JP2018181982A - Electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device having excellent productivity and capable of making a pre-doped state of a negative electrode uniform. An electrochemical device according to the present invention comprises a first electrode unit, a second electrode unit, a third electrode unit, a first lithium ion supply source, a second lithium ion supply source, and an electrolytic solution. Equipped. The first lithium ion supply source includes a first current collector having a first main surface on the first electrode unit side and a second main surface on the third electrode unit side. The second lithium ion supply source includes a second current collector having a third main surface on the side of the second electrode unit and a fourth main surface on the side of the third electrode unit. A first metallic lithium is attached to the first main surface, and a second metallic lithium having a thickness smaller than that of the first metallic lithium is attached to the second main surface. A third metallic lithium is attached to the third main surface, and a fourth metallic lithium having a thickness smaller than that of the third metallic lithium is attached to the fourth main surface. [Selection diagram] Fig. 4

Description

  The present invention relates to an electrochemical device composed of a plurality of electrode units.

  Large-capacity capacitors are being used in fields that require repeated charging and discharging with large power, such as energy regeneration and load leveling. Conventionally, an electric double layer capacitor has been widely used as a large capacity capacitor, but in recent years, the use of a lithium ion capacitor having a high energy density has been studied.

  The lithium ion capacitor needs pre-doping in which lithium ions are doped in advance to the negative electrode. However, in order to use the lithium ion capacitor stably for a long time, it is important to make the pre-doped state of the negative electrode uniform.

  Here, pre-doping of lithium ions is performed by immersing metal lithium electrically connected to the negative electrode in an electrolytic solution. Since lithium ions move in the electrolytic solution and reach the negative electrode, the pre-doped state is affected by the positional relationship between the negative electrode and the lithium ion supply source.

  For example, Patent Document 1 discloses a configuration in which lithium ions are supplied to a negative electrode by arranging lithium ion sources on both sides of a plurality of electrode units constituting a cell.

WO 2006/112068

  However, in the configuration described in Patent Document 1, when the number of electrode units is two, the number of parts is large. Therefore, pre-doping can be advanced by arranging a lithium ion source between the electrode units. When the number of electrode units is three or more, the ratio of pre-doping in the electrode unit is changed, and the doping amount may be nonuniform. Furthermore, it is necessary to adjust the amount of lithium per terminal area of the electrode unit.

  In view of the circumstances as described above, it is an object of the present invention to provide an electrochemical device which is excellent in productivity and can make the pre-doped state of the negative electrode uniform.

In order to achieve the above object, an electrochemical device according to an aspect of the present invention comprises a first electrode unit, a second electrode unit, a third electrode unit, a first lithium ion source, And a lithium ion source and an electrolyte solution.
In the first electrode unit, positive electrodes and negative electrodes are alternately stacked via a separator.
In the second electrode unit, the positive electrode and the negative electrode are alternately stacked via a separator.
The third electrode unit has a positive electrode and a negative electrode alternately stacked via a separator, and is positioned between the first electrode unit and the second electrode unit.
The first lithium ion source is disposed between the first electrode unit and the third electrode unit, and the first main surface on the first electrode unit side and the third electrode unit A first current collector is provided which is a metal foil having a side second main surface.
The second lithium ion source is disposed between the second electrode unit and the third electrode unit, and has a third main surface on the second electrode unit side and the third electrode unit. A second current collector is provided which is a metal foil having a side fourth main surface.
In the electrolyte, the first electrode unit, the second electrode unit, the third electrode unit, the first lithium ion supply source, and the second lithium ion supply source are immersed.
In the negative electrode of the first electrode unit, the second electrode unit, and the third electrode unit, a first metal lithium having a first thickness attached to the first main surface, and the first metal lithium A second metal lithium having a second thickness smaller than the first thickness affixed to the main surface of the second metal, a third metal lithium having the first thickness affixed to the third main surface, and The fourth metal lithium having the second thickness attached to the main surface of the above 4 is pre-doped with lithium ions.

