Lithium secondary battery, and method for manufacturing a lithium secondary battery
A transparent and flexible lithium secondary battery design with multi-layered conductive films addresses the lack of transparency and flexibility in existing batteries, offering enhanced design and performance.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NIPPON TELEGRAPH & TELEPHONE CORP
- Filing Date
- 2022-11-17
- Publication Date
- 2026-07-01
AI Technical Summary
Existing lithium-ion batteries lack transparency to visible light and flexibility, limiting their design and application possibilities.
A lithium secondary battery design featuring transparent and flexible positive and negative electrodes, coated with multi-layered transparent conductive films of ITO and FTO, and sealed with a transparent electrolyte, allowing for visible light transmission and flexibility.
The battery achieves transparency and flexibility, enhancing design possibilities and performance through improved charge/discharge capabilities.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a lithium secondary battery and a method for manufacturing the same.
Background Art
[0002] A lithium secondary battery is a secondary battery that charges and discharges by the movement of lithium ions between a positive electrode and a negative electrode. The electrode reaction of a lithium secondary battery is an insertion / desorption reaction of lithium ions. The insertion / desorption reaction of lithium ions is a reaction in which lithium ions are inserted into or desorbed from a compound by electrochemically oxidizing or reducing the substances used for the positive electrode and the negative electrode.
[0003] Since lithium secondary batteries have a higher energy density than other batteries, they are used in various applications such as electronic devices, automotive power sources, and power storage. In addition, research and development on electrode materials and electrolyte materials are being advanced for performance improvement and cost reduction. Furthermore, with the development of smartphone terminals and IoT (Internet of Things) devices, they have attracted great attention as mobile power sources, and flexibility and designability of the battery itself are also required as power sources for transparent displays and ultra-thin displays.
[0004] Non-Patent Document 1 discloses a lithium secondary battery that can be bent with a thickness on the order of μm by forming a solid electrolyte of LiPoN (a transparent amorphous film in which oxygen in Li3PO4 is partially substituted with nitrogen to exhibit lithium ion conductivity), a negative electrode of metallic lithium, and a negative electrode current collector of Cu in this order on a positive electrode film of LiCoO2 formed on a Pt / Ti current collector film by an RF (Radio Frequency) sputtering method or a vacuum evaporation method.
Prior Art Documents
Non-Patent Documents
[0005]
Non-Patent Document 1
[0006] Thin, flexible lithium-ion batteries are being considered. However, no lithium-ion batteries that also possess visible light transmittance have been found in Non-Patent Document 1 or in commercially available batteries.
[0007] This disclosure is made in view of the above circumstances, and the purpose of this disclosure is to provide a technology that can provide a lithium secondary battery that is transparent to visible light and has excellent flexibility. [Means for solving the problem]
[0008] A lithium secondary battery according to one aspect of the present disclosure comprises: a transparent and flexible positive electrode film and a negative electrode film; a transparent conductive film for the positive electrode coated on the surface of the positive electrode film; a transparent conductive film for the negative electrode coated on the surface of the negative electrode film; a positive electrode formed as a thin film on the surface of the transparent conductive film for the positive electrode, which is transparent to visible light, flexible, and capable of inserting and removing lithium ions; a negative electrode formed as a thin film on the surface of the transparent conductive film for the negative electrode, which is transparent to visible light, flexible, and composed of metallic lithium, a metal capable of forming an alloy with lithium, or a substance capable of inserting and removing lithium ions; a transparent electrolyte disposed between the positive electrode and the negative electrode and having lithium ion conductivity; and a transparent sealing means for sealing the positive electrode film, the transparent conductive film for the positive electrode, the positive electrode, the electrolyte, the negative electrode, the transparent conductive film for the negative electrode, and the negative electrode film, wherein the transparent conductive film for the positive electrode or the transparent conductive film for the negative electrode is ITO (Indium Tin A transparent conductive film in which an Oxide layer and an FTO (Fluorine-doped Tin Oxide) layer are laminated. , Using a gas containing 30% to 50% oxygen within the container The ITO layer and the FTO layer are coated It is being done.
