Roll-to-roll formation process for solid electrolytes using colloidal metal particles

Abstract

A roll-to-roll forming process of a solid electrolyte using colloidal metal particles, the roll-to-roll forming process comprising: (a) directly coating a metal electrode foil with colloidal metal particles to form a solid electrolyte layer; and (b) supplying a sulfur source to the solid electrolyte layer formed in step (a) to induce a sulfidation reaction and thereby form a sulfide-based solid electrolyte layer.

Description

Technical area

[0001] The present invention relates to a roll-to-roll forming method of a solid electrolyte using colloidal metal particles, and more particularly, to a method of coating a metal electrode foil (a positive electrode plate or a negative electrode plate) with colloidal metal particles and sequentially inducing a sulfidation reaction using a roll-to-roll method to form a sulfide-based solid electrolyte. State of the art

[0002] A secondary battery, which is a battery that can be used semi-permanently through repeated charging and discharging, refers to a device that converts external electrical energy into chemical energy, stores the chemical energy, and generates electricity when needed using the chemical energy. The four core materials of a secondary battery are a positive electrode material, a negative electrode material, a separator, and an electrolyte.

[0003] A lithium-ion battery, a representative secondary battery, has the advantages of being lighter and smaller than other batteries of the same capacity, and higher performance than conventional batteries. The lithium-ion battery is rapidly expanding from a small battery market to the electric vehicle and medium-to-large market. It is applicable as a core technology for future industries and has the potential to expand into various industries.

[0004] However, since the lithium-ion battery, which is a general secondary battery, uses a liquid electrolyte containing an organic solvent, there are various problems related to the stability of the battery, such as leakage, shock load, ignition and explosion caused by the use of the organic solvent.

[0005] As a result, a solid-state battery is attracting attention as a next-generation secondary battery. It replaces the liquid electrolyte, a component of conventional lithium-ion batteries, with a solid electrolyte. The solid-state battery has the advantages of significantly reducing the risk of fire and explosion due to the use of a solid electrolyte, having a wide range of applications, being manufactured through a simplified manufacturing process, and exhibiting high energy density.

[0006] The conventional all-solid-state battery has the problem of undergoing complex processes such as synthesis of sulfide powder with a desired composition, electrode coating, rolling, and heat treatment to form the solid electrolyte, which is a core component of the all-solid-state battery.

[0007] In particular, (1) it is difficult to compact pre-synthesized ceramic particles without voids in a sulfide powder compaction process, and (2) it is difficult for the pre-synthesized ceramic particles to form a homogeneous interface with particles forming a positive electrode and a negative electrode. Document CN 1 11 977 681 A further discloses a sulfide solid electrolyte material and a gas-phase synthesis method and application of the sulfide solid electrolyte material. State-of-the-art documents Korean registered patent KR 10 2 088 648 B1 Korean registered patent KR 10 2 193 945 B1 Chinese patent application CN 1 11 977 681 A RevelationTechnical Problem

[0008] It is an object of the present invention to provide a roll-to-roll forming method for a solid electrolyte using colloidal metal particles, wherein a metal electrode foil is directly coated with colloidal metal particles to design a solid electrolyte material having a desired composition, and a sequential sulfidation reaction is induced using a roll-to-roll method without a complex powder processing process to form a void-free sulfide-based solid electrolyte material. Technical solution

[0009] To achieve the above-mentioned object, the present invention provides a roll-to-roll forming method of a solid electrolyte using colloidal metal particles, the roll-to-roll forming method comprising: (a) directly coating a metal electrode foil with colloidal metal particles to form a solid electrolyte layer; and (b) supplying a sulfur source to the solid electrolyte layer formed in step (a) to induce a sulfidation reaction and thereby form a sulfide-based solid electrolyte layer.

[0010] In the direct coating step for forming the solid electrolyte layer, the colloidal metal particles may be colloidal particles consisting of at least one of individual metal particles of copper (Cu), lithium (Li), germanium (Ge), phosphorus (P), silicon (Si), sodium (Na), molybdenum (Mo), lanthanum (La) or zirconium (Zr) and alloy metal particles selected from a group consisting of combinations thereof.

[0011] In the step of inducing a sulfidation reaction to form the sulfide-based solid electrolyte layer, the sulfur source may comprise at least one of hydrogen sulfide (H2S), sulfur gas (S vapor), and methyl mercaptan (CH3SH), and may be supplied by a continuous or pulsed gas supply. Beneficial effects

[0012] In a roll-to-roll forming method of a solid electrolyte using colloidal metal particles according to an embodiment of the present invention, a metal electrode foil is directly coated with individual colloidal metal particles such as copper or lithium or colloidal metal alloy particles, whereby it is possible to design a solid electrolyte material having a desired composition.

[0013] Furthermore, a sulfidation reaction is sequentially induced on a solid electrolyte formation layer using a roll-to-roll method without a complex powder processing process, making it possible to form a void-free sulfide-based solid electrolyte material. Description of the drawings Fig. 1 is a flowchart showing a roll-to-roll forming process of a solid electrolyte using colloidal metal particles according to an embodiment of the present invention. Fig. 2 is a view showing a process for directly coating a metal electrode foil with colloidal metal particles according to an embodiment of the present invention. Fig. 3 is a view showing a process of supplying a sulfur source to a solid electrolyte formation layer formed by coating on a metal electrode foil to induce a sequential sulfidation reaction according to an embodiment of the present invention. Best mode

[0014] The present invention will be described in more detail below.

[0015] An embodiment of the present invention relates to a roll-to-roll forming method of a solid electrolyte using colloidal metal particles, the roll-to-roll forming method comprising:

[0016] directly coating a metal electrode foil with colloidal metal particles to form a solid electrolyte layer (e.g., step (a)); and

[0017] Supplying a sulfur source to the solid electrolyte layer formed in the above step to induce a sulfidation reaction and thereby form a sulfide-based solid electrolyte layer (e.g., step (b)).

[0018] Specifically, in the method of the present invention, an electrode is directly coated with colloidal metal particles to form a solid electrolyte layer, and a sulfur source is sequentially supplied using a roll-to-roll process after the electrode is directly coated with the colloidal metal particles to form a sulfide-based solid electrolyte. Furthermore, it is possible to minimize potentially occurring voids at an interface between the electrode and metal particles or voids between the metal particles.

[0019] In the roll-to-roll process, a material is applied, coated, or printed while being wound around a rotating roll in an electrode process. According to the roll-to-roll process, the material can be transferred from one roll to another by rotating a pair of rolls spaced at a predetermined distance from each other.

[0020] Roll-to-roll technology is gaining increasing importance in the secondary battery industry due to its large area advantage and process simplification. In the present invention, an electrode is coated with colloidal metal particles through sequential processes using the roll-to-roll method, and a sulfur source is sequentially supplied to a metal-colloidal solid electrolyte layer formed by coating to form a sulfide-based solid electrolyte with minimized voids.

[0021] With reference to Fig. 2, in step (a), a particle supply unit 300 configured to supply colloidal metal particles to one of a pair of rollers 210 and 220 configured to transfer a metal electrode foil 100 may be arranged at a position spaced from one of the pair of rollers 210 and 220. For example, the particle supply unit 300 may be arranged near the right roller 210, which is a roller of the Fig. 1 shown pair of rollers 210 and 220. Here, one roller (ie the right roller in Fig. 2) denote a roll from which the transfer of the metal electrode foil 100 is started, and the other roll (ie the left roll in Fig. 2) may denote a roll at which the transfer of the metal electrode foil 100 is completed. That is, the metal electrode foil 100 may be transferred from one roll, which is one of the pair of spaced-apart rollers 210 and 220, to the other roll.

[0022] In step (a), the metal electrode foil 100 passing one of the pair of rollers may be coated with colloidal metal particles supplied by the particle supply unit 300. That is, colloidal metal particles may be supplied to one of the pair of rollers (the right roller in Fig. 2) be supplied by the particle supply unit, and the part of the metal electrode foil passing one of the pair of rollers can be coated with the colloidal metal particles, whereby a solid electrolyte layer can be formed.

[0023] In step (b), a sulfur source may be sequentially supplied in a longitudinal direction of the metal electrode foil 100 when the metal electrode foil 100 is transferred in a roll-to-roll manner. Specifically, a sulfur source supply unit 400 configured to supply the sulfur source may be installed above the metal electrode foil 100 being transferred (i.e., from the solid electrolyte layer to the metal electrode foil) so that it is spaced apart therefrom. That is, as shown in Fig. As shown in Figure 2, the sulfur source supply unit 400 may be arranged in a direction perpendicular to a direction in which the pair of rollers are spaced apart from each other. At this time, the sulfur source supply unit 400 may be arranged above an imaginary line connecting the pair of rollers so as to be spaced apart therefrom.

[0024] A sulfur source can be sprayed downward from the sulfur source supply unit 400. That is, the metal electrode foil (i.e., the metal electrode foil on which the solid electrolyte layer is formed) continuously moved between the pair of rollers 210 and 220 can pass under the sulfur source supply unit 400. At this time, the sulfur source can be continuously sprayed toward the metal electrode foil 100 passing under the sulfur source supply unit 400.

[0025] More specifically, when the metal electrode foil 100 coated with the colloidal metal particles and thus having the solid electrolyte layer formed thereon is transferred from one of the pair of rollers 210 and 220 to the other, the sulfur source can be sprayed onto the metal electrode foil 100 in the direction of the solid electrolyte layer by the sulfur source supply unit 400 in step (b).

[0026] Step (a) and step (b) can be performed sequentially and continuously.

[0027] A colloidal electrolyte with individual metal particles or metal alloy particles incorporated therein, such as the metal colloids of the present invention, has the advantage of simplifying the design of a solid electrolyte because the interface properties can be directly controlled. The solid electrolyte is divided into an organic (polymer) electrolyte and an inorganic electrolyte. A colloidal electrolyte, such as the metal colloids of the present invention, can be classified as the inorganic electrolyte.

