KR100582558B1 - Lithium metal anode for lithium metal polymer secondary battery comprising spacer and method for forming the same - Google Patents

Abstract

Disclosed are a lithium metal negative electrode for a lithium metal polymer secondary battery having a spacer and a method of manufacturing the same. The lithium metal negative electrode according to the present invention includes a metal current collector, a lithium film formed by being separated into a plurality of areas on the metal current collector, and a grid-shaped spacer defining each area of the lithium film. By inserting a spacer thicker than the lithium film in the lithium film, a problem of volume change due to a change in thickness of the negative electrode due to dendritic growth occurring during charging and discharging may be minimized.

Lithium metal polymer secondary battery, lithium metal anode, spacer, grid, cycle stability

Description

Lithium metal anode for lithium metal polymer secondary battery with spacer and manufacturing method therefor {Lithium metal anode for lithium metal polymer secondary battery comprising spacer and method for forming the same}

1A is a plan view of a lithium metal negative electrode for a lithium metal polymer secondary battery according to a first exemplary embodiment of the present invention.

FIG. 1B is a cross-sectional view taken along the line Ib-Ib 'of FIG. 1A.

2 is a plan view of a lithium metal negative electrode for a lithium metal polymer secondary battery according to a second exemplary embodiment of the present invention.

3A to 3C are cross-sectional views illustrating a manufacturing method of a lithium metal negative electrode for a lithium metal polymer secondary battery according to a preferred embodiment of the present invention.

Figure 4 is a graph showing the cycle performance of the unit cells made of a lithium metal negative electrode according to the present invention with a comparative example.

5 is a graph showing the change in cell thickness as the number of cycles increases in the unit cells obtained from the lithium metal negative electrode according to the present invention together with the case of the comparative example.

<Explanation of symbols for the main parts of the drawings>

10: lithium metal negative electrode, 12: metal current collector, 12a: top surface, 14: lithium film, 14a: top surface, 16: spacer, 16a: top surface, 17: opening, 20: lithium metal negative electrode, 26: spacer, 27: opening .

The present invention relates to a lithium metal polymer secondary battery and a method of manufacturing the same, and more particularly, to a lithium metal negative electrode for a lithium metal polymer secondary battery provided with a spacer and a method of manufacturing the same.

In recent years, as the IT (Information Technology) industry is advanced, miniaturization, thinning, and weight reduction of electronic devices are rapidly made. In particular, one of the notable changes in the trend of technology is that in the field of office automation, desktop computers are rapidly reduced in size and size to portable notebook PCs or smaller, and portable electronic devices such as cellular phones are increasingly being used. As functions diversify, the company continues to pursue miniaturization.

Accordingly, high performance is also required for lithium secondary batteries that supply power thereto. One of the most widely used lithium secondary batteries installed in small IT devices is a lithium ion battery (LIB). This is because small size and light weight are advantageous and energy density is higher than conventional lead acid batteries or nickel-cadmium batteries.

Lithium ion batteries use a carbon-based material as a negative electrode whose chemical potential is almost similar to that of metallic lithium upon insertion / desorption of lithium ions. As the positive electrode material, a transition metal oxide such as lithium cobalt oxide (LiCoO ₂ ) exhibiting a potential of about 3 to 4.5 V higher than that of lithium is used. And a liquid electrolyte / membrane system is used as the electrolyte.

However, conventional lithium ion batteries have been restricted in design to prevent leakage of liquid electrolyte, and due to the fundamental limitations of materials, performance has been judged to have reached a saturation state. Even in the process, there is a problem that the manufacturing cost is expensive and difficult to large-capacity.

One of the efforts to overcome the problems of the existing lithium secondary battery and upgrade the performance is the lithium metal polymer battery (LMPB). Lithium metal polymer secondary battery uses lithium metal as a negative electrode instead of a carbon-based negative electrode in the configuration, and uses a new transition metal oxide material having improved capacity than a conventional positive electrode. In particular, by using a polymer electrolyte instead of a conventional liquid electrolyte / membrane system, it has improved stability compared to a lithium ion battery, and various designs and enlargement are facilitated.

However, despite being spotlighted as next generation power devices, lithium metal polymer secondary batteries still have many problems to be improved in cycle characteristics and life characteristics. During charging, short-circuit problems occur due to lithium dendrite growth on the surface of the lithium negative electrode, and irreversible reaction is intensified, thereby degrading cycle performance. In addition, lithium lumps or particles that fall off the surface of the cathode during discharge have a serious impact on stability. Finally, as the lithium resin phase is formed, the thickness change of the lithium negative electrode is generated, and thus, the expansion, contraction, or deformation of the cell is generated, thereby seriously affecting the stability and life characteristics of the battery.

