JP2019047084A - Method for manufacturing power storage element - Google Patents

Abstract

To provide a method for manufacturing power storage element at low cost while ensuring the safety.SOLUTION: A method for manufacturing a power storage element 1 arranged by sealing an electrode body 10, in which a positive electrode 20 having a current collector 21 coated with a positive electrode material 22 capable of reversibly supporting lithium ions or anions, and a negative electrode 30 having a current collector 31 coated with a negative electrode material 32 capable of occluding and releasing lithium ions are opposed to each other through a separator 40, together with an electrolyte solution in an outer packaging body 11 comprises: a step (s9) of charging the power storage element causing the negative electrode to occlude lithium ions; an additive agent-preparation step (s4) of preparing an additive agent including a supply source of lithium ions to make the negative electrode occlude; and steps (s5, s7) of introducing the additive agent into the outer packaging body. In the additive agent-preparation step, a lithium halide is used as the lithium ion supply source, and the lithium halide is dissolved in a solvent to prepare the additive agent.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method of manufacturing a storage element. Specifically, the present invention relates to a method of manufacturing a storage element of a type in which lithium ions are stored in advance in a negative electrode.

  A storage element capable of charging and discharging includes a positive electrode configured to contain a material capable of reversibly supporting lithium ions or anions, and a negative electrode configured to include a material capable of inserting and extracting lithium ions. An electrode body having an electrolytic solution containing a lithium salt and having a positive electrode and a negative electrode disposed opposite to each other with a separator interposed therebetween is hermetically sealed together with the electrolytic solution in an outer package. Then, there is a negative electrode in which lithium ions are stored (hereinafter, also referred to as pre-doping) in advance. As a storage element (hereinafter, also referred to as a pre-doped storage element) of a type in which lithium ions are pre-doped to the negative electrode, there is one called a lithium ion capacitor. In the lithium ion capacitor, the positive electrode forms an electric double layer and is charged and discharged by physical action, whereas the negative electrode is charged and discharged by the redox reaction of lithium.

In the pre-doped storage element, the potential V (vs Li / Li ⁺ ) of the negative electrode is lowered by pre-doping lithium ions in the negative electrode, and the cell voltage, which is the potential difference between the positive and negative electrodes, can be increased. It is something that can be obtained. In addition, the lithium ion capacitor is capable of rapid charging as well as the known electric double layer capacitor. The pre-doped storage element is expected to be used for load leveling devices for wind power generation, instantaneous interruption countermeasure devices, storage applications of regenerative power in automobiles, and the like.

  The positive electrode and the negative electrode constituting the pre-doped storage element are produced, for example, by applying a slurry-like electrode material containing an electrode active material on the surface of a flat current collector. In the pre-doped type storage element, an electrode body of one layer in which a positive electrode and a negative electrode are disposed opposite to each other with a separator interposed, or an electrode body of multiple layers in which a plurality of electrode bodies are stacked is enclosed in an outer package together with an electrolytic solution. It is a thing.

  There are roughly two types of pre-doped storage elements according to the method of pre-doping lithium ions to the negative electrode. In a pre-doping system in one type of storage element, a current collector having a mesh-like hole formed in at least one of a positive electrode and a negative electrode is used on the outer surface side of the uppermost or lowermost layer of the laminated electrode assembly. Metallic lithium is adhered, and lithium ions originating from the metallic lithium are absorbed in the negative electrode through the holes of the current collector. In addition, the following patent document 1 is described about the electrical storage element which employ | adopted this system.

  In the pre-doping method of the other type of storage element, in the sheet-like current collector, metal lithium is disposed on the same surface as the surface to which the negative electrode material is applied, and lithium ions are applied to the surface of the current collector It is made to occlude to a negative electrode along. In addition, about this kind of electrical storage element, it describes, for example in the following patent document 2 grade | etc.,.

Patent No. 348593 JP, 2009-295400, A

  The conventional pre-doped storage element uses metallic lithium as a source of lithium ions to be pre-doped to the negative electrode. As is well known, metallic lithium is a water-free substance and reacts explosively to water. Therefore, in the production of the pre-doped storage element, it is necessary to strictly control the handling of metallic lithium to ensure safety. Furthermore, metallic lithium is in the form of a foil, very light and easy to deform. Therefore, it is difficult to accurately align metal lithium at a required position, or to attach metal lithium to the position so as to be in a flat state. Further, in a pre-doped storage element using a current collector in which a hole is formed, there is a problem that the cost of the current collector itself is high. In addition, since a complicated process of applying the electrode material to the current collector provided with the holes is required, it is more difficult to reduce the manufacturing cost.

  Therefore, an object of the present invention is to provide a method for manufacturing a storage element at low cost while securing safety.

