Electrode for lithium metal battery and lithium metal battery comprising same

Abstract

An electrode for a lithium metal battery according to embodiments of the present invention includes a lithium metal storage layer containing silicon oxide particles. The silicon oxide particles have a porous structure, and the molar ratio of oxygen to silicon in the silicon oxide particles is 1.5 or more and less than 2.0. A lithium metal battery according to embodiments of the present invention includes the electrode for a lithium metal battery according to the above-described embodiments.

Description

Electrode for lithium metal battery and lithium metal battery including same

[0001] The present disclosure relates to an electrode for a lithium metal battery and a lithium metal battery including the same.

[0002]

[0003] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as hybrid vehicles.

[0004] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries. Among these, lithium secondary batteries are actively being researched and developed due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and weight reduction.

[0005] Graphite and silicon are commonly used as anode materials for lithium secondary batteries. However, graphite and silicon have high reaction potentials and low capacities, limiting their ability to increase the energy density and capacity of lithium secondary batteries. Energy density can be improved by using lithium metal, which has low potential and high capacity, as an anode material.

[0006] However, when lithium metal is used as an anode material, lithium can grow unevenly on the surface of the lithium metal during the charging process, forming lithium dendrites. This can lead to short circuits, overheating, and explosion of the electrode. Furthermore, the electrode volume can repeatedly expand and contract during the deposition and desorption process on the lithium metal surface, potentially compromising the stability of the lithium secondary battery.

[0007]

[0008] An object of the present disclosure is to provide an electrode for a lithium metal battery having improved capacity and stability.

[0009] An object of the present disclosure is to provide a lithium metal battery with improved capacity and stability.

[0010]

[0011] An electrode for a lithium metal battery according to embodiments of the present disclosure includes a lithium metal storage layer comprising silicon oxide particles. The silicon oxide particles have a porous structure, and the molar ratio of oxygen to silicon contained in the silicon oxide particles is 1.5 or more and less than 2.0.

[0012] In some embodiments, the silicon oxide particles are SiO x , and 1.5≤x<2.

[0013] In some embodiments, the porosity of each of the silicon oxide particles may be from 10% to 90%.

[0014] In some embodiments, the porosity of the lithium metal storage layer may be from 40% to 95%.

[0015] In one embodiment, the size of the pores formed within the silicon oxide particles may be 10 nm to 1 μm.

[0016] In one embodiment, the size of the pores formed within the lithium metal storage layer may be 10 nm to 10 μm.

[0017] In some embodiments, the maximum voltage of the lithium metal storage layer measured during the charging process after initial formation may be 0 V or less relative to the redox voltage of lithium.

[0018] In some embodiments, the electrode for the lithium metal battery may further include an electrode current collector. The lithium metal storage layer may be disposed on at least one surface of the electrode current collector.

[0019] In some embodiments, the silicon oxide particles are lithium silicate (Li y SiO x , 0 <y, 1.5≤x<2)를 포함할 수 있다.

[0020] In some embodiments, at a SOC100% state of charge, the ratio of the lithium content present as lithium silicate within the lithium metal storage layer to the lithium content of lithium metal deposited within the lithium metal storage layer may be 0.9 or greater on a molar basis.

[0021] In one embodiment, the ratio of the content of lithium contained in the lithium metal storage layer at a SOC100% state to the content of lithium contained in the lithium metal storage layer at a SOC0% state may be 2.2 or less in moles.

[0022] A lithium metal battery according to embodiments of the present disclosure includes the electrode for a lithium metal battery described above.

[0023] In a method for manufacturing silicon oxide particles for lithium metal batteries according to embodiments of the present disclosure, a silicon precursor having a porous structure is mixed with an alkaline earth metal or carbon powder to form a mixture. The mixture is heat-treated, and the heat-treated mixture is washed to obtain silicon oxide particles. The molar ratio of oxygen to silicon in the silicon oxide particles is 1.5 or more and less than 2.0.

[0024] In some embodiments, the heat-treated mixture may be mixed with an acid before washing the heat-treated mixture.

[0025] In some embodiments, the silicon precursor may be SiO2.

[0026] In some embodiments, the alkaline earth metal may be magnesium (Mg).

[0027]

[0028] An electrode for a lithium metal battery includes a lithium metal storage layer comprising silicon oxide particles, wherein a molar ratio of oxygen to silicon in the silicon oxide particles may be 1.5 or more and less than 2.0. Accordingly, lithium metal can be deposited and desorbed within the silicon oxide particles.

[0029] Silicon oxide particles can have a porous structure. As the reaction surface area for lithium metal increases, the current density can be distributed during charging, suppressing the growth of lithium dendrites. Consequently, the electrical properties and stability of lithium metal batteries can be improved.

[0030] The porosity of the lithium metal storage layer can be controlled within a predetermined range. Accordingly, lithium metal nuclei can be uniformly generated within the lithium metal storage layer, and the stable deposition of lithium metal can reduce volume changes in the lithium storage layer.

[0031] Lithium metal batteries according to embodiments of the present disclosure can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other battery-powered solar and wind power generation. Furthermore, lithium metal batteries according to embodiments of the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, and other vehicles that prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0032]

[0033] FIG. 1 is a schematic cross-sectional view illustrating an electrode for a lithium metal battery according to exemplary embodiments.

[0034] FIG. 2 is a schematic cross-sectional view illustrating an electrode for a lithium metal battery according to exemplary embodiments.

