KR102148506B1 - Anode Comprising Mesh Type Current Collector, Lithium Secondary Battery Comprising the Same and Manufacturing Method thereof - Google Patents

Abstract

The present invention relates to a negative electrode for a lithium secondary battery including a current collector in the form of a mesh and a lithium thin film, and more particularly, a negative electrode in which a lithium thin film is introduced into an opening of the current collector and an empty space is formed, a lithium secondary battery including the same, and It relates to a method of manufacturing the same.
According to the present invention, it is possible to prevent the growth of lithium dendrites, thereby improving the safety of a lithium secondary battery. In addition, the adhesion efficiency between the negative electrode and the current collector may be increased, and thus the negative electrode current collector and the lithium thin film may be prevented from being separated during charging and discharging of the battery.

Description

Anode Comprising Mesh Type Current Collector, Lithium Secondary Battery Comprising the Same and Manufacturing Method thereof, including a negative electrode including a mesh-type current collector, and a lithium secondary battery including the same

The present invention relates to a negative electrode for a lithium secondary battery including a current collector in the form of a mesh and a lithium thin film, and more particularly, a negative electrode in which a lithium thin film is introduced into an opening of the current collector and an empty space is formed, a lithium secondary battery including the same, and It relates to a method of manufacturing the same.

Recently, interest in energy storage technology is increasing. As the fields of application to mobile phones, camcorders, notebook PCs, and even electric vehicles are expanded, efforts for research and development of electrochemical devices are increasingly being materialized.

Electrochemical devices are the field that is receiving the most attention in this respect, and among them, the development of secondary batteries capable of charging and discharging has become the focus of interest, and recently, in developing such batteries, in order to improve capacity density and energy efficiency. Research and development on the design of new electrodes and batteries is ongoing.

Among the secondary batteries currently applied, the lithium secondary battery developed in the early 1990s has the advantage of having a higher operating voltage and significantly higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries using aqueous electrolyte solutions. It is in the limelight.

In general, a lithium secondary battery is built in a battery case in a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode is stacked or wound, and is constructed by injecting a non-aqueous electrolyte into the battery case. As a negative electrode, a lithium electrode is used by attaching a lithium foil on a planar current collector. In this case, lithium dendrites are formed due to irregular formation and removal of lithium during charging and discharging, which leads to a continuous decrease in capacity.

To solve this problem, research has been conducted to introduce a polymer protective layer or an inorganic solid protective layer to the lithium metal layer, increase the concentration of salt in the electrolyte, or apply an appropriate additive. However, the inhibitory effect of these studies on lithium dendrite is insignificant. Therefore, it may be an effective alternative to solve the problem through the shape modification of the lithium metal anode itself or the structure of the battery.

Korean Patent Publication No. 10-1621410 "Lithium electrode and lithium secondary battery including the same"

As described above, the lithium dendrites of the lithium secondary battery are deposited on the surface of the negative electrode current collector, thereby causing volume expansion of the cell. Accordingly, the inventor of the present invention has conducted various studies, and as a result, found a method that can solve the problem caused by dendrites by modifying the shape and structure of the electrode itself, and completed the present invention.

Accordingly, an object of the present invention is to solve the problem of volume expansion of a cell due to lithium dendrite by modifying the shape and structure of an electrode, and to provide a lithium secondary battery with improved cell performance.

The present invention in order to achieve the above object is a negative electrode current collector in the form of a mesh (mesh) consisting of a wire portion and an opening; And a lithium thin film comprising a lead-in portion and a non-intrusion portion of the negative electrode current collector.

In addition, the present invention comprises the steps of preparing a mesh-type negative electrode current collector; Placing a lithium metal foil on the negative electrode current collector; And rolling the lithium metal foil and a negative electrode current collector so that the lithium metal is introduced into an opening of the negative electrode current collector.

In addition, the present invention provides a lithium secondary battery including the negative electrode.