In one aspect of the present invention for achieving the above object, there is provided a positive electrode comprising a current collector on which a positive electrode material capable of reversibly supporting lithium ions or anions is applied, and a lithium ion occluded on the current collector. A storage element comprising: an anode coated with a releasable anode material; and an electrode body in which the cathode and the anode are disposed opposite to each other with a separator interposed therebetween, and an electrolyte solution enclosed in an outer package. A manufacturing method,
A pre-doping step in which lithium ions are stored in advance in the negative electrode by charging the storage element after the electrode body and the electrolytic solution are enclosed in the outer package;
An additive preparation step of preparing an additive including a lithium ion supply source stored in advance in the negative electrode;
An additive introducing step of introducing the additive into the outer package;
Including
In the additive preparation step, lithium halide is used as a lithium ion supply source, and the lithium halide is dissolved in a solvent to prepare the additive.
The method is a method of manufacturing a storage element characterized by

  In the additive preparation step, N, N-dimethylformamide can be used as the solvent. Alternatively, dimethyl sulfoxide may be used as the solvent.

  Then, in the additive introduction step, the additive may be added to the electrolytic solution, and the electrolytic solution may be stored in the outer package.

  According to the method of manufacturing a storage element of the present invention, a storage element of a type in which lithium ions are stored in the negative electrode in advance can be manufactured more inexpensively while securing safety.

It is a figure which shows an example of the electrical storage element produced by the manufacturing method of the electrical storage element which concerns on the Example of this invention. It is a figure which shows the procedure of the manufacturing method of the electrical storage element which concerns on the Example of this invention.

=== Technical thought ===
As described above, in the conventional pre-doping type storage element, lithium ion is pre-doped to the negative electrode using metallic lithium which is difficult to handle at the time of manufacture. And in the manufacturing method of the conventional electrical storage element, it was difficult to manufacture a pre-doping type | mold electrical storage element at low cost, ensuring safety | security. So, in the manufacturing method of the electrical storage element which concerns on the Example of this invention, it is presupposed that a lithium ion is pre-doped to a negative electrode, without using the metal lithium which handling is difficult. Specifically, the method of manufacturing the storage element according to the embodiment of the present invention comprises using any lithium compound to be decomposed by a chemical reaction in the negative electrode or the positive electrode as a source of lithium ions to be pre-doped (hereinafter also referred to as lithium ion source). By using it, it is based on the technical idea that manufacturing cost is reduced while securing safety. Furthermore, in the method of manufacturing the storage element according to the embodiment of the present invention, the technical idea is to further reduce the manufacturing cost of the storage element by pre-doping the lithium compound together with the electrode body and the electrolyte only by sealing in the outer package. include.

  And, in the method of manufacturing the storage element according to the embodiment of the present invention based on the above technical idea, lithium halide (lithium chloride, lithium bromide, lithium iodide, lithium fluoride etc.) is used as a lithium ion source, and further It is characterized in that lithium ions from the lithium source are pre-doped in a simpler procedure. And below, the procedure which manufactures the electrical storage element by which the electric power generation element which consists of an electrode body and electrolyte solution is accommodated in the exterior body which consists of a laminate film as an Example of this invention is mentioned.

=== Structure of Storage Element ===
The structure of the electrical storage element 1 produced by the method which concerns on FIG. 1 at the Example of this invention was shown. FIG. 1A is a perspective view showing the appearance of the storage element 1, and FIG. 1B is an exploded perspective view of the storage element 1. The illustrated storage element 1 has a flat external appearance as shown in FIG. 1A, and a power generation element is enclosed in a flat rectangular bag-like exterior body 11 made of a laminate film. Further, in the storage element 1 shown here, the positive electrode terminal plate 23 and the negative electrode terminal plate 33 are drawn outward from one side 13 of the rectangular outer package 11.

  Next, the structure of the storage element 1 will be described with reference to FIG. 1 (B). In FIG. 1B, some members and portions are hatched to make it easy to distinguish them from other members and portions. As shown in FIG. 1 (B), the exterior body 11 is a rim of the rectangular aluminum laminate film (11a, 11b) which is overlapped with each other and shown by hatching or dotted frame in the figure. Region 12 is welded by thermocompression bonding to seal the inside. In the exterior body 11, an electrode body 10 in which a sheet-like positive electrode 20 and a sheet-like negative electrode 30 are laminated via a separator 40 is enclosed together with an electrolytic solution. One ends of the strip-like positive electrode terminal plate 23 and the negative electrode terminal plate 33 are connected to the positive electrode current collector 21 and the negative electrode current collector 31 by a method such as ultrasonic welding. The other ends of the positive electrode terminal plate 23 and the negative electrode terminal plate 33 are exposed to the outside of the exterior body 11. And in the manufacturing method of the electrical storage element 1 which concerns on the Example of this invention, the lithium ion which used lithium halide as lithium source is pre-doped to the negative electrode 30 for electrolyte solution. Also, in order to ensure that the necessary amount of lithium source is dissolved in the electrolytic solution, the lithium source is introduced into the exterior body 11 in a state of being dissolved in a predetermined solvent.

