JP4928828B2 - Lithium ion storage element - Google Patents

Description

  The present invention relates to a lithium ion storage element, and in particular, a laminated electrode body in which a positive electrode capable of inserting and extracting anions and a negative electrode capable of inserting and extracting lithium ions are alternately laminated with a separator interposed therebetween. It relates to what is used.

  In recent years, power storage means capable of rapid charging / discharging of relatively large electric energy has been required for load leveling in wind power generation, solar cells, etc., countermeasures for voltage sag and power failure, and energy regeneration in automobiles. It was.

  Conventionally, lithium ion secondary batteries that have high energy density and can be charged have been provided as power storage means. However, the lithium ion secondary battery is rapidly deteriorated in characteristics due to repeated charge and discharge, and has a limited number of charge / discharge cycles (lifetime). In addition, the time required for charging is long, and rapid charging as required by the energy regeneration is impossible. That is, there was a problem in charge / discharge characteristics. This is a problem common to all secondary batteries as well as lithium ion secondary batteries.

  If attention is paid only to the charge / discharge characteristics, the electric double layer capacitor is more suitable than the secondary battery. The charge / discharge characteristics of the electric double layer capacitor are superior to those of the secondary battery, and can be used without maintenance for a long period of time, and can be rapidly charged / discharged. However, the electric double layer capacitor can have a very large capacity (capacitance) as a capacitor, but the chargeable / dischargeable capacity is considerably inferior to that of the lithium ion secondary battery.

  Therefore, a lithium ion storage element having such characteristics as an electric double layer capacitor and a lithium ion secondary battery are proposed. This power storage element is configured using a positive electrode capable of occluding and releasing anions, a negative electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte containing a lithium salt (see Patent Documents 1 and 2). .

  In the above lithium ion secondary battery, a reversible process of charge and discharge is performed by exchanging lithium ions between the positive electrode and the negative electrode through a non-aqueous electrolyte using a composite oxide containing lithium as the positive electrode (for example, lithium cobaltate). Is done. On the other hand, in the lithium ion storage element, a reversible process of charging and discharging is performed by occlusion / release of electrolyte anions at the positive electrode and occlusion / release of lithium ions at the negative electrode.

  This lithium ion storage element has such a property that the lithium ion secondary battery and the electric double layer capacitor have both advantages. That is, the charge / discharge cycle characteristics are superior to each stage as compared with the lithium ion secondary battery, and the charge / discharge capacity (capacity capable of being charged / discharged) is greater than each stage of the electric double layer capacitor.

  This lithium ion storage element can be suitably used as a high-performance capacitor-type secondary battery, but it has a low maintenance burden and can be charged and discharged quickly. It can be suitably used as a power storage means for performing low power outage countermeasures, energy regeneration in automobiles, and the like.

  The lithium ion storage element is the same as a conventional lithium ion secondary battery in that an electrolyte containing lithium ions is used, but unlike a lithium ion secondary battery, a substance that supplies lithium ions to a positive electrode ( For example, lithium cobaltate) is not used, and charging and discharging are performed using anions and lithium ions present as electrolyte components in the electrolytic solution.

  The positive electrode occludes the electrolyte anion in the electrolyte during charging and releases it during discharge. The negative electrode occludes lithium ions (cations) in the electrolyte during charging and releases it during discharging. A reversible charging / discharging process is performed by reversible occlusion / release of these anions and lithium ions.

  Here, in order for the reversible process of charge / discharge to be performed efficiently without causing the gas generation reaction of the electrolyte, the negative electrode is covered over the entire range from the initial charge stage (or the final discharge stage) to the final charge stage (or the initial discharge stage). The potential needs to be stably fixed around the lithium potential. Therefore, the negative electrode is preliminarily occluded (doped) with lithium ions, so-called pre-occlusion (pre-doping).

  This pre-occlusion can be performed by arranging lithium metal in the electrolytic solution and electrically connecting the lithium metal to the negative electrode. In the lithium ion storage element having a structure using a stacked electrode body in which positive electrodes and negative electrodes are alternately stacked with a separator interposed therebetween, as shown in FIG. 2, a blank portion is provided on the surface of the negative electrode current collector 232, Conventionally, a foil-like lithium metal 41 is attached to the blank portion (Patent Documents 1 and 2).

  FIG. 2 shows a main part of a conventional lithium ion storage element. In the same figure, (a) shows the laminated electrode body 20, and (b) shows the negative electrode 23 in the laminated electrode body 20 taken out.

  In the laminated electrode body 20, rectangular seed-like positive electrodes 21 and negative electrodes 23 are alternately laminated with a separator 22 interposed therebetween. In the positive electrode 21, a positive electrode material 211 capable of occluding and releasing anions is disposed in layers on both surfaces of a sheet-like positive electrode current collector 212 made of a metal foil. In the negative electrode 23, a negative electrode material 231 capable of occluding and releasing lithium ions is disposed in layers on both surfaces of a sheet-like negative electrode current collector 232 made of a metal foil by coating or the like.

