Negative electrode material, method for preparing thereof, negative electrode comprising the same and lithium secondary battery comprising the negative electrode

Abstract

The present invention relates to a negative electrode material having an inorganic coating layer, a method for manufacturing the same, a negative electrode comprising the negative electrode material, and a lithium secondary battery comprising the negative electrode, wherein the negative electrode comprises silicon oxide particles; and a core comprising one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide. and comprises an inorganic coating layer surrounding the core, wherein the inorganic coating layer comprises a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate complex, and wherein the metal phosphate is 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 wherein the metal phosphate derivative comprises a metal phosphate-derived unit and a boric acid-derived unit The present invention provides a negative electrode material comprising at least one selected from a lithium borate-derived unit, a method for manufacturing the same, a negative electrode comprising the same, and a lithium secondary battery comprising the negative electrode.

Description

Technology Field

[0001] The present invention relates to a cathode material having an inorganic coating layer, a method for manufacturing the same, a cathode comprising the cathode material, and a lithium secondary battery comprising the cathode. Background Technology

[0003] Recently, as the application areas of lithium-ion batteries have rapidly expanded to include not only power supply for electronic devices such as electrical, electronic, telecommunications, and computers, but also power storage for large-area devices such as automobiles and power storage systems, there is a growing demand for lithium-ion batteries that are high-capacity, high-output, and highly stable.

[0004] A lithium secondary battery is generally manufactured by applying a slurry, which is a mixture of a positive electrode material capable of inserting and extracting lithium ions and a negative electrode material capable of absorbing and releasing lithium ions, and optionally a binder and a conductive material, to a positive electrode current collector and a negative electrode current collector, respectively, and removing the solvent by heat or the like, and then stacking the positive electrodes on both sides of a separator to form an electrode current collector of a predetermined shape, and then inserting the electrode current collector and a non-aqueous electrolyte into a battery case.

[0005] Graphite-based anodes, which are representative anode materials, exhibit excellent structural stability even during lithium insertion and extraction, and show stable capacity retention characteristics over long cycles; however, their low theoretical capacity (350 mAh / g for LiC6) makes them unsuitable as high-capacity, high-output materials currently required. Accordingly, silicon-based anode materials, such as silicon or silicon oxide, are attracting attention as anode materials for next-generation lithium secondary batteries due to their low reduction potential with lithium, abundant reserves, and a theoretical capacity more than 10 times higher than that of graphite (2700–4200 mAh / g for Li4.4Si). However, despite these advantages, silicon-based anodes consume about three times more lithium than graphite-based anodes, and there is a problem where a large amount of the lithium inserted into the anode during initial charging cannot return to the cathode due to volume expansion and surface side reactions during charging and discharging of lithium secondary batteries employing them, resulting in a large initial irreversible capacity.

[0006] In addition, various methods have been attempted to improve the initial efficiency of silicon oxide (SiOx) particles, particularly in order to solve the problem of initial efficiency caused by the irreversible reaction of Li ions, such as doping with Mg or prelithiating Li into the silicon oxide particles. However, when an anode material slurry is prepared using an aqueous process, the lithium compound generated inside the prelithiated silicon oxide particles reacts with H2O to produce LiOH byproducts, which lowers the viscosity of the slurry and generates hydrogen, resulting in poor coating characteristics of the slurry and consequently a decrease in adhesion between the anode material layer and the current collector.

[0007] Therefore, there is a need to develop a cathode material that has excellent initial capacity and capacity retention rate, does not have significant viscosity changes when manufacturing a cathode material slurry through an aqueous process, suppresses hydrogen generation, and suppresses volume expansion during charging and discharging in the cathode using this material. Prior art literature

[0009] KR10-2014-0091388A The problem to be solved

[0010] The present invention was devised to solve the problems of the prior art described above, and aims to provide a cathode material that has excellent initial capacity and capacity retention rate, has almost no change in viscosity when manufacturing a cathode material slurry through an aqueous process, and suppresses hydrogen generation.

