JP2009094029A - All-solid lithium secondary battery, and electrode for all-solid lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve cycle life by suppressing increase in battery resistance with time, improve discharge load characteristics by carrying out reduction of inner resistance simultaneously, and improve reliability of the battery in an all solid lithium secondary battery using a polymer solid electrolyte. <P>SOLUTION: In the all solid secondary battery using the polymer solid electrolyte, a solid electrolyte powder is added to an electrode constituting material such as an active material, a conductive assistant, the polymer solid electrolyte, and binder, and the ratio of the polymer solid electrolyte and the inorganic solid electrolyte powder to an electrode mixture is made less than 50% by volume fraction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an all solid-state lithium secondary battery using a polymer electrolyte.

  In recent years, with the rapid spread of high-performance small portable devices such as mobile phones and notebook personal computers, a power source capable of obtaining a high energy density is required. Among secondary batteries, lithium secondary batteries that can obtain high voltage are attracting attention, and are increasingly being applied to small electronic devices, and are beginning to be applied to power storage, power sources for electric vehicles, and the like.

  Such a lithium battery is composed of an electrode made of an inorganic material and a non-aqueous electrolyte. Lithium batteries using non-aqueous electrolytes have excellent rate characteristics and are widely used. However, there are still problems with the risk of leakage, the destruction of equipment due to the generation of flammable gases, the explosion of batteries, and the risk of ignition. Has been. Therefore, research on lithium secondary batteries using a polymer electrolyte capable of avoiding such a risk is underway.

The solid polymer electrolyte as described above is a polymer such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinyl alcohol, or lithium perchlorate, lithium hexafluorophosphate as a supporting electrolyte in a polymer matrix of these copolymers. In addition, a polymer in which lithium tetrafluoroborate, lithium trifluoromethanesulfonate, or the like is dissolved, or a crosslinked product is used.
These solid polymer electrolytes have flexibility and excellent moldability, and can easily form a film and an interface with an active material in an electrode.

  However, solid polymer electrolytes have an ionic conductivity that is about 2 to 3 orders of magnitude lower than that of non-aqueous electrolytes. When used for secondary batteries, the operating temperature must be high and the rate characteristics must be low. Has become an issue. In addition, when used for a secondary battery, since it is repeatedly charged and discharged for a long period of time, chemical stability is also required for the electrode material, but the solid polymer electrolyte is particularly at a high potential of the positive electrode during charging. There are many things that cannot be tolerated, and each time the cycle is repeated, the resistance of the electrolyte increases with time, resulting in a decrease in battery capacity and a problem with short cycle life.

  To address these issues, a technology has been proposed to coat the active material surface with an inorganic material so that the active material and the electrolyte in the electrode are not in direct contact with each other. All-solid-state lithium secondary batteries with high reliability have not been obtained due to problems such as suppression of increase and rate characteristics.

Patent Documents 1 and 2 disclose a technique in which an aqueous solution of (LiPO ₃ ) _n is prepared, mixed with an electrode active material, stirred, and then dried to coat (LiPO ₃ ) _n on the surface of the active material. ing. However, these have the problem that it is difficult to obtain an effect of improving the ionic conductivity of the polymer solid electrolyte portion, and it is difficult to obtain an output. Moreover, it is not preferable because the process for uniformly coating the surface of the active material with an inorganic solid electrolyte must be further added to the existing electrode manufacturing process for lithium ion batteries.
JP 2000-340261 A JP 2000-348711 A

  In view of such circumstances, the object of the present invention is to suppress the increase in battery resistance over time and improve cycle life in an all-solid-state lithium secondary battery using a solid polymer electrolyte, and simultaneously reduce internal resistance. By improving the discharge load characteristics, the reliability of the battery is improved.

In order to solve the above problems, the present inventor added a solid inorganic electrolyte powder to the electrode of an all-solid-state lithium secondary battery using a solid polymer electrolyte, thereby increasing the cycle life and improving the rate characteristics. We have found that an excellent and reliable all solid-state lithium secondary battery can be obtained.
Specifically, the present invention provides the following.

