Lithium secondary battery and method of manufacturing same

Abstract

The present invention relates to a lithium secondary battery and a manufacturing method thereof, and the lithium secondary battery includes a sensing probe including a metal oxide having a plateau potential of 1.3 V to 1.8 V on the side of a negative electrode composite layer, thereby enabling non-destructive, real-time confirmation of the presence or absence of lithium metal deposition that may occur on the negative electrode during initial charging of the lithium secondary battery. As a result, the present invention has advantages of not only reducing the defect rate during the manufacturing of lithium secondary batteries, but also improving the degradation of lithium secondary batteries, such as capacity loss, thereby extending the lifespan and improving the safety of the lithium secondary batteries.

Description

[Technical field]

[0001] The present invention relates to a lithium secondary battery and a method for producing the same.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0100117 dated July 29, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference. [Background technology]

[0003] With technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries, which have high energy density and working potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Recently, as lithium secondary batteries are used as power sources for medium- to large-sized devices such as electric vehicles, there is an increasing demand for lithium secondary batteries with high capacity, high energy density, and low cost. Lithium secondary batteries are the most practical technology for such high-performance secondary batteries and / or secondary batteries for vehicles. Lithium secondary batteries function by repeatedly inserting and extracting lithium ions between the negative and positive electrodes. There are lithium salt-containing electrolytes that allow lithium ions to move between these electrodes but not electrons.

[0005] While much research has been conducted on these secondary batteries from the viewpoint of increasing capacity and density, it is also important to improve their lifespan and safety. To achieve this, it is necessary to suppress the decomposition reaction with the electrolyte on the surface of the electrode and to prevent overcharging / discharging. In particular, it is necessary to prevent so-called lithium-plating, in which lithium is deposited on the surface of the negative electrode. If lithium metal is deposited, it can cause side reactions with the electrolyte and changes in the kinetic balance of the secondary battery, which can cause degradation of the secondary battery, such as capacity loss, affect the lifespan of the secondary battery, and can cause safety issues such as the loss of overcharge adjustment function.

[0006] The deposition of lithium metal may occur when the positive electrode composite layer separates from the negative electrode composite layer during stacking of the positive and negative electrodes during the manufacturing process of the lithium secondary battery, and the deposited lithium metal occurs continuously during the charging and discharging process of the battery. To solve this problem, it is necessary to detect the deposition of lithium metal in real time during the manufacturing process of the lithium secondary battery.

[0007] However, it has been very difficult to know in real time whether lithium metal has been deposited in a secondary battery. Conventional techniques for non-destructively detecting whether lithium metal has been deposited in a negative electrode include low-temperature discharge, heat capacity analysis, thickness increase analysis, etc. However, these techniques are all limited in detecting lithium metal deposited in a negative electrode in real time because they cannot be measured while the secondary battery is in operation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2017-0023583 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, an object of the present invention is to provide a lithium secondary battery and a method for manufacturing the same that can non-destructively check in real time whether or not lithium metal deposition that may occur in the negative electrode of the lithium secondary battery occurs. [Means for solving the problem]

[0010] To solve the above problems, In one embodiment, the present invention comprises: The battery includes an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed between the negative electrode current collector and a separator, A sensing probe containing a metal oxide having a plateau potential of 1.3V to 1.8V is provided on the side of the negative electrode mixture layer, thereby providing a lithium secondary battery.

[0011] Here, the sensing probe may have a wire structure including a core wire containing a conductive metal and a metal oxide layer surrounding the core wire.

[0012] The sensing probe may have an average diameter of 10 to 200 μm, and the average diameter may be smaller than the average thickness of the negative electrode mixture layer.

[0013] Further, the sensing probe may be disposed at a distance of 0.1 to 2,000 μm from the side of the negative electrode mixture layer.

[0014] The metal oxide contained in the sensing probe may contain one or more metals selected from the group consisting of titanium, vanadium, iron, cobalt, nickel, copper, molybdenum, tungsten and niobium.

[0015] Furthermore, the metal oxide may be a lithium titanate compound represented by the following chemical formula 1.

[0016] [Chemical formula 1] Li a Ti b Mc O d

[0017] In the above chemical formula 1, M is Sn, Cr, Y, Nb, Mg, Zn, Ni, V, Na, K, Ca, Co, Ta, Mo, Zr, Al, Cu, Mn or Bi; a is an integer satisfying 0.4≦a≦5, b is an integer satisfying 0.5≦b≦5.5, c is an integer satisfying 0≦c≦0.9, d is an integer satisfying the condition 1.5≦d≦12.5.

[0018] The sensing probe may also include a metal oxide charged to a state of charge (SOC) of 40% to 60%.

[0019] Further, in one embodiment, the present invention provides inserting an electrode assembly including a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode into a secondary battery case, and disposing a sensing probe including a metal oxide having a plateau potential of 1.3 V to 1.8 V on a side of the negative electrode composite layer of the negative electrode to assemble a lithium secondary battery; filling an electrolyte into the assembled lithium secondary battery case; charging the electrolyte-filled lithium secondary battery; measuring a potential of a sensing probe provided in the lithium secondary battery.

[0020] At this time, the sensing probe may be charged at a state of charge (SOC) of 40% to 60%.