[0011] In addition, the present invention aims to provide a method for manufacturing the above-mentioned cathode material.

[0012] In addition, the present invention aims to provide a cathode comprising the above-mentioned cathode material.

[0013] In addition, the present invention aims to provide a lithium secondary battery comprising the above-mentioned negative electrode. means of solving the problem

[0015] To solve the above problem, the present invention provides a cathode material, a method for manufacturing the same, a cathode including the same, and a lithium secondary battery.

[0016] (1) The present invention comprises a core comprising silicon oxide particles; and one or more lithium-containing compounds selected from lithium silicate, lithium disilicate and lithium silicide; and comprises an inorganic coating layer surrounding the core, wherein the inorganic coating layer comprises a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate complex, and wherein the metal phosphate is 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 wherein the metal phosphate derivative comprises a metal phosphate-derived unit and a boric acid-derived unit A cathode material is provided that comprises at least one selected from lithium borate-derived units.

[0017] (2) The present invention provides a cathode material according to (1), wherein the silicon oxide particles include a carbon coating layer on their surface.

[0018] (3) In the present invention, in (1) or (2) above, the metal phosphate derivative is [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 is 1, 2 or 3, providing a cathode material.

[0019] (4) The present invention provides a cathode material in which, in (1) or (2), the lithium oxide-nonmetal phosphate composite is Li2O-BPO4.

[0020] (5) The present invention provides a cathode material in which, in any one of (2) to (4), the thickness of the carbon coating layer is 1 nm to 1 μm.

[0021] (6) The present invention provides a cathode material in which, in any one of (1) to (5), the inorganic coating layer is 0.1 nm to 1 μm.

[0022] (7) The present invention provides a cathode material in which, in any one of (1) to (6), the coating layer further comprises a cationic surfactant.

[0023] (8) The present invention provides a cathode material in which, in (7) above, the cationic surfactant is cetrimonium bromide.

[0024] (9) The present invention provides a method for manufacturing a negative electrode material of any one of (1) to (8), comprising the steps of: mixing silicon oxide particles and lithium powder and heat treating to form core particles (S1); reacting the core particles with a composition for forming a coating layer (S2); and calcining at 700°C to 900°C (S3), wherein the composition for forming a coating layer comprises a metal phosphate precursor, or comprises at least one selected from a metal phosphate precursor and lithium hydroxide, boric acid and lithium borate, or comprises a non-metal phosphate, boric acid and lithium borate.

[0025] (10) The present invention provides a method for manufacturing a cathode material in which, in (9) above, the reaction of step S2 is performed by mechanically grinding the core particles and the composition for forming the coating layer in a solvent-free environment.

[0026] (11) The present invention provides a method for manufacturing a cathode material, wherein the reaction of step S2 in (9) is performed by mixing a core particle and a composition for forming a coating layer in a solvent, and the composition for forming a coating layer further comprises at least one selected from an organic solvent and a cationic surfactant.

[0027] (12) The present invention provides a method for manufacturing a cathode material in any one of (9) to (11), wherein the metal phosphate precursor is 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.

[0028] (13) The present invention provides a method for manufacturing a cathode material in any one of (9) to (11), wherein the lithium hydroxide is LiOH.

[0029] (14) The present invention provides a method for manufacturing a cathode material in which, in any one of (9) to (11), the lithium borate is at least one selected from Li3BO3 and Li2B4O7.

[0030] (15) The present invention provides a method for manufacturing a cathode material in any one of (9) to (11), wherein the non-metallic phosphate is NH4H2PO4.

[0031] (16) The present invention provides a cathode comprising a conductive metal current collector; and a negative electrode layer provided on at least one surface of the current collector, wherein the negative electrode layer comprises any one of (1) to (8) a negative electrode material, and the negative electrode material comprises lithium ions diffused by pre-lithiation.