(Configuration 1)
In at least one electrode, the ratio of the polymer solid electrolyte and the inorganic solid electrolyte powder to the electrode mixture containing the active material, the conductive additive, the polymer solid electrolyte, and the inorganic solid electrolyte powder is 50% in volume fraction. An all-solid-state lithium secondary battery having an electrode that is less than
(Configuration 2)
The all-solid-state lithium secondary battery according to Configuration 1, wherein the inorganic solid electrolyte powder is dispersed in the polymer solid electrolyte.
(Configuration 3)
The all-solid-state lithium secondary battery according to Configuration 1 or 2, wherein in at least one electrode, the proportion of the inorganic solid electrolyte powder in the electrode mixture is less than 30% in volume fraction.
(Configuration 4)
4. The all solid lithium secondary battery according to any one of configurations 1 to 3, wherein the inorganic solid electrolyte powder has an average particle size of 30 μm or less.
(Configuration 5)
The inorganic solid electrolyte powder is composed of any one or more of an oxide containing lithium, a compound containing lithium and halogen, and a compound containing lithium and nitrogen. All solid-state lithium secondary battery.
(Configuration 6)
6. The all-solid-state lithium secondary battery according to any one of configurations 1 to 5, wherein the inorganic solid electrolyte powder is a lithium ion conductive oxide.
(Configuration 7)
The inorganic solid electrolyte powder is Li _{1 + x + z} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, 0 ≦ 7. An all-solid-state lithium secondary battery according to any one of Structures 1 to 6, comprising a crystal of z ≦ 0.6 and one or more selected from M = Al and Ga.
(Configuration 8)
All solid type in which the proportion of the polymer solid electrolyte and the inorganic solid electrolyte powder is less than 50% of the electrode mixture containing the active material, the conductive additive, the polymer solid electrolyte and the inorganic solid electrolyte powder. Electrode for lithium secondary battery.
(Configuration 9)
9. The electrode for an all solid-state lithium secondary battery according to Configuration 8, wherein the inorganic solid electrolyte powder is dispersed in the polymer solid electrolyte.
(Configuration 10)
The electrode for the all-solid-state lithium secondary battery according to Configuration 8 or 9, wherein the proportion of the inorganic solid electrolyte powder is less than 30% in terms of volume fraction with respect to the electrode mixture.
(Configuration 11)
11. The electrode for an all solid-state lithium secondary battery according to any one of configurations 8 to 10, wherein the inorganic solid electrolyte powder has an average particle size of 30 μm or less.
(Configuration 12)
The inorganic solid electrolyte powder includes any one or more of an oxide containing lithium, a compound containing lithium and halogen, and a compound containing lithium and nitrogen. Electrode for all solid-state lithium secondary battery.
(Configuration 13)
The electrode for an all-solid-state lithium secondary battery according to any one of Structures 8 to 12, wherein the inorganic solid electrolyte powder is a lithium ion conductive oxide.
(Configuration 14)
The inorganic solid electrolyte powder is Li _{1 + x + z} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, 0 ≦ 14. An electrode for an all-solid-state lithium secondary battery according to any one of Structures 8 to 13, comprising a crystal of z ≦ 0.6 and one or more selected from M = Al and Ga.

According to the present invention, the battery resistance is prevented from increasing over time to improve cycle life, and at the same time, the internal resistance is reduced to improve discharge load characteristics, resulting in long cycle life and excellent rate characteristics. A highly solid all-solid secondary battery can be obtained.
In addition, in the present invention, the manufacturing process of the conventional all-solid-state secondary battery can be simplified, which is practically very effective.

