KR20220117430A - Anode electrode structure for secondary battery, an anode including the same and the manufacturing method - Google Patents

Abstract

The present invention provides a novel negative electrode structure for a secondary battery. Specifically, the negative electrode structure is designed to have an inner space that is a space between two conductive metal thin plates used as current collectors and during battery charging, a position of electrodeposition of the metal is induced to be limited inside the space. According to the structure of the present invention, dendrite growth is suppressed during electrodeposition of a negative electrode of the metal and volume change of the electrode is prevented during electrodeposition and desorption of the metal. By using the novel negative electrode structure having such functions, performance like energy density, rapid charging, stability, and lifespan of a secondary battery can be improved. The present invention relates to a novel concept of a negative electrode, the structure thereof, and a secondary battery using the same.

Description

Anode structure for secondary battery, negative electrode including same, secondary battery including same, and manufacturing method {Anode electrode structure for secondary battery, an anode including the same and the manufacturing method}

Secondary batteries are being actively applied not only as an energy storage medium for mobile devices, but also in medium and large-sized fields such as electric vehicles and power storage. The main components of a secondary battery can be divided into a positive electrode, a negative electrode, a separator, and an electrolyte, and in the case of a commercially available lithium secondary battery, an oxide positive electrode material, a graphite negative electrode material, a polymer separator, and a liquid electrolyte are commonly used. The positive and negative electrodes are fabricated by applying the respective active materials thereon using aluminum and copper foils as current collectors.

The present invention relates to a negative electrode of a secondary battery, a secondary battery including the same, and a method for manufacturing the same. More specifically, among the various negative electrode types of secondary batteries, for example, metal ions such as lithium or sodium do not use a separate active material such as graphite or silicon used in conventional secondary batteries, for example, a metal state The main content is to solve the problem of safety and durability of the metal anode by utilizing a metal anode in the form of electrodeposition and by guiding the electrodeposition position to the space between the current collectors having a special structure. From this, it relates to a technology that utilizes the high capacity and fast charging performance, which are the advantages of a metal negative electrode, while allowing it to be used safely for a long lifespan, and thus improving the performance of a secondary battery.

In lithium ion batteries, which are currently commercialized and widely used secondary batteries, lithium ions of a positive electrode move to a negative electrode through an electrolyte during charging, and electrons move to a negative electrode through an external circuit. Lithium ions are reduced in the negative electrode, and the reduced lithium is stored in the negative electrode active material, and energy is stored in the battery in this process. During discharging, lithium ions and electrons move from the negative electrode to the positive electrode again, and the energy stored during charging is used at this time. As a method of charging lithium in the negative electrode, the electrode-deposited form with lithium metal itself is the simplest and advantageous in terms of energy density. However, in this lithium metal anode, the volume change of the electrode by the volume corresponding to the difference between the lithium electrodeposition and the desorption state occurs repeatedly during the process of lithium electrodeposition and movement to the positive electrode, that is, in the charging/discharging process of a battery. This may cause distortion of the battery shape and durability problems. In addition, due to the non-uniform distribution of electric current, it is usually observed that lithium is gradually electrodeposited in the form of a dendritic form, and the growth of such dendritic acicular lithium continues to expand, which pierces the separator and causes a short circuit between the positive and negative electrodes, which is the heat generation of the battery. and safety-related problems such as ignition.

In order to cope with this problem, graphite anode materials have been introduced and widely commercialized (Korean Patent Application Laid-Open No. 10-2019-0073777). This is a method of using graphite as an active material to store lithium between graphene layers of graphite in atomic units. The graphite active material particles keep the overall volume of the anode constant, and lithium is not exposed to the outside and inside the crystal structure of graphite. By being stored in the dendritic growth problem can be suppressed. Due to these effects, graphite is used as a negative active material for commercial batteries. However, due to the volume and weight of graphite itself, the volume and weight of the negative electrode are increased, resulting in a loss in terms of energy storage density per volume and per weight of the battery, which causes the energy density of the lithium ion battery to increase. There will also be limitations. In addition, due to the limitation of the reaction rate at which lithium is intercalated and desorbed between the layers of the graphite crystal structure, the driving speed of the battery using the lithium as an anode active material, that is, the charging speed and output, is limited. Typically, the negative electrode active material is prepared in the form of a powder and is applied to the current collector in the form of a slurry together with the binder material. As the current collector for the negative electrode, a copper foil having a thickness of several micrometers is widely used. The current collector maintains the shape of the negative electrode and serves to support the negative electrode material, but by itself does not contribute to the capacity of the battery. have.

The current anode technology for commercial lithium-ion batteries can be summarized as follows: Graphite, which serves as a storage container for stably storing lithium and a frame for maintaining a constant volume of the anode, is used as the anode active material, and the anode active material The powder is applied and fixed to the copper foil current collector and used. These technical features stably store lithium when driving a lithium ion battery, while a loss in energy density occurs due to the volume and weight of the graphite anode active material, and the rapid charge/discharge performance is affected due to the limitation of the lithium insertion/desorption rate. There are also restrictions on Metal cathodes, which are electrodeposited and desorbed in their own state without using anode materials such as graphite, are ideal in terms of energy density or rapid charging. The problems of safety and cycle life must be solved.