[0032] (17) The present invention provides a lithium secondary battery comprising a cathode according to (16); a positive electrode; and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Effects of the invention

[0034] The cathode material according to the present invention comprises a core containing silicon oxide particles and a lithium-containing compound and an inorganic coating layer surrounding the core, so that even when prepared as an aqueous cathode material slurry, the decrease in viscosity of the slurry and hydrogen generation caused by LiOH byproducts are suppressed, resulting in excellent initial capacity and capacity retention rate, and compared to an aqueous cathode material slurry containing conventional silicon oxide particles, the change in viscosity is small and hydrogen generation is reduced, thereby suppressing slurry coating defects and adhesion reduction caused by the decrease in viscosity of the slurry, and has the effect of excellent storage stability.

[0035] In addition, the cathode according to the present invention includes a cathode layer comprising a pre-lithiated cathode material, thereby having excellent initial efficiency and suppressing volume expansion of the cathode, so that the capacity retention rate and long-term stability can be excellent. Brief explanation of the drawing

[0037] The following drawings attached to this specification illustrate specific embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the aforementioned description; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. Figure 1 is the XRD pattern of the pre-lithiated Li-SiOx / C core particles prepared in Example 2. Figure 2 is the XRD pattern of the pre-lithiated SiOx / C core particles prepared in Comparative Example 2. Figure 3 is a graph comparing the capacity retention rates of a half-cell using the cathode material prepared in Example 2 and a half-cell using the cathode material of Comparative Example 1. Figure 4 is a graph comparing the capacity retention rates of a half-cell using the cathode material prepared in Example 4 and a half-cell using the cathode material of Comparative Example 1. Specific details for implementing the invention

[0038] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0039] Terms and words used in the description and claims of the present invention should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0041] cathode material

[0042] The present invention provides a silicon or silicon oxide-based cathode material comprising an inorganic coating layer on its surface.

[0043] A negative electrode material according to one embodiment of the present invention comprises silicon oxide particles; and a core comprising one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide; and comprises an inorganic coating layer surrounding the core, wherein the inorganic coating layer comprises a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate complex, and wherein the metal phosphate is 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 wherein the metal phosphate derivative comprises a metal phosphate-derived unit and a boric acid-derived unit It is characterized by including at least one selected from lithium borate-derived units.

[0045] Graphite-based anode materials are known as anode materials, and although graphite-based anode materials exhibit excellent structural stability during lithium insertion and extraction and show stable capacity retention characteristics over long cycles, they are not suitable as high-capacity, high-power materials currently required due to their low theoretical capacity (350 mAh / g for LiC6). Therefore, silicon or silicon oxide, which have a theoretical capacity more than 10 times higher than that of graphite (~4200 mAh / g for Li4.4Si), are attracting attention. However, silicon-based anode materials consume about three times more lithium than graphite-based anode materials and have the problem of increased irreversible capacity. To solve the problem of initial efficiency caused by the irreversible reaction of lithium ions, a method is being attempted to improve initial efficiency by prelithiating Li. However, when preparing an aqueous anode slurry using prelithiated silicon-based anode materials, the lithium compounds generated by prelithiation react with H2O to produce LiOH byproducts, which increase hydrogen generation, change the viscosity of the slurry, and degrade the slurry coating characteristics, causing serious defects in the slurry coating. Consequently, fatal problems such as a rapid decrease in capacity due to electrical short circuits with the current collector may occur.

[0046] However, the cathode material according to the present invention has a structure comprising an inorganic coating layer on the surface of a core containing pre-lithiated silicon oxide particles, so even if it is manufactured as an aqueous cathode material slurry, the coating layer suppresses the reduction in viscosity of the slurry and hydrogen generation caused by LiOH by-products, thereby preventing slurry coating defects and reduced adhesion, so the integrity and capacity retention rate of the cathode can be excellent.

[0048] Hereinafter, the cathode material according to the present invention will be described in detail.