  According to this configuration, a large amount of lithium ions released from the first metal lithium is supplied to the first electrode unit facing the first metal lithium, and a lithium ion released from the second metal lithium is , And much is supplied to the third electrode unit facing the second metallic lithium. In addition, a large amount of lithium ions released from the third metal lithium is supplied to the second electrode unit facing the third metal lithium, and a lithium ion released from the fourth metal lithium is the fourth lithium ion released from the third metal lithium. Much is supplied to the third electrode unit facing metal lithium. While lithium ions are supplied to the first electrode unit from the first metal lithium and to the second electrode unit from the third metal lithium, the third electrode unit is supplied with the second metal lithium and Lithium ions are supplied from both of the fourth metal lithium. Here, since the thicknesses (second thickness) of the second metal lithium and the fourth metal lithium are smaller than the thicknesses (first thickness) of the first metal lithium and the third metal lithium, the third thickness The amount of lithium ions supplied to the electrode unit is equivalent to that of the first electrode unit and the second electrode unit, and it is possible to make the doping amount of lithium ions uniform among the electrode units.

  The ratio of the first thickness to the second thickness may be in the range of 3: 1 to 3: 2.

  The ratio of the first thickness to the second thickness can be adjusted according to the thickness of the electrode unit (the number of laminated layers of the positive electrode and the negative electrode), and is preferably in the range of 3: 1 to 3: 2. .

  The positive electrode provided in the first electrode unit, the second electrode unit, and the third electrode unit includes a positive electrode current collector that is a porous metal foil and a positive electrode active material, and the front and back sides of the positive electrode current collector And the negative electrode provided in the first electrode unit, the second electrode unit, and the third electrode unit is a negative electrode current collector that is a porous metal foil, and a negative electrode active material. And a negative electrode active material layer laminated on the front and back sides of the negative electrode current collector.

  According to this configuration, lithium ions released from the first lithium ion supply source and the second lithium ion supply source can move in each electrode unit without being blocked by the positive electrode, the negative electrode and the separator. It becomes possible to make the doping amount of lithium ion uniform in the electrode unit.

  The first electrode unit, the second electrode unit, and the third electrode unit may have the same thickness.

  According to this configuration, it is possible to use the electrode unit having the same structure as the first electrode unit, the second electrode unit and the third electrode unit, and at the same time, the doping amount of lithium ion is uniform in each electrode unit. It is possible to

  The electrochemical device may be a lithium ion capacitor.

  As described above, according to the present invention, it is possible to provide an electrochemical device which has excellent productivity and can make the pre-doped state of the negative electrode uniform.

1 is a perspective view of an electrochemical device according to an embodiment of the present invention. It is sectional drawing of the same electrochemical device. It is sectional drawing of the electrode unit with which the same electrochemical device is equipped. It is an enlarged view of the same electrochemical device. It is a schematic diagram which shows the aspect of lithium ion pre dope in the same electrochemical device. It is a table | surface which shows the structure and resistance rise rate of the electrochemical device which concerns on the Example of this invention, and a comparative example.

  An electrochemical device according to the present embodiment will be described.

[Structure of electrochemical device]
FIG. 1 is a perspective view of an electrochemical device 100 according to the present embodiment, and FIG. 2 is a cross-sectional view of the electrochemical device 100. FIG. 2 is a cross-sectional view taken along line AA of FIG.

  The electrochemical device 100 is an electrochemical device that requires lithium ion pre-doping, and can be a lithium ion capacitor. Electrochemical device 100 may also be another electrochemical device that requires lithium ion pre-doping, such as a lithium ion battery. In the following description, the electrochemical device 100 is a lithium ion capacitor.

  As shown in FIGS. 1 and 2, the electrochemical device 100 includes a first electrode unit 101, a second electrode unit 102, a third electrode unit 103, a first lithium ion supply source 104, a second lithium ion supply source 105, An exterior film 106, a positive electrode terminal 107, and a negative electrode terminal 108 are provided. Hereinafter, a stacked body of the first electrode unit 101, the second electrode unit 102, the third electrode unit 103, the first lithium ion supply source 104, and the second lithium ion supply source 105 is referred to as an electrode body 109.

  Each of the first electrode unit 101, the second electrode unit 102, and the third electrode unit 103 is a unit capable of storing electricity. The first electrode unit 101, the second electrode unit 102, and the third electrode unit 103 can have the same structure.

  FIG. 3 is a schematic view of an electrode unit 110 that can be used as the first electrode unit 101, the second electrode unit 102, and the third electrode unit 103. As shown in the figure, the electrode unit 110 includes a positive electrode 120, a negative electrode 130, and a separator 140.