Republic of Korea Patent Publication No. 10-2019-0073777 (June 27, 2019)

An object of one aspect of the present invention is that the electrodeposition and desorption positions of metal ions during the charging and discharging process of the secondary battery are specified as the space inside the negative electrode structure, as a result, the negative electrode volume is kept constant, and dendritic growth of the electrodeposited metal is prevented. It is to provide an anode structure for a secondary battery that can be suppressed.

Another object of the present invention is to provide a method of manufacturing the negative electrode structure for a secondary battery.

Another object of the present invention is to provide a secondary battery including the negative electrode structure for a secondary battery as a negative electrode.

In order to achieve the above object,

In one aspect of the present invention

Two sheets of conductive metal thin plate having an anti-electrodeposition layer coupled to each side, and disposed so that the opposite metal surface of the surface to which the anti-electrodeposition layer is coupled faces each other; and

In the anode structure for a secondary battery comprising a; space between the two thin metal plates,

It provides a negative electrode structure for a secondary battery, which is formed in the metal thin plate and the electrodeposition prevention layer is a hole through which the electrolyte and metal ions can move.

In addition, in another aspect of the present invention

Preparing two sheets of conductive metal thin plates;

forming a hole after applying an electrodeposition prevention layer to each side of the two thin conductive metal plates;

The method of manufacturing the negative electrode structure for a secondary battery of claim 1, including; disposing the metal surfaces opposite to the surface on which the electrodeposition prevention layer is applied of the two thin conductive metal plates to face each other and assembling to secure a space therebetween provides

In addition, in another aspect of the present invention

A secondary battery comprising the anode structure for a secondary battery provided in one aspect of the present invention as an anode is provided.

In the anode structure provided in one aspect of the present invention, in the case of a lithium secondary battery, since the electrodeposition position of lithium metal is limited to the space between two conductive metal thin plates, lithium dendritic growth penetrates the separator and causes a short circuit of the battery, By increasing the electrolyte interface through dendrite growth, there is an effect that can overcome the problems of the conventional metal anode, such as causing continuous decomposition of the electrolyte.

In addition, since the electrodeposition and desorption of lithium metal is performed in the space between the two thin metal plates constituting the anode structure, the volume of the entire electrode is kept constant, thereby providing excellent durability.

Accordingly, the negative electrode for a secondary battery according to the present invention has an excellent effect of improving lifespan and stability while having characteristics of high capacity and rapid charging.

1 shows a structural diagram of an anode structure according to an embodiment of the present invention.
2 is a view comparing the negative electrode structure according to an embodiment of the present invention to the conventional negative electrode technology, [1] a conventional metal negative electrode in a form in which metal ions are electrodeposited and desorbed on the current collector, [2] graphite negative electrode A cross section of a commercial negative electrode used as an active material, and a negative electrode utilizing the space between two thin metal plates (current collector) proposed in the present invention [3] is shown.
Figure 3 is a negative electrode structure according to an embodiment of the present invention manufactured in coin cell standards, [1] a thin metal plate with an electrodeposition prevention layer is combined and a hole through which the electrolyte can move, [2] an electrodeposition inducing layer is the surface An enlarged photograph of the electrodeposition-inducing layer composed of the mesh-type structure and zinc oxide nanorods formed in [3] shows the assembled anode structure.
4 is a photograph of a coin cell manufactured using the negative electrode structure according to an embodiment of the present invention, after 100 cycles of driving, disassembling the negative electrode structure in a state of being charged with lithium and observing each part with an electron microscope: [ 1] The surface where the electrodeposition prevention layer of the two thin metal plates are bonded, [2] the opposite metal surfaces of the two thin metal plates, and [3] the surface of the mesh-shaped structure were observed with an electron microscope, and the inset shows the This is an enlarged photo to check whether lithium is electrodeposited.
5 is a view comparing the cycle performance of the negative electrode structure according to Example 1 of the present invention with the conventional lithium metal negative electrode of Comparative Example 2, [1] a negative electrode using the negative electrode structure proposed in the present invention and [2] conventional lithium It shows the cycle driving charge/discharge graph (time-voltage graph) of the metal cathode.
6 is a view of the negative electrode structure after 100 cycles of driving the coin cell using the negative electrode structures according to Examples 1 and 3 in order to confirm the function according to the formation of the electrodeposition prevention layer and the electrodeposition inducing layer of the negative electrode structure of the present invention. As a photograph observed under a microscope in [1] Example 1 [2] Example 3 [3] Example 2 was observed under a microscope.

Hereinafter, the present invention will be described in detail.

On the other hand, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided in order to more completely explain the present invention to those of ordinary skill in the art.

Furthermore, "including" a certain element throughout the specification means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

The present invention proposes a new anode structure that can solve the problems of the metal anode for secondary batteries. Specifically, it is proposed as a core technology to design a structure so that two sheets of conductive metal thin plates, which are current collectors, have a space between them, and to guide the metal electrodeposition to the space between them. From the application of this technology, in the case of a metal, for example, a lithium secondary battery, since the electrodeposition position of lithium metal is limited to the space in between, lithium grows dendrites to break through the separator and cause a short circuit of the battery, or through dendritic growth with the electrolyte and By increasing the interface of By applying this technology to secondary batteries, while taking advantage of the metal anode technology capable of high-capacity and rapid operation, the electrode volume change, stability problems caused by dendritic growth, and cycle life problems are resolved, ultimately using a metal anode. It aims to realize a high-performance secondary battery.

