JP2009123374A - Nonaqueous electrolyte power storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte power storage device having sufficient safety and power storage performance, easy to manufacture a negative electrode, and capable of reducing cost. <P>SOLUTION: The nonaqueous electrolyte power storage device includes: a sheet-like positive electrode made of a carbon material; a sheet-like negative electrode facing the positive electrode through a separator and made of a material capable of absorbing/releasing lithium; and an electrolyte containing a lithium salt. The positive electrode and the negative electrode are formed by being coated substantially in a rectangular shape on the surface of a sheet-like current collector having an outside electrode part projecting to one side having substantially a rectangular shape, the negative electrode is coated on at least one side out of the side where the outside electrode part is formed on the current collector and the side facing it so as to have a blank space, metallic lithium is stuck on the blank space of the negative current collector, the coated region of the negative electrode has a distance of ≤90 mm from the side facing the negative electrode in the metallic lithium, the positive electrode is coated on the region other than the outside electrode part, and the coated region is positioned on the inner side than that of the facing negative electrode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a sheet-like positive electrode made of a carbon material, a sheet-like negative electrode made of a material capable of occluding and releasing thium and disposed opposite to the positive electrode via a separator, and an electrolyte containing a lithium salt And a non-aqueous electrolytic electricity storage device in which a positive electrode, a separator, and a negative electrode are sequentially laminated. Specifically, the present invention relates to a technical improvement for doping lithium ions in advance in a non-aqueous electrolytic electricity storage device of a type in which lithium ions are previously stored in a negative electrode.

  The above-mentioned type of non-aqueous electrolytic electricity storage device (hereinafter referred to as pre-doped electricity storage device) is capable of rapid charging and has lithium ions stored in advance in the negative electrode, so that the potential of the negative electrode is lowered and a large voltage can be obtained. High energy capacity can be obtained. Therefore, it is expected to be used for wind power generation load leveling devices, instantaneous power failure countermeasure devices, regenerative power storage for automobiles, and the like.

  In the conventional lithium ion storage (pre-doping) method in the pre-doped type electricity storage device, there is a method of pre-doping lithium ions by scraping a part of the negative electrode or pasting lithium metal on the negative electrode. For example, as described in Japanese Patent No. 3485935, a method in which lithium metal is attached to the outside of a mesh current collector, a negative electrode is formed on the inside, and lithium ions are pre-doped into the negative electrode through this mesh has become the mainstream. It's getting on. In this method, the lithium metal foil and the negative electrode face each other through the mesh current collector, and lithium ions are pre-doped from the direction perpendicular to the negative electrode. Hereinafter, such a pre-doping method is referred to as a “vertical doping method”.

  In the pre-doping method in which a part of the negative electrode is scraped or a lithium metal is stuck on the negative electrode, irregularities are formed on the part where the lithium metal is stuck, and current concentrates on the part, so that the lithium metal is easily deposited. As is well known, if the deposited lithium metal breaks the separator and comes into contact with the positive electrode, an internal short circuit may occur, resulting in serious consequences such as ignition. In the vertical dope method, a method using a current collector having a hole such as a mesh requires a complicated process of applying lithium to the surface of the current collector having a complicated shape, which increases the manufacturing cost. Processing the current collector into a mesh itself also increases the manufacturing cost. In the hole portion such as a mesh, the electrical conductivity decreases and the resistance increases. That is, energy loss increases.

  Therefore, the present inventors have made manufacturing ease and cost reduction the most important requirements, and forming a negative electrode on the surface of the sheet-like current collector, sticking lithium metal on the same surface as the current collector surface, The “horizontal doping method” in which lithium ions are doped into the negative electrode along the surface of the current collector was adopted. In the horizontal dope method, for example, a negative electrode can be easily formed on the surface of the current collector by forming (applying) a slurry-like negative electrode active material using a squeegee or a transfer roll. Of course, if attention is paid only to ease of manufacture and price reduction, sufficient safety and power storage performance cannot be ensured.

  The present invention has been made in view of the above problems, and an object thereof is to provide a non-aqueous electrolytic electricity storage device that has sufficient safety and electricity storage performance, can be easily manufactured negatively, and can be expected to be reduced in price. .

