Battery

Abstract

The present invention improves charging / discharging characteristics. A battery, according to the present invention, has a positive electrode and a negative electrode. The positive electrode has: a positive electrode active material layer that has a first main surface and a second main surface on the reverse side from the first main surface; a positive electrode coating layer that is on the first main surface side of the positive electrode active material layer and has electronic insulating properties; and a positive electrode current collector on the second main surface side of the positive electrode active material layer. The positive electrode active material layer is a continuous body in which a positive electrode active material having a layered rock-salt structure is continuously formed from the first main surface to the second main surface. The first main surface has, among crystal planes of the layered rock-salt structure, a crystal plane that intersects a {001} plane. The ratio of the length of the crystal plane that intersects the {001} plane, the length present in a cross section along the thickness direction of the positive electrode active material layer as measured by a transmission electron microscope, to the surface length of the first main surface is greater than 0.28.

Description

battery

[0001] This invention relates to a battery.

[0002] Patent Document 1 discloses a battery that uses a positive electrode made of a polycrystalline material oriented to a specific crystal orientation and a solid electrolyte made of ceramics.

[0003] International Publication No. 2015 / 151566

[0004] In the battery described in Patent Document 1, the movement of carrier ions may be inhibited at the junction interface between the solid electrolyte and the positive electrode active material, potentially leading to a decrease in charge-discharge characteristics.

[0005] The present invention aims to provide a battery that can improve charge and discharge characteristics.

[0006] A battery according to one aspect of the present invention has a positive electrode and a negative electrode, the positive electrode having a positive electrode active material layer having a first main surface and a second main surface opposite to the first main surface, a positive electrode coating layer having electronic insulating properties located on the first main surface side of the positive electrode active material layer, and a positive electrode current collector located on the second main surface side of the positive electrode active material layer, the positive electrode active material layer being a continuum in which a positive electrode active material having a layered rock salt type structure is continuously formed from the first main surface to the second main surface, the first main surface having a crystal plane that intersects with the {001} plane among the crystal planes of the layered rock salt type structure, and the ratio of the length of the crystal plane intersecting with the {001} plane to the length of the surface of the first main surface, as seen in a cross-section along the thickness direction of the positive electrode active material layer measured by a transmission electron microscope, is greater than 0.28.

[0007] The battery of the present invention can improve charge and discharge characteristics.

[0008] Figure 1 is a schematic cross-sectional view showing a battery according to an embodiment. Figure 2 is an explanatory diagram illustrating a measurement method related to the positive electrode active material layer.

[0009] Embodiments of the battery of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Each embodiment is illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible.

[0010] (Embodiment) Figure 1 is a schematic cross-sectional view showing a battery according to the embodiment. The battery 10 according to the embodiment is an all-solid-state battery that can be repeatedly charged and discharged, and more specifically, a lithium-ion secondary all-solid-state battery. As shown in Figure 1, the battery 10 has a positive electrode 20, a negative electrode 30, and a solid electrolyte layer 40. The positive electrode 20 and the negative electrode 30 are stacked with the solid electrolyte layer 40 in between.

[0011] The positive electrode 20 includes a positive electrode current collector 21, a positive electrode active material layer 22, and a positive electrode coating layer 23. In the positive electrode 20, the positive electrode current collector 21, the positive electrode active material layer 22, and the positive electrode coating layer 23 are stacked in that order. In the following description, the direction in which the positive electrode current collector 21, the positive electrode active material layer 22, and the positive electrode coating layer 23 are stacked is described as the Z direction, and one of the directions perpendicular to the Z direction is described as the X direction. In the embodiment, the Z direction is an example of the thickness direction of the positive electrode active material layer 22 according to the present disclosure. Also, in the embodiment, the X direction is an example of the direction along the main surface of the positive electrode current collector 21 on the positive electrode active material layer 22 side according to the present disclosure.

[0012] The positive electrode current collector 21 is a conductive layer, which is, for example, a metal. Specifically, aluminum foil or the like can be used as the material for the positive electrode current collector 21.

[0013] The positive electrode active material layer 22 is a layer containing positive electrode active material. The positive electrode active material layer 22 has a first main surface S1 and a second main surface S2 opposite to the first main surface S1. In this embodiment, the second main surface S2 of the positive electrode active material layer 22 is in contact with the positive electrode current collector 21, and the first main surface S1 of the positive electrode active material layer 22 is covered with a positive electrode coating layer 23.

[0014] The positive electrode active material layer 22 is preferably a continuum in which the positive electrode active material is continuously formed from the first main surface S1 to the second main surface S2. In this embodiment, the positive electrode active material layer 22 is a layer in which the positive electrode active material is uniformly deposited, and does not contain any substances other than the positive electrode active material, such as binders and conductive additives, and does not contain substantially any voids. As a result, there is a larger amount of positive electrode active material that can intercept and deintercept carrier ions, and thus the battery capacity can be improved.