[0049] According to one embodiment of the present invention, the cathode material comprises silicon oxide particles; a core comprising 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 comprise a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate complex.

[0051] The above core contains silicon oxide particles and a lithium-containing compound.

[0052] Here, the core is obtained by mixing silicon oxide particles with lithium powder and then heat-treating, that is, formed by pre-lithiating the silicon oxide particles; the core comprises silicon oxide particles and lithium silicate (Li2SiO3), lithium disilicate (Li2Si2O5), and lithium silicide (Li2Si2O5) formed by the pre-lithiation of the silicon oxide particles. a Si, 0 <a≤4.4) 중에서 선택된 1종 이상의 리튬 함유 화합물을 포함한다.

[0053] The above silicon oxide (SiOx, where x is 0 <x≤2이다) 입자는 비정질 구조를 갖는 것일 수 있으며, 상기 실리콘 산화물 입자는 5 nm 내지 20 ㎛의 평균입경(D 50 It may have ).

[0054] In addition, the silicon oxide particles may include a carbon coating layer on their surface, and the thickness of the carbon coating layer may be 1 nm to 1 μm or 1 nm to 100 nm.

[0056] In addition, the cathode material comprises an inorganic coating layer surrounding the core, and the inorganic coating layer may comprise a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate complex.

[0057] In addition, the thickness of the inorganic coating layer may be 0.1 nm to 1 μm.

[0059] 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.

[0060] In addition, the metal phosphate derivative may be, for example, a condensation product of a metal phosphate precursor and boric acid, and specifically, the metal phosphate derivative is [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 can be 1, 2 or 3.

[0061] As another example, the metal phosphate derivative may be a reaction product of a metal phosphate precursor, boric acid, and lithium borate.

[0062] In addition, the lithium oxide-nonmetal phosphate may be a reaction product of nonmetal phosphate, boric acid, and lithium borate, specifically Li2O-BPO4.

[0063] As another example, the coating layer may further include a cationic surfactant, and the cationic surfactant may be cetrimonium bromide.

[0065] Method for manufacturing cathode material

[0066] The present invention provides a method for manufacturing the above-mentioned cathode material.

[0067] A method for manufacturing a cathode material according to one embodiment of the present invention comprises the steps of: mixing silicon oxide particles and lithium powder and heat-treating to form core particles (S1); reacting the core particles with a composition for forming a coating layer (S2); and calcining at 700°C to 900°C (S3). The composition for forming a coating layer may include a metal phosphate precursor, or at least one selected from a metal phosphate precursor and lithium hydroxide, boric acid, and lithium borate, or may include a non-metal phosphate, boric acid, and lithium borate.

[0069] Hereinafter, a method for manufacturing the cathode material according to one embodiment of the present invention will be explained in more detail by dividing it into steps.

[0070] (S1) Step

[0071] The above step (S1) is a step for manufacturing pre-lithiated core particles, and may be performed by mixing silicon oxide particles and lithium powder and heat treating.

[0072] Here, the silicon oxide particles are as described above.

[0073] In addition, the silicon oxide particles may include a carbon coating layer on their surface, and in this case, the silicon oxide particles may have a carbon coating layer formed by heat-treating a carbon precursor on their surface to carbonize it.

[0074] At this time, the carbonization method described above may utilize methods conventional in the art, such as dry or wet mixing, and carbon-containing gases such as methane, ethane, propane, acetylene, and ethylene may be used as carbon precursors, or a carbon precursor that is liquid at room temperature, such as toluene, may be vaporized and a deposition method such as chemical vapor deposition (CVD) may be used. In addition, resins such as phenol resin, naphthalene resin, polyvinyl alcohol resin, urethane resin, polyimide resin, furan resin, cellulose resin, epoxy resin, and polystyrene resin, coal-based pitch, petroleum-based pitch, tar, or low molecular weight heavy oil may be used as amorphous carbon precursors. Sucrose may also be used.