The negative electrode structure proposed by the present invention, an electrodeposition prevention layer is formed on each surface of at least one of the two sheets of conductive metal thin plates, the two sheets of conductive metal thin plates disposed so that the metal faces of the two thin conductive metal plates face each other; and

As a negative electrode structure comprising a; space between the two thin metal plates,

In this case, there is provided an anode structure for a secondary battery in which the conductive metal thin plate on which the electrodeposition prevention layer is formed and the electrodeposition prevention layer have holes through which electrolytes and metal ions can move.

In the negative electrode structure, an electrodeposition prevention layer is formed on one surface of any one of the two thin conductive metal plates, and the conductive metal plate on which the electrodeposition prevention layer is formed and the electrodeposition prevention layer have holes through which electrolytes and metal ions can move.

In addition, in the negative electrode structure, an electrodeposition prevention layer is formed on each side of each of the two thin conductive metal plates, and the conductive metal plate on which the electrodeposition prevention layer is formed and the electrodeposition prevention layer have holes through which electrolytes and metal ions can move. .

Among the anode structures proposed by the present invention, an anode structure in which an electrodeposition prevention layer and holes are formed on both thin conductive metal plates is shown in FIG. 1 . In addition, a comparative drawing of the present invention and a conventional anode is summarized in FIG. 2 .

[1] of FIG. 2 shows a metal negative electrode on which a metal is electrodeposited on a current collector. In this type of negative electrode, for example, in the case of a lithium secondary battery, lithium is electrodeposited on a copper current collector when the battery is charged, and lithium is desorbed and moved to the positive electrode during discharge. Since it does not use a separate anode material other than a single current collector, it is most advantageous in terms of energy density, but a corresponding volume change occurs as the amount of lithium on the current collector changes during electrodeposition and desorption of lithium, and this volume change is repeated Silver may cause deformation of the electrode and cell shape and stability problems. In addition, as the electrodeposition and desorption are repeated, lithium usually exhibits needle-like and dendrite growth, which results in a continuous increase in the area of the interface between lithium and the electrolyte. As the area of the interface increases, electrolyte decomposition by side reactions at the interface continues, leading to depletion of the electrolyte. In addition, it is known that lithium grown as a dendrite eventually damages the separator and reaches the surface of the positive electrode, causing a short circuit inside the battery, which causes safety problems such as reduced battery cycle life and exothermic ignition.

[2] of FIG. 2 shows a negative electrode using currently commercialized graphite powder as a negative electrode active material, and graphite powder, which is a negative electrode active material, is coated on a copper current collector and used. When the battery is charged, lithium is stored in the atomic unit within the crystal structure of the graphite active material. Since lithium is contained in the crystal structure of graphite, dendritic growth is prevented, and since graphite maintains the volume of the electrode, the volume change of the negative electrode during charging and discharging of the battery is also relatively suppressed. However, due to the weight and volume of graphite itself, the accommodating density of lithium ions in the electrode is lowered, so the energy storage density of the battery is lowered. In addition, due to the limitation of the rate in the process of diffusion of lithium ions for insertion/desorption into the crystal structure of graphite, the driving rate of the battery is limited, which limits rapid charge/discharge.

[3] of FIG. 2 shows an anode structure proposed in an embodiment of the present invention. This is a form in which the structure secures an interspace, ie, an internal space, between two thin conductive metal plates (current collectors). By bonding the electrodeposition prevention layer to one side of each of the thin metal plates, the electrodeposition of metal ions is suppressed, on the other hand, the surface opposite to the surface to which the electrodeposition prevention layer is bonded, that is, the surface of the metal thin plate opposite to each other or the surface of the structure for securing the space between them. An electrodeposition-inducing layer was formed to induce the electrodeposition of metal ions. In addition, the thin metal plate and the electrodeposition prevention layer are machined with fine holes that can serve as a passage for the electrolyte. Through this electrode structure, the electrodeposition of the metal is limited to the space between the two thin metal plates when the battery is charged. For example, when applied to a lithium ion battery, the electrodeposition of lithium is limited to the space between the current collectors, that is, the internal space. Since it is a structure that secures and maintains an internal space, there is no change in the volume of the electrode during charging and discharging, and since the dendritic growth of lithium is limited in this space, a continuous increase in the lithium-electrolyte interface area and short circuit of the anode due to the continuation of dendritic growth problems such as this can be avoided. In short, the structure proposed in the present invention effectively responds to the problems of electrode volume change and dendrite growth, which are problems of the metal anode, and utilizes the high capacity and fast charging characteristics, which are the strengths of the metal anode. From this, an anode for a secondary battery having excellent performance in high energy density, high output, fast charging, stability, cycle life, and the like, and a secondary battery technology using the same are provided.

One aspect of the present invention is

Two sheets of conductive metal thin plate having an anti-electrodeposition layer coupled to each side, and disposed so that the opposite metal surface of the surface to which the anti-electrodeposition layer is coupled faces each other; and

In the anode structure for a secondary battery comprising a; space between the two thin metal plates,

It provides a negative electrode structure for a secondary battery, which is formed in the metal thin plate and the electrodeposition prevention layer is a hole through which the electrolyte and metal ions can move.

The two sheets of conductive metal thin plate may be a current collector that maintains the shape of the negative electrode and supports the negative electrode material.

At this time, the metal surface disposed to face each other of the two sheets of conductive metal thin plates is the inner surface of the negative electrode structure, and the surface to which the electrodeposition prevention layer is coupled is the opposite electrode direction surface of the negative electrode structure, and between the two sheets of thin metal plates The space of can be referred to as the internal space of the negative electrode structure.