In an effort to solve the above problems, research has been conducted to suppress lithium dendritic formation and prevent direct contact with the electrolyte through surface modification of the lithium anode (for example, US Pat. No. 5,314,765, 6,432,584 B1). These attempts and improvements have led to some improvement in lithium dendritic formation. However, as long as the possibility of forming the lithium resin phase could not be eliminated fundamentally, it was not possible to fundamentally control the volumetric deformation caused by the volume expansion and contraction of the cell caused by the change of the thickness of the cathode during charge and discharge. In particular, the larger the capacity and area of the cell, the more serious this problem becomes.

An object of the present invention is to solve the problems in the prior art as described above, it is possible to solve the volume deformation phenomenon of the cell due to the change in thickness of the lithium negative electrode generated during the charge and discharge in the prior art, and the stability of the cell And to provide a lithium metal negative electrode for a lithium metal polymer secondary battery having a structure capable of improving the cycle life characteristics.

Another object of the present invention is to fundamentally solve the volume deformation of the cell according to the thickness change of the lithium anode by a simplified manufacturing process, lithium lithium polymer secondary battery that can improve the stability and cycle life characteristics of the cell It is to provide a method for producing a metal cathode.

In order to achieve the above object, a lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention is a metal current collector, a lithium film formed by separating a plurality of areas on the metal current collector, and to define each region of the lithium film Grid-shaped spacers.

The metal current collector may be formed of a foil, a mesh, or a foam.

Each of the lithium film and the spacer is formed to be in contact with an upper surface of the metal current collector, and is formed from an upper surface of the metal current collector to an upper surface of the spacer rather than a thickness from an upper surface of the metal current collector to an upper surface of the lithium film. Larger thickness

The spacers are formed with a plurality of openings corresponding to respective regions of the lithium film, and the openings have a polygonal, circular or elliptical shape.

In order to achieve the above another object, in the method of manufacturing a lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention, a metal current collector is prepared first. A lithium film is formed on the metal current collector. A spacer having a thickness thicker than the lithium film is inserted into the lithium film. In order to form the lithium film, a film-shaped lithium is laminated on the metal current collector.

In order to insert the spacer, the spacer may be placed on the lithium film, followed by lamination and pressing.

The lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention is obtained by placing a grid-type spacer film of an insulating material thicker than a lithium film on a lithium layer and inserting the same into a lithium film through lamination / pressing. Since the thickness of the spacer is thicker than the thickness of the lithium film, a large amount of the dendritic particles may be prevented from penetrating and growing into the polymer electrolyte or the separator, causing short circuit or peeling of the electrode surface from the cathode. Therefore, volume expansion and contraction of the battery cell due to the thickness change of the lithium negative electrode are suppressed, and cycle stability and life characteristics are improved.

Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1A is a plan view of a lithium metal negative electrode for a lithium metal polymer secondary battery according to a first exemplary embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line Ib-Ib 'of FIG. 1A.

1A and 1B, a lithium metal negative electrode 10 for a lithium metal polymer secondary battery according to the present invention is a metal current collector 12 and a lithium film formed by being separated into a plurality of regions on the metal current collector 12. 14 and a grid-shaped spacer 16 defining each region of the lithium film 14.

The spacer 16 is formed to contact the metal current collector 12, and has a thickness T ₁ from the top surface 12a of the metal current collector 12 to the top surface 14a of the lithium film 14. The thickness T ₂ from the upper surface 12a of the metal current collector 12 to the upper surface 16a of the spacer 16 is greater than).

The metal current collector 12 may be formed by a rolling method or an electrolytic method, and may be made of metal in a film or mesh form. Alternatively, the metal current collector 12 may be made of a metal having a foam shape. The metal current collector 12 may be made of copper or nickel, for example. The thickness T ₃ of the metal current collector 12 may be about 5 to 50 μm.

The lithium film 14 may be formed on the metal current collector 12 by lamination or direct deposition. The thickness T ₂ of the lithium film 14 may be about 0.5 to 100 μm.

The grid-shaped spacer 16 may be made of glass reinforced fiber, carbon fiber, or aluminum oxide, and the spacer 16 has a plurality of openings 17 corresponding to respective regions of the lithium film 14. It is. Each opening formed in the spacer 16 may have various shapes such as polygon, circle, oval. 1A and 1B illustrate a spacer 16 having a rectangular opening 17.

