KR20210044119A - Sencondary battery, and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a secondary battery comprising: a negative electrode; a positive electrode; and an electrolyte interposed between the positive electrode and the negative electrode, wherein the negative electrode includes a metal layer containing a metal capable of reversible absorption and release of alkali metal or alkaline earth metal ions by alloying and dealloying with an alkali metal or alkaline earth metal, and the electrolyte includes an ether-based solvent and metal salt.

Description

Secondary battery, and a method of manufacturing the same TECHNICAL FIELD [Sencondary Battery, AND MANUFACTURING METHOD THEREOF]

It relates to a secondary battery, and a method of manufacturing the same. Specifically, the reversible absorption and release of alkali metal or alkaline earth metal ions by alloying and dealloying with an alkali metal or alkaline earth metal relates to a negative electrode including a metal layer including a metal, and a secondary battery including an ether-based electrolyte will be.

As various portable electronic devices and electric vehicles are researched and developed, the need for energy storage technology is further increasing, and accordingly, lithium secondary batteries having high energy density and voltage are widely used.

However, due to the high price and limited reserves of lithium, active research on sodium ion batteries using sodium having a relatively low price and high energy density as a next-generation battery is being conducted.

Even if a graphite negative electrode used in a lithium ion battery is applied to a sodium ion battery, it is not possible to achieve a high capacity as in the conventional lithium ion battery, and there is a problem in that a battery having high energy cannot be developed.

Accordingly, there is a need to develop a new anode capable of achieving high capacity even when applied to a sodium ion battery or the like.

It provides a secondary battery including a negative electrode with improved charge/discharge cycle characteristics and electrode capacity, and an ether-based electrolyte.

A secondary battery according to an embodiment of the present invention includes a negative electrode, a positive electrode, and an electrolyte interposed between the positive electrode and the negative electrode.

The negative electrode may include a metal layer including a metal capable of reversibly absorbing and releasing alkali metal or alkaline earth metal ions by alloying and dealloying with an alkali metal or alkaline earth metal.

The electrolyte may include an ether solvent and a metal salt.

The metal layer may include a metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi.

The metal layer may contain 97 mass% or more of the metal based on 100 mass% of the total metal layer. Specifically, it may be 97 to 100% by mass, 98 to 100% by mass, 99 to 100% by mass, or 99.8 to 100% by mass. As the balance, other metals or impurities may be further included.

The metal layer may have a thickness of 1 μm to 2 mm. Specifically, it may be 10㎛ to 2mm, 20㎛ to 2mm, 30㎛ to 2mm, 50㎛ to 2mm, 100㎛ to 2mm, 150㎛ to 2mm, or 200㎛ to 2mm.

The metal layer may be in the form of a metal foil.

The ether solvent is dimethoxyethane (DME), 1,3-dioxolane (1,3-dioxolane), tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (Diethylene glycol). dimethyl ether, DEGDME), triethylene glycol dimethyl ether (TEGDME), polyethylene glycol dimethyl ether (PEGDME), polyethylene oxide (PEO), and dioxolane (DOL) It may include those selected from the group containing.

The anode is CuS. It may be selected from the group including Cu ₂ S, NiS, Ni ₃ S ₂ , NiS ₂ , TiS ₂ , and MoS _3.

A separator may be further included between the anode and the cathode.

The separation membrane may be a nanoporous separation membrane having pores of 10 nm to 100 nm. Specifically, it may be 20nm to 100nm, 50nm to 100nm, or 80nm to 100nm.

The separation membrane may be a microporous separation membrane having pores of 1 μm to 50 μm. Specifically, it may be 3 μm to 50 μm, 5 μm to 50 μm, 10 μm to 50 μm, or 15 μm to 50 μm.

The thickness of the nanopore separation membrane may be 5 μm to 1 mm. Specifically, it may be 10 μm to 1 mm, 15 μm to 1 mm, 20 μm to 1 mm, and 25 μm to 1 mm.

The micropore separation membrane may have a pore size of 1 μm to 50 μm. Specifically, it may be 3 μm to 50 μm, 5 μm to 50 μm, 8 μm to 50 μm, or 10 μm to 50 μm.

The microporous separation membrane may have a thickness of 0.2mm to 2mm. Specifically, it may be 0.5mm to 2mm, 0.8mm to 2mm, or 1mm to 2mm.

The separation membrane may be a multiple separation membrane including a nanoporous separation membrane and a microporous separation membrane.

In the secondary battery according to another embodiment of the present invention, the metal layer may include two or more metal layers including a metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi. .

Each of the two or more metal layers may include metals different from each other.

A method of manufacturing a secondary battery according to an embodiment of the present invention includes the steps of manufacturing a negative electrode having a metal layer formed thereon by rolling a metal; And manufacturing a battery including the negative electrode, the electrolyte, and the positive electrode.

The electrolyte may include an ether solvent and a metal salt.

The metal layer may include a metal capable of reversibly absorbing and releasing alkali metal or alkaline earth metal ions by alloying with an alkali metal or alkaline earth metal.

After the manufacturing of the negative electrode, a negative electrode including the metal layer and a half-cell including the metal electrode may be formed, completely discharged, and then partially charged.

In the method of manufacturing a secondary battery according to another embodiment of the present invention, in the manufacturing of the electrode, a first metal layer is formed by rolling a first metal, and a second metal layer is rolled on the first metal layer to form a second metal layer. It may be to form.

The first metal and the second metal may include a metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi.

The first metal and the second metal may be metals different from each other.

Cathode capacity can be improved by applying a cathode containing a metal capable of reversibly absorbing and releasing alkali metal or alkaline earth metal ions by alloying and dealloying with an alkali metal or alkaline earth metal.

