JP5293112B2 - Method for producing active material and method for producing electrode body - Google Patents

Description

  The present invention relates to a method for producing an active material, a method for producing an electrode body, and a lithium ion secondary battery. In particular, the present invention relates to a method for producing an active material capable of producing an active material that can also be used as a positive electrode active material for a lithium ion secondary battery, a positive electrode active material produced by the method for producing the active material, and a solid electrolyte. The present invention relates to an electrode body manufacturing method for manufacturing an electrode body, and a lithium ion secondary battery including the electrode body manufactured by the electrode body manufacturing method.

  A lithium ion secondary battery has the characteristics that it has a higher energy density than other secondary batteries and can operate at a high voltage. For this reason, it is used as a secondary battery that can be easily reduced in size and weight in information equipment such as a mobile phone, and in recent years, there is an increasing demand for large-sized power such as for hybrid vehicles.

  The lithium ion secondary battery includes a positive electrode layer and a negative electrode layer, and an electrolyte disposed between the positive electrode layer and the negative electrode layer, and the electrolyte is composed of a non-aqueous liquid or solid. When a non-aqueous liquid (hereinafter referred to as “electrolytic solution”) is used as the electrolyte, the electrolytic solution penetrates into the positive electrode layer. Therefore, the interface between the positive electrode active material constituting the positive electrode layer and the electrolyte is easily formed, and the performance is easily improved. However, since the widely used electrolyte is flammable, it is necessary to mount a system for ensuring safety. On the other hand, since the solid electrolyte is nonflammable, the above system can be simplified. Therefore, a lithium ion secondary battery in a form provided with a solid electrolyte that is nonflammable (hereinafter sometimes referred to as a “solid electrolyte layer”) has been proposed.

  In a lithium ion secondary battery in which a solid electrolyte layer is disposed between a positive electrode layer and a negative electrode layer (hereinafter sometimes referred to as a “compact all-solid battery”), the positive electrode active material and the electrolyte are solid. The electrolyte hardly penetrates into the positive electrode active material, and the interface between the positive electrode active material and the electrolyte is likely to be reduced. Therefore, in the powder all-solid battery, the area of the interface is increased by using, as the positive electrode layer, a positive electrode mixture layer containing a mixed powder obtained by mixing a positive electrode active material powder and a solid electrolyte powder.

  Further, in a powder all-solid battery, resistance when lithium ions move through the interface between the positive electrode active material and the solid electrolyte (hereinafter sometimes referred to as “interface resistance”) tends to increase. This is said to be because a high resistance site is formed on the surface of the positive electrode active material by the reaction between the positive electrode active material and the solid electrolyte (Non-patent Document 1). Since there is a correlation between the interfacial resistance and the performance of the dust all-solid battery, a technique aimed at improving the performance of the dust all-solid battery by reducing the interface resistance has been disclosed so far. It is coming. For example, Non-Patent Document 1 discloses a technique for reducing the interfacial resistance by using a positive electrode active material in which the surface of lithium cobaltate is covered with lithium niobate.

  In addition, Patent Document 1 discloses a technique related to an electrode material for an all-solid-state secondary battery that has been surface-treated with at least sulfur and / or phosphorus. Patent Document 2 discloses a technique related to a compacted all-solid battery in which lithium chloride is supported on at least a part of the surface of a positive electrode active material made of a lithium-containing transition metal oxide.

JP 2008-27581 A JP 2001-52733 A Electrochemistry Communications, 9 (2007), p. 1486-1490

  According to the technique disclosed in Non-Patent Document 1, it is considered that the interface resistance can be reduced by coating the surface of lithium cobaltate with lithium niobate. However, when heat treatment is performed in an oxygen atmosphere at 400 ° C. disclosed in Non-Patent Document 1, lithium niobate contained in the coating layer formed on the surface of the active material is crystallized. When lithium niobate is crystallized, the interfacial resistance increases. Therefore, in the technique disclosed in Non-Patent Document 1, it may be difficult to sufficiently reduce the interfacial resistance of the coating layer. There was a problem that the effect might be impaired. Such a problem has been difficult to solve even if the technique disclosed in Non-Patent Document 1 and the technique disclosed in Patent Documents 1 and 2 are combined.

