KR20090027901A - Method of manufacturing a lithium secondary battery - Google Patents

Abstract

A method for manufacturing a lithium secondary battery is provided to perform the operation at room temperature or high temperature, and to realize steadily big capacity by activating transition metal alloys or transition metal oxides which are not reactive or less reactive with lithium at room temperature. A method for manufacturing a lithium secondary battery comprises a step of forming an electrode having an active material layer including transition metal alloys or transition metal oxides; and a step of electrochemically activating the electrode by charging or recharging at a temperature of 50-200 °C. The transition metal alloys is the following chemical formula 1: AxBy. In the chemical formula 1, A comprises any one selected from Si, Sn, Al, Ge, Ga, In, Sb, Pb, Bi, Mg and Zn; B comprises any one selected from Cu, Ni, Co, Fe, Mn, Cr, V, Ti, Sc, Mo, Ru and W; and 0<x<=1, 0<y<=1.

Description

Manufacturing method of lithium secondary battery {METHOD OF MANUFACTURING A LITHIUM SECONDARY BATTERY}

The present invention relates to a method for manufacturing a lithium secondary battery, and more particularly to a method for manufacturing a lithium secondary battery using a transition metal alloy or transition metal oxide as a negative electrode material.

In general, graphite-based materials having stable battery characteristics are widely used as negative electrode materials of lithium secondary batteries. However, in order to satisfy the requirements of the market of miniaturized and high output lithium secondary batteries, researches are being actively conducted to develop materials that exceed the limit of the theoretical capacity of graphite (about 372 mAh / g).

As a substitute for graphite, a negative electrode material having high reactivity with lithium such as tin (992 mAh / g) and silicon (4200 mAh / g) (which can be alloyed with lithium can be charged and discharged in a lithium secondary battery). A material having a high activity against (hereinafter referred to as an alloy-based material) has been studied. However, such an alloy-based anode material undergoes a large volume change (about 310% for Li ₂₂ Si ₅ and about 260% for Li ₂₂ Sn ₅₎ during charge and discharge reaction with lithium. Electrical shorts occur in the material, resulting in rapid deterioration of cell performance. In order to solve this problem, a method of preparing such an alloy-based negative electrode material to a nano size, a method of making a compound such as oxide, nitride, sulfide, alloying with at least one other element that does or does not react with lithium, The method of thinning, the method of using a high performance binder, etc. have been tried.

When alloying with one or more other elements that do not react or react with lithium to produce a negative electrode material (where alloying refers to a reaction between an element that does not or does react with lithium and the alloy material), charge and discharge It is possible to suppress the aggregation of the alloying elements according to the, and the transition metal that does not react with lithium has the advantage of improving the electrode performance by the effect of buffering the volume change caused by the reaction with the lithium of the alloying material. However, many of the above alloy-based compounds (materials alloyed by reaction between lithium or a non-reacting element with an alloy-based material) can be reacted by thermodynamics, but for kinetic reasons, again. In other words, the reaction with lithium is known to be inactive or limited in activity to lithium ions at room temperature. In particular, many transition metal-silicon compounds, including copper or nickel, are known to have no activity at room temperature. (J.H. Kim, H. Kim, H.J. Sohn, Electrochem.Commun. 7, 2005)

Various transition metal oxides are being studied as another material that can replace graphite. These transition metal oxides precipitate Li ₂ O and nano-sized transition metals when lithium is inserted and the addition reaction of lithium is inserted while the bond between the transition metal and oxygen is maintained or the bond between the transition metal and oxygen is broken. The conversion reaction takes place. In these two reactions, due to the crystal structure of the transition metal oxide and the bonding force between the transition metal and oxygen, a large number of transition metal oxides having inertness or limited activity to lithium ions are generated at room temperature, which makes it difficult to perform as a negative electrode material at room temperature. It is known.

In order to induce the activity at room temperature of these inert or limited activity compounds at room temperature using a high energy ball-milling method or particles of several tens of nanometers or less in order to use as a negative electrode material of the lithium secondary battery Although methods such as manufacturing have been attempted, there are few examples of having an activity at room temperature, and these methods have a disadvantage of having to undergo a complicated process in the preparation of the active material.

Accordingly, an object of the present invention is to provide a method for manufacturing a lithium secondary battery which can operate at room temperature or at high temperature by electrochemically activating a transition metal alloy or transition metal oxide which is not reactive with lithium at room temperature or very little.