=== First Example ===
As a method of manufacturing a storage element according to the first embodiment of the present invention, a manufacturing procedure of a pre-doped storage element (hereinafter also referred to as a storage element) using lithium chloride as a lithium source will be described. FIG. 2 shows the procedure of the method of manufacturing the storage element 1 according to the first embodiment. Hereinafter, this procedure will be described with reference to FIGS. 2 and 1.

First, the positive electrode 20 and the negative electrode 30 constituting the electrode body 10 are manufactured (s1). For the positive electrode 20, activated carbon was used as a positive electrode active material, and a conductive agent, a thickener, and acetylene black, carboxymethyl cellulose, and an acrylic binder were used as a binder. The preparation procedure of the positive electrode 20 will be described below. First, the positive electrode active material, the conductive agent, the thickener, and the binder were mixed at a ratio of 88 wt%, 6 wt%, 3 wt%, and 3 wt%, respectively, and pure water was added and mixed thereto. The positive electrode mixture was used as the positive electrode material 22. The positive electrode material 22 was applied onto the positive electrode current collector 21 made of aluminum foil at a basis weight of 45 g / m ^{2, and} the positive electrode current collector 21 coated with the positive electrode material 22 was punched into 30 mm long and 50 mm wide. Furthermore, the positive electrode current collector 21 to which the positive electrode material 22 was applied was dried to complete the positive electrode 20. Here, after the positive electrode current collector 21 to which the positive electrode material 22 is applied is naturally dried, for example, it is vacuum dried at a temperature of about 100 ° C. to 200 ° C. for about 12 hours.

For the negative electrode 30, pitch coat carbon black was used as a negative electrode active material, and a conductive agent, a thickener, and acetylene black, carboxymethyl cellulose, and styrene butadiene rubber were used as a binder. Then, the negative electrode active material, the conductive agent, the thickener, and the binder were mixed at a ratio of 88 wt%, 5 wt%, 4 wt%, and 3 wt%, respectively, and pure water was added and mixed thereto. The negative electrode mixture was used as the negative electrode material 32. Next, the negative electrode material 32 was applied onto the negative electrode current collector 31 made of copper foil at a basis weight of 21 g / m ² . Further, the negative electrode current collector 31 to which the negative electrode material 32 was applied was punched into a length of 32 mm and a width of 52 mm, and then dried by the same drying process as the positive electrode to complete the negative electrode 30.

  The positive electrode 20 and the negative electrode 30 produced in the above-described procedure were stacked via the separator 40 to produce the electrode assembly 10 (s2). As the separator 40, for example, a microporous film made of polyolefin or the like, a woven fabric, and a non-woven fabric can be used. Here, a separator 40 made of polyolefin non-woven fabric was employed. The positive electrode terminal plate 21 is applied to the positive electrode current collector 21 and the negative electrode current collector 31 at appropriate times such as before the positive electrode material 22 and the negative electrode material 32 are applied, or when preparation of the positive electrode 20 and the negative electrode 30 is completed. 23 and the negative electrode terminal plate 33 are attached.

An additive containing an electrolytic solution and a lithium source was produced in parallel with or before or after the procedure from the production step (s1) of the electrodes (20, 30) to the assembly step (s2) of the electrode assembly 10. An electrolytic solution was prepared by dissolving LiPF ₆ at a concentration of 1.2 M in a solvent of propylene carbonate (s3). Further, a solution in which lithium chloride as a lithium source was dissolved in N, N-dimethylformamide (DMF) as a solvent was prepared as an additive (s4). Here, 1 g of lithium chloride was dissolved in 13 mL of DMF. Then, an electrolytic solution adjusting step (s5) of adding 35.7 μL of the additive to 0.4 mL of the electrolytic solution was performed. After producing the power generation element including the electrode body 10 and the electrolytic solution to which the additive was added After the power generation element was housed in an exterior body 11 made of a laminate film prepared separately, the exterior body 11 was sealed (s6, s7). In addition, as a procedure which accommodates an electric power generation element in the exterior body 11, and seals the exterior body 11, for example, three sides of two rectangular laminate films (11a, 11b) which were made to face each other are welded, A bag-like exterior body 11 having an opening 13 is produced, the electrode body 10 is housed together with the electrolytic solution in the bag-like exterior body 11, and one side 13 opened in the bag-like exterior body 11 is sealed. The procedure can be adopted.

  Next, the aging process (s8) was first performed with respect to the electrical storage element 1 assembled by the procedure (s1-s7) mentioned above. In the aging step (s8), the assembled storage element 1 is allowed to stand for 7 days in a 25 ° C. constant temperature bath, and then the end cell voltage is 3.5 V and charged for 24 hours with 10 mA constant current and constant voltage The charge and discharge cycle of rest for 24 hours and spontaneous discharge was repeated twice. Then, the storage element 1 after the aging step (s8) is charged, and the pre-doping step (s9) of allowing the negative electrode 30 to occlude lithium ions is carried out. Completed. In the pre-doping step (s9), charging was performed in a 25 ° C. constant temperature bath at a constant current of 10 mA and a constant voltage for 24 hours until the end cell voltage of 3.5 V was reached.