[0035] FIG. 3 is a schematic process flow diagram for explaining a method for manufacturing an electrode structure according to exemplary embodiments.

[0036] FIGS. 4 and 5 are schematic plan views and cross-sectional views, respectively, showing lithium metal batteries according to exemplary embodiments.

[0037] Figures 6 and 7 are SEM images of silicon precursor and silicon oxide particles, respectively.

[0038] FIG. 8 is a graph showing the voltage of an electrode for a lithium metal battery according to exemplary embodiments versus the redox voltage of lithium.

[0039] Figure 9 is a graph showing the voltage of an electrode containing SiO versus the redox voltage of lithium.

[0040]

[0041] According to embodiments of the present disclosure, an electrode for a lithium metal battery is provided, which includes a silicon oxide having a porous structure. Furthermore, according to embodiments of the present disclosure, a lithium metal battery is provided, which includes the above-described lithium metal battery electrode.

[0042] According to embodiments of the present disclosure, a method for producing the above-described silicon oxide particles is provided.

[0043] Hereinafter, unless otherwise specifically defined, when a part such as a layer, film, thin film, region, or plate is said to be “on” or “over” another part, this may include not only the case where it is “directly on” the other part, but also the case where there is another part in between.

[0044] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to the drawings. However, the following drawings attached to this specification illustrate some embodiments of the present disclosure and, together with the contents of the invention described above, serve to further understand the technical concept of the present disclosure. Therefore, the present disclosure should not be interpreted as being limited to the matters described in such drawings.

[0045] FIGS. 1 and 2 are schematic cross-sectional views each showing an electrode for a lithium metal battery according to exemplary embodiments.

[0046] Referring to FIGS. 1 and 2, an electrode for a lithium metal battery (hereinafter, abbreviated as “electrode”) may include a lithium metal storage layer.

[0047] The lithium metal storage layer (120) may include silicon oxide particles (122). The molar ratio of oxygen to silicon in the silicon oxide particles (122) may be 1.5 or more and less than 2.0. Accordingly, electrodeposition and desorption reactions of lithium metal may occur on the surface of the silicon oxide particles (122).

[0048] For example, when the molar ratio of oxygen to silicon in the silicon oxide particles (122) is less than 1.5 or 2.0, lithium ions may be alloyed and dealloyed into the silicon oxide particles (122) as a reversible alloying reaction occurs between the silicon oxide and lithium ions. Therefore, the oxidation and reduction reactions of silicon oxide by lithium ions during charge and discharge may occur as the main reversible reaction related to the capacity of the lithium secondary battery.

[0049] According to exemplary embodiments, the silicon oxide particles (122) are SiO x , and 1.5≤x<2 may be satisfied. Therefore, during charge and discharge, the negative electrode reaction may occur substantially by electrodeposition and desorption of lithium metal rather than by oxidation and reduction reactions of silicon oxide particles (122). Therefore, the electrodeposition and desorption of lithium metal may be provided as the main reversible reaction related to the capacity of a lithium secondary battery.

[0050] The lithium metal storage layer (120) may include the silicon oxide particles (122) described above, so that lithium metal can grow within the lithium metal storage layer (120). Lithium metal has a low reaction potential and high capacity, so that the output characteristics and energy density of the lithium metal battery can be improved.

[0051] In one embodiment, a lithium metal battery including an electrode (130) for a lithium metal battery may have a substantially anode-free structure.

[0052] In one embodiment, when manufacturing a lithium metal battery, lithium metal may first be deposited within a lithium metal storage layer (120). Accordingly, the electrode (130) for a lithium metal battery may be used as an anode of the lithium metal battery.

[0053] According to exemplary embodiments, the potential during charging of an electrode (130) for a lithium metal battery (vs. Li / Li) + ) may be less than 0 V. For example, the maximum value of the voltage during charging of the lithium metal storage layer (120) measured after the initial charge / discharge (formation) may be less than 0 V compared to the redox voltage of lithium.

[0054] Since the lithium metal battery electrode (130) has a lower potential than lithium metal, the capacity of the lithium metal battery can be developed through the electrodeposition and desorption of lithium metal. In addition, lithium metal has a low standard reduction potential, which can provide high battery potential and energy density. Accordingly, the lithium metal storage layer (120) can have a low redox potential, so that the capacity and charge / discharge efficiency of the lithium metal battery can be further improved.

[0055] According to exemplary embodiments, the silicon oxide particle (122) may have a porous structure. For example, the silicon oxide particle (122) may include a plurality of pores (124) on the surface and / or inside.

[0056] Lithium metal nuclei can be generated within the silicon oxide particles (122) or in the pores (124) existing between the silicon oxide particles (122). Accordingly, lithium metal can be uniformly grown or deposited within the lithium metal storage layer (120).

[0057] For example, if the current density is unevenly distributed on the surface of the lithium metal storage layer (120), the growth and deposition of lithium metal may be concentrated in a local area, for example, an area where the current is concentrated. In this case, lithium dendrites or lithium ion crystals may grow due to the overvoltage in the area where the current is concentrated.

[0058] Lithium dendrites have low conductivity and can easily lose electrical contact. Consequently, lithium dendrites can detach from the electrode, generating inactive lithium. This can reduce the capacity of lithium metal batteries, lowering their energy density and charge-discharge efficiency.

[0059] In addition, if lithium dendrites grow intensively in certain areas, volume changes such as electrode expansion may increase. Excessively grown lithium dendrites may cause contact between the lithium metal battery electrode (130) and the positive electrode, resulting in an internal short circuit, and may increase side reactions with the electrolyte.

[0060] However, according to exemplary embodiments, the silicon oxide particles (122) may have a porous structure. Accordingly, the current may be uniformly distributed within the lithium metal storage layer (120) through the pores (124), thereby suppressing local current concentration. Accordingly, the uniform current density may allow the lithium metal to grow uniformly within the lithium metal storage layer (120), and the growth of lithium dendrites may be suppressed.

[0061] In addition, by using a lithium metal storage layer (120) including silicon oxide particles (122) rather than a metal current collector composed of Cu, Ni, Al, etc. as a base structure for the growth of lithium metal, the stability and life characteristics of lithium metal can be improved.

[0062] For example, the voltage required for lithium deposition on the surface of a metal current collector may be higher than the voltage required for additional lithium deposition onto the lithium metal. Therefore, lithium metal deposition may be concentrated on regions of the metal current collector surface where lithium metal nuclei are first formed, thereby forming lithium dendrites.

[0063] According to exemplary embodiments, since the silicon oxide particles (122) have the composition ratio of silicon and oxygen described above, the voltage required for lithium to be deposited on the surface of the silicon oxide particles (122) may be substantially the same as or similar to the voltage required for lithium to be additionally deposited on lithium metal.

[0064] Therefore, even if lithium metal nuclei are first formed in some areas of the surface of the silicon oxide particles (122), lithium metal nuclei may be additionally generated in other areas. Accordingly, lithium metal can be uniformly grown on the surface of the silicon oxide particles (122).

[0065] According to exemplary embodiments, the porosity of each silicon oxide particle (122) may be from 10% to 90%. The porosity of the silicon oxide particle (122) may be a percentage of the volume of pores contained within the silicon oxide particle (122) divided by the total volume of the silicon oxide particle (122).

[0066] For example, when the porosity of the silicon oxide particles (122) is less than 10%, the surface area of ​​the silicon oxide particles (122) may decrease, thereby reducing the storage space of lithium metal on the surface of the silicon oxide particles (122) or inside the lithium metal storage layer (120). Accordingly, the reversible capacity due to the deposition and desorption of lithium metal may decrease.

[0067] For example, when the porosity of the silicon oxide particles (122) is less than 90%, the structural stability of the silicon oxide particles (122) may decrease. In addition, as the reaction area becomes excessively large, side reactions between the lithium metal grown within the silicon oxide particles (122) and the electrolyte may increase.

[0068] In some embodiments, the porosity of each silicon oxide particle (122) may be 20% to 90%, 30% to 85%, or 50% to 85%. Within this range, the growth of lithium dendrites is further suppressed, and the life characteristics and capacity of the lithium metal battery may be further improved.

[0069] In one embodiment, the porosity of the silicon oxide particles (122) can be measured through mercury intrusion porosimetry (MIP) or the BET method. In one embodiment, the porosity of the silicon oxide particles (122) can be measured using true density. For example, the density and weight of the silicon oxide particles (122) can be measured, and the porosity can be obtained through the volume calculated through the density and weight and the actual volume measured from the silicon oxide particles (122).

[0070] In one embodiment, the size of the pores (124) formed within the silicon oxide particles (122) may be 10 nm to 1 μm. The size of the pores (124) may refer to the longest diameter of the pores (124).

[0071] Within the above range, lithium metal can be sufficiently deposited and grown within the pores (124) of the silicon oxide particles (122), and the structural stability of the silicon oxide particles (122) can be further improved. Accordingly, the life characteristics and capacity of the lithium metal battery can be further improved.

[0072] According to exemplary embodiments, the porosity of the lithium metal storage layer (120) may be 40% to 95%. The porosity of the lithium metal storage layer (120) may be a percentage of the total volume of all pores contained within the lithium metal storage layer (120) divided by the volume of the lithium metal storage layer (120).

[0073] The pores of the lithium metal storage layer (120) may be derived from pores (124) of silicon oxide particles (122), pores formed between silicon oxide particles (122), pores formed between silicon oxide particles (122) and a binder or conductive material, etc.

[0074] When the porosity of the lithium metal storage layer (120) is within the above range, lithium metal can be more uniformly deposited and desorbed within the lithium metal storage layer (120). Therefore, volume changes in the lithium metal storage layer (120) due to charge and discharge can be suppressed. In addition, even if lithium dendrites grow in local areas of the lithium metal storage layer (120), the volume increase due to the lithium dendrites can be accommodated or alleviated by the pores included in the lithium metal storage layer (120).

[0075] In some embodiments, the porosity of the lithium metal storage layer (120) may be 50% to 95%, 60% to 90%, or 70% to 90%. Within this range, lithium metal can stably grow and disappear within the pores, thereby further improving the stability, ionic conductivity, and energy density of the lithium metal battery electrode (130).

[0076] In one embodiment, the porosity of the lithium metal storage layer (120) can be measured or calculated using mercury porosimetry, BET method, or densitometry.

[0077] In some embodiments, the size of the pores formed within the lithium metal storage layer (120) may be 10 nm to 10 μm. Within this range, sufficient space for lithium metal to be deposited within the lithium metal storage layer (120) can be secured, and the charge / discharge capacity and energy density of the lithium metal battery can be further improved.

[0078] According to exemplary embodiments, the silicon oxide particle (122) may include lithium silicate. For example, at least a portion of the surface of the silicon oxide particle (122) may be formed of lithium silicate (Li) by an initial formation process. y SiO x ) can be oxidized.

[0079] Accordingly, lithium metal can be deposited and desorbed on the lithium silicate by charging and discharging. For example, the surface of the silicon oxide particle (122) can have an overall low potential due to lithium silicate on the surface of the silicon oxide particle (122), and lithium metal can grow uniformly on the surface of the silicon oxide particle (122).

[0080] In some embodiments, at a SOC100% state, the lithium content (M1) of the lithium metal deposited in the lithium metal storage layer (120) Li ) lithium content (M2) present as lithium silicate in the lithium metal storage layer (120) Li ) of the ratio (M2) Li / M1 Li ) can be greater than 0.9 based on the number of moles.

[0081] For example, the above molar ratio (M2 Li / M1 Li ) may be the molar ratio of lithium converted to lithium silicate in the initial Martian process and lithium newly deposited as lithium metal within the lithium metal storage layer (120) during the second charge.

[0082] As lithium metal is uniformly formed on lithium silicate within the above range, lithium metal can be more stably deposited within the lithium metal storage layer (120). For example, when the molar ratio of lithium contained in lithium silicate to the molar ratio of the deposited lithium metal is less than 0.9, an additional oxidation / reduction reaction may occur between lithium ions and silicon oxide particles (122). In addition, lithium ion crystals may be excessively formed on the surface of the silicon oxide particles (122), which may cause an internal short circuit.

[0083] For example, the above molar ratio (M2 Li / M1 Li ) can be 0.9 to 2.0, 0.9 to 1.6 or 0.9 to 1.5.

[0084] In some embodiments, lithium (M2) contained in the lithium metal storage layer (120) at SOC0% Li ) Lithium (M2) contained in the lithium metal storage layer (120) at SOC100% state Li +M1 Li ) molar ratio ((M2) Li +M1 Li ) / M2 Li ) may be less than or equal to 2.2.

[0085] Within the above range, the electrochemical stability of the electrode (130) for a lithium metal battery can be further improved while the lithium metal storage layer (120) has a low potential, and the growth of lithium dendrites can be further suppressed.

[0086] In some embodiments, the lithium metal storage layer (120) may further include a binder (128) and a conductive material (126).

[0087] For example, the binder (128) may include an organic binder such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, etc.; an aqueous binder such as styrene-butadiene rubber (SBR).

[0088] A conductive material (126) may be included to promote electron transfer. For example, the conductive material may include a carbon-based conductive material such as graphite, carbon black, graphene, carbon nanotubes, and / or a metal-based conductive material including a perovskite material such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0089] According to exemplary embodiments, the electrode (130) for a lithium metal battery may further include an electrode current collector (125). The lithium metal storage layer (120) may be disposed on at least one surface of the electrode current collector (125).

[0090] The electrode current collector (125) may include gold, stainless steel, nickel, aluminum, iron, titanium, copper or an alloy thereof, for example, copper or a copper alloy.

[0091] FIG. 3 is a schematic process flow diagram illustrating a method for manufacturing silicon oxide particles according to exemplary embodiments. Hereinafter, the method for manufacturing silicon oxide particles will be described with reference to FIG. 3.

[0092] Referring to FIG. 3, a silicon precursor can be mixed with an alkaline earth metal or carbon compound to form a mixture (e.g., step S10).

[0093] The above silicon precursor may have a porous structure. For example, the porosity of the silicon oxide particles can be controlled by controlling the porosity and pore size of the silicon precursor.

[0094] In some embodiments, the silicon precursor may comprise SiO2. The silicon precursor may be reduced by reaction with an alkaline earth metal or carbon. Accordingly, the oxygen and silicon composition ratio of the silicon oxide particles may be controlled as oxygen is removed from the crystal structure of the silicon precursor.

[0095] In some embodiments, the alkaline earth metal may include magnesium, calcium, strontium, and barium. For example, magnesium (Mg) may be used as the alkaline earth metal. Magnesium has an appropriate reactivity with SiO2, which may further improve processability and efficiency.

[0096] In some embodiments, the carbon compound may include carbon black such as Super-P, Super-C60, amorphous carbon compounds, carbon nanotubes, graphene, etc.

[0097] In one embodiment, the alkaline earth metal and carbon compound may be used in powder form. Accordingly, the contact area with the silicon precursor increases, allowing the alkaline earth metal or carbon compound to appropriately react over the entire surface of the silicon precursor.

[0098] In some embodiments, the ratio of the content of the silicon precursor to the content of the alkaline earth metal or carbon compound in the mixture may be 4 times or more, 5 times or more, 7 times or more, or 12 times or less, 11 times or less, or 10 times or less by weight.

[0099] The above mixture can be heat treated (e.g., step S20). The heat treatment process can reduce the silicon precursor and deoxygenate it.

[0100] In some embodiments, the heat treatment may be performed in an inert atmosphere, for example, a nitrogen or argon atmosphere.

[0101] In some embodiments, the heat treatment temperature may be between 500°C and 1,000°C. Within this range, the silicon precursor can be appropriately reduced while preventing melting of the silicon precursor. In one embodiment, the heat treatment time may be between 30 minutes and 4 hours.

[0102] The amount of reduction of the silicon precursor can be controlled by adjusting the content of alkaline earth metal and carbon compound, powder size, heat treatment temperature and time, etc.

[0103] In one embodiment, the heat-treated mixture may be mixed with an acid (e.g., step S30).

[0104] By-products or by-products such as metal oxides (e.g., MgO, etc.) formed on silicon oxide particles by acid can be more easily removed.

[0105] In some embodiments, the acid may include acetic acid (CH3COOH), hydrochloric acid (HCl), sulfuric acid (H2SO4), phosphoric acid (H3PO4), nitric acid (HNO3), and the like.

[0106] The above heat-treated mixture can be washed and dried to obtain silicon oxide particles (e.g., step S40).

[0107] Washing can be performed using water or an alcohol-based solvent. In some embodiments, when the heat-treated mixture is mixed with an acid, washing can be performed until the mixture becomes neutral.

[0108] The drying process may be performed at a temperature of 20°C to 100°C. In one embodiment, the drying process may be performed sequentially by a convection drying process and a vacuum drying process.

[0109] By the above-described manufacturing method, the above-described silicon oxide particles can be obtained. The molar ratio of oxygen to silicon of the silicon oxide particles can be 1.5 or more and less than 2.0.

[0110] Hereinafter, a lithium metal battery including the electrode for the lithium metal battery described above will be described with reference to FIGS. 4 and 5.

[0111] Referring to FIGS. 4 and 5, the lithium metal battery may include a positive electrode (100) and an electrode (130) for a lithium metal battery facing the positive electrode (100).

[0112] In one embodiment, the positive electrode (100) may be a lithium metal electrode.

[0113] In one embodiment, the positive electrode (100) may include a positive electrode active material layer (110) formed by applying a positive electrode active material to a positive electrode current collector (105).

[0114] For example, a positive electrode slurry can be prepared by mixing and stirring a positive electrode active material with a positive electrode binder, a conductive agent, and / or a dispersing agent in a solvent. The positive electrode slurry can be coated on at least one surface of a positive electrode current collector (105), and then dried and rolled to prepare a positive electrode (100).

[0115] The positive electrode current collector (105) may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector (105) may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver.

[0116] As an example of a positive electrode active material, it may include one or more compounds selected from a lithium iron phosphate compound, a lithium cobalt oxide, a lithium manganese oxide, a lithium nickel oxide, or a lithium composite oxide.

[0117] In one embodiment, the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or lithium manganese oxide such as LiMnO3, LiMn2O3 and LiMnO2; lithium copper oxide (Li2CuO2); LiV3O8, V2O 5　 It may include vanadium oxides such as Cu2VO7, lithium iron phosphate oxides such as LiFePO4, etc.

[0118] In some embodiments, the positive electrode active material may include a compound represented by the following chemical formula 1.

[0119] [Chemical Formula 1]

[0120] Li a Ni b M 1-b O2

[0121] In chemical formula 1, 0.95≤a≤1.08, b is b≥0.5, and M may be at least one element among Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Ba, and Sr.

[0122] In one embodiment, the positive electrode active material includes nickel (Ni) and may further include at least one of cobalt (Co) and manganese (Mn). For example, a nickel-cobalt-manganese (NCM) lithium oxide may be used as the positive electrode active material.

[0123] For example, nickel (Ni) can be provided as a metal associated with the capacity of lithium secondary batteries. While a higher nickel content can improve the capacity and output of a lithium secondary battery, excessive nickel content can shorten its lifespan and compromise mechanical and electrical stability.

[0124] In one embodiment, the conductivity or resistance of a lithium secondary battery can be improved by cobalt (Co), and the mechanical and electrical stability of a lithium secondary battery can be improved by manganese (Mn).

[0125] The chemical structure represented by Chemical Formula 1 represents the bonding relationship contained within the lattice structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M may serve as the main active element of the positive electrode active material. Chemical Formula 1 is provided to express the bonding relationship of the main active element and should be understood as a formula encompassing the introduction and substitution of additional elements.

[0126] In one embodiment, auxiliary elements may be further included in addition to the main active element to enhance the chemical stability of the positive electrode active material or the crystal structure. The auxiliary elements may be incorporated into the crystal structure to form bonds, and in this case, it should be understood that they are also included within the chemical structure range represented by Chemical Formula 1.

[0127] Materials substantially identical to or similar to the above-described materials may be used as the positive electrode binder and conductive material. For example, a PVDF-based binder may be used as the positive electrode binder. In this case, the amount of binder for forming the positive electrode active material layer (110) may be reduced, while the amount of positive electrode active material may be relatively increased, thereby improving the output and capacity of the secondary battery.

[0128] In some embodiments, a separator (140) may be interposed between the positive electrode (100) and the lithium metal battery electrode (130). The separator (140) may include a porous polymer film made of a polyolefin polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, or the like. The separator (140) may also include a nonwoven fabric formed of high-melting-point glass fibers, polyethylene terephthalate fibers, or the like.

[0129] According to exemplary embodiments, an electrode cell is defined by a cathode (100), a lithium metal battery electrode (130), and a separator (140), and a plurality of the electrode cells may be stacked to form an electrode assembly (150) in the form of, for example, a jelly roll. For example, the electrode assembly (150) may be formed by winding, stacking, folding, or the like of the separator (140).

[0130] An electrode assembly (150) may be housed within a case (160) together with an electrolyte to define a lithium metal battery. According to exemplary embodiments, a non-aqueous electrolyte may be used as the electrolyte.

[0131] The non-aqueous electrolyte may include a lithium salt as an electrolyte and an organic solvent. The lithium salt may be, for example, Li + X - is expressed as and the anion of the lithium salt (X - ) as F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 -, (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - Examples include:

[0132] Examples of the organic solvent that can be used include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran. These may be used alone or in combination of two or more.

[0133] In some embodiments, a solid electrolyte layer may be interposed between the positive electrode (100) and the electrode (130) for a lithium metal battery. The solid electrolyte layer may include a sulfide-based electrolyte, an oxide-based electrolyte, or a polymer electrolyte.

[0134] In this case, the lithium metal battery may not include a separator and an electrolyte. The solid electrolyte layer substantially functions as a separator and can prevent a short circuit between the positive electrode (100) and the lithium metal battery electrode (130). In addition, the solid electrolyte layer allows lithium ions to move between the positive electrode (100) and the lithium metal battery electrode (130).

[0135] The above sulfide-based solid electrolyte may include an LPS-based solid electrolyte containing Li, P, and S, an LGPS-based solid electrolyte containing Li, P, Ge, and S, or an LSiPSCl-based solid electrolyte containing Li, Si, P, S, and Cl.

[0136] For example, Li2S-P2S5, Li as a sulfide-based solid electrolyte 10 GeP2S 12 , Li 10 SnP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 , Li 10 (Ge 0.5 Sn 0.5 )P2S 12 , Li 10 (Si 0.5 Sn 0.5 )P2S 12 , Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li9P3S9O3, Li 10.35 Ge 1.35 P 1.65 S 12 , Li 10.35 Si 1.35 P 1.65 S 12 , Li 9.81 Sn 0.81 P 2.19 S12 , Li 9.42 Si 1.02 P 2.1 S 9.96 O 2.04 , Li6PS5Cl, etc. can be used.

[0137] The above oxide-based solid electrolyte may include a metal oxide or an ion-conducting compound containing oxygen.

[0138] Examples of the above metal oxides include Al2O3, ZnO2, Ce2O3, TiO2, ZrO2, HfO2, MnO2, MgO, WO 2, Examples include V2O5.

[0139] As an example of the above ion conducting compound, LLZO type compound (e.g., Li7La3Zr2O 12 ) and other garnet compounds; LLTO compounds (e.g., Li 3x La 2 / 3-x TiO3, 0 <x<3) 등의 페로브스카이트(perovskite)계 화합물; Li 1+x Al x Ge 2-x (PO4)3(0 <x<2), Li 1+x Al x Ti 2-x (PO4)3(0 <x<2), Li 1+x Ti 2-x-y Al x Si y (PO4) 3-y (0≤x≤1, 0 <y≤1), LAGP계 화합물, LATP계 화합물, LiAl x Zr 2-x (PO4)3(0≤x≤1, 0≤y≤1), LiTi x Zr 2-x NASICON compounds such as (PO4)3(0≤x≤1, 0≤y≤1); LIPON compounds; Li6La2CaTa2O 12 ; Li6La2ANb2O 12 (A is Ca or Sr); Li2Nd3TeSbO 12 , Li3BO 2.5 N0.5 ; Li9SiAlO8, etc. can be mentioned.

[0140] The polymer electrolyte may include polyether polymers such as poly(ethylene oxide) and poly(propylene oxide), polycarbonate polymers such as poly(ethylene carbonate), poly(propylene carbonate), and poly(trimethylene carbonate), and polyester polymers such as poly(ε-caprolactone) and poly(1,4-butylene adipate).

[0141] As illustrated in FIG. 4, electrode tabs (positive electrode tab and negative electrode tab) may protrude from the positive electrode collector (105) and negative electrode collector (125) belonging to each electrode cell and extend to one side of the case (160). The electrode tabs may be fused together with the one side of the case (160) to form electrode leads (positive electrode lead (107) and negative electrode lead (127)) that extend or are exposed to the outside of the case (160).

[0142] The above lithium secondary battery can be manufactured in a cylindrical, square, pouch or coin shape using, for example, a can.

[0143] Hereinafter, preferred embodiments are presented to help understand the present disclosure, but these embodiments are only illustrative of the present disclosure and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0144]

[0145] Example 1

[0146] (1) Preparation of silicon oxide particles

[0147] 8 g of diatomaceous earth (Diatomite, SiO2, flux-calcined, Merck) classified to a size of 10 μm or less and 1 g of magnesium powder (Mg>99%, Merck) were mixed in a mortar and pestle in a glove box. The mixed powder was placed in a stainless steel sealed reactor with an inner volume of 20 ml and sealed. The mixed powder was heat-treated in a synthesis furnace under an Ar atmosphere at 675°C for 2 hours, and the heat-treated powder was stirred in 1 L of 1 M HCl for 24 hours. The powder was washed with distilled water in a pressure reducing filter until it became neutral. The washed powder was dried in a convection oven at 80°C for 24 hours, and then dried in a vacuum oven at 80°C for 24 hours to obtain silicon oxide particles.

