All-solid lithium battery

Abstract

To provide an all-solid lithium battery using carbon nanowalls (CNWs) as anodes.SOLUTION: An all-solid lithium battery is constructed by combining an anode 4, on which carbon nanowalls have been grown after removing a copper oxide from the surface of an electrolytic copper foil, with a solid electrolyte 5 and a cathode 3. By synthesizing the carbon nanowalls (CNWs) on the electrolytic copper foil and using them as the anode, it is expected that the combination of high surface area and electrical conductivity contributes to improving the performance and efficiency of the electrolytic copper foil anode. Specifically, in energy storage devices such as lithium-ion batteries and supercapacitors, carbon nanowalls (CNWs) can provide a high reactive surface area and play a role in promoting efficient electrochemical reactions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an all-solid-state lithium battery. [Background technology]

[0002] Lithium-ion batteries are used in a wide range of applications, from electronic devices such as mobile phones and laptops to electric vehicles. However, improper use, deterioration, heat and other factors can combine to cause lithium-ion batteries to burst or explode. It is important to use an appropriate charger, avoid overcharging and over-discharging, not expose batteries to excessively high temperatures, and handle them carefully to prevent physical damage.

[0003] Because solid-state batteries do not use liquid electrolytes, there is a low risk of leakage or thermal runaway, they have a high energy density, can store more energy in the same size battery, and can operate stably over a wide temperature range, making it easier to maintain performance even under extreme temperature conditions. They are said to have high charging and discharging efficiency and little loss of electrical energy, and are relatively easy to make flexible and thin, allowing for a high degree of design freedom, which is expected to lead to the realization of lightweight and compact devices for specific applications. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-239369 A Summary of the Invention [Problem to be solved by the invention]

[0005] All-solid-state lithium batteries are a next-generation battery technology that has the potential to offer higher energy density, safety, and cycle life than conventional lithium-ion batteries, and their structure is an important area of ​​research because the anode material has a significant impact on battery performance.

[0006] According to the inventor's research, carbon nanowalls (CNWs) are a type of nanocarbon material, and their fine structure and high specific surface area make them promising anode materials for all-solid-state batteries. Developed as part of nanotechnology, they are nanocarbon-based materials that have a three-dimensional wall structure rather than a planar structure like graphene, have high electrical conductivity, and are used in a variety of application fields.

[0007] In lithium-ion batteries that use liquid electrolytes, the liquid electrolyte is relatively free and easy for ions to move, so even if the gap between carbon nanowalls (CNWs) is 150 nm, the lithium ions in the electrolyte can act as ion conductors relatively easily and move to the CNWs.

[0008] In contrast, in solid-state batteries that use solid electrolytes, the movement of ions is more restricted in solid electrolytes than in liquid electrolytes. Solid electrolytes generally tend to have lower ionic conductivity than liquid electrolytes, and when ions move through a solid electrolyte, the movement of ions becomes more difficult if there are narrower gaps. Therefore, limiting the gaps between carbon nanowalls (CNWs) to a distance of 1 to 2 μm is an advantageous condition for solid-state batteries. [Means for solving the problem]

[0009] In view of the above circumstances, the present invention proposes an all-solid-state lithium battery characterized in that a positive electrode made of a lithium compound and a negative electrode made of carbon nanowalls grown on the surface of a substrate are provided, and a solid electrolyte is provided between the positive electrode and the negative electrode.

[0010] Here, as the lithium compound, for example, lithium cobalt oxide (LiCoO2) can be used.

[0011] As the solid electrolyte, for example, lithium oxide ceramics (LiPON) and lithium sulfide ceramics (Li2S, SiS2) can be used.

[0012] Furthermore, in the present invention, conventionally used substrates such as stainless steel (SUS), copper plate, and electrolytic copper foil can be used as the substrate.

[0013] Although SUS (stainless steel) has properties such as corrosion resistance and mechanical strength and is widely used in the chemical industry and construction, it has low conductivity and is not suitable for transmitting electrical signals, so there are limitations to its electrical applications.

[0014] In contrast, electrolytic copper foil has extremely high electrical conductivity, which allows current to flow efficiently and reduces energy loss, making it a material well suited to transmitting electrical signals with high efficiency.

[0015] In the present invention, therefore, the inventors have focused on using electrolytic copper foil as a substrate, on the surface of which carbon nanowalls are grown, to produce a negative electrode.

[0016] However, when electrolytic copper foil is used, the copper oxide layer on the surface reduces adhesion to carbon nanowalls (CNWs), which may cause them to peel off easily.