In the charging and discharging process of the secondary battery, it is characterized in that the metal ions are electrodeposited and desorbed in a metallic state on the metal surface disposed to face each other in the space between the thin metal plates of the negative electrode structure.

At this time, since the electrodeposition prevention layer is formed on the opposite electrode direction surface opposite to the interspace, electrodeposition and desorption of the metal ions on the opposite electrode direction surface of the negative electrode structure is prevented,

Holes are formed in the thin metal plate and the electrodeposition prevention layer through which electrolytes and metal ions can move, so that the electrolyte and metal ions can move into the space between the two thin metal plates of the negative electrode structure, that is, the internal space.

The structure is manufactured in a form in which an insulation prevention layer and a hole are formed on both thin conductive metal plates, can be used in both directions, and can receive metal ions from anodes in both directions as in a commercial secondary battery.

In the case of a secondary battery in which the metal to be electrodeposited is included in the negative electrode in principle of operation, such as a metal-sulfur metal-air battery, or when compensation for irreversible capacity, that is, metal ions during battery operation, is required, the structure can contain the metal to be electrodeposited. and, for example, in the case of a lithium ion battery, a small amount of lithium metal may be contained.

The average diameter of the pores can be applied without limitation as long as it has a size that allows electrolytes and metal ions to pass easily, but in one embodiment may be 1 μm to 1000 μm, 1 μm to 500 μm, and 1 μm to 300 μm, 1 μm to 250 μm, 1 μm to 220 μm, 10 μm to 1000 μm, 10 μm to 500 μm, 10 μm to 250 μm, , may be 10 μm to 220 μm, may be 50 μm to 300 μm, may be 80 μm to 250 μm, may be 90 μm to 220 μm, and preferably may be 200 μm.

In addition, the average thickness of the two thin metal plates may be each independently 1 μm to 15 μm, 1 μm to 14 μm, 1 μm to 13 μm, 1 μm to 12 μm, 1 μm to 11 μm, 1 μm to 10 μm, 1 μm to 9 μm, 2 μm to 15 μm, 3 μm to 15 μm, 4 μm to 15 μm may be 2 μm to 14 μm, may be 2 μm to 12 μm, may be 2 μm to 11 μm, may be 2 μm to 10 μm, may be 3 μm to 10 μm, 4 It may be from ㎛ to 10 ㎛, 4 ㎛ to 9 ㎛, most preferably 6 ㎛.

The average thickness of the electrodeposition prevention layer may be 0.1 μm to 100 μm, may be 0.1 μm to 50 μm, may be 0.1 μm to 20 μm, may be 0.1 μm to 15 μm, and may be 1 to 100 μm, and , 1 μm to 50 μm, 1 μm to 20 μm, 1 μm to 15 μm, 3 μm to 100 μm, 3 μm to 50 μm, 3 μm to 20 It can be from 3 μm to 15 μm, it can be from 3 μm to 12 μm, it can be from 5 μm to 20 μm, it can be from 5 μm to 15 μm, it can be from 5 μm to 12 μm, It may be 5 μm to 11 μm, and most preferably 10 μm.

In addition, in the interspace, in order to maintain a constant volume of the negative electrode structure during charging and discharging of the battery and stably forming the interspace, a structure may be provided between the two sheets of conductive metal thin plates.

In this case, the structure can be applied without limitation as long as it has a three-dimensional shape and a shape capable of stably forming an interspace, and may have a particulate, fibrous or mesh shape.

In one embodiment, a mesh made of a metal, ceramic, or plastic material may be used, or beads made of a metal, ceramic, or plastic material may be dispersed and used. In addition, in order to reduce the weight, a core-shell structure of various materials may be used. For example, a metal or ceramic may be coated on the surface of a mesh made of plastic or organic fiber.

If a mesh shape is adopted as the structure, the average thickness of the mesh forming the gap between the two thin metal plates can be applied without limitation as long as it can form a space between the two thin conductive metal plates, but in one embodiment 10 μm to 1000 μm, 30 μm to 1000 μm, 50 μm to 1000 μm, 100 μm to 1000 μm, 150 μm to 1000 μm, 170 μm to 1000 It can be from 190 μm to 1000 μm, from 10 μm to 1000 μm, from 10 μm to 750 μm, from 10 μm to 500 μm, from 10 μm to 250 μm, 50 μm to 500 μm, 100 μm to 500 μm, 150 μm to 500 μm, 50 μm to 300 μm, 100 μm to 300 μm, 150 μm to 300 μm may be, may be 170 µm to 250 µm, may be 170 µm to 220 µm, may be 190 µm to 220 µm, and most preferably may be 200 µm.

An electrodeposition-inducing layer for activating electrodeposition of metal ions may be formed on at least a portion of the opposite metal surfaces of the two thin conductive metal plates or on the surface of the structure. For example, in the case of a lithium ion battery, zinc oxide, silicon, sulfur, etc., which are known to have lithiophilic properties, may be used to activate the electrodeposition of lithium ions, and other materials that can help the electrodeposition of lithium may be used. It is also possible to use

In addition, in order to maximize the electrodeposition-inducing function of the electrodeposition-inducing layer, the surface area can be maximized by manufacturing in the form of nano- or micrometer-scale projections.