According to the lithium secondary battery manufacturing method according to an embodiment for achieving the above object of the present invention, first to form an electrode having an active material layer containing a transition metal alloy or a transition metal oxide. The electrode is electrochemically activated by charging or charging and discharging at a temperature of 50 to 200 ° C.

For example, the transition metal alloy may be represented by the following Chemical Formula 1, and the transition metal oxide may be represented by the following Chemical Formula 3.

<Formula 1>

A _x B _y (A is at least one selected from Si, Sn, Al, Ge, Ga, In, Sb, Pb, Bi, Mg and Zn, B is Cu, Ni, Co, Fe, Mn, Cr, At least one selected from V, Ti, Sc, Mo, Ru, and W, and 0 <x≤1, 0 <y≤1.)

<Formula 2>

GO _x (G comprises at least one selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W, Ru and Zr, where 0 <x≤3.)

For example, the electrode may be Si, Sn, Al, Ge, Ga on a current collector layer including at least one selected from Cu, Ni, Co, Fe, Mn, Cr, V, Ti, Sc, Mo, Ru, and W. , In, Sb, Pb, Bi, Mg and Zn may be formed by depositing and heating at least one material selected from. Alternatively, after the transition metal alloy or the transition metal oxide is prepared in powder form, a slurry containing a conductive material, a binder resin and a solvent is coated on a metal current collector to form a film, and then the film is dried to form a film. Can be.

A battery cell may be prepared to electrochemically activate the electrode. For example, the electrode is provided as a cathode, a cathode including an active material layer is provided, a separator including an electrolyte is provided between the cathode and the anode to form a battery cell, and then the battery cell is 50 to 200. It can charge and discharge at the temperature of ° C.

For example, the electrolyte may include an organic solvent and a lithium salt. Specifically, the lithium salt is LiBOB (lithium (bis) oxaloborate), LiB (C ₂ O ₄ ) ₂ ), LiBETI (lithium (bis) trifluoroethanesulfonimide), LiN (SO ₂ C ₂ F ₅ ) ₂ ), LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiSCN, LiC (CF ₃ SO ₂ ) _{3 And} the like, the organic solvent is ethylene carbonate (ethylene carbonate) , Propylene carbonate, diethylcarbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, gamma-butyrolactone (Γ-butyrolactone), tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,3-dioxolane, 4-methyl-1,3-dioxolane (4-methyl-1,3-dioxolane), diethylether, sulfolane, sulfoxide, polyethylene oxide, and the like.

The active material layer of the positive electrode may include a lithium compound represented by the following Chemical Formula 3, a lithium compound represented by the following Chemical Formula 4, and the like.

<Formula 3>

LiA _x B _y C (1-xy) O ₂ (A, B, C each comprise one selected from Cr, Mn, Fe, Co, and Ni, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1).

<Formula 4>

LiFe _x D (1-x) PO ₄ (D includes one selected from Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, wherein 0 ≦ x ≦ 1.)

In order to electrochemically activate the electrode, the battery cell may be charged at a temperature of 50 to 200 ° C., or the battery cell may be charged and discharged once at a temperature of 50 to 200 ° C. In particular, when the negative electrode includes a copper-indium alloy, the battery cell may be charged at a temperature of 50 to 200 ° C and then discharged at a temperature of 10 to 30 ° C.

According to the method of manufacturing a lithium secondary battery according to an embodiment of the present invention described above, a transition metal alloy or a transition metal oxide, which has not been active at room temperature in the past through high temperature activation, is converted to have activity at room temperature, and an electrode layer after activation. By dispersing the stress due to charging and discharging therein, the performance of the lithium secondary battery can be improved, and a lithium secondary battery capable of stably expressing a large capacity at room temperature or high temperature (50 to 200 ° C.) can be manufactured.

1 is a flowchart illustrating a method of manufacturing a lithium secondary battery according to an embodiment of the present invention. 2 is a cross-sectional view of a battery cell for electrochemically activating a negative electrode according to an embodiment of the present invention.

Referring to FIG. 1, an electrode is formed using a transition metal alloy or a transition metal oxide (S 100). The transition metal alloy includes an element that is reactive with lithium and an element that is not reactive with lithium, and specifically, may be represented by the following Chemical Formula 1.

<Formula 1>

A _x B _y

(A is an element capable of expressing capacity by alloying with lithium, and includes at least one selected from Si, Sn, Al, Ge, Ga, In, Sb, Pb, Bi, Mg, and Zn, and B is lithium As an inactive element, it contains at least one selected from Cu, Ni, Co, Fe, Mn, Cr, V, Ti, Sc, Mo, Ru, W, and 0 <x≤1, 0 <y≤1.)