[0017] In the present invention, the carbon nanowalls are grown after the copper oxide layer on the surface is removed.

[0018] To remove the copper oxide layer on the surface, an alkaline solution such as sodium hydroxide or an acidic solution such as dilute hydrochloric acid is used. Effect of the Invention

[0019] In the present invention, the negative electrode of the all-solid-state battery is composed of carbon nanowall layers grown in various directions, and the use of a negative electrode with such a new structure provides the all-solid-state battery with advantages such as high performance, long life, and improved safety.

[0020] Carbon nanowalls (CNWs) are carbon nanostructures with a high specific surface area, which increases the reactive surface area and therefore can promote electrochemical reactions and store energy.

[0021] Furthermore, electrolytic copper foil is a highly conductive material used in electrical circuits and electronic devices, and by synthesizing carbon nanowalls (CNWs) on electrolytic copper foil and using it as the negative electrode as in the present invention, it is expected that a high surface area and electrical conductivity will be combined, contributing to improving the performance and efficiency of the negative electrode of the electrolytic copper foil. Specifically, in energy storage devices such as lithium ion batteries and supercapacitors, carbon nanowalls (CNWs) can provide a high reaction surface area and play a role in promoting efficient electrochemical reactions. [Brief description of the drawings]

[0022] [Figure 1] Image of an all-solid-state lithium-ion battery [Diagram 2] A diagram showing the process of growing carbon nanowalls after removing the copper oxide layer on the surface of electrolytic copper foil. [Diagram 3] Image of cylindrical all-solid-state lithium battery [Figure 4] SEM image of carbon nanowall [Diagram 5] TEM image of carbon nanowalls [Figure 6] Raman spectrum of carbon nanowalls DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An all-solid-state lithium battery composed of a negative electrode 4, on which carbon nanowalls have been grown after removing the copper oxide from the surface of electrolytic copper foil, combined with a solid electrolyte 5 and a positive electrode 3.

[0024] The present invention will be described based on the illustrated embodiment. Fig. 1 is a diagram for explaining the configuration of the present invention and its operating principle. 3 is a positive electrode made of lithium cobalt oxide (LiCoO2), 4 is an electrolytic copper foil 10 and carbon nanowalls (CNWs) grown on the surface of the foil. S ) 20 is a negative electrode, and 5 is a solid electrolyte made of lithium oxide ceramics (LiPON).

[0025] The negative electrodes (CNWs) 4 contain a lithium compound called LiC6″, and exchange electrons and lithium ions (Li + )8. When charging, lithium ion (Li + )8 moves from the positive electrode 3 to the negative electrode (CNWs) 4 and accumulates in the negative electrode (CNWs) 4. At the same time, electrons supplied from the outside are supplied to the negative electrode, causing a chemical reaction. During discharge, by connecting to an external circuit, electrons flow from the negative electrode (CNWs) 4 to the positive electrode 3, and lithium ions (Li + )8 moves, and an electrochemical reaction occurs in the positive electrode 3. The solid electrolyte 5 between the electrodes allows the movement of lithium ions and provides electronic conductivity. + +e - ⇔LiCoO2; negative electrode (CNWs) is LiC6⇔LiCoO2+e - +6C; the overall reaction proceeds as CoO2+LiC6⇔LiCoO2+6C.

[0026] Incidentally, disposing an aluminum current collector 9 on the positive electrode of an all-solid-state battery is one method for efficiently collecting current at the positive electrode and improving the performance of the entire battery.

[0027] FIG. 2 shows the process of forming a negative electrode by growing carbon nanowalls on the surface of electrolytic copper foil. (1) The electrolytic copper foil 10 is used as a substrate on which vertically oriented multi-layer carbon nanowalls (CNWs) 20 are synthesized. The electrolytic copper foil 10 is washed in advance with acetone and purified water 14 in order using an ultrasonic cleaning device, and the purified water remaining on the electrolytic copper foil 10 is removed with a nitrogen gas gun 15. (2) The washed electrolytic copper foil 10 is placed in a NaOH solution 12, and the surface with copper oxide 11 is etched for about 15 minutes, and the foil is placed in a water tank containing purified water 14 and hung on a stent 16. The foil is dried for about 10 minutes with a nitrogen gas gun 15. (3) Fine particles 17 appear on the surface of the electrolytic copper foil 10, and the foil is placed in a plasma CVD device 18 and flowed in an H2 gas atmosphere for about 15 minutes. (4) The heating temperature of the table supporting the electrolytic copper foil 10 is set to 500°C, and methane gas is flowed. (5) The particles 17 on the surface of the electrolytic copper foil 10 absorb carbon atoms from the methane gas and become copper carbide particles. These are compound particles composed of copper and carbon elements, and in this embodiment, the particles are 300 to 500 o These particles are grown by a reaction in gas (methane) using C. By setting the appropriate reaction gas and conditions, Cu2C particles are formed, as in "2Cu+C→Cu2C". (6) Plasma is a process that makes the gas high-energy and activates the atoms and molecules contained within it. Through plasma processing, carbon atoms begin to enter the Cu2C particles, and as they pass through the Cu2C 19 particles, the carbon atoms bond with each other to form a hexagonal honeycomb structure, which spreads two-dimensionally, and carbon nanowalls grow in a disordered state in the vertical direction.