According to the present invention, the negative electrode for a lithium secondary battery in which a part of the lithium thin film is drawn into the negative electrode current collector can increase the surface area of the lithium thin film and the negative electrode current collector, thereby improving the performance of the lithium secondary battery and distributing electrons in the lithium electrode. When the lithium secondary battery is driven, the growth of lithium dendrites can be prevented through uniformization of the lithium secondary battery, thereby improving the safety of the lithium secondary battery.

In addition, as a part of the lithium thin film is introduced into the opening of the negative electrode current collector, the generation of lithium dendrites is induced into an empty space, thereby preventing the cell from expanding in volume.

In addition, compared to the conventional simple bonding structure, since the lead-in portion of the lithium thin film and the opening of the negative electrode current collector are joined in a fitting manner, the adhesion efficiency can be increased, thereby preventing the negative electrode current collector and the lithium thin film from peeling off during charging and discharging of the battery can do.

1 is a cross-sectional view of a negative electrode for a lithium secondary battery including a lithium thin film introduced into an opening of a negative electrode current collector according to the present invention.
2 is a perspective view illustrating a method of manufacturing a negative electrode for a lithium secondary battery according to the present invention.
3 is a schematic diagram of a step-by-step explaining a method of manufacturing a negative electrode for a lithium secondary battery according to the present invention.
4 is an image of a mesh-type negative electrode current collector applied in Example 1 of the present invention.
5 is an SEM image of a mesh-type negative electrode current collector applied in Example 1 of the present invention.
6 is an image of a negative electrode for a lithium secondary battery according to Example 1 of the present invention.
7 is an SEM image of a negative electrode for a lithium secondary battery according to Example 1 of the present invention.
8 is an initial capacity and efficiency data of a lithium secondary battery to which the negative electrode according to Example 1 and Comparative Example 1 of the present invention is applied.
9 is data comparing rate performance of a lithium secondary battery to which a negative electrode according to Example 1 and Comparative Example 1 of the present invention is applied.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement it. However, the present invention may be implemented in various different forms, and is not limited to this specification.

In the drawings, parts not related to the description are omitted in order to clearly describe the present invention, and similar reference numerals are used for similar parts throughout the specification. In addition, the size and relative size of the components indicated in the drawings are not related to the actual scale, and may be reduced or exaggerated for clarity of description.

1 is a cross-sectional view of a negative electrode for a lithium secondary battery including a lithium thin film introduced into an opening of a negative electrode current collector according to the present invention. Referring to Figure 1, the present invention is a negative electrode current collector 100 in the form of a mesh (mesh) consisting of a wire portion 120 and an opening 110; And it presents a negative electrode for a lithium secondary battery including a lithium thin film 200 made of a lead-in portion 210 and a non-introductory portion 220 that is lead through the opening 110 of the negative electrode current collector 100.

The negative electrode for a lithium secondary battery according to the present invention has a structure in which a lithium thin film 200 is inserted in a state in which one surface is in contact with the upper surface of the mesh-shaped negative electrode current collector 100, whereby a part of the lithium thin film 200 is a negative electrode collector. As it is introduced into the opening 110 of the entire 100, an empty space of the opening 110 is left. As lithium dendrite is generated in this space, volume expansion of the cell can be prevented.

In the present invention, the electrode material formed on the negative electrode current collector 100 is preferably a lithium thin film 200. The lithium thin film 200 has the characteristic malleability and ductility of a metal film, and since it spreads thinly and changes shape when pressure is applied, it can be formed into the mesh-shaped negative electrode current collector opening 110 by only a predetermined rolling process. You can bring it in.

However, among materials applied as a negative electrode to a lithium secondary battery, in the case of a negative electrode active material containing lithium in a form other than a thin film form, a predetermined coating process is usually performed in which a slurry mixture is prepared and applied to the negative electrode current collector. Unlike lithium in the form of a thin film, this slurry mixture has difficulty in introducing it into the opening of the negative electrode current collector in the form of a mesh through a coating film forming process or a subsequent rolling process, as well as a possibility of cracking due to the pressure applied in the rolling process. have. Even if the viscosity of the slurry mixture is adjusted to be introduced into the opening of the negative electrode current collector, it is very difficult to control the degree of securing the desired empty space in the present invention.