  In order to achieve the above-mentioned object, the present inventors have made a condition for lithium metal to diffuse in the horizontal direction along the sheet-shaped current collector and sufficiently pre-dope the negative electrode, a device shape in which lithium metal is difficult to deposit, etc. And the present invention was created by finding the optimum conditions for solving the above-mentioned problems in the horizontal dope method.

The present invention relates to a sheet-like positive electrode made of a carbon material, a sheet-like negative electrode made of a material capable of occlusion / release of lithium arranged opposite to the positive electrode and a separator, and an electrolysis using a lithium salt as a supporting electrolyte. A non-aqueous electrolytic electricity storage device comprising a liquid,
Each of the positive electrode and the negative electrode is formed by applying each active material mixture in a substantially rectangular shape to a coating region on the surface of a substantially rectangular sheet-shaped current collector provided with an external electrode part on one side.
The positive electrode has a coating region in a region excluding the external electrode part,
The negative electrode has a strip-shaped blank provided along at least one side of the substantially rectangular sheet-shaped current collector as an uncoated region, and a region excluding the uncoated region and the external electrode portion as a coated region,
The application area of the positive electrode is inside the application area of the negative electrode arranged opposite to the positive electrode,
In the uncoated area of the negative electrode, a strip-shaped lithium metal is adhered along the strip-shaped margin, and the coated area of the negative electrode is at a distance of 90 mm or less from the lithium metal adhered area. .

  In the non-aqueous electrolyte electricity storage device, the uncoated region is formed on two sides facing each other in the substantially rectangular sheet-shaped current collector, and the lithium metal is attached to at least one of the two sides. Good. It is more preferable that the uncoated region is provided on both sides of the side where the external electrode portion is formed and the side facing the side.

  The present invention also refers to the formation conditions of the external electrode, and the non-electrolytic power storage device provided such that the external electrode portion of the positive electrode and the external electrode portion of the negative electrode do not overlap in the stacking direction, A non-electrolyte electric storage device in which the external electrode portions of the positive electrode and the negative electrode protrude from a part of one side of the same side of each sheet-like current collector can also be provided.

Any one of the above non-electrolyte power storage device manufacturing methods is also within the scope of the present invention. The invention according to the method includes providing the coating region on the surface of the sheet current collector for positive electrode, A positive electrode application step of applying a material mixture;
A negative electrode application step of providing the non-application area and the application area on the surface of the sheet-like current collector for a negative electrode, and applying a negative electrode active material mixture to the application area;
Adhering lithium metal to the uncoated area of the negative electrode sheet-shaped current collector;
A lamination step of laminating the positive electrode and the negative electrode in a state of being opposed to each other with a separator interposed therebetween;
The laminated body obtained by the laminating step is enclosed in a laminate film outer package, stored for a predetermined period of time, and diffusing lithium metal into the negative electrode. In the negative electrode applying step, the coated area is separated from the boundary with the uncoated area. Provided to be a distance of 90 mm or less,
In the step of applying the lithium metal, the lithium application region is 90 mm or less from the application region of the negative electrode active material.

  Further, in the method for manufacturing a non-electrolyte electrical storage device, in the coating process, in the sheet-like current collector, if an electrode active material is applied along a direction parallel to the side on which the electrode is formed, preferable.

  According to the non-aqueous electrolytic electricity storage device of the present invention, sufficient safety and electricity storage performance are provided, manufacturing at a low cost is possible, and cost reduction can be expected.

=== First Embodiment ===
FIG. 1 shows a schematic structure (A) on the negative electrode side and a schematic structure (B) on the positive electrode side of the nonaqueous electrolytic storage device (hereinafter, storage device) in the first embodiment of the present invention. In the structure, each of the positive electrode 10p and the negative electrode 10n is applied to the surface of a substantially rectangular sheet-shaped current collector (hereinafter, current collector sheets, 11p, 11n). In addition, in order to take out the electricity stored in the electricity storage device when the electricity storage device is configured by laminating the current collector sheets (11p, 11n) with the positive electrode 10p and the negative electrode 10n arranged to face each other with a separator interposed therebetween. It is necessary to provide a portion (external electrode portion) to be a terminal of the first electrode, and in the first embodiment, a convex region (12p, 12n) on one side of a substantially rectangular shape of the current collector sheet (11p, 11n). ) And the region is used as the external electrode portion (12p, 12n). That is, the positive electrode 10p and the negative electrode 10n are applied on the current collector sheets (11p, 11n) with the external electrode portions (12p, 12n) as blanks, respectively. In the following, in the rectangular current collector sheets (11p, 11n), the extension direction of the side 13 on the side where the external electrode portions (12p, 12n) are projected is defined as the vertical direction, and the direction orthogonal to the extension direction. Is described as the left-right direction.