The transition metal oxide may be represented by the following formula (2).

<Formula 2>

GO _x

(G includes at least one selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W, Ru, Zr, and 0 <x≤3.)

The transition metal alloy and the transition metal oxide may be crystalline or amorphous.

For example, the electrode may be formed of a current collector layer and an active material layer. For example, the electrode including the transition metal alloy may be formed using a deposition method. Specifically, a first thin film made of B material is prepared, and a second thin film made of A material is formed on the first thin film (S 110). The first thin film may be formed using a foil itself, or using a sputtering method, an electroplating method, or the like on a metal foil. The second thin film may be formed using a sputtering method, an electroplating method, or the like. For example, the thickness of the second thin film may be about 0.2 μm to about 50 μm.

Next, an alloy layer is formed by heating the first thin film and the second thin film at all times (S 120). The heating is preferably carried out in an inert gas atmosphere containing argon gas, helium gas and the like. The heating temperature may be about 200 to about 1000 ° C. The heating causes an alloying reaction at the interface between the first thin film and the second thin film to form an alloy layer. In the alloying reaction, the lower portion of the first thin film does not react and serves as a current collector layer. The total thickness of the electrode may be about 1 to about 500 ㎛, the thickness of the alloy layer increases as the thickness of the second thin film increases. As described above, when forming the alloy layer by deposition and heat treatment, it is possible to increase the energy density of the battery.

Alternatively, the electrode may be formed by applying a slurry containing a transition metal alloy powder on the current collector layer. Specifically, the A material and the B material are mixed to obtain a transition metal alloy powder of Chemical Formula 1 through high energy ball milling or heat treatment. The transition metal alloy powder is mixed with a binder resin, a conductive material and a solvent to prepare a slurry. For example, carbon black such as Super P may be used as the conductive material, and polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), Polyethylene (PE), polypropylene (PP), etc. can be used. These may each be used alone or in combination. As the solvent, an organic solvent such as N-methylpyrrolidone (NMP) or water may be used. The slurry may be coated on a metal current collector layer to form a film, and dried and rolled to form an electrode.

The electrode including the transition metal oxide may be formed by applying a slurry including the transition metal oxide powder on the current collector layer. Specifically, a slurry is prepared by mixing the transition metal oxide powder of Chemical Formula 2 with a binder resin, a conductive material, and a solvent. The binder resin, the conductive material and the solvent may be used the same as those mentioned above. The slurry may be coated on a metal current collector layer to form a film, and dried and rolled to form an electrode.

Next, the electrode is electrochemically activated at about 50 to about 200 ° C (S 200).

For example, a battery cell including the electrode may be manufactured to activate the electrode (S 210). Referring to FIG. 2, the lithium secondary battery 5 has a spiral cylindrical shape, a positive electrode 26 having a positive electrode current collector 25 disposed between two positive electrode active material layers 20, and a negative electrode current collector 15. ) Is a cylindrical structure in which a cathode 16 having two layers of negative electrode active material layer 10 positioned therebetween, and a laminate in which a thin film separator 30 is positioned between the center pin 7 are wound in multiple layers. Contains a sieve.

Insulation plates 13a and 13b are provided above and below the laminate, respectively, and the cylindrical laminate has a bottom portion formed at one end thereof and is housed in a hollow cylindrical mold anode terminal 28 having a hollow cylinder shape. . The positive electrode current collector 25 of the laminate penetrates through the insulating plate 13a and is connected to the positive electrode terminal 28 by the positive electrode lead 27. Further, a safety valve 31 having a convex shape (concave) in the insulating plate 13b direction on the insulating plate 13b on the opening side opposite to the bottom portion, and a convex shape in the opposite direction to the safety valve 31 (convex portion) The negative electrode terminal 18 of the cap type which has () is formed. The edge surfaces of the safety valve 31 and the negative electrode terminal 18 are sealed by the gasket 32 and are separated from the positive electrode terminal 28. The negative electrode current collector 15 of the laminate penetrates through the insulating plate 13b and is connected to the negative electrode terminal 18 by the negative electrode lead 17. The negative electrode current collector 15 and the positive electrode current collector 25 serve to extract the electromotive force generated by the movement of lithium ions.