<Confirmation of pre-doping>
In order to confirm whether lithium ions are pre-doped in the negative electrode of the storage element produced by the method according to the first embodiment described above, the storage element produced by the method of the first example and the additive are used An electric storage element manufactured without using an electric storage element, an electric storage element manufactured using an additive containing no lithium compound, an electric storage element manufactured using an additive containing a lithium compound other than lithium halide is used as a sample, and the state of pre-doping in each sample I examined.

  Table 1 below shows the manufacturing conditions of each sample.

表１において、サンプル１は第１の実施例に係る方法で作製した蓄電素子である。サンプル２は、電解液にリチウム源とその溶媒が含まれておらず、サンプル３は電解液にリチウム源の溶媒であるＤＭＦのみが含まれている。また、サンプル４は、リチウムアセチルアセトナートをＤＭＦに溶解させて得た溶液を添加剤として使用したものである。ここでは、図２における添加剤作製工程（ｓ４）において、１ｇのリチウムアセチルアセトナートを２０ｍＬのＤＭＦに溶解させて添加剤を作製し、電解液調整工程（ｓ５）では、０．４ｍＬの電解液に１３２．８μＬの添加剤を添加した。サンプル５は、クエン酸リチウムをＤＭＦに溶解させて得た溶液を添加剤として使用したものであり、添加剤作製工程（ｓ４）において、１ｇのクエン酸リチウムを２０ｍＬのＤＭＦに溶解させて添加剤を作製した。電解液調整工程（ｓ５）では、０．４ｍＬの電解液に２７２．２μＬの添加剤を添加した。また、サンプル２〜５に対しても、サンプル１と同様にしてエージング工程（ｓ８）とプレドープ工程（ｓ９）とを実行した。そして、プレドープ工程（ｓ９）後の各サンプルの負極電位を測定した。

In Table 1, Sample 1 is a storage element manufactured by the method according to the first embodiment. The sample 2 contains no lithium source and its solvent in the electrolyte, and the sample 3 contains only DMF, which is a solvent for the lithium source, in the electrolyte. Sample 4 is a solution obtained by dissolving lithium acetylacetonate in DMF as an additive. Here, in the additive preparation step (s4) in FIG. 2, 1 g of lithium acetylacetonate is dissolved in 20 mL of DMF to prepare an additive, and in the electrolytic solution adjusting step (s5), 0.4 mL of the electrolytic solution Add 132.8 μL of the additive. Sample 5 uses a solution obtained by dissolving lithium citrate in DMF as an additive, and in the additive preparation step (s4), 1 g of lithium citrate is dissolved in 20 mL of DMF to be an additive Was produced. In the electrolyte adjustment step (s5), 272.2 μL of the additive was added to 0.4 mL of the electrolyte. The aging step (s8) and the pre-doping step (s9) were also performed on samples 2 to 5 in the same manner as in sample 1. Then, the negative electrode potential of each sample after the pre-doping step (s9) was measured.

  Table 2 shows the negative electrode potential of each sample.

表２に示したように、第１の実施例の方法で作製したサンプル１におけるセル電圧に対する負極の電位（以下、負極電位とも言う）は０．２Ｖ（ｖｓ Ｌｉ/Ｌｉ^＋）であった。一方、他のサンプル２〜５の負極電位は、０．７Ｖ（ｖｓ Ｌｉ/Ｌｉ^＋）であり、サンプル１の負極電位に対して０．５Ｖ高かった。以上より、サンプル１ではリチウムイオンが負極３０にプレドープされ、そのプレドープにより負極電位が０．５Ｖ低下することが確認できた。また、塩化リチウム以外のリチウム化合物を添加剤に用いたサンプル４とサンプル５では、サンプル２やサンプル３と同様に負極電位が０．７Ｖ（ｖｓ Ｌｉ/Ｌｉ^＋）であり、プレドープされていないことが確認できた。すなわち、リチウム源としてハロゲン化リチウムの一つである塩化リチウムを用いることで負極３０にリチウムイオンをプレドープさせることが可能であること、およびハロゲン化リチウム以外のリチウム化合物を添加剤に用いてもプレドープできないことが確認できた。

As shown in Table 2, the potential of the negative electrode (hereinafter also referred to as negative electrode potential) with respect to the cell voltage in sample 1 manufactured by the method of the first embodiment was 0.2 V (vs Li / Li ⁺ ). On the other hand, the negative electrode potentials of the other samples 2 to 5 were 0.7 V (vs Li / Li ⁺ ), and were 0.5 V higher than the negative electrode potential of the sample 1. From the above, it was confirmed that lithium ions were pre-doped to the negative electrode 30 in sample 1, and the potential of the negative electrode was lowered by 0.5 V due to the pre-doping. Moreover, in sample 4 and sample 5 using lithium compounds other than lithium chloride as an additive, the negative electrode potential is 0.7 V (vs Li / Li ⁺ ) as in sample 2 and sample 3, and they are not pre-doped Was confirmed. That is, by using lithium chloride which is one of lithium halides as a lithium source, it is possible to pre-dope lithium ions on the negative electrode 30, and even if a lithium compound other than lithium halide is used as an additive I could confirm that I could not do it.

