JP2019192609A - All-solid lithium battery and method of manufacturing the same - Google Patents

Abstract

To make it possible to remarkably improve charge and discharge performance in an all-solid lithium battery using a solid electrolyte member including a low angle orientation positive electrode plate and a solid electrolyte represented by a composition formula 3 LiOH LiSO.SOLUTION: The all-solid lithium battery includes: a low-angle-oriented positive electrode plate that is a lithium composite oxide sintered plate having porosity of from 0% or more and 10% or less; a negative electrode plate, containing Ti, capable of inserting and removing lithium ions at 0.4 V (vs. Li/Li) or higher; and a solid electrolyte member including a solid electrolyte represented by a composition formula 3 LiOH LiSO.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an all solid lithium secondary battery (hereinafter referred to as an all solid lithium battery) and a method for producing the same.

  As a positive electrode active material layer for a lithium secondary battery (also called a lithium ion secondary battery), a powder of a lithium composite oxide (typically a lithium transition metal oxide) and an additive such as a binder or a conductive agent A powder-dispersed positive electrode obtained by kneading and molding is widely known. Such a powder-dispersed positive electrode contains a relatively large amount of binder (for example, about 10% by weight) that does not contribute to capacity, so that the packing density of the lithium composite oxide as the positive electrode active material is low. For this reason, the powder-dispersed positive electrode has much room for improvement in terms of capacity and charge / discharge efficiency.

Therefore, attempts have been made to improve capacity and charge / discharge efficiency by forming the positive electrode or the positive electrode active material layer with a lithium composite oxide sintered plate. In this case, since the binder is not contained in the positive electrode or the positive electrode active material layer, it is expected that high capacity and good charge / discharge efficiency can be obtained by increasing the packing density of the lithium composite oxide. For example, Patent Document 1 (International Publication No. 2017/146088) discloses a plurality of primary elements composed of a lithium composite oxide such as lithium cobalt oxide (LiCoO ₂ ) as a positive electrode of a lithium secondary battery including a solid electrolyte member. It is disclosed to use a low-angle-oriented positive electrode plate including particles, in which (003) planes of a plurality of primary particles are oriented at an average orientation angle of more than 0 ° and 30 ° or less with respect to the plate surface of the positive electrode plate. Yes. By the above orientation, stress generated at the interface between the positive electrode plate and the solid electrolyte member during charge / discharge is relaxed. That is, the expansion and contraction rate in the plate surface direction of the positive electrode plate can be reduced to relieve the stress generated at the interface between the positive electrode plate and the solid electrolyte member, thereby causing defects in the solid electrolyte member and the positive electrode from the solid electrolyte member. The peeling of the plate can be suppressed.

It is also known that the negative electrode or the positive electrode active material layer is composed of a lithium composite oxide sintered plate. For example, Patent Document 2 (Japanese Patent Application Laid-Open No. 2015-185337) includes a positive electrode, a negative electrode, and a solid electrolyte member, and uses a lithium titanate (Li ₄ Ti ₅ O ₁₂ ) sintered body for the positive electrode or the negative electrode. A solid state battery is disclosed. The sintered body disclosed in this document is dense with a relative density (dense) of 90% or more. This can be said to be based on a general understanding that the positive electrode and the negative electrode are desirably dense in order to increase the energy density of the all-solid-state secondary battery.

By the way, a lithium ion conductive material having an inverted perovskite structure has been proposed as a solid electrolyte having high lithium ion conductivity. For example, Patent Document 3 (International Publication No. 2012/112229) describes Li ₃ OCl and Li _(3-x) M _{x / 2} OA (where 0 ≦ x ≦ 0.8, M is Mg, Ca, A solid electrolyte having excellent lithium ion conductivity, wherein at least one selected from the group consisting of Ba and Sr, and A is at least one selected from the group consisting of F, Cl, Br and I) It is disclosed as. Non-Patent Document 1 (Yutao Li et al., “Fluorine-Doped Antiperovskite Electrolyte for All-Solid-State Lithim-Ion Batteries”, Angew. Chem. Int. Ed. 2016, 55, 9965-9968) Li ₂ OHX (wherein X is Cl or Br) is promising as a solid electrolyte for an all-solid secondary battery, and the Li ₂ OHCl is doped with fluorine to partially convert OH ⁻ into F ⁻ It is disclosed that the compound partially substituted in (1) exhibits electrochemical stability suitable for an all-solid-state secondary battery.

International Publication No. 2017/146088 Japanese Patent Laying-Open No. 2015-185337 International Publication No. 2012/112229

Yutao Li et al., "Fluorine-Doped Antiperovskite Electrolyte for All-Solid-State Lithim-Ion Batteries", Angew. Chem. Int. Ed. 2016, 55, 9965-9968

The present inventors initially thought that a high-performance all-solid lithium battery could be produced by using the low-angle-oriented positive electrode plate, the negative electrode plate, and the solid electrolyte as described above. However, when such an all-solid lithium battery was actually produced, it was found that a battery with significantly poor charge / discharge performance may exist among the produced batteries. This is a peculiar problem that occurs when a battery configuration such as that described above, including a solid electrolyte such as Li ₃ OCl, is employed.

The present inventors have now used a solid electrolyte represented by a composition formula 3LiOH · Li ₂ SO ₄ , and the charge / discharge performance of the low angle oriented positive electrode plate is 0% or more and 10% or less. The knowledge that it can improve remarkably was acquired.

Accordingly, an object of the present invention is to significantly improve charge / discharge performance in an all-solid-state lithium battery using a solid electrolyte member including a low-angle-oriented positive electrode plate and a solid electrolyte represented by a composition formula 3LiOH · Li ₂ SO _4. There is in being able to.