By applying an electrolyte containing an ether-based solvent, it is possible to improve the charge/discharge cycle characteristics of the negative electrode.

As a result, it is possible to provide a secondary battery with improved capacity and cycle characteristics.

1 is a schematic diagram of a negative electrode included in a battery according to an embodiment of the present invention.
2 is an actual photograph of the negative electrode of Example 1-1.
3 is a diagram showing a half-cell structure for electrode evaluation.
4 is a graph showing the cycle characteristics of the negative electrode of Example 1-1 at a current density of 0.1 C (84.7 mA/g).
5 is a graph showing charge/discharge curves of the 50th cycle of the negative electrode of Example 1-1 at a current density of 0.1 C.
6 shows charge/discharge curves of the negative electrode of Example 1-1 at a current density of 0.01 C.
7 is a graph showing charge/discharge curves according to the current density of Example 1-1.
8 is a graph showing the charge/discharge curves of Example 1-2 of the present invention at a current density of 0.01 C.
9 is a graph showing the cycle characteristics of the negative electrode of Example 1-1 for 100 cycles at current densities of 0.5 C and 1 C.
10 is a SEM photograph of the surface of the Sn metal layer of the negative electrode in Example 1-1.
11 is an EDS mapping photograph of the Sn metal layer of the cathode in Example 1-1.
12 is an EDS spectrum of the Sn metal layer of the negative electrode in Example 1-1.
13 is an XRD result of the cathode Sn metal layer in Example 1-1.
14 is a photograph of a state in which the Sn metal layer of the negative electrode of Example 1-1 completely reacted with Na.
15 is a SEM photograph of a state in which the Sn metal layer of the negative electrode of Example 1-1 completely reacted with Na.
16 is a real photograph of the metal layer after 20 cycles of the negative electrode in Example 1-1.
17 is a diagram showing the structure of a full-cell using the cathode and the NVP[Na ₃ V ₂ (PO ₄ ) _{3] anode of Example 1-1.}
18 is a diagram showing the structure of a Na/NVP half-cell.
19 is a graph of charge/discharge curves of Na/NVP half-cells at a current density of 1A/g.
20 is a graph showing rate characteristics and cycle characteristics of a full-cell composed of a cathode and an NVP anode in Example 1-1.
21 is a graph showing charge/discharge curves of a full-cell consisting of a cathode and an NVP anode in Example 1-1 at a current density of 1 A/g.
22 is an actual photograph of the cathode of Example 2.
23 is an XRD result of the negative electrode of Example 2.
24 is a charge/discharge curve of the negative electrode of Example 2 at a current density of 0.01 C (4.85 mA/g).
25 is a photograph of the negative electrode of Example 3.
26 is a charge/discharge curve of the negative electrode of Example 3 at a current density of 0.1 C (3.85 mA/g).
27 is a charge/discharge curve of the negative electrode of Example 3 at 0.01 C.
28 is a schematic diagram showing the structure of a cathode in Example 4;
29 is an initial charge/discharge curve of a half-cell at 0.01 C to which Example 4 negative electrode was applied.
30 is a graph of cycle characteristics of a battery to which a carbonate electrolyte is applied for 10 cycles at a current density of 0.1 C.
31 is a graph showing a charge/discharge curve of a battery to which a carbonate electrolyte is applied for 10 cycles at a current density of 0.1C.
32 is a graph of cycle characteristics of Comparative Examples 2-1 and 2-2.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

In this specification, the terminology used is only for referring to specific embodiments and is not intended to limit the present invention. Singular forms as used herein also include plural forms unless the phrases clearly indicate the opposite. In the present specification, when a certain part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

When a part of a layer, film, region, plate, etc. is said to be "above" or "on" another part, this includes not only the case where the other part is "directly over" but also the case where there is another part in the middle. In addition, throughout the specification, the term "on" means that it is located above or below the target part, and does not necessarily mean that it is located above or below the direction of gravity.

In the present specification, the metal layer is used to include a plate-like (plate-shaped) metal having a thickness and an area.

In the present specification, the alloying material absorbs sodium by electrochemically reacting and alloying with an alkali metal or alkaline earth metal such as sodium, and electrochemically absorbs sodium and the like by electrochemically releasing sodium and the like by dealloying, It means a material that can be released. These alloying materials (metal active materials) are gallium (Ga, gallium), germanium (Ge, germanium), indium (In, indium), tin (Sn, tin), antimony (Sb, antimony), thallium (Tl, thallium), It may be selected from the group including lead (Pb, lead), bismuth (Bi, bismuth), and alloys thereof. However, it is not limited to the metals listed above, and metals capable of reversibly absorbing and releasing alkali metal or alkaline earth metal ions by alloying and dealloying with alkali metal or alkaline earth metal may be included therein.

A material that can be absorbed and released through an alloying and dealloying reaction with the alloying material may be an alkali metal or an alkaline earth metal, and the alloying and dealloying reaction has the following chemical reaction formula.

xA+ M ↔ A _x M

In the above chemical reaction formula, A is an alkali metal or alkaline earth metal, and M is an alloying material.

At this time, most of the values of x exceed 1, so the alloying material shows a high theoretical capacity.

For example, when tin reacts with sodium _{to form the final product Na 15} Sn ₄ (x=3.75), it exhibits a high theoretical capacity of 847 mAh/g. Table 1 below shows sodiumation reaction products and theoretical capacity according to the type of alloying material.

Referring to Table 1 below, it can be seen that the ion capacity of the alloying material may vary depending on the type of the alloying material. In addition, the alloying material may have a different capacity depending on the degree of sodiumization.