The separator 30 serves to prevent a short circuit between the negative electrode 16 and the positive electrode 26, and also moves lithium ions between the positive electrode and the negative electrode, including the electrolyte solution. Preferably, the separator 30 is porous and has fine pores formed on its surface.

For example, the separator 30 may be a polymer mat, glass fiber mat, kraft paper, and the like. Specifically, Celgard series (product name, Hoechest Celanese Corp.) such as Celgard 2400, 2300, Ube Industries Ltd. . Or a polypropylene separator of Pall RAI may be used.

For example, the electrolyte of the separator 30 may include an organic solvent and a lithium salt. Examples of the lithium salt are LiBOB (lithium (bis) oxaloborate), LiB (C ₂ O ₄ ) ₂ ), LiBETI (lithium (bis) trifluoroethanesulfonimide), LiN (SO ₂ C ₂ F ₅ ) ₂ ), LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiSCN, and LiC (CF ₃ SO ₂ ) ₃ , and the like, may be used alone or in combination. Examples of the organic solvent include ethylene carbonate, propylene carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane ( 1,2-diethoxyethane), gamma-butyrolactone, tetrahydrofuran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane ), 4-methyl-1,3-dioxolane (4-methyl-1,3-dioxolane), diethylether (diethylether), sulfolane (sulfolane), polyethylene oxide (polyethylene oxide) and the like, These may each be used alone or in combination. In addition, a solid electrolyte such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ may also be used.

The anode active material layer 10 includes a transition metal alloy of Formula 1 or a transition metal oxide of Formula 2 described above.

For example, the positive electrode active material layer 20 includes LiA _x B _y C (1-xy) O ₂ (A, B, C each selected from Cr, Mn, Fe, Co, and Ni, and 0≤ x ≦ 1, 0 ≦ y ≦ 1), LiFe _x D (1-x) PO ₄ (D includes one selected from Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, and 0 ≦ x ≦ 1.), and specifically, LiFePO ₄ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , and the like. When the lithium secondary battery including the negative electrode active material layer 10 is used at a high temperature, for example, about 85 to about 150 ° C., the positive electrode active material layer 20 uses LiFePO ₄ to minimize performance degradation due to side reactions. It is preferable to include.

Alternatively, the battery cell may be a square or coin-shaped battery cell that is not spiral cylindrical.

When the battery cell is completed, the battery cell is charged at about 50 to about 200 ° C. to electrically activate the negative electrode (S 220).

When the negative electrode includes a transition metal alloy, the following reaction may theoretically occur during charging and discharging of a battery cell.

_{(a) A v B w +} Li + + e - → LiA v + wB: Charge

^{_{(b) LiA v → Li +}} + e - + vA: Discharge

(c) vA + wB → (vr) A + (ws) B + A _r B _s : spontaneous alloying reaction of A and B

(0 <r≤v, 0 <s≤w)

As the A material alloys with lithium through the charging process, element B is precipitated, and lithium is released through the discharge process, and A material is precipitated. The B material deposited during the charging process and the A material precipitated during the discharge process spontaneously alloy. At this time, the degree of spontaneous alloying reaction between A and B materials is influenced by the affinity according to the species of A and B, the size of precipitated particles and the temperature condition during discharge, and unreacted A and B materials may remain. .

The charging reaction is a thermodynamic spontaneous reaction, but this reaction does not easily occur at room temperature. It is believed that the chemical bonds of A and B must be broken in order for Li to react during the charging reaction, and the activation energy for breaking the chemical bonds of A and B is considered to be due to kinetic reasons that greatly inhibit the charging reaction rate.

When the negative electrode contains a transition metal oxide, the following reaction may theoretically occur during charging and discharging of a battery cell.

(d) _t + MO qLi ⁺ + qe ^- → Li MO _{q t:} insertion (addition) reaction

(e) _t + MO + + 2tLi 2te ^- → O ₂ + M tLi: conversion (conversion) reaction

The transition metal oxide may undergo an insertion reaction in which a three-phase Li-M-O is formed by reacting with lithium and a conversion reaction in which lithium oxide is formed by breaking a chemical bond of M-O.

The insertion reaction and the conversion reaction are thermodynamic spontaneous reactions, but such reactions do not easily occur at room temperature due to crystal structure, transition metal-oxygen bond strength, and the like.

In the method for manufacturing a lithium secondary battery according to an embodiment of the present invention, the negative electrode may have activity even at room temperature by electrochemically activating a negative electrode including a transition metal alloy or a transition metal oxide at a high temperature. Such high temperature electrochemical activation can improve the degree of spontaneous alloying reaction of the transition metal alloy, the crystallinity of the active material layer, the area of the interface between the active material layer and the electrolyte, and the like.

