JP2010097707A - Pre-doping method of lithium ion, electrode, and storage capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for pre-doping lithium ions, while preventing the crystal structure collapse of an insertion-based substance. <P>SOLUTION: An electrode configuration A consists of a lithium electrode 10, a positive electrode 20, and a negative electrode 30. In the electrode configuration A, the lithium electrode 10 and the positive electrode 20 are electrically connected through a charge/discharge device 40a. Through charging, a pillar element P, included in an active material 21 of the positive electrode 20, is dedoped to the lithium electrode 10 side. After that, the mode is switched to discharging for pre-doping lithium ion into the active material 21, after dedoping of pillar element P from the lithium electrode 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technology of a power storage unit such as a lithium ion secondary battery, and is particularly effective when applied to a lithium ion pre-doping method for an insertion material used for a positive electrode active material or the like.

  The technology described below has been studied by the present inventors in completing the present invention, and the outline thereof is as follows.

  In order to spread electric vehicles (EV) in earnest, it is essential to extend the cruising range. Lithium ion batteries (LIBs) are taken as one of the most promising candidates for storage power sources for electric vehicles because of their high energy density. In such a lithium ion battery, there is a demand for further improvement in energy density. In addition, when mounted on an electric vehicle, the lithium ion battery must be excellent in safety.

  Such lithium ion batteries have been developed using, for example, vanadium oxide compounds as electrode active materials. A vanadium oxide compound has a high characteristic of incorporating lithium ions between layers of the layered crystal structure. Therefore, it is attracting attention because it can extract high energy.

Further, among vanadium oxide compounds, vanadium pentoxide (V ₂ O ₅ ) has attracted particular attention. By using vanadium pentoxide as an electrode active material, it is possible to increase the size and capacity of the lithium ion battery. In addition, it is considered promising as a storage battery for electric vehicles as a safe battery having a high energy density.

For example, Patent Document 1 proposes to use such vanadium pentoxide as an active material. It is described that vanadium pentoxide, which is an active material, is represented by the chemical formula M _x V ₂ O ₅ A _y · nH ₂ O. M represents a cation, and A represents an anion. In particular, since a strong inorganic acid is used in production, A is described as a nitrate ion, a sulfate ion, or a chlorine ion.
Japanese Patent Publication No. 2004-511407

  The inventor has been researching a vanadium oxide-based material that is easily doped or dedoped with lithium ions. Under such circumstances, the layer length of the crystal structure of the vanadium oxide material was shortened. As a result, it has been found that the ease of doping and dedoping of lithium ions can be improved, and an earlier application was filed.

  This proposal shortens the path length (passage distance) of lithium ions by defining the layer length to a certain length or less. The idea is to ensure smoothness of entering and exiting the layered crystal structure by shortening the bus length. However, it is preferable if there is a means for ensuring smoothness of entry and exit of the lithium ions into the layered crystal structure without changing the layer length.

  In general, it has been pointed out that the crystal structure of an insertion material (host material) doped with lithium ions collapses upon dedoping. Such collapse makes it difficult to dope lithium ions again. Moreover, even if it is doped, it is naturally difficult to dope.

  Therefore, the present inventor made a proposal in the previous application to dope the interlayer securing member into the layered crystal structure. The dope of the interlayer securing member prevents the crystal structure from collapsing. That is, in the layered crystal structure such as vanadium pentoxide, the collapse of the crystal structure due to lithium ion doping and dedoping was avoided. Such proposals have improved cycle stability and the like.

  However, further improvement in cycle stability is required. There is also a demand for further improvement in energy density. In order to improve the energy density, it is required to increase the amount of lithium ion doping and dedoping as one means.

  When the doping amount of lithium ions is large, the crystal structure of the host material is more easily collapsed than when the doping amount of lithium ions is small. Therefore, there is a need for a technique that suppresses the further collapse of the crystal structure of an insertion material such as vanadium oxide and increases the doping amount of lithium ions. Incidentally, in the previous application, the dope amount of the interlayer securing member was limited to 0.5 mol or less per mol of vanadium oxide.

  An object of the present invention is to provide a technique for doping lithium ions while suppressing the collapse of the crystal structure of an insertion material.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows. That is, an element that has an ion radius larger than that of lithium ions and can be electrically dedoped is previously included in the crystal structure of the host material that is an insertion material of lithium ions. The ions of such elements are exchanged for lithium ions to dope lithium ions.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  In other words, in the present invention, the insertion structure material doped with lithium ions contains an element that has an ionic radius larger than that of lithium ions and can be electrically dedoped. Such an element suppresses the collapse of the crystal structure at the time of lithium ion doping or the like. Further, the element exchanges ions with lithium ions to ensure the pre-doping amount of lithium ions. As a result, the capacity retention rate, high rate discharge performance, and the like of the power storage unit using such electrodes are improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention relates to a power storage unit such as a lithium ion secondary battery. In particular, it is a technique applicable to an electrode used in a power storage unit such as a lithium ion secondary battery. This is a technique of doping lithium ions into an active material used for an electrode. That is, the present invention is effective when applied to a so-called pre-doping technique in which an insertion material used for a positive electrode or the like is doped (inserted) with lithium ions in advance. Such a technique can be applied to an insertion material such as vanadium oxide containing vanadium pentoxide or the like. This is a technique that enables pre-doping and dedoping of a high concentration of lithium ions to an insertion material used as such an active material. As a result, for example, the capacity retention rate is improved and the high rate discharge characteristics are improved.

  Examples of insertion materials to which the present invention can be applied include oxides and sulfides of transition metals. Such a substance has a crystal structure capable of pre-doping lithium ions between layers.

  Specific examples include lithium-containing transition metal oxides such as lithium cobalt oxide and lithium manganese oxide, and so-called polyanionic lithium-containing compounds such as lithium iron phosphate and lithium silicate. In addition, lithium can be inserted into a substance that does not contain lithium ions in the original material. Transition metal oxides such as vanadium and manganese are known.

  The insertion material is pre-doped with lithium ions. In the present invention, when lithium ions are pre-doped, an element (pillar element) different from the lithium element is previously contained in the insertion material. Such an element different from lithium ions is required to have an ion radius larger than that of lithium ions. By satisfying such a requirement, a space larger than lithium ions can be secured. In addition, the smoothness of entering and exiting lithium ions can be ensured. This facilitates pre-doping and dedoping of lithium ions. Furthermore, by including a pillar element in advance, the included crystal structure itself is strengthened, and the collapse of the host structure during lithium ion doping and dedoping is suppressed. That is, the host structure is strengthened.

  Such enhancement of the host structure can be explained as follows. When a host material is synthesized using an element having a small ion radius such as lithium ion, the structure is formed in a state in which repulsion of anions such as oxygen in the host structure is inherent because of the small lithium ion size. become. Once the matrix structure with repulsion in the structure is memorized in that state, when lithium ions are repeatedly inserted / extracted with charge / discharge, it becomes apparent and leads to structural collapse. On the other hand, when a host material is synthesized using an element having a large ionic radius, the repulsion is relaxed and the relaxed state is stored in the host structure, so that a strong host structure in which collapse is suppressed against charge / discharge is obtained. It is formed.

  Such an element is considered to play a role of a strut that prevents the collapse of the crystal structure between layers, for example. In other words, it plays a role as a pillar. Such an element is hereinafter referred to as a pillar element.