According to one aspect of the present invention, there is provided an oriented positive electrode plate which is a lithium composite oxide sintered body plate having a porosity of 0% or more and 10% or less, wherein the lithium composite oxide sintered body plate is a lithium composite oxide sintered plate. An alignment positive electrode plate comprising a plurality of primary particles composed of a material, wherein the plurality of primary particles are aligned at an average alignment angle of more than 0 ° and 30 ° or less with respect to the plate surface of the alignment positive electrode plate;
A negative electrode plate containing Ti and capable of inserting and extracting lithium ions at 0.4 V (vs. Li / Li ⁺ ) or higher;
A solid electrolyte member including a solid electrolyte represented by a solid electrolyte represented by a composition formula 3 LiOH · Li ₂ SO ₄ ;
An all-solid lithium battery is provided.

According to another aspect of the present invention, there is provided a method for producing the all solid lithium battery,
Placing a solid electrolyte member containing a solid electrolyte represented by a composition formula 3LiOH · Li ₂ SO ₄ on the positive electrode plate or the negative electrode plate;
Placing the negative electrode plate or the positive electrode plate on the solid electrolyte powder;
Pressing the negative electrode plate toward the positive electrode plate or the positive electrode plate toward the negative electrode plate;
A method for producing an all-solid lithium battery is provided.

It is a schematic cross section which shows an example of the all-solid-state lithium battery of this invention.

(Configuration of all-solid lithium battery)
FIG. 1 schematically shows an example of the all solid lithium battery of the present invention. An all solid lithium battery 10 shown in FIG. 1 includes an oriented positive electrode plate 12, a solid electrolyte member 14, and a negative electrode plate 16.

  The oriented positive electrode plate 12 is a lithium composite oxide sintered body plate having a porosity of 0% or more and 10% or less. This lithium composite oxide sintered plate includes a plurality of primary particles composed of a lithium composite oxide, and the plurality of primary particles has an average orientation angle of more than 0 ° and not more than 30 ° with respect to the plate surface of the oriented positive electrode plate. It is a so-called “low angle oriented positive electrode plate” oriented at

The solid electrolyte member 14 includes a solid electrolyte represented by the following composition formula (1).
Composition formula (1)... 3LiOH.Li ₂ SO ₄

The negative electrode plate 16 is a negative electrode plate capable of inserting and extracting lithium ions at 0.4 V (vs. Li / Li ⁺ ) or higher, and contains Ti.

  Thus, charge / discharge performance in an all-solid-state lithium battery is obtained by using the low-angle-oriented positive electrode plate 12 having a porosity of 0% or more and 10% or less and the solid electrolyte member 14 containing the solid electrolyte of the composition formula (1). Can be remarkably improved.

  As described above, the present inventors may be able to produce a high-performance all-solid-state lithium battery by using a low-angle-oriented positive electrode plate, a negative electrode plate, and a solid electrolyte as disclosed in Patent Documents 1 to 3. Initially thought. However, when such an all-solid-state lithium battery was actually produced, there were cases where batteries having high battery resistance and remarkably poor charge / discharge performance existed among the produced batteries. The cause is not clear, but it can be solved conveniently by using a solid electrolyte member containing the solid electrolyte of the above composition formula (1) and setting the porosity of the low-angle oriented positive electrode plate to 0% or more and 10% or less. Thus, the charge / discharge performance can be remarkably improved.

  The alignment positive electrode plate 12 is a lithium composite oxide sintered body plate. The lithium composite oxide sintered body plate includes a plurality of primary particles composed of a lithium composite oxide having a layered rock salt structure, and the plurality of primary particles are more than 0 ° and 30 ° with respect to the plate surface of the oriented positive electrode plate. Orientation is performed at the following average orientation angle.

  The oriented positive plate 12 is an oriented sintered body composed of a plurality of primary particles 11 bonded to each other. Each primary particle 11 is mainly plate-shaped, but may include particles formed in a rectangular parallelepiped shape, a cubic shape, a spherical shape, or the like. The cross-sectional shape of each primary particle 11 is not particularly limited, and may be a rectangle, a polygon other than a rectangle, a circle, an ellipse, or a complex shape other than these.

Each primary particle 11 is composed of a lithium composite oxide. The lithium composite oxide is Li _x MO ₂ (0.05 <x <1.10, M is at least one transition metal, and M is typically 1 of Co, Ni, Mn, and Al. Oxide containing a species or more). The lithium composite oxide has a layered rock salt structure. The layered rock salt structure is a crystal structure in which lithium layers and transition metal layers other than lithium are alternately stacked with oxygen layers in between, that is, the transition metal ion layer and the lithium single layer are alternately arranged via oxide ions. It refers to a laminated crystal structure (typically an α-NaFeO ₂ type structure, ie, a structure in which transition metals and lithium are regularly arranged in the [111] axis direction of a cubic rock salt type structure). Examples of the lithium composite oxide include Li _x CoO ₂ (lithium cobaltate), Li _x NiO ₂ (lithium nickelate), Li _x MnO ₂ (lithium manganate), Li _x NiMnO ₂ (nickel / lithium manganate) , Li _x NiCoO ₂ (nickel / lithium cobaltate), Li _x CoNiMnO ₂ (cobalt / nickel / lithium manganate), Li _x CoMnO ₂ (cobalt / lithium manganate), and the like, particularly preferably Li _x CoO _2. (Lithium cobaltate, typically LiCoO ₂ ). The lithium composite oxide includes Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, Sn, Sb, Te, Ba One or more elements selected from Bi, Bi, and W may be included.