For example, high temperature electrochemical activation of a cathode comprising a transition metal alloy results in the formation of a nanocomposite with a uniform mixture of A, B or AB alloy particles of several to tens of nanometers in size. Excellent battery characteristics can be obtained compared with the use, and nanocomposites of these particles can be obtained without a complicated chemical synthesis method.

For example, as compared with the case of using Si having electrical conductivity close to the insulator alone, when the cathode including the Cu-Si alloy is activated at high temperature, not only is it active at room temperature, but also the conductivity characteristics are improved. Electrical short circuit between particles can be prevented. This is because Cu or Cu ₃ Si particles having a relatively high electrical conductivity maintain the electrical connection in the active material and suppress the stress due to the volume expansion of Si.

As another example, charging a negative electrode containing crystalline MoO ₂ becomes an amorphous state in which nano-sized Li ₂ O and Mo particles are uniformly mixed and maintains an amorphous state different from the initial state even after discharging it. This amorphous structure can improve the cycle performance of the electrode by dispersing the stress generated during the repeated insertion / desorption reaction with lithium and increases the activity of the electrode. As a result, when a lithium secondary battery using crystalline MoO ₂ as a negative electrode is electrochemically activated at high temperature and used at room temperature, high capacity can be stably expressed.

Preferably, the negative electrode may be charged at a high temperature of about 50 to about 200 ℃, and then discharged at the same high temperature. However, the method of electrochemically activating the cathode at high temperature is not limited to the above hot charging / high temperature discharge method.

For example, when the negative electrode comprises a copper-indium alloy, it is preferable to charge the negative electrode at about 50 to about 200 ° C. and then discharge it at a temperature of about 10 to about 30 ° C.

The temperature, voltage range, current magnitude, charge / discharge method, and the like of the charge and discharge may be appropriately adjusted according to the composition of each cathode and the characteristics of the constituent elements. At this time, the state of charge (SOC), the current, the charge and discharge method (constant current charge and discharge, constant current / voltage charge and discharge, pulse charge and discharge) and the like can be adjusted by adjusting the cut-off voltage of the charge or discharge.

In consideration of process efficiency and the like, the high temperature electrochemical activation step is preferably performed after manufacturing a commercial battery cell using the negative electrode including the transition metal alloy or the transition metal oxide, but using a temporary battery cell After a chemical activation step, it may be provided to manufacture a commercial battery cell.

The negative electrode of a lithium secondary battery manufactured according to an embodiment of the present invention may express a larger capacity when operating at a high temperature of about 85 to about 150 ° C. as compared to when operating at room temperature. In this case, in order to minimize performance degradation due to side reactions, the cathode active material layer may include LiFePO ₄ and the electrolyte may be a polymer electrolyte including polyethylene oxide.

Hereinafter, a method of manufacturing a lithium secondary battery according to an embodiment of the present invention will be described in detail with reference to specific examples and experimental examples.

Example 1

A silicon film was formed by depositing silicon on a copper foil having a thickness of about 25 μm using a DC sputtering method at a power of about 2 kW (500 V, 4 A). The copper thin film and the silicon thin film were heat-treated for about 15 hours while heating up from about room temperature to about 500 ° C. at a rate of about 1 ° C./min in an argon gas atmosphere to prepare an electrode having an alloy layer of Cu ₃ Si. The thickness of the electrode was about 50 μm.

Example 2

Copper and silicon powder are mixed in a molar ratio of 3: 1, mixed with a steel sphere with a diameter of about 5 mm and a weight ratio of 1:10, and then a high energy ball-mill is operated for 12 hours in an inert atmosphere of argon gas. Was carried out to obtain powder. Cu ₃ Si powder was prepared by heat treating the powder for about 15 hours while raising the temperature from room temperature to about 500 ° C. at a rate of about 1 ° C./min in an inert atmosphere of argon gas.

The Cu ₃ Si powder, super P and PVdF were mixed at a weight ratio of about 70:15:15, and the slurry dissolved in NMP solvent was applied to a uniform thickness on a copper thin film having a thickness of about 25 μm using a doctor blade method. dried, and rolled at about 120 ℃ to manufacture an electrode comprising an alloy layer of Cu ₃ Si. The thickness of the electrode was about 50 μm.