  The current collector sheet on the positive electrode side protrudes from one side of a substantially square having the same length of the top, bottom, left, and right sides, and the projecting region serves as an external electrode portion. And the application | coating shape of the positive electrode 10p is a substantially rectangular (square) used as the substantially whole surface other than the external electrode part 12p (B). On the other hand, on the negative electrode side, a current collector sheet 11n having a shape in which the external electrode portion 12n is protruded on the short side of a substantially rectangular shape whose left and right lengths are slightly longer than the upper and lower lengths is employed. In the negative electrode 10n, in the current collector sheet 11n, a margin (15, 16) is formed along at least one side of two sides (13, 14) extending in the vertical direction in addition to the external electrode portion 12n. (A). In this example, margins (15, 16) are formed on both sides (13, 14) in the vertical direction. Moreover, the substantially rectangular lithium metal 20 extended in an up-down direction is affixed on each margin part (15, 16) along the said both sides (13, 14). Thereby, lithium ions diffuse from the lithium metal in the left-right direction along the surface of the current collector sheet 11n, and the negative electrode 10n applied on the current collector sheet 11n is pre-doped.

  2A and 2B show a basic structure of the electricity storage device of the first example, and FIG. 2C schematically shows a current distribution state in the electricity storage device. The power storage device 1a has a laminated structure in which the positive electrode 10p and the negative electrode 10n applied and formed on the current collector sheets (11p, 11n) as described above are arranged to face each other with the separator 30 therebetween, and the positive and negative electrodes (10p , 10n) are laminated so that the external electrode portions (12p, 12n) protrude in opposite directions. (A) is a figure for comparing the area | region of the positive / negative bipolar | polarity (10p, 10n) in a lamination | stacking state, when the said electrical storage device 1a is seen from an upper surface. (B) is sectional drawing of the said laminated structure. Thus, the application regions of the positive and negative electrodes (10p, 10n) are Xp <Xn and Yp <Yn, and the application region of the positive electrode 10p is accommodated inside the application region of the negative electrode 10n in the stacked state. ing. That is, in the electricity storage device 1a, the current I concentrates on the edge portion 17 of the electrode (C), and in the negative electrode 10n, lithium metal tends to be deposited on the edge portion 17n. Therefore, in the present invention, the current is not concentrated on the edge 17n of the negative electrode 10n by setting the electrode size so that the entire region of the positive electrode 10p is within the region of the negative electrode 10n. Therefore, the possibility that lithium metal is deposited is reduced. For example, even if lithium metal is deposited on the edge 17n of the negative electrode 10n, there is no positive electrode 10p on the opposite surface of the edge so that no short circuit occurs.

=== Second Embodiment ===
In the said 1st Example, although the lithium metal was affixed on each of two sides extended in an up-down direction in the substantially rectangular collector sheet, the form which affixes lithium metal only to one side is also possible. Conceivable. Here, the most preferable example in this mode is assumed to be the second example.

  FIG. 3 shows the electrode shape of the electricity storage device according to the second example. In the first embodiment, the external electrode portions (12p, 12n) are provided so as to project the current collector sheets (11p, 11n) substantially vertically, but in the second embodiment, the vertical direction It protrudes on one of the upper side or the lower side of one side 13 of the. Further, the side in the left-right direction 18 is shorter than the side in the up-down direction (13, 14), and has a clear rectangle. The positive electrode 10p is applied to almost the entire surface excluding the external electrode portion 11p, as in the first embodiment. The negative electrode 10n is applied leaving a blank 16 where the lithium metal 20 is stuck. However, in the second embodiment, the margin 16 is provided only on the side 14 where the external electrode portion 12n is not provided, out of the two sides (13, 14) extending in the vertical direction.