  The average value of the orientation angles of the primary particles 11, that is, the average orientation angle is more than 0 ° and not more than 30 °. This provides the following various advantages. First, since each primary particle 11 is in a state of lying in a direction inclined with respect to the thickness direction, the adhesion between the primary particles can be improved. As a result, since the lithium ion conductivity between a certain primary particle 11 and other primary particles 11 adjacent to both sides in the longitudinal direction of the primary particle 11 can be improved, rate characteristics can be improved. Second, cycle characteristics can be improved. That is, when each primary particle 11 expands and contracts in the direction perpendicular to the (003) plane in accordance with the entry and exit of lithium ions, the orientation positive electrode in the plate plane direction is reduced by reducing the inclination angle of the (003) plane with respect to the plate plane direction. The expansion / contraction amount of the plate 12 is reduced, and it is possible to suppress the occurrence of stress between the oriented positive electrode plate 12 and the solid electrolyte member 14. Third, rate characteristics can be further improved. As described above, when the lithium ion enters and exits, in the alignment positive electrode plate 12, the expansion / contraction in the thickness direction is more dominant than the plate surface direction, so that the expansion / contraction of the alignment positive electrode plate 12 becomes smooth. This is because lithium ions can go in and out smoothly.

  The average orientation angle of the primary particles 11 is determined by (i) polishing the positive electrode plate with a cross section polisher (CP), and (ii) obtaining a cross section of the positive electrode plate (a cross section perpendicular to the plate surface of the positive electrode plate) at a predetermined magnification ( (Eg, 1000 times) and a predetermined field of view (for example, 125 μm × 125 μm), and (iii) For all particles specified in the obtained EBSD image, the (003) plane of primary particles and the plate surface of the positive electrode plate Can be determined by calculating the average value of these angles (iv). The average orientation angle of the primary particles 11 is preferably 30 ° or less, more preferably 25 ° or less, from the viewpoint of further improving the rate characteristics. The average orientation angle of the primary particles 11 is preferably 2 ° or more, more preferably 5 ° or more, from the viewpoint of further improving the rate characteristics.

  The orientation angle of each primary particle 11 may be widely distributed from 0 ° to 90 °, but most of the primary particles 11 are preferably distributed in the region of more than 0 ° and not more than 30 °. That is, the oriented sintered body constituting the oriented positive electrode plate 12 is obtained by analyzing the cross section (cross section perpendicular to the plate surface of the positive electrode plate) by EBSD, and the oriented positive electrode among the primary particles 11 included in the analyzed cross section. The total area of primary particles 11 (hereinafter referred to as low-angle primary particles) whose orientation angle with respect to the plate surface of the plate 12 is greater than 0 ° and 30 ° or less is the primary particle 11 (specifically, the average orientation angle) included in the cross section. The total area of 30 primary particles 11) used for the calculation is preferably 70% or more, more preferably 80% or more. Thereby, since the ratio of the primary particle 11 with high mutual adhesiveness can be increased, rate characteristics can be further improved. The total area of the low-angle primary particles having an orientation angle of 20 ° or less is more preferably 50% or more with respect to the total area of the 30 primary particles 11 used for calculating the average orientation angle. . Furthermore, the total area of the low-angle primary particles having an orientation angle of 10 ° or less is more preferably 15% or more with respect to the total area of the 30 primary particles 11 used for calculating the average orientation angle. .

  Since each primary particle 11 is mainly plate-shaped, in the cross section perpendicular to the plate surface of the positive electrode plate, the cross section of each primary particle 11 extends in a predetermined direction, and typically has a substantially rectangular shape. That is, when the cross section of the oriented sintered body is analyzed by EBSD, the total area of the primary particles 11 having an aspect ratio of 4 or more among the primary particles 11 included in the analyzed cross section is included in the cross section. The total area of the particles 11 (specifically, 30 primary particles 11 used for calculating the average orientation angle) is preferably 70% or more, more preferably 80% or more. Thereby, the mutual adhesion between the primary particles 11 can be further improved, and as a result, the rate characteristics can be further improved. The aspect ratio of the primary particles 11 is a value obtained by dividing the maximum ferret diameter of the primary particles 11 by the minimum ferret diameter. The maximum ferret diameter is the maximum distance between the straight lines when the primary particle 11 is sandwiched between two parallel lines on the EBSD image obtained by analyzing the cross section perpendicular to the plate surface of the positive electrode plate by EBSD. The minimum ferret diameter is the minimum distance between the straight lines when the primary particle 11 is sandwiched between two parallel lines on the EBSD image obtained by analyzing the cross section perpendicular to the plate surface of the positive electrode plate by EBSD.

  The average particle size of the plurality of primary particles constituting the oriented sintered body is preferably 5 μm or more. Specifically, the average particle diameter of the 30 primary particles 11 used for calculating the average orientation angle is preferably 5 μm or more, more preferably 7 μm or more, and further preferably 12 μm or more. Thereby, since the number of grain boundaries between the primary particles 11 in the direction in which lithium ions are conducted is reduced and the lithium ion conductivity as a whole is improved, the rate characteristics can be further improved. The average particle diameter of the primary particles 11 is a value obtained by arithmetically averaging the equivalent circle diameters of the primary particles 11. The equivalent circle diameter is the diameter of a circle having the same area as each primary particle 11 on the EBSD image.

  The porosity of the lithium composite oxide sintered body plate constituting the aligned positive electrode plate 12 is 0% or more and 10% or less, preferably 0% or more and 8% or less, more preferably 0% or more and 5% or less, and still more preferably. It is 0% or more and 3% or less. When the porosity is within such a range, significant improvement in charge / discharge performance can be realized. The porosity of the aligned positive electrode plate 12 is the volume ratio of the voids in the aligned positive electrode plate 12. This porosity can be measured by image analysis of an SEM image of a cross section perpendicular to the plate surface of the positive electrode plate. For example, (i) a sintered body plate is processed with a cross section polisher (CP) to expose a polished cross section, and (ii) the polished cross section is subjected to a predetermined magnification (for example, 1000 times) and a predetermined field of view (for example, 125 μm × 125 μm). ) By SEM (scanning electron microscope), (iii) image analysis of the obtained SEM image, and divide the area of all voids in the field of view by the area (cross-sectional area) of the sintered body plate in the field of view. The porosity (%) can be obtained by multiplying the obtained value by 100.