Cathode material
(Anode material) Sodiumation products
(Sodiation product) Theoretical capacity
(Theoretical capacity) Ga Na _0.56 Ga (Na ₂₂ Ga ₃₉ ) 217 Ge Na ₃ Ge 1106 In NaIn 233 Sn Na _3.75 Sn (Na ₁₅ Sn ₄ ) 847 Sb Na ₃ Sb 660 Tl Na ₆ Tl 787 Pb Na ₁₅ Pb ₄ 485 Bi Na ₃ Bi 385

However, the volume of the alloying material (M) expands when alloyed with an alkali metal or alkaline earth metal such as sodium (A _x M), and returns to the original alloying material (M) during dealloying and decreases in volume. Therefore, when the alloying material is applied as an electrode active material, when charging and discharging a battery, alloying and dealloying occurs in the electrode active material, and the intrinsic problem of causing volume change of volume expansion and contraction in the alloyed material is solved. Cause. In other words, the volume change due to charging and discharging causes internal stress in the alloyed material, which leads to the generation of cracks in the electrode active material (layer), and the electrode active material (layer) is split by growing cracks. This leads to a process in which the electrode active material is pulverized into smaller particles. Such pulverization of the electrode active material (layer) causes a problem that the electrode active material (layer) is disconnected from the current collector or the conductive material in the electrode. Thus, since electrons are not supplied from the current collector, it is placed in a state in which the electrochemical reaction can no longer be performed, and as the charging and discharging proceeds repeatedly, a rapid decrease in capacity occurs. As a result, an electrode having an alloying mechanism has a short charge/discharge cycle life.

In order to solve the pulverization problem due to a large volume change rate during charging and discharging of the electrode active material, a method of making the active material into fine particles may be considered. However, in the case of the process of pulverizing the active material into fine particles, there is a problem of increasing the electrode price by entailing a complicated and expensive process cost.

In addition, when a powder electrode active material is used, a polymer binder is used to fix the powder electrode active material to the current collector, and a conductive material for improving conductivity is further included. However, these polymeric binders and conductive materials are materials that do not react electrochemically, and since the content of the active material in the electrode decreases, the total capacity of the electrode is reduced.

In order to provide a space to accommodate volume expansion of the electrode active material during charging and discharging, a porous structure can be designed using an electrode active material, the same material, and a different material. However, even if the porous structure is designed using the same material, there is a problem that a fine powdering technique is required, and the manufacturing process becomes complicated. In addition, when designing a porous structure using dissimilar materials, a material that does not react electrochemically is added to the electrode, thereby reducing the total capacity of the electrode.

In addition, since the electrode using powder has a low tap density, the compression process must be entered. Even if the electrode is compressed, the processing density of the electrode using powder must be lower than that of an electrode made of a single mass. It is also generally very difficult to increase the processing density of an electrode containing them. For the same reason, it is difficult to increase the thickness in order to improve the loading amount of electrodes per area.

Moreover, even if all of the above methods are used, it is not possible to fundamentally solve the problem of pulverization of the electrode active material layer due to volume change occurring during a charge/discharge cycle, a decrease in capacity, and a decrease in cycle characteristics, which is an essential problem.

The negative electrode included in the secondary battery of the present application includes an electrode active material of an alloyed material having a high capacity in the form of a metal layer, thereby providing a negative electrode for a secondary battery having a high density and a high capacity. In addition, since the negative electrode included in the secondary battery of the present application may not necessarily contain a conductive material and/or a binder, it may contribute to an improvement in electrode capacity and battery capacity. Since the metal layer can perform the role of the electrode active material layer and the current collector together, the volume can be minimized while securing an improved capacity.

In addition, when an electrode active material of such an alloyed material is used, a secondary battery capable of solving the problem of deterioration of charge/discharge cycle characteristics due to a large volume change rate during charging and discharging can be provided.

Secondary battery

A secondary battery according to an embodiment of the present invention includes a negative electrode; anode; And an electrolyte interposed between the positive electrode and the negative electrode.

The negative electrode includes a metal layer including a metal capable of reversible absorption and release of alkali metal or alkaline earth metal ions by alloying and dealloying with an alkali metal or alkaline earth metal, and the electrolyte includes an ether solvent and a metal salt. .

Metals capable of reversible absorption and release of alkali metal or alkaline earth metal ions by alloying and dealloying with alkali metal or alkaline earth metal include Ga, Ge, In, Sn, Sb, Tl, Pb, or Bi.

The metal layer may include a metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi.

As described above, these metals have a high theoretical capacity, but there is a problem that the volume expansion due to alloying is large. That is, when applied to an electrode, as charging and discharging are repeated, the active material layer is pulverized, separated from the current collector, and electrical connection is disconnected, and cycle characteristics are deteriorated.

Accordingly, these metals are generally used as nanoparticles, but even in this case, due to a large volume change rate, the problem of deteriorating cycle characteristics cannot be completely solved.

However, according to one embodiment of the present invention, the above-described metal having such a high theoretical capacity may be applied to the negative electrode of the secondary battery in the form of a metal layer.

The metal layer may contain 97 mass% or more of the metal based on 100 mass% of the metal layer. Specifically, the metal may include 97 to 100% by mass, 98 to 100% by mass, 99 to 100% by mass, or 99.5 to 100% by mass. The balance may include other metals and/or unavoidable impurities.

Most preferably, it may contain 100% by mass of the metal.

In the case of using the above-described metal having a high theoretical capacity in the negative electrode for a secondary battery in the form of a metal layer, as in the embodiment of the present invention, the tap density is high compared to the case of using an active material in the form of powder, and electrochemically Since it does not require an unreacted binder and/or a conductive material, there is an advantage in that the capacity of the negative electrode can be improved.