[0009] A method for manufacturing a lithium secondary battery according to one aspect of the present disclosure is a method for manufacturing a lithium secondary battery comprising: a first step of coating the surface of a transparent and flexible positive electrode film with a transparent conductive film for the positive electrode; a second step of forming a thin film of a positive electrode on the surface of the transparent conductive film for the positive electrode, which is transparent, flexible, and capable of inserting and removing lithium ions; a third step of coating the surface of a transparent and flexible negative electrode film with a transparent conductive film for the negative electrode; and a thin film of a positive electrode on the surface of the transparent conductive film for the negative electrode, which is transparent, flexible, The process involves a fourth step of forming a thin film of a negative electrode composed of metallic lithium, a metal capable of forming an alloy with lithium, or a material capable of inserting and removing lithium ions; a fifth step of placing a transparent electrolyte having lithium ion conductivity between the positive electrode and the negative electrode; and a sixth step of sealing the positive electrode film, the transparent conductive film for the positive electrode, the positive electrode, the electrolyte, the negative electrode, the transparent conductive film for the negative electrode, and the negative electrode film with a transparent sealing means, wherein the transparent conductive film for the positive electrode or the transparent conductive film for the negative electrode is a transparent conductive film in which an ITO (Indium Tin Oxide) layer and an FTO (Fluorine doped Tin Oxide) layer are laminated, and in the first or third step, the ITO layer and the FTO layer are laminated using a gas containing oxygen at a ratio of 30% to 50% in the gas. coating do. [Effects of the Invention]
[0010] According to this disclosure, it is possible to provide a lithium secondary battery that is transparent to visible light and has excellent flexibility. [Brief explanation of the drawing]
[0011] [Figure 1] Figure 1 shows an example of the configuration of a lithium secondary battery. [Figure 2] Figure 2 shows the transmittance of a lithium secondary battery. [Figure 3] Figure 3 shows the initial charge-discharge curve. [Figure 4] Figure 4 is a reference diagram used when explaining battery performance. [Modes for carrying out the invention]
[0012] Embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals and their descriptions are omitted. This disclosure is not limited to the following and may be modified as appropriate without changing the spirit and scope of this disclosure.
[0013] [Summary of this invention] If we can create a thin, flexible, and transparent lithium-ion secondary battery, it will greatly expand the design possibilities and range of applications for various devices.
[0014] Therefore, in this embodiment, a lithium secondary battery is provided comprising a positive electrode containing a material capable of inserting and removing lithium ions, a negative electrode composed of one of metallic lithium, a metal capable of forming an alloy with lithium, or a material capable of inserting and removing lithium ions, and an electrolyte having lithium ion conductivity. The positive and negative electrodes are formed as thin films on a substrate coated with a transparent conductive film such as ITO (Indium Tin Oxide) on a transparent and flexible film, a transparent electrolyte is used as the electrolyte, and the entire structure is sealed using a transparent adhesive or sealant. This makes it possible to provide a lithium secondary battery that is transparent to visible light and has excellent flexibility.
[0015] Furthermore, in this embodiment, a different type of transparent conductive film, such as FTO (Fluorine-doped Tin Oxide), is laminated on an ITO thin film. This makes it possible to provide a lithium secondary battery that has visible light transmittance, excellent flexibility, and superior charge / discharge performance.
[0016] Furthermore, in this embodiment, oxygen is mixed with the gas used during the deposition of a multi-layered transparent conductive film. This makes it possible to provide a lithium secondary battery with superior performance.
[0017] In addition, in this embodiment, the mixing ratio of oxygen is set to 30 to 50% of the entire gas. This makes it possible to provide an even more excellent lithium secondary battery.
[0018] [Configuration of Lithium Secondary Battery] The lithium secondary battery according to this embodiment includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode is made of a material containing a substance capable of inserting and extracting lithium ions. The negative electrode is made of any one of metallic lithium, a metal capable of forming an alloy with lithium, and a substance capable of inserting and extracting lithium ions. The electrolyte is made of a material having lithium ion conductivity.
[0019] A transparent conductive film such as ITO is formed on the entire surface of a flexible film with visible light transmittance such as PET (Polyethylene terephthalate). The positive electrode is fabricated by forming a flexible substance capable of inserting and extracting lithium ions and having visible light transmittance on the transparent conductive film with a predetermined thickness. Those film-forming methods may be any film-forming methods such as sputtering and vapor deposition. This method for fabricating the positive electrode is an example and is not limited to this method.
[0020] The negative electrode is fabricated in the same manner as the positive electrode. Specifically, the negative electrode is fabricated by forming, for example, a flexible substance capable of inserting and extracting lithium ions and having visible light transmittance on a transparent conductive film such as ITO formed on the entire surface of a flexible film with visible light transmittance such as PET with a predetermined thickness. This method for fabricating the negative electrode is also an example.
[0021] Any electrolyte can be used as long as it is a substance having lithium ion conductivity and visible light transmittance. For example, the electrolyte is realized using an organic electrolyte solution containing lithium ions, an aqueous electrolyte solution, or a gel polymer. In addition, even a solid electrolyte such as a solid electrolyte containing lithium ions or a polymer electrolyte can be used as long as it transmits visible light. It is preferable that the electrolyte is a substance having no electronic conductivity.
[0022] Figure 1 is a diagram showing an example of the configuration of a lithium secondary battery 1 according to this embodiment. Figure 1(a) is a side cross-sectional view of the lithium secondary battery 1. Figure 1(b) is a top view of the lithium secondary battery 1. The lithium secondary battery 1 comprises a positive electrode 11 and a negative electrode 12 arranged opposite each other, and an electrolyte 13 arranged between the positive electrode 11 and the negative electrode 12 in contact with both electrodes.
[0023] The constituent materials and manufacturing methods for the positive electrode 11, negative electrode 12, and electrolyte 13 are as described above.
[0024] The positive electrode 11 is made of a material that allows for the insertion and removal of lithium ions, is transparent to visible light, and is flexible. The positive electrode 11 is formed as a thin film on the surface of the transparent conductive film 16 for the positive electrode.
[0025] The negative electrode 12 is composed of one of the following materials: metallic lithium, a metal capable of forming an alloy with lithium, or a material capable of inserting and removing lithium ions. It is made of a flexible material that is transparent to visible light. The negative electrode 12 is formed as a thin film on the surface of the transparent conductive film 17 for the negative electrode.
[0026] The electrolyte 13 is composed of a transparent material that is lithium-ion conductive and transparent to visible light. The electrolyte 13 is placed between the positive electrode 11 and the negative electrode 12. When an organic electrolyte or an aqueous electrolyte is used as the electrolyte 13, a separator may be placed between the positive electrode 11 and the negative electrode 12 in contact with both electrodes, and the separator may be impregnated with these electrolytes. Alternatively, the organic electrolyte or aqueous electrolyte may be impregnated with a polymer electrolyte or the like. Furthermore, when a solid electrolyte such as a solid electrolyte or a polymer electrolyte is used as the electrolyte 13, both electrodes, the positive electrode 11 and the negative electrode 12, should be placed in contact with the solid electrolyte.
[0027] Furthermore, as shown in Figure 1, the lithium secondary battery 1 comprises a visible light-transmitting, flexible, transparent positive electrode film 14, a visible light-transmitting, flexible, transparent negative electrode film 15, a transparent conductive film 16 for the positive electrode coated on the surface of the positive electrode film 14, a transparent conductive film 17 for the negative electrode coated on the surface of the negative electrode film 15, and a visible light-transmitting, flexible, transparent laminate film 18. The laminate film 18 is an example of a sealing means. The sealing means includes a transparent adhesive, a transparent sealant, and the like.
[0028] [Manufacturing method for lithium secondary batteries] First, a transparent conductive film 16 for the positive electrode is coated over the entire surface of one side of the transparent and flexible positive electrode film 14 (first step).
[0029] Next, a thin film of a positive electrode 11 capable of inserting and removing lithium ions is formed on the exposed surface of the transparent conductive film 16 for the positive electrode (second step).
[0030] Next, a transparent conductive film 17 for the negative electrode is coated over the entire surface of one side of the transparent and flexible negative electrode film 15 (third step).
[0031] Next, a thin film of a negative electrode 12, which allows for the insertion and removal of lithium ions, is formed on the exposed surface of the transparent conductive film 17 for the negative electrode (fourth step).
[0032] Next, the exposed surface of the positive electrode 11 and the exposed surface of the negative electrode 12 are placed facing each other, and a transparent electrolyte 13, which is composed of a polymer electrolyte impregnated with, for example, an organic electrolyte, is placed between them (fifth step).
[0033] Finally, the entire assembly is sandwiched between a pair of transparent laminate films 18 from both sides, the edges are bonded using a transparent adhesive or sealant, and after vacuum drying, it is heat-pressed (step 6).
[0034] This allows the lithium secondary battery 1 to be prepared. At this time, a portion of the transparent conductive film 16 for the positive electrode and the film 14 on the positive electrode side are exposed to the outside of the laminate film 18 to form the electrode terminal 19a for the positive electrode. Similarly, a portion of the transparent conductive film 17 for the negative electrode and the film 15 on the negative electrode side are exposed to the outside of the laminate film 18 to form the electrode terminal 19b for the negative electrode.
[0035] Thus, the lithium secondary battery 1 according to this embodiment is made of a flexible material in which each component is formed as a thin film and has visible light transmittance, so it can transmit visible light and can be charged and discharged even when bent.
[0036] Furthermore, in this embodiment, in the first and third steps, a transparent conductive film 16 for the positive electrode and a transparent conductive film 17 for the negative electrode are formed by laminating multiple transparent conductive films of different materials. A mixed gas containing oxygen is used to form these multiple transparent conductive films. The oxygen content in the mixed gas is preferably, for example, 30% to 50%. This improves the charge-discharge performance. The effects of this will be described later.
[0037] The above-described method for manufacturing a lithium secondary battery is merely an example. For instance, the third and fourth steps may be performed before or simultaneously with the first and second steps.
[0038] [Example 1] In Example 1, the lithium secondary battery 1 according to this embodiment was manufactured using the following procedure.
[0039] (Method for fabricating glass substrates with transparent conductive film) A glass substrate measuring 100 mm in length, 100 mm in width, and 2 mm in thickness was used as the positive electrode film 14 and the negative electrode film 15. A 50 nm thin film of ITO was deposited on the surface of the glass substrate by RF sputtering. The sputtering was performed using an ITO (5 wt% SnO2) target with 18 sccm of argon and 2 sccm of oxygen flowing through it, at an RF output of 50 W. Subsequently, a 50 nm thin film of FTO was deposited on the ITO thin film deposited in the previous step by sputtering using an FTO target with 18 sccm of argon and 2 sccm of oxygen flowing through it, at an RF output of 50 W. This created a two-layer thin film of ITO / FTO on the glass substrate. These two-layer thin films are the transparent conductive film 16 for the positive electrode and the transparent conductive film 17 for the negative electrode.
[0040] (Method for preparing electrolytes) Electrolyte 13 was prepared using the following procedure: Polyvinylidene fluoride (PVdF) powder as a binder, an organic electrolyte prepared by dissolving 1 mol / L of lithium bistrifluoromethanesulfonyliimide (LiTFSI) as a lithium salt in propylene carbonate (PC), and tetrahydrofuran (THF) as a dispersion medium were mixed in a weight ratio of 4:6:10. The mixed solution was stirred at 60°C for 1 hour in dry air with a dew point of -50°C or lower. After stirring, 50 ml of the solution was poured into a 200Φ petri dish and vacuum-dried at 50°C for 12 hours to produce a transparent film with a thickness of 0.1 mm, which was then molded to a size of 90 mm x 100 mm.
[0041] (Method for manufacturing the positive electrode) The positive electrode 11 was fabricated using the following procedure. A 100 nm thick film of lithium cobalt phosphate (LiCoPO4) was deposited on one side of the electrolyte 13 using RF sputtering. Sputtering was performed using a LiCoPO4 ceramic target with 15 sccm of argon and 5 sccm of oxygen, at an RF output of 100 W.