2 illustrates a lithium metal negative electrode 20 for a lithium metal polymer secondary battery having a spacer 26 having a circular opening 27. In Fig. 2, the same reference numerals as in Figs. 1A and 1B denote the same members.

In the case of the rectangular opening 17 as in FIGS. 1A and 1B, the horizontal and vertical dimensions of the opening 17 may be about 100 μm to 1 cm, respectively. In addition, in the case of the circular opening 27, as shown in FIG. 2, the opening 27 may have a diameter of about 100 μm to 1 cm. The thickness T ₂ of the spacer 16 may be about 1 to 200 μm.

As described above, in the lithium metal negative electrode according to the present invention, the thickness of the spacer is thicker than the thickness of the lithium film constituting the lithium metal negative electrode. Therefore, when lithium ions exiting the anode during charging are reduced on the surface of the cathode, no matter how much lithium resin is grown in the direction of the anode, the thickness does not increase while penetrating or pushing the polymer electrolyte or the separator. This is because even if the thickness of the lithium anode itself grows, a change is caused only within the thickness of the spacer film. Therefore, the phenomenon in which the thickness and volume of the battery cell are deformed can be effectively suppressed. In addition, as the resin phase penetrates and grows toward the polymer electrolyte or the separator, the peeling phenomenon occurs on the surface of the negative electrode. In addition, even though the morphology of the cathode surface changes from time to time, since the direct contact with lithium at the interface with the electrolyte film is suppressed, it hardly affects the increase in the interface resistance. Therefore, the short circuit phenomenon of a battery can be suppressed and a cycle stability can also be improved significantly.

In addition, the lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention may be applied to a conventional liquid electrolyte / membrane system, and its manufacturing process is simple and easy.

3A to 3C are cross-sectional views of a lithium metal polymer according to a preferred embodiment of the present invention in order to explain a method of manufacturing a lithium metal negative electrode for a secondary battery.

Referring to FIG. 3A, first, a metal current collector 12 made of a metal, for example, copper or nickel, is prepared. The metal current collector 12 may be made of a metal foil or a metal mesh, or a metal foam manufactured by rolling or electrolysis. For example, the metal current collector 12 may be made of copper or nickel.

Referring to FIG. 3B, a lithium film 14 is formed on the metal current collector 12. The lithium film 14 may be formed by laminating film-shaped lithium on the metal current collector 12 or by directly depositing lithium on the metal current collector 12.

Referring to FIG. 3C, a grid-shaped spacer 16 made of an insulator is placed on a lithium film 14 formed on the metal current collector 12, and then, in the lithium film 14 by lamination and pressing processes. The spacer 16 is inserted to complete a lithium metal negative electrode for a lithium metal polymer secondary battery as illustrated in FIGS. 1A and 1B. Detailed configurations of the lithium film 14 and the spacer 16 have been described with reference to FIGS. 1A, 1B, and 2.

Hereinafter, a method of manufacturing a lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention will be described in more detail with reference to specific examples. However, the specific examples described below are merely examples to help understanding of the present invention, and the scope of the present invention should not be construed as being limited thereto.

Example 1

After attaching a nickel tab terminal to a copper current collector having a thickness of 15 μm and a size of 2 cm × 2 cm with an ultrasonic welding machine, lithium was sputtered onto the film to produce a lithium film. The spacer film made of glass reinforcing fibers was placed on the obtained lithium film and pressed to prepare a lithium metal negative electrode having a lower end portion of the spacer film inserted into the lithium film. Here, the spacer film had a size of 2 mm × 2 mm and a thickness of 25 μm of one opening constituting the grid. At this time, since the thickness of the spacer film is thicker than that of the lithium film, the upper portion of the spacer film protrudes out from the lithium film, and the thickness of the upper portion of the spacer film protruding from the lithium film was 15 μm.

Example 2

A lithium metal negative electrode was manufactured in the same manner as in Example 1, except that a spacer film prepared using a carbon fiber material was used.

Example 3

A lithium metal negative electrode was prepared in the same manner as in Example 1, except that a spacer film having a circular grid made of aluminum oxide was used.