FIG. 4 shows the basic structure of the electricity storage device in the second embodiment. (A) is a figure for comparing the area | region of the positive / negative bipolar | polarity (10p, 10n) in a lamination | stacking state, when the electrical storage device 1b in a 2nd Example is seen from an upper surface. (B) is a lamination | stacking sectional drawing of the electrical storage device 1b in a 2nd Example. In the electricity storage device 1b according to the second example, as in the first example, the region of the positive electrode 10p is located inside the negative electrode 10n region (Xn> Xp, Yn> Yp). However, in the second example 1b, unlike the first example 1a, the external electrode portions (12p, 12n) are laminated so as to be in the same direction. Further, the external electrode portions (12p, 12n) on the respective sides of the positive electrode 10p and the negative electrode 10n do not overlap in the stacking direction, and the external electrode portions (12p, 12n) of both positive and negative electrodes are not easily in contact with each other. It has become. Further, in this configuration, the lithium metal 20 is attached only to the margin 16 of the side 14 on the side where the external electrode portion 12n is not provided. Therefore, there is no positive electrode current collector sheet 11p on the opposite surface of the lithium metal 20, and in addition to the deposition of the lithium metal accompanying the charge / discharge reaction, the positive and negative electrodes formed by the adhered lithium metal 20 are disposed. It has a structure that can prevent short circuit.
=== About the electrode coating process ===
The manufacturing method of the electricity storage device in each of the above embodiments will be described in particular with respect to the electrode application process. Since the electricity storage device of the present invention employs a horizontal dope method, it is easy to manufacture and can reduce manufacturing costs. Below, the application | coating process for making manufacture easier is demonstrated. FIG. 5 is an explanatory diagram of the coating process of the electrodes (10p, 10n), (A) is a coating region of the negative electrode 10n in the electricity storage device shown in the first embodiment, and (B) to (E) ) Shows an example of the process for applying the negative electrode to the application region.

  When the negative electrode 10n is formed by a coating process, the external electrode portion 12n and the margins (15, 16:40) extending in the vertical direction along the sides (13, 14) of the rectangular current collector sheet 11n are formed into the negative electrode 10n. (A), the application direction can be two directions, up and down and left and right. (B)-(E) mentioned the process in the case of apply | coating in the left-right direction. In the coating process in the comparative example, a mask 41 is formed in the blank portion in advance so that the uncoated portion 40 is not selectively coated, and then the slurry-like electrode active material 42 is coated using a squeegee 43 or the like ( B) to (D), the mask 41 is peeled off after application (E).

  However, the steps shown in the above (B) to (E) include complicated steps such as mask formation and peeling. Further, a step 45 is generated between the surface of the mask 41 and the surface of the current collector sheet 11n to which the electrode active material 42 is applied (D), and there is a possibility that the coating unevenness 45 is generated near the edge 44 of the mask 41. (D, E). On the other hand, in the case of applying in the vertical direction along the marginal sides (13, 14), the width 19 is determined by the mask 41 simply by applying the squeegee 43 to the mask 41, and continuous coating is possible. The electrode sheet can be created. If applied in the vertical direction, the electrode active material 42 applied on the mask 41 is not wasted. Further, the extending direction of the edge 44 of the mask 41 and the coating direction are parallel, and the coating unevenness 45 does not occur. Thus, in the present invention, the shape of the current collector and the electrode shape in the electricity storage device are mentioned, and the application process can be simplified by the shape. The present invention also extends to a method for manufacturing an electricity storage device specialized for the current collector and electrode shape.

=== Multi-layered storage device ===
As a manufacturing process of the electricity storage device of this example, first, the positive electrode 10p and the negative electrode 10n were applied on the current collector sheet (11p, 11n) by the method described above, and the negative electrode 10n had a blank (15, 16). Lithium metal 20 is attached to the part. What is necessary is just to determine the quantity of the lithium metal 20 suitably in consideration of the quantity to pre-dope. Then, the positive electrode 10p and the negative electrode 10n are opposed and stacked with the separator 30 interposed therebetween. Up to this point, the manufacturing process has been described for a single-layer power storage device (1a, 1b) composed of a pair of positive and negative electrodes. There is a high possibility of being used as a power storage device having a multilayered structure (multilayer power storage device).