[0021] In addition, the method for manufacturing the lithium secondary battery may further include, after the step of measuring the potential of the sensing probe, determining that the lithium secondary battery is defective if the measured potential of the sensing probe exceeds 2.0V. Effect of the Invention

[0022] The lithium secondary battery according to the present invention can non-destructively and in real time check for the presence or absence of lithium metal deposition that may occur on the negative electrode during initial charging of the lithium secondary battery by providing a sensing probe including a metal oxide having a plateau potential of 1.3 V to 1.8 V on the side of the negative electrode composite layer. As a result, the present invention has the advantages of being able to reduce the defective rate during the manufacture of lithium secondary batteries, as well as improving degradation of the lithium secondary battery, such as capacity loss, thereby increasing the lifespan and improving the safety of the lithium secondary battery. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a schematic diagram showing the structure of a lithium secondary battery of Comparative Example 2 according to the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing the structure of a lithium secondary battery according to a first embodiment of the present invention. [Diagram 3] 13 is an image showing a position on the side of a negative electrode mixture layer where a sensing probe can be placed. [Figure 4] 1 is a graph showing a change in potential of a sensing probe provided in a lithium secondary battery of Example 4 according to the present invention and a control group during initial charging. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Although the present invention can be modified in various ways and can have various embodiments, a specific embodiment will be described in detail in the detailed description.

[0025] However, it should be understood that this is not intended to limit the invention to the particular embodiment, but rather to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0026] In the present invention, the terms "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] In addition, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion in between. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion in between. In addition, in the present application, being "located on" may include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0028] Furthermore, in the present invention, a "major component" means 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 97.5% by weight or more of the total weight of the composition or specific component, and in some cases, it can also mean 100% by weight when it constitutes the entire composition or specific component.

[0029] The present invention will now be described in more detail.

[0030] <Lithium secondary battery> In one embodiment, the present invention comprises: The battery includes an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed between the negative electrode current collector and a separator, A lithium secondary battery is provided having a sensing probe including a metal oxide having a plateau potential of 1.3V to 1.8V on the side of the negative electrode mixture layer.

[0031] The present invention relates to a lithium secondary battery, the lithium secondary battery having a configuration including an electrode assembly including a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode.

[0032] In this case, the negative electrode provided in the electrode assembly has a sensing probe on a side of the negative electrode mixture layer, specifically, on an exposed side end of the negative electrode mixture layer that is not in contact with the separator and the negative electrode current collector, i.e., on a sliding boundary surface of the negative electrode mixture layer, and the sensing probe can non-mechanically detect lithium metal deposited on the negative electrode mixture layer in real time during initial charging of the lithium secondary battery.

[0033] More specifically, when the positive electrode mixture layer containing the positive electrode active material is stacked in a misaligned manner with the negative electrode mixture layer, for example, when the negative electrode is not stacked to cover the entire surface of the positive electrode during the stacking process of the positive electrode and the negative electrode, but is biased to one side, a part of the positive electrode mixture layer may be exposed. When a part of the positive electrode mixture layer is exposed in this way, lithium ions may be precipitated on the separator side where there is no negative electrode during the charging process of the battery. The precipitated lithium metal is continuously generated during the charging and discharging process of the battery and grows in a dendritic shape, which not only causes an internal short circuit in the battery, but also causes a violent exothermic reaction when exposed to moisture, which significantly reduces the safety of the battery. Therefore, in order to check the precipitation of lithium metal in the past, it is necessary to separate the battery cell from the battery pack and perform a CT analysis on the separated battery cell or disassemble the battery cell, which is costly and time-consuming, and there is also a problem that it is difficult to check whether lithium metal is precipitated during the use of a lithium secondary battery and / or a battery module including the same. However, in the lithium secondary battery according to the present invention, by introducing a sensing probe containing a metal oxide into the side surface of the negative electrode composite layer, it is possible to easily check the deposition of lithium metal in the negative electrode in real time without separating the battery cells housed in the battery pack to perform CT scans or disassembling the battery cells.

[0034] For this purpose, the sensing probe may include a metal oxide having a plateau potential of 1.3 V to 1.8 V, and more specifically, may include a metal oxide having a plateau potential of 1.3 V to 1.7 V, 1.3 V to 1.6 V, 1.4 V to 1.7 V, 1.4 V to 1.6 V, 1.4 V to 1.8 V, or 1.45 V to 1.55 V. The term "plateau potential" refers to a region where the potential of the active material is maintained constant in the reversible capacity region, except for the initial and / or final stages, during charging and discharging of a secondary battery, and refers to a section where the absolute value of the slope of the charge and discharge profile in the charge and discharge curve is close to 0.

[0035] Such metal oxides may include oxides containing one or more metals selected from the group consisting of titanium, manganese, iron, cobalt, nickel, copper, molybdenum, tungsten, and niobium. For example, the metal oxides having a plateau potential of 1.3 V to 1.8 V include TiO 2 , MnO 2 , Fe 2 O 3 , Fe 3 O 4 , CoO, Co 3 O 4 , MoO 3 , NiO, CuO, WO 3 , MoO 2 , Nb 2 O 5 The sensing probe can be constructed using metal oxides such as, either alone or in combination.

[0036] In addition, the sensing probe may include a lithium titanate compound represented by the following Chemical Formula 1 as a metal oxide.

[0037] [Chemical formula 1] Li a Ti b M c O d

[0038] In the above chemical formula 1, M is Sn, Cr, Y, Nb, Mg, Zn, Ni, V, Na, K, Ca, Co, Ta, Mo, Zr, Al, Cu, Mn or Bi; a is an integer satisfying 0.4≦a≦5, b is an integer satisfying 0.5≦b≦5.5, c is an integer satisfying 0≦c≦0.9, d is an integer satisfying the condition 1.5≦d≦12.5.

[0039] The lithium titanate compound represented by the above formula 1 has a plateau potential of about 1.4 V to 1.7 V, and is represented by LiTiO, Li 0.5 TiO 2 , Li 2 TiO 3 , Li 2 Ti 3 O 7 , Li 4 Ti 5 O 12 These may be included alone or in combination of two or more.

[0040] As an example, the electrode assembly according to the present invention is 4 Ti 5 O 12 A sensing probe including the above-mentioned may be provided on one side of the separator in contact with the negative electrode mixture layer.

[0041] Furthermore, the sensing probe may be charged so that the state of charge (SOC) of the metal oxide is 40% to 60%, specifically, 45% to 60%, 40% to 55%, or 45% to 55%. The sensing probe of the present invention exhibits a plateau potential of 1.3V to 1.8V, and when lithium metal deposited on the negative electrode contacts the surface, the potential increases significantly. Therefore, the state of charge (SOC) may be adjusted to 40% to 60% so that the plateau potential of the sensing probe can be stably realized. The sensing probe may be electrically connected to a battery management system (BMS) installed in the lithium secondary battery to monitor the state of charge (SOC) of the electrode in real time.

[0042] The sensing probe may have a wire structure including a core wire containing a conductive metal and a metal oxide layer surrounding the core wire for charging the metal oxide. Specifically, the sensing probe may include a core wire, without being particularly limited, as long as it is a conductor wire that is normally applied in the industry. For example, the core wire may include a wire in the form of a wire containing one or more metals selected from the group consisting of copper, brass, zinc, aluminum, gold, and silver. In addition, the core wire may include a coating layer, i.e., a metal oxide layer, in which the surface is coated with a metal oxide having a plateau potential of 1.3V to 1.8V. Furthermore, the metal oxide layer may be located at the end of the sensing probe, and the part on which the metal oxide layer is not formed may have an insulating coated form.

[0043] As an example, the sensing probe has Li on the surface of a copper conductor. 4 Ti 5 O 12 The wire electrode may include an LTO layer formed by coating the LTO slurry.

[0044] The sensing probe may have an average diameter of 10 μm to 200 μm. Specifically, the sensing probe may have an average diameter of 10 μm to 200 μm, 50 μm to 200 μm, 80 μm to 200 μm, 100 μm to 200 μm, 120 μm to 200 μm, 150 μm to 200 μm, 10 μm to 150 μm, 10 μm to 120 μm, 10 μm to 100 μm, 50 μm to 150 μm, 80 μm to 190 μm, or 110 μm to 180 μm.

[0045] Furthermore, the sensing probe may be smaller than the average thickness of the negative electrode mixture layer. Specifically, the sensing probe may have an average diameter that is 20% to 99% of the average thickness of the negative electrode mixture layer, and more specifically, may have an average diameter that is 30% to 99%, 40% to 99%, 50% to 99%, 60% to 99%, 30% to 95%, 40% to 95%, 50% to 95%, 50% to 90%, or 60% to 90% of the average thickness of the negative electrode mixture layer.

[0046] By controlling the average diameter of the sensing probe within the above range, the present invention can prevent the sensing probe from coming into contact with a material other than the deposited lithium metal to cause a short circuit, or prevent the deposited lithium metal from losing charge before coming into contact with the sensing probe, resulting in failure to detect the deposited lithium metal.

[0047] FIG. 2 is a schematic diagram showing the structure of a lithium secondary battery 200 according to the present invention. As shown in FIG. 2, the sensing probe 240 may be disposed at a certain distance from the side of the negative electrode composite layer 212, specifically, from the boundary surface of the sliding part of the negative electrode composite layer 212. Specifically, lithium metal is generated at the negative electrode during charging of the lithium secondary battery 200, and is generated in large amounts at the side of the negative electrode composite layer 212 when a shift s occurs between the positive electrode composite layer 211 of the positive electrode and the negative electrode composite layer 212 of the negative electrode, which are stacked around the separator 213. The lithium metal precipitated in this way may grow in a dendrite shape and cause an internal short circuit at the end of the electrode or cause a violent exothermic reaction. In order to detect this in real time in a non-mechanical manner, the sensing probe 240 may be disposed at a certain distance from the side of the negative electrode composite layer 212.

[0048] For example, the sensing probe may be disposed on the side of the composite layer so as to be spaced 0.1 μm to 2,000 μm from the side of the negative electrode composite layer. Specifically, the sensing probe may be disposed on the side of the composite layer so as to be spaced 5 μm to 1,500 μm, 10 μm to 1,000 μm, 10 μm to 500 μm, 10 μm to 250 μm, 10 μm to 200 μm, 10 μm to 100 μm, 10 μm to 80 μm, 50 μm to 200 μm, 100 μm to 200 μm, 30 μm to 80 μm, or 10 μm to 50 μm from the side of the negative electrode composite layer.

[0049] The sensing probe can be disposed at any position on the side surface of the negative electrode mixture layer without any particular limitations.

[0050] FIG. 3 is an image showing a position where a sensing probe can be placed on the side of the negative electrode mixture layer 12 provided in the electrode assembly 10. Referring to FIG. 3, the sensing probe is placed on the side of the negative electrode mixture layer 12 where an electrode tap (not shown) is located. When it is formed on one side, the opposite side <c> Can be placed on the side or electrode taps are formed< / c> adjacent to the side and / or ´ Placed on the side or, in some cases, electrode taps are formed It can also be arranged so as not to come into contact with the electrode taps on the sides.