Example 4

For charge and discharge cycle measurements, unit cells were manufactured using the lithium metal negative electrodes prepared in Examples 1 and 3. At this time, 80% by weight of lithium-manganese-nickel oxide powder, 12% by weight of a conductive agent, and 8% by weight of a binder were used as a positive electrode plate, and an electrolyte was used as a separator / liquid electrolyte system. As a comparative example, a unit cell in which no spacer was placed on the surface of a lithium metal negative electrode was also prepared and measured under the same conditions. Charge and discharge characteristics were investigated while charging and discharging the current density to 4.8V at 1 mA (C / 5 rate) and discharging to 3.0V. In addition, cycle stability up to 50 cycles was measured.

4 is a graph showing the cycle performance of the unit cells made of the lithium metal negative electrodes of Examples 1 and 3 together with the case of the comparative example. In the case of Example 1 and Example 3 using the lithium metal negative electrode according to the present invention it can be seen that the retention characteristics of the discharge capacity according to the cycle is superior to that of the comparative example.

FIG. 5 is a graph showing a change in cell thickness as the number of cycles increases in unit cells obtained from lithium metal negative electrodes according to Examples 1 and 3, together with a comparative example. In the case of Examples 1 and 3, there is almost no change in the cell thickness compared to the case of the comparative example, it can be seen that the problem of the volume change of the cell according to the thickness change of the lithium anode is improved.

The lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention is obtained by placing a grid-type spacer film of an insulating material thicker than a lithium film on a lithium layer and inserting the same into a lithium film through lamination / pressing. Since the thickness of the spacer is thicker than the thickness of the lithium film, a large amount of the dendritic particles may be prevented from penetrating and growing into the polymer electrolyte or the separator, causing short circuit or peeling of the electrode surface from the cathode. In addition, since the thickness and volume of lithium expand and contract only within the spacer film thickness range, they do not fundamentally change the battery cell thickness. In addition, although the morphology of the negative electrode surface changes from time to time, there is no direct contact with lithium at the interface with the electrolyte film and thus does not cause an increase in the interface resistance. Thus, cycle stability and lifespan characteristics can be improved.

Lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention is applicable to ultra-thin lithium anode to thick film form, and from small unit cells to large stack / winding cell. In addition, the manufacturing method of the lithium metal negative electrode for a lithium metal polymer secondary battery according to the present invention can be easily applied without changing the existing process so that the process is simple and easy.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes by those skilled in the art within the spirit and scope of the present invention. You can change it.

Claims (12)

Metal current collectors, A lithium film formed by being separated into a plurality of regions on the metal current collector; Lithium metal negative electrode for a lithium metal polymer secondary battery, characterized in that it comprises a grid-shaped spacer defining each region of the lithium film. The method of claim 1, The metal current collector is a lithium metal negative electrode for a lithium metal polymer secondary battery, characterized in that consisting of a foil (foil), a mesh (mesh), or a foam (foam). The method of claim 1, The metal current collector is lithium metal anode for lithium metal polymer secondary battery, characterized in that consisting of copper or nickel. The method of claim 1, The lithium film and the spacer is a lithium metal negative electrode for a lithium metal polymer secondary battery, characterized in that formed in contact with the upper surface of the metal current collector, respectively. The method of claim 4, wherein And a thickness from an upper surface of the metal current collector to an upper surface of the spacer is greater than a thickness from an upper surface of the metal current collector to an upper surface of the lithium film. The method of claim 4, wherein The thickness of the said lithium film is selected in the range of 0.5-100 micrometers, The thickness of the spacer is lithium metal anode for lithium metal polymer secondary battery, characterized in that selected in the range of 1 to 200㎛. The method of claim 1, The spacer is a lithium metal negative electrode for a lithium metal polymer secondary battery, characterized in that made of glass reinforced fiber, carbon fiber, or aluminum oxide. The method of claim 1, A plurality of openings corresponding to each region of the lithium film are formed in the spacer, and the openings have a polygonal, circular or elliptical shape. Preparing a metal current collector; Forming a lithium film on the metal current collector; Method of manufacturing a lithium metal negative electrode for a lithium metal polymer secondary battery comprising the step of inserting a spacer having a thickness thicker than the lithium film in the lithium film. The method of claim 9, Method of manufacturing a lithium metal negative electrode for a lithium metal polymer secondary battery, characterized in that for laminating the film-shaped lithium on the metal current collector to form the lithium film. The method of claim 9, Method for producing a lithium metal negative electrode for a lithium metal polymer secondary battery, characterized in that for depositing lithium directly on the metal current collector to form the lithium film. The method of claim 9, Method of manufacturing a lithium metal negative electrode for a lithium metal polymer secondary battery, characterized in that the lamination and pressing after the spacer on the lithium film to insert the spacer.

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