In the all solid-state lithium secondary battery of the present invention, at least one electrode includes an inorganic solid electrolyte powder, and the electrode mixture (the electrode mixture is an active material, a conductive additive, a polymer solid electrolyte, and an inorganic solid electrolyte powder). The solid solid electrolyte powder and the inorganic solid electrolyte powder account for less than 50% in volume fraction. Thus, by including the inorganic solid electrolyte powder in the electrode and making the volume fraction of the polymer solid electrolyte and the inorganic solid electrolyte powder less than 50%, the increase in battery resistance over time is suppressed, and the internal resistance of the battery is reduced. Can be reduced. In order to easily maintain the rate characteristics while obtaining the above effect, the volume fraction of the polymer solid electrolyte and the inorganic solid electrolyte powder is more preferably 48% or less, and most preferably 45% or less.
Further, if the total volume fraction of the polymer solid electrolyte and the inorganic solid electrolyte powder is less than 5%, the lithium ion conductivity in the electrode is lowered and the discharge characteristics are likely to be affected, and the battery resistance over time. The volume fraction is preferably 5% or more, more preferably 15% or more, and more preferably 20% or more% because it is difficult to obtain the effect of suppressing the increase and reducing the internal resistance of the battery. Is most preferred.

  As the active material used for the positive electrode material, a transition metal compound capable of occluding and releasing lithium can be used. For example, at least one selected from manganese, cobalt, nickel, vanadium, niobium, molybdenum, titanium, and iron Transition metal oxides containing can be used.

  As the conductive additive used for the positive electrode material, a carbon-based material such as acetylene black and other known materials can be used.

  Active materials used for the negative electrode material include metal lithium, lithium-aluminum alloys, lithium-indium, silicon, tin alloys such as lithium occluding and releasing alloys, transition metal oxides such as titanium and vanadium, and graphite. It is preferable to use a carbon-based material.

  The polymer solid electrolyte used for the electrode is a polymer such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinyl alcohol, or lithium perchlorate, lithium hexafluorophosphate as a supporting electrolyte in a polymer matrix of these copolymers. In addition, a polymer in which lithium tetrafluoroborate, lithium trifluoromethanesulfonate, or the like is dissolved, or a crosslinked product can be used.

  The electrode containing the inorganic solid electrolyte powder can be prepared by weighing the above materials at a predetermined ratio, mixing them, and applying and drying on the current collector. For mixing, an organic solvent or the like that can dissolve the electrolyte polymer may be used.

The inorganic solid electrolyte powder is preferably dispersed in the polymer solid electrolyte contained in the electrode mixture from the viewpoint of ion conduction in the electrode. FIG. 1 is a conceptual diagram of an electrode of the present invention. As shown in the figure, in the present invention, the inorganic solid electrolyte powder is dispersed in the polymer solid electrolyte. FIG. 2 is a conceptual diagram of a conventional electrode. As shown in this figure, an inorganic solid electrolyte coated in an active material has a polymer solid electrolyte portion compared to a case where it is dispersed in a solid electrolyte. It is difficult to obtain the effect of improving ionic conductivity, and it is difficult to obtain an output. Moreover, it is not preferable because the process for uniformly coating the surface of the active material with an inorganic solid electrolyte must be further added to the existing electrode manufacturing process for lithium ion batteries.
In order to satisfactorily disperse the inorganic solid electrolyte powder in the polymer solid electrolyte, the inorganic solid electrolyte should be added at the same time when the active material, the conductive additive, and the binder are mixed in the electrode preparation process described above. That's fine.

In the all-solid-state lithium secondary battery of the present invention, the ratio of the inorganic solid electrolyte powder to the electrode mixture in the at least one electrode is less than 30% in terms of volume fraction. This is preferable because it is easier to suppress the increase and the internal resistance of the battery can be further reduced. In order to make the above effect easier to obtain, the ratio of the inorganic solid electrolyte powder to the electrode mixture is more preferably 29.9% or less, and most preferably 27% or less in terms of volume fraction. .
In addition, when the proportion of the inorganic solid electrolyte powder to the electrode mixture is less than 2%, it is difficult to obtain the effect of suppressing the increase in battery resistance with time and reducing the internal resistance of the battery. Is preferably 2% or more, more preferably 5% or more, and most preferably 7% or more.