Therefore, in the present invention, the lithium thin film 200 is preferably applied as the negative electrode material, and the thickness d210 of the lead-in portion of the lithium thin film 200 is adjusted to be 20 to 60% of the total lithium thin film. That is, the space filled with the lead-in portion 210 of the lithium thin film among the space of the opening 110 of the negative electrode current collector is 20 to 60% of the entire lithium thin film, and thus, the empty space in the opening 100 space is maintained. do. Dendrites are formed in the remaining space of the opening 100 while charging and discharging, so that volume expansion of the cell may be prevented.

In this case, it is preferable that the thickness d220 of the non-retracted portion of the lithium thin film 200 leaves 40 to 80% of the total lithium thin film thickness d200 and only the remaining portion is introduced. If a portion of the lithium thin film 200 is not completely drawn in and left, a space is left inside the negative electrode current collector 100, and the above-described effects can be secured. In addition, as both surfaces of the lithium thin film 200 are exposed to the electrolyte, a stable SEI film is formed on both surfaces, thereby preventing the Li metal surface from being exposed, thereby preventing electrolyte degradation due to charge and discharge.

The thickness (d200) of the lithium thin film is selected from 10 to 800㎛, but it is preferable to select a thickness thicker than the thickness of the negative electrode current collector. The reason for this is to secure a sufficient thickness of the non-retracted portion 220 even when the lithium thin film 200 is introduced into the opening 110 of the negative electrode current collector.

In addition, the negative electrode current collector 100 is applied in a thickness range of 3 to 500㎛. If the thickness of the negative electrode current collector is less than 3 μm, the current collecting effect is degraded, and the opening 110 of a sufficient size for collecting lithium dendrites is not secured. On the other hand, if the thickness exceeds 500 μm, the cell is folded. In the case of assembling, there is a problem that the workability is deteriorated.

The smaller the size of one opening 110 of the negative electrode current collector 100 and the larger the ratio occupied by the opening 110 is, the better the lithium dendrite growth suppression effect is. More specifically, the wire member 120 of the negative electrode current collector 100 may have a line width of 50 to 500 µm and a line spacing of 100 µm to 1 mm, and the opening 110 formed by the wire member 120 ) One size is preferably 10 ~ 300㎛ to ensure the above effect.

In addition, the ratio of the openings 110 in the negative electrode current collector 100 is preferably 20 to 80%, which is the ratio of the area occupied by the openings 110 based on 100% of the total area of the negative electrode current collector 100. Do. If the aperture ratio is less than 20%, the effect of inducing the precipitation and removal reaction of lithium dendrites, which is the object of the present invention, cannot be secured. If the aperture ratio exceeds 80%, the contact area between the negative electrode current collector and the lithium metal layer is relatively It decreases, and the performance of the battery is deteriorated because it is not appropriate to function as a negative electrode current collector.

The shape of the opening 110 formed by the wire portion 120 of the negative electrode current collector 100 is not limited, and may be, for example, a circular, elliptical, or polygonal shape.

The negative electrode current collector 100 is not particularly limited as long as it has high conductivity without causing chemical changes to the battery, and copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, It may be selected from the group consisting of alloys and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium, or silver, and an aluminum-cadmium alloy may be used as the alloy, and in addition, non-conductive polymer surface-treated with calcined carbon, conductive material, or conductive polymer, etc. You can also use In general, a thin copper plate is used as the negative electrode current collector.

According to the present invention, the negative electrode for a lithium secondary battery in which a part of the lithium thin film is introduced into the negative electrode current collector increases the surface area of the lithium thin film and the negative electrode current collector, uniformizes the electron distribution in the lithium electrode, By inducing dry matter to precipitate, the safety of the lithium secondary battery can be improved.