=== Second Example ===
As described above, in the pre-doping step (s9) performed on samples 1 to 5 shown in Table 1, the end cell voltage was 3.5 V. This is because, in Samples 2 and 3 in which a lithium source is not introduced, lithium ions are not pre-doped on the negative electrode, and there is a possibility that the positive electrode may be oxidized and decomposed if charging is performed with an end cell voltage higher than 3.5 V This is because the. Then, in the sample in which the positive electrode is oxidatively decomposed, there is no reliability in the value of the negative electrode potential after the pre-doping step (s9), and it is confirmed that the pre-doping can be performed by the method of manufacturing the storage element according to the first embodiment. become unable. However, from the results shown in Table 1, it can be confirmed that pre-doping is possible by the method of the first embodiment. Therefore, the procedure for producing the storage element 1 by performing the pre-doping step (s9) at a termination cell voltage higher than 3.5 V is referred to as a method for producing the storage element according to the second embodiment of the present invention.

Specifically, the pre-doped storage element including the positive electrode material 22 and the negative electrode material 32 used in the method of manufacturing the storage element according to the first embodiment is the same as the lithium ion capacitor except for the form of the lithium source. And operate by the same charge / discharge reaction as a lithium ion capacitor. Further, in the lithium ion capacitor, when the lithium ion is pre-doped by an amount capable of being occluded by the negative electrode 30, the cell voltage becomes 3.8V. Therefore, in the method of manufacturing a storage element according to the second embodiment, the storage element after assembly is charged at a termination cell voltage of 3.8 V in the pre-doping step (s9) in the manufacturing procedure of the storage element shown in FIG. I decided. Then, when the negative electrode potential of the storage element after the pre-doping step (s9) was examined, it became a negative electrode potential of 0 V (vs Li / Li ⁺ ), and lithium ions of an amount that can theoretically be absorbed by the negative electrode 30 are actually pre-doped. It was confirmed that it was done.

=== Third Example ===
Next, as a method of manufacturing the storage element according to the third embodiment of the present invention, in the additive preparation step (s4) in the preparation procedure of the storage element shown in FIG. A procedure for manufacturing a storage element by changing the addition amount is described. In the method of manufacturing a storage element according to the first and second embodiments, a solution obtained by dissolving 1 g of lithium chloride in 13 mL of DMF is used as an additive, and 35.7 μL of the additive is 0.4 mL of an electrolyte In the third example, various storage elements different in the addition amount of the additive to 0.4 mL of the electrolytic solution were manufactured as samples. In the method of manufacturing the storage element according to the third embodiment, the pre-doping step (s9) is performed at a termination cell voltage of 3.8 V as in the second embodiment. Then, the negative electrode potential of the sample was examined for the storage element after the pre-doping step (s9).

  The following Table 3 shows the additive amount of the additive and the negative electrode potential after the pre-doping step (s9) in the sample produced by the method of the third example.

表３において、サンプル６は、第２の実施例の方法で作製した蓄電素子であり、負極電位は、０．０Ｖ（ｖｓ Ｌｉ／Ｌｉ^＋）である。そして、表３に示したように、電解液に対する添加剤の添加量が少ないサンプルほど負極電位が高くなっている。しかし、表３に示した全てのサンプル６〜１０は、プレドープされていない場合のサンプル（表１、サンプル２〜サンプル５）の負極電位である０．７Ｖ（ｖｓ Ｌｉ／Ｌｉ^＋）よりも低い負極電位を示した。以上により、リチウム源として塩化リチウムを含む添加剤を外装体内に導入すれば、導入されたリチウム源の量に対応するリチウムイオンが確実に負極にプレドープされることが確認できた。

In Table 3, sample 6 is a storage element produced by the method of the second embodiment, and the negative electrode potential is 0.0 V (vs Li / Li ⁺ ). And, as shown in Table 3, the negative electrode potential is higher as the amount of the additive added to the electrolytic solution is smaller. However, all the samples 6 to 10 shown in Table 3 are lower than 0.7 V (vs Li / Li ⁺ ) which is the negative electrode potential of the sample (Table 1, samples 2 to 5) when not pre-doped. The negative electrode potential is shown. As mentioned above, when the additive containing lithium chloride as a lithium source is introduce | transduced in an exterior body, it has confirmed that the lithium ion corresponding to the quantity of the lithium source introduce | transduced was reliably pre-doped by the negative electrode.