[0075] In addition, the mixing of the silicon oxide particles and the lithium powder can be carried out using powder mixing methods conventional in the art without specific limitations, as long as the mixture is uniformly mixed. In this case, the lithium powder may be mixed in an amount of 1 to 15 parts by weight, specifically 3 to 10 parts by weight or 5 to 10 parts by weight, based on 100 parts by weight of the silicon oxide particles. In this case, the increase in initial efficiency due to the pre-lithiation of the silicon oxide can be sufficiently secured, while the reduction in capacity, which is in a trade-off relationship with this, can be minimized.

[0076] In addition, the heat treatment may be performed at a temperature of less than 1000°C, specifically 900°C or lower, or at a temperature of 500 to 1000°C, 600 to 1000°C, 500 to 900°C, or 600 to 900°C. If the heat treatment temperature exceeds 1000°C, there may be a problem in that the Si crystals of the silicon oxide particles tend to increase, making it difficult to control volume expansion during lithium insertion and release.

[0078] (S2) Step

[0079] The above step (S2) is a step for applying (coating) a composition for forming a coating layer on the surface of a core particle, and can be performed by reacting the core particle prepared in the above step (S1) with the composition for forming a coating layer, and the reaction can be performed through wet coating or dry coating.

[0080] 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, and in this case, the coating layer may be formed by sufficient contact between solid reactants in the absence of a solvent.

[0081] As another example, the reaction between the core particle and the coating layer forming composition may be carried out by mixing the core particle and the coating layer forming composition in a solvent, and in this case, the coating layer forming composition may further include at least one selected from an organic solvent and a cationic surfactant.

[0082] The above-mentioned composition for forming a coating layer may include a metal phosphate precursor, or include at least one selected from a metal phosphate precursor and lithium hydroxide, boric acid, and lithium borate, or include a non-metal phosphate, boric acid, and lithium borate.

[0083] 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 specifically, at least one selected from the group consisting of Co(H2PO4)2, Mg(H2PO4)2, and Al(H2PO4)3.

[0084] In addition, the lithium hydroxide may be LiOH.

[0085] In addition, the lithium borate may be at least one selected from Li3BO3 and Li2B4O7.

[0086] In addition, the non-metallic phosphate may be NH4H2PO4.

[0088] Meanwhile, in reacting the core particles with the coating layer-forming composition to apply (coat) 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 effective component 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 the core particles. In this case, the effect of suppressing gas generation in the aqueous slurry by forming the coating layer is excellent, while the reduction in capacity and efficiency due to the weight (or thickness) of the coating layer can be minimized.

[0089] Here, the active ingredient comprises at least one selected from a metal phosphate precursor, a metal phosphate precursor and lithium hydroxide, boric acid and lithium borate, or a non-metal phosphate, boric acid and lithium borate.

[0091] (S3) Step

[0092] The above step (S3) is a step for manufacturing a cathode material in which an inorganic coating layer is formed through heat treatment, and can be performed by firing the cathode material, which has a coating layer forming composition coated on the surface of the core particles, at a temperature of 700°C to 900°C.

[0093] Meanwhile, in a method for manufacturing a cathode material according to one embodiment of the present invention, a composition for forming a coating layer is coated on the surface of a core particle and then fired at a high temperature within the above range, thereby forming an inorganic coating layer while causing a polycondensation reaction to occur, which can effectively suppress hydrogen generation when manufacturing a cathode material slurry through this aqueous process.

[0094] Specifically, the above calcination may be carried out under an inert gas atmosphere at a temperature range of 700°C to 900°C for 1 to 6 hours, and in this case, a more sufficient polycondensation reaction may occur, and an inorganic coating layer with a better hydrogen generation suppression effect may be formed.

[0096] cathode

[0097] The present invention provides a cathode comprising the above cathode material.

[0098] According to one embodiment of the present invention, the cathode comprises a conductive metal current collector; and a cathode material layer provided on at least one surface of the current collector, wherein the cathode material layer comprises the cathode material, and the cathode material may comprise lithium ions diffused by pre-lithiation.

[0100] The cathode according to the present invention comprises a cathode layer containing the above-mentioned pre-lithiated silicon or silicon oxide-based cathode material, thereby having excellent initial efficiency and suppressing volume expansion of the cathode, so that the capacity retention rate and long-term stability can be excellent.

[0102] The conductive metal current collector comprises a highly conductive metal, wherein the conductive metal current collector is not particularly limited as long as it is non-reactive within the voltage range of the battery, for example, stainless steel, aluminum, copper, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the current collector may have a thickness of 3 μm to 500 μm.

[0104] Meanwhile, the above-mentioned cathode may be prepared by mixing an aqueous solvent, the cathode material, a binder, and a conductive material to produce a cathode material slurry, and then applying and drying the cathode material slurry on at least one surface of a conductive metal current collector. Here, the aqueous solvent may be water.

[0106] In addition, the conductive material may be included without special limitations as long as it does not cause chemical changes and has electronic conductivity, but specifically, the conductive material may 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, carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used.

[0107] In addition, the binder may typically be added in an amount of 0.1% to 10% by weight based on the total weight of the cathode layer, and 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.

[0109] lithium secondary battery

[0110] The present invention provides a lithium secondary battery comprising the above-mentioned negative electrode.

[0111] According to one embodiment of the present invention, the lithium secondary battery may comprise the negative electrode; the positive electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. Additionally, the lithium secondary battery may optionally further comprise a battery container housing an electrode assembly of the negative electrode, the positive electrode, and the separator, and a sealing member sealing the battery container.

[0112] According to one embodiment of the present invention, the anode may comprise an anode current collector and an anode material layer located on the anode current collector.

[0113] According to one embodiment of the present invention, the positive current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the positive current collector may typically have a thickness of 3 μm to 500 μm, and may form fine irregularities on its surface to strengthen the bonding strength of the positive material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0114] According to one embodiment of the present invention, the anode layer may optionally include a binder and a conductive material together with the anode material.

[0115] According to one embodiment of the present invention, the cathode material is 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=1이다.), LiMnO2, LiMnO3, LiMn2O3, LiMn2O4, LiMn 2-e M 3 eO2(M 3 ...is one or more selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and 0.01≤e≤0.1), Li2Mn3M 4 O8(M 4 is one or more selected from the group consisting of Ci, Ni, Fe, Cu and Zn), and may be one selected from the group consisting of LiFePO4, Li2CuO2, LiV3O8, V2O5, Cu2V2O7 and lithium metal.

[0116] According to one embodiment of the present invention, the binder is a component that assists in bonding between the conductive material, the cathode material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the cathode material layer. Examples of such a binder 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.

[0117] According to one embodiment of the present invention, the conductive material of the cathode material layer 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 cathode material layer, as a component for further improving the conductivity of the cathode material. Such conductive material is not particularly limited as long as it has conductivity without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0118] According to one embodiment of the present invention, the anode may be manufactured by applying and drying a slurry for forming an anode layer, prepared by dissolving or dispersing an anode material and optionally a binder and a conductive material in a solvent, onto an anode current collector, or by casting the slurry for forming an anode layer onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0119] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0120] According to one embodiment of the present invention, the electrolyte may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which are usable in the manufacture of a lithium secondary battery, but is not limited thereto. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0121] According to one embodiment of the present invention, the organic solvent may be used without special limitations as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; or an aromatic hydrocarbon-based solvent such as benzene or fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0122] According to one embodiment of the present invention, the lithium salt may be used without special limitations as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, as the anion of the lithium salt, 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 LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0123] According to one embodiment of the present invention, in addition to the electrolyte components, for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, the electrolyte may include, for example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), propane sulfone (PS), 1,3-propane sulfone (PRS), ethylene sulfate (ESa), succinonitrile (SN), adiponitrile (AN), hexane tricarbonitrile (HTCN), γ-butyrolactone, biphenyl (BP), cyclohexyl benzene (CHB), t-amyl One or more additives selected from the group consisting of benzene (tert-amyl benzene, TAB), or haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride may be further included. In this case, the said additives may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

[0125] Since the lithium secondary battery including the negative electrode according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEV) and electric vehicles (EV).