[0015] Here, whether or not the positive electrode active material layer 22 is a continuum in which the positive electrode active material is continuously formed from the first main surface S1 to the second main surface S2 can be determined by the following method. First, the positive electrode active material layer 22 is cut in the thickness direction and observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to obtain an observation image. Then, when a line is drawn in the direction parallel to the thickness direction in the observation image, if the total width of the region in the thickness direction of the positive electrode active material layer 22 that passes only through the positive electrode active material from the first main surface S1 to the second main surface S2 is 50% or more of the width of the cross-section of the positive electrode active material layer 22 (thickness of the positive electrode active material layer 22) in at least one of the observation images, then the positive electrode active material layer 22 can be said to be a continuum in which the positive electrode active material is continuously formed from the first main surface S1 to the second main surface S2.

[0016] The positive electrode active material layer 22 contains a positive electrode active material having a layered rock salt type structure. The positive electrode active material is preferably a lithium-containing compound such as a lithium-containing composite oxide or a lithium-containing phosphate compound. Here, the lithium-containing composite oxide is an oxide containing lithium and one or more elements other than lithium as constituent elements. An example of a lithium-containing compound having a layered rock salt type structure is LiCoO2. ２ LiNiO ２ LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ These are some examples.

[0017] Here, whether or not the positive electrode active material layer 22 contains positive electrode active material having a layered rock salt type structure can be determined by crystal structure analysis of the positive electrode active material. More specifically, the crystal structure of the positive electrode active material layer can be examined using TEM, X-ray diffraction (XRD), etc. If the crystal space group is assigned to R-3m, then it can be said that the positive electrode active material has a layered rock salt type structure.

[0018] The positive electrode coating layer 23 is provided on the first main surface S1 of the positive electrode active material layer 22. That is, the positive electrode coating layer 23 is provided between the first main surface S1 of the positive electrode active material layer 22 and the solid electrolyte layer 40. Here, the positive electrode coating layer 23 substantially does not contain a positive electrode active material. By providing the positive electrode coating layer 23, direct contact between the positive electrode active material layer 22 and the solid electrolyte layer 40 is suppressed, and reaction between the positive electrode active material layer 22 and the solid electrolyte layer 40 can be suppressed, so that charge-discharge characteristics can be improved.

[0019] The positive electrode coating layer 23 has electron insulation. In the present disclosure, having electron insulation means being made of a material having an electrical resistivity of 10 ４ Ω·m or more. The positive electrode coating layer 23 preferably contains a compound containing lithium (Li), element A, and element X, and more preferably contains a compound represented by the general formula Li-A-X. Here, element A is at least one of B, Al, Si, P, Ti, Ge, Zr, Nb, In, Sn, Hf, Ta, and W. Element X is at least one of O, S, N, F, Cl, Br, and I. The positive electrode coating layer 23 more preferably contains a compound containing Li and at least one of Nb, P, and In and at least one of O, Cl, and N. That is, element A is more preferably at least one of Nb, P, and In, and element X is more preferably at least one of O, S, N, F, Cl, and Br. The positive electrode coating layer 23 includes, for example, lithium niobate (LiNbO ３ ), lithium phosphate (Li ３ PO ４ ), lithium indium chloride (Li ３ InCl ６ ), and the like. Thereby, the positive electrode coating layer 23 can be suppressed from undergoing a redox reaction, and the reaction between the positive electrode 20 and the solid electrolyte layer 40 can be suppressed, so that charge-discharge characteristics can be improved.

[0020] The thickness of the positive electrode coating layer 23 is preferably 5 nm or more, more preferably 20 nm or more. Also, the thickness of the positive electrode coating layer 23 is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 1 μm or less, and most preferably 450 nm or less. Thereby, the interfacial resistance between the positive electrode active material layer 22 of the positive electrode 20 and the solid electrolyte layer 40 is suppressed. Note that, for the thickness of the positive electrode coating layer 23, the average thickness of the positive electrode coating layer 23 measured by SEM or TEM with respect to a cross-section along the thickness direction (Z direction) of the positive electrode 20 can be adopted.

[0021] The negative electrode 30 includes a negative electrode current collector 31 and a negative electrode active material layer 32. In the negative electrode 30, the negative electrode active material layer 32 is laminated on one surface of the negative electrode current collector 31. In a direction perpendicular to one surface of the negative electrode current collector 31, the negative electrode active material layer 32 is provided between the negative electrode current collector 31 and the solid electrolyte layer 40.

[0022] The negative electrode current collector 31 is a conductor, and for example, a copper foil or the like can be used.

[0023] The negative electrode active material layer 32 is a layer containing a negative electrode active material. The negative electrode active material includes materials capable of storing and releasing lithium, such as, for example, carbon materials, metals, semimetals, alloys or compounds of silicon, and alloys or compounds of tin (Sn).