=== Fourth and fifth embodiments ===
In the first to third embodiments, lithium chloride is used as lithium halide serving as a lithium source, and DMF is used as a solvent for dissolving the lithium source. Therefore, in the method of manufacturing the storage element according to the fourth embodiment of the present invention, lithium halide other than lithium chloride is used as a lithium source in the additive preparation step (s4) of the preparation procedure of the storage element shown in FIG. I decided to use it. In addition, in the method of manufacturing the storage element according to the fifth example, dimethyl sulfoxide (DMSO) is used as a solvent of lithium chloride in place of DMF as a solvent for lithium chloride in the additive preparation step (s4). Then, the storage element 1 shown in FIG. 1 was produced as a sample by the method according to the fourth and fifth examples, and the negative electrode potential of each sample was measured. In the pre-doping step (s9), the final cell voltage was 3.8 V.

  Table 4 shows preparation conditions and negative electrode potentials of the samples manufactured by the methods of the fourth and fifth examples.

表４では第２の実施例の方法で作製したサンプル６の製造条件と負極電位も示した。表４に示したように、塩化リチウム以外のハロゲン化リチウムである臭化リチウムをリチウム源としたサンプル１１、およびリチウム源の溶媒としてＤＭＳＯを用いたサンプル１２においても、負極電位が０．７Ｖ（ｖｓ Ｌｉ／Ｌｉ^＋）よりも低く、プレドープされていることが確認できた。

Table 4 also shows the production conditions of the sample 6 produced by the method of the second embodiment and the negative electrode potential. As shown in Table 4, in the sample 11 using lithium bromide which is a lithium halide other than lithium chloride as a lithium source and the sample 12 using DMSO as a solvent of the lithium source, the negative electrode potential is 0.7 V ( It can be confirmed that it is pre-doped, which is lower than vs. Li / Li ⁺ ).

  From the above, it was found that not only lithium chloride but also lithium bromide can be used as a lithium source. Of course, since lithium chloride and lithium bromide can be used as a lithium source, it can be easily imagined that other lithium halides such as lithium iodide and lithium fluoride can be used as a lithium source. That is, it is considered that any compound represented by LiX with X as a halogen atom can be used as a lithium source.

  In the embodiment of the present invention, in order to introduce lithium halide into the outer package, an additive is prepared by dissolving lithium halide in a solvent, and an electrolytic solution to which the additive is added together with the electrode body It is housed in the exterior body. This is because, if lithium halide is added as it is to the electrolytic solution, not all of the lithium halide is dissolved in the electrolytic solution, and a target amount of lithium ions may not be pre-doped on the negative electrode. Therefore, in the method of manufacturing a storage element according to the embodiment of the present invention, it is necessary to prepare an additive using a solvent capable of dissolving lithium halide. And, DMF and DMSO are known to dissolve many compounds, and it has been confirmed that DMF and DMSO can be used as a solvent for the additive. In other words, if an additive is prepared using a solvent capable of dissolving lithium halide, not limited to DMF or DMSO, and the additive is introduced into the package, lithium ion derived from lithium halide can be produced. It is believed that the negative electrode can be pre-doped.

  It is also known that DMF and DMSO can be mixed in an organic solvent at any ratio. Then, in the method of manufacturing the storage element according to the embodiment of the present invention, lithium halide is electrolyzed by mixing DMF or DMSO containing lithium halide as a solute with a solvent (propylene carbonate) constituting the electrolytic solution. It is dissolved in the solution. In addition, since lithium halide has strong polarity, it is preferable to use what has polarity as a solvent of lithium halide. In addition, since the storage element manufactured by the method of each embodiment uses lithium ion for charge and discharge reaction, it operates at a cell voltage higher than the voltage at which water decomposes, so lithium halide can be used. It is preferred to use an aprotic solvent which is not electrolyzed by high cell voltage. And, as a polar aprotic solvent, there are, for example, acetonitrile and the like in addition to DMF and DMSO.

=== Sixth Example ===
The storage element manufactured by the method according to the first to fifth examples uses a carbon-based material as the positive electrode active material, as in the lithium ion capacitor. Of course, the positive electrode active material is not limited to the carbon-based material. For example, it is also conceivable to use, as the positive electrode active material, a ternary active material (Li (Ni-Mn-Co) O ₂ ) containing cobalt, nickel, and manganese used in lithium secondary batteries and the like.

  The ternary active material has a large capacity per unit mass, has excellent thermal stability, and is highly safe. And the electric potential of the positive electrode using a ternary active material is 4.2V. Therefore, when a pre-doped storage element is manufactured using a ternary active material as a positive electrode, the electric capacity of the storage element can be increased. Therefore, as a method of manufacturing an electricity storage device according to the sixth embodiment, a procedure of manufacturing the electricity storage device in the same procedure as the method of the first to fifth embodiments while using a ternary active material as the positive electrode active material Give Hereinafter, a method of manufacturing a storage element according to the sixth embodiment will be described with reference to FIGS. 1 and 2.

First, the positive electrode 20 and the negative electrode 30 are produced in the electrode production step (s1). For the positive electrode 20, 90 wt%, 5 wt% and 5 wt% of the above-mentioned ternary active material, acetylene black as a conductive agent, and polyvinylidene difluoride (PVDF) binder as a binder, respectively The positive electrode material 22 obtained by mixing in a ratio and adding and mixing N-methyl-2 pyrrolidone thereto was coated on a positive electrode current collector 21 made of aluminum foil with an electrode weight of 191 g / m ² . Then, the positive electrode current collector 21 to which the positive electrode material 22 is applied is punched into 17 mm long and 17 mm wide, and the positive electrode current collector 21 to which the positive electrode material 22 is applied is the first embodiment described above. The positive electrode 20 was completed by drying in the same manner.

