Conductive particles containing a phosphate-based material for a positive electrode or a negative electrode

Abstract

Provided are conductive particles containing a phosphate system for a positive electrode or a negative electrode. 【Solution means】The conductive particles 40 are used in the electrodes of a solid battery or a semi-solid battery. The conductive particles include ceramic particles 30 for guiding lithium ions and dispersing them in the lithium ion channels, an amorphous carbon layer 50 that covers the outer surface of the ceramic particles, has conductivity, and suppresses the expansion of the ceramic particles, a plurality of graphene sheet layers 54 that are mixed in the amorphous carbon layer and form a multilayer structure covering the outer periphery of the ceramic particles, and a plurality of first carbon nanotubes 56 that are mixed in the amorphous carbon layer and serve as crosslinks between the graphene sheet layer and the ceramic particles and between different graphene sheet layers.

Description

Technical Field

[0001] The present invention relates to a battery electrode material, and more particularly to conductive particles containing a phosphate-based material for a positive electrode or a negative electrode.

Background Art

[0002] A battery is mainly formed by disposing electrodes (a positive electrode and a negative electrode) in an electrolyte solution. In the prior art, the ion conductivity is increased by adding an LLZO material to the electrodes. Since the LLZO material has a high ion conductivity with respect to lithium ions, when lithium ions pass through the electrodes, the lithium ion channels are dispersed by being guided by the dispersed LLZO particles. Therefore, by distributing lithium ions as a uniform channel inside the electrodes, a situation where lithium ions abnormally accumulate in the electrode slurry and a side reaction with the electrode slurry occurs is prevented.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in the manufacturing process of the electrodes, since moisture is present, the hydrophilic LLZO particles are likely to absorb moisture and generate alkaline substances. In order to prevent the LLZO particles from absorbing moisture in the manufacturing process of the electrodes, it was necessary to coat the outer layer of the LLZO particles with a protective layer. When the outer surface of conventional LLZO particles is coated with polydopamine, since the electronic conductivity of dopamine itself is low, the electronic conductivity of the electrode plate decreases.

[0004] Based on years of experience in battery materials, the present inventor proposed a novel design. That is, by coating the outer surface of the LLZO material with a carbon layer, it becomes hydrophobic, making it difficult for moisture to enter the LLZO material. In addition, the carbon layer enhances the conductivity of the entire electrode particle. Note that in order to enhance the ionic conductivity, lithium fluoride particles are added into the carbon layer, and by adding carbon nanotubes to enhance the conductivity of the entire electrode, the volume expansion of the electrode particles can be improved, and the efficiency of the electrode is further increased.

[0005] In view of the above problems, the present invention has been made through the intensive research of the present inventor, and its purpose is to provide conductive particles containing a phosphate-based material for a positive electrode or a negative electrode.

Means for Solving the Problems

[0006] In order to solve the above problems, the conductive particles containing a phosphate-based material for a positive electrode or a negative electrode, which is an aspect of the present invention, can suppress the volume expansion of the entire conductive particles by coating the outer periphery of the ceramic particles with an amorphous carbon layer so as to prevent damage due to excessive expansion of the conductive particles. The amorphous carbon layer has suitable conductivity and can enhance the conductivity of the entire conductive particles. In order to prevent the conduction of lithium ions from becoming difficult due to the thickness of the amorphous carbon layer being too thick, the amorphous carbon layer further includes a plurality of lithium fluoride particles serving as a jumping board for lithium ion channels to assist in guiding lithium ions.

[0007] From the descriptions of the specification and drawings to be described later, at least the following matters will become clear.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution means of the invention.

[0010] First, an example of a specific embodiment of the conductive particles 40 containing a phosphate-based material for a positive electrode or a negative electrode of the present invention will be described with reference to FIGS. 1 to 4.

[0011] The conductive particles 40 containing a phosphate-based material for a positive electrode or a negative electrode according to the present invention are mainly used for the electrode 10 of a solid battery or a semi-solid battery. The electrode 10 includes an electrode substrate 11 for placing the material of the electrode 10 and an electrode slurry layer 13 coated on the electrode substrate 11. (See FIG. 3). The electrode slurry layer 13 includes an electrode slurry 12 containing a plurality of conductive particles 40 and a binder, and the weight percentage of the plurality of conductive particles 40 in the electrode slurry layer is in the range of 0.1 wt% to 1 wt%. The particle size of each of the conductive particles 40 is less than 200 nm.

[0012] In such a case, as shown in FIG. 1, the conductive particles 40 of the present invention include the following configuration. Each will be described below.