[0024] Examples of the carbon material that can be used as the negative electrode active material include graphite, non-graphitizable carbon, graphitizable carbon, and the like. More specifically, the carbon material includes, for example, pyrolytic carbons, cokes, vitreous carbon fibers, fired bodies of organic high molecular compounds, activated carbons, carbon blacks, and the like. Cokes include pitch coke, needle coke, petroleum coke, and the like. Here, the fired body of the organic high molecular compound is obtained by firing a high molecular compound such as a phenol resin or a furan resin at an appropriate temperature and carbonizing it.

[0025] Metals and semimetals that can be used as the negative electrode active material include, for example, tin, lead (Pb), aluminum, indium (In), silicon, zinc (Zn), antimony (Sb), bismuth (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y), and hafnium (Hf). Among them, silicon, germanium, tin, and lead are preferable. Further, silicon and tin are more preferable because they have a large ability to occlude and release lithium and can obtain a high energy density.

[0026] Examples of the silicon alloy that can be used as the negative electrode active material include those containing at least one kind selected from the group consisting of tin, nickel, copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc, indium, silver, titanium (Ti), germanium, bismuth, antimony, and chromium as the second constituent element other than silicon. Examples of the silicon compound that can be used as the negative electrode active material include those containing oxygen (O) or carbon (C), and may contain the above-described second constituent element in addition to silicon.

[0027] Examples of the tin alloy that can be used as the negative electrode active material include those containing at least one kind selected from the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as the second constituent element other than tin. Examples of the tin compound that can be used as the negative electrode active material include those containing oxygen or carbon, and may contain the above-described second constituent element in addition to tin.

[0028] Note that the negative electrode active material layer 32 is not limited to only the negative electrode active material, and may contain, for example, a conductive assistant and a binder.

[0029] The solid electrolyte layer 40 is provided between the positive electrode 20 and the negative electrode 30. The solid electrolyte layer 40 contains a solid electrolyte and contains a material different from that of the positive electrode coating layer 23. Here, the solid electrolyte layer substantially does not contain the negative electrode active material. The solid electrolyte layer 40 is electrically conductive. Here, being electrically conductive means that its electrical resistivity is 10 4 This refers to a value greater than Ω·m. The solid electrolyte is not particularly limited as long as it is a material that allows ions to move between the positive electrode 20 and the negative electrode 30. For example, lithium compounds that are at least one of a composite oxide, oxide, nitride, sulfide, sulfate, phosphate, carbonate, borate, and conductive polymer containing at least one of Si, Ti, Sn, and Al, or compounds containing S (sulfur), can be used. Specifically, TiO ２ Li ６ PS ５ Cl, Li ３ PS ４ Li ４ SnS ４ The following can be used. The solid electrolyte layer 40, formed from a compound containing sulfur, has excellent thermoformability and can form a good bonding interface with the positive electrode active material layer 22. The solid electrolyte layer may be a laminate containing multiple layers made of different materials. Furthermore, the solid electrolyte layer is not an essential component and may not be provided. Even in this case, the positive electrode coating layer functions as a solid electrolyte, allowing carrier ions to move while maintaining insulation between the positive and negative electrodes.

[0030] Next, the detailed configuration of the first main surface of the positive electrode active material layer 22 will be described. Figure 2 is an explanatory diagram for illustrating the measurement method related to the positive electrode active material layer. Figure 2 shows an observation image IM of the cross-section of the positive electrode active material layer 22 including the first main surface S1.

[0031] In the example shown in Figure 2, the positive electrode active material layer 22 consists of a positive electrode active material with a layered rock salt structure. Furthermore, the microscopic surface shape of the first main surface S1 is uneven. Therefore, in the cross-sectional view shown in Figure 2, the surface of the first main surface has a bent shape formed by the combination of lines of multiple types of crystal planes. Consequently, multiple types of crystal planes of the layered rock salt structure, such as the {001} plane (plane S11) and the {116} plane (plane S12), are visible on the first main surface S1. In the following explanation, the ratio of the length of the crystal planes to the length of the surface of the first main surface S1, as seen in the cross-section along the thickness direction of the positive electrode active material layer 22, may be simply described as the ratio of the length of the crystal planes on the first main surface S1.

[0032] (Crystal planes of the first principal surface) The first principal surface S1 has crystal planes that intersect with the {001} plane among the crystal planes of the layered rock salt type structure. That is, the first principal surface S1 has crystal planes other than the {001} plane among the crystal planes of the layered rock salt type structure. In other words, the first principal surface S1 has crystal planes that intersect with the crystal orientation <110> direction among the crystal planes of the layered rock salt type structure. As a result, the cross section of the ion insertion and deinsertion surface of the positive electrode active material crystal is exposed on the first principal surface S1, thereby improving the charge and discharge characteristics.

[0033] The ratio of the length of the crystal planes intersecting the {001} plane on the first main surface S1 is preferably 0.55 or more, and more preferably 0.79 or more and 0.90 or less. This ensures that the cross-sectional area of ​​the ion insertion and deinsertion surface of the positive electrode active material crystal exposed on the first main surface S1 is sufficient, thereby further improving the charge and discharge characteristics.