  FIG. 6 shows a cross-sectional view of the stacked state of the multilayered electricity storage device. Embodiments in which the electricity storage devices of the first example and the second example are multilayered are shown in (A) and (B), respectively. The positive electrode 10p and the negative electrode 10n are respectively applied to both surfaces of one current collector sheet (11p, 11n), and a separator 30 is interposed between the positive and negative electrodes. That is, the configuration of the first and second embodiments is each layer (1a, 1b) having a multilayer structure. For the multilayer power storage device (A) corresponding to the first embodiment, each layer 1a is laminated so that the external electrode portions (12p, 12n) of the same pole protrude in the same direction, and the corresponding multilayer power storage of the second embodiment In the device (B), positive and negative external electrode portions (12p, 12n) protrude in the same direction, and the external electrode portions (12p, 12n) of the positive electrode 10p and the negative electrode 10n overlap with each other in the stacking direction. I try not to.

  In order to obtain a usable electricity storage device regardless of one layer or multiple layers, an external terminal is connected to the external electrode portion (12p, 12n) by welding or the like. In the case of a multilayer structure, the same poles are connected in parallel. In this way, an electricity storage device as a structure is assembled. Next, lithium ions are pre-doped on the negative electrode 10n of the electricity storage device in the assembled state. For this purpose, the assembled structure is enclosed in a laminate film. Then, the sealed state is stored for a predetermined period (about two weeks in this embodiment), and a usable multilayer power storage device is completed.

=== Pre-doping of lithium ions ===
In the present invention, lithium ions are pre-doped by a horizontal doping method. However, in the horizontal doping method, there is a possibility that lithium ions are not sufficiently diffused at a position far from the bonding position of the lithium metal 20 in the application region of the negative electrode 11n. Alternatively, an extremely long time may be required for sufficient diffusion. The most significant feature of the present invention is that the relationship between the lithium metal attachment position and the application region of the negative electrode 10n is defined. And in order to find the optimal condition in the said relationship, the diffusion state of lithium ion was evaluated by making into the parameter the distance (henceforth diffusion distance) of the negative electrode side and the negative electrode area | region in the lithium metal 20 stuck. FIG. 7 shows a schematic diagram of the diffusion distance. When the lithium metal 20 is attached to both the left and right sides of the negative electrode 10n as in the first embodiment, the distance between the side 21 of the lithium 20 that faces the negative electrode 10n and the line 22 that equally divides the negative electrode region into left and right parts is It becomes the diffusion distance L (A). When the lithium metal 20 is attached to only one side 14 as in the second embodiment, the side 21 of the lithium metal 20 that faces the negative electrode 10n and the side 13 of the negative electrode 10n that does not face that side Is the diffusion distance L (B). The evaluation was performed by preparing various types of single-layer electricity storage devices with different diffusion distances L as samples and confirming whether lithium ions were diffused in each sample.

The evaluation results are shown in Table 1 below.

  From the evaluation result, it was found that when the diffusion distance L was 90 mm, lithium ion diffusion (presence of lithium ions) was confirmed, and when the diffusion distance L was 100 mm, it was not sufficiently diffused. Therefore, in the present invention, the diffusion distance L is defined as 90 mm or less. By setting the diffusion distance L to 90 mm or less, sufficient power storage performance can be obtained.

=== Regarding Application Area ===
In the present invention, the lithium ions are horizontally doped, and the relationship between the lithium metal and the negative electrode coating region, and in each of the above embodiments, the negative electrode has a band-like shape along the side parallel to the side on which the external electrode is formed. A margin was provided, and the margin and the external electrode were set as an uncoated region. Of course, the shape of the external electrode is not limited to a convex shape, and may be provided in a strip shape along one side of a rectangular sheet-shaped current collector. The region for attaching the lithium metal is not limited to the side where the external electrode is formed or the side facing it. The present invention relates to a positive electrode and a negative electrode applied in a substantially rectangular shape on a current collector sheet, the positive electrode application region being inside the negative electrode application region opposed to each other, and the negative electrode application region and the lithium metal The region to be attached is characterized by being 90 mm or less.