[0051] The sensing probe may be introduced into at least one of the sides of the negative electrode mixture layer, and for this purpose, one or more electrodes may be provided in the lithium secondary battery. For example, referring to FIG. 3, when the lithium secondary battery is a pouch-type battery, the sensing probe may be provided with an electrode tap. When it is formed on one side, the opposite side <c> Sides and electrode taps formed< / c> adjacent to the side and ' It may have a configuration in which one is introduced on each side.

[0052] Meanwhile, the positive electrode provided in the lithium secondary battery according to the present invention includes a positive electrode mixture layer formed on at least one surface of a positive electrode current collector, and the positive electrode mixture layer includes a lithium metal composite oxide represented by the following Chemical Formula 2 as a positive electrode active material capable of reversible intercalation and deintercalation.

[0053] [Chemical formula 2] Li x [Ni y Co z Mn w M 1 v ]O u

[0054] In the above chemical formula 2, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo; x, y, z, w, v, and u are 1.0≦x≦1.30, 0≦y<0.95, 0 <z≦0.5、0<w≦0.5、0≦v≦0.2、1.5≦u≦4.5である。

[0055] The lithium metal composite oxide represented by the above chemical formula 2 is a composite metal oxide containing lithium and nickel, and is LiCoO 2 , LiCo 0.5 Zinc 0.5 O 2 , LiCo 0.7 Zinc 0.3 O 2 , LiNiO 2 , LiNi 0.5 Co 0.5 O 2 , LiNi 0.6 Co 0.4 O 2 , LiNi 1 / 3 Co 1 / 3 Al 1 / 3 O 2 , LiMnO 2 , LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.9 Co 0.05 Mn 0.05 O 2 , LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O 2 , and LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O 2 As an example, the positive electrode active material may contain one or more compounds selected from the group consisting of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 Or LiNi 0.6 Co 0.2 Mn 0.2 O 2 Each of them can be used alone or in combination.

[0056] The content of the positive electrode active material may be 85 to 95 parts by weight, specifically 88 to 95 parts by weight, 90 to 95 parts by weight, 86 to 90 parts by weight, or 92 to 95 parts by weight, relative to 100 parts by weight of the positive electrode mixture layer.

[0057] Furthermore, the positive electrode mixture layer may further contain a conductive material, a binder, other additives, and the like, in addition to the positive electrode active material.

[0058] In this case, the conductive material can be used to improve the electrical performance of the positive electrode, and can be one or more carbon-based materials selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber. For example, the conductive material may include acetylene black.

[0059] The conductive material may be contained in an amount of 1 to 5 parts by weight relative to 100 parts by weight of the composite layer, specifically, 1 to 4 parts by weight, 2 to 4 parts by weight, 1.5 to 5 parts by weight, or 1 to 3 parts by weight of the conductive material.

[0060] Furthermore, the binder may include one or more resins selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, and copolymers thereof. As an example, the binder may include polyvinylidene fluoride.

[0061] The binder may be contained in an amount of 1 to 10 parts by weight, specifically 2 to 8 parts by weight, 2 to 6 parts by weight, 1 to 5 parts by weight, or 2 to 4 parts by weight, based on 100 parts by weight of the entire mixture layer.

[0062] Furthermore, the positive electrode can be a positive electrode current collector having high conductivity without inducing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. can be used, and in the case of aluminum or stainless steel, those surface-treated with carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode current collector can be formed with fine irregularities on the surface to increase the adhesive force of the positive electrode active material, and can be in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc. Furthermore, the average thickness of the current collector can be appropriately applied in the range of 1 to 500 μm in consideration of the conductivity and total thickness of the positive electrode to be manufactured.

[0063] In addition, the negative electrode provided in the lithium secondary battery according to the present invention includes a negative electrode mixture layer formed on at least one surface of the negative electrode current collector, and the negative electrode mixture layer can be manufactured by applying, drying, and pressing a negative electrode active material.

[0064] Here, the negative electrode active material may be any material commonly used in the art as a negative electrode active material, and may include both a carbon material and a silicon (Si)-containing material. The carbon material refers to a carbon material mainly composed of carbon, and examples of the carbon material include graphite having a perfect layered crystal structure such as natural graphite, soft carbon having a low-crystalline layered crystal structure (graphene structure; a structure in which hexagonal honeycomb-shaped carbon planes are arranged in layers), and hard carbon in which such a structure is mixed with a non-crystalline portion, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, acetylene black, ketjen black, carbon nanotubes, fullerene, activated carbon, graphene, carbon nanotubes, etc., and preferably includes at least one selected from the group consisting of natural graphite, artificial graphite, graphene, and carbon nanotubes. More preferably, the carbon material includes natural graphite and / or artificial graphite, and may further include any one or more of graphene and carbon nanotubes together with the natural graphite and / or artificial graphite. In this case, the carbon material may include 0.1 to 10 parts by weight of graphene and / or carbon nanotubes relative to 100 parts by weight of the total carbon material, more specifically, 0.1 to 5 parts by weight or 0.1 to 2 parts by weight of graphene and / or carbon nanotubes relative to 100 parts by weight of the total carbon material.