  Then, this invention makes it a subject to provide the manufacturing method of an active material, the manufacturing method of an electrode body, and a lithium ion secondary battery which can reduce interface resistance.

In order to solve the above problems, the present invention takes the following means. That is,
According to a first aspect of the present invention, there is provided a coating process in which a solution containing a lithium niobate precursor is applied to the surface of an ion conductive material to produce a heat-treated body, and a heat-treated body produced in the coating process. And a heat treatment step of producing an active material by heat treatment in an ozone atmosphere at a temperature of not less than 300 ° C and not more than 300 ° C.

  In the present invention, the “ion conducting substance” refers to a substance that allows metal ions to enter and exit. Specific examples of metal ions include lithium ions. Moreover, as a specific example of the ion conductive material capable of entering and exiting lithium ions, lithium cobaltate and the like can be given. The “ion conducting substance” in the present invention may be a substance that reacts with lithium niobate in an oxygen atmosphere at 400 ° C., for example. The active material manufactured according to the first aspect of the present invention using an ion conductive material capable of entering and exiting lithium ions can be used as a positive electrode active material of a lithium ion secondary battery. Further, in the present invention, the form of the application step is particularly suitable if the solution containing the lithium niobate precursor can produce a heat-treated body in which at least a part of the surface of the ion conductive material is applied. It is not limited and can be a known form. In the present invention, the ozone concentration in the atmosphere is not particularly limited as long as the “ozone atmosphere” in the heat treatment step is an ozone-containing atmosphere. The ozone concentration of the ozone atmosphere in the present invention can be set to 0.1%, for example.

According to a second aspect of the present invention, there is provided a coating process in which a solution containing a lithium niobate precursor is applied to the surface of an ion conductive material to produce a heat-treated body, and a heat-treated body produced in the coating process. ℃ and heat treatment step to prepare a positive electrode active material was heat-treated at 300 ° C. in less ozone atmosphere above, a cathode active material prepared by the heat treatment step, a mixing step of mixing a solid electrolyte comprising a solid sulfide , characterized in that it have a a method of manufacturing an electrode body.

  In the second aspect of the present invention, the “mixing step” is not particularly limited as long as it is a step capable of uniformly mixing the positive electrode active material and the solid electrolyte containing solid sulfide, and has a known form. be able to. However, from the viewpoint of making it possible to produce an electrode body capable of reducing the interface resistance, the shearing force applied in the mixing step so that peeling of the coating layer formed on the surface of the ion conductive material can be suppressed. It is preferable that the positive electrode active material and the solid electrolyte containing solid sulfide be uniformly mixed while maintaining a state where is a predetermined value or less (for example, 10 [N] or less).

  According to 1st this invention, decomposition | disassembly of the solution apply | coated to the ion conductive substance can be accelerated | stimulated by performing heat processing in ozone atmosphere. Therefore, a coating layer containing lithium niobate can be formed on the surface of the ion conductive material even in an environment of 260 ° C. or higher and 300 ° C. or lower than the conventional temperature. In addition, the heat treatment under such a temperature environment can suppress or prevent the reaction between the ion conductive material and the coating layer and the crystallization of lithium niobate contained in the coating layer. Since the coating layer containing lithium niobate can be formed, the interface resistance of the coating layer can be reduced. Therefore, according to 1st this invention, the manufacturing method of the active material which can manufacture the active material which can reduce interface resistance can be provided.

In the second present invention, to produce the electrode body by using the cathode active material manufactured through the same coating process and heat treatment process and method of manufacturing an active material according to the first aspect of the present invention. Therefore, according to the second aspect of the present invention, it is possible to provide an electrode body manufacturing method capable of manufacturing an electrode body capable of reducing the interface resistance.

  It is known that by using a positive electrode layer (electrode body) containing a positive electrode active material on which a coating layer is formed and a solid electrolyte, the lithium ion conduction resistance (interface resistance) of a powdered all-solid battery can be reduced. Yes. In order to improve the performance of the powder all-solid battery, it is effective to form a coating layer having a low interface resistance. As a result of intensive studies, the present inventors have conducted a heat treatment for forming a coating layer at a conventional temperature (for example, about 400 ° C.), and the reaction between the active material on which the coating layer is formed and the coating layer The present inventors have found that there is a concern about crystallization of substances contained in the coating layer. The knowledge is described in detail as follows.