The negative electrode includes a metal layer including a metal capable of reversible absorption and release of alkali metal or alkaline earth metal ions by alloying and dealloying with an alkali metal or alkaline earth metal. The negative electrode may further include a current collector, but is not limited thereto. This is because the metal layer is made of a metal having conductivity, and thus the metal layer can serve as an active material layer and a current collector together.

The electrolyte may include an ether-based solvent.

The ether solvent may be selected from the group including DME, TEGDME, DEGDME, PEGDME, and PEO.

Specifically, dimethoxyethane (DME), 1,3-dioxolane (1,3-dioxolane), tetraethylene glycol dimethyl ether (TEGDME), Diethylene glycol dimethyl ether , DEGDME), triethylene glycol dimethyl ether (TEGDME), polyethylene glycol dimethyl ether (PEGDME), polyethylene oxide (PEO), and dioxolane (DOL) and their It may be selected from the group containing a mixture.

In the case of using an ether-based solvent, a solid electrolyte interface (SEI) layer may not be formed or may be formed very thin during the charging/discharging process of the battery. Therefore, even if the metal layer is cracked or pulverized during the charging/discharging process, the cracked or pulverized metal layers can contact each other during expansion, so that the electrical connection of the metal layers can be maintained, so that repeated charging/discharging may be possible. As a result, in the case of using an ether-based solvent, the problem of separation of active material particles from the current collector and/or electrical connection of the active material layer due to pulverization of the active material layer, despite the large volume change rate during charging and discharging of the metal layer It can be solved.

The metal layer may have a thickness of 1 μm to 2 mm. The thickness of the metal layer can be adjusted according to the required capacity of the electrode. However, since the cathode of the present application includes a metal layer in the form of a foil, there is an advantage in that a metal layer and/or a metal active material layer can be formed thicker than the metal layer of the plating method. Specifically, in a specific example of the present invention described later, a metal layer is formed by rolling an active material metal. In this case, there is an advantage in that a metal layer having a desired thickness can be formed according to a desired capacity by a simple method, and a cathode having a high capacity can be easily formed according to the thickness. Since the active material layer is the entire electrode and maintains its shape by metal bonding, it can be easily cut and manufactured into an electrode of a specific shape without risk of detachment of the active material.

The electrolyte may include a metal salt and an ether-based solvent. Specifically, the metal salt is NaPF ₆ , NaClO ₄ , NaCF ₃ SO ₃ , NaBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiBF ₄ , LiTFSI, Mg(PF ₆ ) ₂ , Mg(ClO ₄ ) ₂ , Mg(CF ₃ SO ₃ ) ₂ , Mg(BF ₄ ) ₂ , Mg(TFSI) ₂ , Mg(HMDS) ₂ , and MgCl ₂ .

The anode is CuS. It may be selected from the group including Cu ₂ S, NiS, Ni ₃ S ₂ , NiS ₂ , TiS ₂ , and MoS _3. However, it is not limited thereto, and includes those that can be applied to the technical common sense of the relevant technical field.

The secondary battery according to the exemplary embodiment of the present invention may further include a separator between the positive electrode and the negative electrode.

The separation membrane may be a nanoporous separation membrane.

The nanopore separation membrane may have a pore size of 10 nm to 100 nm.

If the above range is satisfied, it may serve as a physical barrier so that the pulverized metal layer particles are not separated from the negative electrode according to battery charging and discharging. Accordingly, the pulverized metal layer particles may be attached to the metal layer to continuously serve as an active material, and a charge/discharge cycle life may be improved. If the pores of the separator are too large, the pulverized metal layer particles may be separated or separated from the negative electrode and the cycle characteristics may be deteriorated.If the pores of the separator are too small, impregnation of the electrolyte is difficult and the contact area between the electrolyte and the electrode decreases. Ion transfer may not be smooth, and consequently, ion conduction required for driving the battery may not be satisfied.

The thickness of the nanopore separation membrane may be 5 μm to 1 mm. When the above range is satisfied, it serves as a sufficient physical barrier to prevent separation from the pulverized metal layer, thereby contributing to improvement of cycle characteristics.

In an embodiment of the present invention to be described later, Celgard 2400 (thickness 25 µm, pores 100 nm or less) was used as a nanopore separation membrane.

The separation membrane may be a microporous separation membrane.

The micropore separation membrane may have a pore size of 1 μm to 50 μm.

The microporous separation membrane may have a thickness of 0.2mm to 2mm.

When the above numerical range is satisfied, the microporous separator can prevent a short circuit inside the battery due to the formation of dendrite generated on the electrode surface during the charging and discharging process.

In an embodiment of the present invention to be described later, a glass fiber filter (about 1 mm in thickness, 10 µm or more pores) was used as a microporous separation membrane.

According to one embodiment of the present invention, a plurality of microporous separation membranes and/or microporous separation membranes may be included.

In an embodiment of the present invention to be described later, a triple separation membrane (Celgard 2400 / glass fiber filter / Celgard 2400) in which nanoporous separation membranes are positioned on both sides of one microporous separation membrane, respectively, was used. Specifically, the nanoporous separator may be in contact with each electrode, and a microporous separator may be positioned between the two nanoporous separators.

In this case, the role of the glass fiber filter may delay the time of internal short circuit due to sodium metal or dendritic phase of the anode.

In addition, Celgard 2400 in contact with the anode can suppress the formation of dendritic phase of the anode.

Celgard 2400 in contact with the cathode prevents the metal layer particles pulverized with nano pores from separating from the cathode and can delay the internal short circuit due to the formation of dendritic phase of the anode.

As a result, it is possible to improve the charge/discharge cycle characteristics of the electrode.