[0065] The silicon (Si)-containing material is a material containing silicon (Si) as a main component as a metal component, and is not limited to silicon (Si), silicon monoxide (SiO) or silicon dioxide (SiO 2 The silicon (Si)-containing material may be silicon monoxide (SiO) and silicon dioxide (SiO 2 ) are uniformly mixed or composited and contained in the negative electrode mixture layer, they are silicon oxide (SiOx, where 1≦x≦ 2 ). Furthermore, the silicon (Si)-containing material includes silicon monoxide (SiO) particles and silicon dioxide (SiO 2 When the particles have a uniformly mixed morphology, each particle may have the morphology of a crystalline particle, and silicon monoxide (SiO) particles and silicon dioxide (SiO 2 When the silicon (Si) particles have a composite form, they may have the form of crystalline particles or amorphous particles, and in this case, the ratio of the amorphous particles may be 50 to 100 parts by weight, specifically 50 to 90 parts by weight, 60 to 80 parts by weight, or 85 to 100 parts by weight, based on 100 parts by weight of the total silicon (Si)-containing material. By controlling the ratio of the amorphous particles contained in the silicon (Si)-containing material to the above range, the present invention can improve the thermal stability and flexibility without deteriorating the electrical properties of the electrode.

[0066] Furthermore, the negative electrode active material may contain a carbon material and a silicon (Si)-containing material, and may contain 75 to 99 parts by weight of the carbon material and 1 to 25 parts by weight of the silicon (Si)-containing material relative to 100 parts by weight of the total. More specifically, the negative electrode active material may contain 80 to 95 parts by weight of the carbon material and 5 to 20 parts by weight of the silicon (Si)-containing material, 90 to 97 parts by weight of the carbon material and 3 to 10 parts by weight of the silicon (Si)-containing material, 85 to 92 parts by weight of the carbon material and 8 to 15 parts by weight of the silicon (Si)-containing material, 82 to 87 parts by weight of the carbon material and 13 to 18 parts by weight of the silicon (Si)-containing material, or 93 to 98 parts by weight of the carbon material and 2 to 7 parts by weight of the silicon (Si)-containing material relative to 100 parts by weight of the total. By adjusting the contents of the carbon material and silicon (Si)-containing material contained in the negative active material within the above ranges, the present invention can reduce the lithium consumption and irreversible capacity loss during the initial charge and discharge of the battery, and improve the charge capacity per unit mass.

[0067] Furthermore, the negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery, and for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. can be used. In the case of copper or stainless steel, it is also possible to use a material that has been surface-treated with carbon, nickel, titanium, silver, etc. In addition, the negative electrode current collector can be formed with fine irregularities on the surface to strengthen the binding force with the negative electrode active material, as with the positive electrode current collector, and can be in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc. In addition, the average thickness of the negative electrode current collector can be appropriately applied in the range of 1 to 500 μm, taking into consideration the conductivity and total thickness of the negative electrode to be manufactured.

[0068] In addition, in the electrode assembly for a lithium secondary battery according to the present invention, the average thickness of each composite layer constituting the positive electrode and the negative electrode and / or the average area ratio therebetween can be controlled within a certain range.

[0069] Specifically, the average thickness of the positive electrode mixture layer may be 50 μm to 300 μm, and more specifically, may be 100 μm to 200 μm, 80 μm to 150 μm, 120 μm to 170 μm, 150 μm to 300 μm, 200 μm to 300 μm, 150 μm to 190 μm, 130 μm to 160 μm, 100 μm to 150 μm, or 110 μm to 160 μm.

[0070] The negative electrode mixture layer may have an average thickness of 100 μm to 300 μm, and more specifically, may have an average thickness of 100 μm to 250 μm, 100 μm to 200 μm, 100 μm to 180 μm, 100 μm to 150 μm, 120 μm to 200 μm, 140 μm to 200 μm, or 140 μm to 160 μm.

[0071] Furthermore, the separator provided in the electrode assembly for a lithium secondary battery according to the present invention is not particularly limited as long as it is a thin insulating film that is commonly used in the industry and is interposed between the positive electrode and the negative electrode and has high ion permeability and mechanical strength. Specifically, a sheet or nonwoven fabric made of chemically resistant and hydrophobic polypropylene, glass fiber, or polyethylene can be used. In some cases, a composite separator in which inorganic particles / organic particles are coated with an organic binder polymer on a porous polymer substrate such as the sheet or nonwoven fabric can be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte can also serve as the separator. Furthermore, the pore diameter of the separator may be an average of 0.01 to 10 μm, and the thickness may be an average of 5 to 300 μm. In addition, the separator has an area larger than the positive electrode and the negative electrode, and can prevent the positive electrode mixture layer and the negative electrode mixture layer from contacting each other in advance. Specifically, since the positive electrode mixture layer is formed to have an area smaller than that of the negative electrode mixture layer in order to prevent a short circuit inside the battery, the separator may be provided to be 101% to 110% larger based on the area of ​​the negative electrode mixture layer, and may be provided to have a length approximately 0.5 to 2 mm longer than that of the negative electrode mixture layer.

[0072] <Method of manufacturing lithium secondary battery> In one embodiment, the present invention provides a method for producing a composition comprising: Assembling a lithium secondary battery by placing an electrode assembly including a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode in a secondary battery case, and disposing a sensing probe including a metal oxide having a plateau potential of 1.3 V to 1.8 V on a side of the negative electrode composite layer of the negative electrode; filling an electrolyte into the assembled lithium secondary battery case; charging the electrolyte-filled lithium secondary battery; and measuring a potential of the sensing probe provided in the lithium secondary battery.

[0073] The method for manufacturing the lithium secondary battery according to the present invention may include the steps of: placing an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode into a secondary battery case; assembling the lithium secondary battery by disposing a sensing probe on a side of the negative electrode composite layer introduced into the secondary battery case; injecting an electrolyte into the assembled lithium secondary battery to initially charge the battery; and measuring the potential of the sensing probe.