  Lead-shaped tabs 213 and 233 for connecting to external terminals are integrally formed on the current collectors 212 and 232 on the negative electrode side and the positive electrode side, respectively. The lithium metal 41 is stuck on the negative electrode current collector 232 in a thinly developed state. Thereby, the lithium metal 41 is conductively connected to the negative electrode 23.

By housing the laminated electrode body 20 in the element container together with the non-aqueous electrolyte, the lithium metal 41 is dissolved in the electrolyte as lithium ions and eventually inserted in the negative electrode 231.
JP 2000-21392 JP-A-9-147835

  It has been clarified by the present inventors that the above-described conventional lithium ion storage element has the following problems.

  (1) Although the production of the laminated electrode body is performed using a negative electrode on which lithium metal is adhered, this significantly impedes productivity. Lithium metal is highly reactive and requires special care when handling it. In particular, lithium metal in the state of being thinly developed in a foil shape is likely to react and is likely to ignite during the process. For this reason, the process after the installation of lithium metal requires special protective measures and reduces productivity. When lithium metal is bonded to the negative electrode current collector in advance, in addition to the increase in man-hours for the bonding, a series of processes including assembly of the subsequent laminated electrode bodies are greatly complicated, and productivity is hindered. End up.

  (2) It took a long time for the lithium metal to be dissolved in the non-aqueous electrolyte and stored as lithium ions throughout the negative electrode. This is presumably because lithium metal is placed in a state of being confined between the layers of the laminated electrode body. It has been found that the lithium metal placed in this state does not necessarily elute smoothly into the electrolyte, takes time to occlude in the negative electrode, and is difficult to uniformly occlude.

  The present invention has been made in view of the above problems, and its purpose is to interpose a separator between a positive electrode capable of occluding and releasing anions and a negative electrode capable of occluding and releasing lithium ions. However, in the lithium ion storage element using the rectangular laminated electrode body that is alternately laminated, the pre-occlusion of the lithium metal for pre-occlusion and the pre-occlusion of the lithium ion to the negative electrode are smoothly and rapidly performed, and the production process The purpose is to increase the productivity by reducing the frequency of handling lithium metal.

  Other objects and configurations of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  The solution provided by the present invention is as follows.

(1) A rectangular sheet-like positive electrode on which a positive electrode material capable of occluding and releasing anions is disposed on a positive electrode current collector, and a negative electrode material capable of occluding and releasing lithium ions are disposed on a negative electrode current collector. A rectangular sheet-like negative electrode having rectangular laminated electrode bodies alternately laminated with a separator interposed therebetween, a non-aqueous electrolyte solution in which lithium salt is dissolved, and the laminated electrode body are accommodated together with the non-aqueous electrolyte solution A lithium ion storage element including a hermetically sealed element container,
It has a strip-shaped conductive support that is installed so as to be parallel to the stacked end face of the stacked electrode body, and lithium metal that is attached along the side of the electrode body of the conductive support, and the lithium metal A lithium ion storage element, wherein the lithium ion storage element is conductively connected to the negative electrode of the electrode body through a conductive support.

  (2) In the means (1), the laminated electrode body is configured such that positive and negative terminal leads are drawn out from one side thereof, and the conductive support is formed on the four side sides of the laminated electrode body. Among them, it is installed so as to be parallel to and facing the laminated end surface of the three side sides excluding the lead side of the terminal lead, and the lithium metal is attached to face the laminated end surface of the three side sides. Lithium ion storage element characterized.

  In a lithium ion storage element using a rectangular laminated electrode body in which a positive electrode capable of occluding and releasing anions and a negative electrode capable of occluding and releasing lithium ions are alternately laminated with a separator interposed therebetween, Dissolution of the pre-occlusion lithium metal and pre-occlusion of lithium ions into the negative electrode can be performed smoothly and quickly, and the frequency of handling the lithium metal in the production process can be reduced to increase productivity.

 Operations / effects other than those described above will be apparent from the description of the present specification and the accompanying drawings.

FIG. 1 shows a first embodiment of a lithium ion storage element according to the present invention.
In the figure, (a) is a broken front view, and (b) is a cross-sectional view taken along line AA of (a). In the electric storage element 10 shown in the figure, an electrode body 20 in which a positive electrode 21 and a negative electrode 23 are opposed to each other through a separator 22 is hermetically accommodated in an element container 11 together with a nonaqueous electrolytic solution 24.