[0028] (Cylindrical solid-state battery) Unlike conventional batteries that use liquid electrolytes, solid-state batteries use a solid electrolyte, which allows them to combine high energy density with a compact design, making them suitable for large-capacity devices such as electric bicycles and electric cars.

[0029] There are three types of solid-state batteries: coin type, pouch type, and cylindrical type. Cylindrical solid-state batteries have the advantage of being able to pack more energy into a small space by effectively utilizing the layered structure of the electrodes and electrolyte, making it possible to provide the advantages of solid-state batteries while maintaining the same shape as conventional cylindrical batteries.

[0030] Figure 3 shows an example of a cylindrical all-solid-state battery, in which a positive electrode 3, a solid electrolyte 5, and a negative electrode 4 are laminated, with a terminal plate 1 and a current collecting terminal 2 supplying electrons to the positive electrode 3 inside the battery, and a negative electrode (CNWs) 4 receiving electrons inside the battery, and having the electrical conductivity and chemical reaction properties of the solid electrolyte 5. It is expected that a cylindrical all-solid-state battery will operate by combining these elements, achieving high energy density and excellent safety.

[0031] Figure 4 shows a typical scanning electron microscope (SEM) image of carbon nanowalls (CNWs) formed on electrolytic copper foil. This is an observation of the electrolytic copper foil from above, and it can be seen that a thin layer of material is deposited on the surface of the electrolytic copper foil, and curved wall-like structures protrude vertically from the substrate. These curved wall-like structures are composed of carbon atoms. We conduct observations such as SEM to understand the synthesis state and properties.

[0032] A transmission electron microscope image of CNWs peeled off from a substrate is shown in Figure 5. The graphene sheets are clearly confirmed to be composed of more than ten layers, and are shown to have the structure of graphite and to be part of it.

[0033] Figure 6 shows the Raman spectrum of a typical carbon nanowall. A Raman spectrum is a spectrum obtained when a material scatters light, and provides information about the molecular structure and vibrational modes of the material. -1Peak around 1,350 cm⁻¹ (D band): This peak is due to defects and incomplete structures, and the D band occurs due to disturbances and defects in the crystal structure within the carbon nanowall. The G band is a peak caused by lattice vibrations of graphene, and is an important characteristic that indicates the crystallinity of a material and the presence of graphene. Peak around 1,350 cm⁻¹ (D band): This peak is due to defects and incomplete structures, and the D band occurs due to disturbances and defects in the crystal structure within the carbon nanowall. [Industrial Applicability]

[0034] According to the present invention, it is possible to provide an all-solid-state lithium battery with improved performance, long life, and safety. [Explanation of symbols]

[0035] 1………………terminal board 2………………Current collector terminal 3………………Positive electrode (LiCoO2) 4………………Negative electrode (CNWs) 5………………Solid electrolyte 6………………Charging 7……………………discharge 8………………Li⁺ ion 9………………Aluminum current collector 10………………Copper foil 11...Copper oxide layer 12………………NaOH solution 13………………Aquarium 14………………Purified water 15....Nitrogen gas 16………………Stent 17………………Cu fine particles 18...Plasma CVD equipment 20...Carbon nanowalls (CNWs)

Claims

1. An all-solid-state lithium battery characterized by having a positive electrode made of a lithium compound and a negative electrode made of carbon nanowalls grown on the surface of a substrate, with a solid electrolyte provided between the positive electrode and the negative electrode.

2. 2. The all-solid-state lithium battery according to claim 1, wherein the negative electrode, the solid electrolyte, and the positive electrode are laminated to form a cylindrical structure.

3. 2. The all-solid-state lithium battery according to claim 1, wherein the substrate is an electrolytic copper foil.

4. 4. The all-solid-state lithium battery according to claim 3, wherein after copper oxide is removed from the surface of the electrolytic copper foil, carbon nanowalls are grown to form the negative electrode.

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