The average particle size of the inorganic solid electrolyte powder contained in the electrode is preferably 30 μm or less in order to facilitate good dispersibility in the electrode in consideration of the active material particle size and electrode thickness in the electrode. Or less, and most preferably 18 μm or less.
The average particle size of the inorganic solid electrolyte powder contained in the electrode is preferably 150 nm or more, more preferably 200 nm or more, and most preferably 500 nm or more in order to facilitate the dispersion in the electrode and the binding property between the electrode materials. preferable. The average particle diameter is a value of D50 (cumulative 50% diameter) measured by a laser diffraction method. Specifically, a value measured by a particle size distribution measuring device LS100Q or a submicron particle analyzer N5 manufactured by Beckman Coulter, Inc. Can be used. The above-described measuring apparatus is properly used depending on the particle diameter of the object to be measured. When the maximum particle size of the object to be measured is less than 3 μm, measurement is performed using a submicron particle analyzer N5. When the minimum particle diameter of the object to be measured is 0.4 μm or more, measurement is performed using a particle size distribution measuring device LS100Q. When the maximum particle size of the object to be measured is 3 μm or more and the minimum particle size is less than 0.4 μm, first, measurement is performed with LS100Q, and when the peak of the distribution curve is 2 μm or more, the value obtained by measurement with LS100Q is used. When the peak of the distribution curve measured with LS100Q is less than 2 μm, the value obtained by measuring with N5 is used. The average particle diameter is a value expressed on a volume basis.

  The inorganic solid electrolyte powder is preferable because it tends to be composed of one or more of an oxide containing lithium, a compound containing lithium and halogen, and a compound containing lithium and nitrogen. Among these, a lithium ion conductive oxide is more preferable because it has high chemical stability with respect to materials such as an organic solvent used in the battery manufacturing process and a production atmosphere in the air.

Further, the lithium ion conductive inorganic solid electrolyte powder is Li _{1 + x + z} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, 0 ≦ z ≦ 0.6, M = one or more selected from Al, Ga) and having high ion conductivity, lithium in the electrode This is most preferable because it is easy to obtain sufficient conductivity for carrying ion migration.

  The lithium ion conductive crystal is advantageous in terms of ion conduction if it does not include a crystal grain boundary that inhibits ion conduction. In particular, glass ceramics are more preferable because they have almost no vacancies or crystal grain boundaries that hinder ion conduction, and therefore have high ion conductivity and excellent chemical stability.

  Here, the glass ceramic is a material obtained by precipitating a crystalline phase in a glass phase by heat-treating the glass, and means a material composed of an amorphous solid and a crystal. In other words, a material that has undergone phase transition to the above, that is, a material whose crystal content (crystallinity) in the material is 100 mass%. In the case of glass ceramics, even if the material is 100% crystallized, there are almost no voids between crystal grains or in the crystal. On the other hand, ceramics and sintered bodies generally referred to in the production process cannot avoid the presence of vacancies and crystal grain boundaries between crystal grains, and crystals, and can be distinguished from the glass ceramics of the present invention. it can. In particular, with regard to ionic conduction, in the case of ceramics, due to the presence of vacancies and crystal grain boundaries, the conductivity is considerably lower than the conductivity of the crystal grains themselves. Glass ceramics can suppress a decrease in conductivity between crystals by controlling the crystallization process, and it becomes easy to obtain the same conductivity as the conductivity inherent to the crystal grains themselves.

_{Therefore, Li 1 + x + z M} x (Ge 1-y Ti y) 2-x Si z P 3-z O 12 ( where, 0 ≦ x ≦ 0.8,0 ≦ y ≦ 1.0,0 ≦ z ≦ 0. 6, one or more selected from M = Al and Ga) is most preferable as the lithium ion conductive inorganic solid electrolyte powder contained in the electrode.