The thickness of the alignment positive electrode plate 12 is 30 μm or more, preferably 40 μm or more, particularly preferably 50 μm or more, from the viewpoint of improving the energy density of the all-solid lithium battery 10 by increasing the active material capacity per unit area. Preferably it is 55 micrometers or more. Although the upper limit value of the thickness is not particularly limited, the thickness of the alignment positive electrode plate 12 is preferably less than 200 μm, more preferably from the viewpoint of suppressing deterioration of battery characteristics (particularly increase in resistance value) due to repeated charge and discharge. It is 150 μm or less, more preferably 120 μm or less, particularly preferably 100 μm or less, most preferably 90 μm or less, 80 μm or less, or 70 μm or less. Further, the size of the oriented positive electrode plate is preferably 5 mm × 5 mm square or more, more preferably 10 mm × 10 mm square or more, and in other words, preferably 25 mm ² or more, more preferably 100 mm ² or more.

  A positive electrode current collector 13 is preferably provided on the surface of the oriented positive electrode plate 12 on the side away from the solid electrolyte member 14. In addition, a negative electrode current collector 17 is preferably provided on the surface of the negative electrode plate 16 on the side away from the solid electrolyte member 14. Examples of materials constituting the positive electrode current collector 13 and the negative electrode current collector 17 include platinum (Pt), platinum (Pt) / palladium (Pd), gold (Au), silver (Ag), aluminum (Al), Examples thereof include copper (Cu) and ITO (indium-tin oxide film).

  The alignment positive electrode plate 12, the solid electrolyte member 14 and the negative electrode plate 16 are accommodated in a container 18. The container 18 is not particularly limited as long as it can accommodate a unit cell or a stack in which a plurality of unit batteries are stacked in series or in parallel. In particular, since the all-solid lithium battery 10 has no fear of electrolyte leakage, the container 18 can adopt a relatively simple container form and may be packaged with an exterior material. For example, a chip form for mounting on an electronic circuit or a laminate cell form (for example, a multilayer product of aluminum (Al) / polypropylene (PP)) for thin and wide space applications can be employed. A structure in which the positive electrode current collector 13 and / or the negative electrode current collector 17 also serves as a part of the container 18 may be employed. In order to further improve the heat resistance, a heat resistant resin such as PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), polyimide, polyamide or the like may be used instead of polypropylene. .

A typical form of the solid electrolyte member 14 is a solid electrolyte layer. As the solid electrolyte member 14, a mixture obtained by mixing LiOH raw material powder and Li ₂ SO ₄ raw material powder in a molar ratio of 4: 1 to 3: 1 is heated in an Ar atmosphere (400 to 450 ° C., 0.1 to 1). It is possible to use a solidified product obtained by quenching the melt that has been melted for a long time. This solidified product is a solid electrolyte member including a solid electrolyte represented by a composition formula 3LiOH · Li ₂ SO ₄ . That is, this solidified product is not only composed of a solid electrolyte represented by the composition formula 3LiOH · Li ₂ SO ₄ but also a composition formula xLiOH · yLi ₂ SO ₄ (for example, x = 4, y = The solid electrolyte member is allowed to contain the solid electrolyte represented by 1) at the same time. Needless to say, the solid electrolyte member 14 may include solid electrolytes composed of different constituent elements while including a solid electrolyte represented by the composition formula 3LiOH · Li ₂ SO ₄ .

The dimension of the solid electrolyte member 14 is not particularly limited, but the thickness of the solid electrolyte layer is preferably 0.0005 mm to 1.0 mm, more preferably 0.001 mm to 0.00 mm, from the viewpoints of charge / discharge rate characteristics and mechanical strength. 1 mm, more preferably 0.002 to 0.05 mm. The thickness of the solid electrolyte layer may be controlled by a solid electrolytic mass placed on the positive electrode plate 12 (or the negative electrode plate 16), or may be controlled by a spacer used during pressing. The type of the spacer to be used in is not particularly limited, for example, _Al 2 _O 3, MgO, may be used ceramics such as ZrO _2.

The negative electrode plate 16 is a negative electrode plate capable of inserting and desorbing lithium ions at 0.4 V (vs. Li / Li ⁺ ) or higher, and contains Ti. The negative electrode active material satisfying such conditions is preferably an oxide containing at least Ti. Preferable examples of such a negative electrode active material include lithium titanate Li ₄ Ti ₅ O ₁₂ (hereinafter referred to as LTO), niobium titanium composite oxide Nb ₂ TiO ₇ , and titanium oxide TiO ₂ , more preferably LTO and Nb. ₂ TiO ₇ , more preferably LTO. Note that LTO is typically known to have a spinel structure, but other structures may be employed during charging and discharging. For example, the reaction of LTO proceeds in a two-phase coexistence of Li ₄ Ti ₅ O ₁₂ (spinel structure) and Li ₇ Ti ₅ O ₁₂ (rock salt structure) during charge and discharge. Therefore, LTO is not limited to a spinel structure.

The negative electrode plate 16 is preferably a sintered plate (for example, LTO or Nb ₂ TiO ₇ sintered plate). In the case of a sintered body plate, since the negative electrode plate does not contain a binder, high capacity and good charge / discharge efficiency can be obtained by increasing the packing density of the negative electrode active material (for example, LTO or Nb ₂ TiO ₇ ). Can do. The reason why the binder is not contained in the negative electrode plate is that the binder disappears or burns out during firing even if the binder is contained in the green sheet. The LTO sintered body plate can be manufactured according to the method described in Patent Document 2 (Japanese Patent Laid-Open No. 2015-185337).

  The negative electrode plate 16 may be dense or may include voids. When the negative electrode plate 16 includes voids, the stress generated by the expansion and contraction of the crystal lattice associated with the entry and exit of lithium ions in the charge / discharge cycle is released satisfactorily (uniformly) by the voids. There is an advantage that generation of boundary cracks is suppressed as much as possible.

  The porosity of the negative electrode plate 16 is preferably 2 to 40%, more preferably 3 to 30%. Within such a range, it is possible to desirably realize the stress releasing effect due to the air gap and the effect of increasing the capacity. The porosity of the negative electrode plate 16 is the volume ratio of the voids in the negative electrode plate 16 and is measured by image analysis of the cross-sectional SEM image of the negative electrode plate 16 in the same manner as the porosity of the aligned positive electrode plate 12 described above. Can be measured.

The thickness of the negative electrode plate 16 is 25 μm or more, preferably 30 μm or more, more preferably 40 μm or more, from the viewpoint of improving the energy density of the all-solid lithium battery 10 by increasing the active material capacity per unit area. Especially preferably, it is 50 micrometers or more, Most preferably, it is 55 micrometers or more. Although the upper limit of the thickness is not particularly limited, the thickness of the negative electrode plate 16 is preferably 400 μm or less, more preferably 300 μm, from the viewpoint of suppressing deterioration of battery characteristics (particularly an increase in resistance value) due to repeated charge / discharge. It is as follows. Moreover, the size of the negative electrode plate 16 is preferably 5 mm × 5 mm square or more, more preferably 10 mm × 10 mm square or more. In other words, the size is preferably 25 mm ² or more, more preferably 100 mm ² or more.

As described above, the oriented positive plate 12 is preferably a LiCoO ₂ (LCO) sintered plate, and the negative plate 16 is preferably a Li ₄ Ti ₅ O ₁₂ (LTO) sintered plate. In particular, when the average value of the orientation angle of the LCO-oriented positive electrode plate, that is, when the average orientation angle is more than 0 ° and 30 ° or less, expansion / shrinkage does not occur in the surface direction during charge / discharge, and the LTO negative electrode plate also expands during charge / discharge. Since no contraction occurs and the solid electrolyte member 14 does not expand or contract during charge / discharge, stress (particularly, stress at the interface between the oriented positive electrode plate 12 or the negative electrode plate 16 and the solid electrolyte member 14) does not occur during charge / discharge. Can be performed stably. For the same purpose as described above, when an Nb ₂ TiO ₇ sintered body plate is used as the negative electrode plate 16, primary particles constituting the Nb ₂ TiO ₇ sintered body plate are oriented so as to control expansion and contraction. Is preferred.

  The all-solid-state lithium battery 10 of the present invention can be charged and discharged at room temperature, but is preferably charged and discharged at a temperature of 100 ° C. or higher. By charging / discharging at a temperature of 100 ° C. or higher, rapid charge / discharge can be realized with a high cycle capacity maintenance rate. That is, rapid charging / discharging becomes possible by charging / discharging the all-solid-state lithium battery 10 at a high temperature of 100 ° C. or higher. That is, the all solid lithium battery 10 can be driven at a high speed and stably at the above temperature. In addition, a high capacity can be maintained even when rapid charge / discharge is repeated, that is, a high cycle capacity maintenance ratio can be realized. Therefore, the preferable operating temperature of the all-solid-state lithium battery 10 at the time of charging / discharging is 100 degreeC or more, More preferably, it is 100-300 degreeC, More preferably, it is 100-200 degreeC, Most preferably, it is 100-150 degreeC. The heating means for realizing the operating temperature can be various heaters or various devices or devices that generate heat, and a preferable example is an electrically heated ceramic heater. In other words, the all solid lithium battery 10 of this embodiment is preferably provided as a secondary battery system with heating means.

(Manufacturing method of the alignment positive electrode plate 12)
1. Preparation of LiCoO ₂ Template Particles Co ₃ O ₄ raw material powder and Li ₂ CO ₃ raw material powder are mixed and fired (500 to 900 ° C. for 1 to 20 hours) to synthesize LiCoO ₂ powder.

The obtained LiCoO ₂ powder is pulverized to a volume-based D50 particle size of 0.1 μm to 10 μm by a pot mill, whereby plate-like LiCoO ₂ particles capable of conducting lithium ions in parallel with the plate surface are obtained. The obtained LiCoO ₂ particles are easily cleaved along the cleavage plane. It is to cleave by crushing the LiCoO ₂ particles to prepare a LiCoO ₂ template particles.

Such LiCoO ₂ particles can be obtained by a method of crushing after growing a green sheet using LiCoO ₂ powder slurry, a plate method such as a flux method, hydrothermal synthesis, single crystal growth using a melt, or a sol-gel method. It can also be obtained by a method of synthesizing crystals.

  In this step, the profile of the primary particles constituting the aligned positive electrode plate 12 can be controlled as described below.

First, by adjusting at least one of the aspect ratio and the particle size of the LiCoO ₂ template particles, the total area ratio of the low-angle primary particles whose orientation angle is greater than 0 ° and 30 ° or less can be controlled. Specifically, the larger the aspect ratio of LiCoO ₂ template particles, also, the larger the particle size of the LiCoO ₂ template particles, it is possible to increase the total area ratio of the low-angle primary particles.

Each of the aspect ratio and the particle size of the LiCoO ₂ template particles is the particle size of the Co ₃ O ₄ raw material powder and the Li ₂ CO ₃ raw material powder, and the pulverization conditions during pulverization (such as pulverization time, pulverization energy, pulverization technique), and It can be adjusted by at least one of the classification after pulverization.

Moreover, the average particle diameter of the primary particles can be controlled by adjusting the particle diameter of the LiCoO ₂ template particles.

Further, the density of the aligned positive electrode plate 12 can be controlled by adjusting the particle size of the LiCoO ₂ template particles. Specifically, the density of the aligned positive electrode plate 12 can be increased as the particle size of the LiCoO ₂ template particles is reduced.

2. Preparation of matrix particles Co ₃ O ₄ raw material powder is used as matrix particles. The volume-based D50 particle size of the Co ₃ O ₄ raw material powder is not particularly limited and can be, for example, 0.1 to 1.0 μm, but is preferably smaller than the volume-based D50 particle size of LiCoO ₂ template particles. The matrix particles can also be obtained by subjecting a Co (OH) ₂ raw material to heat treatment at 500 ° C. to 800 ° C. for 1 to 10 hours. In addition to Co ₃ O ₄ , Co (OH) ₂ particles or LiCoO ₂ particles may be used as matrix particles.