  The present inventors mixed lithium cobaltate and lithium niobate with a ball mill, and analyzed these with a powder X-ray diffractometer by accelerating the reaction by heat treatment at 120 ° C. for 2 weeks. The reactivity of was evaluated. The results are shown in FIG. In FIG. 7, the vertical axis represents intensity [cps] and the horizontal axis represents diffraction line angle 2θ [°]. In FIG. 7, “●” represents the peak of lithium niobate, “◯” represents the peak of lithium cobaltate, and “x” represents CoO (NbO) produced by the reaction of lithium niobate and lithium cobaltate. Each peak is shown. From FIG. 7, a peak of CoO (NbO) was confirmed. Therefore, it turns out that lithium niobate and lithium cobaltate react at the temperature of 120 degreeC or more.

On the other hand, J.H. Appl. Phys. 49 (9), 1978, p. In 4808 (hereinafter referred to as “Non-Patent Document 2”), crystalline lithium niobate is an insulator having an activation energy of 1.9 [eV], whereas it is amorphous. It is described that lithium niobate has an activation energy of 0.4 [eV] and a lithium ion conductivity of 1 × 10 ⁻⁶ [S / cm]. That is, it can be said that when lithium niobate is crystallized, the lithium ion conduction resistance increases and the lithium ion conductivity decreases. Non-Patent Document 2 describes that the crystallization start temperature of lithium niobate is 360 ° C., and that lithium hydroxide decomposes at 290 ° C. (dehydration reaction: 2LiOH → Li ₂ O + H ₂ O). Has been.

On the other hand, the present inventors put a solution containing a precursor of lithium niobate (hereinafter sometimes referred to as “precursor-containing solution”) in a different atmosphere, and conduct Raman spectroscopic analysis while heating, The presence or absence of changes in peak shape was investigated. The results are shown in FIGS. FIG. 8 is a diagram showing the results of Raman spectroscopic analysis of a precursor-containing solution heated in an air atmosphere, and FIG. 9 is a diagram showing the results of Raman spectroscopic analysis of a precursor-containing solution heated in an oxygen atmosphere. These are figures which show the Raman spectroscopic analysis result of the precursor containing solution heated in ozone atmosphere. 8 to 10, the vertical axis represents scattered light intensity [cps], and the horizontal axis represents the Raman shift in terms of wave number [cm ⁻¹ ]. From FIG. 8, when heated in an air atmosphere, the peak shape did not change up to a heating temperature of 260 ° C., and the peak shape changed at a heating temperature of 300 ° C. Further, from FIG. 9, when heated in an oxygen atmosphere, the peak shape did not change up to the heating temperature of 260 ° C., and the peak shape changed at the heating temperatures of 280 ° C. and 300 ° C. Further, as shown in FIG. 10, when heated in an ozone atmosphere, the peak shape did not change up to the heating temperature of 240 ° C., and the peak shape changed at the heating temperatures of 260 ° C., 280 ° C., and 300 ° C. From these results, it was found that the temperature at which the peak shape starts to change can be lowered by increasing the oxidizing power of the atmosphere.

  As described above, the present inventors applied a heat treatment in which the temperature and atmosphere were controlled to a heat-treated body prepared by applying a precursor-containing solution to the surface of an ion conductive material (for example, lithium cobalt oxide), thereby covering It was found that the interface resistance of the layer can be reduced. The present invention has been made on the basis of such findings, and a method for producing an active material capable of reducing interfacial resistance by forming a coating layer containing homogeneous amorphous lithium niobate The first gist is to provide a method for manufacturing an electrode body. In addition, by providing a positive electrode active material having a coating layer with reduced interface resistance, it is possible to provide a lithium ion secondary battery (compact all-solid battery) capable of improving performance. This is the second gist.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

1. Active Material Manufacturing Method FIG. 1 is a flowchart showing a flow of steps included in the active material manufacturing method of the present invention. FIG. 2 is a diagram showing a form example of the active material 1 produced by the method for producing an active material of the present invention. An active material 1 shown in FIG. 2 is a lithium cobaltate 2 (hereinafter, also referred to as “ion conductive material 2”) that is an ion conductive material, and a homogeneous material formed on the surface of the ion conductive material 2. And a coating layer 3 containing amorphous lithium niobate. Hereafter, the manufacturing method of the active material of this invention is demonstrated, referring FIG.1 and FIG.2.
As shown in FIG. 1, the manufacturing method of the active material of this invention has a coating process (process S11) and a heat treatment process (process S12).