According to another embodiment of the present invention, the metal layer includes a first metal layer including a first metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi, and on the first metal layer. A second metal layer including a second metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi positioned at may be included.

The first metal and the second metal may be metals different from each other.

In this case, it is easy to design the required battery voltage and capacity within a limited volume.

The metal layer may further include an alloy active material layer including an alloy of a first metal and a second metal between the first metal layer and the second metal layer. This may be due to the manufacturing method of the present invention. Specifically, in the process of forming the second metal layer by rolling the second metal on the first metal layer, an alloy of the first metal and the second metal may be formed at the interface between the first metal layer and the second metal layer.

In one specific embodiment of the present invention to be described later, a cathode in which a Pb metal layer and a Sn metal layer are sequentially stacked is disclosed.

*

Method of manufacturing secondary battery

A method of manufacturing a secondary battery according to an exemplary embodiment of the present invention includes the steps of manufacturing a negative electrode having a metal layer formed thereon; And manufacturing a battery including the negative electrode, the electrolyte, and the positive electrode.

The electrolyte includes an ether solvent and a metal salt, and the metal layer includes a metal capable of reversible absorption and release of alkali metal or alkaline earth metal ions by alloying with an alkali metal or alkaline earth metal.

The manufacturing of the negative electrode on which the metal layer is formed may include manufacturing a negative electrode on which the metal layer is formed by rolling a metal.

According to an embodiment of the present invention, it is possible to manufacture a negative electrode by a simple method by rolling, and it is possible to easily adjust the thickness and the capacity of the negative electrode. In addition, there is an advantage in that a large-area negative electrode and various types of negative electrodes can be manufactured by a simple method.

After the manufacturing of the negative electrode, the negative electrode on which the metal layer is formed, and a half-cell including the metal electrode may be formed, completely discharged, and then partially charged. In this case, not only can the initial reversible capacity be improved, but also the capacity of the negative electrode can be controlled according to the adjustment of the charge amount. Specifically, the smaller the amount of charge, the greater the amount of alkali metal or alkaline earth metal ions that can be accommodated in the negative electrode.

The partial charging means full charging, that is, not 100% charging. When fully charged in the above step, the alkali metal or alkaline earth metal is inserted into the metal layer to the maximum limit to form an alloying. Therefore, when the fully charged negative electrode in the half-cell step is applied to the full-cell, the negative electrode cannot accommodate alkali metal or alkaline earth metal ions that have moved from the positive electrode to the negative electrode through the electrolyte.

The manufacturing of the electrode may include rolling a first metal to form a first metal layer, and rolling a second metal on the first metal layer to form a second metal layer.

The first metal and the second metal include a metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi, and the first metal and the second metal may be different metals. have.

Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited to the following examples.

Example 1- A cathode comprising a Sn metal layer

The Sn metal was rolled to form an Sn metal layer having a thickness of 27 μm, and punched with a diameter of 6 mm and 10 mm, respectively, to prepare a negative electrode of Example 1-1 and Example 1-2.

1 is a schematic diagram of a negative electrode included in a battery according to an embodiment of the present invention. It is shown that the cathode includes an Sn metal layer.

2 is an actual photograph of the Sn metal layer of the negative electrode of Example 1-1. A metal layer having a metallic luster can be identified.

Evaluation Example 1-1-Example 1 Evaluation of half-cell characteristics using negative electrode

3 is a design diagram of a battery for electrode evaluation. In order to evaluate the characteristics of the electrode of the present invention, a half-cell test was performed, and for this purpose, sodium metal as a counter electrode and Celgard 2400 and a GF/D filter (glass fiber filter) as a separator membrane were used together. Was used. The electrodes of the examples were stacked on the separator and the battery was sealed to form a sealed half-cell to evaluate electrode performance. 1M NaPF6 + DME electrolyte was sufficiently inserted to wet all electrodes and separators so that ion transfer through the electrolyte was not cut off.

In the half-cell experiment, the use of a single Celgard 2400 (thickness = 25 µm) cannot suppress the formation of dendrite on the counter electrode surface during the charging and discharging process of the sodium metal counter electrode, and the dendritic phase grows as the cycle progresses. An internal short-circuit occurs.

Therefore, a thick glass fiber filter (thickness = about 1 mm) was used to suppress dendritic growth of the sodium metal counter electrode.

Celgard 2400 in contact with sodium metal can suppress the dendritic phase of sodium metal due to nanopore. In addition, the Celgard 2400 in contact with the negative electrode in Example 1 prevents the metal particles of the metal layer pulverized into nanopores from being separated from the negative electrode, and can delay the internal short circuit due to the dendritic phase of sodium.

4 is a graph showing cycle characteristics at a current density of 0.1 C (84.7 mA/g) of the negative electrode of Example 1-1. The initial discharge capacity was 767 mAh/g, and the initial charging capacity was 666 mAh/g. After the 5th cycle, both the discharge capacity and the charge capacity were 800 mAh/g, and the charging and discharging efficiency achieved 100%. After that, a gradual decrease in capacity occurred, but a high capacity of 692mAh/g was maintained even after 100 cycles.

5 is a graph showing charge/discharge curves of the 50th cycle at the current density of 0.1 C of the negative electrode of Example 1-1. Both the discharging capacity and the charging capacity were high at 725 mAh/g, and four flat voltage sections were clearly observed during charging.

6 shows a charge/discharge curve at 0.01 C of the negative electrode in Example 1-1. The initial discharge capacity was 857 mAh/g, and the initial charging capacity was 777 mAh/g. During the charging and discharging process, four flat sections were clearly observed, and after 3 cycles, the charging/discharging capacity was 800 mAh/g, indicating a charging/discharging efficiency of 100%.

7 is a graph showing charge/discharge curves according to various current densities of Example 1-1. At 0.1C, 0.2C, 0.4C, 0.8C, and 1.6C, the charging capacities were 781 mAh/g, 778 mAh/g, 671 mAh/g, 245 mAh/g, and 49 mAh/g, respectively. The efficiency is 100% regardless of the current density.

8 is a graph showing charge/discharge curves at a current density of 0.01C of Example 1-2 of the present invention. As the cycle progresses, the capacity decrease does not occur, and it maintains a high capacity of 685 mAh/g after 6 cycles.

9 is a graph showing cycle characteristics for 100 cycles at current densities of 0.5 C and 1 C of the negative electrode of Example 1-1. At 0.5C current density, the initial discharge capacity was 569 mAh/g, the initial charging capacity was 547 mAh/g, and the capacity increased up to 39 cycles, resulting in a high capacity of 719 mAh/g in both charge and discharge capacity, and 694 after 100 cycles. It maintains a high capacity of mAh/g. At the current density of 1C, the initial discharge capacity was 279 mAh/g, the initial charge capacity was 242 mAh/g, and both charge and discharge capacity after 100 cycles were 164 mAh/g.

10 is a SEM photograph of the surface of the Sn metal layer of the negative electrode in Example 1-1. It can be seen that it has a smooth metal surface.

11 is an EDS mapping photograph of the Sn metal layer of the cathode in Example 1-1.

It can be seen that the Sn metal layer is made of only tin.

12 is an EDS spectrum of the Sn metal layer of the negative electrode in Example 1-1.

By only the peak corresponding to tin appears, it can be confirmed that only tin is present in the Sn metal layer.

13 is an XRD result of the cathode Sn metal layer in Example 1-1.

In FIG. 13, when looking at the XRD results showing the crystal structure of Example 1-1 cathode Sn metal layer, peaks similar to those of JCPDS#894898 appearing in tin powder appear. However, from the peak ratio of XRD, it can be seen that the Sn metal layer of Example 1-1 has a preferred orientation, which is that the Sn metal layer of the cathode of Example 1-1 was not made of powder. Can be confirmed, and it can be seen that this is because the process of rolling the metal is used when manufacturing the Sn metal layer.

14 is a photograph showing a state in which the Sn metal layer of the negative electrode in Example 1-1 completely reacted with Na. (Standard ruler 2mm)

It can be seen that the metal layer surface lost its metallic luster due to the reaction with Na, and no visible cracks were observed on the metal layer even after the reaction with Na.

15 is a SEM photograph of a state in which the Sn metal layer of the negative electrode of Example 1-1 completely reacted with Na. It can be seen that the metal layer surface lost its metallic luster due to the reaction with Na, and no visible cracks were observed on the metal layer even after the reaction with Na.

16 is a real photograph of the metal layer after 20 cycles of the negative electrode in Example 1-1 (2 mm standard ruler). It was confirmed that there were no visible cracks on the surface of the metal layer even after 20 cycles.

Evaluation Example 1-2: Evaluation of full-cell characteristics using the negative electrode of Example 1

17 is a diagram showing the structure of a full-cell using the cathode and the NVP[Na ₃ V ₂ (PO ₄ ) _{3] anode of Example 1-1.}

Example 1-1 A negative electrode, Celgard 2400, GF/D glass fiber filter, Celgard 2400, and NVP positive electrode were stacked in this order, and 1M NaPF ₆ + DME was injected as an electrolyte, and then the battery was sealed to construct a battery.

At this time, the negative electrode of Example 1-1 constituted a half-cell of FIG. 3, was completely discharged at 0.01 C, and then charged to about 350 mAh/g. The value of this charging capacity means that the tin electrode is charged to the end of the first flat voltage region around 0.15V in the charging curve. That is, the negative electrode of Example 1-1 was reacted with sodium in advance using a half-cell, and this was separated from the half-cell to constitute an NVP electrode and a full-cell. The first assembled full-cell was charged first, followed by a charging/discharging test.

18 is a diagram showing the structure of a Na/NVP half-cell for confirming the characteristics of the NVP anode.

Before evaluating the Sn/NVP full-cell, a test of the Na/NVP half-cell was performed to confirm the characteristics of the NVP positive electrode. A half-cell was constructed by sequentially laminating the NVP anode, Celgard 2400, GF/D glass fiber filter, and sodium metal.

19 is a graph of charge/discharge curves at a current density of 1A/g of a Na/NVP half-cell. The discharge capacity was 97 mAh/g, the flat voltage during discharge was 3.35V, and the flat voltage during charging was 3.40V.

20 is a graph showing rate characteristics and cycle characteristics of a full-cell composed of a negative electrode and an NVP positive electrode of Example 1-1. As a result of conducting the rate characteristics for 5 cycles at currents of 0.1A/g, 1A/g, 2A/g, and 4A/g, the discharge capacity was shown as 105mAh/g, 99mAh/g, 91mAh/g, and 81mAh/g, respectively. After 300 cycles at 1A/g, the discharge capacity was 97 mAh/g.

21 is a graph showing charge/discharge curves at a current density of 1 A/g of a full-cell composed of a cathode and an NVP anode of Example 1-1. The flat voltage during discharge was 3.23V, and the flat voltage during charging was 3.34V.

The voltage may be added or subtracted according to the current density, the thickness of the electrode, the type of the electrolyte, the type of the separator, and the shape of the electrode.

Example 2-A cathode comprising a Pb metal layer

The Pb metal was rolled to a thickness of 30 μm and punched to a diameter of 10 mm to prepare a negative electrode of Example 2 including a Pb metal layer.