[0034] Preferably, the first main surface S1 has at least one of the {116}, {012}, and {104} planes of a layered rock salt type structure, and more preferably, a {116} plane of a layered rock salt type structure. This makes it possible to give the surface of the positive electrode active material on the first main surface S1 a chemically stable crystalline structure, suppressing side reactions associated with the charge-discharge reaction, and thus improving the charge-discharge characteristics.

[0035] The ratio of the length of the {116} plane of the layered rock salt structure on the first main surface S1 is preferably greater than 0.05, and more preferably 0.35 or greater. This improves the charge-discharge characteristics.

[0036] (Method for measuring crystal planes on the first main surface) The ratio of crystal plane lengths on the first main surface S1 is measured by TEM on a cross-section along the thickness direction (Z direction) of the positive electrode active material layer 22. The method for measuring the ratio of crystal plane lengths on the first main surface S1 is described in detail below.

[0037] First, the battery 10 is viewed from the Z direction in a plan view and cut into a rectangle with sides of approximately 1 cm. Next, it is washed in a washing solvent (e.g., dimethyl carbonate) by stirring for 1 minute, and dried at room temperature for 1 hour to evaporate the washing solvent. Then, an argon ion beam is irradiated in a direction perpendicular to the Z direction to flatten the cross-section of the positive electrode 20 by ion milling. For example, an IM4000 (Hitachi High-Tech) ion milling apparatus can be used. Then, the area near the first main surface S1 of the positive electrode current collector is thinned using focused beam processing to obtain an observation sample. For example, a JIB-4700F (JEOL) focused beam processing apparatus can be used.

[0038] Next, the cross-section of the fabricated test specimen is observed using a TEM. TEM observation can be performed under the following conditions, for example. Here, the observation image is acquired such that the positive electrode active material layer 22 accounts for 50% or more of the area. Three observation images are acquired. The observation magnification is merely an example, and it is preferable to make it as large as possible. TEM: JEM-ARM200F (manufactured by JEOL) Acceleration voltage: 200kV Observation magnification: 500,000x to 1,000,000x

[0039] The ratio of the length of the crystal planes on the first principal surface S1 is calculated as follows. First, from multiple observation images obtained by TEM, a square area containing the first principal surface S1 and with sides of approximately 100 nm is extracted, as shown in Figure 2. Then, the crystal planes on the surface of the first principal surface S1 are identified for each direction of extension of the surface of the first principal surface S1, and the length of the surface containing the crystal plane to be measured is calculated. Specifically, as shown in Figure 2, the crystal planes on the surface of the first principal surface S1 are identified using the fringes that extend in the crystal orientation <110> direction of the layered rock salt type structure that appear in the TEM observation image of the cross section of the positive electrode active material layer 22. In the example in Figure 2, plane S11 extends in a direction parallel to the extension direction of the fringes along the crystal orientation <110>, so it can be identified as the {001} plane. Furthermore, since plane S12 extends in a direction intersecting the direction of extension of the fringes along the crystal orientation <110>, it can be identified as a crystal plane intersecting the {001} plane, and from the angle between the direction of extension of plane S12 and the direction of extension of the fringes along the crystal orientation <110>, it can be identified as the {116} plane. Next, the length of the surface of the first principal plane S1 in the extracted area is calculated. Then, the ratio of the length of the crystal plane to be measured to the calculated surface length of the first principal plane S1 is averaged across the three observation images to calculate the ratio of the length of the crystal plane on the first principal plane S1.

[0040] (Length ratio L / Lp) The ratio L / Lp of the length L of the surface of the first main surface S1, which appears in a cross-section along the thickness direction of the positive electrode active material layer 22, to the length Lp of the positive electrode active material layer 22 in the direction along the surface of the positive electrode current collector 21 (X direction), is preferably 1.14 or more. This increases the surface area of ​​the first main surface S1, and the anchoring effect caused by the increased unevenness of the first main surface S1 firmly bonds the positive electrode 20 and the solid electrolyte layer 40, thereby suppressing interfacial resistance and further improving charge-discharge characteristics. In the following description, the ratio L / Lp of length L to length Lp may be simply referred to as the length ratio L / Lp.

[0041] (Method for measuring the length ratio L / Lp) The length ratio L / Lp is measured by SEM on a cross-section along the thickness direction (Z direction) of the positive electrode active material layer 22. The method for measuring the length ratio L / Lp is described in detail below.

[0042] First, the battery 10 is cut into a rectangle with sides of approximately 1 cm when viewed from above in the Z direction. Next, it is washed for 1 minute by stirring in a washing solvent (e.g., dimethyl carbonate), and dried at room temperature for 1 hour to evaporate the washing solvent. Then, an argon ion beam is irradiated in a direction perpendicular to the Z direction to flatten the cross-section of the positive electrode 20 by ion milling. For example, an IM4000 (Hitachi High-Tech) can be used as the ion milling apparatus.