  In this step, the profile of the primary particles constituting the aligned positive electrode plate 12 can be controlled as described below.

First, by adjusting the ratio of the particle size of the matrix particles to the particle size of the LiCoO ₂ template particles (hereinafter referred to as “matrix / template particle size ratio”), the orientation angle is less than 0 ° and less than 30 °. The total area ratio of the primary particles can be controlled. Specifically, the smaller the matrix / template particle size ratio, that is, the smaller the particle size of the matrix particles, the easier it is for the matrix particles to be incorporated into the LiCoO ₂ template particles in the firing step described later. The total area ratio can be increased.

  Further, the density of the aligned positive electrode plate 12 can be controlled by adjusting the matrix / template particle size ratio. Specifically, the smaller the matrix / template particle size ratio, that is, the smaller the particle size of the matrix particles, the higher the density of the aligned positive electrode plate 12 can be.

3. Preparation of green sheet While mixing powder, dispersion medium, binder, plasticizer and dispersant in which LiCoO ₂ template particles and matrix particles are mixed in a ratio of 100: 3 to 3:97, the mixture is stirred and degassed under reduced pressure. A slurry is prepared by adjusting to the desired viscosity.

Next, a molded body is formed by molding the prepared slurry using a molding technique capable of applying a shearing force to LiCoO ₂ template particles. Thereby, the average orientation angle of each primary particle can be made to be more than 0 ° and not more than 30 °.

A doctor blade method is suitable as a forming technique capable of applying a shearing force to LiCoO ₂ template particles. When the doctor blade method is used, a green sheet as a molded body is formed by molding the prepared slurry on a PET film.

  In this step, the profile of the primary particles constituting the aligned positive electrode plate 12 can be controlled as described below.

  First, by adjusting the molding speed, the total area ratio of low-angle primary particles having an orientation angle of more than 0 ° and not more than 30 ° can be controlled. Specifically, the higher the molding speed, the higher the total area ratio of the low-angle primary particles.

  Moreover, the average particle diameter of a primary particle can be controlled by adjusting the density of a molded object. Specifically, the average particle diameter of the primary particles can be increased as the density of the molded body is increased.

The density of the aligned positive electrode plate 12 can also be controlled by adjusting the mixing ratio between the LiCoO ₂ template particles and the matrix particles. Specifically, the smaller the amount of LiCoO ₂ template particles, the higher the density of the aligned positive electrode plate 12 can be lowered.

4). Preparation of Oriented Sintered Plate A molded product of slurry is placed on a zirconia setter and subjected to heat treatment (500 ° C. to 900 ° C., 1 to 10 hours) to obtain a sintered plate as an intermediate.

  Next, the sintered plate is sandwiched between lithium sheets so that the Li / Co ratio is 1.0, and the synthesized lithium sheet is placed on a zirconia setter.

Next, after putting a setter into an alumina sheath and firing in the atmosphere (700 to 850 ° C., 1 to 20 hours), the sintered plate is sandwiched between lithium sheets and further fired (750 to 900 ° C., 1 to 40). Time) to obtain a LiCoO ₂ sintered plate. This firing step may be performed in two steps or may be performed once. When firing twice, it is preferable that the first firing temperature is lower than the second firing temperature. In this step, the profile of the primary particles constituting the aligned positive electrode plate 12 is controlled as follows. Can do.

  First, the total area ratio of the low-angle primary particles whose orientation angle is more than 0 ° and not more than 30 ° can be controlled by adjusting the temperature rising rate during firing. Specifically, the higher the temperature increase rate, the more the sintering of the matrix particles is suppressed, and the total area ratio of the low-angle primary particles can be increased.

  In addition, the total area ratio of the low-angle primary particles whose orientation angle is greater than 0 ° and 30 ° or less can also be controlled by adjusting the heat treatment temperature of the intermediate. Specifically, the lower the heat treatment temperature of the intermediate, the more the sintering of the matrix particles is suppressed, and the total area ratio of the low-angle primary particles can be increased.

  Moreover, the average particle diameter of the primary particles can be controlled by adjusting at least one of the temperature increase rate during firing and the heat treatment temperature of the intermediate. Specifically, the average particle diameter of the primary particles can be increased as the rate of temperature increase is increased and the heat treatment temperature of the intermediate is decreased.

Also, the average particle size of the primary particles can be controlled by adjusting at least one of the amount of Li (for example, Li ₂ CO ₃ ) and the amount of sintering aid (for example, boric acid or bismuth oxide) during firing. Can do. Specifically, the average particle size of the primary particles can be increased as the amount of Li is increased and the amount of the sintering aid is increased.

Moreover, the density of the alignment positive electrode plate 12 can be controlled by adjusting the amount of Li (for example, Li ₂ CO ₃ ) during firing. Specifically, the denseness of the aligned positive electrode plate 12 can be increased as the amount of Li is increased.

  Further, the density of the aligned positive electrode plate 12 can be controlled by adjusting the profile during firing. Specifically, the density of the aligned positive electrode plate 12 can be increased as the firing temperature is lowered and the firing time is lengthened.

(Manufacturing method of all-solid-state lithium battery 10)
First, LiOH raw material powder and _Li 2 SO ₄ raw material powder and a volume ratio of 3: The mixed mixture 1, heat treatment in an Ar atmosphere (400 to 450 ° C., 0.1 to 1 h) was melted in to it The solid is obtained by quenching the melt. This solidified product is a solid electrolyte member containing a solid electrolyte represented by a composition formula 3LiOH · Li ₂ SO ₄ .

  Next, the obtained solid electrolyte is placed on the positive electrode plate 12 (or the negative electrode plate 16).