22 is an actual photograph of the cathode of Example 2. A metal layer having a lead metal surface can be identified.

23 is an XRD result of Example 2 cathode PB metal layer.

Example 2 Looking at the XRD results showing the crystal structure of the negative electrode PB metal layer, a peak similar to that of JCPDS#870663 appears in lead powder. However, it was confirmed that the cathode PB metal layer in Example 2 was not made of powder and could have a preferred orientation because the rolling process was used.

Evaluation Example 2-1: Evaluation of half-cell characteristics using the negative electrode of Example 2

24 is a charge/discharge curve at a current density of 0.01 C (4.85 mA/g) of the cathode Pb metal layer in Example 2. FIG.

Example 2 A half-cell having the structure of FIG. 3 was manufactured using a negative electrode. The initial discharge capacity was 498mAh/g, and the initial charging capacity was 434mAh/g. During initial discharge, three flat voltage sections were shown at 0.32V, 0.15V, and 0.10V, and four flat voltage sections were shown at 0.13V, 0.20V, 0.38V, and 0.51V during initial charging. In the second discharge, there are four flat voltage sections of 0.50V, 0.34V, 0.17V, and 0.10V, which are a voltage section that corresponds well to the flat voltage section that appears during initial charging. In addition, the second discharge capacity is 441 mAh/g, which represents a charging/discharging efficiency of almost 100% compared to the initial charging capacity.

Example 3-Cathode comprising Bi metal layer

Bi metal was rolled to a thickness of 200 μm and punched to a diameter of 6 mm to prepare a negative electrode of Example 3 including a Bi metal layer.

25 is a photograph of the Bi metal layer of the negative electrode of Example 3. It can be seen that the Bi metal layer of the prepared Example 3 negative electrode has a smooth metal surface.

Evaluation Example 3-1: Evaluation of half-cell characteristics using the negative electrode of Example 3

26 is a charge/discharge curve at 0.1 C of the negative electrode of Example 3.

Example 3 A half-cell having the same structure as in FIG. 3 was assembled using a negative electrode.

Example 3 It can be seen that the negative electrode exhibits a reversible capacity of 321 mAh/g even at 130 cycles, and maintains a capacity of 83.4% compared to the theoretical capacity (385 mAh/g).

27 is a charge/discharge curve at 0.01 C of the negative electrode of Example 3.

Example 3 A half-cell having the same structure as in FIG. 3 was assembled using a negative electrode. It shows a reversible capacity of 367 mAh/g even at 20 cycles, and maintains a capacity of 95.3% of the theoretical capacity.

Example 4-A cathode in which a Pb metal layer and a Sn metal layer are sequentially stacked

Rolling the Pb metal to form a Pb metal layer with a thickness of 30 μm, and rolling the Sn metal on the Pb metal layer to form a Sn metal layer with a thickness of 27 μm, and punching it in a circular shape with a diameter of 10 mm to prepare an Example 4 negative electrode including two metal layers I did.

28 is a schematic diagram showing the structure of a cathode in Example 4; It shows that the Pb metal layer and the Sn metal layer are located.

Evaluation Example 4-1: Evaluation of half-cell characteristics using the negative electrode of Example 4

FIG. 29 illustrates an initial charge/discharge curve at 0.01 C after assembling a half-cell having the structure of FIG. 3 using the cathode of Example 4.

The initial discharge capacity and charging capacity are approximately 570 mAh/g and 500 mAh/g. A distinct flat section appears in both the discharge curve and the charging curve, and this flat section may include 4 flat sections appearing in the tin foil electrode and 4 flat sections appearing in the lead foil electrode, and the flat section made by the tin-lead alloy. May appear. The sequential stacked structure of dissimilar metal active materials can easily design the capacity of the electrode, and it is easy to flexibly design the charge/discharge voltage.

Evaluation Example 5-Evaluation of battery characteristics according to application of ether-based electrolyte

As Inventive Example 1, sodium metal, Celgard 2400, GF/D glass fiber filter, Celgard 2400, Example 1-1 were stacked in the negative electrode order, and an electrolyte containing _{DME as an ether solvent and 1M NaPF 6 metal salt was injected.} , The battery was sealed to construct a battery.

As Comparative Example 1, sodium metal, Celgard 2400, GF/D glass fiber filter, Celgard 2400, Example 1-1 were stacked in the negative electrode order, and the carbonate-based solvent EC/DEC (ethylene carbonate/diethyl carbonate, 1:1 volume ratio) ) And a metal salt of 1M NaClO ₄ , and after injecting an electrolyte containing an additive FEC (fluoroethylene carbonate, 5%), the battery was sealed to construct a battery.

30 is a graph of cycle characteristics at a current density of 0.1 C for 10 cycles of a battery using the carbonate electrolyte described above. The initial discharge capacity was 1.25 mAh/g, and the initial charging capacity was 0.1 mAh/g. After 10 cycles, a reversible capacity of less than 0.1 mAh/g appeared without an increase in capacity.

31 is a graph showing a charge/discharge curve at a current density of 0.1 C during 10 cycles of a battery using the carbonate electrolyte described above. Charging and discharging is performed without a flat voltage section, and capacity is hardly seen.

The cycle characteristics and charge/discharge curves of the battery of Inventive Example 1 of the present application are shown in FIGS. 4 and 5.