[0043] Next, the cross-section of the fabricated test specimen is observed using a scanning electron microscope (SEM). SEM observation can be performed under the following conditions, for example: Here, the observed image is acquired such that the positive electrode active material layer 22 accounts for 50% or more of the area, the positive electrode active material layer 22 is contained within the image across the thickness direction (Z direction), and the lateral direction of the observed image is parallel to the direction (X direction) along the main surface of the positive electrode current collector 21 on the positive electrode active material layer 22 side. Five observation images are acquired. The observation magnification is merely an example; it is preferable to make it as large as possible. SEM: S-4800 (Hitachi High-Tech) Acceleration voltage: 3kV Magnification: 1000x-5000x

[0044] The length ratio L / Lp is calculated as follows. First, from multiple observation images obtained by SEM, a square area containing the first principal surface S1 and with sides of approximately 100 nm is extracted, as shown in Figure 2. Here, the length in the lateral direction (X direction) of the extracted area is defined as Lp. Next, the surface length of the first principal surface S1 is calculated within the extracted area to obtain the surface length L of the first principal surface S1. By averaging the length ratio L / Lp for each SEM observation image across five observation images, the length ratio L / Lp of the sample to be measured can be calculated.

[0045] The positive electrode according to this embodiment can be manufactured, for example, using the flux method. The method for manufacturing a positive electrode using the flux method includes a step of forming a mixed material layer, a heat treatment step, a cleaning step, and a step of forming a positive electrode coating layer.

[0046] In the step of forming the mixed material layer, the positive electrode active material and flux are dissolved in water and dropped onto the positive electrode current collector to form the mixed material layer. In the heat treatment step, the positive electrode current collector with the mixed material layer formed on it is heat-treated in an electric furnace in a dry air atmosphere to obtain a positive electrode current collector with the positive electrode active material deposited on it. Here, by adjusting the heat treatment conditions such as the heating temperature, heating rate, and cooling rate, the crystal planes and length ratio L / Lp appearing on the first main surface can be made suitable. In the washing step, the positive electrode current collector with the positive electrode active material deposited on it is washed with a polar solvent to remove flux components and residues, and then dried under vacuum to obtain a positive electrode current collector with the positive electrode active material layer formed on it. In the step of forming the positive electrode coating layer, for example, Li-Nb oxide is deposited on the surface of the positive electrode layer by sputtering to obtain the positive electrode according to this embodiment. Furthermore, the method for forming the positive electrode active material layer is not limited to the flux method described above. The positive electrode active material layer may also be formed using methods such as molten salt crystallization, laser thin film deposition, sputtering thin film deposition, chemical vapor deposition, organometallic decomposition, electrochemical methods, solvothermal synthesis, and soft chemical synthesis.

[0047] (Example 1) The following describes an example. However, the present invention is not limited by this example.

[0048] The positive electrode for Example 1 was prepared by the following method. In the step of forming the mixed material layer, a mixture of lithium nitrate and cobalt nitrate as the positive electrode active material and lithium chloride and potassium chloride as the flux in a molar ratio of 60:40 was dissolved in water and dropped onto an aluminum plate to form a mixed material layer with a thickness of approximately 20 μm. In the heat treatment step, the positive electrode current collector with the mixed material layer formed was heated in an electric furnace at 600°C in a dry air atmosphere to form the positive electrode active material LiCoO ２ A positive electrode current collector was obtained with LiCoO deposited. In the cleaning process, LiCoO ２The aluminum plate on which the precipitate had formed was washed with a polar solvent to remove flux components and residue, and dried under vacuum at 120°C for 8 hours to obtain a positive electrode current collector with a positive electrode active material layer formed on it. In the process of forming the positive electrode coating layer, a 20 nm thick Li-Nb oxide film was deposited on the surface of the positive electrode active material layer by sputtering under the following conditions to obtain the positive electrode according to this embodiment. Sputtering apparatus: RF sputtering apparatus (manufactured by ULVAC) Target material: LiNbO ３ Sputtering temperature: Room temperature Power output: 600W Gas atmosphere: Ar (gas flow rate 30 mL / m), O ２ (Gas flow rate: 30 mL / m) Film deposition pressure: 0.4 Pa

[0049] The battery according to Example 1 was prepared by the following method: 100 mg of Li was placed in a zirconia cylinder with a diameter of 10 mm. ６ PS ５ Add Cl powder (manufactured by NEI Corporation) to 1 tf / cm² ２ The material was compressed into pellets at min (minute) to create a solid electrolyte layer. Then, the positive electrode prepared above was placed in a cylinder at 1 tf / cm². ２ - min) to 3 tf / (cm ２ The pressure was increased to min) and compacted. Then, on the opposite side of the positive electrode of the solid electrolyte layer, an indium foil with a diameter of 10 mm and a thickness of 0.25 mm and a metallic lithium foil with a diameter of 8 mm and a thickness of 0.2 mm were stacked in order as the negative electrode, and the pressure was increased to 0.5 tf / cm. ２ A battery for evaluation was fabricated by fixing it inside the cylinder at min (min).

