Manufacturing method for all-solid-state lithium batteries

Abstract

To provide a method for manufacturing an all-solid-state lithium battery that can be charged at a low voltage. [Solution] The all-solid-state lithium battery comprises a solid electrolyte layer, a positive electrode layer containing Li adjacent to the solid electrolyte layer in the thickness direction, a first current collector provided at one end in the thickness direction, and a second current collector provided at the opposite end in the thickness direction. In the method for manufacturing the all-solid-state lithium battery, a process is performed to remove water contained in an inert gas, the inert gas after the process is supplied into a chamber of a thin-film forming apparatus configured to form a thin film using the plasma of the inert gas, and at least the positive electrode layer is formed by the thin-film forming apparatus.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing an all-solid-state lithium battery. [Background technology]

[0002] Patent Document 1 discloses an all-solid-state lithium battery. This all-solid-state lithium battery has a structure in which a negative electrode composite layer, a solid electrolyte layer, and a positive electrode composite layer are stacked in that order. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 7359173 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Conventionally, all-solid-state lithium batteries could not be charged unless a high voltage was applied. In one aspect of this disclosure, it is preferable to provide a method for manufacturing an all-solid-state lithium battery that can be charged at a low voltage. [Means for solving the problem]

[0005] One aspect of this disclosure is a method for manufacturing an all-solid-state lithium battery, comprising: a solid electrolyte layer; a positive electrode layer containing Li, adjacent to the solid electrolyte layer in the thickness direction; a first current collector provided at one end in the thickness direction; and a second current collector provided at the opposite end in the thickness direction.

[0006] In the method for manufacturing an all-solid-state lithium battery, a process is performed to remove water contained in an inert gas, and the inert gas after the process is supplied into the chamber of a thin-film forming apparatus configured to form a thin film using the plasma of the inert gas, and at least the positive electrode layer is formed by the thin-film forming apparatus.

[0007] According to one aspect of this disclosure, a method for manufacturing an all-solid-state lithium battery, it is possible to manufacture an all-solid-state lithium battery that can be charged at a low voltage. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1A is a plan view showing the configuration of an all-solid-state lithium battery. Figure 1B is a cross-sectional view of Figure 1A along the IB-IB section. [Figure 2] This is an explanatory diagram illustrating the charging state of an all-solid-state lithium battery. [Figure 3] This is an explanatory diagram showing the configuration of a magnetron sputtering apparatus. [Figure 4] This is an explanatory diagram showing the configuration of an argon gas supply system. [Figure 5] Figure 5A is a photograph showing a magnetron sputtering apparatus. Figure 5B is a photograph showing an argon gas supply apparatus. [Figure 6] This is an explanatory diagram showing the configuration of an apparatus for measuring the concentrations of H and Li contained in the positive electrode layer. [Figure 7] This is an explanatory diagram illustrating the principle of the recoil particle detection method. [Figure 8] Figure 8A is a graph showing the measurement results of H and Li concentrations in the all-solid-state lithium battery of the example. Figure 8B is a graph showing the measurement results of H and Li concentrations in the all-solid-state lithium battery of the comparative example. [Figure 9] Figure 9A is the graph from Figure 8A, normalized with the Counts for no voltage applied set to 1. Figure 9B is the graph from Figure 8B, normalized with the Counts for no voltage applied set to 1. [Figure 10] This graph shows the relationship between the applied voltage and the value of x, which represents the Li concentration in LixCoO2, for each of the all-solid-state lithium batteries in the examples and comparative examples. [Figure 11]FIG. 11A is a model diagram illustrating a state in which Li moves without being affected by H in the all-solid-state lithium battery of the example. FIG. 11B is a model diagram illustrating a state in which Li is affected by H and is difficult to move in the all-solid-state lithium battery of the comparative example. [Mode for Carrying Out the Invention]

[0009] Exemplary embodiments of the present disclosure will be described with reference to the drawings. <First Embodiment> 1. Configuration of All-Solid-State Lithium Battery 1 The configuration of the all-solid-state lithium battery 1 will be described based on FIG. 1A, FIG. 1B, and FIG. 2. The all-solid-state lithium battery 1 has, for example, a plate-like form. As shown in FIG. 1A, the all-solid-state lithium battery 1 has, for example, a rectangular shape in plan view.