4 is a graph showing cycle characteristics at a current density of 0.1 C (84.7 mA/g) of a half-cell made of sodium metal and a cathode of Example 1-1. The initial discharge capacity was 767 mAh/g, and the initial charging capacity was 666 mAh/g. After the 5th cycle, both the discharge capacity and the charge capacity were 800 mAh/g, and the charging and discharging efficiency achieved 100%. After that, a gradual decrease in capacity occurred, but a high capacity of 692mAh/g was maintained even after 100 cycles. 5 is a graph showing a charge/discharge curve of the 50th cycle at a current density of 0.1C of the battery of Inventive Example 1 of the present application. Both the discharging capacity and the charging capacity were high at 725 mAh/g, and four flat voltage sections were clearly observed during charging.

That is, it can be seen that when a carbonate-based electrolyte other than an ether-based electrolyte is applied to the negative electrode of Example 1-1, the capacity hardly appears.

Evaluation Example 6-Evaluation of battery characteristics according to the application of a triple separator

In the same manner as in Invention Example 1, as shown in FIG. 3, sodium metal, Celgard 2400, GF/D glass fiber filter, Celgard 2400, Example 1-1 were laminated in the negative order, and the ether-based solvent DME and metal salt 1M NaPF ₆ were included. After injecting the electrolyte, the battery is sealed to form a battery.

As Comparative Example 2-1, the same as Inventive Example 1, but using only Celgard 2400 as a separator, a battery was constructed.

As Comparative Example 2-2, the same as Inventive Example 1, but using only a GF/D glass fiber filter as a separator, a battery is constructed.

* Fig. 32 is a graph of cycle characteristics of Comparative Examples 2-1 and 2-2. In both cases, the reversible capacity was over 600mAh/g in the initial cycle, but the capacity rapidly decreased to 458 mAh/g and 330 mAh/g during 100 cycles. In the case of Comparative Example 2-1 using only Celgard 2400 as a separator, it can be observed that the charging capacity increases significantly compared to the discharge capacity after 20 cycles. This is due to the formation of sodium dendrite due to the absence of the glass fiber filter. It is believed to be in accordance with the paragraph. In the case of Comparative Example 2-2 using only a glass fiber filter as a separator, the capacity steadily decreases, which is believed to be because the electrode is pulverized and separated from the current collector and the separator, thereby reducing the active material. That is, it was confirmed that neither the micropore separation membrane nor the nanopore separation membrane could exhibit stable cycle characteristics.

In contrast, looking at the graph showing the charging/discharging curve of Inventive Example 1 of FIG. 4, the reversible capacity of the initial cycle is 665 mAh/g, and the reversible capacity after 100 cycles is 692 mAh/g, even when charging and discharging is performed. It can be seen that no reduction in dose occurs.

That is, it can be seen that cycle characteristics can be improved by using a multi-membrane including a nano-pore separation membrane and a micro-pore separation membrane.

The present invention is not limited to the above embodiments, but may be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains, other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented with. Therefore, it should be understood that the embodiments described above are illustrative in all respects and are not limiting.

Claims (13)

cathode;
anode; And
Including; an electrolyte interposed between the positive electrode and the negative electrode,
The cathode is
It includes a metal layer containing a metal capable of reversible absorption and release of alkali metal or alkaline earth metal ions by alloying and dealloying with an alkali metal or alkaline earth metal,
The electrolyte is
It contains an ether-based solvent and a metal salt,
Secondary battery.
The method of claim 1,
The metal layer includes a metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi,
Secondary battery.
The method of claim 1,
The metal layer contains 97% by mass or more of the metal based on 100% by mass of the total metal layer,
Secondary battery.
The method of claim 1,
The metal layer has a thickness of 1 μm to 2 mm,
Secondary battery.
The method of claim 1,
The metal layer is in the form of a metal foil,
Secondary battery.
The method of claim 1,
The ether solvent is dimethoxyethane (DME), 1,3-dioxolane (1,3-dioxolane), tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (Diethylene glycol). dimethyl ether, DEGDME), triethylene glycol dimethyl ether (TEGDME), polyethylene glycol dimethyl ether (PEGDME), polyethylene oxide (PEO), and dioxolane (DOL) Including those selected from the group containing,
Secondary battery.
The method of claim 1,
The anode is CuS. Cu ₂ S, NiS, Ni ₃ S ₂ , NiS ₂ , TiS ₂ , and MoS ₃ to be selected from the group containing,
Secondary battery.
The method of claim 1,
Further comprising a separator between the anode and the cathode,
The separation membrane is a nanoporous separation membrane having pores of 10 nm to 100 nm,
Secondary battery.
The method of claim 8,
It further comprises a micropore separation membrane having pores of 1 μm to 50 μm,
Secondary battery.
The method of claim 1,
The metal layer is
Ga, Ge, In, Sn, Sb, Tl, Pb, and comprises two or more metal layers containing a metal selected from the group containing Bi,
Each of the metal layers comprises different metals from each other,
Secondary battery.
Rolling a metal to prepare a negative electrode on which a metal layer is formed; And
Including; and the step of manufacturing a battery comprising the negative electrode, the electrolyte, and the positive electrode,
The electrolyte contains an ether solvent and a metal salt,
The metal layer includes a metal capable of reversible absorption and release of alkali metal or alkaline earth metal ions by alloying with an alkali metal or alkaline earth metal,
Secondary battery manufacturing method.
The method of claim 11,
After the step of preparing the negative electrode
Comprising a negative electrode including the metal layer and a half-cell including a metal electrode, and completely discharging and then partially charging,
Secondary battery manufacturing method.
The method of claim 11,
The step of manufacturing the electrode
The first metal layer is formed by rolling the first metal,
Rolling a second metal on the first metal layer to form a second metal layer,
The first metal and the second metal include a metal selected from the group including Ga, Ge, In, Sn, Sb, Tl, Pb, and Bi,
The first metal and the second metal are metals different from each other,
Secondary battery manufacturing method.

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