[0050] <Charge and Discharge Test> As a charge and discharge test, the battery unit according to Example 1 was set in a charge and discharge test machine (Toyo System, TOSCAT3100) and the initial charge and discharge was performed under the following conditions: Charging method: CCCV Charging rate: 0.05C Charging control voltage: 3.83V (vs. Li-In) Charging termination current: 0.01C Discharging method: CC Discharge rate: 0.05C Discharge termination voltage: 2.38V (vs. Li-In) Subsequently, charge and discharge were performed under the following first charge and discharge conditions: Charging method: CCCV Charging rate: 0.05C Charging control voltage: 3.83V (vs. Li-In) Charging termination current: 0.01C Discharging method: CC Discharge rate: 0.1C Discharge termination voltage: 2.38V (vs. Li-In) After that, charge and discharge were performed under the following second charge and discharge conditions. Charging method: CCCV Charging rate: 0.05C Charging control voltage: 3.83V (vs. Li-In) Charging termination current: 0.01C Discharging method: CC Discharge rate: 1C Discharge termination voltage: 2.38V (vs. Li-In) The discharge maintenance rate was calculated as the ratio of the discharge capacity under the second charge-discharge condition (1C discharge capacity) to the discharge capacity under the first charge-discharge condition (0.1C discharge capacity).

[0051] <Length Measurement> For the positive electrode 20 according to Example 1, the length ratio L / Lp was measured by SEM using the method described above. In addition, the ratio of the lengths of crystal planes other than the {001} plane (crystal planes intersecting the {001} plane) and the {116} plane on the first principal surface was measured by TEM using the method described above. Here, the ratio of the lengths of crystal planes other than the {001} plane or the {116} plane on the first principal surface was calculated from the difference between the ratio of crystal planes other than the {001} plane on the first principal surface and the ratio of the lengths of the {116} plane on the first principal surface.

[0052] (Example 2) In Example 2, the positive electrode was manufactured by cooling it at a slower rate than in Example 1 during the heat treatment process for manufacturing the positive electrode, but otherwise the battery was manufactured and measured in the same manner as in Example 1.

[0053] (Example 3) In Example 3, the battery was manufactured and measured in the same manner as in Example 1, except that the sputtering time in the positive electrode coating layer formation process was adjusted to make the thickness of the positive electrode coating layer 450 nm.

[0054] (Example 4) In Example 4, in the process of forming the positive electrode coating layer, Li ３ PO ４ Except for forming a Li-P oxide positive electrode coating layer using a target (manufactured by Toyoshima Seisakusho), the battery was fabricated and measured in the same manner as in Example 1.

[0055] (Example 5) In Example 5, in the process of forming the positive electrode coating layer, the positive electrode current collector on which the positive electrode active material layer has been formed and 25 mg of Li ３ InCl ６ The powder is sequentially placed into a 10 mm diameter zirconia cylinder, resulting in a concentration of 1 tf / cm². ２ A positive electrode coating layer with a thickness of 20 μm was fabricated by compressing it into pellets at min (min). The negative electrode was made of Li, which is the negative electrode active material. ６ Ti ５ O １２ and the solid electrolyte Li ３ InCl ６ The two materials were mixed in a volume ratio of 50:50 and pressed together to form the structure. Otherwise, the battery was fabricated and measured in the same manner as in Example 1. In Example 5, a solid electrolyte layer was not formed. As a result, the positive electrode coating layer functions as a solid electrolyte, allowing for the movement of carrier ions while maintaining insulation between the positive and negative electrodes.

[0056] (Example 6) In Example 6, in the process of forming the positive electrode coating layer, the positive electrode current collector on which the positive electrode active material layer has been formed and 25 mg of Li ３ InCl ６ The powder is placed in a 10 mm diameter zirconia cylinder and measured at 1 tf / cm². ２ A 20 μm thick positive electrode coating layer was prepared by compacting the material at min(1) and forming pellets. Otherwise, the battery was prepared and measured in the same manner as in Example 1. In Example 6, a solid electrolyte layer was not formed. As a result, the positive electrode coating layer functions as a solid electrolyte, allowing for the movement of carrier ions while maintaining insulation between the positive and negative electrodes.

[0057] (Example 7) In Example 7, the positive electrode was manufactured by increasing the heating rate and cooling rate during the heat treatment process compared to Example 1, except that the battery was manufactured and measured in the same manner as in Example 1.

[0058] (Example 8) In Example 8, the positive electrode was manufactured by reducing the heating rate and cooling rate during the heat treatment process compared to Example 1, except that the battery was manufactured and measured in the same manner as in Example 1.