1.1. Application process (process S11)
Step S11 is performed by applying a solution (precursor-containing solution) containing lithium niobate precursors (for example, LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₅ ) to the surface of the ion conductive material 2. This is a step of producing a heat-treated body constituted by coating at least a part of the surface of the ion conductive material 2 with a precursor-containing solution. In step S11, for example, a precursor-containing solution prepared by dissolving equimolar LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₅ in a solvent (eg, ethanol) is transferred to the surface of the ion conductive material 2. By spray coating using a dynamic fluidized coating apparatus, a form to be heat-treated in which at least a part of the surface of the ion conductive material 2 is coated with the precursor-containing solution can be obtained. Process S11 is not limited to the said form, By apply | coating a precursor containing solution to the surface of the ion conductive material 2, at least one part of the surface of the ion conductive material 2 was coat | covered with the precursor containing solution. Other forms are possible as long as the heat-treated body can be manufactured.

1.2. Heat treatment step (step S12)
Step S12 is an active process in which at least a part of the surface of the ion conductive material 2 is coated with the coating layer 3 by heat-treating the heat-treated body prepared in the above-described step S11 in an ozone atmosphere of 260 ° C. or higher and 300 ° C. or lower. This is a process for producing the substance 1. Here, since the crystallization start temperature of lithium niobate is 360 ° C. as described above, the heat treatment is performed at 260 ° C. or more and 300 ° C. or less to prevent crystallization of lithium niobate according to the present invention. can do. Furthermore, by performing the heat treatment in an ozone atmosphere having a high oxidizing power, the peak shape can be changed even when the heat treatment temperature is 260 ° C. or higher and 300 ° C. or lower. Of lithium niobate can be formed. That is, according to step S12 of the present invention, the coating layer 3 containing homogeneous amorphous lithium niobate can be formed on the surface of the ion conductive material 2, so that the active material 1 can be produced. it can. The heat treatment time in step S12 is not particularly limited as long as it is a time during which the active material 1 can be produced. For example, it can be 2 hours.

  Thus, according to the manufacturing method of the active material of this invention which has process S11 and process S12, the homogeneous amorphous niobic acid formed in the surface of ion conduction material 2 and this ion conduction material 2 An active material 1 having a coating layer 3 containing lithium can be produced. As described above, when the amorphous lithium niobate is present in the coating layer 3, compared with the case where only the crystalline lithium niobate is contained in the coating layer 3, the interface resistance of the coating layer 3 ( Lithium ion conduction resistance) can be reduced. Therefore, according to this invention, the manufacturing method of the active material which can manufacture the active material 1 which can reduce interface resistance can be provided.

2. Electrode Body Manufacturing Method FIG. 3 is a flowchart showing a flow of steps included in the electrode body manufacturing method of the present invention. FIG. 4 is a cross-sectional view showing an example of the form of the electrode body 5 manufactured by the electrode body manufacturing method of the present invention. 4, components having the same configuration as in FIG. 2 are denoted by the same reference numerals as those used in FIG. 2, and description thereof is omitted as appropriate. Hereinafter, the manufacturing method of the electrode body of the present invention will be described with reference to FIGS.

As shown in FIG. 3, the manufacturing method of the electrode body of this invention has a coating process (process S21), a heat treatment process (process S22), and a mixing process (process S23). On the other hand, as shown in FIG. 4, the electrode body 5 manufactured by the method for manufacturing an electrode body of the present invention is referred to as an active material 1, 1,... (Hereinafter referred to as “positive electrode active material 1, 1,...”). And solid electrolytes 4, 4,..., And these are uniformly mixed. The positive electrode active materials 1, 1,... Have ion conductive materials 2, 2,... And coating layers 3, 3,. In the electrode body 5, the ion conductive materials 2, 2,... Are lithium cobalt oxide, and the main component of the coating layers 3, 3,. On the other hand, the solid electrolytes 4, 4,... Are made of Li ₇ P ₃ S ₁₁ .