[0042] (Method for fabricating the negative electrode) The negative electrode 12 was fabricated using the following procedure. On the other surface (back side) of the electrolyte 13, lithium titanate (Li4Ti5O) was applied by RF sputtering. 12A film was deposited to a thickness of 150 nm using ) as the negative electrode. Sputtering was performed using Li4Ti5O 12 Using a ceramic target, the experiment was conducted with 15 sccm of argon and 5 sccm of oxygen, at an RF output of 100 W.
[0043] (Method for manufacturing lithium secondary batteries) Lithium secondary battery 1 was manufactured using the following procedure. Two transparent conductive film-coated glass substrates were prepared and placed facing each other so that they overlapped to a size of 90 mm in length and 100 mm in width. The electrolyte 13 on which the positive electrode 11 and negative electrode 12 were formed was sandwiched between them, and a pair of laminate films 18 were placed on both outer sides to seal the edges with adhesive. Before the adhesive hardened, the substrate was placed in a vacuum dryer and vacuum dried, after which the adhesive was allowed to solidify.
[0044] (Transmittance measurement of lithium secondary batteries) The transmittance of lithium secondary battery 1 in the visible light region was measured using a commercially available light meter.
[0045] (Performance evaluation of lithium-ion batteries) A commercially available charge / discharge measurement system was used to perform charge / discharge tests on lithium secondary battery 1. The current density per unit area of the positive and negative electrodes was set to 1 μA / cm². 2 The charging termination voltage was set to 3.3V and the discharging termination voltage to 2.0V, and the charge / discharge test was performed in a constant temperature chamber at 25°C (under normal atmospheric conditions).
[0046] [Example 2] (Method for fabricating glass substrates with transparent conductive film) A 50nm ITO film was deposited on the surface of a glass substrate of the same size as in Example 1 using RF sputtering. The sputtering was performed using an ITO (5wt%SnO2) target with 14 sccm of argon and 6 sccm of oxygen flowing through it, at an RF output of 50W. Subsequently, a 50nm FTO film was deposited on the ITO thin film deposited in the previous step using an FTO target with 14 sccm of argon and 6 sccm of oxygen flowing through it, at an RF output of 50W. This resulted in the fabrication of a two-layer ITO / FTO thin film on the glass substrate.
[0047] (Methods for preparing electrolytes, etc.) The methods for preparing the electrolyte, the positive electrode, the negative electrode, the lithium secondary battery, the transmittance measurement of the lithium secondary battery, and the performance evaluation of the lithium secondary battery are the same as in Example 1. The same applies to Examples 3 to 4, which will be described later.
[0048] [Example 3] (Method for fabricating glass substrates with transparent conductive film) A 50nm ITO film was deposited on the surface of a glass substrate of the same size as in Example 1 using RF sputtering. The sputtering was performed using an ITO (5wt%SnO2) target with 10 sccm of argon and 10 sccm of oxygen flowing through it, at an RF output of 50W. Subsequently, a 50nm FTO film was deposited on the ITO thin film deposited in the previous step using an FTO target with 10 sccm of argon and 10 sccm of oxygen flowing through it, at an RF output of 50W. This resulted in the fabrication of a two-layer ITO / FTO thin film on the glass substrate.
[0049] [Example 4] (Method for fabricating glass substrates with transparent conductive film) A 50nm ITO film was deposited on the surface of a glass substrate of the same size as in Example 1 using RF sputtering. The sputtering was performed using an ITO (5wt%SnO2) target with 6 sccm of argon and 14 sccm of oxygen flowing through it at a 50W RF output. Subsequently, a 50nm FTO film was deposited on the ITO thin film deposited in the previous step using an FTO target with 6 sccm of argon and 14 sccm of oxygen flowing through it at a 50W RF output. This resulted in the fabrication of a two-layer ITO / FTO thin film on the glass substrate.
[0050] [Comparative Example] A lithium-ion secondary battery was fabricated for comparison.
[0051] (Method for fabricating glass substrates with transparent conductive film) A 100 nm thin film of ITO was deposited on the surface of a glass substrate of the same size as in Example 1 using RF sputtering. The sputtering was performed using an ITO (5 wt% SnO2) target with argon flowing at 20 sccm and an RF output of 50 W. This resulted in the fabrication of a single-layer thin film of ITO on the glass substrate.