On the other hand, it may be deformed in a form in which the electrodeposition target metal is composited in the space between the two thin conductive metal plates. For example, in the case of a lithium ion battery, a lithium foil may be inserted into the space or a structure inserted to secure a space may be implemented by coating or compounding the structure with lithium metal.

In the case of applying the metal-sulfur or metal-air battery to a battery in which the metal to be electrodeposited must be manufactured in a form that is included in the negative electrode due to the driving principle of the secondary battery, the metal to be electrodeposited in the negative electrode can be implemented in a complex form through this method. In the case of compensating for the irreversible loss of metal ions from the cathode, it can be supplemented by a method.

The negative electrode structure can be applied to a secondary battery mediated by metal ions, for example, a lithium ion battery, a sodium ion battery, an aluminum ion battery, a magnesium ion battery, a calcium ion battery, a potassium ion battery, and the like.

The conductive metal thin plate is a current collector, and in the case of a commercial lithium ion battery, copper foil is preferable, but other conductive metals such as aluminum, iron, stainless steel, nickel, silver, gold, magnesium, titanium, and metals thereof It is also possible to use an alloy based on the.

The electrodeposition prevention layer may have insulating properties to prevent reduction and electrodeposition of metal ions by blocking the movement of electrons so as to inhibit metal ions from being reduced and electrodeposited by electrons moving from the conductive metal thin plate.

If the electrodeposition prevention layer is an insulating material, a metal, a ceramic, a polymer, etc. may be used, and in the case of a lithium ion battery, it is more preferable to have a lithium (Lithophobic) surface characteristic. In addition, in order to reduce the weight of the electrode, a polymer material, PVA or PVC in one embodiment, may be used, and it is also possible to use a ceramic-based solid electrolyte insulating layer.

In the negative electrode structure for a secondary battery provided in one aspect of the present invention, in the case of a lithium secondary battery, since the electrodeposition position of lithium metal is limited to the space between two conductive metal thin plates, lithium dendritic growth penetrates the separator and causes a short circuit of the battery Alternatively, there is an effect that can overcome the problems of the conventional metal anode, such as causing continuous decomposition of the electrolyte by increasing the electrolyte interface through dendrite growth.

In addition, since the electrodeposition and desorption of lithium metal is performed in the space between the two thin metal plates constituting the anode structure, the volume of the entire electrode is kept constant, thereby providing excellent durability.

Accordingly, the negative electrode for a secondary battery according to the present invention has an excellent effect of improving lifespan and stability while having characteristics of high capacity and rapid charging.

In another aspect of the present invention,

Preparing two sheets of conductive metal thin plates;

forming a hole after applying an electrodeposition prevention layer to each side of the two thin conductive metal plates;

A negative electrode for a secondary battery provided in one aspect of the present invention, including; assembling so that the metal surfaces opposite to the surface on which the electrodeposition prevention layer is applied of the two thin conductive metal plates are disposed to face each other and a space therebetween is secured A method for manufacturing a structure is provided.

At this time, in the process of assembling the two thin conductive metal plates, the electrodeposition prevention layer should be formed on the opposite electrode direction surface opposite to the space between the two thin metal plates, whereby metal ions are electrodeposited and desorbed on the opposite electrode direction surface of the negative electrode structure can be prevented.

In addition, prior to forming the hole, it may further include the step of drying the electrodeposition prevention layer applied to each side of the two thin conductive metal plates. The electrodeposition prevention layer may have an average thickness after drying of 0.1 μm to 100 μm, 0.1 μm to 50 μm, 0.1 μm to 20 μm, 0.1 μm to 15 μm, and the same as described above. 1 to 100 μm, 1 μm to 50 μm, 1 μm to 20 μm, 1 μm to 15 μm, 3 μm to 100 μm, 3 μm to 50 μm can be 3 μm to 20 μm, 3 μm to 15 μm, 3 μm to 12 μm, 5 μm to 20 μm, 5 μm to 15 μm, 5 μm It may be 12 μm to 12 μm, 5 μm to 11 μm, and most preferably 10 μm.

The securing of a space between the two thin conductive metal plates may include providing a structure between the two thin conductive metal plates.

The structure can be applied without limitation as long as it has a shape capable of stably forming an interspace, and may have a particulate, fibrous or mesh form.

When the mesh-type structure is adopted, the method may further include a step of aligning the positions so that each empty space of the mesh matches the positions of the holes formed in the conductive metal thin plate and the electrodeposition prevention layer.

In another aspect of the present invention,

A secondary battery comprising the anode structure for a secondary battery provided in one aspect of the present invention as an anode is provided.

In the anode structure provided in one aspect of the present invention, in the case of a lithium secondary battery, since the electrodeposition position of lithium metal is limited to the space between two conductive metal thin plates, lithium dendritic growth penetrates the separator and causes a short circuit of the battery, By increasing the electrolyte interface through dendrite growth, there is an effect that can overcome the problems of the conventional metal anode, such as causing continuous decomposition of the electrolyte.

In addition, since the electrodeposition and desorption of lithium metal is performed in the space between the two thin metal plates constituting the anode structure, the volume of the entire electrode is kept constant, thereby providing excellent durability.

Accordingly, the negative electrode for a secondary battery according to the present invention has an excellent effect of improving lifespan and stability while having characteristics of high capacity and rapid charging.

Hereinafter, the present invention will be described in detail through Examples and Experimental Examples.