[0028] The colloidal metal particles may be colloids consisting of at least one of individual metal particles of copper (Cu), lithium (Li), germanium (Ge), phosphorus (P), silicon (Si), sodium (Na), molybdenum (Mo), lanthanum (La) or zirconium (Zr) and alloy metal particles selected from a group consisting of combinations thereof.

[0029] The colloidal metal particles may contain chlorine (Cl), magnesium (Mg), and sodium (Na) for dispersibility and doping purposes and may be used with molecules such as polyethylene oxide (PEO) and polyacrylonitrile (PAN), polyvinylidene difluoride (PVDF), and polymethyl methacrylate (PMMA); however, the present invention is not limited thereto.

[0030] A dispersant that can be used to form the colloidal electrolyte can include, but is not limited to, a single solvent such as fluoroethylene carbonate (FEC), polyethylene glycol (PEG), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), or dimethyl carbonate (DMC), or a mixture thereof.

[0031] In the embodiment of the present invention, the sulfur source comprises at least one of hydrogen sulfide (H2S), sulfur gas (S vapor), and methyl mercaptan (CH3SH) and is supplied by continuous or pulsed gas supply. The sulfur source is sequentially supplied to the solid electrolyte layer formed by directly coating the metal electrode foil with the colloidal metal particles by continuous or pulsed gas supply, thereby inducing a sulfidation reaction to form a sulfide-based solid electrolyte.

[0032] In the embodiment of the present invention, the sulfur source may comprise thiol-containing molecules including a thiol group.

[0033] In the embodiment of the present invention, the metal electrode foil can be heated to a temperature ranging from room temperature to 500°C, depending on the type of metal colloids, when the sulfur source is supplied. The metal electrode foil can be preheated by a separate heating element or can be heated by heating one of the pair of rollers.

[0034] It is possible to induce a sulfidation reaction by supplying a sulfur source to a colloidal solid metal electrolyte layer formed by direct coating on a metal electrode foil, without the effort of primarily synthesizing sulfide powder with a desired composition and coating it on an electrode, performing a process that uses a high-energy ball mill to ensure the composition and crystallinity of the sulfide powder, or undergoing complex processes such as rolling and heat treatment to form a solid electrolyte, as in the prior art.

[0035] Although the specific details of the present invention have been described in detail, one of ordinary skill in the art to which the present invention belongs will recognize that the detailed description discloses only preferred embodiments of the present invention and thus does not limit the scope of the present invention. It is possible for one of ordinary skill in the art to which the present invention relates to make various applications and modifications within the scope of the invention based on the above description.

[0036] Accordingly, the essential scope of the present invention is defined by the appended claims and their equivalents.

Claims

[1] A roll-to-roll forming process of a solid electrolyte using colloidal metal particles, the roll-to-roll forming process comprising: (a) directly coating a metal electrode foil with colloidal metal particles to form a solid electrolyte layer; and (b) supplying a sulfur source to the solid electrolyte layer formed in step (a) to induce a sulfidation reaction and thereby form a sulfide-based solid electrolyte layer. [2] The roll-to-roll forming method according to claim 1, wherein in step (b), the sulfur source is sequentially supplied in a longitudinal direction of the metal electrode foil when the metal electrode foil is transferred in a roll-to-roll manner. [3] A roll-to-roll forming method according to claim 2, wherein a sulfur source supply unit configured to supply the sulfur source is installed above the solid electrolyte layer, which is transferred so as to be spaced therefrom, and the sulfur source is sprayed downwards from the sulfur source supply unit. [4] The roll-to-roll forming method according to claim 1, wherein in step (a), a particle supply unit configured to supply the colloidal metal particles toward one of a pair of rollers configured to transfer the metal electrode foil is arranged at a position spaced apart from the one of the pair of rollers. [5] The roll-to-roll forming method according to claim 4, wherein in step (a), the metal electrode foil passing by one of the pair of rollers is coated with the colloidal metal particles supplied by the particle supply unit. [6] The roll-to-roll forming method according to claim 5, wherein, when the solid electrolyte layer formed on the metal electrode foil as a result of coating the metal electrode foil with the colloidal metal particles is transferred to the other of the pair of rollers, the sulfur source is sprayed toward the solid electrolyte layer in step (b). [7] A roll-to-roll forming method according to claim 4, wherein step (a) and step (b) are carried out sequentially and continuously. [8] The roll-to-roll forming method according to claim 1, wherein the metal electrode foil is preheated to a temperature in a range of room temperature to 500°C when step (b) is carried out. [9] The roll-to-roll forming method according to claim 1, wherein the colloidal metal particles are colloidal particles consisting of at least one of individual metal particles of copper (Cu), lithium (Li), germanium (Ge), phosphorus (P), silicon (Si), sodium (Na), molybdenum (Mo), lanthanum (La) or zirconium (Zr) and alloy metal particles selected from a group consisting of combinations thereof. [10] The roll-to-roll forming method according to claim 1, wherein the sulfur source comprises at least one of hydrogen sulfide (H2S), sulfur gas (S vapor), and methyl mercaptan (CH3SH), and is supplied by a continuous or pulsed gas supply.

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