  In the electrode body 5, when the ion conductive materials 2, 2,... Contact with the solid electrolytes 4, 4,..., They react to form a high resistance site on the surface of the ion conductive materials 2, 2,. The When a high resistance portion is formed on the surface of the ion conductive material 2, 2,..., The interface resistance increases, and thus the pressure having the electrode body 5 (hereinafter, also referred to as “positive electrode mixture layer 5”). The performance of the powder all-solid battery is reduced. In order to suppress such a situation, in the positive electrode mixture layer 5, the positive electrode active materials 1, 1,... That are coated with the coating layers 3, 3,. 4,... Are mixed. The coating layers 3, 3, ... are arranged on the surfaces of the ion conductive materials 2, 2, ..., and the coating layers 3, 3, ... are arranged between the ion conductive materials 2, 2, ... and the solid electrolytes 4, 4, .... By interposing, reaction between the ion conductive materials 2, 2,... And the solid electrolytes 4, 4,. Therefore, according to the positive electrode mixture layer 5, the interface resistance can be reduced.

2.1. Application process (process S21)
Step S21 is a step of manufacturing a heat-treated body configured by covering at least part of the surfaces of the ion conductive materials 2, 2,... With the precursor-containing solution. Since step S21 can have the same form as step S11, detailed description thereof is omitted.

2.2. Heat treatment step (step S22)
Step S22 is a step of producing the positive electrode active materials 1, 1,... By heat-treating the object to be heat-treated produced in the step S21 in an ozone atmosphere of 260 ° C. or higher and 300 ° C. or lower. Since step S22 can have the same form as step S21, detailed description thereof is omitted.

2.3. Mixing step (step S23)
Step S23 is a step of uniformly mixing the positive electrode active materials 1, 1,... Produced in Step S22 and the solid electrolytes 4, 4,. When the positive electrode active materials 1, 1,... Having the coating layers 3, 3,... Are mixed with the solid electrolytes 4, 4,. The coating layers 3, 3,... Covering the surfaces of the substances 2, 2,. Therefore, in step S23, while maintaining the state where the shearing force applied to the coating layers 3, 3,... Is not more than a predetermined value (for example, 10 [N] or less), the positive electrode active materials 1, 1,. It is preferable to set it as the process which mixes solid electrolyte 4,4, ... uniformly. The step S23 is not particularly limited as long as it can uniformly mix the positive electrode active materials 1, 1,... And the solid electrolytes 4, 4,..., For example, using a spatula. .. Are mixed with the positive electrode active materials 1, 1... And the solid electrolytes 4, 4..., And are mixed with the positive electrode active materials 1, 1. It is preferable to do.

  Further, in step S23, even if the shearing force applied to the coating layers 3, 3,... Is kept below a predetermined value, the positive electrode active materials 1, 1,. Otherwise, the contact interface between the positive electrode active materials 1, 1,... And the solid electrolytes 4, 4,... Decreases, and the lithium ion conductivity and the electronic conductivity in the positive electrode mixture layer 5 decrease. The performance of layer 5 is reduced. Therefore, in step S23, the positive electrode active materials 1, 1,... And the solid electrolytes 4, 4,. It is determined whether or not these are uniformly mixed, for example, the positive electrode active material particles 1, 1,... Produced in step S22 have a diameter of R1, and the positive electrode active contained in the powder mixed in step S23. When the diameter of the aggregate of the substance particles 1, 1,... Is R2, it can be determined by whether or not R2 ≦ 3 × R1 is satisfied.

  Thus, according to the manufacturing method of the electrode body of this invention which has process S21-process S23, by passing through process S21 and process S22, ion-conductive substance 2, 2, ... and a homogeneous amorphous niobic acid The positive electrode active materials 1, 1,... Having the coating layers 3, 3,. And according to the manufacturing method of the electrode body of the present invention, to the powder in which the positive electrode active materials 1, 1,... And the solid electrolytes 4, 4,. The positive electrode mixture layer 5 can be manufactured through steps such as applying and drying a mixture prepared by adding a binder. Since the positive electrode mixture layer 5 contains the positive electrode active materials 1, 1,... Having the coating layers 3, 3,..., According to the present invention, the electrode body 5 (positive electrode mixture) that can reduce the interface resistance. An electrode body manufacturing method capable of manufacturing the agent layer 5) can be provided.