[0052] (Methods for preparing electrolytes, etc.) The methods for preparing the electrolyte, the positive electrode, the negative electrode, the lithium secondary battery, the transmittance measurement of the lithium secondary battery, and the performance evaluation of the lithium secondary battery are the same as in Example 1.
[0053] Finally, Table 1 summarizes the fabrication conditions for each transparent conductive film produced in Examples 1-4 and the Comparative Example.
[0054] [Table 1]
[0055] [Comparative Study of Examples and Comparative Examples] First, we will examine the visible light transmittance of lithium secondary battery 1.
[0056] Figure 2 shows the results of the transmittance measurement in the visible light region for lithium secondary battery 1 fabricated in Example 1. It shows a transmittance of 60% or more in the visible light region with a wavelength of 400 nm or higher. From these measurement results, it can be seen that lithium secondary battery 1 of Example 1 is capable of sufficiently transmitting visible light. Table 2 summarizes the average transmittance of each lithium secondary battery 1 fabricated in each example and comparative example.
[0057] [Table 2]
[0058] Table 2 shows that Examples 2 to 4 can also transmit visible light sufficiently.
[0059] Next, we will examine the charge and discharge results of lithium secondary battery 1.
[0060] Figure 3 shows the initial charge-discharge curves for Example 1 and the Comparative Example. The initial charge-discharge curve for Example 2, which showed the highest charge-discharge performance, is also included. Example 1 showed a capacity of approximately 0.100 mAh and an average discharge voltage of approximately 2.65 V. On the other hand, the Comparative Example showed a capacity of approximately 0.073 mAh and an average discharge voltage of approximately 2.6 V. Table 3 summarizes the initial discharge capacity and the discharge capacity after 20 cycles for each lithium secondary battery 1 produced in each example and comparative example.
[0061] [Table 3]
[0062] Examples 1 to 4 had higher charge / discharge capacity and discharge voltage, and lower charge voltage than the comparative example. Conversely, the comparative example had lower charge / discharge capacity and discharge voltage, and higher charge voltage than Examples 1 to 4.
[0063] This is because, in Examples 1 to 4, as shown in the side cross-sectional view in Figure 4(a), a two-layer thin film of ITO / FTO is formed on the glass substrate. Therefore, even if a crack occurs in the two-layer thin film when the lithium secondary battery 1 is bent, the network of the ITO / FTO current collection path is maintained.
[0064] On the other hand, in the comparative example, as shown in the side cross-sectional view in Figure 4(b), since the ITO thin film is a single layer, if a crack occurs in the ITO thin film, part of the ITO current collection path is severed, and that isolated part becomes inactive, which is thought to be the cause of the decrease in capacity and increase in current collection resistance.
[0065] Furthermore, Tables 1 and 3 show that mixing oxygen during the deposition of the transparent conductive film improves performance compared to the comparative example where oxygen is not mixed. It can also be seen that Example 2, in which a slightly larger amount of oxygen was mixed, showed improved performance compared to Example 1. This is thought to be because mixing an appropriate amount of oxygen during the deposition of the transparent conductive film increased the conductivity of the transparent conductive film and reduced the resistance of the electrodes. Moreover, comparing the discharge capacities of Examples 2 and 3 with those of Example 4, it can be seen that higher performance is observed when the proportion of oxygen mixed is between 30% and 50%, as in Examples 2 and 3.
[0066] [Effects of this embodiment] According to this embodiment, the lithium secondary battery 1 comprises a transparent and flexible positive electrode film 14 and a negative electrode film 15, a transparent conductive film 16 for the positive electrode coated on the surface of the positive electrode film, a transparent conductive film 17 for the negative electrode coated on the surface of the negative electrode film, a positive electrode 11 formed as a thin film on the surface of the transparent conductive film for the positive electrode and capable of inserting and removing lithium ions, a negative electrode 12 formed as a thin film on the surface of the transparent conductive film for the negative electrode and composed of one of metallic lithium, a metal capable of forming an alloy with lithium, or a substance capable of inserting and removing lithium ions, a transparent electrolyte 13 disposed between the positive electrode and the negative electrode and having lithium ion conductivity, and a transparent sealing means 18 that seals the positive electrode film, the transparent conductive film for the positive electrode, the positive electrode, the electrolyte, the negative electrode, the transparent conductive film for the negative electrode, and the negative electrode film. Thus, it is possible to provide a lithium secondary battery that is transparent to visible light and has excellent flexibility.
