All-solid-state thin film battery and production process thereof

Abstract

The invention provides an all-solid-state thin film battery and a production process thereof, and belongs to the technical field of solid-state batteries, the all-solid-state thin film battery is characterized in that a positive electrode current collector layer is used as a positive electrode substrate, and a positive electrode layer, a solid electrolyte layer, a negative electrode layer and a negative electrode current collector layer are sequentially deposited by adopting a vacuum coating technology, the carbon source is a conductive carbon source, the sulfur source is a sulfur-containing electrode material, the sulfur-containing electrode material comprises elemental sulfur and one of compounds simultaneously containing the elemental sulfur and metal elements, and the carbon source is one or a combination of more than two of graphite, graphene and amorphous carbon. The invention provides an all-solid-state thin film battery and a production process thereof, and aims of facilitating mass production and uniform coating are fulfilled without an annealing step.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to an all-solid-state thin-film battery and a production process thereof. Background Art

[0002] The commonly used batteries on the market are as follows: (1) High-temperature Na-S batteries. Sodium-sulfur batteries are composed of a positive electrode, a negative electrode, an electrolyte, a separator and a shell. Unlike general secondary batteries (lead-acid batteries, nickel-cadmium batteries, etc.), sodium-sulfur batteries are composed of molten electrodes and solid electrolytes. The active material of the negative electrode is molten metal sodium, and the active material of the positive electrode is liquid sulfur and sodium polysulfide molten salt. It has the advantages of low cost, but its operating temperature needs to be controlled at 300-350℃, which is not suitable for fast start charging and discharging. Therefore, it is only suitable for the field of stationary energy storage and is prone to problems such as thermal runaway; ( 2) Liquid batteries: mainly liquid lithium batteries, which use liquid electrolytes and have advantages such as high energy density and long life, but have poor safety performance and are prone to fire and combustion, causing accidents; (3) All-solid-state batteries: batteries that use all-solid-state electrolytes and do not contain liquid components, have advantages such as thermal stability, non-flammability and non-explosion, and high energy density. However, the grain boundary impedance between the particles in its structure is large and the electron mobility is poor, resulting in poor charge and discharge performance and poor rate performance. However, thanks to the continuous advancement of technology, all-solid-state batteries are expected to gradually replace liquid lithium-ion batteries and become the mainstream battery technology.

[0003] All-solid-state thin-film batteries use the same electrochemical material system for the positive and negative electrodes as all-solid-state batteries, but the thickness of the active material layer is typically at the micrometer or nanometer level. These batteries offer advantages such as light weight, high energy density, and excellent safety. For example, patent publication number CN106207099B, entitled "A Three-Dimensional LiMn2O4 Thin-Film Positive Electrode and a Production Process for a Three-Dimensional All-Solid-State Thin-Film Battery," discloses a process using a Li-excess LiMn2O4 target. The chamber is evacuated, the substrate is heated, argon and oxygen are introduced, and the chamber pressure is adjusted. A three-dimensional LiMn2O4 thin film is formed on the substrate. The resulting three-dimensional LiMn2O4 thin film is annealed to form the positive electrode. A solid electrolyte film, a negative electrode film, and a negative current collector are sequentially deposited on the three-dimensional positive electrode film to form an all-solid-state thin-film battery. However, the all-solid-state thin-film battery described in this technical solution requires multiple annealing steps, resulting in a complex manufacturing process that limits its large-scale application and mass production. Furthermore, the battery exhibits low capacitance and uneven coating, resulting in poor performance.

[0004] In addition, patent publication number CN119481230A, entitled "A All-Solid-State Thin Film Battery and Its Preparation Method," discloses a new all-solid-state thin film battery prepared using a vacuum coating method using Na2S or S as a cathode target. However, Na2S or S are electronic insulating materials. To ensure that Na2S particles or S particles can smoothly release or receive electrons to achieve the charge and discharge process, in certain specific circumstances, when using a Na2S target or S target for coating, a carbon target also needs to be used for simultaneous coating to generate Na2S / C or S / C composite coated particles, thereby improving the charge and discharge efficiency of the cathode material. However, this dual-target simultaneous coating scenario not only greatly increases the coating process difficulty, but also makes it difficult to control the weight ratio of the various components in the Na2S / C composite film or S / C composite film, resulting in uneven coating and poor battery performance. Summary of the Invention

[0005] In view of this, the present invention provides an all-solid-state thin-film battery and its production process, which eliminates the need for an annealing step and avoids the process difficulties of simultaneous coating of two targets, thereby achieving the purpose of facilitating mass production and uniform coating.

