copper foil.

[0008] Generally, a lithium transition metal oxide is used as the positive electrode active material, and a carbon-based material is used as the negative electrode active material.

[0009] However, recently, lithium metal batteries using lithium metal itself as the negative electrode active material have been commercialized. In addition, active research is being conducted on lithium-free batteries in which only a current collector is used as the negative electrode during the preparation of the electrode, lithium is provided from the positive electrode through discharge, and the resulting lithium metal is used as the negative electrode active material. From the perspective of high energy density, lithium-free batteries are considered a battery concept that can achieve the highest energy density.

[0010] However, in the negative electrode made only of a current collector, a lithium layer is formed by electrodeposition due to charging. At this time, a lithium layer with a low electrodeposition density is formed on the current collector, and the side reaction of the electrolyte is severe, resulting in rapid deterioration of the life characteristics.

[0011] Therefore, it is necessary to develop a current collector for the negative electrode of a lithium-free battery that can solve the above problems. SUMMARY OF THE INVENTION

[0012] Technical problem

[0013] The present disclosure aims to solve the above problems and other unsolved technical problems.

[0014] Specifically, an object of the present disclosure is to provide a current collector for a negative electrode in which a lithium layer with a high electrodeposition density can be formed by a simpler method.

[0015] Another object of the present disclosure is to prevent side reactions of the electrolyte of a lithium-free battery using the current collector for the negative electrode, thereby improving the life characteristics.

[0016] Technical solution

[0017] To achieve the above object, according to an embodiment of the present disclosure, there is provided a current collector for a negative electrode of a lithium-free battery, the current collector for the negative electrode including: a metal current collecting substrate; a conductive layer formed on at least one surface of the metal current collecting substrate and including a conductive material; and an auxiliary layer formed on the conductive layer and increasing the electrodeposition density of lithium.

[0018] The metal current collecting substrate may be at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, aluminum-cadmium alloy, copper surface-treated with a different metal, and stainless steel surface-treated with a different metal.

[0019] The metal current collecting substrate may be a metal containing copper.

[0020] The conductive layer may be a primer layer, a conductive polymer layer, or a conductive epoxy layer.

[0021] The primer layer may include a conductive material and an adhesive material, and the conductive material may include at least one selected from the group consisting of natural graphite, artificial graphite, graphene, carbon black, channel black, furnace black, lamp black, thermal crack carbon black, carbon nanotubes, graphite nanofibers, carbon nanofibers, aluminum, nickel, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives.

[0022] The conductive polymer layer may include at least one conductive polymer selected from the group consisting of poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate / ester) (PEDOT / PSS), polyaniline (PANI), polypyrrole (PPy), polythiophene (PT), polyacetylene (PA), and poly(p-phenylenevinylene) (PPV).

[0023] The conductive epoxy layer may include a conductive filler and an adhesive, and the conductive filler may include at least one selected from the group consisting of metal powders of gold, platinum, silver, copper, or nickel, carbon or carbon fibers, graphite, and composite powders.

[0024] The auxiliary layer may include a carbonaceous material, a lithium metal oxide, a metal compound capable of alloying with lithium, a metal oxide, a lithium-metal alloy, or a mixture of two or more thereof.

[0025] The auxiliary layer may further include an adhesive.

[0026] The total thickness of the conductive layer and the auxiliary layer may be in the range of 0.1 μm to 60 μm.

[0027] The thickness of the conductive layer may be in the range of 0.1 μm to 20 μm.

[0028] The thickness of the auxiliary layer may be in the range of 0.1 μm to 40 μm.

[0029] The total thickness of the conductive layer and the auxiliary layer may be in the range of 2 μm to 20 μm.

[0030] According to another embodiment of the present disclosure, there is provided an electrode assembly including: the above-described negative electrode current collector; a positive electrode having a structure in which a positive electrode mixture containing an active material is applied to at least one surface of a positive electrode current collector; and a separator interposed between the negative electrode current collector and the positive electrode.

[0031] According to another embodiment of the present disclosure, there is provided a lithium-free battery including a positive electrode, a negative electrode, a separator, and a lithium non-aqueous electrolyte, wherein the negative electrode includes the negative electrode current collector described in item 1 and a lithium layer formed on the negative electrode current collector, and wherein the lithium layer is formed by charging the lithium-free battery. Detailed Description

[0032] Hereinafter, the present disclosure will be described in more detail to facilitate understanding of the present invention.

[0033] The terms and words used in this specification and the claims should not be construed as limited to their ordinary or dictionary meanings, but should be interpreted based on the principle that the inventor has appropriately defined the concepts of the terms so as to describe the present invention in the best way, using meanings and concepts consistent with the technical scope of the present invention.

[0034] The terms provided herein are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are also intended to include the plural forms.

[0035] In addition, throughout the specification, unless otherwise stated, when a part is referred to as "comprising" a specific component, this means that the part may also contain other components without excluding other components.

[0036] According to one embodiment of the present disclosure, a negative electrode current collector for a lithium-free battery is provided, the negative electrode current collector comprising: a metal current collecting substrate, a conductive layer formed on at least one surface of the metal current collecting substrate and containing a conductive material; and an auxiliary layer formed on the conductive layer and increasing the electrodeposition density of lithium.

[0037] The metal current collecting substrate may be at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, aluminum-cadmium alloy, copper surface-treated with a different metal, and stainless steel surface-treated with a different metal.

[0038] Specifically, due to conductivity, cost, safety, etc., the metal current collecting substrate may be a metal containing copper, and more specifically, may be formed of copper.

[0039] The thickness of this metal current collecting substrate does not have a significant difference from that of the negative electrode current collector used in a conventional lithium-free battery. Specifically, it may be formed to a thickness of 3 μm to 200 μm, preferably 5 μm to 40 μm, and more preferably 8 μm to 20 μm.

[0040] Conventionally, such a metal current collecting substrate is used as a negative electrode current collector in a lithium-free battery.

[0041] However, as described above, when only such a metal current collecting substrate is used as a negative electrode current collector and lithium is electrodeposited by charging and discharging, a lithium layer with a low electrodeposition density is formed, and side reactions of the electrolyte are severe, resulting in a rapid deterioration of the life characteristics.

[0042] This is because the specific surface area of the metal used as the metal current collecting substrate is small and the affinity with lithium is low. Therefore, when lithium is electrodeposited, it is randomly electrodeposited.

[0043] To solve these problems, according to this embodiment, as the thin layer on the metal current collector substrate, the auxiliary layer is formed of a material capable of occluding and releasing lithium or a material having a strong affinity for lithium, whereby the specific surface area increases and the resistance decreases. When lithium is electrodeposited by subsequent charging / discharging using a material having an affinity for lithium, a lithium layer with a high electrodeposition density can be formed.

[0044] On the other hand, at the same time, when a conductive layer is formed between the auxiliary layer and the metal current collector substrate, not only can higher electron conductivity be ensured to prevent a decrease in electron conductivity due to the formation of the auxiliary layer, but also the bonding strength between the auxiliary layer and the metal current collector substrate can be enhanced. The conductive layer can be a primer layer, a conductive polymer layer, or a conductive epoxy layer.

[0045] The primer layer may contain a conductive material and an adhesive material.

[0046] The conductive material is not particularly limited as long as it is a component that maintains conductivity by electrically connecting the current collector and the auxiliary layer. For example, the conductive material may include at least one selected from the group consisting of natural graphite, artificial graphite, graphene, carbon black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, graphite nanofibers, carbon nanofibers, aluminum, nickel, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives.

[0047] The adhesive material is used to fix the conductive material on the current collector, form a coating film, and achieve the bonding between the current collector and the auxiliary layer. Examples of the adhesive material may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose (HPC), regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene, and fluororubber.

[0048] When the primer layer contains both a conductive material and an adhesive material at the same time, the weight ratio of the conductive material to the adhesive material may be from 1:99 to 99:1, preferably from 3:7 to 7:3.

[0049] When the weight ratio is below the above range, the content of the conductive material is too small, and due to the increase in internal resistance, the operating characteristics of the battery deteriorate. On the contrary, when the weight ratio exceeds the above range, the content of the adhesive material is too small, and thus sufficient bonding strength cannot be obtained.

[0050] The method for forming the primer layer can utilize the coating film forming methods commonly used in the art. For example, the methods that can be used include: wet coating methods such as concave coating, slot die coating, spin coating, spraying, rod coating, dip coating; and dry coating methods such as thermal evaporation, electron beam evaporation, chemical vapor deposition (CVD), and sputtering.

[0051] As the conductive polymer layer, a polymer generally referred to as a conductive polymer can be used. Examples of the conductive polymer may include at least one conductive polymer selected from the group consisting of poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate / ester) (PEDOT / PSS), polyaniline (PANI), polypyrrole (PPy), polythiophene (PT), polyacetylene (PA), and poly(p-phenylenevinylene) (PPV).

[0052] The conductive polymer layer can be formed by producing a mixed solution obtained by melting the conductive polymer or dissolving it in a solvent, and using various wet coating methods as described in the coating method of the primer layer. At this time, when the conductive polymer is mixed with the solvent, the solvent can be a polar organic solvent, examples of which include chloroform, dichloromethane, m-cresol, tetrahydrofuran (THF), dimethylformamide (DMF), and the like.

[0053] On the other hand, since the polymer itself in the conductive polymer layer exhibits binding force, a separate fixing material or the like is not required.

[0054] However, for stronger binding, an adhesive material disclosed in the conductive polymer layer can also be included. At this time, based on the total weight of the conductive polymer layer, the content of the adhesive material can be 0.1% by weight to 10% by weight.

[0055] In addition, optionally, the conductive polymer layer can further include graphite, such as natural graphite and artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking carbon black; conductive fibers, such as carbon fibers and metal fibers; metal powders, such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives.

[0056] The conductive epoxy layer can include a conductive filler and an adhesive.

[0057] Specifically, the conductive epoxy layer is used as an adhesive by mixing the conductive filler and the adhesive.

[0058] The conductive filler can include at least one selected from the group consisting of metal powders of gold, platinum, silver, copper, or nickel, carbon or carbon fibers, graphite, and composite powders.

[0059] The adhesive is a component that binds the conductive filler, but is not limited thereto. Examples thereof can be at least one selected from the group consisting of polymer materials of acrylic, epoxy, polyurethane, polysiloxane, polyimide, phenol, polyester, composite polymer resins, and low melting point glasses.

[0060] On the other hand, the conductive epoxy layer can be classified into room-temperature drying type, room-temperature curing type, heat-curing type, high-temperature calcination type, UV-curing type, etc. according to its manufacturing method. The room-temperature drying type can be formed by containing conductive fillers in an adhesive and a solvent such as acrylic and drying at room temperature, and the room-temperature curing type can be formed by additionally containing a two-component highly reactive curing agent and curing the solvent containing conductive fillers and the adhesive.

[0061] In addition, the heat-curing type can be formed by mainly using an epoxy-based adhesive and heating the solvent containing conductive fillers, the high-temperature calcination type can be formed by performing heat treatment at a high temperature and curing, and the UV-curing type can be formed by UV radiation curing.

[0062] At this time, the conductive fillers and the adhesive can also be included in a weight ratio of 1:99 to 99:1, specifically a weight ratio of 7:3 to 3:7.

[0063] When the content of the conductive fillers is very small and exceeds the above range, the conductivity decreases and the resistance increases, and when the content of the adhesive is very small, the binding force of the conductive fillers cannot be obtained, which is not preferable.

[0064] On the other hand, the auxiliary layer serves to increase the electrodeposition density of lithium deposition by increasing the actual specific surface area or increasing the lithium affinity. The auxiliary layer can include carbon-based materials, lithium metal oxides, metal compounds capable of alloying with lithium, metal oxides, lithium-metal alloys, or a mixture of two or more of them. In addition, a binder material can also be optionally included.

[0065] That is to say, the auxiliary layer according to this embodiment can include materials that are often used as negative electrode active materials. In the absence of the binder material, the binding effect can be supplemented by coating and dry rolling, and the conductive material may not be included. However, when the auxiliary layer becomes thicker, the auxiliary layer can also include a binder material that further binds them in addition to the conductive layer, and a conductive material for increasing conductivity.

[0066] Specifically, the carbon-based material can be carbon, such as non-graphitizable carbon and graphite-like carbon.

[0067] The lithium metal oxide can be, for example, Li x Fe 2 O 3 (0≤x≤1), Li x WO 2 (0≤x≤1), Li a Ti b O 4 (0.5≤a≤3, 1≤b≤2.5), etc.

[0068] The metal compound capable of alloying with lithium is a compound containing a metal that forms an alloy with lithium, and can be, for example, an Si-based active material or an Sn-based active material. For example, it can be Si / C, etc.

[0069] In addition, the metal oxide can be, for example, the following materials: SiO x (1 ≤ x ≤ 2), SnO, SnO 2 , PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , GeO, GeO 2 , Bi 2 O 3 , Bi 2 O 4 or Bi 2 O 5 .

[0070] Finally, the metal of the lithium-metal alloy can be, for example, the following metals: Na, K, Rb, Cs, Fr, Be, Sr, Ba, Ra, Mg, Ca, Al, Ge, Pb, As, Sb, Bi, Ag, Zn, Cd, P, or Hg.

[0071] The adhesive material is the same as the example of the adhesive material of the primer layer described in the conductive layer.

[0072] Here, the content ratio by weight of the carbon-based material, lithium metal oxide, metal compound capable of alloying with lithium, metal oxide, lithium-metal alloy, or a mixture of two or more thereof and the adhesive material can be 7:3 to 99:1.

[0073] When the content of the adhesive material is too large and exceeds the above range, it is difficult to fully exhibit the improvement effect of the lithium layer electrodeposition density aimed at by forming the auxiliary layer, and when the content of the adhesive material is too small, the bonding cannot be carried out well, so it is not preferred.

[0074] Therefore, when a carbon-based material, a lithium metal oxide, a metal compound capable of alloying with lithium, a metal oxide, a lithium-metal alloy, or a mixture of two or more thereof is included as an auxiliary layer, the specific surface area of the negative electrode current collector increases, and the sites where lithium ions generated by charging and discharging can be electrodeposited increase. In addition, since it is made of a material having a strong affinity for lithium, a lithium layer with improved electrodeposition density is obtained. Especially in the case of an alloy material, it can be applied in the form of particles / wires. In this case, the advantage is that the active area can be maximized, thereby reducing the resistance.

[0075] On the other hand, this auxiliary layer is different from the active material layer formed on the negative electrode in a general battery.

[0076] Specifically, the auxiliary layers are formed in a very thin range so that they actually react with lithium and receive lithium by charging, but the auxiliary layers are used as the negative electrode current collector for a lithium-free battery, where a lithium layer is formed on these auxiliary layers in a larger amount than them, and the lithium layer is used as the active material.

[0077] Therefore, the thickness of the auxiliary layer can be 0.1 μm to 40 μm, specifically 1 μm to 20 μm, and more specifically 1 μm to 10 μm.

[0078] When the auxiliary layer is formed too thick and outside the above range, lithium is inserted into the auxiliary layer so that the lithium layer cannot be sufficiently obtained by electrodeposition. And when the auxiliary layer is formed too thin, the improvement effect of the electrodeposition density of the lithium layer cannot achieve the effect expected in the present disclosure, which is not preferred.

[0079] Similarly, the conductive layer can have a thickness of 0.1 μm to 20 μm, specifically 1 μm to 10 μm, and more specifically 1 μm to 5 μm.

[0080] When the conductive layer is formed too thick and outside the above range, the total thickness of the negative electrode current collector increases, which is not preferred. And when the conductive layer is formed too thin, the effect of restoring conductivity cannot be exerted, which is not preferred.

[0081] In the negative electrode current collector for a non-lithium battery according to the present embodiment, the total thickness of the conductive layer and the auxiliary layer may be in the range of 0.1 μm to 60 μm. The reason why the total thickness of the conductive layer and the auxiliary layer is in the range of 0.1 μm to 60 μm is to form a negative electrode current collector for a non-lithium battery, which has the effect of increasing the electrodeposition density of lithium electrodeposited on the negative electrode current collector by charging and discharging the non-lithium battery. As a comparative example, as a component of the negative electrode in a general lithium secondary battery, the active material layer can be used as a site for receiving lithium from the positive electrode. In this case, since it is impossible to have the total thickness range of the conductive layer and the auxiliary layer according to the above embodiment, they can be distinguished from each other.

[0082] In addition, the total thickness of the conductive layer and the auxiliary layer may be in the range of 0.2 μm to 60 μm, or the total thickness may be in the range of 2 μm to 20 μm.

[0083] When the conductive layer and the auxiliary layer are too thin and outside the above range, it is difficult to obtain the improvement effect of the electrodeposition density of the lithium layer aimed at by the present disclosure. And when the layer is too thick, the total thickness of the negative electrode current collector increases, and ultimately, the energy density will decrease, making it difficult to achieve a high energy density battery, which is not preferred.

[0084] According to another embodiment of the present disclosure, there is provided an electrode assembly including: the above negative electrode current collector; a positive electrode having a structure in which a positive electrode mixture containing an active material is applied to at least one surface of a positive electrode current collector; and a separator interposed between the negative electrode current collector and the positive electrode.

[0085] According to the present embodiment, since the non-lithium battery uses the negative electrode current collector as the negative electrode when initially manufacturing the electrode assembly, the negative electrode in the electrode assembly can be formed by the negative electrode current collector.

[0086] Thereafter, the negative electrode current collector receives lithium from the positive electrode in response to the charging of the subsequently prepared non-lithium battery, and a lithium layer is formed on the current collector, and the lithium layer serves as an active material.

[0087] On the other hand, the positive electrode has a structure in which a positive electrode mixture containing an active material is applied to at least one surface of a positive electrode current collector.

[0088] The positive electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. In addition, the thickness of the positive electrode current collector can be 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to increase the binding force of the positive electrode active material. For example, the positive electrode current collector can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

[0089] The positive electrode active material as the active material can be, for example: layered compounds such as lithium nickel oxide (LiNiO 2 ), or compounds substituted with one or more transition metals; lithium manganese oxides such as the chemical formula Li 1+x Mn 2-x O 4 (where x is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2 ; lithium copper oxide (Li 2 CuO 2 ); vanadium oxides such as LiV 3 O 8 , LiFe 3 O 4 , V 2 O 5 and Cu 2 V 2 O 7 ; Ni-site type lithium nickel oxide represented by the chemical formula LiNi 1-x M x O 2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); lithium manganese composite oxide represented by the chemical formula LiMn 2-x M x O 2 (where M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1) or Li 2 Mn 3 MO 8 (where M = Fe, Co, Ni, Cu or Zn); LiMn 2 O 4 in which part of the Li in the chemical formula is replaced by alkaline earth metal ions; disulfides; Fe 2 (MoO 4 ) 3 etc., but not limited thereto.

[0090] Based on the above-mentioned positive electrode active material, the positive electrode mixture may further include a conductive material and a binder.

[0091] Based on the total weight of the positive electrode mixture layer, the addition amount of the conductive material is generally 0.1% by weight to 30% by weight, specifically 1% by weight to 10% by weight, and more specifically 1% by weight to 5% by weight. The conductive material is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, graphite such as natural graphite and artificial graphite can be used; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking carbon black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives.

[0092] The binder is a component that helps the adhesion of the active material, conductive material, etc. and the adhesion to the current collector. Based on the total weight of the positive electrode mixture layer, an amount of 0.1% by weight to 30% by weight, specifically 1% by weight to 10% by weight, and more specifically 1% by weight to 5% by weight can generally be added. Examples of the binder may include polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene monomer (EPDM), sulfonated EPDM, styrene - butadiene rubber, fluororubber, various copolymers, etc.

[0093] The separator is an insulating film with high ion permeability and mechanical strength. The pore size of the separator is generally 0.01 μm to 10 μm, and the thickness is generally 5 μm to 300 μm. As such a separator, for example, olefin polymers with chemical resistance and hydrophobicity such as polypropylene are used; sheets or non - woven fabrics made of glass fibers or polyethylene. When a solid electrolyte (such as a polymer) is used as the electrolyte, the solid electrolyte can also be used as the separator.

[0094] According to another embodiment of the present disclosure, a lithium - free battery is provided, which includes a positive electrode, a negative electrode, a separator, and a lithium non - aqueous electrolyte, wherein the negative electrode includes the negative electrode current collector of item 1 and a lithium layer formed on the negative electrode current collector.

[0095] At this time, as described above, the lithium layer can be formed on the negative electrode current collector by subsequently charging the lithium - free battery.

[0096] More specifically, the lithium - free battery is prepared by loading an electrode assembly including a negative electrode current collector, a positive electrode, and a separator together with a lithium non - aqueous electrolyte into a battery case, sealing the battery case, and then activating it.

[0097] At this time, lithium ions present in the non-aqueous electrolyte that are ionized from the positive electrode by charging during the activation process undergo an electrochemical reaction with the negative electrode current collector according to the present disclosure, and a lithium layer is deposited on the surface of the negative electrode current collector, and the lithium layer serves as the negative electrode active material.

[0098] The lithium non-aqueous electrolyte generally contains a lithium salt and a non-aqueous solvent. As the non-aqueous solvent, non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, etc. are used, but are not limited thereto.

[0099] As examples of the non-aqueous electrolyte, aprotic organic solvents such as N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate can be mentioned.

[0100] Examples of the organic solid electrolyte include polyethylene derivatives, poly(ethylene oxide) derivatives, poly(propylene oxide) derivatives, phosphate esters polymers, poly(lysine alginate), poly(ester sulfide), poly(vinyl alcohol), poly(vinylidene fluoride), and polymers containing ionic dissociating groups, etc.

[0101] Examples of the inorganic solid electrolyte include nitrides, halides, and sulfates of lithium (Li), such as Li 3 N, LiI, Li 5 NI 2 、Li 3 N-LiI-LiOH, LiSiO 4 、LiSiO 4 -LiI-LiOH, Li 2 SiS 3 、Li 4 SiO 4 、Li 4 SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 2 S-SiS 2 。

[0102] The lithium salt is a material that is easily soluble in the non-aqueous electrolyte. The lithium salt may include, for example, LiCl, LiBr, LiI, LiClO 4 、LiBF 4 、LiB10 Cl 10 、LiPF 6 、LiCF 3 SO 3 、LiCF 3 CO 2 、LiAsF 6 、LiSbF 6 、LiAlCl 4 、CH 3 SO 3 Li、CF 3 SO 3 Li、(CF 3 SO 2 ) 2 NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, imide salts, etc.

[0103] In addition, in order to improve charge / discharge characteristics, flame retardancy, etc., the non-aqueous electrolyte may further contain, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, diglyme, hexamethylphosphoramide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, in order to impart non-flammability, the electrolyte may further contain a halogen-containing solvent such as carbon tetrachloride and trifluoroethylene. In addition, in order to improve the high-temperature retention characteristics, the electrolyte may further contain carbon dioxide gas. In addition, fluoroethylene carbonate (FEC), propylene sultone (PRS), etc. may also be included.

[0104] The battery case is not limited as long as it has a structure capable of accommodating the electrode assembly, and may be a pouch-type battery known in the prior art, or a prismatic or cylindrical battery case made of a metal can.

[0105] Hereinafter, preferred embodiments of the present disclosure, comparative examples for comparison with them, and test examples for evaluating them will be described. However, it is obvious to those skilled in the art that these embodiments are only examples of the present disclosure, and various changes and modifications can be made within the scope and technical gist of the present disclosure, and such changes and modifications of course fall within the scope of the appended claims.

[0106] <Example 1>

[0107] A lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2) It is used as the positive electrode active material, PVdF is used as the binder, and Super-P is used as the conductive material. The positive electrode active material: binder: conductive material are added to NMP at a weight ratio of 96:2:2 to prepare the active material slurry, and then it is coated on the aluminum foil at 4 mAh / cm per side 2 It is coated on the aluminum foil, dried in a dryer at 130 °C in an air atmosphere, and then calendered to prepare the positive electrode.

[0108] A graphene dispersion of 2 wt% graphene / 5 wt% PVDF / 5 wt% H-NBR / 88 wt% NMP is coated on a 15-μm copper foil, and then dried to prepare a 3-μm thick primer layer. A slurry of 92 wt% graphite flakes (D50 = 3 μm) / 2 wt% carbon black / 6 wt% PVDF is coated on the primer layer and dried to prepare a 12-μm thick auxiliary layer, thereby preparing the negative electrode.

[0109] The SRS separator with a thickness of 20 μm is assembled on the positive and negative electrodes using the stacking method. The assembled battery is placed in an aluminum pouch-type battery case, and a solution of propylene carbonate (PC), fluoroethylene carbonate (FEC), and ethyl methyl carbonate (EMC) with a volume ratio of 1:2:7 in which 3.5 M of LiFSI is dissolved is injected, and then the battery case is sealed to prepare a single cell.

[0110] <Example 2>

[0111] The negative electrode is prepared and a single cell is prepared in the same manner as in Example 1, except that lithium metal oxide Li 4 Ti 5 O 12 (particle size (D50): 3 μm) is used instead of the graphite flakes in the auxiliary layer.

[0112] <Example 3>

[0113] The negative electrode is prepared and a single cell is prepared in the same manner as in Example 1, except that SnO 2 particles (particle size (D50): 3 μm) are used instead of the graphite flakes in the auxiliary layer.

[0114] <Example 4>

[0115] The negative electrode is prepared and a single cell is prepared in the same manner as in Example 1, except that LiAl particles (particle size (D50): 3 μm) are used instead of the graphite flakes in the auxiliary layer.

[0116] <Example 5>

[0117] The negative electrode was prepared in the same manner as in Example 1 and a single cell was prepared, except that a slurry of 92 wt% PEDOT / PSS, 2 wt% carbon black, and 6 wt% PVDF was coated on a 15 μm copper foil and dried to form a conductive polymer layer.

[0118] <Example 6>

[0119] The negative electrode was prepared in the same manner as in Example 1 and a single cell was prepared, except that a slurry of 92 wt% silver and 8 wt% acrylic binder was coated onto a 15 μm copper foil and dried to form a conductive epoxy layer.

[0120] <Comparative Example 1>

[0121] A single cell was prepared in the same manner as in Example 1, except that a 30 μm thick copper foil was used as the negative electrode as it was, without a primer layer and an auxiliary layer on the negative electrode.

[0122] <Comparative Example 2>

[0123] A single cell was prepared in the same manner as in Example 1, except that only the primer layer was formed on the negative electrode and this negative electrode on which the auxiliary layer was not formed was applied.

[0124] <Comparative Example 3>

[0125] The negative electrode was prepared in the same manner as in Example 1 and a single cell was prepared, except that instead of the primer layer, silver was vacuum deposited on a 15 μm copper foil to a thickness of 20 nm to produce a conductive layer.

[0126] <Comparative Example 4>

[0127] A single cell was prepared in the same manner as in Example 1, except that a negative electrode on which only the auxiliary layer was formed on a 15 μm copper foil and the primer layer was not applied was used.

[0128] <Experimental Example 1>

[0129] The single cells prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were charged under the following conditions, and then the cells were disassembled to calculate the thickness and electrodeposition density of the lithium electrodeposition layer formed on the negative electrode. The results are shown in Table 1 below.

[0130] Charging: 0.2C, CC / CV, 4.25V, 1 / 20C cut-off

[0131] For the thickness of the electrodeposition layer, the average value of the thickness was obtained by selecting two arbitrary points, and the electrodeposition density of the electrodeposition layer was digitized by calculating the deposition mass and deposition volume.

[0132] [Table 1]

[0133] Electrodeposited layer thickness (μm) Electrodeposited density (g / cc) Example 1 35 0.28 Example 2 40 0.25 Example 3 38 0.26 Example 4 45 0.23 Example 5 39 0.26 Example 6 37 0.27 Comparative Example 1 95 0.11 Comparative Example 2 90 0.12 Comparative Example 3 34 0.28 Comparative Example 4 43 0.24

[0134] (The theoretical density of lithium metal: 0.54 g / cm 3 )

[0135] Referring to Table 1, it can be confirmed that, compared with Comparative Examples 1 and 2 where the auxiliary layer was not formed, the thickness of the electrodeposited layer of Examples 1 to 6 according to the configuration of the present disclosure decreased and the electrodeposition density increased.

[0136] <Experimental Example 2>

[0137] The single cells of Examples 1 to 6 and Comparative Examples 1 to 4 were charged and discharged at 0.2C, and the first discharge capacity was measured. Charging and discharging were further carried out under the following conditions, and then the 200th discharge capacity retention rate relative to the first discharge capacity was calculated. The results are shown in Table 2.

[0138] Charging: 0.2C, CC / CV, 4.25V, cutoff at 1 / 20C

[0139] Discharging: 0.5C, CC, 3.0V, cutoff

[0140] [Table 2]

[0141] Initial capacity (mAh) Capacity retention rate after 200 cycles (%) Example 1 62.9 90 Example 2 63.3 85 Example 3 62.3 93 Example 4 62.9 84 Example 5 62.4 86 Example 6 62.7 88 Comparative Example 1 61.8 20 Comparative Example 2 61.5 30 Comparative Example 3 62.5 80 Comparative Example 4 62.8 82

[0142] Referring to Table 2, it can be confirmed that in the case of Examples 1 to 6, while the density of the electrodeposited layer increased, the life characteristics were excellent. From these results, it can be confirmed that when an auxiliary layer is generated by using a material for lithium insertion / extraction or alloying / dealloying, the life increases while the density of the lithium electrodeposited layer increases.

[0143] On the other hand, comparing Example 1 with Comparative Example 3, it can be confirmed that when the same auxiliary layer is included, the type of the conductive layer does not cause a large difference in the density of the electrodeposited layer, but in terms of life characteristics, compared with the case where the conductive layer is formed of a thin metal film, it is more preferable that the conductive layer is formed of a primer layer having the configuration of the present disclosure.