[0074] When the positive and negative electrode composite layers included in the electrode assembly are stacked with a shift, lithium metal is deposited on the side of the negative electrode composite layer during initial charging. However, the present invention can detect this in real time in a non-destructive manner by introducing a sensing probe with a state of charge (SOC) of 40% to 60% into the side of the negative electrode composite layer and measuring the potential of the sensing probe during initial charging of the secondary battery.

[0075] Here, the sensing probe may be disposed on the side of the negative electrode mixture layer and then charged separately before charging the lithium secondary battery, i.e., charging the electrode assembly. Specifically, the sensing probe may be introduced on the side of the negative electrode mixture layer and electrically connected to the positive electrode, and then, when the lithium secondary battery is assembled and electrolyte filling is completed, a step of separately charging only the sensing probe to satisfy a condition of 40% to 60% state of charge (SOC) before initial charging of the lithium secondary battery may be performed.

[0076] In addition, the method for manufacturing a lithium secondary battery according to the present invention may further include a step of determining that the lithium secondary battery is defective if the measured potential of the sensing probe exceeds 2.0V after the step of measuring the potential of the sensing probe. A charged sensing probe has a plateau potential of 1.3V to 1.8V, but the potential increases rapidly when deposited lithium metal contacts the surface. Therefore, in the manufacturing method of the present invention, if the potential of the sensing probe exceeds 2.0V after the step of measuring the potential of the sensing probe, it means that lithium metal has been deposited on the negative electrode of the electrode assembly, so that the target lithium secondary battery can be determined to be defective, and if it is 2.0V or less, it can be determined to be a normal lithium secondary battery.

[0077] Meanwhile, the configurations of the electrode assembly and the sensing probe inserted into the secondary battery case are the same as those described above for the lithium secondary battery, and therefore a detailed description thereof will be omitted.

[0078] The electrolyte injected into the secondary battery case is composed of an electrolytic solution and a lithium salt. As the electrolytic solution, a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, or the like can be used.

[0079] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0080] Examples of the organic solid electrolyte that can be used include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymeric materials containing ionic dissociation groups.

[0081] The inorganic solid electrolyte may be, for example, 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 Nitrides, halides, and sulfates of Li such as those mentioned above can be used.

[0082] The lithium salt is a substance that is easily dissolved in a non-aqueous electrolyte, and examples of the lithium salt include LiCl, LiBr, LiI, and LiClO. 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , C.H. 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylboronate, imide, etc. can be used.

[0083] In addition, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added to the electrolyte in order to improve charge / discharge characteristics, flame retardancy, etc. In some cases, a halogen-containing solvent such as carbon tetrachloride or trifluoroethylene may be further added to impart non-flammability, and carbon dioxide gas may be further added to improve high-temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate), PRS (Propenesultone), etc. may be further added.

[0084] <Lithium sensing device> Further, in one embodiment, the present invention provides A lithium detection device is provided that can non-destructively detect lithium metal deposited on a negative electrode during initial charging of a lithium secondary battery.

[0085] The lithium sensing device is electrically connected to the lithium secondary battery and can track the potential change of the sensing probe in real time, thereby determining the deposition of lithium metal in the negative electrode during initial charging.

[0086] To this end, the lithium sensing device may include a support part on which the above-mentioned lithium secondary battery of the present invention is mounted, and a control part electrically connected to the lithium secondary battery mounted on the support part, for controlling initial charging of the lithium secondary battery according to the potential of the sensing probe and determining whether or not lithium metal is deposited.

[0087] More specifically, the lithium secondary battery may further include a battery management system (BMS) to which the sensing probe is electrically connected and which measures the potential of the sensing probe in real time, and the battery management system may be electrically connected to a control unit of the lithium sensing device and transmit the measured potential of the sensing probe to the control unit. When the potential of the sensing probe transmitted from the battery management system exceeds a preset value, for example, 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, or 2.5V, the control unit may determine that lithium metal has been deposited on the negative electrode of the lithium secondary battery and determine the target lithium secondary battery as defective, and when the potential of the sensing probe reaches a flat potential of 1.3V to 1.8V without a sudden potential change, the control unit may determine that the target lithium secondary battery is a normal lithium secondary battery and terminate the initial charge of the lithium secondary battery. Here, the sudden potential change of the sensing probe means that the potential change of the sensing probe is 0.5V or more in a unit time during which the initial charge is performed, for example, 30±5 seconds during which the initial charge is performed.

[0088] In addition, the lithium sensing device may further include an electrolyte injection unit for injecting electrolyte into the assembled lithium secondary battery before initial charging of the lithium secondary battery, and the electrolyte injection unit may have the same configuration as a device commonly used in the art for injecting electrolyte into a lithium secondary battery.

[0089] The lithium sensing device according to the present invention can be used in or attached to a device / equipment used in an initial activation process during the manufacture of a lithium secondary battery, and / or can be used in a test device / equipment during the development of a lithium secondary battery.

[0090] The present invention will now be described in more detail with reference to examples and experimental examples.

[0091] However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0092] <Production Examples 1 to 4. Production of sensing probe> N-methyl-2-pyrrolidone was poured into a reactor, and 98 parts by weight of the metal oxide shown in Table 1 below and 2 parts by weight of polyvinylidenefluoride (PVDF) were added to the reactor based on the solid content, and mixed to prepare a slurry. Separately, a copper conductor having an average diameter of 120±10 μm was prepared, and the surface was coated with the slurry prepared above, and then dried at 130° C. for 1 hour to prepare a sensing probe (average diameter: 220±10 μm).