As for the negative electrode 30, pure water is prepared by mixing 97 wt% of graphite which is a negative electrode active material, 1.5 wt% of carboxymethyl cellulose which is a thickener, and 1.5 wt% of styrene butadiene rubber which is a binder. Was added to obtain a slurry-like negative electrode material 32. And this negative electrode material 32 was apply | coated on the negative electrode collector 31 which consists of copper foils with an electrode fabric weight of 93 g / m < ² >. Subsequently, the negative electrode current collector 31 to which the negative electrode material 32 was applied was punched out to a length of 18 mm and a width of 18 mm, and then dried in the same manner as the positive electrode 20 to complete the negative electrode 30.

  In the electrode assembly step (s2), the positive electrode 20 and the negative electrode 30 were laminated via a separator 40 made of a non-woven fabric of polyolefin to produce an electrode assembly 10. The positive electrode terminal plate 23 and the negative electrode terminal plate 33 may be attached to the positive electrode current collector 21 and the negative electrode current collector 31 at appropriate times.

In the electrolytic solution preparation step (s3), an electrolytic solution was prepared by dissolving LiPF ₆ at a concentration of 1.2 M in a solvent adjusted such that the volume ratio of ethylene carbonate and ethyl methyl carbonate is 1: 2. In the additive preparation step (s4), an additive is prepared by dissolving 1 g of lithium chloride in 13 mL of DMF, and in the electrolytic solution adjusting step (s5), 5 μL of the additive is added to 0.4 mL of the electrolytic solution did. Then, the electrode body 10 and the electrolytic solution were sealed in the exterior body 11 (s6, s7).

  In the aging step (s8), the storage element 1 assembled according to the previous procedure (s1 to s7) is allowed to stand in a 25 ° C. constant temperature bath for 4 days, and then the storage element 1 is stopped at a constant current of 1 mA. The cell voltage was charged to 4.2 V, and then the charged storage element 1 was discharged to an end cell voltage of 2.5 V. In the actual method of manufacturing the storage element 1, the pre-doping step (s9) is performed following the aging step (s8), but here, the storage element 1 after the aging step (s8) has been performed is sampled The charge capacity and the discharge capacity were determined based on the time taken for constant current charging and constant current discharging at 1 mA in the aging step (s8). In addition, in order to evaluate the capacity characteristics of the sample manufactured by the method of the sixth embodiment, the procedure (s1 to s8) up to the aging step is the same as the sixth embodiment except that no additive is used. The storage element 1 manufactured by the method was prepared as a sample according to a comparative example. The storage element 1 manufactured without using the additive operates as a lithium secondary battery.

  Table 5 below shows the preparation conditions and capacitance characteristics of the sample manufactured by the method of the sixth example and the sample according to the comparative example.

表５において、サンプル１３が第６の実施例の方法で作製した蓄電素子１であり、サンプル１４が比較例に係るサンプルである。サンプル１３は、充電容量が７．７５ｍＡｈで、放電容量が７．７１ｍＡｈであった。一方、サンプル１４では、充電容量が６．３５ｍＡｈで、放電容量が６．３１ｍＡｈであった。そして、サンプル１３の方が充電容量と放電容量が、サンプル１４の充電容量と放電容量に対して大きくなったことについては、サンプル１４では、充放電容量に寄与するリチウムイオンが、正極２０を構成する三元系活物質に含まれているリチウムを起源としたものだけであり、サンプル１３では、リチウムイオンが、三元系活物質に含まれているリチウムを起源としたものに、エージング工程（ｓ８）における定電流充電によってハロゲン化リチウムを起源として負極にプレドープされたものが加わったためと考えることができる。すなわち、サンプル１３とサンプル１４の容量の差は、負極にプレドープされたリチウムイオンの量に対応しているものと考えることができる。

In Table 5, the sample 13 is the storage element 1 manufactured by the method of the sixth embodiment, and the sample 14 is a sample according to a comparative example. Sample 13 had a charge capacity of 7.75 mAh and a discharge capacity of 7.71 mAh. On the other hand, in the sample 14, the charge capacity was 6.35 mAh and the discharge capacity was 6.31 mAh. Then, with regard to the fact that the charge capacity and the discharge capacity of the sample 13 are larger than the charge capacity and the discharge capacity of the sample 14, in the sample 14, the lithium ions contributing to the charge and discharge capacity constitute the positive electrode 20. In the sample 13, the lithium ions contained in the ternary active material were caused to originate from the lithium contained in the ternary active material. It can be considered that the constant current charge in s8) added the pre-doped one to the negative electrode originating from lithium halide. That is, it can be considered that the difference between the capacities of the sample 13 and the sample 14 corresponds to the amount of lithium ions pre-doped to the negative electrode.