Further, the present invention is a negative electrode current collector in the form of a mesh (mesh) consisting of a wire portion and an opening; A lithium thin film comprising a lead-in portion introduced into an opening portion of the negative electrode current collector and a non-intrusion portion not lead-in; And a protective structure formed on an opposite surface of the lithium thin film facing the negative electrode current collector, wherein the protective structure comprises an organic polymer part and an inorganic material part, wherein the organic polymer part is on the opposite surface of the lithium thin film in contact with the wire rod part, It provides a negative electrode for a lithium secondary battery, characterized in that the inorganic material portion is generated on the opposite surface of the lithium thin film corresponding to the opening.

The protective structure according to the present invention can provide an ion path between the cathode and the electrolyte. Such a protective structure is a shape in which an inorganic material is filled between the frames formed by the organic polymer part, and an inorganic material cell or layer made of a specific ceramic/glassy material, pinholes, cracks, and /Or may include grain boundary defects, but the presence of multiple ion pathways can minimize the effect of defects in any one ion pathway. Thus, in such a protective structure, if a defect is present, it is typically much less fatal than it is in a protective structure comprising one or more continuous ceramic layers. For example, because defects can be isolated (e.g., at least partially surrounded by a polymeric material), propagation of the defects to other ion pathways (e.g., inorganic material-filled cavities) can be reduced or avoided. have.

The organic polymer part provides advantageous mechanical properties such as flexibility and strength of the protective structure. Placing a cell filled with inorganic material inside the polymer frame can reduce the vulnerability of the inorganic material-filled cavity to the cracking mechanism. The material is not limited, but may be selected from polyvinyl alcohol, polyisobutylene, epoxy, polyethylene, polypropylene, polytetrafluoroethylene, and combinations thereof as a non-ionic conductive polymer.

The inorganic material part is a material in ionic communication with the lithium thin film, and may be a ceramic material or a glass material, such as Li ₂ O, Li ₃ N, Al ₂ O ₃ , ZrO ₂ , SiO ₂ , CeO ₂ , Al ₂ TiO ₅ , oxy-sulfide glass and combinations thereof.

For example, the protective structure may be manufactured by forming a frame with an organic polymer part along a wire part forming a mesh shape of a negative electrode current collector, and then filling the frame with an inorganic material. The method includes electron beam deposition, sputtering, and It is possible to apply a method such as thermal evaporation.

2 and 3 are perspective and step-by-step schematic diagrams illustrating a method of manufacturing a negative electrode for a lithium secondary battery according to the present invention. Inserting the lithium thin film 200 into the opening 110 formed by the mesh-shaped negative electrode current collector 100 may be achieved by placing the lithium thin film 200 on the negative electrode current collector 100 and then performing a rolling process. have. More specifically, the present invention comprises the steps of: i) preparing a negative electrode current collector 100 in a mesh shape; Ii) placing a lithium thin film 200 on the negative electrode current collector 100; And iii) rolling the lithium thin film 200 and the negative electrode current collector 100 so that the lithium thin film 200 is introduced into the opening 110 of the negative electrode current collector 100; including a negative electrode for a lithium secondary battery. Provides a manufacturing method.

The rolling step may be carried out according to a conventional method, for example, by pressing with a pressing roller 300 provided in a roll press, or by pressing over the entire electrode with a plate-shaped press, and a lithium thin film 200 May be introduced into the opening 110 of the negative electrode current collector 100.

In particular, in this rolling process, a pressure of 10 kg/cm 2 to 100 ton/cm 2 may be applied and heated to a temperature of 100 to 200°C. The heat treatment at the temperature includes heating while performing the rolling process, or performing the rolling process in a heated state before performing the rolling process. By controlling the temperature and pressure conditions, the degree of lead-in of the lithium thin film can be controlled, and preferably, the roll may be performed to satisfy the inlet thickness d210 of the above-described range.

The lithium secondary battery according to the present invention can be manufactured through a known technique performed by a person skilled in the art for the remaining configurations except for the structure and characteristics of the negative electrode described above, and will be described in detail below.

The positive electrode according to the present invention may be prepared in the form of a positive electrode by forming a composition including a positive electrode active material, a conductive material, and a binder on a positive electrode current collector.

The positive electrode active material is LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li(Ni _a Co _b Mn _c )O ₂ (0<a<1, 0<b<1, 0<c<1, a+ b+c=1), LiNi _{1 - y} CoyO ₂ , LiCo _{1 - y} MnyO ₂ , LiNi _{1 - y} MnyO ₂ (O≤≤y<1), Li(Ni _a Co _b Mn _c )O ₄ (0<a<2,0<b<2,0<c<2, a+b+c=2), LiMn _{2 - z} NizO ₄ , LiMn _{2 - z} CozO ₄ (0<z<2), LiCoPO ₄ and LiFePO Any one selected from the group consisting of ₄ or a mixture of two or more of them may be used. In addition, in addition to these oxides, sulfide, selenide, and halide may be used. In a more preferred example, the positive active material may be LiCoO ₂ suitable for high-power batteries.

The conductive material is a component for further improving the conductivity of the positive electrode active material, and non-limiting examples include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum, 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 may be used.

The binder holds the positive electrode active material in the positive electrode current collector and has a function of organically connecting the positive electrode active materials, for example, polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), carboxymethylcellulose ( CMC), starch, hydroxypropylcellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine Rubber, and various copolymers thereof.

The positive electrode current collector is the same as described above for the negative electrode current collector, and generally, an aluminum thin plate may be used as the positive electrode current collector.

The positive electrode composition may be coated on the positive electrode current collector using a conventional method known in the art, for example, a dipping method, a spray method, a roll court method, a gravure printing method. , A bar court method, a die coating method, a comma coating method, or a mixing method thereof may be used.

The positive electrode and the positive electrode composition that has undergone such a coating process are then dried through a drying process to evaporate a solvent or a dispersion medium, and obtain a dense coating layer and adhesion between the coating layer and the current collector. At this time, drying is performed according to a conventional method, and this is not particularly limited.

The separation membrane according to the present invention is not particularly limited in its material, and physically separates the anode and the cathode, and has electrolyte and ion permeability, and can be used without particular limitation as long as it is commonly used as a separator in an electrochemical device. As a porous, non-conductive or insulating material, in particular, it is preferable that the electrolyte has low resistance to ion migration and excellent electrolyte-moisturizing ability. For example, a polyolefin-based porous membrane or a nonwoven fabric may be used, but is not particularly limited thereto.

Examples of the polyolefin-based porous membrane include polyolefin-based polymers such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polyolefin-based polymers such as polypropylene, polybutylene, and polypentene, respectively, or a mixture of them. There is one act.

The nonwoven fabric is, for example, polyphenyleneoxide, polyimide, polyamide, polycarbonate, polyethylene terephthalate, polyethylenenaphthalate, in addition to the above-described polyolefin nonwoven fabric. , Polybutyleneterephthalate, polyphenylenesulfide, polyacetal, polyethersulfone, polyetheretherketone, polyester, etc., either alone or A nonwoven fabric formed of a polymer mixture of these can be used, and such a nonwoven fabric is a fiber form forming a porous web, and includes a spunbond or meltblown form composed of long fibers.

The thickness of the separator is not particularly limited, but is preferably in the range of 1 to 100 µm, and more preferably in the range of 5 to 50 µm. When the thickness of the separator is less than 1 µm, mechanical properties cannot be maintained, and when the thickness of the separator exceeds 100 µm, the separator acts as a resistive layer, thereby deteriorating battery performance.