Li _{1 + x + z} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, 0 ≦ z ≦ 0.6, The glass ceramics on which the lithium ion conductive crystal represented by M = Al or Ga) is expressed in mol% based on the oxide,
Li ₂ O 10-25%, and Al ₂ O ₃ and / or Ga ₂ O ₃ 0-15%, and TiO ₂ and / or GeO ₂ 25-50%, and SiO ₂ 0-15%, and P ₂ O ₅ 26-40%
After obtaining glass by melting and quenching the glass containing each of the above components, the glass can be heat treated to precipitate crystals.

  Here, “mol% based on oxide” means that oxides, nitrates, and the like used as raw materials for the inorganic composition constituents of the present invention are all decomposed and changed to oxides when melted. This is a composition in which each component contained in the glass ceramic is described with the total mass of the generated oxide being 100 mol%.

In the case of the above-mentioned composition, it is possible to easily obtain glass by casting molten glass, and the glass ceramics having the above crystal phase obtained by heat-treating this glass is 1 × 10 ⁻⁴ S / cm to 25 ° C. High lithium ion conductivity of 1 × 10 ⁻³ S / cm.

  The electrolyte (separator) of the all-solid-state lithium secondary battery of the present invention is a polymer such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinyl alcohol, or a perchloric acid as a supporting electrolyte in a polymer matrix of these copolymers. A known material such as a polymer in which lithium, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, or the like is dissolved, or a crosslinked material can be used.

  The all-solid-state lithium secondary battery of the present invention can be produced by laminating the positive electrode, separator, and negative electrode described above in order and thermoforming or laminating and forming the positive electrode / electrolyte and negative electrode / electrolyte, and then bonding or thermocompression bonding. it can.

  Hereinafter, an all-solid lithium secondary battery and an electrode for an all-solid lithium secondary battery according to the present invention will be described with specific examples. In addition, this invention is not limited to what was shown to the following Example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
1) Preparation of lithium ion conductive glass ceramics H ₃ PO ₄ , Al (PO ₃ ) ₃ , Li ₂ CO ₃ , SiO ₂ , and TiO ₂ are used as raw materials, and these are converted to P ₂ O in mol% in terms of oxide. ₅ is 35.0%, Al ₂ O ₃ is 7.5%, Li ₂ O is 15.0%, TiO ₂ is 38.0%, and SiO ₂ is 4.5%. After uniformly mixing, the mixture was placed in a platinum pot and melted by heating in an electric furnace at 1500 ° C. with stirring for 4 hours. Thereafter, the glass melt was dropped into running water to obtain flaky glass, and the glass was crystallized by heat treatment at 950 ° C. for 12 hours to obtain the target glass ceramic. The precipitated crystal phase powder X-ray _{diffractometry, Li 1 + x + z Al} x (Ge 1-y Ti y) 2-x Si z P 3-z O 12 (0 <x ≦ 0.2, y = 1,0 <Z ≦ 0.3) was confirmed to be the main crystal phase. The obtained glass ceramic flakes were pulverized by a lab-scale jet mill and classified by a zirconia rotating roller to obtain a glass ceramic powder having an average particle diameter of 8 μm. Moreover, the ionic conductivity of this glass ceramic was 1.3 * 10 < ^-3 > Scm < ^-1 >.
2) Preparation of positive electrode The volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture is 45 vol%, and the volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture is 27 vol%. A positive electrode was prepared. Details are as follows.
An Al foil having a thickness of 20 μm was used as the positive electrode current collector. 93 wt% of LiCoO ₂ was mixed as an active material, and 7 wt% of acetylene black was mixed as a conductive additive. As a polymer solid electrolyte and an inorganic solid electrolyte in which lithium bistrifluorosulfonylimide is dissolved in a polyethylene oxide polymer, the volume fraction of the lithium ion conductive glass ceramic is 60 vol%. The mixture was weighed and mixed, and NMP (N-methyl-2-pyrrolidone) was added to prepare a paste. This solid electrolyte paste and the previously mixed LiCoO ₂ and acetylene black mixture were weighed so that the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture was 45 vol% in terms of solid content. Was added to prepare a paste. This paste was applied to an Al foil current collector and dried at 100 ° C. Then, it pressed so that an electrode compound material might become dense with a roll press, and it cut | judged to 50 mm square after that, and produced the positive electrode. Here, the average particle diameter of LiCoO ₂ was 8 μm. The inorganic solid electrolyte powder is dispersed in the polymer solid electrolyte. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 27 vol%.
3) Production of Negative Electrode A 18 μm thick Cu foil was used as the negative electrode current collector. 92 wt% of graphite as an active material and 8 wt% of the polymer solid electrolyte used in the positive electrode were mixed, and NMP was added to prepare a paste. This paste was uniformly applied to the negative electrode current collector and dried at 100 ° C. Then, after pressing with a roll press, it cut | judged to 52 square mm and produced the negative electrode. Here, graphite having an average particle diameter of 15 μm was used.
3) Preparation of battery The same polymer solid electrolyte as that used for the electrode on the negative electrode obtained in 2) above after drying each electrode obtained in 2) and 3) in vacuum at 70 ° C. Was applied to laminate a polymer solid electrolyte layer. Thereafter, the positive electrodes obtained in 1) above were stacked and stacked, and housed in a metal laminated resin film case.