[0013] <Ceramic particles 30> The size of the particles is less than 150 nm. The ceramic particles 30 have high lithium ion conductivity. When lithium ions pass through the electrode 10, they are guided by the ceramic particles 30, and the lithium ion channels are dispersed. By forming uniformly distributed lithium ion channels in the electrode, the situation where lithium ions abnormally accumulate in the electrode slurry and a side reaction with the electrode slurry occurs is prevented.

[0014] The ceramic particles 30 are a ceramic oxide or phosphate-based material, a garnet or perovskite-structured oxide, or a sulfide having a lithium ion conduction ability (the lithium ion conductivity is more than 10 -3 cm 2 / s (diffusion coefficient).

[0015] The oxide having the lithium ion conduction ability is, for example, lithium aluminum titanium phosphate (LATP) having a NASICON (sodium (Na) super ionic conductor) structure, lithium aluminium germanium phosphate (LAGP), etc. The phosphate-based material having the lithium ion conduction ability is, for example, lithium phosphate (Li 3 PO 4 ). The oxide having a garnet or perovskite structure is, for example, lithium lanthanum zirconium oxide (Li 7 La 3 Zr 2 O 12, lithium lanthanum zirconium oxide (LLZO) or lithium lanthanum titanium oxide (LLTO). The sulfide is, for example, lithium germanium phosphorus sulfur (LGPS). The ceramic particles 30 may be a combination of the above components in any ratio.

[0016] The ceramic particles 30 are made of LLZO material, and the LLZO material is formed of at least one of LLZO, Ga-LLZO (Ga-doped LLZO, gallium-doped lithium lanthanum zirconium oxide), Cu-LLZO (Cu-doped LLZO, copper-doped lithium lanthanum zirconium oxide), Ta-LLZO (Ta-doped LLZO, tantalum-doped lithium lanthanum zirconium oxide), Sr-LLZO (Sr-doped LLZO, strontium-doped lithium lanthanum zirconium oxide), and Al-LLZO (Al-doped LLZO, aluminum-doped lithium lanthanum zirconium oxide).

[0017] When the ceramic particles 30 are made of LAGP or LATP, the LAGP or LATP is Li 1+x Al x A 2-x (PO 4 ) 3 , or Li 1+x+y Al x A 2-x-y-z M y N z (PO 4 ) 3 selected from, where x ranges from 0.1 to 0.8, y ranges from 0 to 0.2, and z ranges from 0 to 0.2. A is Ge (germanium) or Ti (titanium). M is Sc 3+ (scandium ion), Y 3+ (yttrium ion), Ga 3+ (gallium ion), In3+ (Indium ion), La 3+ Trivalent cations such as (lanthanum ion). N is Zr 4+ (Zirconium ion), Si 4+ (Silicon ion), Sn 4+ Tetravalent cations such as (tin ion).

[0018] <Amorphous carbon layer 50> It covers the outer surface of the ceramic particles 30. The radial thickness of the amorphous carbon layer 50 is less than 10 nm. The amorphous carbon layer 50 itself has good electrical conductivity, and when the ceramic particles 30 are filled with lithium ions, it can suppress excessive volume expansion, thereby achieving the purpose of protecting the conductive particles 40 from being damaged.

[0019] The amorphous carbon layer 50 includes amorphous carbon 52 formed of at least one of the following. (i) Hard carbon or soft carbon formed by an organic resin system through sintering and de-esterification, or hard carbon or soft carbon formed by an organic carbohydrate through sintering and de-esterification. (ii) Amorphous carbon formed by an organic compound in a reducing atmosphere. The organic compound is selected from carbohydrates (monosaccharides, disaccharides, oligosaccharides, polysaccharides, etc.), water-soluble fibers, or amino acid polymers, etc. Preferably, the organic compound is a carbon-containing compound containing at least one element of nitrogen, fluorine, phosphorus, or sulfur. Through a reduction reaction, these elements (i.e., nitrogen, fluorine, phosphorus, or sulfur) are doped into carbon, and the electron conductivity of the conductive particles 40 is increased. (iii) Amorphous carbon formed by a carbohydrate through dehydration. (iv) Amorphous carbon containing a plurality of carbon skeletons and some functional groups formed by dehydration of a water-soluble fiber. (v) Amorphous carbon formed by dehydration of an amino acid polymer, formed of a plurality of carbon skeletons of a straight chain or side chain containing a doping element.