The pore size and porosity of the separator are not particularly limited, but the pore size is preferably 0.1 to 50 μm, and the porosity is preferably 10 to 95%. If the pore size of the separator is less than 0.1 μm or the porosity is less than 10%, the separator acts as a resistive layer, and if the pore size exceeds 50 μm or the porosity exceeds 95%, mechanical properties cannot be maintained. .

The electrolyte applicable in the present invention may be a non-aqueous electrolyte solution or a solid electrolyte that does not react with lithium metal, but is preferably a non-aqueous electrolyte, and includes an electrolyte salt and an organic solvent.

The electrolyte salt contained in the non-aqueous electrolyte solution is a lithium salt. As the lithium salt, those commonly used in an electrolyte for a lithium secondary battery may be used without limitation. For example is the above lithium salt anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF _{^{4 -, (CF 3) 3}} PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 - _{, (CF 3 SO 2) 2} N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, ( CF ₃ SO _{2) 3} C ^- from the group consisting of ^{_{-, CF 3 (CF 2)}} 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and _{(CF 3 CF 2 SO 2)} 2 N Any one selected or two or more of them may be included.

As organic solvents included in the non-aqueous electrolyte, those commonly used in electrolytes for lithium secondary batteries can be used without limitation, for example, ether, ester, amide, linear carbonate, cyclic carbonate, etc., alone or in combination of two or more Can be used. Among them, representatively, a cyclic carbonate, a linear carbonate, or a carbonate compound that is a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, Any one selected from the group consisting of 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or a mixture of two or more thereof. These halides include, for example, fluoroethylene carbonate (FEC), but are not limited thereto.

In addition, specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, or these A mixture of two or more of them may be typically used, but is not limited thereto.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are organic solvents with high viscosity and have high dielectric constants, so that lithium salts in the electrolyte can be more easily dissociated, such as dimethyl carbonate and diethyl carbonate. If a low viscosity, low dielectric constant linear carbonate is mixed in an appropriate ratio and used, an electrolyte solution having a higher electrical conductivity can be prepared.

In addition, as the ether of the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, and ethylpropyl ether, or a mixture of two or more thereof may be used. , But is not limited thereto.

And esters in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ -Any one selected from the group consisting of valerolactone and ε-caprolactone, or a mixture of two or more of them may be used, but the present invention is not limited thereto.

The injection of the non-aqueous electrolyte may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process and required physical properties of the final product. That is, it can be applied before assembling the electrochemical device or at the final stage of assembling the electrochemical device.

In the lithium secondary battery according to the present invention, in addition to winding, which is a general process, lamination and stacking of a separator and an electrode and folding are possible. In addition, the battery case may be a cylindrical shape, a square shape, a pouch type, or a coin type.

As described above, since the lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics and capacity retention rate, portable devices such as mobile phones, notebook computers, and digital cameras, and hybrid electric vehicles (HEVs) ), etc. It is useful in electric vehicle fields.

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided. The battery module or battery pack may include a power tool; Electric vehicles, including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it may be used as a power source for any one or more medium and large-sized devices in a power storage system.

Hereinafter, examples will be described in detail to illustrate the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art.

Example: Manufacture of lithium secondary battery

<Example 1>

A lithium foil having a thickness of 40 μm was placed on a 25 μm thick copper mesh (shown in FIGS. 4 and 5) as an anode current collector, pressure was applied so that 50% of the lithium foil was drawn in, and roll pressed at room temperature to (Shown in Figs. 6 and 7) was prepared.

A positive electrode was prepared by forming a positive electrode active material: carbon black: a binder (KF9700) in a composition of 95.5:2.0:2.5 on an aluminum foil having a thickness of 12㎛ as a positive electrode current collector.

As a separator, a secondary battery was manufactured using a separator in which SRS was coated on both sides of 8 μm polyethylene (PE) fabric by 2.5 μm. FEC/DEC was used as an electrolyte, and a lithium secondary battery was manufactured using an electrolyte containing 1M of LiPF ₆ and 0.5 wt% of an additive.