[0067] Furthermore, according to this embodiment, since the transparent conductive film 16 for the positive electrode or the transparent conductive film 17 for the negative electrode is a multi-layered transparent conductive film in which the material types of each layer are different from each other, it is possible to provide a lithium secondary battery that has visible light transmittance, excellent flexibility, and excellent charge / discharge performance.
[0068] Furthermore, according to this embodiment, since the multi-layered transparent conductive film is a transparent conductive film coated using an oxygen-containing gas, it is possible to provide a lithium secondary battery with superior performance.
[0069] Furthermore, according to this embodiment, since the proportion of oxygen in the gas is 30% to 50%, it becomes possible to provide an even better lithium secondary battery.
[0070] [Industrial applicability] The lithium secondary battery 1 according to this embodiment can be used as a power source for various electronic devices. [Explanation of Symbols]
[0071] 1. Lithium-ion rechargeable battery 11 Positive electrode 12 Negative electrode 13 Electrolytes 14. Film on the positive side 15. Film on the negative electrode side 16 Transparent conductive film for positive electrode 17 Transparent conductive film for negative electrode 18 Laminating film 19a Positive electrode terminal 19b Electrode terminal for the negative electrode
Claims
1. A transparent and flexible positive electrode film and a negative electrode film, A transparent conductive film for the positive electrode is coated on the surface of the positive electrode film, A transparent conductive film for the negative electrode is coated on the surface of the negative electrode film, A thin film is formed on the surface of the transparent conductive film for the positive electrode, and the positive electrode is transparent to visible light, flexible, and capable of inserting and removing lithium ions. A thin film is formed on the surface of the transparent conductive film for the negative electrode, and the negative electrode is composed of one of the following: metallic lithium, a metal capable of forming an alloy with lithium, or a material capable of inserting and removing lithium ions. A transparent electrolyte having lithium-ion conductivity is disposed between the positive electrode and the negative electrode, The device comprises the positive electrode film, the transparent conductive film for the positive electrode, the positive electrode, the electrolyte, the negative electrode, the transparent conductive film for the negative electrode, and a transparent sealing means for sealing the negative electrode film. The transparent conductive film for the positive electrode or the transparent conductive film for the negative electrode is A lithium secondary battery comprising a transparent conductive film in which an ITO (Indium Tin Oxide) layer and an FTO (Fluorine Doped Tin Oxide) layer are laminated, wherein the ITO layer and the FTO layer are coated using a gas containing oxygen at a concentration of 30% to 50%.
2. In a method for manufacturing lithium secondary batteries, The first step involves coating the surface of a transparent and flexible positive electrode film with a transparent conductive film for the positive electrode, A second step involves forming a thin film of a positive electrode on the surface of the transparent conductive film for the positive electrode, which is transparent to visible light, flexible, and capable of inserting and removing lithium ions. A third step involves coating the surface of a transparent and flexible negative electrode film with a transparent conductive film for the negative electrode, A fourth step is to form a thin negative electrode film on the surface of the transparent conductive film for the negative electrode, which is transparent to visible light, flexible, and composed of one of the following: metallic lithium, a metal capable of forming an alloy with lithium, or a material capable of inserting and removing lithium ions. A fifth step involves placing a transparent electrolyte having lithium-ion conductivity between the positive electrode and the negative electrode, A sixth step is performed in which the positive electrode film, the transparent conductive film for the positive electrode, the positive electrode, the electrolyte, the negative electrode, the transparent conductive film for the negative electrode, and the negative electrode film are sealed together with a transparent sealing means. The transparent conductive film for the positive electrode or the transparent conductive film for the negative electrode is A transparent conductive film in which an ITO (Indium Tin Oxide) layer and an FTO (Fluorine Doped Tin Oxide) layer are laminated, In the first or third step, A method for manufacturing a lithium secondary battery, comprising coating the ITO layer and the FTO layer with a gas containing 30% to 50% oxygen in the gas.