Example 3

A tin film was formed by depositing tin on a copper thin film having a thickness of about 25 μm using a DC sputtering method at a power of about 1 kW (400 V, 2.5 A). The copper thin film and tin thin film were heat-treated in a vacuum oven at about 300 ° C. for about 30 hours to prepare an electrode having an alloy layer of Cu ₃ Sn. The thickness of the electrode was about 50 μm.

Example 4

MoO ₂ powder (Aldrich, USA), super P and PVdF were mixed in a weight ratio of about 70:20:10, and the slurry dissolved in NMP solvent was uniformly deposited using a doctor blade method on a copper thin film having a thickness of about 25 μm. After coating, it was dried at about 120 ° C. and rolled to prepare an electrode having an active material layer of MoO ₂ . The thickness of the electrode was about 50 μm.

3 is a graph showing charge and discharge behavior at room temperature of a half cell battery manufactured using the electrode of Example 1. FIG. Specifically, the electrode of Example 1 was dried in a vacuum oven at about 120 ° C for about 12 hours. A membrane of about 150 μm thick (glass fiber filter paper, Toyo Roshi Kaisha. Ltd., Japan) containing about 500 μm thick lithium thin film and a LiBOB / PC electrolyte at a concentration of about 1 M was used as a counter electrode. A coin-shaped battery cell (diameter: about 20 mm, thickness: about 3.2 mm) was manufactured using the same. The battery cell was charged and discharged once at a constant current method at a current density of about 500 mA / g _Si at a voltage range of 0-2 V (vs. Li / Li ⁺ ) at about 85 ° C. Thereafter, the battery was charged and discharged at a current density of about 500 mA / g _Si at a voltage range of 0-2 V (vs. Li / Li ⁺ ) at room temperature (about 25 ° C.).

Referring to FIG. 3, it can be seen that a half cell battery including an electrode having an alloy layer of Cu ₃ Si may express high capacity even at room temperature through an electrochemical activation at a high temperature (single-discharge at high temperature). have.

4 is a graph showing charge and discharge behaviors at high temperature and room temperature of a half cell battery manufactured using the electrode of Example 3. FIG. Specifically, the electrode of Example 3 was dried in a vacuum oven at about 120 ° C. for about 12 hours. A membrane of about 150 μm thick glass fiber filter paper (Toyo Roshi Kaisha. Ltd., Japan) containing about 500 μm thick lithium thin film and a LiBETI / PC electrolyte at a concentration of about 1 M was used as a counter electrode. Two coin-shaped battery cells (diameter: about 20 mm, thickness: about 3.2 mm) were prepared. One of the battery cells was charged and discharged according to the constant current method at a current density of about 100 mA / g _Sn at a voltage range of 0-2 V (vs. Li / Li ⁺ ) at about 120 ° C., and the other was at room temperature (about 25 ° C) was charged and discharged according to the constant current method at a current density of about 100 mA / g _Sn in the voltage range of 0-2 V (vs. Li / Li ⁺ ). 4 shows the charge and discharge behavior of the battery cells charged and discharged at room temperature, and the bottom shows the charge and discharge behavior of the battery cells charged and discharged at about 120 ° C.

FIG. 5 is a graph showing charge and discharge capacity at room temperature of a half cell battery manufactured using the electrode of Example 3 of FIG. 4. The battery cell was activated by charging and discharging once according to a constant current method at a current density of about 100 mA / g _Sn at a voltage range of 0-2 V (vs. Li / Li ⁺ ) at about 120 ° C. Figure 5 shows the charge and discharge characteristics at room temperature (about 25 ℃) after activation by the above method, the charge and discharge conditions are the same as the high temperature activation conditions.

4 and 5, the half-cell battery including the electrode having an alloy layer of Cu ₃ Sn has almost no capacity at room temperature, but through electrochemical activation at high temperature (one time charge and discharge at high temperature). It can be seen that a large dose can be stably expressed even at room temperature operation, and can be expressed at about twice as large as a room temperature operation even when operated at high temperature after activation.