[0144] In addition, comparing Example 1 with Comparative Example 4, it can be confirmed that the difference in the presence or absence of the conductive layer has an impact on the density of the electrodeposited layer, and this impact even leads to a difference in life characteristics.

[0145] On the other hand, when looking at Example 1, 5 and 6 and Comparative Example 4, it can be seen that as the conductive layer, the primer layer is most preferable, but the conductive polymer layer and the conductive epoxy layer also have significant improvements.

[0146] On the other hand, it can be seen that in the case of Example 6 and Comparative Example 3, the same silver is used as the conductive layer, but the forming methods thereof are different. In the case of Comparative Example 3 formed of a thin metal film, the electrodeposition density slightly increases, but there is almost no difference. In terms of life characteristics, Example 6 formed using particles instead of a thin film layer exhibits more excellent performance.

[0147] This is understood to be because it is difficult to perform lithium insertion / extraction in the case of a thin film layer. Therefore, it can be seen that in terms of battery performance, the formation of the conductive epoxy layer is more excellent than the formation of the metal thin film layer.

[0148] Those of ordinary skill in the art to which the present invention pertains can make various applications and modifications within the scope of the present invention based on the above.

[0149] [Industrial Applicability]

[0150] As described above, the negative electrode current collector according to the embodiment of the present disclosure forms a conductive layer and an auxiliary layer on at least one surface of a metal substrate. Thus, when the negative electrode current collector is used as the negative electrode of a lithium-free battery, uniform lithium electrodeposition due to charging and discharging is carried out, and the negative electrode current collector has the effect of increasing the electrodeposition density of the lithium layer formed thereby.

[0151] In addition, thereby, a lithium-free battery including the negative electrode current collector can minimize side reactions of the electrolyte, thereby improving life characteristics.

Claims

1. A lithium-free battery, the lithium-free battery comprising a positive electrode, a negative electrode, a separator, and a lithium non-aqueous electrolyte, wherein the negative electrode comprises a negative current collector and a lithium layer formed on the negative current collector, and wherein the negative current collector comprises: a metal current collecting substrate; a conductive layer formed on at least one surface of the metal current collecting substrate and comprising a conductive material; and an auxiliary layer formed on the conductive layer and increasing the electrodeposition density of lithium, wherein the conductive layer is a primer layer, a conductive polymer layer, or a conductive epoxy layer, and the thickness of the conductive layer is in the range of 0.1 μm to 20 μm, wherein the auxiliary layer comprises a carbon-based material, a lithium metal oxide, a metal compound capable of alloying with lithium, a metal oxide, or a mixture of two or more thereof, and the thickness of the auxiliary layer is in the range of 0.1 μm to 40 μm, wherein the primer layer is composed of a conductive material and an adhesive material, and the conductive material is at least one selected from the group consisting of natural graphite, artificial graphite, graphene, carbon black, channel black, furnace black, lamp black, thermal cracking carbon black, carbon nanotubes, graphite nanofibers, carbon nanofibers, aluminum, nickel, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and wherein the conductive epoxy layer is composed of a conductive filler and an adhesive, and the conductive filler is at least one selected from the group consisting of metal powders of gold, platinum, silver, copper, or nickel, carbon or carbon fibers, graphite, and composite powders, wherein, the lithium layer is formed by charging the lithium-free battery.

2. The lithium-free battery according to claim 1, wherein: the metal current collecting substrate is at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, an aluminum-cadmium alloy, copper surface-treated with a different metal, and stainless steel surface-treated with a different metal.

3. The lithium-free battery according to claim 1, wherein: the metal current collecting substrate is a metal containing copper.

4. The lithium-free battery according to claim 1, wherein: the conductive polymer layer comprises at least one conductive polymer selected from the group consisting of poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate / ester), polyaniline, polypyrrole, polythiophene, polyacetylene, and poly(p-phenylenevinylene).

5. The lithium-free battery according to claim 1, wherein: the auxiliary layer further comprises an adhesive.

6. The lithium-free battery according to claim 1, wherein: the total thickness of the conductive layer and the auxiliary layer is in the range of 0.1 μm to 60 μm.

7. The lithium-free battery according to claim 6, wherein: the total thickness of the conductive layer and the auxiliary layer is in the range of 2 μm to 20 μm.

8. The lithium-free battery according to claim 1, wherein: the positive electrode has a structure in which a positive electrode mixture containing an active material is applied to at least one surface of a positive current collector; and the separator is interposed between the negative current collector and the positive electrode.