  Next, after placing the negative electrode plate 14 (or the positive electrode plate 12) on the solid electrolyte, the negative electrode plate 14 (or the positive electrode plate 12) is pressed toward the positive electrode plate 12 (or the negative electrode plate 16).

  Thus, the all solid lithium battery 10 is formed.

The present invention is more specifically described by the following examples. In the following example, LiCoO ₂ is abbreviated as “LCO”, and Li ₄ Ti ₅ O ₁₂ is abbreviated as “LTO”.

(Preparation of Examples 1-4 and Comparative Examples 1-2)
(1) Production of positive electrode plate

(1a) Preparation of LCO Green Sheet Co ₃ O ₄ powder (manufactured by Shodo Chemical Co., Ltd., average particle size 0.9 μm) and Li ₂ CO weighed so that the molar ratio of Li / Co is 1.02. After mixing ₃ powders (Honjo Chemical Co., Ltd.), the mixture was held at 750 ° C. for 5 hours. The obtained powder was pulverized by a pot mill so that the volume standard D50 was 0.4 μm to obtain a powder composed of LCO plate-like particles. 100 parts by weight of the obtained LCO powder, 100 parts by weight of a dispersion medium (toluene: isopropanol = 1: 1), 10 parts by weight of a binder (polyvinyl butyral: product number BM-2, manufactured by Sekisui Chemical Co., Ltd.), and a plasticizer 4 parts by weight (DOP: Di (2-ethylhexyl) phthalate, manufactured by Kurokin Kasei Co., Ltd.) and 2 parts by weight of a dispersant (product name: Rheodor SP-O30, manufactured by Kao Corporation) were mixed. The obtained mixture was stirred and degassed under reduced pressure, and an LCO slurry was prepared by adjusting the viscosity to 4000 cP. The viscosity was measured with an LVT viscometer manufactured by Brookfield. An LCO green sheet in which the average orientation angle of primary particles is adjusted to 3 ° to 20 ° as shown in Table 1 by forming the slurry thus prepared into a sheet on a PET film by a doctor blade method. Formed. The thickness of the LCO green sheet was set to a value such that the thickness after firing was 50 μm.

(1b) Production of Li ₂ CO ₃ green sheet (excess lithium source) Li ₂ CO ₃ raw material powder (volume basis D50 particle size 2.5 μm, manufactured by Honjo Chemical Co., Ltd.) 100 parts by weight and binder (polyvinyl butyral: product number BM) -2, 5 parts by weight of Sekisui Chemical Co., Ltd., 2 parts by weight of plasticizer (DOP: di (2-ethylhexyl) phthalate, Kurokin Kasei Co., Ltd.) and dispersant (Rheodor SP-O30, Kao) 2 parts by weight) were mixed. The resulting mixture was stirred and degassed under reduced pressure, and the viscosity was adjusted to 4000 cP to prepare a Li ₂ CO ₃ slurry. The viscosity was measured with an LVT viscometer manufactured by Brookfield. A Li ₂ CO ₃ green sheet was formed by forming the Li ₂ CO ₃ slurry thus prepared into a sheet on a PET film.

(1c) Production of LCO sintered plate (positive electrode plate) The LCO green sheet peeled off from the PET film was cut into a 50 mm square with a cutter and placed in the center of a magnesia setter (dimension 90 mm square, height 1 mm) as a lower setter. did. The LCO green sheet was heated to 600 ° C. at a temperature rising rate of 200 ° C./h, degreased for 3 hours, and then calcined by holding at 900 ° C. for 3 hours. To Co content in the resultant LCO calcined plate, the molar ratio of Li content in _Li 2 CO ₃ green sheet, sized to Li / Co ratio is 0.5, dried _Li 2 CO _Three green sheets were cut out. On the LCO calcined plate, the cut out Li ₂ CO ₃ green sheet piece was placed as an excess lithium source, and a porous magnesia setter as an upper setter was placed thereon. The sintered plate and the green sheet piece were placed in a 120 mm square alumina sheath (Nikkato Co., Ltd.) with the setter sandwiched between them. At this time, the alumina sheath was not sealed, and a gap of 0.5 mm was left to cover. The obtained laminate was heated to 600 ° C. at a temperature rising rate of 200 ° C./h and degreased for 3 hours, then heated to 800 ° C. at 200 ° C./h and held for 5 hours, and then from 800 ° C. to 900 ° C. Firing was performed by raising the temperature at 200 ° C./h and holding for 24 hours. At this time, the porosity in each LCO sintered body plate (positive electrode plate) of each of Examples 1 to 4 and Comparative Example 2 was changed as shown in Table 1 by changing the firing temperature.

  After firing, the temperature was lowered to room temperature, and then the fired body was taken out from the alumina sheath. Thus, an LCO sintered plate was obtained as a positive electrode plate. An Au film (thickness: 100 nm) was formed as a current collecting layer by sputtering on the surface of the obtained LCO sintered body plate that was in contact with the lower setter, and then laser processed into a 10 mm × 10 mm square shape.

(2) Production of negative electrode plate (2a) Production of LTO green sheet LTO powder (volume basis D50 particle size 0.06 μm, Sigma-Aldrich Japan GK) 100 parts by weight and dispersion medium (toluene: isopropanol = 1: 1) 100 parts by weight, 20 parts by weight of a binder (polyvinyl butyral: product number BM-2, manufactured by Sekisui Chemical Co., Ltd.) and 4 parts by weight of a plasticizer (DOP: Di (2-ethylhexyl) phthalate, manufactured by Kurokin Kasei Co., Ltd.) And 2 parts by weight of a dispersant (product name Leodol SP-O30, manufactured by Kao Corporation) were mixed. The obtained negative electrode raw material mixture was stirred and degassed under reduced pressure, and an LTO slurry was prepared by adjusting the viscosity to 4000 cP. The viscosity was measured with an LVT viscometer manufactured by Brookfield. The slurry thus prepared was formed into a sheet on a PET film by a doctor blade method to form an LTO green sheet. The thickness of the LTO green sheet after drying was set to such a value that the thickness after firing was 50 μm.