  In the manufacturing method of the electrode body of the present invention, the manufacturing method of the solid electrolytes 4, 4,... Mixed with the positive electrode active materials 1, 1,. It can be produced by the method described in Japanese Patent No. 228570.

3. Lithium Ion Secondary Battery FIG. 5 is a conceptual diagram showing an example of a cell provided in the lithium ion secondary battery of the present invention. 5, components having the same configuration as in FIG. 4 are denoted by the same reference numerals as those used in FIG. 4, and description thereof is omitted as appropriate. FIG. 5 shows a simplified form of the positive electrode layer. Hereinafter, the lithium ion secondary battery of the present invention will be described with reference to FIGS. 4 and 5.

As shown in FIG. 5, the lithium ion secondary battery 10 (hereinafter referred to as “secondary battery 10”) of the present invention is a positive electrode layer (hereinafter referred to as “positive electrode layer 5”) composed of the positive electrode mixture layer 5. A solid electrolyte layer 6 containing Li ₇ P ₃ S ₁₁ , and a negative electrode layer 7 made of In foil. When the secondary battery 10 is charged, lithium ions are extracted from the ion conductive materials 2, 2,... Constituting the positive electrode active materials 1, 1,. The solid electrolytes 4, 4,... And the solid electrolyte layer 6 reach the negative electrode layer 7. On the other hand, when the secondary battery 10 is discharged, lithium ions released from the negative electrode layer 7 are transmitted through the solid electrolyte layer 6, the solid electrolytes 4, 4,... And the coating layers 3, 3,. It reaches the conductive material 2, 2, .... As described above, when the secondary battery 10 is charged / discharged, lithium ions move through the interface between the positive electrode active materials 1, 1,... And the solid electrolytes 4, 4,. In order to achieve output, it is important to reduce the ion conduction resistance (interface resistance) of the interface. Here, the secondary battery 10 includes a positive electrode layer 5, and the positive electrode layer 5 has a positive electrode active material in a state where the coating layers 3, 3,. 1, 1, ... are contained. By interposing the coating layers 3, 3, ... between the ion conductive materials 2, 2, ... and the solid electrolytes 4, 4, ..., the ion conductive materials 2, 2, ... and the solid electrolytes 4, 4, ... This reaction can be suppressed. Therefore, formation of the high resistance site | part on the surface of ion-conductive substance 2, 2, ... can be suppressed. In addition, the coating layers 3, 3,... Contain homogeneous amorphous lithium niobate. By forming the coating layers 3, 3,... Containing homogeneous amorphous lithium niobate on the surfaces of the ion conductive materials 2, 2,..., It becomes easy to reduce the interface resistance. That is, since the secondary battery 10 includes the positive electrode layer 5 that can easily reduce the interface resistance, according to the present invention, the performance can be improved by reducing the interface resistance. The secondary battery 10 can be provided.

  In the present invention, the electrode body and the positive electrode layer of the lithium ion secondary battery may have, for example, the positive electrode active materials 1, 1,... And the solid electrolytes 4, 4,. In addition, it is possible to adopt a form in which another substance (for example, a conductive agent or the like) is contained. In addition to the above effects, the electron conductivity can be improved by adopting a form in which a conductive agent is contained in the electrode body of the present invention or the positive electrode layer of the lithium ion secondary battery. Examples of the conductive agent that can be used in the present invention include acetylene black, ketjen black, graphite and the like in addition to vapor grown carbon fiber.

In the above description of the present invention, the solid electrolyte 4 and 4 constituted by Li ₇ P ₃ S _11, ... although illustrated in the form contained, the present invention is not limited to this embodiment. The solid electrolyte in the present invention is not particularly limited as long as it includes a solid sulfide and can be used in a positive electrode layer of a powder all-solid battery. Specific examples of the solid electrolyte in the present _invention, in addition to the Li ₇ P _{3 S 11,} may be exemplified _{80Li 2 S-20P 2 S 5} , Li 3 PO 4 -Li 2 S-SiS 2 , and the like.