<Example 2>

Example 1 and Example 1 except that a lithium foil having a thickness of 40 μm was placed on a copper mesh having a thickness of 25 μm (shown in FIGS. 4 and 5) as a negative electrode current collector, and 40% of the lithium foil was introduced. A lithium secondary battery was manufactured under the same conditions.

<Example 3>

Example 1, except that a lithium foil having a thickness of 40 μm was placed on a copper mesh having a thickness of 25 μm (shown in FIGS. 4 and 5) as a negative electrode current collector, and 30% of the lithium foil was adjusted to be introduced. A lithium secondary battery was manufactured under the same conditions as.

<Example 4>

Example 1 and Example 1 except that a lithium foil having a thickness of 40 μm was placed on a copper mesh having a thickness of 25 μm (shown in FIGS. 4 and 5) as a negative electrode current collector and adjusted so that 20% of the lithium foil was introduced. A lithium secondary battery was manufactured under the same conditions.

<Example 5>

Example 1, except that a lithium foil having a thickness of 40 μm was placed on a copper mesh having a thickness of 25 μm (shown in FIGS. 4 and 5) as a negative electrode current collector, and 10% of the lithium foil was adjusted to be introduced. A lithium secondary battery was manufactured under the same conditions as.

<Comparative Example 1>

A copper foil having a thickness of 20 μm was applied as a negative electrode current collector, and a lithium secondary battery was manufactured under the same conditions as in Example 1 without performing a rolling process of the negative electrode.

<Experimental Example 1>

The lithium secondary batteries of Examples 1 to 5 and Comparative Example 1 were subjected to charge/discharge tests under 0.1C charge/0.1C discharge conditions, and the results are shown in FIG. 8 and summarized in Table 1 below.

Charging capacity (mAh/g) Discharge capacity (mAh/g) efficiency(%) Example 1 225 210 93.22 Example 2 224 209 93.30 Example 3 225 209 92.88 Example 4 226 210 92.92 Example 5 224 209 93.30 Comparative Example 1 226 210 93.14

As can be seen from Table 1, the initial charge/discharge capacity and efficiency of the lithium secondary batteries of Examples 1 to 5 and Comparative Example 1 were similar.

<Experimental Example 2>

9 and Table 2 are data comparing the rate performance of a lithium secondary battery to which a negative electrode according to Examples 1 to 5 of the present invention is applied and Comparative Example 1.

Capacity retention (%, compared to 0.1C) Discharge
C-rate Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 0.5C/0.1C 92.50 92.30 92.10 91.95 91.80 91.37 1.0C/0.1C 85.05 83.55 82.10 80.05 78.05 75.46 2.0C/0.1C 66.40 63.35 60.20 55.05 51.05 43.63 3.0C/0.1C 44.60 38.66 32.55 27.05 22.10 13.99

The charging rate was fixed, and the capacity retention rate was confirmed while increasing the discharge C-rate. The results shown in the table indicate the capacity expression rate compared to 0.1C, and the 0.1C capacity was the same for the lithium secondary batteries of Example 1 and Comparative Example 1. However, when the discharge rate is increased, the lithium secondary batteries of Examples 1 to 5 have higher capacity retention rates than the lithium secondary batteries of Comparative Example 1. As the C-rate increases, the difference increases. When discharging at 2.0C, the lithium secondary battery of Example 1 exhibits a capacity retention rate of 66%, but exhibits a capacity retention rate of 44% of the lithium secondary battery of Comparative Example 1, and the difference is about 22%. The lithium secondary batteries of Examples 2 to 5 also exhibited excellent capacity retention compared to Comparative Example 1.

That is, when mesh Cu is used, the area where Li metal and Cu contact is increased, and the electrical conductivity is improved, and the internal resistance of the cell can be lowered. In addition, it improves cell performance while inducing dendrite formation in the empty space of the previously described opening. In the case of using general mesh Cu, dendrite is formed on the surface of Li metal in contact with the separator during charging and discharging, increasing the interface resistance between the separator and the Li metal. In addition, even after charging and discharging, an increase in the interface resistance between the Li metal and the separator can be prevented.