However, the Examples and Experimental Examples described below are merely illustrative of the present invention in detail in one aspect, and the present invention is not limited thereto.

<Example 1> Preparation of the negative electrode structure of the present invention, and a battery comprising the same

Two thin copper plates were prepared, and an aqueous solution of polyvinyl alcohol (PVA), an electrodeposition preventing material, was applied to one side of both thin metal plates and dried, and then fine holes having a diameter of about 200 μm were processed.

A nickel-plated nylon mesh was prepared as a structure for securing space between thin copper plates. The surface of the mesh was coated with zinc oxide, an electrodeposition inducing material. To increase the surface area, the zinc oxide layer was configured in the form of projections of nanorod particles. A small amount of lithium metal and the mesh were combined by overlapping and pressing a lithium foil having a thickness of 70 μm on the mesh.

The lithium-mesh composite is inserted between the metal surfaces on which the PVA layer is not formed of the two thin copper plates, and finally, as shown in FIG. A structure in which a composite of a mesh and lithium metal formed on the surface of an electrodeposition inducing layer was inserted was fabricated.

The thickness of the copper foil used to fabricate the structure was 6 μm, and the coating amount was adjusted so that the thickness after drying of the PVA coating layer was 10 μm. The nickel mesh used was #30 standard, and the thickness of the mesh was about 200 μm, and the thickness of the lithium foil was 70 μm.

Two sheets of copper thin plate, lithium foil and nickel mesh were all punched out in a 14 mm diameter circle in accordance with the coin cell manufacturing standard, and thus, a structure combining them was also manufactured in Φ14 mm. A 2032-type coin battery was manufactured using this structure as an electrode and a 0.5 mm thick lithium chip as a counter electrode.

<Example 2> Preparation of the negative electrode structure of the present invention and a battery comprising the same

In Example 1, an anode structure was manufactured in the same manner as in Example 1, except that zinc oxide, an electrodeposition inducing material, was not coated on the surface of the nickel-plated nylon mesh as a structure.

<Example 3> Preparation of the negative electrode structure of the present invention and a battery comprising the same

In Example 1, an anode structure was manufactured in the same manner as in Example 1, except that PVA, an electrodeposition preventing material, was not coated on the surfaces of the two copper thin plates as the current collector.

<Comparative Example 1> Preparation of a battery including a graphite negative electrode material

A commercial graphite anode was evaluated as a comparative object. A slurry composed of a commercial natural graphite negative electrode material, a binder, and a conductive material in a weight ratio of 8:1:1 was applied to a 6 μm-thick copper thin plate current collector and dried. This was rolled and punched to a size of Φ14 mm, vacuum dried at 80° C. for 24 hours, and then used as an electrode to fabricate a 2032-type coin cell. The application amount of the negative electrode material per unit area of the current collector was controlled in the range of 20±5 mg/cm2. A coin cell was manufactured under the same conditions as in Example 1, except that graphite was used as an anode active material.

<Comparative Example 2> Preparation of a battery including a negative electrode using a single metal current collector

Instead of a negative electrode structure, only a single copper thin plate current collector was used, and an electrode of a method in which lithium was exposed on the copper thin plate surface was used as an electrode. Other than that, a coin cell was manufactured under the same conditions as in Example 1.

<Experimental Example 1> Confirmation of the electrodeposition position of lithium

Through the embodiment of the present invention, a new negative electrode structure capable of suppressing the expansion of dendritic growth during lithium electrodeposition and preventing the volume change of the electrode was proposed. Through this electrode structure, lithium is induced to be electrodeposited in the inner space behind the electrode rather than on the front surface, and it is intended to suppress the problem of dendritic growth protruding in the anode direction and the continuous electrolyte decomposition reaction caused by dendrite growth. did. In other words, by safely using a lithium metal anode for a long lifespan, it was intended to realize a secondary battery negative electrode with high capacity, high output, long lifespan, and safety compared to the existing commercial graphite negative electrode, and whether the intention of this invention was realized through Examples and Comparative Examples It was checked through sample preparation and evaluation.

More specifically, the coin cells prepared in Example 1 and Comparative Example 1 were subjected to 1.5 mA (1.0 mA/cm ² in conversion per unit area) and 15 mA (10 mA/ in conversion per area) in a voltage range of -0.05 to 0.50 V. cm ² ) The capacity was measured by charging and discharging with an electric current. In the case of Example 1, since it is intended in the present invention that electrodeposition occurs only inside the structure, the amount of lithium electrodeposition that the structure can accommodate in a range in which lithium is not electrodeposited on the outer surface was evaluated, and the capacity was converted therefrom. Thereafter, charging and discharging were repeated in the ±0.50 V voltage limit range under the condition of charging and discharging for 30 minutes at a current of 15 mA (current of 10 mA/cm ² in terms of unit area). This corresponds to repeatedly driving a capacity of 7.5 mAh (5.0 mAh/cm ² in terms of unit area) at a rate of 2 C. A total of 1000 cycle driving tests were performed under these conditions.

In order to confirm whether the function of inhibiting lithium electrodeposition in the structure internal space and lithium electrodeposition on the outer surface of the structure, which is the core concept of the present invention, was implemented, the coin cell of Example 1 was subjected to 100 charge/discharge cycles after lithium electrodeposition was performed. disassembled in condition. The electrode sample extracted from this was disassembled, and the electrodeposition state of lithium was identified by observing the outer surface of the thin copper plate on which the electrodeposition prevention layer was formed, the opposite inner surface, and the surface of the mesh as a structure. From this, it was determined whether the electrodeposition of lithium was induced and limited to the inside of the negative electrode structure as intended in the present invention. The results are shown in FIG. 4 .