[0093] [Table 1]

[0094] <Examples 1-2 and Comparative Examples 1-2. Production of Lithium Secondary Batteries> To form the positive electrode composite layer, LiNi 0.8 Co 0.1 Mn 0.1 O 2 94 parts by weight of ZnO, 3 parts by weight of carbon black as a conductive material, and 3 parts by weight of PVDF as a binder were weighed and mixed at 3,000 rpm for 60 minutes to prepare a positive electrode slurry. The prepared positive electrode slurry was applied to one side of an aluminum current collector, dried at 100°C, and rolled to manufacture a positive electrode. At this time, the total thickness of the positive electrode mixture layer was 130 μm, and the total thickness of the manufactured positive electrode was about 200 μm.

[0095] In addition, 99 parts by weight (94.05 parts by weight and 4.95 parts by weight, respectively) of natural graphite and silicon (SiOx, where 1≦x≦2) particles as negative electrode active materials and 1 part by weight of styrene butadiene rubber (SBR) as a binder were prepared, and a negative electrode slurry was prepared in the same manner as the method for producing the positive electrode slurry. At this time, the graphite used in producing the negative electrode mixture layer was natural graphite (average particle size: 0.01 to 0.5 μm), and the silicon (SiOx) particles had an average particle size of 0.9 to 1.1 μm. The prepared negative electrode slurry was applied to one side of a copper current collector, dried at 100 ° C., and rolled to produce a negative electrode. At this time, the total thickness of the negative electrode mixture layer was 150 μm, and the total thickness of the produced negative electrode was about 250 μm.

[0096] Next, a separator (thickness: about 16 μm) made of a porous polyethylene (PE) film was interposed between the prepared positive and negative electrodes, and the resulting battery was inserted into a battery pouch, after which the sensing probe prepared in the Preparation Example was disposed on the side of the negative electrode composite layer and electrically connected to the positive electrode for charging the sensing probe. The position where the sensing probe was disposed is shown in Table 2 below with reference to FIG. 3.

[0097] Then, E2DVC was injected into the battery pouch as an electrolyte to fabricate a full cell. Here, E2DVC is a type of carbonate-based electrolyte, which is a mixture of ethylene carbonate (EC): dimethyl carbonate (DMC): diethyl carbonate (DEC) = 1:1:1 (volume ratio) and lithium hexafluorophosphate (LiPF 6 , 1.0 M) and vinyl carbonate (VC, 2 wt %).

[0098] [Table 2]

[0099] <Example 3 and Comparative Examples 3 to 4. Production of Lithium Secondary Batteries> A lithium secondary battery was manufactured in the same manner as in Example 1, except that the sensing probes manufactured in Preparation Examples 2 to 4 were used instead of the sensing probe manufactured in Preparation Example 1, as shown in Table 3 below.

[0100] [Table 3]

[0101] <Experimental Example> In order to evaluate the safety of the lithium secondary battery according to the present invention, the following experiment was carried out.

[0102] First, an electrode assembly was prepared by stacking the positive electrode composite layer and the negative electrode composite layer on the separator so that they were misaligned with each other, and the lithium secondary batteries of Examples 4 to 6 and Comparative Examples 5 to 8 were manufactured in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 4, respectively, except that a sensing probe was disposed at the part where the composite layers were stacked in a misaligned manner. Furthermore, in order to confirm the presence or absence of lithium metal deposition due to the misalignment when stacking the positive electrode composite layer and the negative electrode composite layer, and the effect of the lithium metal sensing electrode, a lithium secondary battery in which the positive electrode composite layer and the negative electrode composite layer were not misaligned was separately prepared as a control group.

[0103] Next, each lithium secondary battery was charged so that the state of charge (SOC) of the sensing probe provided on the prepared lithium secondary battery was 40% to 60%, and the initial charging of each lithium secondary battery was performed to observe the potential change of the sensing probe provided on each lithium secondary battery. At this time, the initial charging was performed at a temperature of 25°C with a charging current of 0.3C to a charge end voltage of 4.2 to 4.25V, and the current density at the end voltage was 0.02C. In addition, when the potential of the sensing probe was observed, if the potential suddenly increased and exceeded 2.0V, it was displayed as "○". After the initial charging of the lithium secondary battery was completed, the battery was disassembled to confirm the presence or absence of lithium metal deposition on the negative electrode. The measurement results are shown in Table 4 and FIG. 4 below.

[0104] [Table 4]

[0105] Referring to Table 4 and FIG. 4, it can be seen that the lithium secondary battery according to the present invention can sense deposition on the negative electrode in real time.

[0106] Specifically, first, in reference to the control group, it was confirmed that when the positive electrode composite layer and the negative electrode composite layer are stacked with a misalignment, lithium is precipitated on the side surface of the negative electrode composite layer, but when the composite layers are stacked without a misalignment, lithium metal is not precipitated on the side surface of the negative electrode composite layer.

[0107] In addition, when the lithium secondary batteries of Examples 4 to 6 according to the present invention were disassembled and the negative electrodes were observed at the point in time when the electrode potential of the sensing probe containing a metal oxide having a plateau potential of 1.3 V to 1.8 V exceeded 2.0 V, it was confirmed that lithium metal was deposited on the side of the negative electrode composite layer and contacted the sensing probe.