100. Anode current collector
110. Opening
120. Wire Rod
200. Lithium thin film
210. Entrance
220. Non-entry part
300. Pressure Roller

Claims (16)

A negative electrode current collector in the form of a mesh made of a wire portion and an opening; And
Including; a lithium thin film consisting of a lead-in portion and a non-intrusion portion introduced into the opening of the negative electrode current collector,
The thickness of the lead-in portion of the lithium thin film is 20 to 60% of the total thickness of the lithium thin film,
A negative electrode for a lithium secondary battery in which an empty space exists among the opening spaces of the negative electrode current collector. delete The method of claim 1,
A negative electrode for a lithium secondary battery, characterized in that the thickness of the non-retractable portion of the lithium thin film is 40 to 80% of the total thickness of the lithium thin film. The method of claim 1,
The negative electrode for a lithium secondary battery, characterized in that the thickness of the lithium thin film is 10 to 800㎛. The method of claim 1,
A negative electrode for a lithium secondary battery, characterized in that the wire portion of the negative electrode current collector has a line width of 50 to 500 μm and a line spacing of 100 μm to 1 mm. The method of claim 1,
A negative electrode for a lithium secondary battery, characterized in that the shape of the opening of the negative electrode current collector is circular, oval, or polygonal. The method of claim 1,
The negative electrode for a lithium secondary battery, characterized in that the aperture ratio of the negative electrode current collector is 20 to 80%. The method of claim 1,
The negative electrode for a lithium secondary battery, characterized in that the thickness of the negative electrode current collector is 3 to 500㎛. The method of claim 1,
The negative electrode current collector is at least one selected from the group consisting of copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, alloys thereof, and combinations thereof. . A negative electrode current collector in the form of a mesh made of a wire portion and an opening;
A lithium thin film comprising a lead-in portion introduced into an opening portion of the negative electrode current collector and a non-intrusion portion not lead-in; And
A protective structure formed on the opposite surface of the lithium thin film facing the negative electrode current collector;
Including,
The thickness of the lead-in portion of the lithium thin film is 20 to 60% of the total thickness of the lithium thin film,
An empty space exists among the opening spaces of the negative electrode current collector,
The protective structure is composed of an organic polymer part and an inorganic material part,
The negative electrode for a lithium secondary battery, characterized in that the organic polymer portion is formed on the opposite surface of the lithium thin film in contact with the wire rod portion, and the inorganic material portion is formed on the opposite surface of the lithium thin film corresponding to the opening. The method of claim 10,
The organic polymer part is a negative electrode for a lithium secondary battery, characterized in that selected from polyvinyl alcohol, polyisobutylene, epoxy, polyethylene, polypropylene, polytetrafluoroethylene, and combinations thereof. The method of claim 10,
The inorganic material part is Li ₂ O, Li ₃ N, Al ₂ O ₃ , ZrO ₂ , SiO ₂ , CeO ₂ , Al ₂ TiO ₅ , oxy-sulfide glass, and a negative electrode for a lithium secondary battery, characterized in that selected from a combination thereof. I) preparing a mesh-shaped negative electrode current collector;
Ii) placing a lithium thin film on the negative electrode current collector; And
Iii) rolling the lithium thin film and the negative electrode current collector to lead the lithium thin film into the opening of the negative electrode current collector. The method of manufacturing the negative electrode for a lithium secondary battery of claim 1 comprising. The method of claim 13,
The method of manufacturing a negative electrode for a lithium secondary battery, characterized in that the rolling of step iii) applies a pressure of 10 kg/cm 2 to 100 ton/cm 2. The method of claim 13,
The method of manufacturing a negative electrode for a lithium secondary battery, characterized in that the rolling in step iii) is heated to a temperature of 100 to 200°C. A lithium secondary battery comprising the negative electrode of claim 1.

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