  The positive electrode 21 is formed by laminating a positive electrode material 211 using a carbon material capable of occluding and releasing anions on both surfaces of a sheet-like current collector 212 made of a metal foil (Al) by coating or the like, and the whole is a sheet. It is formed in a shape. Similarly, the negative electrode 23 has a negative electrode material 231 capable of occluding and releasing lithium ions attached to both surfaces of a sheet-like current collector 232 made of a metal foil (Cu) by coating or the like, and the whole is formed into a sheet shape. Is formed. The positive electrode 21 and the negative electrode 23 are sequentially stacked while sandwiching the separator 22 to form a rectangular flat stacked electrode body 20.

  The current collectors 212 and 232 are integrally formed with lead-like tabs 213 and 233 for connecting to external terminals, respectively. The tabs 213 of the positive electrode current collector 212 are commonly connected to each other and connected to the positive electrode terminal 31. Similarly, the tabs 233 of the negative electrode current collector 232 are commonly connected to each other and connected to the negative electrode terminal 33. The terminal lead is drawn out on one side of the four sides of the laminated electrode body 20. The positive electrode terminal 31 and the negative electrode terminal 33 are installed across the inside and outside of the element container 11 while keeping the sealed state of the element container 11.

  The positive electrode 21 occludes anions in the electrolyte during charging and releases them during discharging. The negative electrode 23 occludes lithium ions (cations) in the electrolyte during charging and releases it during discharging. A reversible charging / discharging process is performed by reversible occlusion / release of these anions and lithium ions. As the material for the positive electrode material 211 and the negative electrode material 231, a carbon material is suitable.

  The element container 11 is not particularly limited as long as it can stably and hermetically contain element components including the non-aqueous electrolyte 24, but in this embodiment, an airtight flexible packaging material such as a laminate film is rectangular by fusion or the like. Soft containers processed into bags are used. This soft container can be easily sealed by heat-sealing the opening. Sealing by thermal fusion can be performed in a state where the positive electrode terminal 31 and the negative electrode terminal 33 are sandwiched between the fusion portions.

  Furthermore, in the lithium ion storage element, the strip-like conductive support 25 made of metal foil faces parallel to the laminated end faces of the three sides of the four sides of the laminated electrode body 20 excluding the lead side of the terminal lead. It is installed along the way. A lithium metal 41 is attached along the side surface of the electrode body 20 of the conductive support 25. At the same time, one end of the conductive support 25 is welded to the inner portion of the element container 11 of the negative electrode terminal 33 via the connecting lead 26.

  In the lithium ion storage element described above, the lithium metal 41 for preocclusion is installed outside the laminated electrode body 20. Therefore, the laminated electrode body 20 can be produced in a state where no lithium metal is present. As a result, it is possible to largely avoid the increase in man-hours and the complexity of the process associated with the handling of lithium metal, thereby ensuring good productivity.

  Further, since the lithium metal 41 is not confined between the layers of the laminated electrode body 20 and is disposed outside the layer, the lithium metal 41 is smoothly and quickly dissolved in the electrolyte solution, and the electrolyte solution contains lithium ions as lithium ions. The diffusibility after dissolution becomes good, and thereby, lithium ions are uniformly distributed over the entire negative electrode in the electrode body 20 and quickly occluded.

  Furthermore, since the lithium metal 41 that is the lithium ion supply source is arranged along the laminated end face of the laminated electrode body 20, the lithium ions eluted from the lithium metal 41 are separated from each other in the laminated electrode body 20. Through 22, it reaches the negative electrode 23 of each layer simultaneously and is occluded. As a result, lithium ions can be preoccluded quickly and uniformly in the negative electrode 23 of each layer in the electrode body 20. Therefore, the pre-occlusion that conventionally required a long time can be performed in a significantly shorter time.

  Still further, the conductive support 25 is provided along the laminated end faces of the three side edges excluding the terminal lead drawing side edge among the four side edges of the laminated electrode body while facing in parallel and the laminated end face of the three side edges. On the other hand, the lithium metal 41 is arranged so that lithium ions eluted from the lithium metal 41 move into the electrode body 20 from the laminated end faces on the three sides of the laminated electrode body 20 respectively. Thereby, preliminary occlusion of lithium ions into the negative electrode 23 of each layer can be performed more rapidly and uniformly.

<Example>
Production of positive electrode: Graphite powder as a positive electrode material and carboxymethylcellulose (Daiichi Kogyo Kagaku Co., Ltd., Cellogen 4H) as a positive electrode material are mixed at a weight ratio of 97: 3, and ion-exchanged water is added thereto to form a paste. A mixture was prepared. This mixture was applied to both surfaces of a 20 μm thick aluminum foil serving as a current collector. This was dried and rolled, and then cut into a predetermined shape to produce a sheet-like positive electrode. The cut positive electrode also includes an uncoated portion that becomes a tab for connection with the positive electrode terminal.