6 is a graph showing charge and discharge behaviors at high and normal temperatures of a half cell battery manufactured using the electrode of Example 4. FIG. Specifically, the electrode of Example 4 was dried in a vacuum oven at about 120 ° C. for about 12 hours. About 150 μm thick glass fiber sheet using about 500 μm thick lithium thin film as counter electrode and containing about 1 M LiPF ₆ / EC + DEC (volume ratio of EC and DEC is about 1: 1) electrolyte A coin-shaped battery cell (diameter: about 20 mm, thickness: about 3.2 mm) was prepared using fiber filter paper, Toyo Roshi Kaisha. Ltd., Japan, as a separator. The battery cell was charged and discharged according to the constant current method at a current density of about 100 mA / g at a voltage range of 0.1-3 V (vs. Li / Li ⁺ ) at room temperature (about 25 ° C.). In addition, a glass fiber sheet having a thickness of about 150 μm using a lithium thin film having a thickness of about 500 μm as the counter electrode and including an electrolyte of about 1 M in concentration of LiBOB / EC + DMC (volume ratio of EC and DMC is about 1: 1) ( A coin-shaped battery cell (diameter: about 20 mm, thickness: about 3.2 mm) was prepared using glass fiber filter paper, Toyo Roshi Kaisha. Ltd., Japan, as a separator. The battery cell was charged and discharged according to the constant current method at a current density of about 100 mA / g at a voltage range of about 0.1-3 V (vs. Li / Li ⁺ ) at about 120 ° C.

FIG. 7 is a graph showing charge and discharge capacity at room temperature of a half cell battery manufactured using the electrode of Example 4 of FIG. 6. The battery cell is charged once (after activation) at a current density of about 100 mA / g at a voltage range of about 0.1-3 V (vs. Li / Li ⁺ ) at about 120 ° C. (after activation), and then at room temperature ( About 25 ° C.) in the same manner. Charge and discharge after 2 times were performed at room temperature.

Referring to FIGS. 6 and 7, the half cell battery including the electrode having the active material layer of MoO ₂ exhibited a small capacity at low temperature, but was operated at room temperature through a process of electrochemical activation at high temperature (single-discharge at high temperature). It can be seen that a large dose can be expressed, and that when operated at high temperature, a larger dose can be expressed compared to room temperature operation.

8 is a graph showing charge and discharge behavior at high temperatures of a full cell battery manufactured using the electrode of Example 1. FIG. Specifically, the electrode of Example 1 was dried in a vacuum oven at about 120 ° C for about 12 hours. LiFePO ₄ , super P and PVdF were mixed at a weight ratio of about 8: 1: 1, and the slurry dissolved in NMP solvent was applied to a uniform thickness on the Al foil having a thickness of about 20 μm using a doctor blade method, and then about 120 It was dried at 占 폚 and rolled to prepare an electrode of about 50 μm thick with an active material layer of LiFePO ₄ . The electrode was used as an anode, the electrode of Example 1 was used as a cathode, and a coin-shaped coin was made using a polymer electrolyte having a thickness of about 150 μm in which LiBOB was dispersed in polyethylene oxide (molecular weight of about 400,000) at a molar ratio of 20: 1. Battery cells (diameter: about 20 mm, thickness: about 3.2 mm) were prepared. The battery cells were charged and discharged at a rate of 0.5 C-rate at a potential of 2-4 V at about 100 ° C.

Referring to FIG. 8, it can be seen that a full cell battery including an electrode having an alloy layer of Cu ₃ Si may express high capacity at a high temperature through an electrochemical activation at a high temperature (single-discharge at high temperature). have. Specifically, after expressing the highest dose in the electrochemical activation process, it stably expressed a high dose in subsequent charge and discharge.

According to the method of manufacturing a lithium secondary battery according to an embodiment of the present invention described above, by reacting lithium at room temperature by electrochemically activating a transition metal alloy or a transition metal oxide, which has not been previously active at room temperature, It can switch to a negative electrode active material. In addition, the transition metal alloy or transition metal oxide may improve the performance of the lithium secondary battery by maintaining the electrical connection of the active material particles, dispersing the stress caused by the charge and discharge. In addition, by stably expressing a large capacity at room temperature or high temperature, it is possible to exhibit excellent performance in the field requiring a large capacity in a high temperature environment, such as automobiles.

As described above with reference to the preferred embodiment of the present invention, those skilled in the art without departing from the spirit and scope of the present invention described in the claims below various modifications and It will be appreciated that it can be changed.

1 is a flowchart illustrating a method of manufacturing a lithium secondary battery according to an embodiment of the present invention.

2 is a cross-sectional view of a battery cell for electrochemically activating a negative electrode according to an embodiment of the present invention.

3 is a graph showing the relationship between the potential and the capacity in the activation (single charge and discharge) step at high temperature and the charge and discharge step at room temperature of the half cell battery manufactured using the electrode of Example 1. FIG.