[0020] A plurality of graphene sheet layers 54 are mixed in the amorphous carbon layer 50, and each of the graphene sheet layers 54 is composed of 2 to 10 layers of thin-layer graphene. The sheet diameter of the graphene sheet layer 54 (i.e., the area of graphene) is less than 500 nm. Each of the graphene sheet layers 54 has a sheet-like structure, and a multilayer structure covering the outer periphery of the ceramic particles 30 is formed by the plurality of graphene sheet layers 54.

[0021] A plurality of first carbon nanotubes 56 are mixed in the amorphous carbon layer 50, and the size of the first carbon nanotubes 56 is less than 1 μm. There is a gap between the plurality of graphene sheet layers 54 and the ceramic particles 30. The plurality of first carbon nanotubes 56 are used to cross-link between the graphene sheet layer 54 and the ceramic particles 30 or between different graphene sheet layers 54 in order to further enhance the conductivity efficiency of the conductive particles 40.

[0022] The weight ratio of the ceramic particles 30 to the amorphous carbon layer 50 is 99.5:0.5. The weight ratio of the weight of the graphene sheet layer 54 to the total weight of the plurality of first carbon nanotubes 56 is 4:1.

[0023] In such a case, as shown in FIG. 2, the present invention further includes the following configuration.

[0024] <A plurality of lithium fluoride (LiF) particles 55> They are distributed in the amorphous carbon layer 50. Since the efficiency of lithium ions passing through the conductive particles 40 is affected by the thickness of the amorphous carbon layer 50, by using the plurality of lithium fluoride particles 55 as a jumping board for lithium ions, the lithium ions pass through the conductive particles 40 by the plurality of lithium fluoride particles 55. By doing so, it helps to guide the lithium ions.

[0025] The particle size of each of the lithium fluoride particles 55 is less than 5 nm. The weight ratio of the weight of the ceramic particles 30 to the total weight of the plurality of lithium fluoride particles 55 is in the range of 99.9 to 99.95:0.1 to 0.05.

[0026] In such a case, as shown in FIG. 4, the present invention further includes the following configuration.

[0027] A plurality of second carbon nanotubes (Carbon NanoTube, CNT) 42 cover the outer periphery of the conductive particles 40, thereby forming composite particles 45. The length of the second carbon nanotubes 42 is in the range of 1 μm to 3 μm.

[0028] Carbon nanotubes are very good conductive materials, and have a plurality of the second carbon nanotubes 42 and the composite particles 45 of the conductive particles 40 in the form of yarn. The second carbon nanotubes 42 are used to enhance the conductivity of electrons and enable the conduction of electrons on the conductive particles 40. Since carbon nanotubes have extremely high conductivity, lithium ions can be conducted between the conductive particles 40 by the carbon nanotubes, and the conductivity of the entire electrode is increased.

[0029] The weight ratio of the total weight of the plurality of second carbon nanotubes 42 to the conductive particles 40 is in the range of 1:99 to 0.2:99.8.

[0030] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included.

Explanation of Reference Numerals

[0031] 10 Electrode 11 Electrode Substrate 12 Electrode Slurry 13 Electrode Slurry Layer 30 Ceramic Particles 40 Conductive particles 42 Second carbon nanotube 45 Composite particles 50 Amorphous carbon layer 52 Amorphous carbon 54 Graphene sheet layer 55 Lithium fluoride particles 56 First carbon nanotube

Claims

1. A conductive particle containing a phosphoric acid system for a positive or negative electrode used in an electrode of a solid-state or semi-solid battery, Ceramic particles used to guide lithium ions and form lithium ion channels uniformly distributed within the electrode; an amorphous carbon layer covering an outer surface of the ceramic particle, the amorphous carbon layer having a specific electrical conductivity and used to suppress expansion of the volume of the ceramic particle when the ceramic particle is filled with lithium ions; a plurality of graphene sheet layers mixed in the amorphous carbon layer, each of the graphene sheet layers having a sheet-like structure, the plurality of graphene sheet layers forming a multilayer structure that covers the outer periphery of the ceramic particle; a plurality of first carbon nanotubes mixed in the amorphous carbon layer, the plurality of first carbon nanotubes being used to bridge between each of the graphene sheet layers and the ceramic particles and between different graphene sheet layers; A conductive particle containing a phosphate system for positive or negative electrodes, characterized in that a plurality of second carbon nanotubes cover the outer periphery of the conductive particle to form a composite particle, and the composite particle has a wool-like shape.