[0010] As shown in FIG. 1B, the all-solid-state lithium battery 1 includes a solid electrolyte layer 3, a positive electrode layer 5, a first current collector 7, and a second current collector 9. Examples of the solid electrolyte constituting the solid electrolyte layer 3 include Li 1.4 Al 0.4 Ti 0.9 Ge 0.7 P3O 12 , Li 1.8 Al 0.8 Ti 0.6 Ge 0.6 P 2.3 O 12 , and Li 2.9 Al 0.9 Ti 1.1 Si 1.0 P2O 12 (LATP) and the like. The thickness of the solid electrolyte layer 3 is, for example, 20 μm or more and 150 μm or less.

[0011] The positive electrode layer 5 is adjacent to the solid electrolyte layer 3 in the thickness direction T of the all-solid-state lithium battery 1. The positive electrode layer 5 contains Li. Examples of the material of the positive electrode layer 5 include lithium cobaltate (LiCoO2), LiFePO4, LiMnO2 and the like. The thickness of the positive electrode layer 5 is, for example, 30 nm or more and 1000 nm or less.

[0012] The first current collector 7 is located at one end in the thickness direction T. The first current collector 7 is adjacent to the positive electrode layer 5 in the thickness direction T. The second current collector 9 is located at the opposite end in the thickness direction T. The second current collector 9 is adjacent to the solid electrolyte layer 3 in the thickness direction T.

[0013] Examples of materials for the first current collector 7 and the second current collector 9 include metals. Examples of metals include Au, Pt, Ag, Cu, Al, and Fe. The thickness of the first current collector 7 is, for example, 10 nm to 30 nm. The thickness of the second current collector 9 is, for example, 10 nm to 30 nm.

[0014] Figure 2 shows the state of the all-solid-state lithium battery 1 while it is being charged. The second current collector 9 is grounded. A positive voltage is applied to the first current collector 7 by the power supply 11. The Li contained in the positive electrode layer 5 + Ions move to the side of the solid electrolyte layer 3 that faces the second current collector 9. As a result, an in-situ negative electrode 13 is formed on the side of the solid electrolyte layer 3 that faces the second current collector 9. The composition of the in-situ negative electrode 13 is, for example, Li x Ti y (PO4)3. The potential of the in-situ negative electrode 13 is, for example, 2.35V vs. Li / Li + The following applies: When the all-solid-state lithium battery 1 is being discharged, Li is present in the in-situ negative electrode 13. + The ions move towards the positive electrode layer 5.

[0015] 2. Manufacturing method of all-solid-state lithium battery 1 A method for manufacturing an all-solid-state lithium battery 1 will be explained based on Figures 3 to 5. The magnetron sputtering apparatus 21 shown in Figure 3 is used for manufacturing the all-solid-state lithium battery 1. The magnetron sputtering apparatus 21 has a known configuration.

[0016] The magnetron sputtering apparatus 21 is equipped with a vacuum chamber 23. The vacuum chamber 23 is provided with an argon gas introduction section 25 and a vacuum exhaust section 27. Argon gas 29 is introduced into the vacuum chamber 23 from the argon gas introduction section 25. Argon gas 29 corresponds to an inert gas. The vacuum exhaust section 27 performs exhaust, and the inside of the vacuum chamber 23 becomes a high vacuum.

[0017] The magnetron sputtering apparatus 21 includes a target holder 31 and a sample holder 33 within a vacuum chamber 23. A target 35 is mounted on the target holder 31. A sample 37 is mounted on the sample holder 33. The magnetron sputtering apparatus 21 is equipped with an RF power supply 41. The RF power supply 41 applies a high-frequency voltage to the target holder 31.

[0018] The magnetron sputtering apparatus 21 includes a heater 43 and a heating device 45. The heater 43 is in contact with the sample holder 33. The heater 43 and the heating device 45 heat the sample holder 33 and the sample 37. Figure 5A shows a photograph of the magnetron sputtering apparatus 21. The magnetron sputtering apparatus 21 corresponds to a thin film forming apparatus configured to form thin films using an inert gas plasma.

[0019] The manufacturing method for the all-solid-state lithium battery 1 uses the argon gas supply device 51 shown in Figure 4. The argon gas supply device 51 is a device that supplies argon gas 29 with a low water content to the argon gas inlet 25. The argon gas supply device 51 comprises an argon gas cylinder 53, a regulator 55, piping 57, a backflow prevention unit 59, and a liquid nitrogen trap 61.

[0020] Argon gas cylinder 53 stores argon gas 29. Regulator 55 adjusts the pressure of the argon gas 29 sent from argon gas cylinder 53 to piping 57. The pressure of the argon gas 29 is, for example, 3 kPa or less. Piping 57 sends the argon gas 29 from argon gas cylinder 53 to argon gas inlet 25. A backflow prevention unit 59 is installed in the middle of piping 57. The backflow prevention unit 59 leaks when the pressure in piping 57 exceeds 2 kPa, preventing backflow.

[0021] The liquid nitrogen trap 61 consists of a container 61A and liquid nitrogen 61B held within the container 61A. Part of the piping 57 passes through the liquid nitrogen 61B and comes into contact with it. When argon gas 29 passes through the portion of piping 57 that is in the liquid nitrogen 61B, the water contained in the argon gas 29 freezes on the inner surface of piping 57. As a result, the water contained in the argon gas 29 is removed. The amount of water contained in the argon gas 29 that has passed through the liquid nitrogen trap 61 is less than the amount of water contained in the argon gas 29 stored in the argon gas cylinder 53. Note that liquid nitrogen 61B corresponds to a substance with a temperature lower than the freezing point of water. Figure 5B shows a photograph of the argon gas supply device 51.

[0022] The manufacturing method for the all-solid-state lithium battery 1 is as follows: A solid electrolyte layer 3 is attached to a sample holder 33 as a sample 37. A target 35 is attached to a target holder 31. The target 35 has the same composition as the positive electrode layer 5.

[0023] Next, the solid electrolyte layer 3 is heated using the heater 43 and the heating device 45. For example, the solid electrolyte layer 3 is heated to approximately 400-600°C. Then, the argon gas 29 supplied by the argon gas supply device 51 is introduced into the vacuum chamber 23 from the argon gas introduction section 25 to generate argon plasma.

[0024] Next, while introducing O2 into the vacuum chamber 23 at a flow rate of 2 kPa or less, the positive electrode layer 5 is deposited on only one side of the solid electrolyte layer 3. Then, the target 35 is replaced with one having the same composition as the first current collector 7, and the first current collector 7 is deposited on top of the positive electrode layer 5.

[0025] Next, the front and back of sample 37 are reversed. Also, target 35 is replaced with one having the same composition as the second current collector 9. Then, the second current collector 9 is deposited onto the surface of the solid electrolyte layer 3, on the side opposite to the positive electrode layer 5. Through these steps, the all-solid-state lithium battery 1 is completed.

[0026] 3. Effects of the manufacturing method of the all-solid-state lithium battery 1 (1A) According to the method for manufacturing an all-solid-state lithium battery 1 of the present disclosure, an all-solid-state lithium battery 1 that can be charged at a low voltage can be manufactured. Because it can be charged at a low voltage, rapid charging becomes possible. Also, because it can be charged at a low voltage, the all-solid-state lithium battery 1 is less likely to deteriorate even after repeated charging and discharging.

[0027] (1B) In the method for manufacturing the all-solid-state lithium battery 1 of the present disclosure, the pipe 57 through which the argon gas 29 flows is brought into contact with liquid nitrogen 61B, thereby freezing the water contained in the argon gas 29 on the inner surface of the pipe 57. As a result, the effect of removing the water contained in the argon gas 29 is further enhanced. Consequently, the effect of (1A) becomes even more pronounced.

[0028] 4. Examples (4-1) Manufacturing of an all-solid-state lithium battery 1 of the example The all-solid-state lithium battery 1 of the example was manufactured using the manufacturing method described above. The solid electrolyte layer 3 attached to the sample holder 33 was made of LATP. The solid electrolyte layer 3 was a square plate in plan view. The length of one side of the square was 25.4 mm. The thickness of the solid electrolyte layer 3 was 150 μm. The solid electrolyte layer 3 was heated in the vacuum chamber 23 so that its temperature reached 400°C.

[0029] The positive electrode layer 5 was made of LiCoO2. The thickness of the positive electrode layer 5 was approximately 82 nm. The material of the first current collector 7 was Au. The thickness of the first current collector 7 was approximately 11 nm. The material of the second current collector 9 was Pt. The thickness of the second current collector 9 was approximately 10 nm.

[0030] (4-2) Comparative Example: Manufacturing of All-Solid-State Lithium Battery R The comparative example, the all-solid-state lithium battery R, ​​was manufactured using essentially the same method as the manufacturing method for the all-solid-state lithium battery 1 in the example. However, when manufacturing the all-solid-state lithium battery R, ​​the argon gas 29 supplied to the argon gas introduction section 25 did not pass through the liquid nitrogen trap 61. Therefore, the argon gas 29 supplied to the argon gas introduction section 25 contained more water than the argon gas used when manufacturing the all-solid-state lithium battery 1.

[0031] (4-3) Evaluation of all-solid-state lithium batteries 1 and R For all-solid-state lithium batteries 1 and R, the concentrations of H and Li contained in the positive electrode layer 5 were measured using the recoil particle detection method. The apparatus shown in Figure 6 was used to measure the concentrations of H and Li.

[0032] The all-solid-state lithium battery 1,R was installed inside the chamber 71. An ion beam 75 was directed from the tandem accelerator 73 towards the first current collector 7 of the all-solid-state lithium battery 1,R. The ion beam 75 was 9 Mev O 4+ The incident angle of the ion beam 75 on the surface of the first current collector 7 was 15°C.

[0033] A detector 77 was placed on the path of recoiling particles with a reflection angle of 15°. A filter 79 was placed between the all-solid-state lithium battery 1, R and the detector 77. The filter 79 was made of aluminum foil with a thickness of 6 μm. When performing the measurement, a voltage was applied between the first current collector 7 and the second current collector 9 using an electrochemical measuring device 81.

[0034] When the ion beam 75 is directed toward the first current collector 7, as shown in Figure 7, the H and Li contained in the positive electrode layer 5 become recoil particles and are incident on the detector 77. The detector 77 detects the energy of the incident recoil particles.

[0035] The measurement results for all-solid-state lithium battery 1 are shown in Figure 8A. The measurement results for all-solid-state lithium battery R are shown in Figure 8B. In Figures 8A and 8B, the horizontal axis (Channel Number) represents the energy magnitude of the recoil particles detected by detector 77. In Figures 8A and 8B, the vertical axis (Counts) represents the number of recoil particles detected by detector 77.

[0036] Figures 8A and 8B show the measurement results when no voltage is applied between the first current collector 7 and the second current collector 9 (no-bias), and when a voltage is applied. The voltages applied between the first current collector 7 and the second current collector 9 (hereinafter referred to as applied voltage) were 0.4V, 0.8V, 1.0V, 1.2V, 1.4V, 1.6V, 1.8V, 2.3V, or 2.8V. Note that when the applied voltage is a positive value, the first current collector 7 is at a higher potential than the second current collector 9.

[0037] In Figures 8A and 8B, the counts around Channel Number 450 are due to H contained in the positive electrode layer 5. In Figures 8A and 8B, the counts around Channel Number 500-800 are due to Li contained in the positive electrode layer 5. In all-solid-state lithium battery 1, there was less H contained in the positive electrode layer 5 compared to all-solid-state lithium battery R.

[0038] The graph in Figure 9A is the graph in Figure 8A, normalized by setting the Counts for the case where no voltage is applied (no-bias) to 1. The graph in Figure 9B is the graph in Figure 8B, normalized by setting the Counts for the case where no voltage is applied (no-bias) to 1.

[0039] Figure 10 shows the relationship between the applied voltage and the value of x for all-solid-state lithium batteries 1 and R, respectively. x is the formula representing the composition of the positive electrode layer 5, Li x In CoO2, this number represents the amount of Li. The value of x in all-solid-state lithium battery 1 is the value on the vertical axis in Figure 9A when the Channel Number is 800. The value of x in all-solid-state lithium battery R is the value on the vertical axis in Figure 9B when the Channel Number is 800.

[0040] As shown in Figure 10, in the all-solid-state lithium battery 1, the value of x decreased significantly even when the applied voltage was around 0.4V. This is because even at low applied voltages, as shown in Figure 2, Li + This indicates that ion movement occurs, allowing the all-solid-state lithium battery 1 to be charged.

[0041] In contrast, with the all-solid-state lithium battery R, ​​the value of x did not decrease easily when the applied voltage was around 0.4V. For the value of x to decrease significantly, the applied voltage needed to be 1.0V or higher. This indicates that the all-solid-state lithium battery R cannot be charged at low applied voltages.

[0042] The reason why the all-solid-state lithium battery 1 can be charged even at low applied voltages is presumed to be as follows: Because there is little water in the argon gas 29 used in manufacturing, there is little H in the positive electrode layer 5, as shown in Figure 11A. Therefore, Li is accumulated as intercalation between the cobalt oxide layers that make up the positive electrode layer 5. + Ions are less hindered by H (hydrogen) movement. As a result, the all-solid-state lithium battery 1 can be charged even at low applied voltages.

[0043] In an all-solid-state lithium battery R, ​​the reason it cannot be charged when the applied voltage is low is that there is a lot of water in the argon gas 29 used in manufacturing, so as shown in Figure 11B, there is a lot of H in the positive electrode layer 5, and Li + This is presumably because the movement of ions is hindered.

[0044] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented in various modified forms.

[0045] (1) The substance used to trap water contained in the inert gas may be a substance other than liquid nitrogen. For example, dry ice, liquid helium, etc., can be used. (2) The process for removing water contained in the inert gas may be any other process. For example, the process may involve bringing the inert gas into contact with an adsorbent that adsorbs water.

[0046] (3) The thin film formation apparatus used to form the positive electrode layer 5, etc., may be an apparatus other than the magnetron sputtering apparatus 21. Examples of apparatus other than the magnetron sputtering apparatus 21 include an electron beam deposition apparatus and a laser ablation apparatus.

[0047] (4) The inert gas supplied into the vacuum chamber 23 may be a gas other than argon gas 29. Examples of gases other than argon gas 29 include neon gas and krypton gas. (5) The all-solid-state lithium battery 1 of the present disclosure may have a structure in which a negative electrode composite layer, a solid electrolyte layer, and a positive electrode composite layer are stacked in this order, similar to the one described in Patent Document 1. The positive electrode composite layer contains lithium. The positive electrode composite layer contains, for example, lithium cobalt oxide. When forming the positive electrode composite layer, for example, a magnetron sputtering apparatus 21 and an argon gas supply apparatus 51 are used. (6) The function of one component in each of the above embodiments may be divided among multiple components, or the function of multiple components may be performed by one component. Also, some of the configurations of each of the above embodiments may be omitted. Also, at least some of the configurations of each of the above embodiments may be added to, replaced with, etc., the configurations of other embodiments.

[0048] (7) In addition to a method for manufacturing the all-solid-state lithium battery 1, this disclosure can also be realized in various forms, such as the all-solid-state lithium battery 1, a system in which the all-solid-state lithium battery 1 is a component.