4 is a graph showing charge and discharge behavior at room temperature and high temperature of a half cell battery manufactured using the electrode of Example 3. FIG.

5 is a graph showing charge and discharge capacity at room temperature after high temperature activation of a half cell battery manufactured using the electrode of Example 3 of FIG. 4.

6 is a graph showing charge and discharge behavior at room temperature and high temperature of a half cell battery manufactured using the electrode of Example 4. FIG.

FIG. 7 illustrates the relationship between the potential and capacity according to activation (single charge) at high temperature, discharge at room temperature, and subsequent charge and discharge at room temperature of a half cell battery manufactured using the electrode of Example 4 of FIG. 6. It is a graph.

8 is a graph showing charge and discharge behavior at high temperatures of a full cell battery manufactured using the electrode of Example 1. FIG.

Claims (9)

Forming an electrode having an active material layer comprising a transition metal alloy or a transition metal oxide; And The method of manufacturing a lithium secondary battery comprising the step of electrochemical activation by charging or charging and discharging the electrode at a temperature of 50 to 200 ℃. The method of claim 1, wherein the transition metal alloy is represented by the following Chemical Formula 1. <Formula 1> A _x B _y (A is at least one selected from Si, Sn, Al, Ge, Ga, In, Sb, Pb, Bi, Mg and Zn, B is Cu, Ni, Co, Fe, Mn, Cr, At least one selected from V, Ti, Sc, Mo, Ru, and W, and 0 <x≤1, 0 <y≤1.) The method of claim 1, wherein the transition metal oxide is represented by the following Chemical Formula 2. <Formula 2> GO _x (G comprises at least one selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W, Ru and Zr, where 0 <x≤3.) According to claim 2, The electrode is Si, Sn, Al, Ge on the current collector layer containing at least one selected from Cu, Ni, Co, Fe, Mn, Cr, V, Ti, Sc, Mo, Ru and W Method for manufacturing a lithium secondary battery, characterized in that formed by depositing and heating at least one material selected from Ga, In, Sb, Pb, Bi, Mg and Zn. The method of claim 1, wherein the forming of the electrode comprises: Preparing a slurry including the transition metal alloy or transition metal oxide, a conductive material, a binder resin, and a solvent; Applying the slurry onto a metal current collector to form a film; And Method for producing a lithium secondary battery comprising the step of drying the film. The method of claim 1, wherein electrochemically activating the electrode comprises: Providing the electrode as a cathode; Providing a positive electrode comprising an active material layer; Forming a battery cell by providing a separator including an electrolyte between the negative electrode and the positive electrode; And Method for manufacturing a lithium secondary battery comprising the step of charging or charging and discharging the battery cell at a temperature of 50 to 200 ℃. The method of claim 6, wherein the electrolyte comprises an organic solvent and a lithium salt, wherein the lithium salt is liBOB (lithium (bis) oxaloborate), LiB (C ₂ O ₄ ) ₂ ), LiBETI (lithium (bis) trifluoroethanesulfonimide), LiN (SO ₂ C ₂ F ₅ ) ₂ ), LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiSCN and LiC (CF ₃ SO ₂ ) ₃ At least one selected from the group, wherein the organic solvent is ethylene carbonate (propylene carbonate), propylene carbonate (propylene carbonate), diethyl carbonate (diethylcarbonate), 1,2-dimethoxyethane, 1 1,2-diethoxyethane, gamma-butyrolactone, tetrahydrofuran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxo Lan (1,3-dioxolane), 4-methyl-1,3-dioxolane (4-methyl-1,3-dioxolane), diethylether, sulfolane and polyethylene oxide ) Method for manufacturing a lithium secondary battery characterized in that it comprises at least one selected from the group consisting of. The method of claim 6, wherein the active material layer of the positive electrode comprises at least one selected from a lithium compound represented by Formula 3 below and a lithium compound represented by Formula 4 below. <Formula 3> LiA _x B _y C (1-xy) O ₂ (A, B, C each comprise one selected from Cr, Mn, Fe, Co, and Ni, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1). <Formula 4> LiFe _x D (1-x) PO ₄ (D includes one selected from Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, wherein 0 ≦ x ≦ 1.) The method of claim 6, wherein the negative electrode comprises a copper-indium alloy, and electrochemically activating the electrode is charged to the battery cell at a temperature of 50 to 200 ℃, and then discharged at a temperature of 10 to 30 ℃ Method of manufacturing a lithium secondary battery comprising the step.

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