[0006] To achieve the above objectives, the present invention provides an all-solid-state thin-film battery positive electrode composite target material, the composite target material raw materials include a carbon source and a sulfur source, the carbon source is a conductive carbon source, and the sulfur source is a sulfur-containing electrode material.

[0007] Optionally, the sulfur-containing electrode material includes one or a combination of sulfur and a compound containing both sulfur and metal elements.

[0008] Optionally, the compound containing both sulfur and metal elements is one or a combination of two or more of sodium sulfide, lithium sulfide, magnesium sulfide, aluminum sulfide, iron sulfide, and copper sulfide; and the sodium sulfide is one or a combination of two of sodium sulfide and sodium polysulfide.

[0009] Optionally, the carbon source is one or a combination of two or more of graphite, graphene and amorphous carbon.

[0010] In order to achieve the above-mentioned purpose, the present invention also provides a production process for a positive electrode composite target material for an all-solid-state thin-film battery, comprising the following steps: mixing a carbon source and a sulfur source, mechanically grinding them uniformly and then pressing them, and sintering them by vacuum hot pressing to obtain a positive electrode composite target material.

[0011] Optionally, the mass percentage of the sulfur source is 50wt%-98t%, and the mass percentage of the carbon source is 2wt%-50wt%; and the mechanical grinding is ball milling, sand milling or vibration milling.

[0012] Optionally, the vacuum hot pressing method is performed at a temperature of 100° C. to 600° C. and a pressure of 10 MPa to 500 MPa.

[0013] In order to achieve the above-mentioned purpose, the present invention also provides a production process for an all-solid-state thin-film battery, comprising the following steps: using the positive electrode collector layer as the positive electrode substrate, and using vacuum coating technology to sequentially deposit the positive electrode layer, solid electrolyte layer, negative electrode layer and negative electrode collector layer, wherein the target material of the positive electrode layer is a composite target material for the positive electrode of the all-solid-state thin-film battery.

[0014] Optionally, the weight proportion of the material with storage and discharge capabilities in the positive electrode layer is 50%-98%.

[0015] Optionally, the weight proportion of the material with storage and discharge capabilities in the positive electrode layer is 80%-97%.

[0016] Optionally, the weight proportion of the material with storage and discharge capabilities in the positive electrode layer is 90%-95%.

[0017] Optionally, the thickness of the positive electrode current collector layer is 10nm-1000μm; the thickness of the positive electrode layer is 10nm-50μm; the thickness of the solid electrolyte layer is 10nm-50μm; the thickness of the negative electrode layer is 10nm-50μm; the thickness of the negative electrode current collector layer is 0nm-1000μm.

[0018] Optionally, the thickness of the positive electrode current collector layer is any one of 10 nm, 100 nm, 1 μm, 5 μm, 10 μm, 20 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, and 1 mm.

[0019] Optionally, the thickness of the positive electrode layer is any one of 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 5 μm, 10 μm, and 50 μm.

[0020] Optionally, the thickness of the solid electrolyte layer is any one of 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 5 μm, 10 μm, and 50 μm.

[0021] Optionally, the thickness of the negative electrode layer is any one of 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 5 μm, 10 μm, and 50 μm.

[0022] Optionally, the thickness of the negative electrode current collector layer is any one of 0 nm, 10 nm, 100 nm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, and 1 mm.

[0023] Optionally, the vacuum coating technology is one or a combination of vacuum evaporation coating and magnetron sputtering coating.

[0024] Optionally, the material of the positive electrode current collector layer is one or a combination of two or more of copper foil, aluminum foil, stainless steel foil, composite copper foil, composite aluminum foil, metal film formed by plating, composite conductive film, etc.; the target material of the solid electrolyte layer is sodium phosphate, Na3La(PO4)2, Na-β-Al2O3, Na 1+x Zr2Si x P 3-x O 12 One or a combination of two or more types of sodium superion conductors.

[0025] Optionally, the target material of the negative electrode layer is one or a combination of two or more of tin, sodium-tin alloy, carbon sodium storage material, and composite materials containing sodium storage functional materials; the target material of the negative electrode current collector layer is one or a combination of two or more of sodium, tin, sodium-tin alloy, copper, and aluminum.

[0026] Optionally, the weight proportion of the material with storage and discharge capabilities in the negative electrode layer is 50%-100%.

[0027] Optionally, the weight proportion of the material with storage and discharge capabilities in the negative electrode layer is 80%-98%.

[0028] Optionally, the weight proportion of the material with storage and discharge capabilities in the negative electrode layer is 90%-97%.