Example 2
In the adjustment of the solid electrolyte, the mixture of the solid electrolyte, the active material, and acetylene black, except that the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture was adjusted to 35 vol%, Example 1 A battery was similarly prepared. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 21 vol%.

Example 3
Adjusting the volume fraction of the inorganic solid electrolyte powder in the solid electrolyte to 50 vol%, and adjusting the mixture of the solid electrolyte, the active material, and acetylene black, the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture A battery was produced in the same manner as in Example 1 except that the amount was adjusted to 35 vol%. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 18 vol%.

Example 4
Adjusting the volume fraction of the inorganic solid electrolyte powder in the solid electrolyte to 20 vol%, and adjusting the mixture of the solid electrolyte, the active material, and acetylene black, the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture A battery was produced in the same manner as in Example 1 except that the amount was adjusted to 35 vol%. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 7 vol%.

Example 5
Adjusting the volume fraction of the inorganic solid electrolyte powder in the solid electrolyte to 60 vol%, and adjusting the mixture of the solid electrolyte, the active material, and acetylene black, the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture Was adjusted to 25 vol%. The inorganic solid electrolyte powder used at this time was a lithium ion conductive glass ceramic powder prepared in Example 1, and a powder having an average particle size of 1 μm was prepared by wet ball milling. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 15 vol%. Otherwise, a battery was fabricated in the same manner as in Example 1.

Example 6
Adjusting the volume fraction of the inorganic solid electrolyte powder in the solid electrolyte to 50 vol%, and adjusting the mixture of the solid electrolyte, the active material, and acetylene black, the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture Was adjusted to 25 vol%. The inorganic solid electrolyte powder used at this time was prepared in the same manner as in Example 2, and a powder having an average particle diameter of 0.5 μm was prepared. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 13 vol%. Otherwise, a battery was fabricated in the same manner as in Example 1.

Example 7
Adjusting the volume fraction of the inorganic solid electrolyte powder in the solid electrolyte to 20 vol%, and adjusting the mixture of the solid electrolyte, the active material, and acetylene black, the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture Was adjusted to 20%. The inorganic solid electrolyte powder used at this time was the lithium ion conductive glass ceramic flakes produced in Example 1. The obtained glass ceramic flakes were pulverized by a lab-scale jet mill, and then rotated by a zirconia rotating roller. Classification was carried out so that the average particle size was 18 μm. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 10 vol%. Otherwise, a battery was fabricated in the same manner as in Example 1.

Example 8
Using inorganic solid electrolyte powder LiNbO ₃ (average particle diameter 3 μm), adjusting the volume fraction in the solid electrolyte to 40 vol%, and adjusting the mixture of the solid electrolyte, the active material and acetylene black, the polymer for the electrode mixture A battery was fabricated in the same manner as in Example 1 except that the volume fraction occupied by the solid electrolyte and the inorganic solid electrolyte powder was adjusted to 30 vol%. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 12 vol%.