It is a figure which shows the electrode structure of the nonaqueous electrolyte electrical storage device in 1st Example of this invention. It is a schematic structure figure of the nonaqueous electrolyte electrical storage device in the 1st example. It is a figure which shows the electrode structure of the nonaqueous electrolyte electrical storage device in the 2nd Example of this invention. It is a schematic structure figure of the nonaqueous electrolyte electrical storage device in the 2nd example of the above. It is explanatory drawing about the application | coating process of the electrode in a nonaqueous electrolyte electrical storage device. It is a schematic structure figure of the electrical storage device which multilayered the nonaqueous electrolyte electrical storage device in the said 1st and 2nd Example. It is explanatory drawing about the diffusion distance of the lithium ion in the nonaqueous electrolyte electrical storage device in the said 1st and 2nd Example.

Explanation of symbols

1a, 1b Nonaqueous electrolyte electricity storage device 10p Positive electrode 10n Negative electrode 11p, 11n Current collector 12p, 12n External electrode part 20 Lithium metal 30 Separator

Claims (7)

A sheet-like positive electrode made of a carbon material, a sheet-like negative electrode made of a material capable of occluding and releasing lithium disposed opposite to the positive electrode via a separator, and an electrolyte using a lithium salt as a supporting electrolyte Non-aqueous electrolytic electricity storage device,
Each of the positive electrode and the negative electrode is formed by applying each active material mixture in a substantially rectangular shape to a coating region on the surface of a substantially rectangular sheet-shaped current collector provided with an external electrode part on one side.
The positive electrode has a coating region in a region excluding the external electrode part,
The negative electrode has a strip-shaped blank provided along at least one side of the substantially rectangular sheet-shaped current collector as an uncoated region, and a region excluding the uncoated region and the external electrode portion as a coated region,
The application area of the positive electrode is inside the application area of the negative electrode arranged opposite to the positive electrode,
A band-shaped lithium metal is adhered to the non-coated area of the negative electrode along the band-shaped margin, and the coated area of the negative electrode is at a distance of 90 mm or less from the bonded area of the lithium metal. Non-aqueous electrolyte electricity storage device.   In Claim 1, the said non-application area | region is formed in two sides which mutually oppose in the said substantially rectangular sheet-like collector, The said lithium metal is affixed on the at least 1 side of the said 2 sides. Non-aqueous electrolyte electricity storage device characterized.   3. The non-electrolyte storage device according to claim 2, wherein the uncoated region is provided on both sides of the side where the external electrode portion is formed and the side facing the side.   4. The non-electrolyte storage device according to claim 1, wherein the positive external electrode and the negative external electrode are provided so as not to overlap in the stacking direction. 5.   5. The non-electrolytic electricity storage device according to claim 4, wherein each of the external electrode portions of the positive electrode and the negative electrode protrudes from a part of one side of the same side of each sheet-like current collector. It is a manufacturing method of the nonelectrolyte electrical storage device according to claim 1,
A positive electrode application step of providing the application region on the surface of the sheet current collector for positive electrode, and applying a positive electrode active material mixture to the application region;
A negative electrode application step of providing the non-application area and the application area on the surface of the sheet-like current collector for a negative electrode, and applying a negative electrode active material mixture to the application area;
Adhering lithium metal to the uncoated area of the negative electrode sheet-shaped current collector;
A lamination step of laminating the positive electrode and the negative electrode in a state of being opposed to each other with a separator interposed therebetween;
The laminated body obtained by the laminating step is enclosed in a laminate film outer package, stored for a predetermined period of time, and diffusing lithium metal into the negative electrode. In the negative electrode applying step, the coated area is separated from the boundary with the uncoated area. Provided to be a distance of 90 mm or less,
In the step of affixing the lithium metal, the lithium application region is 90 mm or less from the application region of the negative electrode active material.   7. The negative electrode application process according to claim 6, wherein in the negative electrode application step, an uncoated region is provided along a direction parallel to the side where the electrode is formed, and an active material is applied along the parallel direction. A method for producing a non-electrolyte electricity storage device, comprising: