A negative electrode material, a method for manufacturing the same, a negative electrode containing the same, and a lithium secondary battery containing the negative electrode.

Abstract

The present invention relates to an anode material having an inorganic coating layer, a manufacturing method thereof, an anode including the anode material, and a lithium secondary battery including the anode, the anode material including silicone oxide particles; and a core including one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide, and an inorganic coating layer surrounding the core, the inorganic coating layer including a metal phosphate, a metal phosphate derivative, or a lithium oxide-non-metal phosphate complex. The present invention provides an anode material, a manufacturing method thereof, an anode including the anode material, and a lithium secondary battery including the anode.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0047660 dated April 18, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a negative electrode material having an inorganic coating layer, a method for manufacturing the same, a negative electrode containing the negative electrode material, and a lithium secondary battery containing the negative electrode. [Background technology]

[0003] In recent years, the application areas of lithium-ion batteries have rapidly expanded beyond power supply for electronic devices such as electrical, electronic, telecommunications, and computers to include power storage and supply for large-area devices such as automobiles and power storage devices. Consequently, there is an increasing demand for high-capacity, high-output, and highly stable secondary batteries.

[0004] Lithium secondary batteries are generally manufactured by applying a slurry of a positive electrode material capable of inserting and removing lithium ions, a negative electrode material capable of intercalating and deintercalating lithium ions, and a binder and conductive material to a positive electrode current collector and a negative electrode current collector, respectively, and removing the solvent by heat or other means. These electrodes are then stacked on both sides of a separator to form electrode current collectors of a predetermined shape, and these electrode current collectors and a non-aqueous electrolyte are then inserted into a battery case.

[0005] Graphite-based anode materials, a typical anode material, exhibit excellent structural stability during lithium insertion and removal, and stable capacity retention characteristics even over long cycles. However, their low theoretical capacity (350 mAh / g for LiC6) makes them unsuitable as materials for the high capacity and high power currently required. Therefore, silicone-based anode materials such as silicone and silicone oxides are being considered due to their low reduction potential with lithium, abundant reserves, and theoretical capacity (2700-4200 mAh / g for LiC6) which is more than 10 times higher than graphite. 4.4Due to (Si), it has attracted attention as a negative electrode material for next-generation lithium secondary batteries. However, despite such advantages, silicon-based negative electrode materials consume about three times as much lithium as graphite-based negative electrode materials, and due to volume expansion and surface side reactions during charge and discharge of lithium secondary batteries employing them, a large amount of the lithium inserted into the negative electrode during initial charging cannot return to the positive electrode, resulting in a problem of a large initial irreversible capacity.

[0006] In addition, particularly for silicon oxide (SiOx) particles, various methods have been tried to improve the initial efficiency by doping with Mg or prelithiation of SiOx particles with Li in order to solve the problem of initial efficiency due to irreversible reactions of Li ions. However, when using this to produce a negative electrode material slurry by an aqueous process, the lithium compound generated inside the prelithiated silicon oxide particles reacts with H2O to generate LiOH by-products, thereby reducing the viscosity of the slurry, generating hydrogen, deteriorating the coating characteristics of the slurry, and as a result, there is a problem of a decrease in the adhesion force between the negative electrode material layer and the current collector.

[0007] Therefore, in a situation where there is a need to develop a negative electrode material that is excellent in initial capacity and capacity retention rate, has little change in viscosity when producing a negative electrode material slurry by an aqueous process, suppresses hydrogen generation, and suppresses volume expansion during charge and discharge of the negative electrode using it.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made to solve the above-described problems of the prior art, and aims to provide a negative electrode material that is excellent in initial capacity and capacity retention rate, has almost no viscosity change when producing a negative electrode material slurry by an aqueous process, and suppresses hydrogen generation.

[0010] Further, the present invention aims to provide a method for producing the negative electrode material.

[0011] Further, the present invention aims to provide a negative electrode including the negative electrode material.

[0012] Further, the present invention aims to provide a lithium secondary battery including the negative electrode.

Means for Solving the Problems

[0013] In order to solve the above problems, the present invention provides a negative electrode material, a method for producing the same, a negative electrode including the same, and a lithium secondary battery.

[0014] (1) The present invention provides a negative electrode material including: a core including silicon oxide particles and one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide; and an inorganic coating layer surrounding the core, the inorganic coating layer including a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate composite, the metal phosphate being at least one selected from Li3PO4, Li4P2O7, Li9Al3(P2O7)3(PO4)2, Co3(PO4)2, Co3(PO3)2, GaPO4, Ga(PO3)3, FePO4, Fe(PO3)3, Mg3(PO4)2, Mg(PO3)2, Ca3(PO4)2, Ca(PO3)2, Be3(PO4)2, Be(PO3)2, Pb3(PO4)2, Pb(PO3)2, LaPO4, La(PO3)3, YPO4, Y(PO3)3, VOPO4, Zr3(PO4)2, Zr(PO3)2, and Al(PO3)3, and the metal phosphate derivative including at least one selected from a unit derived from a metal phosphate, a unit derived from boric acid, and a unit derived from lithium borate.

[0015] (2) The present invention provides the negative electrode material described in (1) above, wherein the silicone oxide particles include a carbon coating layer on their surface.