Example 9
Li ₄ Ti ₅ O ₁₂ (average particle diameter of 11 μm) was used as the inorganic solid electrolyte powder, the volume fraction in the solid electrolyte was adjusted to 40 vol%, and in the adjustment of the mixture of the solid electrolyte, the active material, and acetylene black, A battery was fabricated in the same manner as in Example 1, except that the volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the material was adjusted to 30 vol%. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 12 vol%.

Example 10
Using LiF (average particle size 0.9 μm) as the inorganic solid electrolyte powder, adjusting the volume fraction in the solid electrolyte to 30 vol%, and adjusting the mixture of the solid electrolyte, the active material, and acetylene black, A battery was fabricated in the same manner as in Example 1 except that the volume fraction occupied by the molecular solid electrolyte and the inorganic solid electrolyte powder was adjusted to 40 vol%. The volume fraction of the inorganic solid electrolyte powder with respect to the electrode mixture was 12 vol%.

Example 11
LiFePO ₄ , AB, lithium ion conductive glass ceramics, and Pvdf were weighed to 73: 7: 5: 15 wt% and mixed with NMP to prepare a positive electrode mixture slurry. As the lithium ion conductive glass ceramics, the glass ceramic flakes produced in Example 1 were used, and the powders had an average particle diameter of 1 μm.
The adjusted positive electrode mixture slurry was applied to an Al foil current collector, dried, and pressed with a roll press. The porosity was calculated from the bulk density of the positive electrode mixture layer at this time, and the porosity was 26%. The polymer electrolyte slurry was applied from above the mixture layer, and the polymer electrolyte was infiltrated into the mixture. Coating and drying were repeated several times to produce a positive electrode. The volume fraction occupied by the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture was 39 vol%, and the volume fraction of the inorganic solid electrolyte powder was 13 vol%.
Further, Li ₄ Ti ₅ O ₁₂ (average particle diameter 11 μm), acetylene black, lithium ion conductive glass ceramic powder having the same average particle diameter 1 μm as above, and Pvdf were weighed so as to be 80: 5: 5: 10 wt%. The negative electrode mixture slurry was prepared by mixing with NMP. This was applied to a Cu foil current collector, dried, and pressed with a roll press. The porosity of the negative electrode mixture layer at this time was calculated, and the porosity was 22%. Thereafter, a polymer electrolyte slurry was applied in the same manner as the positive electrode to produce a negative electrode. The volume fraction of the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture was 30 vol%, and the volume fraction of the inorganic solid electrolyte powder was 8 vol%.
These positive electrode, negative electrode and polymer solid electrolyte film (30 μm) were bonded together and stored in a metal laminated resin film case.

Example 12
LiMn ₂ O ₄ , AB, the same lithium ion conductive glass ceramic powder as in Example 11 as an inorganic solid electrolyte powder, Pvdf was weighed to 80: 5: 5: 10 wt%, mixed with NMP, and mixed with positive electrode The slurry was adjusted.
This was applied to an Al foil current collector, dried, and pressed with a roll press. The porosity was calculated from the bulk density of the positive electrode mixture layer at this time, and the porosity was 24%. The polymer electrolyte slurry was applied from above the mixture layer, and the polymer electrolyte was infiltrated into the mixture. Coating and drying were repeated several times to produce a positive electrode. The volume fraction of the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture was 34 vol%, and the volume fraction of the inorganic solid electrolyte powder was 10 vol%. As the lithium ion conductive glass ceramics, the glass ceramic flakes produced in Example 1 were used, and a powder having an average particle diameter of 3 μm was used. A battery was made in the same manner as Example 11 except for the above.

<< Comparative Example 1 >>
A battery was fabricated in the same manner as in Example 1, except that all of the inorganic solid electrolyte powder used in Example 1 was replaced with a polymer solid electrolyte.