  The positive electrode 120 includes a positive electrode current collector 121 and a positive electrode active material layer 122. The positive electrode current collector 121 is a porous metal foil in which a large number of through holes are formed, and is, for example, an aluminum foil. The thickness of the positive electrode current collector 121 is, for example, 0.03 mm.

  The positive electrode active material layer 122 is formed on both the front and back sides of the positive electrode current collector 121. The positive electrode active material layer 122 can be a mixture of a positive electrode active material and a binder resin, and may further contain a conductive aid. The positive electrode active material is a material capable of adsorbing lithium ions and anions in the electrolytic solution, such as activated carbon and polyacene carbide.

  The binder resin is a synthetic resin for bonding the positive electrode active material, and for example, styrene butadiene rubber, polyethylene, polypropylene, aromatic polyamide, carboxymethyl cellulose, fluorocarbon rubber, polyvinylidene fluoride, isoprene rubber, butadiene rubber, and ethylene propylene rubber Etc. may be used.

  The conductive aid is particles made of a conductive material, and improves the conductivity between the positive electrode active materials. Examples of the conductive aid include carbon materials such as graphite and carbon black. These may be used alone or in combination of two or more. The conductive aid may be a metal material, a conductive polymer, or the like as long as the material has conductivity.

  The negative electrode 130 includes a negative electrode current collector 131 and a negative electrode active material layer 132. The negative electrode current collector 131 is a porous metal foil in which a large number of through holes are formed, and is, for example, a copper foil. The thickness of the negative electrode current collector 131 is, for example, 0.015 mm.

  The negative electrode active material layer 132 is formed on both the front and back sides of the negative electrode current collector 131. The negative electrode active material layer 132 can be a mixture of a negative electrode active material and a binder resin, and may further contain a conductive aid. The negative electrode active material is a material capable of storing lithium ions in the electrolytic solution, for example, non-graphitizable carbon (hard carbon), a carbon-based material such as graphite or soft carbon, an alloy-based material such as Si or SiO, or the like The composite material of can be used.

  The binder resin is a synthetic resin for bonding the negative electrode active material, and for example, styrene butadiene rubber, polyethylene, polypropylene, aromatic polyamide, carboxymethyl cellulose, fluorocarbon rubber, polyvinylidene fluoride, isoprene rubber, butadiene rubber and ethylene propylene rubber Etc. may be used.

  The conductive aid is particles made of a conductive material, and improves the conductivity between the negative electrode active materials. Examples of the conductive aid include carbon materials such as graphite and carbon black. These may be used alone or in combination of two or more. The conductive aid may be a metal material, a conductive polymer, or the like as long as the material has conductivity.

  The separator 140 separates the positive electrode 120 and the negative electrode 130, and transmits ions contained in the electrolytic solution. The separator 140 can be a woven fabric, a non-woven fabric, a synthetic resin microporous film or the like, and can be, for example, an olefin resin as a main material.

  As shown in FIG. 3, the positive electrode 120, the negative electrode 130 and the separator 140 are stacked so that the positive electrode 120 and the negative electrode 130 are alternately disposed via the separator 140, and the lowermost layer and the uppermost layer excluding the separator 140 are the negative electrode 130. Is configured as. The number of stacked layers of the positive electrode 120 and the negative electrode 130 is not particularly limited, and, for example, nine layers of the positive electrode 120 and ten layers of the negative electrode 130 can be used.

  The electrode unit 110 having the above structure can be used as the first electrode unit 101, the second electrode unit 102, and the third electrode unit 103. The positive electrode current collector 121 of each electrode unit is electrically connected to the positive electrode terminal 107 directly or through a wire not shown, and the negative electrode current collector 131 of each electrode unit is electrically connected to the negative electrode terminal 108 directly or by a wire not shown Connected.

  The first lithium ion supply source 104 is disposed between the first electrode unit 101 and the third electrode unit 103, and supplies lithium ions to the negative electrode 130 of each electrode unit. FIG. 4 is an enlarged view of the electrode body 109. As shown in the figure, the first lithium ion supply source 104 includes a lithium current collector 151, a first metal lithium 152, and a second metal lithium 153.

  The lithium current collector 151 is a metal foil, for example, a copper foil. The lithium current collector 151 may be a porous metal foil in which a large number of through holes having a diameter of several tens to several hundreds of micrometers are formed, or may be a metal foil having no through holes. The lithium current collector 151 is electrically connected to the negative electrode current collector 131 of each electrode unit directly or via the negative electrode terminal 108.

  As shown in FIG. 4, among the main surfaces of the lithium current collector 151, the surface on the first electrode unit 101 side is a first main surface 151a, and the surface on the third electrode unit 103 side is a second main surface. It is referred to as 151b.

  The first metal lithium 152 is attached to the first main surface 151a by pressure bonding or the like, and the second metal lithium 153 is attached to the second main surface 151b by pressure bonding or the like. As shown in FIG. 4, the thickness of the first metal lithium 152 is referred to as a first thickness D1, and the thickness of the second metal lithium 153 is referred to as a second thickness D2.

  Here, the first thickness D1 is larger than the second thickness D2. Specifically, the ratio D1: D2 is preferably in the range of 3: 1 to 3: 2, and in particular, D1: D2 is more preferably 2: 1.

  The second lithium ion supply source 105 is disposed between the second electrode unit 102 and the third electrode unit 103, and supplies lithium ions to the negative electrode 130 of each electrode unit. As shown in FIG. 4, the second lithium ion supply source 105 includes a lithium current collector 161, a third metal lithium 162 and a fourth metal lithium 163.

  The lithium current collector 161 is a metal foil, for example, a copper foil. The lithium current collector 161 may be a porous metal foil in which a large number of through holes having a diameter of several tens to several hundreds of micrometers are formed, or may be a metal foil having no through holes. The lithium current collector 161 is electrically connected to the negative electrode current collector 131 of each electrode unit directly or via the negative electrode terminal 108.

  As shown in FIG. 4, among the main surfaces of the lithium current collector 161, the surface on the second electrode unit 102 side is the third main surface 161a, and the surface on the third electrode unit 103 side is the fourth main surface. Suppose it is 161b.

  The first metal lithium 162 is attached to the third main surface 161 a by pressure bonding or the like. The second metal lithium 163 is attached to the fourth major surface 161 b by pressure bonding or the like. As shown in FIG. 4, the third metal lithium 162 has the same thickness D 1 as the first metal lithium 152, and the fourth metal lithium 163 has the same thickness D 2 as the second metal lithium 153.

  As described above, the first thickness D1 is larger than the second thickness D2, and the ratio D1: D2 is preferably in the range of 3: 1 to 3: 2, and in particular, D1: D2 is more preferably 2: 1. .

  The exterior film 106 forms an accommodation space for accommodating the electrode body 109 and the electrolytic solution. The exterior film 106 is a laminate film in which a metal foil such as aluminum foil and a resin are laminated, and is fused and sealed around the electrode body 109. Instead of the exterior film 106, a can-like member or the like capable of sealing the storage space may be used.

Electrolyte solution to be accommodated in the accommodating space together with the electrode body 109 is not particularly limited, for example, LiPF ₆ or the like can be used a solution as a solute.

  The positive electrode terminal 107 is an external terminal of the positive electrode 120, and is electrically connected to the positive electrode 120 of each electrode unit. The positive electrode terminal 107 is drawn from between the exterior films 106 to the outside of the accommodation space as shown in FIG. The positive electrode terminal 107 may be a foil or a wire made of a conductive material.

  The negative electrode terminal 108 is an external terminal of the negative electrode 130, and is electrically connected to the negative electrode 130 of each electrode unit. The negative electrode terminal 108 is drawn from between the exterior films 106 to the outside of the accommodation space as shown in FIG. The negative electrode terminal 108 may be a foil or a wire made of a conductive material.

[About lithium ion pre-doping]
When the electrode body 109 is immersed in the electrolytic solution in a state where the current collector 151 for lithium and the current collector 161 for lithium and the negative electrode current collector 131 are electrically connected in the manufacturing step of the electrochemical device 100, the first metal The lithium 152, the second metal lithium 153, the third metal lithium 162, and the fourth metal lithium 163 are dissolved, and lithium ions are released into the electrolytic solution. The lithium ions move in the electrolytic solution, and are doped (pre-doped) in the negative electrode active material layer 132 of the negative electrode 130 provided in each electrode unit.

  FIG. 5 is a schematic view showing pre-doping of lithium ions. As shown in the figure, most of the lithium ions released from the first metal lithium 152 are supplied to the first electrode unit 101 facing the first metal lithium 152 (arrow A in the figure). Further, a large amount of lithium ions released from the second metal lithium 153 is supplied to the third electrode unit 103 facing the second metal lithium 153 (arrow B in the figure).

  Since the first thickness D1 which is the thickness of the first metal lithium 152 is larger than the second thickness D2 which is the thickness of the second metal lithium 153, lithium supplied from the second metal lithium 153 to the third electrode unit 103 is The amount of ions is smaller than the amount of lithium ions supplied from the first metal lithium 152 to the first electrode unit 101.

  Similarly, most of the lithium ions released from the third metal lithium 162 are supplied to the second electrode unit 102 facing the third metal lithium 162 (arrow C in the figure). Further, a large amount of lithium ions released from the fourth metal lithium 163 is supplied to the third electrode unit 103 facing the fourth metal lithium 163 (arrow D in the figure).

  Since the first thickness D1 which is the thickness of the third metal lithium 162 is larger than the second thickness D2 which is the thickness of the fourth metal lithium 163, lithium supplied from the fourth metal lithium 163 to the third electrode unit 103 is The amount of ions is smaller than the amount of lithium ions supplied from the third metal lithium 162 to the second electrode unit 102.

  However, since lithium ions are supplied to the third electrode unit 103 from both the second metal lithium 153 and the fourth metal lithium 163, the amount of lithium ions supplied to the third electrode unit 103 is the first electrode unit 101. And the second electrode unit 102. Thereby, the doping amount of lithium ions becomes uniform among the first electrode unit 101, the second electrode unit 102, and the third electrode unit 103, and the long-term stability of the electrochemical device 100 can be ensured.

  Assuming that the first thickness D1 and the second thickness D2 are equal to each other, the amount of lithium ions supplied to the third electrode unit 103 is supplied to each of the first electrode unit 101 and the second electrode unit 102. About twice the amount of For this reason, in order to make the doping amount of each electrode unit equal, it is necessary to further arrange a lithium ion source in the upper layer of the first electrode unit 101 and the lower layer of the second electrode unit 102.

  On the other hand, by making the first thickness D1 larger than the second thickness D2, the amount of lithium ions to be doped in each electrode unit by only the first lithium ion supply source 104 and the second lithium ion supply source 105 can be increased. It can be made comparable. Further, even when the thickness of each electrode unit (the number of stacked layers of the positive electrode 120 and the negative electrode 130) is different, the doping of each electrode unit is adjusted by adjusting the ratio of the first thickness D1 and the second thickness D2. The amount can be made uniform.

  Further, since the first lithium ion supply source 104 and the second lithium ion supply source 105 have the same structure, it is not necessary to make both of them separately, and the manufacturing cost can be reduced.

  As described above, each metal lithium dissolves in pre-doping, and each metal lithium does not exist when the electrochemical device 100 is used. However, the arrangement of metallic lithium before pre-doping can be determined by the residual lithium metal or the like present in the lithium current collector 151 and the lithium current collector 161.

[Modification]
As described above, the electrochemical device 100 includes the electrode assembly 109 in which the first electrode unit 101, the second electrode unit 102, the third electrode unit 103, the first lithium ion supply source 104, and the second lithium ion supply source 105 are stacked. Prepare. Here, the electrochemical device 100 may have a structure in which a plurality of electrode bodies 109 are stacked and housed in a housing space. Even in this case, it is possible to make the lithium ion doping amount uniform among the electrode units provided in each electrode body 109.

  Metal lithium having different thicknesses was crimped on both sides of the copper foil to prepare the above-mentioned lithium ion source. The positive electrode and the negative electrode were laminated via a separator to produce the above-mentioned electrode unit. A lithium ion source was disposed between the electrode units, and three electrode units were stacked to fabricate an electrode body. The positive electrode terminal and the negative electrode terminal were connected to the electrode body, and enclosed in a laminate film together with the electrolytic solution. Thus, a lithium ion capacitor according to an example was produced.

  Moreover, metal lithium with the same thickness was crimped | bonded to both surfaces of copper foil, and the lithium ion supply source was produced. Except for this, the configuration is the same as that of the example, and a lithium ion capacitor according to the comparative example is manufactured.

  FIG. 6 is a table showing the ratio of the first thickness D1 to the second thickness D2 in lithium ion capacitors according to Examples and Comparative Examples.

  After storing the lithium ion capacitor according to the example and the comparative example for 30 days under 40 ° C. environment, the negative electrode on the outside of the outermost electrode unit and the other electrode units evaluate the lithium ion amount doped in the central negative electrode. did. Charge and discharge were performed at a current amount of 100 C based on the cell capacity. The charge and discharge cycle was performed with CCCV 1 min of charge 100 C, discharge 100 C, and 2.2 V cutoff. Assuming that the initial internal resistance was 100, the rate of change of the internal resistance was evaluated. The internal resistance was obtained from the voltage drop obtained from the discharge curve. The rate of change of internal resistance is shown in FIG.

  As shown in the figure, it can be seen that in the lithium ion capacitor according to the example, the rate of increase in internal resistance is smaller than in the lithium ion capacitor according to the comparative example, and the life is improved by making the doping amount uniform.

  As mentioned above, although embodiment of this invention was described, this invention is not limited only to the above-mentioned embodiment, of course, a various change can be added.

DESCRIPTION OF SYMBOLS 100 ... Electrochemical device 101 ... 1st electrode unit 102 ... 2nd electrode unit 103 ... 3rd electrode unit 104 ... 1st lithium ion supply source 105 ... 2nd lithium ion supply source 106 ... Package film 109 ... Electrode body 110 ... electrode Unit 120 ... positive electrode 121 ... positive electrode current collector 122 ... positive electrode active material layer 130 ... negative electrode 131 ... negative electrode current collector 132 ... negative electrode active material layer 140 ... separator 151, 161 ... current collector for lithium 152 ... first metal lithium 153 ... 2nd metal lithium 162 ... 3rd metal lithium 163 ... 4th metal lithium

Claims (5)

A first electrode unit in which a positive electrode and a negative electrode are alternately stacked via a separator;
A second electrode unit in which a positive electrode and a negative electrode are alternately stacked via a separator;
A positive electrode and a negative electrode are alternately stacked via a separator, and a third electrode unit positioned between the first electrode unit and the second electrode unit;
It is disposed between the first electrode unit and the third electrode unit, and has a first main surface on the first electrode unit side and a second main surface on the third electrode unit side. A first lithium ion source comprising a first current collector that is a metal foil;
It is disposed between the second electrode unit and the third electrode unit, and has a third main surface on the second electrode unit side and a fourth main surface on the third electrode unit side. A second lithium ion source provided with a second current collector that is a metal foil, the first electrode unit, the second electrode unit, the third electrode unit, the first lithium ion source, and An electrolyte in which the second lithium ion source is immersed;
The negative electrode of the first electrode unit, the second electrode unit, and the third electrode unit includes a first metal lithium having a first thickness attached to the first main surface, and the first metal lithium. A second metal lithium attached to the main surface of 2 and having a second thickness smaller than the first thickness; a third metal lithium having the first thickness attached to the third main surface; An electrochemical device, wherein a lithium metal is pre-doped from a fourth metal lithium having the second thickness attached to the main surface of the four. An electrochemical device according to claim 1, wherein
An electrochemical device wherein the ratio of the first thickness to the second thickness is in the range of 3: 1 to 3: 2. An electrochemical device according to claim 1 or 2, wherein
The positive electrode provided in the first electrode unit, the second electrode unit, and the third electrode unit includes a positive electrode current collector that is a porous metal foil and a positive electrode active material, and the front and back sides of the positive electrode current collector A positive electrode active material layer laminated on the
The negative electrode included in the first electrode unit, the second electrode unit, and the third electrode unit includes a negative electrode current collector that is a porous metal foil and a negative electrode active material, and both the front and back sides of the negative electrode current collector An electrochemical device comprising a negative electrode active material layer laminated to the The electrochemical device according to any one of claims 1 to 3, wherein
An electrochemical device, wherein the first electrode unit, the second electrode unit, and the third electrode unit have the same thickness. The electrochemical device according to any one of claims 1 to 4, wherein
An electrochemical device that is a lithium ion capacitor.

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