  As such pillar elements, for example, as shown in FIG. 1, 11, 12, 19 to 34, 37 to 52, 55 to 84, 87 to 109 in the periodic table Up to the element can be considered. Of course, lanthanoid series elements from 57 to 71 and actinoid series elements from 89 to 103 may also be included. In FIG. 1, the usable elements are elements enclosed within a bold frame in the periodic table. Basically, cations are preferred. However, as long as no reaction occurs, an anion having an ionic radius larger than that of lithium ions may be used. Further, in some cases, an atomic group composed of a plurality of atoms may be used.

  In the present invention, the pillar element is included in the insertion material. In order to strengthen the host structure, 0.2 mol or more is included per 1 mol of the insertion material. In order to further strengthen the crystal strength of the insertion material, it is more desirable to include 0.5 mol or more. If the amount is less than 0.2 mol, the host structure may not be strengthened.

  The number of such pillar elements is preferably as much as possible, but is preferably 1.5 mol or less. This is because in an ordinary industrial production method such as a solid phase synthesis method, a liquid phase synthesis method, or a gas phase deposition method, about 1.5 mol is the upper limit. As a method for producing an insertion material, a solid phase synthesis method, a liquid phase synthesis method, or the like can be used. The solid phase synthesis method is desirable because any pillar element can be easily incorporated into the insertion material by thermal reaction.

  Further, such a pillar element is required to be able to be electrically dedoped from an insertion material. In the present invention, a pillar element is included in the insertion material to suppress the collapse of the insertion material. In addition, by de-doping the included pillar element, lithium ions can be pre-doped in the vacancies. Thereby, lithium ions can be pre-doped at a higher concentration. In order to dedope the doped pillar element, a forcing force is required. It is highly desirable to promote dedoping with electrical forcing. That is, undoping is forcibly forced. Thereafter, the host structure is stored and maintained even in the process of dedoping the pillar element. By removing the pillar element, it is possible to develop lithium ion occupation sites. That is, it is possible to dope lithium ions even in the portion where the pillar element is doped.

  In accordance with the type of pillar element contained in the insertion material, charging is performed by applying a predetermined voltage with reference to a value such as a standard electrode potential. De-doping may be performed by applying such a voltage. Such voltage application is usually preferably performed at 3.5V to 4.5V. Further, it is desirable that the dedoping is performed until the current value is completely attenuated. If de-doping is stopped in the middle, pillar elements are detached intermittently during subsequent charging, and the cell performance deteriorates. Of course, a prescribed amount of pillar elements may be left for the purpose of strengthening the crystal structure. In this case, the dedoping is performed by defining the dedoping amount. However, the dedoping may be performed by applying a predetermined capacity of charging current by applying a voltage. Since the structure is maintained even if the pillar element is desorbed, if a sufficiently strong host structure is obtained at the synthesis stage, it is possible to continue the insertion of lithium ions smoothly. Therefore, at the time of dedoping, the total amount of pillar elements contained or an amount close to the total amount may be dedope.

  Therefore, the content of the pillar element is controlled so that the strength of the host structure can be sufficiently secured. For example, the number of moles of pillar elements contained per mole of the insertion material may be controlled.

  The pillar element artificially contained in the insertion material is dedoped and extracted by controlling the applied voltage as described above. Lithium ions are pre-doped into vacancies in the crystal structure of the insertion material formed by such extraction. Lithium ions are supplied from, for example, a lithium electrode.

  In the present invention, dope means occlusion, support, adsorption or insertion, and means a phenomenon in which ion species such as lithium ions enter an electrode active material which is an insertion material such as a positive electrode. Further, undoping means a phenomenon opposite to such doping. It means a phenomenon in which ionic species such as lithium ions appear. Pre-doping means that an ionic species such as lithium ion is pre-doped into an active material of an electrode prior to energization between the positive and negative electrodes. For example, in a power storage unit such as a lithium ion battery using an insertion material as an active material for an electrode, when the positive and negative electrodes are energized and used, lithium ions are doped or dedoped between the positive and negative electrode active materials. repeat. In such a power storage unit, an electrode using an insertion material as an active material is provided in a state where lithium ions are pre-doped at the beginning of assembly. Such doping of lithium ions is particularly called pre-doping.

  The lithium ion pre-doping method according to the present invention can be carried out, for example, with the electrode configuration shown in FIG. In FIG. 2A, only the electrode configuration is schematically shown for easy understanding. The electrode configuration A has a lithium electrode 10, a positive electrode 20, and a negative electrode 30, as shown in FIG. That is, the electrode configuration A is a three-pole configuration. The lithium electrode 10 is made of, for example, lithium metal. The lithium electrode 10 is provided to face the positive electrode 20. For the positive electrode 20, for example, an insertion material such as vanadium pentoxide is used as an active material. The positive electrode 20 is provided to face the negative electrode 30. In the negative electrode 30, for example, a carbon material or the like is used as an active material.

  The insertion material 21a used as the active material 21 of the positive electrode 20 contains the pillar element P in advance. As described above, the inclusion of the pillar element P is performed by synthesis of an insertion material by a solid phase synthesis method, a liquid phase synthesis method, or the like. In the electrode configuration A in this state, the lithium electrode 10 and the positive electrode 20 are electrically connected via an external load 40 as shown in FIG. For example, the charging / discharging device 40a or the like is connected and connected. In this state, charging is performed between the lithium electrode 10 and the positive electrode 20 using the charging / discharging device 40a. By the charge, the pillar element P is electrically dedope from the active material 21 of the positive electrode 20 in an ionic state. The pillar element P that is electrically forced and dedoped moves to the lithium electrode 10.

  As shown in FIGS. 2A and 2B, the pillar element P to be dedoped is a part of the pillar element P contained in the active material 21. The rest remains in the active material 21 as shown in FIG. The remaining pillar element P ensures the ease of pre-doping of lithium ions performed thereafter. Of course, the ease of doping lithium ions that is repeatedly performed when the electrode after pre-doping is used is also ensured. In addition, the ease of dedoping of predoped lithium ions is ensured.

  That is, the pillar structure P left in the active material 21 prevents the crystal structure from collapsing so that lithium ions can easily enter and exit. It is presumed that the pillar element P plays a role of a support in the crystal structure and prevents collapse. As described above, even if the entire amount of the pillar element or an amount close thereto is dedope, there is no particular problem as long as the crystal structure is strong. Further, depending on the purpose, the dedoping amount of the pillar element P may be controlled by the amount of charging current that flows using the charging / discharging device 40a. The amount of de-doping of the pillar element P can be controlled by the charging current capacity or the time for which a predetermined capacity of charging current is passed.

  In this way, after the pillar element P is dedoped from the positive electrode 20, lithium ions are predoped. In pre-doping, the charge / discharge device 40a is switched to the discharge mode while the lithium electrode 10 and the positive electrode 20 are connected. As shown in FIG. 2C, lithium ions move from the lithium electrode 10 to the positive electrode 20. Lithium ions are pre-doped in the crystal structure of the active material 21 of the positive electrode 20. In other words, lithium ions are pre-doped in the vacancies in place of the dedoped pillar elements P. Here, the pillar element P is mainly incorporated into the coating of the solid electrolyte interface phase (abbreviated as SEI) formed on the surface of the lithium electrode by dedoping as shown in FIG. Therefore, the pillar element P is hardly taken into the active material 21 in the positive electrode 20 again by the discharge operation shown in FIG. In this way, pre-doping of lithium ions into the positive electrode 20 is completed. That is, the lithium ion pre-doping can be completed in the insertion material 21 a which is the active material 21 of the positive electrode 20. The method is not limited to the above method. Of course, pre-doping of lithium ions into the positive electrode 20 may be performed by electrically short-circuiting the positive electrode and the lithium electrode.

  In the above description, between the positive electrode 20 using the active material containing a pillar element and the lithium electrode 10, the pillar element P is dedoped by performing a charging operation, and after the dedoping, the discharging operation is performed to perform the dedoping pillar. Instead of the element P, lithium ions were pre-doped. However, pre-doping of lithium ions can be performed by other methods.

  FIG. 3 shows a lithium ion pre-doping method different from the method described in FIG. The electrode configuration schematically shown in FIG. 3A is the same as the electrode configuration A shown in FIG. That is, the electrode configuration A is composed of the lithium electrode 10, the positive electrode 20, and the negative electrode 30, and is configured to have three electrodes as shown in FIG. The active material 21 of the positive electrode 20 is doped with the pillar element P as in FIG.

  The pillar element P is dedoped between the positive electrode 20 and the negative electrode 30 as shown in FIG. That is, the positive electrode 20 and the negative electrode 30 are electrically connected via the external load 40. For example, the charging / discharging device 40a or the like is connected and connected. In this state, charging is performed between the positive electrode 20 and the negative electrode 30 using the charge / discharge device 40a. By the charging, the pillar element P is electrically dedoped from the active material 21 of the positive electrode 20 in an ionic state. The electrically forced and dedoped pillar element P moves to the negative electrode 30. In the case shown in FIG. 3B, the pillar element P to be dedoped is a part of the pillar element P held in the active material 21, as in FIG. The rest remains in the active material 21 as shown in FIG.

  The remaining pillar element P ensures the ease of doping including the subsequent pre-doping of lithium ions. In addition, the ease of dedoping of predoped lithium ions is ensured. The pillar element P left in the active material 21 prevents the crystal structure from collapsing so that lithium ions can easily enter and exit. Also in such a case, it is presumed that the pillar element P plays a role of a support in the crystal structure and prevents collapse. As described above, even if the entire amount of the pillar element or an amount close thereto is dedoped, there is no particular problem as long as the crystal structure is strong. Further, depending on the purpose, the dedoping amount of the pillar element P may be controlled by the amount of charging current that flows using the charging / discharging device 40a as in the previous example. The amount of de-doping of the pillar element P can be controlled by the charging current capacity or the time for which a predetermined capacity of charging current is passed.

  In this way, after the pillar element P is dedoped from the positive electrode 20 to the negative electrode 30, lithium ions are pre-doped. At the time of pre-doping, the lithium electrode 10 and the positive electrode 20 are electrically connected via the external load 40. For example, the charging / discharging device 40a or the like is connected and connected. In this state, discharge is performed between the lithium electrode 10 and the positive electrode 20 using the charge / discharge device 40a. Lithium ions are pre-doped from the lithium electrode 10 to the positive electrode 20 by the discharge. In other words, lithium ions are pre-doped in the vacancies in place of the dedoped pillar elements P. The pre-doping method is not limited to the above discharge, and an electrical short circuit or the like can be selected.

  Here, the pillar element P is taken into the solid electrolyte interface phase (SEI) film formed on the surface of the negative electrode 30 by dedoping as shown in FIG. Therefore, for example, only lithium ion doping and dedoping are selectively performed when a power storage unit such as a lithium ion secondary battery is used. The pillar element P hardly participates in the doping and dedoping. In this way, pre-doping of lithium ions into the positive electrode 20 is completed. That is, the lithium ion pre-doping can be completed in the insertion material 21 a which is the active material 21 of the positive electrode 20.

  In the lithium ion pre-doping method described above, the electrode configuration A has a tripolar configuration. However, a two-pole electrode configuration may be used. Such a case has been schematically illustrated in FIG. That is, in the configuration illustrated in FIG. 4A, the electrode configuration B includes the negative electrode 30 that is electrically short-circuited with the lithium electrode 10 and the positive electrode 20. In such an electrode configuration B, the lithium electrode 10 and the negative electrode 30 are electrically connected in advance and short-circuited, so that it can be considered substantially one electrode. In that sense, it can be said to be a two-pole configuration.

  In this electrode configuration B, as shown in FIG. 4A, the negative electrode 30 is provided so as to face the lithium electrode 10. The lithium electrode 10 and the negative electrode 30 are electrically short-circuited in advance by connection or the like. On the other hand, the positive electrode 20 is disposed to face the negative electrode 30 that is electrically connected to the lithium electrode 10. As shown in FIGS. 2 and 3, the active material 21 that is the insertion material 21a of the positive electrode 20 contains the pillar element P in its crystal structure. In this electrode configuration B, as shown in FIG. 4 (a), although not shown in the figure, when an electrolyte is injected, the electrode is electrically connected in advance. The dope is happening.

  The electrode configuration B in this state is then electrically connected to the positive electrode 20 via the electrically connected lithium electrode 10 and negative electrode 30 and the external load 40 as shown in FIG. For example, the connection is made via the charging / discharging device 40a or the like. In this state, charging is performed between the electrically connected lithium electrode 10, negative electrode 30, and positive electrode 20. By such charging, the pillar element P is electrically dedoped from the active material 21 of the positive electrode 20 in an ionic state. The pillar element P that is electrically forced and dedoped moves to the lithium electrode 10 and the negative electrode 30 side. As shown in FIG. 4B, the pillar element P moved to the lithium electrode 10 and the negative electrode 30 in accordance with the potentials of the lithium electrode 10 and the negative electrode 30 as the counter electrode of the positive electrode 20 is a pillar doped in the positive electrode 20. Part of the element P. The rest remains in the active material 21 as shown in FIG.

  The remaining pillar element P ensures the ease of doping including the subsequent pre-doping of lithium ions. In addition, the ease of dedoping of predoped lithium ions is ensured. The pillar element P left in the active material 21 prevents the crystal structure from collapsing so that lithium ions can easily enter and exit. Also in such a case, it is presumed that the pillar element P plays a role of a support in the crystal structure and prevents collapse. As described above, even if the entire amount of the pillar element or an amount close thereto is dedope, there is no particular problem as long as the crystal structure is strong. Further, depending on the purpose, the dedoping amount of the pillar element P may be controlled by the amount of charging current that flows using the charging / discharging device 40a as in the above two examples. The amount of de-doping of the pillar element P can be controlled by the charging current capacity or the time for which a predetermined capacity of charging current is passed.

  In this way, after the pillar element P is dedoped from the positive electrode 20, lithium ions are predoped. At the time of pre-doping, the charge / discharge device 40a is switched to the discharge mode while maintaining the connection state of FIG. By this operation, as shown in FIG. 4C, lithium ions are pre-doped from the lithium electrode 10 to the positive electrode 20. In other words, lithium ions are pre-doped in the vacancies in place of the dedoped pillar elements P. The pillar element P is taken into the solid electrolyte interface phase (SEI) film formed on the surfaces of the lithium electrode 10 and the negative electrode 30 during the dedoping shown in FIG. Therefore, for example, there is no competition with lithium ion doping and dedoping that are repeated when a power storage unit such as a lithium ion secondary battery is used. Only lithium ions are selectively doped and undoped. The pillar element P hardly participates in the doping and dedoping. In this way, the lithium ion pre-doping is completed in the insertion material 21 a which is the active material 21 of the positive electrode 20. Also in the above, an electrical short circuit can be selected for the pre-doping method.

  Next, a power storage unit having the electrode configurations A and B will be described. The power storage unit 100 having the electrode configuration A has, for example, a configuration schematically shown in FIG. That is, the power storage unit 100 is provided with the lithium electrode 10, the positive electrode 20, and the negative electrode 30 via the separator 50. The lithium electrode 10, the positive electrode 20, and the negative electrode 30 provided via the separator 50 are immersed in the electrolytic solution. In the lithium electrode 10, for example, metallic lithium 11 a is provided on the current collector 12 as a lithium supply source 11 with a predetermined layer thickness. In the positive electrode 20, a positive electrode active material 21, which is an insertion material 21 a, is provided on a current collector 22 with a predetermined layer thickness. Also in the negative electrode 30, a negative electrode active material 31 is provided on the current collector 32 in a predetermined layer thickness.

  In the positive electrode 20, a positive electrode terminal 23 is provided by being drawn from the current collector 22. In the negative electrode 30, a negative electrode terminal 33 is provided by being drawn from the current collector 32. When the power storage unit 100 is used, the positive terminal 23 and the negative terminal 33 are used. Thus, the electrical storage body 100 as a single unit having a pair of the positive electrode 20 and the negative electrode 30 is configured. Such a power storage unit 100 is put into a package which is an exterior container such as a laminate film, for example, to be a product.

  In the power storage unit 100 configured as described above, pre-doping with lithium ions is performed before making the product. That is, pre-doping is performed in the assembly process of the power storage unit 100. In the pre-doping, as shown in FIG. 5B, first, the current collector 12 of the lithium electrode 10 and the positive electrode terminal 23 drawn from the current collector 22 of the positive electrode 20 are connected. As shown by a broken line, for example, the connection is established by connection a. At the time of such connection, as shown in FIG. 5B, a charge / discharge device 40a is interposed.

  The charging / discharging device 40a as the external load 40 is set to the charging mode. Charging is performed between the lithium electrode 10 and the positive electrode 20 in the charging mode. With this charging, as shown in FIG. 2B, a part of the pillar element P is dedoped from the active material 21 of the positive electrode 20 to the lithium electrode 10. After the de-doping of the pillar element P, the charge / discharge device 40a is switched to the discharge mode and discharge is performed between the lithium electrode 10 and the positive electrode 20 as shown in FIG. By this discharge, lithium ions are pre-doped into the positive electrode 20. This operation can be replaced with an electrical short circuit. In that case, the charging / discharging device 40a may be removed and the lithium electrode 10 and the positive electrode 20 may be short-circuited. When the pre-doping is completed, the connection a between the lithium electrode 10 and the positive electrode 20 indicated by the broken line is removed together with the charge / discharge device 40a. As shown in FIG. 5A, the power storage unit 100 is brought into the original state in which the positive electrode terminal 23 protrudes from the current collector 22.

  Such lithium ion pre-doping is performed in a state where an electrolytic solution is put. Therefore, in the assembly process of the power storage unit 100, for example, the configuration of the single unit shown in FIG. In the inserted state, the pillar element is first dedoped. Subsequently, lithium ion pre-doping may be performed. Then, after the end of pre-doping, the connection a may be removed as described above to close the package and make a product.

  In FIG. 5A, the current collector 12 of the lithium electrode 10 is not electrically connected anywhere. This is because the power storage unit 100 shown in FIG. 5A shows a state before pre-doping with lithium ions or a state after pre-doping with lithium ions.

  The power storage unit 100 having such a configuration can be a power storage unit 110 of a stacked unit, for example, as shown in FIG. In the case of such a stacked unit, a plurality of positive electrodes 20 and negative electrodes 30 are alternately stacked via separators 50. As shown in FIG. 6, a lithium electrode 10 is provided outside the stacked positive electrode 20 and negative electrode 30. The lithium electrode 10 is provided to face the positive electrode 20. A separator 50 is interposed between the lithium electrode 10 and the positive electrode 20. Each of the plurality of positive electrodes 20 has a current collector 22 electrically connected by a connection b. From this connection b, a positive terminal 23 is provided. The plurality of negative electrodes 30 are also electrically connected by connection c. A negative terminal 33 is provided from the connection c. The lithium electrode 10, the positive electrode 20, and the negative electrode 30 may be configured in the same manner as described in FIG. In the power storage unit 110, the current collector 12 of the lithium electrode 10 is not electrically connected anywhere before and after pre-doping with lithium ions, as shown in FIG.

  When pre-doping with lithium ions, the power storage unit 110 electrically connects the lithium electrode 10 and the positive electrode 20 as shown in FIG. That is, the positive electrode terminal 23 of the positive electrode 20 and the lithium electrode 10 provided on both sides of the multilayer unit are electrically connected by the connection a shown by a broken line. In electrical connection, as shown in FIG. 7, a charge / discharge device 40 a is interposed between the positive electrode terminal 23 and the battery. In this state, the charge / discharge device 40a, which is the external load 40, is set to the charge mode, and the pillar element P is partially dedoped from the active material 21. Thereafter, lithium ions are pre-doped from the lithium electrode 10 into the active material 21 of the positive electrode 20 after completion of the dedoping. This operation can be replaced with a short circuit as described above. After completion of the pre-doping, the connection a is removed from the power storage unit 110 together with the charge / discharge device 40a. The pre-doping procedure of the power storage unit 110 is the same as that for the power storage unit 100 of the single unit described above.

  In the power storage unit 100 illustrated in FIG. 5A, the current collectors 12, 22, and 32 are non-hole current collectors that are not provided with holes. In the configuration of the power storage unit 110 illustrated in FIG. 6, perforated current collectors are used for the current collectors 12, 22, and 32. Since it is a laminated type, consideration was given so that pre-doping could be performed more quickly. However, even in the single unit power storage unit 100, a perforated current collector may be used for at least one of the current collectors 12, 22, and 32. In addition, although the time until completion of pre-doping becomes longer, it is needless to say that a current collector without holes may be used for at least one of the current collectors 12, 22, and 32 of the power storage unit 110.

  Next, a power storage unit 200 that employs the lithium ion pre-doping method described with reference to FIG. 3 will be described. The power storage unit 200 has the same electrode configuration A as shown in FIG. That is, the power storage unit 200 has the same configuration as shown in FIG. The power storage unit 200 is provided with a lithium electrode 10, a positive electrode 20, and a negative electrode 30 with a separator 50 interposed therebetween. The lithium electrode 10, the positive electrode 20, and the negative electrode 30 provided via the separator 50 are immersed in the electrolytic solution. In the lithium electrode 10, for example, metallic lithium 11 a is provided on the current collector 12 as a lithium supply source 11 with a predetermined layer thickness. In the positive electrode 20, a positive electrode active material 21, which is an insertion material 21 a, is provided on a current collector 22 with a predetermined layer thickness. Also in the negative electrode 30, a negative electrode active material 31 is provided on the current collector 32 with a predetermined layer thickness.

  In the positive electrode 20, a positive electrode terminal 23 is drawn from the current collector 22. In the negative electrode 30, the negative electrode terminal 33 is drawn from the current collector 32. When the power storage unit 200 is used, the positive electrode terminal 23 and the negative electrode terminal 33 may be used. In this way, the power storage unit 200 is configured as a single unit having a pair of the positive electrode 20 and the negative electrode 30. Such a power storage unit 200 is made into a product, for example, in a package which is an exterior container such as a laminate film.

  In the power storage unit 200 having such a configuration, pre-doping with lithium ions is performed in the same manner as the power storage unit 100 before making a product. In the pre-doping, as shown in FIG. 8A, first, the current collector 32 of the negative electrode 30 and the current collector 22 of the positive electrode 20 are electrically connected. The positive terminal 23 and the negative terminal 33 may be connected. For example, as shown by a broken line, they are connected by a connection d. At the time of such connection, as shown in FIG. 8A, a charge / discharge device 40a is interposed. The charging / discharging device 40a as the external load 40 is set to the charging mode. Charging is performed between the positive electrode 20 and the negative electrode 30 in the charging mode. With this charging, as shown in FIG. 3B, a part of the pillar element P is dedoped from the active material 21 of the positive electrode 20 to the negative electrode 30. When the dedoping is completed, the connection d is removed together with the external load 40, and the electrical connection between the positive electrode 20 and the negative electrode 30 is released.

  After the connection d is removed, the lithium electrode 10 and the positive electrode 20 are electrically connected by the connection a as shown in FIG. For such connection, a charging / discharging device 40a as an external load 40 is interposed. The charging / discharging device 40 a is set to a discharge mode, and discharging is performed between the lithium electrode 10 and the positive electrode 20. As described with reference to FIG. 3C, lithium ions are pre-doped from the lithium electrode 10 into the active material 21 of the positive electrode 20 by the discharge. Of course, this operation can be replaced with an electrical short as described above. The pillar element de-doping and the lithium ion pre-doping are performed in a state where an electrolytic solution is put. Therefore, in the assembly process of the power storage unit 200, for example, the configuration of the single unit shown in FIG. In this state, the dedoping described in FIG. 8A and the pre-doping described in FIG. 8B are sequentially performed. After pre-doping is completed, the connection a may be removed and the package may be closed to obtain a product.

  Such a power storage unit 200 can also be configured as a stacked unit. The power storage unit 210 configured in the stacked unit is the same as the configuration of the power storage unit 110 illustrated in FIG. 6. That is, a plurality of positive electrodes 20 and negative electrodes 30 are alternately stacked with separators 50 interposed therebetween. As shown in FIG. 6, a lithium electrode 10 is provided outside the stacked positive electrode 20 and negative electrode 30. The lithium electrode 10 is provided opposite to the positive electrode 20 with a separator 50 interposed therebetween. The lithium electrode 10, the positive electrode 20, and the negative electrode 30 are configured in the same manner as the power storage unit 110 described with reference to FIG. Since it overlaps, the description is abbreviate | omitted.

  In this power storage unit 210, lithium ions are pre-doped. In such lithium ion pre-doping, first, the positive electrode terminal 23 and the negative electrode terminal 33 are electrically connected as shown in FIG. That is, the plurality of positive electrodes 20 are connected by the connection b, and the plurality of negative electrodes 30 are also connected by the connection c. The positive terminal 23 drawn from the connection b and the negative terminal 33 drawn from the connection c are electrically connected by the connection d. In the connection by the connection d, a charging / discharging device 40a as an external load 40 is interposed. In this state, the charging / discharging device 40a is set to the charging mode, and charging is performed between the positive electrode 20 and the negative electrode 30. By this charging, a part of the pillar element P in the active material 21 of the positive electrode 20 is dedope. The dedoped pillar element P moves to the negative electrode 30 side. When such dedoping is completed, charging is terminated. The connection d is removed together with the charge / discharge device 40a, and the electrical connection between the positive electrode 20 and the negative electrode 30 is released.

  After the charge is released, lithium ion pre-doping is performed. In the pre-doping of lithium ions, the connection state shown in FIG. 9 is changed as shown in FIG. That is, the lithium electrode 10 and the positive electrode 20 are electrically connected by the connection a as shown in FIG. That is, the plurality of positive electrodes 20 connected by the connection b and the lithium electrodes 10 arranged on both sides of the stacked unit are connected to the positive terminal 23 by the connection a. When connecting with the connection a, the charging / discharging device 40 a is interposed between the positive electrode terminal 23 and the current collector 12 of the lithium electrode 10. The charging / discharging device 40a is set to a discharging mode, and discharging is performed between the lithium electrode 10 and the positive electrode 20. By this discharge, lithium ions are doped from the lithium electrode 10 into the active material 21 of the positive electrode 21. Of course, this operation can be replaced with an electrical short as described above. When the doping of lithium ions is completed, the connection a and the charge / discharge device 40a are both disconnected, and the electrical connection between the lithium electrode 10 and the positive electrode 20 is released.

  Next, a power storage unit 300 that employs the lithium ion pre-doping method shown in FIG. 4 will be described. Such a power storage unit 300 has an electrode configuration B shown in FIG. As shown in FIG. 11A, the power storage unit 300 is provided with a lithium electrode 10, a positive electrode 20, and a negative electrode 30. From the beginning, the lithium electrode 10 and the negative electrode 30 are connected so as to be short-circuited by a connection e indicated by a one-dot chain line. The lithium electrode 10, the positive electrode 20, and the negative electrode 30 of the electrode configuration B are provided via a separator 50 as shown in FIG. In the lithium electrode 10 provided via the separator 50, for example, a metal lithium 11 a as a lithium supply source 11 is provided on the current collector 12 with a predetermined layer thickness. In the positive electrode 20, a positive electrode active material 21, which is an insertion material 21 a, is provided on a current collector 22 with a predetermined layer thickness. Also in the negative electrode 30, a negative electrode active material 31 is provided on the current collector 32 with a predetermined layer thickness.

  The lithium electrode 10, the positive electrode 20, and the negative electrode 30 having such a configuration are immersed in an electrolytic solution. On the other hand, since the lithium electrode 10 and the negative electrode 30 are short-circuited as described above, the lithium electrode 10 and the negative electrode 30 with respect to the negative electrode 30 as described above with reference to FIG. To dope lithium ions.

  In the positive electrode 20, a positive electrode terminal 23 is drawn from the current collector 22. In the negative electrode 30, the negative electrode terminal 33 is drawn from the current collector 32. When the power storage unit 300 is used, the positive terminal 23 and the negative terminal 33 are used. In this way, the power storage unit 300 is configured as a single unit having a pair of the positive electrode 20 and the negative electrode 30. Such a power storage unit 300 is made into a product, for example, in a package which is an exterior container such as a laminate film.

  In the power storage unit 300 having such a configuration, lithium ion pre-doping is performed on the positive electrode 20 in the same manner as the power storage units 100 and 200 before making the product. As shown in FIG. 11B, such pre-doping electrically connects the positive electrode terminal 23 and the negative electrode terminal 33 via the charge / discharge device 40a. That is, the positive electrode terminal 23 and the negative electrode terminal 33 in which the lithium electrode 10 is previously short-circuited to the negative electrode 30 by the connection e are connected by the connection f by the charging / discharging device 40 a as the external load 40. In this state, the charging / discharging device 40a is set to the charging mode, and charging is performed between the positive electrode 20, the lithium electrode 10, and the negative electrode 30. With this charging, as shown in FIG. 4B, a part of the pillar element P is dedoped from the active material 21 of the positive electrode 20 into the lithium electrode 10 and the negative electrode 30.

  When de-doping of the pillar element is completed in this manner, lithium ions are pre-doped. That is, the charging / discharging device 40a is switched to the discharge mode while maintaining the states of the connections e and f shown in FIG. By switching to the discharge mode, pre-doping of lithium ions is performed on the positive electrode 20 from the lithium electrode 10 and the negative electrode 30 side. This operation can be replaced with an electrical short as described above. Due to the pre-doping of lithium ions, lithium ions are taken into the active material 21 of the positive electrode 20. After completion of the lithium ion pre-doping, the connection f is removed together with the charge / discharge device 40a.

  Such de-doping of pillar elements and pre-doping of lithium ions are performed in a state where an electrolytic solution is put. For this reason, in the assembly process of the power storage unit 300, for example, the configuration of the single unit shown in FIG. In this state, dedoping and pre-doping with lithium ions described in FIG. Thereafter, after completion of pre-doping, the connection f may be removed and the package may be closed to obtain a product. The connection f indicated by the alternate long and short dash line is not particularly troublesome in use even if it is not removed from the configuration of the power storage unit 300, but may be removed.

  The power storage unit 300 having such a configuration can also be configured as a stacked unit. FIG. 12 shows a power storage unit 310 configured in a stacked unit. In this power storage unit 310, a plurality of positive electrodes 20 and negative electrodes 30 are alternately stacked with separators 50 interposed therebetween. As shown in FIG. 12, a lithium electrode 10 is provided outside the stacked positive electrode 20 and negative electrode 30. The lithium electrode 10 is disposed opposite to the negative electrode 30 with a separator 50 interposed therebetween. Note that the lithium electrode 10, the positive electrode 20, and the negative electrode 30 may be configured in the same manner as the power storage unit 100 or the power storage unit 200 described with reference to FIG. Since it overlaps, the description is abbreviate | omitted.

  In such a power storage unit 310, the lithium electrode 10 and the negative electrode 30 are short-circuited by a connection e indicated by a one-dot chain line from the beginning. Therefore, when the electrode configuration B of the power storage unit 310 is immersed in the electrolytic solution, the lithium electrode 10 is partially doped with lithium ions from the lithium electrode 10. In this state, as shown in FIG. 13, the positive terminal 23 and the negative terminal 33 are electrically connected. In connection, the charging / discharging device 40a as the external load 40 may be interposed, and the connection may be made by the connection f.

  When the charging / discharging device 40a is set to the charging mode in this state, charging is performed between the positive electrode 20, the lithium electrode 10, and the negative electrode 30. The pillar element is partially dedoped from the active material 21 of the positive electrode 20 by charging. When the dedoping is completed, the charge / discharge device 40a is switched to the discharge mode while maintaining the connection state shown in FIG. In the discharge mode, lithium ions are predoped from the lithium electrode 10 and the negative electrode 30 with respect to the positive electrode 20. By such pre-doping, lithium ions are inserted into the crystal structure of the active material 21. When the pre-doping of lithium ions is completed, the connection f and the charge / discharge device 40a are removed, and the electrical connection between the positive electrode 20, the lithium electrode 10, and the negative electrode 30 is released.

  In the power storage units 100, 110, 200, 210, 300, and 310 described above, applicable members partially overlap with the above description, but are as follows. That is, lithium metal can be used as the lithium electrode 10. In addition to metallic lithium, any lithium ion source can be used. For example, use of a lithium alloy can be considered. For example, a Li-Al alloy etc. can be mentioned. Such a lithium supply source may be provided in a predetermined current collector by adjusting the layer thickness, area, etc. according to the pre-doping amount of lithium ions.

  In the present invention, the insertion material 21 a is applied as the active material 21 of the positive electrode 20. As the insertion material, for example, a material having a layered crystal structure having a lithium ion diffusion channel in a two-dimensional direction can be applied. Alternatively, a substance having a crystal structure having a one-dimensional or three-dimensional lithium ion diffusion channel can also be applied.

  Examples of the substance having a layered crystal structure include vanadium compounds. For example, vanadium oxide can be applied. Such vanadium oxide has a chemical formula of VyOx, for example, and x and y can be expressed as real numbers not including 0. In this chemical formula, for example, y is any real number from 1 to 9. x is any real number from 0.2 to 9.0. FIG. 14 shows some of these vanadium oxides found in the literature. When y = 1, vanadium oxides with x = 0.11 to 2.5 are known.

Other than vanadium oxide, for example, LiMO ₂ (M = Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, W), LiMn ₂ O ₄ There are polyanion type materials typified by oxides such as LiFePO ₄ and Li ₂ CoSiO ₄ .

  More practical examples of the pillar element P doped in advance in the crystal structure of the active material 21a of the positive electrode 21 include sodium and cesium. However, as an element applicable to such a pillar element, as described above, an element within the bold frame shown in the periodic table of FIG. 1 is also possible.

  As the active material 31 used for the negative electrode 30, a commonly used active material may be used. For example, in a non-aqueous lithium ion secondary battery, as a material capable of inserting lithium near a lithium potential, tin is used. And alloys of metals such as silicon and lithium, tin oxide, silicon oxide, and lithium intercalation carbon materials. As the lithium intercalation carbon material, for example, graphite, non-graphitic carbon material, polyacene-based material, or the like can be used. Examples of non-graphitic carbon materials include non-graphitizable carbon materials. Examples of the polyacene-based substance include PAS that is an insoluble and infusible substrate having a polyacene-based skeleton. Any of the negative electrode active materials can be reversibly doped with lithium ions.

  In manufacturing the electrodes such as the positive electrode and the negative electrode, generally, a slurry of the active material is once formed. An electrode is manufactured by applying this slurry onto a current collector with a predetermined layer thickness using a die coater or the like, and drying. When forming such an active material slurry, a binder (binder) or a conductive aid is used as necessary.

  As the binder, polyvinylidene fluoride (PVdF) or the like can be used. Such a binder is preferably mixed with conductive particles described below to form a slurry. An electrode can be formed by applying the slurry in a predetermined layer thickness onto a conductive substrate which is a current collector described below.

  As the conductive aid, for example, the following conductive particles can be used. That is, conductive carbon such as ketjen black, metals such as copper, iron, silver, nickel, palladium, gold, platinum, indium and tungsten, conductive metal oxides such as indium oxide and tin oxide, and the like. Such conductive particles may be contained at a ratio of 1 to 30% of the weight of the active material, for example.

  For the current collector, for example, a conductive substrate showing conductivity at least on the surface in contact with the active material of the positive electrode and the negative electrode is used. As such a substrate, a conductive material such as a metal, a conductive metal oxide, or conductive carbon can be used. In particular, copper, gold, aluminum, an alloy thereof, or conductive carbon may be used. Further, when the base is formed of a non-conductive material, it can be used if the base is covered with a conductive material. Moreover, in order to construct a perforated current collector, for example, a porous hole may be provided in an opening ratio of 10% or more and 30% or less. Incidentally, the aperture ratio is a ratio of the total area of the opening surface of the current collector to the area of the current collector metal portion.

  Moreover, the following non-aqueous solvent can be used for electrolyte solution, for example. That is, examples of the non-aqueous solvent include chain carbonates, cyclic carbonates, cyclic esters, nitrile compounds, acid anhydrides, amide compounds, phosphate compounds, amine compounds, and the like. Furthermore, specific examples of the non-aqueous solvent include ethylene carbonate, diethyl carbonate (DEC), propylene carbonate, dimethoxyethane, γ-butyrolactone, N-methylpyrrolidone, N, N′-dimethylacetamide, acetonitrile, or propylene carbonate. It can be applied as a mixture with dimethoxyethane, a mixture of sulfolane and tetrahydrofuran, or the like.

As the electrolyte dissolved in the electrolytic solution, for example, the following can be used. That is, as the _{electrolyte, CF 3 SO 3 Li, C} 4 F 9 SO 8 Li, (CF 3 SO 2) 2 NLi, (CF 3 SO 2) 3 CLi, LiBF 4, LiPF 6, lithium salts LiClO _4, etc. Can be used. The solvent that dissolves the electrolyte is a non-aqueous solvent. Furthermore, the electrolyte layer inserted between the positive electrode and the negative electrode may be a polymer gel (polymer gel electrolyte) containing a non-aqueous solution of the electrolyte.

  In order to confirm the effect of the description of the above embodiment, an experiment was conducted by taking sodium vanadate and lithium vanadate as examples. That is, the case where sodium was included as a pillar element and the lithium vanadate not containing the pillar element were compared and verified.

[Production of Positive Electrode] In this example, an insertion material containing a pillar element was produced by a solid phase method. The insertion materials include MV ₂ O ₅ , MV ₃ O ₈ (M = Na _x Li _y , The composition can be in the range of 1 ≦ x + y ≦ 1.5, x ≧ 0, y ≧ 0. ) Was selected. As the pillar element M, a sodium element was selected. For comparison, lithium vanadate that did not contain pillar elements was selected.

The synthesis of NaV ₂ O ₅ was performed as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ) and 17.1 g of sodium hydroxide (NaOH) were mixed and pulverized and mixed in advance. Next, it was put in an alumina pot and reacted at 400 ° C. for 6 hours under a mixed argon flow of 10% H ₂ and 90% Ar. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, a NaV ₂ O ₅ phase was confirmed. The amount of the pillar element is 1 mol with respect to 1 mol of the insertion material V ₂ O ₅ .

The synthesis of NaV ₃ O ₈ was performed as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ) and 11.4 g of sodium hydroxide (NaOH) were mixed and pulverized and mixed in advance. Next, it was placed in an alumina bowl and reacted at 400 ° C. for 6 hours under air flow. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, a NaV ₃ O ₈ phase was confirmed. The amount of the pillar element is 1 mol with respect to 1 mol of the insertion material V ₃ O ₈ .

The synthesis of Na _1.5 V ₂ O ₅ was performed as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ) and 25.7 g of sodium hydroxide (NaOH) were mixed and pulverized and mixed in advance. Next, it was put in an alumina pot and reacted at 400 ° C. for 6 hours under a mixed argon flow of 10% H ₂ and 90% Ar. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, a NaV ₂ O ₅ phase was confirmed. The amount of the pillar element is 1.5 mol with respect to 1 mol of the insertion material V ₂ O ₅ .

The synthesis of Na _1.5 V ₃ O ₈ was performed as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ) and 17.1 g of sodium hydroxide (NaOH) were mixed and pulverized and mixed in advance. Next, it was placed in an alumina bowl and reacted at 400 ° C. for 6 hours under air flow. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, a NaV ₂ O ₅ phase was confirmed. The amount of the pillar element is 1.5 mol with respect to 1 mol of the insertion material V ₃ O ₈ .

The synthesis of Na _0.2 Li _0.8 V ₂ O ₅ was performed as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ), 3.6 g of LiOH and 17.1 g of NaOH were mixed and pulverized and mixed in advance. Next, it was put in an alumina pot and reacted at 400 ° C. for 6 hours under a mixed argon flow of 10% H ₂ and 90% Ar. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, a Na _0.2 Li _0.8 V ₂ O ₅ phase was confirmed. The amount of the pillar element is 0.2 mol with respect to 1 mol of the insertion material V ₂ O ₅ .

The synthesis of Na _0.2 Li _0.8 V ₃ O ₈ was performed as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ), 2.4 g of LiOH, and 9.1 g of NaOH were mixed and pulverized and mixed in advance. Next, it was placed in an alumina bowl and reacted at 400 ° C. for 6 hours under air flow. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, a Na _0.2 Li _0.8 V ₃ O ₈ phase was confirmed. The amount of the pillar element is 0.2 mol with respect to 1 mol of the insertion material V ₃ O ₈ .

LiV ₂ O ₅ was synthesized as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ) and 17.9 g of lithium hydroxide (LiOH) were mixed and pulverized and mixed in advance. Next, it was put in an alumina pot and reacted at 400 ° C. for 6 hours under a mixed argon flow of 10% H ₂ and 90% Ar. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, the LiV ₂ O ₅ phase was confirmed. The amount of the pillar element is 0 mol with respect to 1 mol of the insertion material V ₂ O ₅ .

LiV ₃ O ₈ was synthesized as follows. 100 g of ammonium metavanadate (NH ₄ VO ₃ ) and 12.0 g of lithium hydroxide (LiOH) were mixed and pulverized and mixed in advance. Next, it was placed in an alumina bowl and reacted at 400 ° C. for 6 hours under air flow. The obtained crude crystals were pulverized again to synthesize the target material. As a result of elemental composition analysis by XRD and ICP, a LiV ₃ O ₈ phase was confirmed. The amount of the pillar element is 0 mol with respect to 1 mol of the insertion material V ₃ O ₈ .

A positive electrode was prepared using the sodium vanadate and lithium vanadate thus obtained as active materials. 90% by weight of NaV ₂ O ₅ as a positive electrode active material was mixed with 5% by weight of conductive carbon black and 5% by weight of polyvinylidene fluoride (PVdF). For example, N-methylpyrrolidone (NMP) was used as the solvent to form a slurry. The slurry was applied and press-molded by a doctor blade method on both sides of a copper current collector having through holes so that the mixture density per side was 2 g / cm ³ . This dried body was cut into a 24 × 36 mm square to form a positive electrode.

Similarly, NaV ₃ O ₈ , Na _1.5 V ₂ O ₅ , Na _1.5 V ₃ O ₈ , Na _0.2 Li _0.8 V ₂ O ₅ , Na _0.2 Li _0.8 V ₃ O ₈ , LiV ₂ O ₅ and LiV ₃ O ₈ were used as active materials, and electrodes were manufactured in the same manner as NaV ₂ O ₅ except that the active materials were different. A slurry was formed from the produced active material using NMP as a solvent. Such a slurry was prepared by drying to form a positive electrode including a comparative example, and press-molded so that the mixture density was 2 g / cm ³ .

[Preparation of Negative Electrode] Graphite was used as the negative electrode active material. The active material graphite and PVdF as a binder were mixed at a ratio of 90:10. A slurry was prepared by diluting with NMP. This slurry was applied to both surfaces of a copper current collector having through-holes, and press-molded so that the composite material density was 1.5 g / cm ³ . The current collector having such a configuration was cut into a 26 × 38 mm square to form a negative electrode.

  [Preparation of Battery (Accumulator)] Using the positive electrode and the negative electrode manufactured as described above, an electric storage body having electrode configurations A and B was prepared in accordance with the description of the embodiment. In the case of the electrode configuration A, two types were formed based on the two different lithium pre-doping methods described in the above embodiment. A polyethylene microporous membrane was used as a separator. And the lithium electrode which affixed metallic lithium on stainless steel porous foil was further arrange | positioned facing the positive electrode through the separator. In this way, a three-electrode laminate unit composed of a positive electrode, a negative electrode, a lithium electrode, and a separator was produced. Using this triode laminate unit, ethylene carbonate and diethyl carbonate were mixed at a ratio of 1: 3 as a solvent, and lithium tetrafluoroborate was dissolved to a concentration of 1 mol / L to prepare an electrolytic solution. In the case of the electrode configuration B, a power storage unit was configured in the same manner as in the case of the electrode configuration A except that the lithium electrode and the negative electrode were short-circuited from the beginning.

  In the case of the power storage unit having such a configuration and having one of the above two types of electrode configurations A, the contained pillar element is contained in a constant current-constant voltage (CC-CV) charging method of 0.1 C, 4.1 V. Dedoped. In addition, in the electrode configuration A in the other case, the incorporated pillar element was dedoped by a constant current-constant voltage (CC-CV) charging method of 0.1 C and 4.1 V. The power storage unit having such a configuration was pre-doped with lithium ions by discharging. Also for the electrode configuration B, the pillar element was dedopeed by a constant current-constant voltage (CC-CV) charging method of 0.1 C and 4.1 V. Further, lithium ion pre-doping was then performed.

  [Measurement of Capacity Retention Ratio] In the two types having the electrode configuration A prepared as described above and the one type of power storage unit having the electrode configuration B, charging was performed at a constant current-constant voltage (CC− of 0.1 C, 4.1 V). CV) The battery was cut for 30 hours by the charging method, and the discharge was a constant current (CC) discharging method of 0.05C at 1.35 V cut, and the capacity retention rate was measured.

  [Measurement of High Rate Discharge Performance] Two types of the above-prepared electrode configuration A and one type of power storage unit having electrode configuration B were charged at a constant current-constant voltage (CC-CV of 0.1 C, 4.1 V). ) The charging method was cut for 30 hours, and the discharge was a constant current (CC) discharge method of 1.35 V cut at 4.0 C, and high rate discharge performance was measured.

  The three types of lithium ion pre-doping methods described in the above embodiment were performed on the battery unit configured as described above. Thus, the capacity maintenance rate and the high rate discharge performance were measured for each of the three types of power storage devices manufactured by the three types of pre-doping methods. The numerical results obtained in this example are shown in tabular form in FIG. In FIG. 15B, the numerical results are visualized for easy understanding.

  As can be seen from FIGS. 15A and 15B, the results of the three pre-doping methods shown in the above-described embodiment based on the electrode configurations A and B were the same.

As is apparent from FIG. 15B, NaV ₂ O ₅ , NaV ₃ O ₈ , Na _1.5 V ₂ O ₅ , Na _1.5 V ₃ O ₈ , Na _0.2 Li _0.8 V ₂ O ₅ In the case of lithium ion pre-doping using Na _0.2 Li _0.8 V ₃ O ₈ as an active material, pre-doping was performed using LiV ₂ O ₅ and LiV ₃ O ₈ shown as comparative examples. Both the capacity retention rate and the high rate discharge performance were better than the case.

In the capacity maintenance rate, the battery using NaV ₂ O ₅ and Na _1.5 V ₂ O _{5 according} to the present invention is about 1.4 times better than LiV ₂ O ₅ as the conventional example. It was confirmed that At the same time, the high rate discharge performance was improved about 1.3 times. Also in the case of Na _0.2 Li _0.8 V ₂ O ₅ , the capacity retention rate is about 1.3 times and the high rate discharge performance is about 1.2 times compared to LiV ₂ O ₅ as the conventional example. It was confirmed to improve.

On the other hand, the NaV ₃ O ₈ and Na _1.5 V ₃ O _{8 according} to the present invention are also about 1.3 times the capacity retention rate and about the high rate discharge performance compared to the LiV ₃ O ₈ of the conventional example. It was confirmed that it was improved by 1.4 times. For even _{Na 0.2 Li 0.8 V 3 O 8} , compared with the _LiV 3 _{O 8} in the conventional example, about 1.2 times the capacity retention ratio, also increased by about 1.3 times in high rate discharge performance It was confirmed that

Further, as clearly shown in the case of Na _0.2 Li _0.8 V ₂ O ₅ and Na _0.2 Li _0.8 V ₃ O ₈ , sodium as a pillar element is _0.1 % per mol of the active material. If 2 mol is contained, the capacity retention rate can be improved at least about 1.3 to 1.2 times. In addition, in such a case, it was confirmed that the high-rate discharge performance can be improved by about 1.2 to 1.3 times.

  From the above results, the structure in which the pillar active element is included in the electrode active material from the beginning as in the present invention, the pillar element is dedoped, and then lithium is pre-doped instead of the pillar element. It was confirmed that it is effective in improving both the capacity retention rate and the high rate discharge performance.

  INDUSTRIAL APPLICABILITY The present invention can be effectively used in the field of power storage units such as lithium ion secondary batteries that perform lithium ion pre-doping.

It is explanatory drawing which showed the range of the usability as a pillar element in this invention with the periodic table. (A), (b), (c) is explanatory drawing which showed typically only an example of the electrode structure concerning this invention. (A), (b), (c) is explanatory drawing which showed typically only an example of the electrode structure concerning this invention. (A), (b), (c) is explanatory drawing which showed typically only an example of the electrode structure concerning this invention. (A), (b) is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. It is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. It is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. (A), (b) is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. It is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. It is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. (A), (b) is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. It is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. It is explanatory drawing which showed typically an example of the electrical storage body concerning this invention which has an electrode structure corresponding to FIG. It is explanatory drawing which showed an example of the vanadium oxide which can be used as an insertion type material in a tabular form. (A) is explanatory drawing which shows a capacity | capacitance maintenance factor and high rate discharge performance in a table | surface form, (b) is explanatory drawing which visualized (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lithium electrode 11 Lithium supply source 11a Metal lithium 12 Current collector 20 Positive electrode 21 Active material 21a Insertion type material 22 Current collector 23 Positive electrode terminal 30 Negative electrode 31 Active material 32 Current collector 33 Negative electrode terminal 40 External load 40a Charge / Discharge device 50 separator 100 power storage unit 110 power storage unit 200 power storage unit 210 power storage unit 300 power storage unit 310 power storage unit A electrode configuration a connection B electrode configuration b connection c connection d connection e connection f connection P pillar element

Claims (11)

A pre-doping method in which lithium ions are pre-doped into an active material used for an electrode before being used between a positive electrode and a negative electrode
An electrically dedopeable element ion-exchanged with the lithium ion having a larger ionic radius than the lithium ion held in the crystal structure of the active material is dedoped from the active material by charging,
A lithium ion pre-doping method, wherein the lithium ion is electrically doped into the crystal structure of the active material which has become vacant by the dedoping. The lithium ion pre-doping method according to claim 1,
The lithium ion pre-doping method is characterized in that the lithium ion doping is performed by discharging. The lithium ion pre-doping method according to claim 1,
The lithium ion pre-doping method is characterized in that the lithium ion doping is performed by a short circuit. The lithium ion pre-doping method according to any one of claims 1 to 3,
The element is contained in an amount of 0.2 mol or more and 1.5 mol or less with respect to 1 mol of the active material before the first undoping. The lithium ion pre-doping method according to claim 4,
The element is contained in an amount of 0.5 mol or more with respect to 1 mol of the active material before the first undoping. In the lithium ion pre-doping method according to any one of claims 1 to 5,
The charging is performed between a positive electrode using an active material containing the element and a lithium electrode,
The lithium ion pre-doping method is performed between the positive electrode after the element is dedope and the lithium electrode. In the lithium ion pre-doping method according to any one of claims 1 to 5,
The charging is performed between a positive electrode using an active material containing the element and a negative electrode,
The lithium ion pre-doping method is characterized in that the lithium ion doping is performed between the positive electrode after the element is dedope and the lithium electrode. In the lithium ion pre-doping method according to any one of claims 1 to 5,
The charging is performed between a negative electrode electrically short-circuited with a lithium electrode and a positive electrode using an active material containing the element,
The lithium ion pre-doping method is performed between a lithium electrode electrically short-circuited with the negative electrode and the positive electrode after the element is dedoped. An electrode having an active material pre-doped with lithium ions in advance for use between a positive electrode and a negative electrode,
The said lithium ion is doped by the pre-doping method of the lithium ion of any one of Claims 1-8, The electrode characterized by the above-mentioned. A power storage unit having the above-mentioned electrode pre-doped with lithium ions in an active material before energization between the positive and negative electrodes,
The electric storage body, wherein the lithium ion is doped into the electrode by the lithium ion pre-doping method according to claim 1. The power storage unit according to claim 10,
The solid electrolyte interfacial phase formed in the negative electrode contains an electrically dedopeable element that has a larger ion radius than lithium ions and is ion-exchanged with the lithium ions in the crystal structure of the active material used in the positive electrode. A power storage unit characterized in that it is contained in an amount less than or equal to the amount of dedope.