[0059] (Example 9) In Example 9, the positive electrode was manufactured by reducing the heating rate and cooling rate during the heat treatment process compared to Example 8, except that the battery was manufactured and measured in the same manner as in Example 8.

[0060] (Comparative Example 1) In Comparative Example 1, the positive electrode was manufactured by further reducing the heating rate and cooling rate compared to Example 8 during the heat treatment process for manufacturing the positive electrode. Otherwise, the battery was manufactured and measured in the same manner as in Example 9.

[0061] (Comparative Example 2) In Comparative Example 2, the battery was manufactured and measured in the same manner as in Example 1, except that the positive electrode coating layer was not formed.

[0062] Table 1 shows Examples 1 to 9 and Comparative Examples 1 to 2.

[0063]

[0064] As shown in Table 1, in Examples 1 to 9, where the ratio of the lengths of crystal planes other than the {001} plane on the first main surface was greater than 0.28, the charge retention rate was improved compared to Comparative Example 1, where the ratio of the lengths of crystal planes other than the {001} plane on the first main surface was 0.28 or less. Therefore, it can be seen that the charge-discharge characteristics can be improved by making the ratio of the lengths of crystal planes intersecting the {001} plane on the first main surface greater than 0.28.

[0065] As shown in Table 1, in Examples 1 to 9, where the ratio of the lengths of crystal planes other than the {001} plane on the first main surface was 0.55 or more, the charge retention rate was improved compared to Comparative Example 1, where the ratio of the lengths of crystal planes other than the {001} plane on the first main surface was less than 0.55. Therefore, it can be seen that the charge-discharge characteristics can be improved by making the ratio of the lengths of crystal planes intersecting the {001} plane on the first main surface greater than 0.28.

[0066] As shown in Table 1, in Examples 1 and 4 to 6, where the ratio of the lengths of crystal planes other than the {001} plane on the first main surface was 0.79 or more and 0.90 or less, the charge retention rate was more improved compared to Examples 2, 3 and 7 to 9, where the ratio of the lengths of crystal planes other than the {001} plane on the first main surface was less than 0.79 or greater than 0.90. Therefore, it can be seen that the charge-discharge characteristics can be further improved by having the ratio of the lengths of crystal planes intersecting the {001} plane on the first main surface be 0.79 or more and 0.90 or less.

[0067] As shown in Table 1, in Examples 1 to 9, where the ratio of the length of the {116} plane on the first main surface was greater than 0.05, the charge retention rate was improved compared to Comparative Example 1, where the ratio of the length of the {116} plane on the first main surface was 0.05 or less. Therefore, it can be seen that the charge-discharge characteristics can be improved by making the ratio of the length of the {116} plane on the first main surface greater than 0.05.

[0068] As shown in Table 1, in Examples 1 to 9, where the ratio of the length of the {116} plane on the first main surface was 0.35 or more, the charge retention rate improved compared to Comparative Example 1, where the ratio of the length of the {116} plane on the first main surface was less than 0.35. Therefore, it can be seen that the charge-discharge characteristics can be improved by setting the ratio of the length of the {116} plane on the first main surface to 0.35 or more.

[0069] As shown in Table 1, in Examples 1 to 9, which have a positive electrode coating layer, the charge retention rate was improved compared to Comparative Example 2, which does not have a positive electrode coating layer. Therefore, it can be seen that having a positive electrode coating layer can improve charge and discharge characteristics.

[0070] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention may be modified or improved without departing from its spirit, and equivalents thereof are also included.

[0071] For example, the embodiment shows a configuration in which a laminated electrode body, applicable to coin-type or button-type batteries, is used as the battery 10, but it is not limited to this. The battery 10 of this disclosure may also be configured to use a wound electrode body, applicable to cylindrical or laminate film type batteries, for example.

[0072] Furthermore, this disclosure may also take the following form.