  Production of negative electrode: A non-graphitizable carbon material (PIC manufactured by Kureha Chemical Co., Ltd.) which is a negative electrode material and a polyvinylidene fluoride resin (KF # 1100 of Kureha Chemical Co., Ltd.) which is a binder of 95: 5 It mixed by weight ratio, N-methyl-2-pyrrolidinone was added as a solvent to this, and the paste-form mixture was prepared.

  This mixture was applied to both sides of a 14 μm thick copper foil serving as a current collector. This was dried and rolled, and then cut into a predetermined shape to produce a sheet-like negative electrode. The cut negative electrode also includes an uncoated portion that becomes a tab for connection with the negative electrode terminal.

  Production of electrode body: The produced negative electrode and positive electrode are laminated with a polyolefin separator between them so that the uncoated part (tab) of the positive electrode and the uncoated part (tab) of the negative electrode do not overlap each other, and are rectangular A flat laminated electrode body was constructed. This electrode body was accommodated in an element container made of an aluminum laminate film.

  Device preparation: A nickel lead having a predetermined amount of lithium metal adhered thereto is placed in the device container. The nickel lead corresponds to the conductive support and is bent in a U shape along the inner surface of the element container. Lithium metal is stuck inside the U-shape.

  The laminated electrode body was inserted into the element container, and the uncoated portion (tab) of the positive electrode was bundled and welded to the positive electrode terminal. Similarly, the uncoated portion (tab) of the negative electrode was bundled and welded to the negative electrode terminal. Also, one end of the nickel lead was connected to the negative electrode terminal via a connecting lead.

  Thereafter, a non-aqueous electrolyte was poured into the container. And the opening part of the container was airtightly sealed by heat sealing | fusion in the state which made each one end side of a positive electrode terminal and a negative electrode terminal come out of a container, respectively. Thus, the lithium ion electrical storage element of the Example was produced (refer FIG. 1).

<Conventional example>
In contrast to the above example, nickel lead with lithium metal attached is not disposed, and instead, lithium metal is attached to the uncoated part (blank part) of the negative electrode current collector as shown in FIG. did. Other than that, a conventional lithium ion storage element was fabricated in the same manner as in the example.

<Test>
The electricity storage elements of the example and the conventional example were each left in a 45 ° C. thermostat and the time until the lithium metal was completely dissolved was measured. The result was 5 days for the example and 20 days for the conventional example.

  As mentioned above, although this invention was demonstrated based on the typical Example, this invention can have various aspects other than having mentioned above.

  In a lithium ion storage element using a rectangular laminated electrode body in which a positive electrode capable of occluding and releasing anions and a negative electrode capable of occluding and releasing lithium ions are alternately laminated with a separator interposed therebetween, Dissolution of the pre-occlusion lithium metal and pre-occlusion of lithium ions into the negative electrode can be performed smoothly and quickly, and the frequency of handling the lithium metal in the production process can be reduced to increase productivity.

1 is a cutaway front view and a side sectional view showing an embodiment of a lithium ion storage element according to the present invention. It is the sectional side view and perspective view which show the structural example of the conventional lithium ion electrical storage element.

Explanation of symbols

10 power storage elements, 11 element containers, 20 laminated electrode bodies,
21 positive electrode, 211 positive electrode material, 212 positive electrode current collector, 213 tab,
22 separator 23 negative electrode, 231 negative electrode material, 232 negative electrode current collector, 233 tab,
24 non-aqueous electrolyte, 25 conductive support, 26 connecting leads,
31 Positive terminal, 33 Negative terminal, 41 Lithium metal

Claims (2)

A rectangular sheet-shaped positive electrode in which a positive electrode material capable of occluding and releasing anions is installed on a positive electrode current collector, and a rectangular sheet shape in which a negative electrode material capable of occluding and releasing lithium ions is installed on a negative electrode current collector A rectangular laminated electrode body in which negative electrodes are alternately laminated with a separator interposed therebetween, a non-aqueous electrolyte solution in which lithium salt is dissolved, and the laminated electrode body together with the non-aqueous electrolyte solution are sealed A lithium ion storage element comprising a sealed element container,
It has a strip-shaped conductive support that is installed so as to be parallel to the stacked end face of the stacked electrode body, and lithium metal that is attached along the side of the electrode body of the conductive support, and the lithium metal A lithium ion storage element, wherein the lithium ion storage element is conductively connected to the negative electrode of the electrode body through a conductive support. 2. The laminated electrode body according to claim 1, wherein positive electrode and negative electrode terminal leads are drawn out from one side of the laminated electrode body, and the conductive support is the terminal lead among the four side edges of the laminated electrode body. Lithium ion, wherein the lithium metal is attached so as to face the laminated end surface of the three side sides excluding the lead side of the metal, while facing the laminated end surface of the three side sides. Power storage element.

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