  The batteries produced in the above examples were stored at 60 ° C. for 2 days, and then charged and discharged at a current value of 1/10 C by a constant current-constant voltage charge-constant current discharge method. In addition, resistance measurement before and after the charge / discharge cycle was performed by an AC impedance method. Table 1 shows the rate of increase in resistance at the cell impedance after the first discharge and after 50 cycles. In addition, in each of the batteries of the examples, the output capacity is obtained by converting the discharge capacity per charge capacity when the battery is discharged at a current value of 1/4 C after being fully charged by constant current-constant voltage charging. To do. In Table 1, “solid electrolyte volume fraction” indicates the total volume fraction of the polymer solid electrolyte and the inorganic solid electrolyte powder with respect to the electrode mixture.

  From the above, the effect of suppressing the increase in battery impedance can be obtained by mixing a specific amount of the inorganic solid electrolyte with at least one of the electrodes of the all-solid lithium secondary battery using the solid polymer electrolyte of the present invention. It can be seen that the output characteristics and cycle stability can be improved.

Conceptual diagram of electrode mixture of the present invention Conceptual diagram of conventional electrodes

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode active material 2 Electrode current collector 3 Polymer solid electrolyte 4 Conductive aid 5 Inorganic solid electrolyte powder 6 Inorganic solid electrolyte coating layer

Claims (14)

  In at least one electrode, the ratio of the polymer solid electrolyte and the inorganic solid electrolyte powder to the electrode mixture containing the active material, the conductive additive, the polymer solid electrolyte, and the inorganic solid electrolyte powder is 50% in volume fraction. An all-solid-state lithium secondary battery having an electrode that is less than   2. The all solid lithium secondary battery according to claim 1, wherein the inorganic solid electrolyte powder is dispersed in the polymer solid electrolyte.   3. The all-solid-state lithium secondary battery according to claim 1, wherein in at least one electrode, the proportion of the inorganic solid electrolyte powder in the electrode mixture is less than 30% in terms of volume fraction.   The all-solid-state lithium secondary battery according to any one of claims 1 to 3, wherein the inorganic solid electrolyte powder has an average particle size of 30 µm or less.   The inorganic solid electrolyte powder is made of any one or more of an oxide containing lithium, a compound containing lithium and halogen, and a compound containing lithium and nitrogen. The all-solid-state lithium secondary battery described.   The all-solid-state lithium secondary battery according to any one of claims 1 to 5, wherein the inorganic solid electrolyte powder is a lithium ion conductive oxide. The inorganic solid electrolyte powder is Li _{1 + x + z} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, 0 ≦ 7. The all-solid-state lithium secondary battery according to claim 1, comprising a crystal of z ≦ 0.6 and one or more selected from M = Al and Ga.   All solid type in which the proportion of the polymer solid electrolyte and the inorganic solid electrolyte powder is less than 50% of the electrode mixture containing the active material, the conductive additive, the polymer solid electrolyte and the inorganic solid electrolyte powder. Electrode for lithium secondary battery.   The electrode for an all-solid-state lithium secondary battery according to claim 8, wherein the inorganic solid electrolyte powder is dispersed in the polymer solid electrolyte.   The electrode for an all-solid-state lithium secondary battery according to claim 8 or 9, wherein the proportion of the inorganic solid electrolyte powder in the electrode mixture is less than 30% in terms of volume fraction.   The electrode for an all solid-state lithium secondary battery according to any one of claims 8 to 10, wherein an average particle size of the inorganic solid electrolyte powder is 30 µm or less.   The inorganic solid electrolyte powder is composed of any one or more of an oxide containing lithium, a compound containing lithium and halogen, and a compound containing lithium and nitrogen. An electrode for the all-solid-state lithium secondary battery described.   The electrode for an all solid-state lithium secondary battery according to any one of claims 8 to 12, wherein the inorganic solid electrolyte powder is a lithium ion conductive oxide. The inorganic solid electrolyte powder is Li _{1 + x + z} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, 0 ≦ 14. The electrode for an all solid-state lithium secondary battery according to claim 8, comprising a crystal of z ≦ 0.6 and one or more selected from M = Al and Ga.