[0029] In order to achieve the above object, the present invention also provides an all-solid-state thin film battery obtained by the above preparation process.

[0030] The above technical solution of the present invention includes at least the following beneficial effects: The technical solution provided by the present invention adopts a special target material combined with a production process, omitting the annealing step, avoiding the process difficulties of simultaneous coating of two targets, simplifying the coating process, and the prepared all-solid-state thin-film battery has high energy density, high battery rate performance, long battery life, cheap battery materials, low cost, safe battery, excellent high and low temperature resistance, and can be used under conditions of -40°C to 80°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1Schematic diagram of the cross-sectional structure of the all-solid-state thin-film battery in Example 1 of the present invention; Figure 2 This is a physical picture of the all-solid-state thin-film battery in Example 1 of the present invention; Figure 3 This is a scanning electron microscope image of a cross section of the all-solid-state thin-film battery in Example 1 of the present invention; Figure 4 Element distribution test results of the all-solid-state thin-film battery in Example 1 of the present invention; Figure 5 This is a charge and discharge curve diagram of the second cycle of the solid-state thin-film battery in Example 1. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0033] Example 1 An all-solid-state thin-film battery, including a target material for the cathode layer, is a composite target material. The production process for the composite target material comprises the following steps: mixing sodium sulfide and carbon, ball-milling them until uniform, then pressing them, and sintering them using vacuum hot pressing. The mass percentage of sodium sulfide (anhydrous, produced by Rizhao Yijie Xinyuan New Materials Co., Ltd., hereinafter the same) is 95% by weight, and the mass percentage of carbon powder (carbon nanofiber conductive agent, purchased from Shenzhen Kejing Zhida Technology Co., Ltd., hereinafter the same) is 5% by weight. The vacuum hot pressing conditions are a temperature of 300°C and a pressure of 300 MPa. The resulting composite target material is 95Na2S+5C (diameter 50×3 mm).

[0034] The positive electrode current collector layer is made of copper foil (20μm thick); the solid electrolyte layer target is Na₃PO₄ (φ50×3mm, purchased from Yipinchuancheng (Beijing) Technology Co., Ltd.); and the negative electrode layer target is Sn (φ50×3mm, purchased from Yipinchuancheng (Beijing) Technology Co., Ltd.). The positive electrode current collector layer is 20μm thick, and the positive electrode thin film layer is designed to be 500nm thick; the solid electrolyte thin film layer is designed to be 300nm thick, and the negative electrode thin film layer is designed to be 100nm thick. The positive, solid electrolyte, and negative electrode thin films are deposited using vacuum magnetron sputtering.

[0035] A production process for an all-solid-state thin-film battery comprises the following steps: using a positive electrode current collector layer as a positive electrode substrate, sequentially depositing a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector layer using vacuum coating technology; The specific steps include: Step 1: Use a three-target magnetron sputtering device (model VTC-600-3HD) produced by Shenyang Kejing Automation Equipment Co., Ltd. Install the 95Na2S+5C composite cathode target sheet, Na3PO4 target sheet, and Sn target sheet prepared above on the three target heads, set up a copper foil (100mm diameter, 20μm thickness) as a thin film deposition substrate on the sample stage, and set up a mask mold to prepare a sandwich structure with a positive electrode layer / solid electrolyte layer / negative electrode layer without short circuit ( Figure 1 The sample stage was set to rotate at 10 rpm and vacuumed to 1.0×10 -3 After the pressure drops below 4 Pa, adjust the device, introduce argon at a flow rate of 15 ml / min, and control the vacuum value at around 4 Pa.

[0036] Step 2: Slowly adjust the RF power of the composite cathode target to 100W. When the film thickness meter shows a film thickness change rate of 0.1nm / s, open the sample stage shutter to allow the sputtered sodium sulfide and carbon to deposit on the copper foil on the sample stage. When the cumulative deposition thickness reaches 500nm, close the sample stage shutter and reduce the RF power of the composite cathode target to zero. At this point, the cathode thin film layer is formed.

[0037] Step 3: While maintaining a vacuum of approximately 4.0 Pa, introduce nitrogen at a flow rate of 15 ml / min. Slowly adjust the RF power of the sodium phosphate target to 100 W. When the film thickness meter displays a film thickness change rate of 0.1 nm / s, open the sample stage shutter to allow the sputtered sodium phosphate to continue depositing on the copper foil on the sample stage. When the cumulative deposited thickness reaches 300 nm, close the sample stage shutter and reduce the RF power of the sodium phosphate target to zero. At this point, a solid electrolyte thin film layer covering the positive electrode layer is formed.

[0038] Step 4: Turn off the nitrogen. Slowly adjust the RF power of the tin target to 50W. When the film thickness meter shows a rate of change of 0.1nm / s, open the sample stage shutter to allow the sputtered tin to continue depositing on the copper foil on the sample stage. When the cumulative deposited thickness reaches 100nm, close the sample stage shutter and reduce the RF power of the tin target to zero. At this point, a negative electrode thin film layer is formed on top of the solid electrolyte layer.

[0039] Step 5: Cut the vacuum coated copper foil into pieces to obtain Figure 1 Solid-state battery membrane with the structure shown.

[0040] Copper foil is used as the positive electrode current collector layer to lead out the positive electrode tab, and tin layer is used as the negative electrode current collector layer to lead out the negative electrode tab. A small aluminum-plastic film soft-pack battery, i.e., an all-solid-state thin-film battery, is manufactured in a glove box with an argon atmosphere (water content less than 0.1ppm, oxygen content less than 0.1ppm).

[0041] Performance testing: The film thickness is measured using the aforementioned coating equipment's film thickness meter, and the weights of sodium sulfide, sodium phosphate, and tin in the thin-film battery are calculated theoretically. When calculating charge and discharge capacity, Na2S or S is used as the weight of the active charge and discharge material. Energy density is calculated by dividing the battery energy by the deposited weight of all coating materials (positive electrode layer + electrolyte layer + negative electrode layer).

[0042] Use a battery charge and discharge system (SLAN-CT2001A battery tester) to perform charge and discharge tests on small soft-pack batteries.

[0043] The first cycle charging current is 1uA, and the discharge current is 1uA. The test results show that the battery has a first cycle charging capacity of 475mAh / g, a discharge capacity of 428mAh / g, and a coulombic efficiency of 90%.

[0044] The second cycle has a charge current of 1uA and a discharge current of 1uA. The second cycle has a charge capacity of 463mAh / g and a discharge capacity of 445mAh / g, with a coulombic efficiency of 96%.

[0045] The third cycle has a charge current of 1uA and a discharge current of 5uA. The charge capacity of the third cycle is 309mAh / g, the discharge capacity is 293mAh / g, and the coulombic efficiency is 95%.

[0046] The fourth cycle had a charge current of 1 uA and a discharge current of 1 uA. The charge capacity was 451 mAh / g, the discharge capacity was 442 mAh / g, and the coulombic efficiency was 98%. The same charge and discharge conditions were repeated 100 times. The 103rd cycle had a charge capacity of 401 mAh / g, a discharge capacity of 389 mAh / g, and a coulombic efficiency of 97%.

[0047] Compared with the discharge capacity of the second cycle, the discharge capacity retention rate of the third cycle is 92%, indicating that the discharge rate performance is good after the discharge current is increased by 5 times.

[0048] The discharge capacity at the 103rd cycle was maintained at 88% compared to the discharge capacity at the 4th cycle, indicating good cycle performance after 100 cycles of charge and discharge.

[0049] Using the weight of the deposited material in the battery as well as the discharge capacity and average discharge voltage of the second cycle, the energy density of the battery was calculated to be 492Wh / kg.

[0050] Example 2 Example 2 differs from Example 1 only in that the mass percentage of Na2S in the composite cathode target is 75 wt% and the mass percentage of carbon powder is 25 wt%. The vacuum hot pressing conditions are 500°C and 200 MPa, resulting in a 75%Na2S+25%C composite target. The remaining steps and operating conditions are the same as those in Example 1.

[0051] Example 3 Example 3 differs from Example 1 only in that the composite cathode target material contains 40 wt% Na2S and 60 wt% carbon powder. The vacuum hot pressing process is performed at 400°C and 400 MPa, resulting in a 40%Na2S+60%C composite target. The Sn negative electrode thin film layer thickness is adjusted to 50 nm to balance the N / P ratio (the ratio of the theoretical capacity of the negative electrode to the theoretical capacity of the positive electrode). The remaining steps and operating conditions are identical to those of Example 1.

[0052] Example 4 Example 4 differs from Example 1 only in that the raw materials for the composite cathode target are elemental sulfur (purchased from Guangdong Xiaoda Chemical Co., Ltd.) and graphite (purchased from Shenzhen Kejing Zhida Technology Co., Ltd.), with the mass percentage of sulfur being 80 wt% and the mass percentage of graphite powder being 20 wt%. The vacuum hot pressing conditions are a temperature of 100°C and a pressure of 50 MPa, resulting in an 80S+20C composite cathode target. In addition, a NaSn alloy (purchased from Yipinchuancheng (Beijing) Technology Co., Ltd.) is used as the composite anode target. The designed thickness of the cathode thin film layer is 1000 nm, and the designed thickness of the anode thin film layer is adjusted to 500 nm to balance the N / P ratio. Other steps and operating conditions are consistent with those of Example 1.