[0108] In contrast, in the lithium secondary battery of Comparative Example 5, which does not have a sensing probe, lithium metal was deposited on the side of the negative electrode composite layer, making it difficult to detect changes in the secondary battery in real time. Furthermore, in the lithium secondary battery of Comparative Example 6, in which the sensing probe is located on the surface of the composite layer rather than on the side of the negative electrode composite layer, a short circuit occurs between the negative electrode and the sensing probe during the charge / discharge process of the secondary battery, making it difficult to measure the potential. In addition, in the lithium secondary batteries of Comparative Examples 7 and 8, in which the plateau potential of the metal oxide contained in the sensing probe is outside the range of 1.3V to 1.8V, when the lithium metal deposited on the side of the negative electrode composite layer comes into contact, there is a change in the plateau potential, but the change is not large or only occurs to the extent that corresponds to the plateau potential, making it difficult to confirm the presence or absence of lithium metal deposition in real time.

[0109] From these results, it can be seen that if a positive electrode composite layer is stacked on the surface of a negative electrode composite layer with a separator interposed therebetween during the manufacture of a lithium secondary battery, lithium metal is deposited on the side of the stacked negative electrode composite layer during initial charging of the lithium secondary battery. The lithium secondary battery according to the present invention is provided with a sensing probe including a metal oxide having a plateau potential of 1.3V to 1.8V on the side of the negative electrode composite layer, so that the deposited lithium metal can be confirmed in real time in a non-destructive manner. This not only reduces the defective rate during manufacture, but also improves degradation of the lithium secondary battery, such as capacity loss, thereby increasing the lifespan and improving the safety of the lithium secondary battery.

[0110] Although the present invention has been described above with reference to preferred embodiments, it will be understood that a person skilled in the art or having ordinary knowledge in the art can make various modifications and variations to the present invention without departing from the spirit and technical scope of the present invention as described in the claims below.

[0111] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims. [Explanation of symbols]

[0112] 10 Electrode assembly 12 Negative electrode 13 Separation membrane 30 Electrode Tap 100, 200 Lithium secondary battery 110 Electrode assembly 111, 211 positive electrode 112, 212 negative electrode 113, 213 Separation membrane 114, 214 Welding Section 120, 220 Battery case 130, 230 Electrode tap 140, 240 Sensing probe S Exposed positive electrode composite layer area

Claims

1. The battery includes an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed between the negative electrode current collector and a separator, A lithium secondary battery comprising a sensing probe having a plateau potential of 1.3 V to 1.8 V and including a metal oxide on a side of the negative electrode mixture layer, The sensing probe is a probe for non-destructively detecting in real time whether or not lithium metal deposition occurs on the negative electrode during initial charging of the lithium secondary battery. The lithium secondary battery is charged to a state of charge (SOC) of 40 to 60%, and a potential of the sensing probe is measured using the sensing probe that embodies the plateau potential of 1.3 V to 1.8 V. If the measured potential of the sensing probe exceeds 2.0 V, it is determined that the lithium metal has been deposited.

2. 2. The lithium secondary battery according to claim 1, wherein the sensing probe is a wire structure including a core wire containing a conductive metal and a metal oxide layer surrounding the core wire.

3. The lithium secondary battery according to claim 1 , wherein the sensing probe has an average diameter of 10 to 200 μm.

4. The lithium secondary battery according to claim 1 , wherein the average diameter of the sensing probe is smaller than the average thickness of the negative electrode mixture layer.

5. The lithium secondary battery of claim 1 , wherein the sensing probe is disposed 0.1 to 2,000 μm away from a side surface of the negative electrode mixture layer.

6. 2. The lithium secondary battery according to claim 1, wherein the metal oxide is an oxide containing one or more metals selected from the group consisting of titanium, vanadium, iron, cobalt, nickel, copper, molybdenum, tungsten and niobium.

7. The metal oxide is a lithium titanate compound represented by the following chemical formula 1: [Chemical formula 1] LiaTibMcOd In the above Chemical Formula 1, M is Sn, Cr, Y, Nb, Mg, Zn, Ni, V, Na, K, Ca, Co, Ta, Mo, Zr, Al, Cu, Mn or Bi, a is an integer satisfying 0.4≦a≦5, b is an integer satisfying 0.5≦b≦5.5, c is an integer satisfying 0≦c≦0.9, 2. The lithium secondary battery according to claim 1, wherein d is an integer satisfying 1.5≦d≦12.

5.

8. 2. The lithium secondary battery of claim 1, wherein the sensing probe comprises the metal oxide charged at a state of charge (SOC) of 40% to 60%.

9. placing an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode in a secondary battery case, and disposing a sensing probe including a metal oxide having a plateau potential of 1.3 V to 1.8 V on a side of the negative electrode mixture layer of the negative electrode to assemble a lithium secondary battery; filling an electrolyte into the assembled lithium secondary battery case; charging the electrolyte-filled lithium secondary battery; measuring a potential of a sensing probe provided on the lithium secondary battery; A method for producing a lithium secondary battery, comprising: The sensing probe is a probe for non-destructively detecting in real time whether or not lithium metal deposition occurs on the negative electrode during initial charging of the lithium secondary battery, and the potential of the sensing probe is measured using a sensing probe that embodies the plateau potential of 1.3V to 1.8V by charging the battery to a state of charge (SOC) of 40 to 60%, and it is determined that the lithium metal has been deposited when the measured potential of the sensing probe exceeds 2.0V.

10. The method of claim 9, wherein the sensing probe is charged at a state of charge (SOC) of 40% to 60%.

11. After the step of measuring the potential of the sensing probe, 10. The method of claim 9, further comprising: determining that the lithium secondary battery is defective if the measured potential of the sensing probe exceeds 2.0V.

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