(2b) Firing of LTO green sheet The obtained green sheet was cut into a 25 mm square with a cutter knife, embossed and placed on a zirconia setter. The green sheet on the setter was put in an alumina sheath and held at 500 ° C. for 5 hours, and then heated at a temperature rising rate of 200 ° C./h and baked at 800 ° C. for 5 hours. An Au film (thickness: 100 nm) was formed as a current collecting layer by sputtering on the surface of the obtained LTO sintered body plate that was in contact with the setter, and then laser processed into a 10 mm × 10 mm square shape.

(3) Preparation of the solid electrolyte member First, a _Li 2 SO ₄ raw material powder and LiOH raw material powder, a volume ratio of 3: 1 mixture.

  Next, the mixture was put in a glass tube in an Ar atmosphere and melted by heating at 430 ° C. for 2 hours. Then, the glass tube was put into water and held for 10 minutes, whereby the melt was rapidly cooled to form a solidified body.

  Next, a 10 mm × 10 mm square solidified body was cut out in an Ar atmosphere.

(4) Battery preparation The solidified body cut out on the positive electrode plate was placed, and the negative electrode plate was placed while pressing from above. At this time, the solidified body was compressed, and finally a solid electrolyte layer having a thickness of 20 μm was formed. 100 laminated batteries were produced using the obtained positive electrode plate / solid electrolyte / negative electrode plate cell.

(5) Evaluation Regarding the LCO positive electrode plate synthesized in the above (1), the LTO negative electrode plate synthesized in the above (2), and the battery produced in the above (4), various evaluations were performed as shown below. It was.

(Production of Comparative Example 1)
In Comparative Example 1, a battery was fabricated in the same process as Examples 1 to 4 and Comparative Reason 2 except that a non-oriented LCO sintered plate (positive electrode plate) was used. The non-oriented LCO sintered plate used in Comparative Example 1 was obtained by heating a green sheet produced using a commercially available LCO powder to 600 ° C. at a temperature rising rate of 200 ° C./h and degreasing for 3 hours. The temperature was raised to 200 ° C./h up to 200 ° C. and kept for 24 hours to perform firing.

<Porosity>
Each of the LCO positive electrode plate and the LTO negative electrode plate is polished with a cross section polisher (CP) (IB-15000CP, manufactured by JEOL Ltd.), and the obtained electrode plate cross section is observed by SEM with a 1000 × field of view (125 μm × 125 μm). (JSM 6390LA, manufactured by JEOL Ltd.) After image analysis, the area of all voids was divided by the area of each plate, and the resulting value was multiplied by 100 to calculate the porosity (%) of each electrode plate did.

<Average orientation angle of primary particles>
The LCO positive electrode plate was polished with a cross section polisher (CP) (IB-15000CP, manufactured by JEOL Ltd.), and the resulting positive electrode plate cross section (cross section perpendicular to the plate surface of the positive electrode plate) was viewed 1000 times (125 μm × EBSD measurement was performed at 125 μm to obtain an EBSD image. This EBSD measurement was performed using a Schottky field emission scanning electron microscope (manufactured by JEOL Ltd., model JSM-7800F). For all the particles specified in the obtained EBSD image, the angle formed by the (003) plane of the primary particle and the plate surface of the positive electrode plate (that is, the inclination of the crystal orientation from (003)) is determined as the inclination angle, The average value of the angles was defined as the average orientation angle (average tilt angle) of the primary particles.

<Evaluation of charge / discharge availability>
At an operating temperature of 150 ° C., constant current charging is performed until the battery voltage reaches 2.7 V at a 0.2 C rate, and constant voltage charging is performed until the current value reaches a 0.02 C rate, and then 1.5 V at a 0.2 C rate. It was determined whether or not charging / discharging was possible by discharging until.

As shown in Table 1, the positive electrode plate having a porosity of 0% or more and 10% or less and an average orientation angle of primary particles of more than 0 ° and 30 ° or less, and a composition formula 3LiOH · Li ₂ SO ₄ It was confirmed that the charge / discharge performance in the all-solid lithium battery can be remarkably improved by using the solid electrolyte member containing the solid electrolyte.

DESCRIPTION OF SYMBOLS 10 All-solid-state lithium battery 11 Primary particle 12 Positive electrode plate 13 Positive electrode collector 14 Solid electrolyte member 16 Negative electrode plate 17 Negative electrode collector 18 Container

Claims (4)

An oriented positive electrode plate which is a lithium composite oxide sintered body plate having a porosity of 0% or more and 10% or less, wherein the lithium composite oxide sintered plate is a plurality of primary particles composed of a lithium composite oxide An oriented positive electrode plate, wherein the plurality of primary particles are oriented at an average orientation angle of more than 0 ° and not more than 30 ° with respect to the plate surface of the oriented positive electrode plate;
A negative electrode plate containing Ti and capable of inserting and extracting lithium ions at 0.4 V (vs. Li / Li ⁺ ) or higher;
A solid electrolyte member including a solid electrolyte represented by a composition formula 3 LiOH · Li ₂ SO ₄ ;
Comprising
All solid lithium battery. The lithium composite oxide is lithium cobalt oxide;
The all solid lithium battery according to claim 1. It is charged and discharged at a temperature of 100 ° C or higher,
The all-solid-state lithium battery of Claim 1 or 2. It is a manufacturing method of the all-solid-state lithium battery as described in any one of Claims 1-3,
Placing a solid electrolyte member containing a solid electrolyte represented by a composition formula 3LiOH · Li ₂ SO ₄ on the positive electrode plate or the negative electrode plate;
Placing the negative electrode plate or the positive electrode plate on the solid electrolyte; and
Pressing the negative electrode plate toward the positive electrode plate or the positive electrode plate toward the negative electrode plate;
including,
A method for producing an all-solid-state lithium battery.

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