As a result of the observation, as shown in FIG. 4, lithium electrodeposition did not appear on the outer surface of the structure, that is, the PVA-coated positive electrode direction ([1] in FIG. 4). On the other hand, it can be seen that a large amount of lithium is electrodeposited on the surface of the opposite side of the thin copper plates facing each other and on the surface of the mesh inserted to secure space ([2], [3] in FIG. 4). From this, as intended in the present invention, the electrodeposition of lithium is limited only to the inside of the structure, and the growth of lithium is not made to the outside of the anode structure, so that the dendritic growth is extended to the outside as the electrodeposition lithium is trapped in the inner space. It was confirmed that the effect to suppress the

<Experimental Example 2> Performance evaluation as a lithium ion battery negative electrode (1)

For Example 1 and Comparative Example 1, the performance evaluation results as a lithium ion battery negative electrode are summarized in the table below.

In general, the capacity of the negative electrode is converted into the capacity per weight of the negative electrode active material, but since the negative electrode structure proposed in the present invention includes a current collector, in this experimental example, the capacity per weight of the electrode is calculated based on the total weight of the negative electrode. converted. That is, the capacity per weight was calculated by dividing the charge storage capacity by the weight of the negative electrode structure (current collector + mesh weight) in Example 1 and the capacity in Comparative Example 1 by the weight of the total negative electrode (current collector + graphite active material weight). . In the case of cycle life, a total of 1000 cycles were evaluated, and in the case of still operating normally in the last cycle, more than 1000 times (>1000) were indicated. The number of driving was expressed as the lifespan. The performance evaluation results for Example 1 and Comparative Example 1 from the above criteria are shown in Table 1 below.

Capacity (mAh/g*) Cycle life (times)
15 mA (2 C) drive 1.5 mA drive 15 mA drive Example 1
: Structure of the present invention #One 735 701 >1000 #2 750 715 >1000 #3 721 698 >1000 #4 788 751 >1000 #5 767 735 >1000 Comparative Example 1
: Commercial graphite anode #One 244 191 520 #2 252 208 424 #3 262 207 605 #4 239 186 >1000 #5 237 179 788

*Calculation of capacity per weight is based on the total weight of the negative electrode including the current collector.

From the comparison of the evaluation results of Example 1 and Comparative Example 1 of each of the five samples, the negative electrode proposed in the present invention is about 3 times that of the conventional commercial graphite negative electrode in low current driving of 1.5 mA, and in rapid driving of 15 mA. It was possible to realize high energy density by providing capacity per weight of about 3.7 times or more. In particular, it was evaluated that the negative electrode of the present invention exhibits more superior performance under rapid charge/discharge conditions because the loss of capacity when the driving rate is increased is about 5%, which is much smaller than about 22% of the comparative example. As a result of the cycle test with a current of 15 mA, all five samples of Example 1 were capable of driving up to 1000 cycles, but in the case of Comparative Example, normal operation was stopped before all but one sample. This indicates that the negative electrode of the present invention has excellent cycle life compared to the conventional graphite negative electrode.

By combining the evaluation results of Example 1 and Comparative Example 1, which is a commercial graphite negative electrode, the proposal of the present invention provides a higher energy density, excellent rapid charge/discharge performance, improved durability and cycle life compared to the conventional commercial negative electrode. It was confirmed that a secondary battery with improved performance could be realized through the application of this technology.

<Experimental Example 3> Performance evaluation as a lithium ion battery negative electrode (2)

For Example 1 and Comparative Example 2, the cycle performance of the battery was evaluated, and the results are shown in FIG. 5 .

Prepare the samples of Example 1 and Comparative Example 2, charge and discharge for 30 minutes with a current of 15 mA (current of 10 mA / cm ² converted per unit area) ± 0.50 V voltage limit range under the condition of discharging for 30 minutes repeated. This corresponds to repeatedly driving a capacity of 7.5 mAh (5.0 mAh/cm ² in terms of unit area) at a rate of 2 C.

Comparative Example 2 is a general form of a lithium metal negative electrode using electrodeposition and desorption of lithium metal, and is driven in such a way that electrodeposition and desorption of lithium occurs on the surface of the current collector in the counter electrode direction without using a special structure.

On the other hand, the negative electrode structure proposed in the present invention of Example 1 forms a space between two thin metal plates used as a current collector, and has a feature in which electrodeposition and desorption of lithium occurs in the space. Therefore, in the case of a general lithium metal anode, the dendrite growth of electrodeposited lithium proceeds in the opposite direction to cause a short circuit, whereas in the structure proposed in the present invention, the effect of preventing short circuit is expected because the dendrite properties of lithium are confined in the inner space of the anode structure. can

As shown in FIG. 5, as a result of the cycle evaluation of Example 1 and Comparative Example 2, in the case of Example 1, a stable charge/discharge operation was continued, while in Comparative Example 2, an internal short circuit occurred during operation to prevent abnormality. showed From this, it was confirmed that the negative electrode structure proposed in the present invention has an excellent effect of improving the driving durability of the battery.

<Experimental Example 4> Evaluation of anode volume change

For Example 1 and Comparative Example 2, the volume change of the cathode according to the electrodeposition and desorption of metal ions was evaluated as follows.