2. 2. The conductive particle containing phosphate for positive or negative electrodes according to claim 1, further comprising a plurality of lithium fluoride particles distributed in the amorphous carbon layer, the plurality of lithium fluoride particles being springs for a lithium ion channel to help guide lithium ions, and the plurality of lithium fluoride particles being distributed in an island-like manner.

3. The ceramic particles have a lithium ion conductivity of 10 －３ cm ２ The conductive particles containing phosphoric acid for positive or negative electrodes according to claim 1, characterized in that the conductive particles are formed of at least one of ceramic oxides or phosphates, oxides having a garnet or perovskite structure, and sulfides, each of which has a diffusion coefficient (diffusion coefficient) of more than 10000 / s.

4. 4. The conductive particles containing phosphate for positive or negative electrodes according to claim 3, wherein the oxide or phosphate having lithium ion conductivity is at least one selected from lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP) having a NASICON (sodium (Na) super ionic conductor) structure.

5. The ceramic particles are composed of LAGP or LATP, and the LAGP or LATP is Li １＋ｘ A ｘ A ２－ｘ (P.O. ４ ) ３ , or Li １＋ｘ＋ｙ A ｘ A ２－ｘ－ｙ－ｚ M ｙ N ｚ (P.O. ４ ) ３ The conductive particles containing a phosphate system for positive or negative electrodes according to claim 1, characterized in that x is in the range of 0.1 to 0.8, y is in the range of 0 to 0.2, z is in the range of 0 to 0.2, A is Ge (germanium) or Ti (titanium), M is a trivalent cation, and N is a tetravalent cation.

6. M is Sc ３＋ (Scandium ion), Y ３＋ (yttrium ion), Ga ３＋ (Gallium ion), In ３＋ (Indium ion), La ３＋ 6. The conductive particles containing a phosphate system for a positive electrode or a negative electrode according to claim 5, characterized in that the phosphate system is selected from (lanthanum ion).

7. N is Zr ４＋ (zirconium ion), Si ４＋ (Silicon ion), Sn ４＋ 6. The conductive particles containing a phosphoric acid system for a positive electrode or a negative electrode according to claim 5, characterized in that the phosphoric acid system is selected from (tin ions).

8. The conductive particles containing phosphoric acid for positive or negative electrodes according to claim 2, characterized in that the lithium fluoride particles have a particle size of less than 5 nm, and a weight ratio of the ceramic particles to a total weight of the lithium fluoride particles is in the range of 99.9 to 99.95: 0.1 to 0.

05.

9. 2. The conductive particles containing phosphate for positive or negative electrodes according to claim 1, wherein the amorphous carbon layer has a radial thickness of less than 10 nm, and the conductive particles have a particle size of less than 200 nm.

10. The conductive particles containing phosphate for positive or negative electrodes according to claim 1 , wherein the ceramic particles have a particle size of less than 150 nm, and each of the first carbon nanotubes has a size of less than 1 μm.

11. The amorphous carbon layer is Hard or soft carbons formed by sintering deesterification of organic resins or organic carbohydrates; Amorphous carbon formed in a reducing atmosphere from organic compounds, Amorphous carbon is formed when carbohydrates undergo dehydration. Amorphous carbon having a plurality of carbon skeletons and some functional groups is formed by dehydrating the water-soluble fiber; and The conductive particles containing a phosphate system for positive or negative electrodes according to claim 1, characterized in that the amino acid polymer is formed by dehydration, and the amorphous carbon is formed of at least one of the following: amorphous carbon formed of multiple linear or side chain carbon skeletons containing a doping element.

12. The conductive particles containing a phosphate system for positive or negative electrodes according to claim 11, characterized in that the organic compound is a carbohydrate selected from at least one of monosaccharides, disaccharides, oligosaccharides, polysaccharides, water-soluble fibers, and amino acid polymers.

13. The conductive particles containing a phosphate system for positive or negative electrodes according to claim 11, characterized in that the organic compound is a carbon-containing compound containing at least one element selected from the group consisting of nitrogen, fluorine, phosphorus, and sulfur.

14. 2. The conductive particle containing a phosphoric acid system for a positive electrode or a negative electrode according to claim 1, wherein the graphene sheet layer is a thin-layer graphene having 2 to 10 layers, the graphene sheet layer has a sheet-like structure, and a sheet diameter is less than 500 nm.

15. 2. The conductive particle containing phosphate for positive or negative electrodes according to claim 1, wherein a weight ratio of the ceramic particles to a total weight of the amorphous carbon layer is 99.5:0.5, and a weight ratio of the total weight of the graphene sheet layers to a total weight of the first carbon nanotubes is 4:1.

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