Further, in the above description of the present invention has been described by way of the secondary battery 10 form a solid electrolyte layer 6 containing Li ₇ P ₃ S ₁₁ are provided, a lithium ion secondary battery of the present invention is limited to the form It is not something. The solid electrolyte layer provided in the lithium ion secondary battery of the present invention only needs to be composed of a substance that can function as the solid electrolyte layer of the compacted all solid battery. Specific examples of the substance that can constitute the solid electrolyte layer in the lithium ion secondary battery of the present invention include Li ₇ P ₃ S ₁₁ , 80Li ₂ S-20P ₂ S ₅ , Li ₃ PO ₄ -Li ₂ S- Examples thereof include SiS ₂ and Li _3.25 Ge _0.25 P _0.75 O ₄ .

Moreover, in the said description regarding this invention, although the secondary battery 10 of the form provided with the negative electrode layer 7 comprised with In foil was illustrated, the lithium ion secondary battery of this invention is not limited to the said form. . The negative electrode layer provided in the lithium ion secondary battery of the present invention only needs to be composed of a substance that can function as the negative electrode layer of the compacted all solid battery. Specific examples of substances that can form the negative electrode layer in the lithium ion secondary battery of the present invention include In addition to In, graphite, Sn, Si, Li ₄ Ti ₅ O ₁₂ , Al, Fe ₂ S, and the like. it can.

  In the present invention, the size of the aggregate of the positive electrode active material contained in the powder produced in the mixing step in the electrode body, the lithium ion secondary battery, and the electrode body manufacturing method is the above relationship (R2 ≦ 3 × R1) is satisfied, and when the diameter of the solid electrolyte particles mixed with the positive electrode active material is R3 and the diameter of the aggregate of the solid electrolyte particles mixed with the positive electrode active material is R4, It is preferable that R4 ≦ 3 × R3. Specifically, it is preferable that R2 <35 [μm] and R4 <35 [μm].

1) Production of lithium ion secondary battery <Example 1>
A precursor-containing solution prepared by dissolving equimolar LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₅ in an ethanol solvent is applied to a surface of lithium cobalt oxide (ion conductive material) by a rolling fluid coating device ( Spray coating was performed using SFP-01 (manufactured by POWREC Co., Ltd.). Thereafter, the coated lithium cobalt oxide (heat-treated body) was heat-treated in a mixed gas stream of 280 ° C., 92% nitrogen, 7.9% oxygen, 0.1% ozone for 2 hours (hereinafter referred to as “Example 1”). A layer (coating layer) containing homogeneous amorphous lithium niobate is formed on the surface of lithium cobaltate (ion conducting material) by producing a positive electrode active material of Example 1. did.
Next, the positive electrode active material of Example 1 weighed so that the positive electrode active material: solid electrolyte = 7: 3 by mass ratio, and the solid electrolyte produced by the method disclosed in JP-A-2005-228570 ( Li ₇ P ₃ S ₁₁ ) was mixed to prepare a powder. The positive electrode layer 1 was produced using the powder thus produced, and a secondary battery 10 (hereinafter referred to as “battery of Example 1”) including the cell shown in FIG. 5 was produced.

<Comparative Example 1>
A manufacturing process similar to that of the battery of Example 1 above, except that the positive electrode active material of Comparative Example 1 was prepared through a heat treatment in which the heat treatment atmosphere when the positive electrode active material of Example 1 was produced was changed to an air atmosphere. -The battery of Comparative Example 1 was made of the material.

<Comparative example 2>
The battery of Comparative Example 1 except that the positive electrode active material of Comparative Example 2 was produced through heat treatment in which the heat treatment conditions for producing the positive electrode active material of Comparative Example 1 were changed to 400 ° C. and 0.5 hour. A battery of Comparative Example 2 was produced using the same production process and materials as in Example 1.