[0073] (1) A battery having a positive electrode and a negative electrode, wherein the positive electrode comprises a positive electrode active material layer having a first main surface and a second main surface opposite to the first main surface, a positive electrode coating layer having electronic insulating properties located on the first main surface side of the positive electrode active material layer, and a positive electrode current collector located on the second main surface side of the positive electrode active material layer, wherein the positive electrode active material layer is a continuum in which a positive electrode active material having a layered rock salt type structure is continuously formed from the first main surface to the second main surface, the first main surface has a crystal plane that intersects with the {001} plane among the crystal planes of the layered rock salt type structure, and the ratio of the length of the crystal plane intersecting with the {001} plane to the length of the surface of the first main surface, as seen in a cross-section along the thickness direction of the positive electrode active material layer measured by a transmission electron microscope, is greater than 0.28. (2) The battery according to (1), wherein the ratio of the length of the crystal plane intersecting the {001} plane to the length of the surface of the first main surface, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is 0.55 or more. (3) The battery according to (2), wherein the ratio of the length of the crystal plane intersecting the {001} plane to the length of the surface of the first main surface, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is 0.79 or more and 0.90 or less. (4) The battery according to any one of (1) to (3), wherein the first main surface has at least one crystal plane among the {116} plane, {012} plane and {104} plane of the layered rock salt type structure. (5) The battery according to (4), wherein the first main surface has the {116} plane. (6) The battery according to (5), wherein the ratio of the length of the {116} plane to the length of the surface of the first main plane, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is greater than 0.05. (7) The battery according to (6), wherein the ratio of the length of the {116} plane to the length of the surface of the first main plane, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is 0.35 or more.(8) The battery according to any one of (1) to (7), wherein the ratio of the length of the surface of the first main surface appearing in a cross-section along the thickness direction of the positive electrode active material layer, as measured by a scanning electron microscope, to the length of the positive electrode active material layer in the direction along the surface of the positive electrode current collector is 1.14 or more. (9) The battery according to any one of (1) to (8), wherein the positive electrode coating layer comprises a compound containing Li, at least one of B, Al, Si, P, Ti, Ge, Zr, Nb, In, Sn, Hf, Ta, and W, and at least one of O, S, N, F, Cl, Br, and I. (10) The battery according to (9), wherein the positive electrode coating layer comprises a compound containing Li, at least one of Nb, P, and In, and at least one of O, Cl, and N. (11) The battery according to any one of (1) to (10), wherein the thickness of the positive electrode coating layer is 5 nm or more. (12) The battery according to any one of (1) to (11), further comprising a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer comprises a lithium compound which is at least one of a composite oxide, oxide, nitride, sulfide, sulfate, phosphate, carbonate, borate, and conductive polymer, comprising at least one of Si, Ti, Sn, and Al. (13) The battery according to any one of (1) to (12), further comprising a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer comprises a solid electrolyte containing S.

[0074] 10 battery 20 positive electrode 21 positive electrode current collector 22 positive electrode active material layer 23 positive electrode coating layer 30 negative electrode 31 negative electrode current collector 32 negative electrode active material layer 40 solid electrolyte layer

Claims

1. A battery having a positive electrode and a negative electrode, wherein the positive electrode comprises a positive electrode active material layer having a first main surface and a second main surface opposite to the first main surface, a positive electrode coating layer having electronic insulating properties located on the first main surface side of the positive electrode active material layer, and a positive electrode current collector located on the second main surface side of the positive electrode active material layer, wherein the positive electrode active material layer is a continuum in which a positive electrode active material having a layered rock salt type structure is continuously formed from the first main surface to the second main surface, the first main surface has a crystal plane that intersects with the {001} plane among the crystal planes of the layered rock salt type structure, and the ratio of the length of the crystal plane intersecting with the {001} plane to the length of the surface of the first main surface, as seen in a cross-section along the thickness direction of the positive electrode active material layer measured by a transmission electron microscope, is greater than 0.

28.

2. The battery according to claim 1, wherein the ratio of the length of the crystal plane intersecting the {001} plane to the length of the surface of the first main plane, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is 0.55 or more.

3. The battery according to claim 2, wherein the ratio of the length of the crystal plane intersecting the {001} plane to the length of the surface of the first main plane, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is 0.79 or more and 0.90 or less.

4. The battery according to any one of claims 1 to 3, wherein the first main surface has at least one crystal face among the {116} face, {012} face and {104} face of the layered rock salt type structure.

5. The battery according to claim 4, wherein the first main surface has the {116} surface.

6. The battery according to claim 5, wherein the ratio of the length of the {116} plane to the length of the surface of the first main plane, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is greater than 0.

05.

7. The battery according to claim 6, wherein the ratio of the length of the {116} plane to the length of the surface of the first main plane, as measured by a transmission electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, is 0.35 or more.

8. The battery according to any one of claims 1 to 7, wherein the ratio of the length of the surface of the first main surface, as measured by a scanning electron microscope in a cross-section along the thickness direction of the positive electrode active material layer, to the length of the positive electrode active material layer in the direction along the surface of the positive electrode current collector is 1.14 or more.

9. The battery according to any one of claims 1 to 8, wherein the positive electrode coating layer comprises a compound containing Li, at least one of B, Al, Si, P, Ti, Ge, Zr, Nb, In, Sn, Hf, Ta, and W, and at least one of O, S, N, F, Cl, Br, and I.

10. The battery according to claim 9, wherein the positive electrode coating layer comprises a compound containing Li, at least one of Nb, P, and In, and at least one of O, Cl, and N.

11. The battery according to any one of claims 1 to 10, wherein the thickness of the positive electrode coating layer is 5 nm or more.

12. The battery according to any one of claims 1 to 11, further comprising a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer comprises a lithium compound which is at least one of a composite oxide, oxide, nitride, sulfide, sulfate, phosphate, carbonate, borate, and conductive polymer, comprising at least one of Si, Ti, Sn, and Al.

13. The battery according to any one of claims 1 to 12, further comprising a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer comprises a solid electrolyte containing S.

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