[0148] Afterwards, the composition of the silicon oxide particles was measured through XPS (X-ray photoelectron spectroscopy) analysis using a photoelectron spectrometer (Sigma probe, Thermo Scientific). The measured composition of the silicon oxide particles was SiO 1.6 It was.

[0149] (2) Porosity evaluation

[0150] The SEM (scanning electron microscope) image of the above diatomaceous earth powder was taken using a scanning electron microscope (JSM-7000F, JEOL). Thereafter, the SEM image of the silicon oxide particles manufactured using the above diatomaceous earth was taken using a scanning electron microscope.

[0151] Fig. 6 is an SEM image of diatomaceous earth powder. Fig. 7 is a cross-sectional SEM image of silicon oxide particles.

[0152] Referring to FIGS. 6 and 7, it can be confirmed that pores are formed on the surface and inside of the silicon oxide particles when silicon oxide particles are manufactured using diatomaceous earth having a porous structure.

[0153] (3) Porosity measurement

[0154] The volume of pores formed within the silicon oxide particles was measured using the Mercury Intrusion Prosimetry (MIP) method using a mercury intrusion device (AUTOPORE V, Micrometrics). The porosity of the silicon oxide particles was calculated as the percentage of the value obtained by dividing the measured pore volume by the volume of the silicon oxide particles.

[0155] (4) Manufacturing of electrodes for lithium metal batteries

[0156] The above silicon oxide particles (SiO 1.6 ), a conductive agent (Super-P, Timcal), and a binder (PVDF, KF-9700, Kureha) were mixed in a weight ratio of 9.0:0.5:0.5. After that, NMP (N-Methyl-2-pyrrolidone, Merck) solvent was added so that the solid content ratio became 35%, and then mixed using a mixer (ar-100, Thinky Mixer) to prepare a slurry.

[0157] The above slurry was coated on a copper foil having a thickness of 8 μm using a doctor blade. The slurry was coated so that the thickness of the unrolled electrode after final drying was 53 μm.

[0158] The slurry-coated copper foil was dried in a convection oven at 80°C for 24 hours and then dried in a vacuum oven at 80°C for 24 hours to manufacture an electrode for a lithium metal battery.

[0159] The pore volume of the lithium metal storage layer was measured using the MIP method using a mercury intrusion device (AUTOPORE V, Micrometrics). The porosity of the lithium metal storage layer was calculated as the percentage of the measured pore volume divided by the volume of the lithium metal storage layer.

[0160] (5) Manufacturing of coin cells

[0161] A coin cell was manufactured using lithium metal as the electrode for the lithium metal battery manufactured above and the counter electrode.

[0162] Specifically, the electrode and counter electrode were each notched into a circular shape, and a circular polyethylene separator (13 μm thick) was interposed between the electrode and counter electrode to manufacture an electrode assembly.

[0163] The above electrode assembly was placed in a coin-shaped outer case, and an electrolyte was injected to manufacture a coin-shaped lithium secondary battery. The electrolyte used was 1 M LiPF6 dissolved in an EC / EMC (30:70 v / v) mixed solvent.

[0164] (6) Potential measurement

[0165] The manufactured cell was initially charged and discharged within the voltage range of 2.5 V to 4.2 V at a C-rate of 0.2 C. Subsequently, charge and discharge were performed within the voltage range of 2.5 V to 4.2 V at a C-rate of 0.5 C, and the voltage changes during charging and discharging were measured. The measured results are shown in Fig. 8 below.

[0166] Electrodes and coin cells for lithium metal batteries were manufactured using the same method, except that silicon monoxide (SiO) was used instead of the silicon oxide particles manufactured in (1) above. Thereafter, charge and discharge were performed using the same method, and the voltage changes during charging and discharging were measured. The measured results are shown in Fig. 9 below.

[0167] Referring to Fig. 8, when an electrode for a lithium metal battery was manufactured using the above-described silicon oxide particles, the voltage during charging was 0 V or less compared to the redox voltage of lithium, and the voltage during discharging was 0.2 V or less. Therefore, it can be seen that the voltage does not increase in magnitude during the charge and discharge process, and lithium metal is stably deposited and desorbed. It can be confirmed that the capacity of the battery is developed by the deposition and desorption of lithium metal, not by the oxidation and reduction reaction of silicon oxide.

[0168] Referring to Figure 9, when a lithium metal battery electrode was manufactured using silicon monoxide (SiO), the potential changed significantly during charge and discharge. Therefore, it can be confirmed that the battery capacity is developed as silicon oxide, which reacts with lithium ions during the charging process, is reduced back to silicon monoxide during the discharge process.

[0169] Examples 2 and 3

[0170] An electrode and a coin cell for a lithium metal battery were manufactured in the same manner as in Example 1, except that the porosity of the silicon oxide particles and the lithium metal storage layer were changed as shown in Table 1 below.

[0171] The porosity of the silicon oxide particles was controlled by varying the porosity of the diatomaceous earth, heat treatment time, mixing amount of magnesium powder, acid washing time, etc. The porosity of the lithium metal storage layer was controlled by varying the solid content ratio of the slurry, drying time, etc.

[0172] Comparative Example 1

[0173] Silicon oxide particles (SiO) were prepared in the same manner as in Example 1, except that diatomaceous earth that does not form pores was used. 1.6 ) were manufactured. The silicon oxide particles had a non-porous structure. Thereafter, an electrode for a lithium metal battery and a coin cell were manufactured using the same method as in Example 1.