=== Other Examples ===
The structure of the electrical storage element produced by the manufacturing method which concerns on the Example of this invention is not restricted to what was mentioned above. That is, various members and materials constituting the positive electrode and the negative electrode (current collector, electrode active material, conductive agent, thickener, binder), separator, and electrolytic solution are not limited to those described above.

  For example, as the conductive agent, carbon black or the like can be used besides acetylene black. As the binder, acrylic, polytetrafluoroethylene, polyvinylidene fluoride and the like can be used. A stainless steel lath plate or the like can also be used for the positive electrode current collector. As the negative electrode active material, various carbon materials capable of inserting and extracting lithium can be used. For example, pyrolytic carbons, cokes, graphites (such as artificial graphite and natural graphite), organic polymer compound combustion bodies, carbon fibers and the like can be used.

The electrolytic solution is one in which a lithium salt such as LiPF ₆ is dissolved in a non-aqueous solvent, and the non-aqueous solvent includes a high dielectric constant solvent and a low viscosity solvent. Although propylene carbonate, which is a high dielectric constant solvent, is used as a solvent for the electrolytic solution in the above embodiment, a solvent obtained by mixing a high dielectric constant solvent and a low viscosity solvent can also be used. As the high dielectric constant solvent, in addition to propylene carbonate, there are cyclic carbonates such as ethylene carbonate and butylene carbonate. And these high dielectric constant solvents may be used by one type, and may be used in combination of 2 or more types.

  As the low viscosity solvent, linear carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, Ethers such as 1,2-dibutoxyethane and lactones such as γ-butyrolactone can be mentioned. These low viscosity solvents may be used alone or in combination of two or more. Then, as the solvent of the electrolytic solution, a combination of a solvent arbitrarily selected from each of a high dielectric constant solvent and a low viscosity solvent can be used.

  The storage element produced by the method of the above embodiment had a structure in which the electrode body for one layer was housed in the outer package of the laminate film. Of course, it may be a structure in which the electrode body for a plurality of layers is housed in the outer package body of the laminate film. Moreover, the electrical storage element produced by the method which concerns on the Example of this invention is not restricted to what was provided with the exterior body of a laminate film. For example, a button-type (coin-type) storage element, or a well-known spiral-type storage element in which an electrode body is wound in a cylindrical or rectangular cylindrical battery can may be used.

  The procedure for introducing the additive into the outer package of the storage element is not limited to the procedure of adding it to the electrolytic solution as in the above embodiment and storing the electrolytic solution to which the additive is added in the outer package. For example, an electrolytic solution to which no additive is added may be stored in an outer package before sealing, and the additive may be introduced into the outer package by dropping the additive into the outer package. Also, even if a solution additive is added to the positive electrode, the negative electrode, or both in advance, and the electrode body having the additive added to the positive electrode and the negative electrode is enclosed in the outer package together with the electrolytic solution. Good. In order to add the additive to the positive electrode or the negative electrode beforehand, for example, one or both of the positive electrode and the negative electrode, or the electrode assembly may be immersed in a solution-like additive, or the solution-like additive may be added to the positive electrode or the negative electrode It may be dropped on both sides.

1 Laminated storage element, 10 electrode body, 11 exterior body,
11a, 11b laminated film, 20 positive electrodes, 21 positive electrode current collectors,
22 cathode material, 23 cathode terminal plate, 30 anode, 31 anode current collector,
32 negative electrode material, 33 negative electrode terminal plate, 40 separator, s 4 additive preparation process,
s5 Electrolyte adjustment process, s9 pre-doping process

Claims (4)

A positive electrode on which a positive electrode material capable of reversibly supporting lithium ions or anions is coated on a current collector, and a negative electrode on which a negative electrode material capable of absorbing and desorbing lithium ions is coated on a current collector It is a manufacturing method of the electrical storage element which comprises an electrode body and an electrolytic solution which are disposed opposite to each other with the positive electrode and the negative electrode interposed therebetween via a separator,
A pre-doping step in which lithium ions are stored in advance in the negative electrode by charging the storage element after the electrode body and the electrolytic solution are enclosed in the outer package;
An additive preparation step of preparing an additive including a lithium ion supply source stored in advance in the negative electrode;
An additive introducing step of introducing the additive into the outer package;
Including
In the additive preparation step, lithium halide is used as a lithium ion supply source, and the lithium halide is dissolved in a solvent to prepare the additive.
A manufacturing method of a storage element characterized in that.   The method of manufacturing a storage element according to claim 1, wherein in the additive preparation step, N, N-dimethylformamide is used as the solvent.   The method of manufacturing an electricity storage device according to claim 1, wherein dimethylsulfoxide is used as the solvent in the additive preparation step.   The method according to any one of claims 1 to 3, wherein in the additive introducing step, the additive is added to the electrolytic solution, and the electrolytic solution is accommodated in the outer package. Storage element manufacturing method.

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