[0049] [Technical concepts disclosed in this specification] [Item 1] A solid electrolyte layer, In the thickness direction, adjacent to the solid electrolyte layer, a positive electrode layer containing Li is provided. A first current collector is provided at one end in the thickness direction, A second current collector is provided at the opposite end in the thickness direction, A method for manufacturing an all-solid-state lithium battery comprising: Perform a process to remove water contained in the inert gas. The inert gas after the above process is supplied into the chamber of a thin-film forming apparatus configured to form a thin film using the plasma of the inert gas. The thin film forming apparatus forms at least the positive electrode layer. A method for manufacturing all-solid-state lithium batteries. [Item 2] A method for manufacturing an all-solid-state lithium battery as described in item 1, The aforementioned process involves bringing the pipe through which the inert gas flows into contact with a substance whose temperature is lower than the melting point of water, thereby freezing the water contained in the inert gas on the inner surface of the pipe. A method for manufacturing all-solid-state lithium batteries. [Item 3] A method for manufacturing an all-solid-state lithium battery as described in item 2, The substance whose temperature is lower than the melting point of water is liquid nitrogen. A method for manufacturing all-solid-state lithium batteries. [Item 4] A method for manufacturing an all-solid-state lithium battery as described in any one of items 1 to 3, The positive electrode layer contains lithium cobalt oxide, A method for manufacturing all-solid-state lithium batteries. [Item 5] A method for manufacturing an all-solid-state lithium battery as described in any one of items 1 to 3, The thin film forming apparatus is a magnetron sputtering apparatus. A method for manufacturing all-solid-state lithium batteries. [Item 6] A method for manufacturing an all-solid-state lithium battery as described in any one of items 1 to 5, The aforementioned inert gas includes argon gas. A method for manufacturing all-solid-state lithium batteries. [Explanation of symbols]

[0050] 1…All-solid-state lithium battery, 3…Solid electrolyte layer, 5…Positive electrode layer, 7…First current collector, 9…Second current collector, 11…Power supply, 13…In-situ negative electrode, 21…Magnetron sputtering apparatus, 23…Vacuum chamber, 25…Argon gas introduction section, 27…Vacuum exhaust section, 29…Argon gas, 31…Target holder, 33…Sample holder, 35…Target, 37…Sample, 41…RF power supply, 43…Heater, 45…Heating device, 51…Argon gas supply device, 53…Argon gas cylinder, 55…Regulator, 57…Piping, 59…Backflow prevention section, 61…Liquid nitrogen trap, 61A…Container, 61B…Liquid nitrogen, 71…Chamber, 73…Tandem accelerator, 75…Ion beam, 77…Detector, 79…Filter, 81…Electrochemical measuring device

Claims

1. A solid electrolyte layer, In the thickness direction, adjacent to the solid electrolyte layer, a positive electrode layer containing Li is provided, A first current collector is provided at one end in the thickness direction, A second current collector is provided at the opposite end in the thickness direction, A method for manufacturing an all-solid-state lithium battery comprising: Perform a process to remove water contained in the inert gas. The inert gas after the above process is supplied into the chamber of a thin-film forming apparatus configured to form a thin film using the plasma of the inert gas. The thin film forming apparatus forms at least the positive electrode layer. A method for manufacturing all-solid-state lithium batteries.

2. A method for manufacturing an all-solid-state lithium battery according to claim 1, The aforementioned process involves bringing the pipe through which the inert gas flows into contact with a substance whose temperature is lower than the melting point of water, thereby freezing the water contained in the inert gas on the inner surface of the pipe. A method for manufacturing all-solid-state lithium batteries.

3. A method for manufacturing an all-solid-state lithium battery according to claim 2, The substance whose temperature is lower than the melting point of water is liquid nitrogen. A method for manufacturing all-solid-state lithium batteries.

4. A method for manufacturing an all-solid-state lithium battery according to claim 1 or 2, The positive electrode layer contains lithium cobalt oxide, A method for manufacturing all-solid-state lithium batteries.

5. A method for manufacturing an all-solid-state lithium battery according to claim 1 or 2, The thin film forming apparatus is a magnetron sputtering apparatus. A method for manufacturing all-solid-state lithium batteries.

6. A method for manufacturing an all-solid-state lithium battery according to claim 1 or 2, The aforementioned inert gas includes argon gas. A method for manufacturing all-solid-state lithium batteries.

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