<Comparative Example 3>
The same as the battery of Comparative Example 1 except that the positive electrode active material of Comparative Example 3 was produced through heat treatment in which the heat treatment atmosphere when the positive electrode active material of Comparative Example 2 was produced was changed to an oxygen 100% atmosphere. A battery of Comparative Example 3 was produced according to the production process / material.

2) Measurement of interfacial resistance The battery of Example 1, the battery of Comparative Example 1, the battery of Comparative Example 2, and the battery of Comparative Example 3 were charged to 3.58 V at a constant current of 127 μA, and each battery after charging The impedance was measured by the AC impedance method. In impedance measurement, the interfacial resistance is represented by the size of an arc according to the Cole-Cole plot. Further, the capacitance C can be obtained from the frequency of the apex of each arc using the following equation.
2πfm = 1 / RC
Here, fm is the apex frequency, R is the interface resistance, and C is the capacitance. A conceptual diagram of the Cole-Cole plot is shown in FIG.
In the material system used for the battery of Example 1, the battery of Comparative Example 1, the battery of Comparative Example 2, and the battery of Comparative Example 3, from the diameter of the arc corresponding to about capacitance C = 5 × 10 ⁻⁵ F, The resistance (interface resistance) at the positive electrode active material / solid electrolyte interface was determined. Table 1 shows the measurement results of heat treatment conditions and interface resistance.

  From Table 1, the battery of Example 1 having the positive electrode active material of Example 1 had an interface resistance of 36.3Ω. On the other hand, the battery of Comparative Example 1 having the positive electrode active material of Comparative Example 1 has an interface resistance of 94.1Ω, and the battery of Comparative Example 2 having the positive electrode active material of Comparative Example 2 has an interface resistance of 54.0Ω. The battery of Comparative Example 3 having 3 positive electrode active materials had an interface resistance of 37.1Ω. That is, the battery manufactured through the process of heat treatment in the ozone atmosphere at 280 ° C. (battery of Example 1) is the battery manufactured through the process of heat treatment in the oxygen atmosphere of 400 ° C. (battery of Comparative Example 3). It was confirmed that the interface resistance can be reduced. That is, according to the present invention, it is possible to provide an active material, an electrode body, and a lithium ion secondary battery that have the same or better performance than the conventional one even if the heat treatment temperature is lower than the conventional one, and the interface resistance can be reduced. It was confirmed that.

It is a flowchart which shows the example of the form of the manufacturing method of the active material concerning this invention. It is sectional drawing which shows the example of the form of the active material 1 manufactured with the manufacturing method of the active material concerning this invention. It is a flowchart which shows the example of the form of the manufacturing method of the electrode body concerning this invention. It is sectional drawing which shows the example of the form of the electrode body 5 manufactured with the manufacturing method of the electrode body concerning this invention. 1 is a conceptual diagram showing an example of a cell configuration provided in a secondary battery 10. It is a conceptual diagram of a Cole-Cole plot. It is a figure which shows the result of X-ray diffraction. It is a figure which shows the result of a Raman spectroscopic analysis. It is a figure which shows the result of a Raman spectroscopic analysis. It is a figure which shows the result of a Raman spectroscopic analysis.

Explanation of symbols

1 ... Active material (positive electrode active material)
2 ... lithium cobaltate (ion-conducting material)
3 ... coating layer 4 ... solid electrolyte 5 ... electrode body (positive electrode mixture layer, positive electrode layer)
6 ... Solid electrolyte layer 7 ... Negative electrode layer 10 ... Secondary battery (lithium ion secondary battery)

Claims (2)

An application step of applying a solution containing a precursor of lithium niobate to the surface of the ion conductive material to produce a heat-treated body;
A heat treatment step of producing an active material by heat-treating the heat-treated body produced in the coating step in an ozone atmosphere of 260 ° C. or higher and 300 ° C. or lower;
A method for producing an active material, comprising: An application step of applying a solution containing a precursor of lithium niobate to the surface of the ion conductive material to produce a heat-treated body;
A heat treatment step of producing a positive electrode active material by heat-treating the heat-treated body produced in the coating step in an ozone atmosphere of 260 ° C. or higher and 300 ° C. or lower;
A mixing step of mixing the positive electrode active material produced in the heat treatment step and a solid electrolyte containing solid sulfide ;
A method for producing an electrode body, comprising:

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