Each of the five coin cells for Examples and Comparative Examples were disassembled in charging and discharging states of 15 mAh capacity, that is, in electrodeposition and desorption states of lithium to measure the thickness of the electrodes, and the results are presented in Table 2.

Thickness (μm) Electrode thickness change rate (%)
(Electrodeposition → Desorption) electrodeposition Desorption Example 1
: Structure of the present invention #One 255 245 3.9 #2 234 230 1.7 #3 241 235 2.5 #4 228 220 3.5 #5 247 235 4.9 Comparative Example 2
: Lithium metal anode in general form #One 152 7 95.4 #2 120 8 93.3 #3 112 8 92.9 #4 170 10 94.1 #5 95 8 91.6

According to Table 2, in the case of Comparative Example 2, an average of 93.5% of the electrode thickness during lithium electrodeposition and desorption after electrodeposition decreased, whereas in Example 1, only 3.3% was reduced, indicating that the thickness change of the electrode was very small. can be checked Therefore, it was found that the negative electrode structure proposed in the present invention induces electrodeposition and desorption of metal ions inside the negative electrode structure, thereby suppressing a change in the negative electrode volume.

<Experimental Example 5> Evaluation of effectiveness of electrodeposition prevention layer and electrodeposition inducing layer

For Examples 1 to 3, the effects of the formation of an electrodeposition prevention layer and an electrodeposition inducing layer were evaluated, and the results are shown in FIG. 6 .

Charging and discharging for 30 minutes with a current of 15 mA (current of 10 mA/cm ² converted per unit area) was repeated within the ±0.50 V voltage limit range under the condition of 30 minutes of charging and discharging. After driving a total of 100 cycles under these conditions, the outer surface of the current collector of the negative electrode structure was observed.

6 shows a photograph observed with respect to the outer surface of the current collector of the negative electrode structure after 100 cycles of driving for each case. In the case of Example 1 shown in [1] of FIG. 6, there was no electrodeposition of lithium on the outer surface of the current collector on which the electrodeposition prevention layer was formed as intended in the present invention, whereas the electrodeposition prevention layer of [2] of FIG. 6 was not formed. In the case of Example 3, it was observed that a large amount of lithium was electrodeposited on the outer surface of the current collector. From this, it can be confirmed that the electrodeposition prevention layer formed on the outer surface of the structure plays a major role in controlling the electrodeposition position of lithium.

In the case of Example 2 of [3] of FIG. 6, partially electrodeposited lithium was observed on the outer surface of the copper thin plate as the current collector. From this, it can be confirmed that the electrodeposition-inducing layer formed inside the structure is also effective in controlling the electrodeposition position of lithium.

Therefore, in the negative electrode structure proposed in the present invention, the formation of an electrodeposition-preserving layer on the outer surface of two thin metal plates as a current collector and an electrodeposition-inducing layer in the internal space of the structure has a major effect in controlling the electrodeposition position of lithium into the structure. And it was confirmed that the effect can be maximized when both cases are applied together.

Claims (13)

Two sheets of conductive metal thin plate having an anti-electrodeposition layer coupled to each side, and disposed so that the opposite metal surface of the surface to which the anti-electrodeposition layer is coupled faces each other; and
In the anode structure for a secondary battery comprising a; space between the two thin metal plates,
The metal thin plate and the electrodeposition prevention layer, the electrolyte and the hole through which metal ions can move is formed, the negative electrode structure for a secondary battery.
According to claim 1,
The average thickness of the two thin metal plates is each independently 1 μm to 15 μm, a negative electrode structure for a secondary battery.
According to claim 1,
The average thickness of the electrodeposition prevention layer is 0.1 μm to 100 μm, the negative electrode structure for a secondary battery.
According to claim 1,
The average diameter of the hole will be 1 ㎛ to 1000 ㎛, a negative electrode structure for a secondary battery.
According to claim 1,
In order to constantly secure the space between the two sheets of conductive metal thin plates, a structure is provided between the two sheets of thin conductive metal plate, a negative electrode structure for a secondary battery.
According to claim 1,
The gap between the two sheets of conductive metal thin plates is 10 μm to 1000 μm, a negative electrode structure for a secondary battery.
6. The method of claim 5,
The structure has a particulate, fibrous or mesh shape, a secondary battery negative electrode structure.
6. The method of claim 5,
An electrodeposition inducing layer is formed on the surface of the structure, the negative electrode structure for a secondary battery.
According to claim 1,
An electrodeposition inducing layer is formed on at least some of the metal surfaces facing each other of the two sheets of conductive metal thin plate, the negative electrode structure for a secondary battery.
Preparing two sheets of conductive metal thin plates;
forming a hole after applying an electrodeposition prevention layer to each side of the two thin conductive metal plates;
The method for manufacturing the negative electrode structure for a secondary battery of claim 1, comprising: disposing the opposite metal surfaces of the two thin conductive metal plates to face each other and securing a space therebetween.
11. The method of claim 10,
The method of claim 1, wherein the step of securing a space between the two sheets of conductive metal thin plates includes providing a structure between the two sheets of conductive metal thin plates.
11. The method of claim 10,
Prior to forming the hole, the method of claim 1, further comprising the step of drying the electrodeposition prevention layer applied to each side of the two thin conductive metal plates.
A secondary battery comprising the anode structure for a secondary battery of claim 1 as an anode.

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