[0174] Comparative Example 2

[0175] A coin cell was manufactured in the same manner as in Example 1, except that only copper foil was used as an electrode for a lithium metal battery without forming a lithium metal storage layer.

[0176]

[0177] Silicon oxide particle porosity (%) Lithium metal storage layer porosity (%) Example 16080 Example 23050 Example 33035 Comparative examples 1-25

[0178] Experimental Example 1: Measurement of Volume Change Rate

[0179] The initial volume of the electrode for the lithium metal battery manufactured above was measured.

[0180] After this, the charge / discharge capacity at room temperature was 1 mAh / cm 2 , 3mAh / cm 2 , 4mAh / cm 2 , 7 mAh / cm 2 The volume of the electrode for a lithium metal battery was measured at each charge / discharge cycle while increasing the volume. The increase rate of the measured volume with respect to the initial volume was calculated as a percentage.

[0181] The measurement results are shown in Table 2 below.

[0182] Volume change rate (%) 1mAh / cm 2 3mAh / cm 2 4mAh / cm 2 7mAh / cm 2 Example 101225 Example 20101439 Example 33172453 Comparative Example 1217391124 Comparative Example 294263107

[0183]

[0184] Experimental Example 2: Capacity Retention Rate

[0185] For the coin cell manufactured above, charge (CC-CV 0.2 C, 4.2 V cut-off) and discharge (CC 0.2 C, 2.5 V cut-off) were performed as one cycle at room temperature, and the discharge capacity was measured for each cycle.

[0186] For the coin cells manufactured above, the capacity retention was evaluated by calculating the ratio of the discharge capacity at each cycle to the initial discharge capacity as a percentage. If the capacity retention was less than 10%, it was indicated as "-".

[0187] The measurement results are shown in Table 3 below.

[0188] Capacity retention rate (%) 10 times 20 times 30 times 40 times Example 199.198.6 98.197.7 Example 298.3 96.293.890.1 Example 398.0 94.891.888.1 Comparative example 130.211.1--Comparative example 298.890.153.5-

[0189] Referring to Tables 2 and 3, the coin cells of the examples showed small changes in electrode volume even when charge and discharge were repeated, and the charge and discharge capacity was maintained for a long period of time.

[0190] However, the electrode of Comparative Example 1, which used silicon oxide particles without a porous structure, showed a significant increase in volume and a decrease in capacity retention. In addition, Comparative Example 2, which used only a copper current collector as an electrode for a lithium metal battery, showed a significant increase in volume even in the initial cycle, and the capacity decreased rapidly after the 20th cycle as inactive lithium continued to increase due to charge and discharge.

Claims

1. An electrode for a lithium metal battery, comprising a lithium metal storage layer including silicon oxide particles having a porous structure, wherein the molar ratio of oxygen to silicon among the silicon oxide particles is 1.5 or more and less than 2.

0.

2. In claim 1, the silicon oxide particles are SiO x , and an electrode for a lithium metal battery, where 1.5≤x<2.

3. An electrode for a lithium metal battery according to claim 1, wherein each of the silicon oxide particles has a porosity of 10% to 90%.

4. An electrode for a lithium metal battery according to claim 1, wherein the porosity of the lithium metal storage layer is 40% to 95%.

5. An electrode for a lithium metal battery according to claim 1, wherein the size of the pores formed in the silicon oxide particles is 10 nm to 1 μm.

6. An electrode for a lithium metal battery according to claim 1, wherein the size of the pores formed in the lithium metal storage layer is 10 nm to 10 μm.

7. An electrode for a lithium metal battery according to claim 1, wherein the maximum value of the voltage of the lithium metal storage layer measured during the charging process after initial charge / discharge (formation) is 0 V or less compared to the redox voltage of lithium.

8. In claim 1, further comprising an electrode current collector, An electrode for a lithium metal battery, wherein the lithium metal storage layer is disposed on at least one surface of the electrode current collector.

9. An electrode for a lithium metal battery according to claim 1, wherein the silicon oxide particles include lithium silicate.

10. An electrode for a lithium metal battery according to claim 9, wherein, in a state of SOC 100%, the molar ratio of lithium existing as lithium silicate within the lithium metal storage layer to lithium of the lithium metal deposited within the lithium metal storage layer is 0.9 or more.

11. An electrode for a lithium metal battery according to claim 9, wherein the molar ratio of lithium contained in the lithium metal storage layer at a SOC100% state to lithium contained in the lithium metal storage layer at a SOC0% state is 2.2 or less.

12. A lithium metal battery comprising an electrode for a lithium metal battery according to claim 1.

13. A step of forming a mixture by mixing a silicon precursor having a porous structure with an alkaline earth metal or carbon; a step of heat treating the above mixture; and A step of washing the heat-treated mixture to obtain silicon oxide particles is included. A method for producing silicon oxide particles for a lithium metal battery, wherein the molar ratio of oxygen to silicon of the silicon oxide particles is 1.5 or more and less than 2.

0.

14. A method for producing silicon oxide particles for a lithium metal battery, further comprising a step of mixing the heat-treated mixture with an acid before washing the heat-treated mixture according to claim 13.

15. A method for producing silicon oxide particles for a lithium metal battery, wherein the silicon precursor is SiO2 according to claim 13.

16. A method for producing silicon oxide particles for a lithium metal battery, wherein the alkaline earth metal in claim 13 is magnesium (Mg).

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