[0053] Comparative Example 1 Comparative Example 1 differs only in that the mass percentage of Na2S in the composite cathode target is 100 wt%, the mass percentage of carbon powder is 0 wt%, and the vacuum hot pressing conditions are 500°C and 400 MPa, resulting in a 100%Na2S+0C composite target. The remaining steps and operating conditions are the same as those in Example 1.

[0054] Comparative Example 2 Comparative Example 2 differs from Comparative Example 1 only in that the positive electrode thin film layer is produced by simultaneous coating using two targets: a sodium sulfide target (100 Na2S + 0C, produced in Comparative Example 1) and a graphite target (100C, φ50×3mm, purchased from Yipinchuancheng (Beijing) Technology Co., Ltd.). In step 2 of Comparative Example 1 (i.e., step 2 of Example 1), the RF power of the sodium sulfide target and the graphite target were simultaneously adjusted to 100W for coating to form the positive electrode thin film layer. The ratio of sodium sulfide to graphite targets was 1:1. The remaining steps and operating conditions were consistent with those of Comparative Example 1.

[0055] The batteries obtained in Examples 1-4 and Comparative Examples 1-2 were subjected to cycle performance tests and rate performance tests. The results are shown in Table 1.

[0056] Table 1 Battery performance test results of Examples 1 to 4 and Comparative Examples 1 to 2

[0057] It can be seen from Table 1 in combination with the embodiments and comparative examples that the all-solid-state thin-film battery prepared by the technical solution provided by the present invention is superior to the comparative example in terms of cycle performance and battery rate performance, and the battery has high energy density and strong high and low temperature resistance. It eliminates the annealing step, simplifies the coating process, and is convenient for mass production.

[0058] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite target material for positive electrode of all-solid-state thin film battery, characterized in that: The composite target material raw material includes a carbon source and a sulfur source, wherein the carbon source is a conductive carbon source and the sulfur source is a sulfur-containing electrode material.

2. The all-solid-state thin-film battery cathode composite target according to claim 1, characterized in that: The sulfur-containing electrode material includes one or a combination of sulfur and a compound containing sulfur and a metal element.

3. The all-solid-state thin-film battery cathode composite target according to claim 2, characterized in that: The compound containing both sulfur and metal elements is one or a combination of two or more of sodium sulfide, lithium sulfide, magnesium sulfide, aluminum sulfide, iron sulfide, and copper sulfide; and the sodium sulfide is one or a combination of two of sodium sulfide and sodium polysulfide.

4. The all-solid-state thin film battery cathode composite target according to claim 1, characterized in that: The carbon source is one or a combination of two or more of graphite, graphene and amorphous carbon.

5. A process for producing a composite target material for a positive electrode of an all-solid-state thin-film battery according to claim 1, characterized in that: The method comprises the following steps: mixing a carbon source and a sulfur source, grinding them uniformly mechanically and then pressing them, and sintering them by vacuum hot pressing to obtain a positive electrode composite target material.

6. The production process of the all-solid-state thin film battery cathode composite target material according to claim 5, characterized in that: The mass percentage of the sulfur source is 50wt%-98wt%, and the mass percentage of the carbon source is 2wt%-50wt%; the mechanical grinding is ball milling, sand milling or vibration milling.

7. The production process of the all-solid-state thin film battery cathode composite target material according to claim 6, characterized in that: The vacuum hot pressing method is performed under the following conditions: a temperature of 100° C. to 600° C. and a pressure of 10 MPa to 500 MPa.

8. A production process for an all-solid-state thin-film battery, characterized in that: The method comprises the following steps: using the positive electrode current collector layer as the positive electrode substrate, sequentially depositing the positive electrode layer, the solid electrolyte layer, the negative electrode layer and the negative electrode current collector layer by vacuum coating technology, wherein the target material of the positive electrode layer is the positive electrode composite target material of the all-solid-state thin film battery as described in claims 1 to 4.

9. The production process of the all-solid-state thin-film battery according to claim 8, characterized in that: The vacuum coating technology is one of vacuum evaporation coating and magnetron sputtering coating or a combination of the two.

10. An all-solid-state thin-film battery produced by the production process of an all-solid-state thin-film battery according to any one of claims 8 to 9.

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