[0016] (3) The present invention relates to the metal phosphate derivative being [M(H n PO4) m OB(OH)2], [(M(H n PO4) m O)2-B(OH)], or [(M(H n PO4) m The negative electrode material described in (1) or (2) above is O)3-B], where M is at least one selected from Co, Ga, Fe, Mg, Ca, Be, Pb, La, Y, Zr, and Al, n is 1 or 2, and m is 1, 2, or 3.

[0017] (4) The present invention provides the negative electrode material according to (1) or (2) above, wherein the lithium oxide-nonmetallic phosphate composite is Li2O-BPO4.

[0018] (5) The present invention provides a negative electrode material according to any one of (2) to (4) above, wherein the thickness of the carbon coating layer is 1 nm to 1 μm.

[0019] (6) The present invention provides a negative electrode material according to any one of (1) to (5) above, wherein the thickness of the inorganic coating layer is 0.1 nm to 1 μm.

[0020] (7) The present invention provides a negative electrode material according to any one of (1) to (6) above, wherein the inorganic coating layer further comprises a cationic surfactant.

[0021] (8) The present invention provides the negative electrode material described in (7) above, wherein the cationic surfactant is cetrimonium bromide.

[0022] (9) The present invention provides a method for producing a negative electrode material according to any one of (1) to (8) above, comprising the steps of: (S1) mixing silicone oxide particles and lithium powder and heat-treating them to form core particles; (S2) reacting the core particles with a coating layer forming composition; and (S3) firing at 700°C to 900°C, wherein the coating layer forming composition comprises a metal phosphate precursor, or a metal phosphate precursor and at least one selected from lithium hydroxide, boric acid, and lithium borate, or a nonmetallic phosphate, boric acid, and lithium borate.

[0023] (10) The present invention provides a method for producing the negative electrode material described in (9), wherein the reaction in step S2 is carried out by mechanical grinding of the core particles and the coating layer forming composition in a solvent-free environment.

[0024] (11) The present invention provides a method for producing a negative electrode material as described in (9), wherein the reaction in step S2 is carried out by mixing core particles and a coating layer forming composition in a solvent, and the coating layer forming composition further comprises at least one selected from an organic solvent and a cationic surfactant.

[0025] (12) The present invention provides a method for producing a negative electrode material according to any one of (9) to (11) above, wherein the metal phosphate precursor is at least one selected from the group consisting of Co(H2PO4)2, Ga(H2PO4)3, Fe(H2PO4)3, Mg(H2PO4)2, Ca(H2PO4)2, Be(H2PO4)2, Pb(H2PO4)2, La(HPO4)3, VO(H2PO4)2, Y2(HPO4)3, Zr(HPO4)2, and Al(H2PO4)3.

[0026] (13) The present invention provides a method for manufacturing a negative electrode material according to any one of (9) to (11), wherein the lithium hydroxide is LiOH.

[0027] (14) The present invention provides a method for producing a negative electrode material according to any one of (9) to (11), wherein the lithium borate is at least one selected from Li3BO3 and Li2B4O7.

[0028] (15) The present invention provides a method for manufacturing a negative electrode material according to any one of (9) to (11), wherein the nonmetallic phosphate is NH4H2PO4.

[0029] (16) The present invention provides a negative electrode comprising a conductive metal current collector and a negative electrode material layer provided on at least one surface of the current collector, wherein the negative electrode material layer comprises the negative electrode material described in any one of (1) to (8), and the negative electrode material comprises lithium ions diffused by pre-lithification.

[0030] (17) The present invention provides a lithium secondary battery comprising the negative electrode described in (16) above, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. [Effects of the Invention]

[0031] The anode material according to the present invention comprises a core containing silicone oxide particles and a lithium-containing compound, and an inorganic coating layer surrounding the core. As a result, even when manufactured as an aqueous anode material slurry, the viscosity reduction of the slurry and the generation of hydrogen due to LiOH by-products are suppressed, resulting in excellent initial capacity and capacity retention. Furthermore, compared to ordinary aqueous anode material slurries containing silicone oxide particles, viscosity changes are less and hydrogen generation is reduced. Therefore, slurry coating defects and adhesion reduction due to slurry viscosity reduction can be suppressed, resulting in excellent storage stability.

[0032] Furthermore, the anode according to the present invention includes an anode material layer containing a pre-lithified anode material, which allows for excellent initial efficiency, suppression of anode volume expansion, and superior capacity retention and long-term stability. [Brief explanation of the drawing]

[0033] The following drawings attached to this specification are for illustrating specific embodiments of the present invention and, together with the above-described content of the invention, serve to provide a better understanding of the technical concept of the present invention. Therefore, the present invention should not be construed as being limited solely to the matters depicted in these drawings. [Figure 1] This is the XRD pattern of the pre-lithiumized Li-SiOx / C core particles produced in Example 2. [Figure 2] This is the XRD pattern of the unpre-lithiuminated SiOx / C core particles produced in Comparative Example 2. [Figure 3] This graph compares and analyzes the capacity retention rates of a half-cell using the negative electrode material manufactured in Example 2 and a half-cell using the negative electrode material of Comparative Example 1. [Figure 4] This graph compares and analyzes the capacity retention rates of a half-cell using the negative electrode material manufactured in Example 4 and a half-cell using the negative electrode material of Comparative Example 1. [Modes for carrying out the invention]

[0034] The present invention will now be described in more detail so that it can be easily understood.

[0035] The terms and words used in the description and claims of this invention should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​this invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0036] Anode material The present invention provides a silicone or silicone oxide-based anode material that includes an inorganic coating layer on its surface.

[0037] An anode material according to one embodiment of the present invention comprises a core containing silicone oxide particles and one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide, and an inorganic coating layer surrounding the core, wherein the inorganic coating layer contains a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetallic phosphate composite, and the metal phosphate is Li3PO4, Li4P2O7, Li9Al3(P2O7)3(PO4)2, Co3(PO4)2, Co3(PO3)2, GaPO4, Ga(PO3) 3, at least one selected from FePO4, Fe(PO3)3, Mg3(PO4)2, Mg(PO3)2, Ca3(PO4)2, Ca(PO3)2, Be3(PO4)2, Be(PO3)2, Pb3(PO4)2, Pb(PO3)2, LaPO4, La(PO3)3, YPO4, Y(PO3)3, VOPO4, Zr3(PO4)2, Zr(PO3)2, and Al(PO3)3, wherein the metal phosphate derivative comprises at least one selected from a unit derived from a metal phosphate, a unit derived from boric acid, and a unit derived from lithium borate.

[0038] Graphite-based anode materials are known as anode materials. Graphite-based anode materials exhibit excellent structural stability during lithium insertion and removal, and stable capacity retention characteristics even over long cycles. However, due to their low theoretical capacity (350mAh / g for LiC6), they are unsuitable as materials for the high capacity and high power currently required. Therefore, a material with a theoretical capacity approximately 10 times higher than graphite (~4200mAh / g for LiC6) is being considered. 4.4Silicones and silicone oxides containing Si are attracting attention. However, silicone-based anode materials consume about three times more lithium than graphite-based anode materials, resulting in a problem of increased irreversible capacity. To solve the problem of initial efficiency due to the irreversible reaction of lithium ions, methods are being tried to improve initial efficiency by prelithiation of Li. However, when manufacturing aqueous anode material slurries using prelithiated silicone-based anode materials, the lithium compounds generated by prelithiation react with H2O to produce LiOH byproducts, increasing hydrogen generation, changing the viscosity of the slurry, degrading the slurry coating properties, and causing serious defects in the slurry coating. As a result, there is a risk of fatal problems such as a sudden decrease in capacity due to electrical short circuits with the current collector.

[0039] However, the anode material according to the present invention has a structure in which an inorganic coating layer is included on the surface of a core containing pre-lithified silicone oxide particles. Therefore, even when manufactured in an aqueous anode material slurry, the coating layer suppresses the decrease in slurry viscosity and hydrogen generation due to LiOH by-products, thereby preventing slurry coating defects and a decrease in adhesion strength, and enabling the anode to have excellent anode integrity and capacity retention.

[0040] The anode material according to the present invention will be described in detail below.

[0041] The negative electrode material according to one embodiment of the present invention comprises a core containing silicone oxide particles and one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide, and an inorganic coating layer surrounding the core, wherein the inorganic coating layer may contain a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetallic phosphate composite.

[0042] The core comprises silicone oxide particles and a lithium-containing compound.

[0043] Here, the core is obtained by mixing silicon oxide particles with lithium powder and then performing heat treatment, that is, it is formed by prelithiation of silicon oxide particles. The core includes silicon oxide particles and lithium silicate (Li2SiO3), lithium disilicate (Li2Si2O5), and lithium silicide (Li a Si, 0 < a ≤ 4.4), and one or more lithium-containing compounds selected therefrom.

[0044] The silicon oxide (SiOx, where x satisfies 0 < x ≤ 2) particles may have an amorphous structure, and the silicon oxide particles may have an average particle size (D 50 ) of 5 nm to 20 μm.

[0045] In addition, the silicon oxide particles may include a carbon coating layer on the surface. At this time, the thickness of the carbon coating layer may be 1 nm to 1 μm, or 1 nm to 100 nm.

[0046] Moreover, the negative electrode material includes an inorganic coating layer surrounding the core, and the inorganic coating layer may include a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate composite.

[0047] In addition, the thickness of the inorganic coating layer may be 0.1 nm to 1 μm.

[0048] The metal phosphate may be at least one selected from Li3PO4, Li4P2O7, Li9Al3(P2O7)3(PO4)2, Co3(PO4)2, Co3(PO3)2, GaPO4, Ga(PO3)3, FePO4, Fe(PO3)3, Mg3(PO4)2, Mg(PO3)2, Ca3(PO4)2, Ca(PO3)2, Be3(PO4)2, Be(PO3)2, Pb3(PO4)2, Pb(PO3)2, LaPO4, La(PO3)3, YPO4, Y(PO3)3, VOPO4, Zr3(PO4)2, Zr(PO3)2, and Al(PO3)3. Specifically, the metal phosphate may be at least one selected from Co3(PO4)2, Mg3(PO4)2, and Al(PO3)3.

[0049] Furthermore, the metal phosphate derivative may, for example, be a condensation reaction product of a metal phosphate precursor and boric acid, and specifically, the metal phosphate derivative may be [M(H n PO4) m OB(OH)2], [(M(H n PO4) m O)2-B(OH)], or [(M(H n PO4) m O)3-B], where m is at least one selected from Co, Ga, Fe, Mg, Ca, Be, Pb, La, Y, Zr, and Al, n is 1 or 2, and m may be 1, 2, or 3.

[0050] As yet another example, the metal phosphate derivative may be a reaction product of a metal phosphate precursor, boric acid, and lithium borate.

[0051] Furthermore, the lithium oxide-nonmetallic phosphate is a reaction product of a nonmetallic phosphate, boric acid, and lithium borate, and may specifically be Li2O-BPO4.

[0052] As yet another example, the coating layer may further contain a cationic surfactant, the cationic surfactant may be cetrimonium bromide.

[0053] Method for manufacturing negative electrode material The present invention provides a method for manufacturing the negative electrode material.

[0054] A method for producing a negative electrode material according to one embodiment of the present invention comprises the steps of: mixing silicone oxide particles and lithium powder and heat-treating them to form core particles (S1); reacting the core particles with a coating layer forming composition (S2); and firing at 700°C to 900°C (S3), wherein the coating layer forming composition may contain a metal phosphate precursor, or a metal phosphate precursor and at least one selected from lithium hydroxide, boric acid, and lithium borate, or a nonmetallic phosphate, boric acid, and lithium borate.

[0055] The method for manufacturing the negative electrode material according to one embodiment of the present invention will be described in more detail below, step by step.

[0056] (S1) Step Step (S1) is a step for producing pre-lithiumized core particles, which may be carried out by mixing silicone oxide particles and lithium powder and then heat-treating them.

[0057] Here, the silicone oxide particles are as described above.

[0058] Furthermore, the silicone oxide particles may include a carbon coating layer on their surface. In this case, the silicone oxide particles may have a carbon coating layer formed on their surface by heat-treating a carbon precursor to carbonize it.

[0059] In this case, the carbonization method can be a method commonly used in the industry, for example, either dry or wet mixing can be used. As the carbon precursor, a carbon-containing gas such as methane, ethane, propane, acetylene, or ethylene may be used, or a carbon precursor that is liquid at room temperature, such as toluene, may be vaporized and a vapor deposition method such as chemical vapor deposition (CVD) may be used. Furthermore, as amorphous carbon precursors, resins such as phenolic resin, naphthalene resin, polyvinyl alcohol resin, urethane resin, polyimide resin, furan resin, cellulose resin, epoxy resin, and polystyrene resin, as well as coal-based pitch, petroleum-based pitch, tar, or low molecular weight heavy oils can be used. Sucrose can also be used.

[0060] Furthermore, the mixing of the silicone oxide particles and lithium powder is not particularly limited as long as it is mixed uniformly, and can be carried out by conventional powder mixing methods in this industry. In this case, 100 parts by weight of the silicone oxide particles may be used as the basis for mixing with 1 to 15 parts by weight of lithium powder, specifically 3 to 10 parts by weight, or 5 to 10 parts by weight of lithium powder. In this case, it is possible to sufficiently ensure an increase in initial efficiency due to the pre-lithification of the silicone oxide, while reducing the volume reduction that is a trade-off with it.

[0061] Furthermore, the heat treatment can be performed at a temperature of less than 1000°C, specifically 900°C or less, or at a temperature of 500-1000°C, 600-1000°C, 500-900°C, or 600-900°C. If the heat treatment temperature exceeds 1000°C, the Si crystals in the silicon oxide particles tend to increase, which may lead to problems in controlling volume expansion during lithium insertion and removal.

[0062] (S2) Step Step (S2) is a step for applying (coating) a coating layer-forming composition to the surface of the core particles, and can be carried out by reacting the core particles produced in step (S1) with the coating layer-forming composition, in which case the reaction may be carried out by wet coating or dry coating.

[0063] Specifically, the reaction between the core particles and the coating layer forming composition may be carried out by mechanically grinding the core particles and the coating layer forming composition in a solvent-free environment. In this case, a coating layer can be formed by sufficient contact between solid-phase reactants in the absence of a solvent.

[0064] As another example, the reaction between the core particles and the coating layer forming composition may be carried out by mixing the core particles and the coating layer forming composition in a solvent. In this case, the coating layer forming composition may further contain at least one selected from an organic solvent and a cationic surfactant.

[0065] The coating layer forming composition may contain a metal phosphate precursor, or a metal phosphate precursor and at least one selected from lithium hydroxide, boric acid, and lithium borate, or it may contain a nonmetallic phosphate, boric acid, and lithium borate.

[0066] The metal phosphate precursor may be at least one selected from the group consisting of Co(H2PO4)2, Ga(H2PO4)3, Fe(H2PO4)3, Mg(H2PO4)2, Ca(H2PO4)2, Be(H2PO4)2, Pb(H2PO4)2, La(HPO4)3, VO(H2PO4)2, Y2(HPO4)3, Zr(HPO4)2, and Al(H2PO4)3, and more specifically, at least one selected from the group consisting of Co(H2PO4)2, Mg(H2PO4)2, and Al(H2PO4)3.

[0067] Furthermore, the lithium hydroxide may be LiOH.

[0068] Furthermore, the lithium borate may be at least one selected from Li3BO3 and Li2B4O7.

[0069] Furthermore, the nonmetallic phosphate may be NH4H2PO4.

[0070] On the other hand, in the reaction between the core particles and the coating layer forming composition for applying (coating) the coating layer forming composition to the surface of the core particles, the coating layer forming composition may be used in an amount such that the active ingredient in the coating layer forming composition is 0.1 to 20.0 parts by weight, or 0.1 to 10.0 parts by weight, per 100 parts by weight of core particles. In this case, the effect of suppressing gas generation in the aqueous slurry by forming a coating layer is excellent, while the reduction in volume and efficiency due to the weight (or thickness) of the coating layer can be minimized.

[0071] Here, the active ingredient comprises a metal phosphate precursor, a metal phosphate precursor and at least one selected from lithium hydroxide, boric acid, and lithium borate, or a nonmetallic phosphate, boric acid, and lithium borate.

[0072] (S3) Step Step (S3) is a step for manufacturing a negative electrode material in which an inorganic coating layer is formed by heat treatment, and may be performed by firing a negative electrode material in which a coating layer-forming composition is coated on the surface of core particles at a temperature of 700°C to 900°C.

[0073] On the other hand, in a method for manufacturing a negative electrode material according to one embodiment of the present invention, a coating layer forming composition is coated onto the surface of core particles, and then fired at a high temperature within the above range, thereby forming an inorganic coating layer while a polycondensation reaction occurs, and hydrogen generation can be effectively suppressed when a negative electrode material slurry is manufactured by this aqueous process.

[0074] Specifically, the firing process may be carried out in an inert gas atmosphere at a temperature range of 700°C to 900°C for 1 to 6 hours. In this case, a more sufficient polycondensation reaction occurs, and an excellent inorganic coating layer can be formed due to the effect of suppressing hydrogen generation.

[0075] negative electrode The present invention provides a negative electrode including the negative electrode material.

[0076] The negative electrode according to one embodiment of the present invention includes a conductive metal current collector and a negative electrode material layer provided on at least one surface of the current collector, wherein the negative electrode material layer includes the above-mentioned negative electrode material, and the negative electrode material may include lithium ions diffused by pre-lithiumization.

[0077] The anode according to the present invention includes an anode material layer containing the pre-lithified silicone or silicone oxide-based anode material, thereby providing excellent initial efficiency and suppressing volume expansion of the anode, resulting in excellent capacity retention and long-term stability.

[0078] The conductive metal current collector contains a highly conductive metal, and there are no particular limitations on the conductive metal current collector as long as it is unreactive within the battery voltage range. For example, stainless steel, aluminum, copper, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. The current collector may also have a thickness of 3 μm to 500 μm.

[0079] On the other hand, the negative electrode can be manufactured by mixing an aqueous solvent, the negative electrode material, a binder, and a conductive material to produce a negative electrode material slurry, and then applying the negative electrode material slurry to at least one surface of a conductive metal current collector and drying it. Here, the aqueous solvent may be water.

[0080] Furthermore, the conductive material may include any material that does not cause a chemical change and has electronic conductivity, but specifically, examples of the conductive material include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these can be used alone or as a mixture of two or more.

[0081] Furthermore, the binder may typically be added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode material layer. Examples of such binders include polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0082] Lithium-ion rechargeable battery The present invention provides a lithium secondary battery including the negative electrode.

[0083] According to one embodiment of the present invention, the lithium secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The lithium secondary battery may also selectively further include a battery container for housing the electrode assembly of the negative electrode, positive electrode, and separator, and a sealing member for sealing the battery container.

[0084] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode material layer located on the positive electrode current collector.

[0085] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. The positive electrode current collector usually has a thickness of 3 μm to 500 μm, and the bonding strength of the positive electrode material may be strengthened by forming fine irregularities on the surface. For example, it can be used in various forms such as film, sheet, foil, mesh, porous body, foam, and nonwoven fabric.

[0086] According to one embodiment of the present invention, the positive electrode material layer may selectively include a binder and a conductive material together with the positive electrode material.

[0087] According to one embodiment of the present invention, the cathode material may be LiCoO2, LiCoPO4, LiNiO2, Li x Ni a Co b M 1 c M 2 d O2(M 1 and M 2 Each is independently selected from the group consisting of Al, Mn, Cu, Fe, V, Cr, Mo, Ga, B, W, Mo, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y, and 0.9 ≤ x ≤ 1.1, 0 <a<1.0、0<b<1.0、0≦c<0.5、0≦d<0.5、a+b+c+d=1である。)、LiMnO2、LiMnO3、LiMn2O3、LiMn2O4、LiMn 2-e M 3 e O2(M 3 ( is one or more elements selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and 0.01 ≤ e ≤ 0.1. ), Li2Mn3M 4O8(M 4 (This is one or more selected from the group consisting of Ci, Ni, Fe, Cu, and Zn.) It may also be one selected from the group consisting of LiFePO4, Li2CuO2, LiV3O8, V2O5, Cu2V2O7, and lithium metal.

[0088] According to one embodiment of the present invention, the binder is a component that assists in bonding between the conductive material, the positive electrode material, and the current collector, and is usually added in an amount of 0.1% to 10% by weight based on the total weight of the positive electrode material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0089] According to one embodiment of the present invention, the conductive material in the positive electrode layer is a component for further improving the conductivity of the positive electrode material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the positive electrode layer. Such conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; carbon fluoride; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0090] According to one embodiment of the present invention, the positive electrode may be manufactured by applying a slurry for forming a positive electrode material layer, which is prepared by dissolving or dispersing a positive electrode material and a binder and a conductive material selectively in a solvent, onto a positive electrode current collector and drying it, or by casting the slurry for forming a positive electrode material layer onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0091] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular limitations as long as it is a separator that is normally used in lithium secondary batteries, and is particularly preferred if it has low resistance to ion movement of the electrolyte and excellent electrolyte impregnation ability. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be used selectively as a single-layer or multi-layer structure.

[0092] According to one embodiment of the present invention, the electrolyte may include, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0093] According to one embodiment of the present invention, the organic solvent can be used without particular limitations as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0094] According to one embodiment of the present invention, the lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions used in lithium secondary batteries. Specifically, the anion of the lithium salt is F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - CF3CF2SO3 - (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - , (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - , and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of the following, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably in the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0095] According to one embodiment of the present invention, the electrolyte may also contain, in addition to the constituent components of the electrolyte, for the purpose of improving the battery life characteristics, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, for example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), propane sultone (PS), 1,3-propane sultone (PRS), ethylene sulfate (ESa), succinonitrile (SN), adiponitrile (AN), hexane tricarbonitrile (HTCN), γ-butyrolactone, biphenyl (BP), cyclohexylbenzene (CHB), and t-amylbenzene (tert-amyl The mixture may further contain one or more additives selected from the group consisting of benzene, TAB, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additives may be present in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0096] The lithium secondary battery containing the negative electrode according to the present invention exhibits excellent capacity characteristics, output characteristics, and life characteristics stably, making it useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the electric vehicle field, including hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0097] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-shaped, or coin-shaped, using a can.

[0098] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also suitably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells.

[0099] Thus, according to one embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0100] According to one embodiment of the present invention, the battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems. [Examples]

[0101] Examples Hereinafter, embodiments of the present invention will be described in detail so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0102] Example 1 Average particle size (D 50 ) is 6 μm, 100 g of SiOx / C (0 < x ≤ 2) having a carbon coating layer on the surface and 6 g of lithium powder were mixed, and heat-treated at 750 °C for 2 hours to produce Li-SiOx / C, which is prelithiated core particles.

[0103] 15 g of Al(H2PO4)3, which is a metal phosphate precursor, and 150 g of zirconia balls with a diameter of 1 mm were pulverized in a planetary ball mill at 500 rpm for 24 hours under a solvent of 34 g of acetone to reduce the precursor particle size to 50 nm to 500 nm.

[0104] 15 g of the core particles Li-SiOx / C and 0.75 g of Al(H2PO4)3 were put into a particle composite device (NOB-MINI, Hosokawa) and driven at 5000 rpm for 15 minutes to produce Li-SiOx / C coated with Al(H2PO4)3 on the surface. Then, under an argon atmosphere, heat treatment was performed in a tube furnace at 80 °C for 1 hour and then at 700 °C for 2 hours in sequence to produce Li-SiOx / C coated with Al(PO3)3.

[0105] Example 2 Average particle size (D 50 ) is 6 μm, 100 g of SiOx / C (0 < x ≤ 2) having a carbon coating layer on the surface and 6 g of lithium powder were mixed, and heat-treated at 750 °C for 2 hours to produce Li-SiOx / C, which is prelithiated core particles.

[0106] 15 g of Al(H2PO4)3, which is a metal phosphate precursor, and 150 g of zirconia balls with a diameter of 1 mm were pulverized in a planetary ball mill at 500 rpm for 24 hours to reduce the precursor particle size to 50 nm to 500 nm.

[0107] 5 g of the core particles Li-SiOx / C and 0.25 g of Al(H2PO4)3 were mixed in a solution of 30 g of ethanol containing 0.05 g of cetrimonium bromide (CTAB), a cationic surfactant, and ultrasonicated for 60 minutes for dispersion. Then, the mixture was stirred at 300 rpm using a magnetic stirrer at 85 °C to evaporate the solvent, producing Li-SiOx / C coated with Al(H2PO4)3 on its surface. Thereafter, under an argon atmosphere, heat treatment was performed in a tube furnace at 80 °C for 1 hour and then at 700 °C for 6 hours in sequence to produce Li-SiOx / C coated with Al(PO3)3.

[0108] Example 3 In Example 2, except that 5 g of core particles Li-SiOx / C (0 < x ≦ 2) and 0.10 g of Al(H2PO4)3 were mixed in a solution of 30 g of ethanol containing 0.05 g of cetrimonium bromide (CTAB), a cationic surfactant, the same procedure as in Example 2 was carried out to produce Li-SiOx / C coated with Al(PO3)3.

[0109] Example 4 In Example 2, except that 0.11 g of LiOH was additionally mixed with 0.25 g of Al(H2PO4)3 in a solution of 30 g of ethanol containing 0.05 g of cetrimonium bromide (CTAB), the same procedure as in Example 2 was carried out to produce Li-SiOx / C coated with Li9Al3(P2O7)3(PO4)2.

[0110] Example 5 In Example 3, except that 0.11 g of LiOH was additionally mixed with 0.10 g of Al(H2PO4)3 in a solution of 30 g of ethanol containing 0.05 g of cetrimonium bromide (CTAB), the same procedure as in Example 3 was carried out to produce Li-SiOx / C coated with Li3PO4.

[0111] Comparative Example 1 Li-SiOx / C (0 < x ≦ 2), the prelithiated core particles produced in Example 1 above, was used as a comparative negative electrode material.

[0112] Comparative Example 2 In Example 2, except that 100 g of SiOx / C (0 < x ≤ 2) having a carbon coating layer on the surface with an average particle size (D 50 ) of 6 μm that was not prelithiated was used as the core particles, the same procedure as in Example 2 was carried out to produce SiOx / C coated with Al(PO3)3.

[0113] Comparative Example 3 In Example 2, except that Al(PO4) was used instead of Al(H2PO4)3 and the heat treatment process at 700°C for 6 hours in sequence was omitted, the same procedure as in Example 2 was carried out to produce Li-SiOx / C coated with Al(PO4).

[0114] Experimental Example 1 The presence or absence of prelithiation of the core of the Li-SiOx / C negative electrode material coated with Al(PO3)3 produced in Example 2 and the presence or absence of the Al(PO3)3 coating layer on the surface were analyzed.

[0115] (1) Analysis of prelithiated Li-SiOx / C core particles XRD (D8 ENDEAVOR, Bruker, λ = 1.5406 Å, 2θ = 10 to 90°) analysis was performed on the prelithiated Li-SiOx / C core particles obtained in Example 2. At this time, as comparative samples, the non-prelithiated SiOx / C core particles of Comparative Example 2 were both analyzed, and the results are shown in FIGS. 1 and 2.

[0116] Peaks of lithium-containing compounds such as Si and lithium silicate were observed in the core particles of Example 2 (see FIG. 1), but peaks corresponding to lithium-containing compounds were not observed in the core particles of Comparative Example 2 (see FIG. 2).

[0117] (2) Analysis of the coating layer To confirm the Al(PO3)3 coating layer on the surface of the Li-SiOx / C anode material coated with Al(PO3)3 manufactured in Example 2, XPS analysis (K-Alpha+, Thermo Fischer Scientific Co., Ltd., X-ray source: monochromatic Al Kalpha (1486.6 eV)) was performed.

[0118] In this study, both Li-SiOx / C and Al(PO3)3 (Sigma Aldrich) from Comparative Example 1 were analyzed as comparative samples, and the results are shown in Table 1 below.

[0119] [Table 1]

[0120] As shown in Table 1 above, the Al / P ratio on the surface of the negative electrode material in Example 2 was confirmed to be at the same level as Al(PO3)3, and from this, it was confirmed that an Al(PO3)3 coating layer was formed.

[0121] Experimental Example 2 Neutral electrode material slurries were prepared using the negative electrode materials of Examples 1 to 5 and Comparative Examples 1 and 3, and the amount of gas generated was measured. The results are shown in Table 2 below.

[0122] A mixed anode material was obtained by mixing each anode material with graphite in a weight ratio of 1:4. A slurry of anode material was then prepared by mixing Super-C65 as the conductive material, carboxymethyl cellulose as the binder, and styrene-butadiene rubber binder in a weight ratio of 96.3:1.0:1.1:1.6 under an aqueous solvent. The slurry was then placed in an aluminum pouch, sealed, and stored in a 60°C oven, and the change in volume of the pouch over time was measured. The amount of gas generated per unit mass of each anode material was calculated by dividing the difference in volume change by the weight of the anode material used.

[0123] [Table 2]

[0124] As shown in Table 2 above, the negative electrode materials of Examples 1 to 5 showed a significantly reduced amount of gas generation compared to Comparative Example 1. Specifically, after 16 hours of storage, Examples 1 to 5 had almost no gas generation, calculated to be 0 ml / g, and even after 136 hours of storage, the gas generation was only about 1 to 3 ml / g, or 33 or 43 ml / g, which was about half the amount of gas generated by Comparative Example 1 after 16 hours of storage. From this, it can be confirmed that the negative electrode material according to the present invention, by including an inorganic coating layer, suppresses the generation of hydrogen in the slurry due to LiOH by-products, even when manufactured in an aqueous negative electrode material slurry.

[0125] Furthermore, the negative electrode material of Comparative Example 3 showed a significant increase in gas generation after 16 and 64 hours of storage compared to the negative electrode materials of Examples 1 to 5. In this case, the negative electrode material of Comparative Example 3 was manufactured by coating the core particles with metal phosphate without heat treatment. From this, it was confirmed that even if an inorganic coating layer is present on the surface of pre-lithified silicone oxide core particles, a coating layer obtained without heat treatment has little to no effect in suppressing gas generation, or is significantly inferior.

[0126] Experimental Example 3 Half-cells were manufactured using the negative electrode materials of Examples 1 to 5 and Comparative Examples 1 to 3, and the battery characteristics were measured. The results are shown in Table 3 below.

[0127] Each negative electrode material was mixed with the conductive material Super-C65 and the binder Li-PAA in a weight ratio of 70:15:15 to produce a negative electrode slurry. This slurry was then applied to copper foil, and the negative electrode was manufactured through drying, rolling, and punching processes.

[0128] A coin half-cell was manufactured by using lithium metal as the counter electrode, interposing a porous polyethylene separator between the negative electrode and the lithium metal, and injecting an electrolyte solution containing 1 M LiPF6, 1.5 wt% VC, and 0.5 wt% PS into a solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70.

[0129] After leaving the aforementioned coin half-cell for 24 hours, 0.005-1.5V vs. Li / Li + The battery was charged to 0.005V with a constant current (CC) of 0.1C in a section, then charged with a constant voltage (CV) until the charging current reached 0.02C, and finally discharged with a constant current (CC) of 0.1C. The charge / discharge capacity and initial efficiency of the first cycle were then measured.

[0130] Furthermore, the charge-discharge capacities up to 30 cycles of Examples 2 and 4 and Comparative Example 1 were compared and are shown in Figures 3 and 4.

[0131] [Table 3]

[0132] From Table 3, Figure 3, and Figure 4, it was confirmed that all of Examples 1 to 5 exhibited excellent initial efficiency and capacity retention rates.

[0133] Generally, silicone oxide anode materials have high initial capacity, but due to volume expansion during charging and discharging and surface side reactions, a large amount of lithium inserted into the anode during initial charging cannot return to the positive electrode, resulting in a large initial irreversible capacity. This problem can also be confirmed from the results of Comparative Example 2.

[0134] Furthermore, pre-lithium-treated silicone oxide anode materials have problems with volume expansion during charging and discharging, and the resulting decrease in capacity, as can be seen from the fact that the capacity retention rate of Comparative Example 1, shown in Figures 3 and 4, is significantly lower compared to the examples.

[0135] From the above results, it was confirmed that the negative electrode material according to the present invention, by including a core containing silicone oxide particles and a lithium-containing compound, and an inorganic coating layer surrounding the core, suppresses hydrogen generation, exhibits excellent initial capacity characteristics, as well as excellent capacity retention rate and storage stability.

Claims

1. A core comprising silicon oxide particles; and one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide; The inorganic coating layer surrounding the core, The inorganic coating layer comprises a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetallic phosphate complex. The metal phosphate is Li ３ PO ４ 、Li ４ P ２ O ７ 、Li ９ Al ３ (P ２ O ７ ) ３ (PO ４ ) ２ 、Co ３ (PO ４ ) ２ 、Co ３ (PO ３ ) ２ 、GaPO ４ 、Ga(PO ３ ) ３ 、FePO ４ 、Fe(PO ３ ) ３ 、Mg ３ (PO ４ ) ２ 、Mg(PO ３ ) ２ 、Ca ３ (PO ４ ) ２ 、Ca(PO ３ ) ２ 、Be ３ (PO ４ ) ２ 、Be(PO ３ ) ２ 、Pb ３ (PO ４ ) ２ 、Pb(PO ３ ) ２ 、LaPO ４ 、La(PO ３ ) ３ 、YPO ４ 、Y(PO ３ ) ３ 、VOPO ４ 、Zr ３ (PO ４ ) ２ 、Zr(PO ３ ) ２ 、and at least one selected from Al(PO ３ ) ３ ; The metal phosphate derivative comprises at least one selected from a unit derived from a metal phosphate, a unit derived from boric acid, and a unit derived from lithium borate. The anode material is a metal phosphate derivative of [M(H n PO 4) m O-B(OH) 2], [(M(H n PO 4) m O) 2-B(OH)], or [(M(H n PO 4) m O) 3-B], where M is at least one selected from Co, Ga, Fe, Mg, Ca, Be, Pb, La, Y, Zr, and Al, n is 1 or 2, and m is 1, 2, or 3.

2. The negative electrode material according to claim 1, wherein the silicone oxide particles include a carbon coating layer on their surface.

3. The lithium oxide-nonmetallic phosphate complex is Li ２ O-BPO ４ The negative electrode material according to claim 1.

4. The negative electrode material according to claim 2, wherein the thickness of the carbon coating layer is 1 nm to 1 μm.

5. The negative electrode material according to claim 1, wherein the thickness of the inorganic coating layer is 0.1 nm to 1 μm.

6. The anode material according to claim 1, wherein the inorganic coating layer further comprises a cationic surfactant.

7. The negative electrode material according to claim 6, wherein the cationic surfactant is cetrimonium bromide.

8. Step (S1) involves mixing silicone oxide particles and lithium powder and heat-treating them to form core particles, Step (S2) involves reacting the core particles with the coating layer forming composition, The process includes a step (S3) of firing at 700°C to 900°C, The method for producing a negative electrode material according to claim 1, wherein the coating layer forming composition comprises a metal phosphate precursor, or comprises a metal phosphate precursor and at least one selected from lithium hydroxide, boric acid, and lithium borate, or comprises a nonmetallic phosphate, boric acid, and lithium borate.

9. The method for producing a negative electrode material according to claim 8, wherein the reaction in step S2 is carried out by mechanical grinding of the core particles and the coating layer forming composition in a solvent-free environment.

10. The reaction in step S2 is carried out by mixing the core particles and the coating layer forming composition in a solvent. The method for producing a negative electrode material according to claim 8, further comprising at least one selected from an organic solvent and a cationic surfactant in the coating layer forming composition.

11. The metal phosphate precursor is Co(H ２ PO ４ ), Ga(H ２ PO ２ ), Fe(H ４ PO ３ ), Mg(H ２ PO ４ ), Ca(H ３ PO ２ ), Be(H ４ PO ２ ), Pb(H ２ PO ４ ), La(HPO ２ ), VO(H ２ PO ４ ), Y ２ (HPO ２ ), Zr(HPO ４ ), and Al(H ２ PO ４ ), and is at least one selected from the group consisting of: the method for producing a negative electrode material according to claim 8.​​​​​​​​​​​​​​​​​​​​​​​​

12. The method for producing a negative electrode material according to claim 8, wherein the lithium hydroxide is LiOH.

13. where the lithium borate is Li ３ BO ３ and Li ２ B ４ O ７ The method for producing a negative electrode material according to claim 8, which is at least one selected from

14. The aforementioned nonmetallic phosphate is NH ４ H ２ PO ４ The method for manufacturing a negative electrode material according to claim 8.

15. Conductive metal current collector, The current collector includes a negative electrode material layer provided on at least one surface of the current collector, The negative electrode material layer includes the negative electrode material described in claim 1.

16. A lithium secondary battery comprising a negative electrode according to claim 15, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

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