[0126] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0127] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0128] Accordingly, 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.

[0129] According to one embodiment of the present invention, the battery module or battery pack may be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0131] Examples

[0132] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0134] Example 1

[0135] Average particle size (D 50 SiOx / C(0) having a carbon coating layer on a surface with a thickness of 6 μm <x≤2) 100 g과 리튬 분말 6 g을 혼합하고, 750℃에서 2시간 동안 열처리하여 전리튬화된 코어입자인 Li-SiOx / C를 제조하였다.

[0136] 315 g of Al(H2PO4) metal phosphate precursor and 150 g of zirconia balls with a diameter of 1 mm were ground in a planetary ball mill at 500 rpm for 24 hours in 34 g of acetone solvent to reduce the precursor particle size to 50 nm to 500 nm.

[0137] 15 g of the above core particles Li-SiOx / C and 30.75 g of Al(H2PO4) were introduced into a particle composite equipment (NOB-MINI, Hosokawa) and operated at 5000 rpm for 15 minutes to produce Li-SiOx / C coated with Al(H2PO4)3 on the surface. Subsequently, Li-SiOx / C coated with Al(PO3)3 was produced by sequentially heat-treating in a tube furnace under an argon atmosphere at 80°C for 1 hour and at 700°C for 2 hours.

[0139] Example 2

[0140] Average particle size (D 50 SiOx / C(0) having a carbon coating layer on a surface with a thickness of 6 μm <x≤2) 100 g과 리튬 분말 6 g을 혼합하고, 750℃에서 2시간 동안 열처리하여 전리튬화된 코어입자인 Li-SiOx / C를 제조하였다.

[0141] 315 g of Al(H2PO4) metal phosphate precursor and 150 g of zirconia balls with a diameter of 1 mm were ground in a planetary ball mill at 500 rpm for 24 hours in 34 g of acetone solvent to reduce the precursor particle size to 50 nm to 500 nm.

[0142] 5 g of the above core particles Li-SiOx / C and 30.25 g of Al(H2PO4) were mixed in a 30 g solution of ethanol containing 0.05 g of cetrimonium bromide (CTAB), a cationic surfactant, and dispersed by sonication for 60 minutes. Subsequently, Li-SiOx / C coated with Al(H2PO4)3 on its surface was prepared by evaporating the solvent while stirring at 300 rpm in a magnetic stirring device at 85°C. Subsequently, Li-SiOx / C coated with Al(PO3)3 was prepared by sequentially heat-treating in a tube furnace under an argon atmosphere at 80°C for 1 hour and at 700°C for 6 hours.

[0144] Example 3

[0145] In Example 2, the core particles Li-SiOx / C(0 <x≤2) 5 g과 Al(H2PO4)30.10 g을 양이온성 계면활성제인 브로민화 세트리모늄(CTAB) 0.05 g을 포함한 에탄올 30 g 용액에 혼합한 것을 제외하고는 상기 실시예 2와 동일하게 실시하여 Al(PO3)3가 코팅된 Li-SiOx / C를 제조하였다.

[0147] Example 4

[0148] In Example 2, Li-SiOx / C coated with Li9Al3(P2O7)3(PO4)2 was prepared by carrying out the same procedure as in Example 2, except that 0.11 g of LiOH was additionally mixed with 30.25 g of Al(H2PO4) in a 30 g solution of ethanol containing 0.05 g of cetrimonium bromide (CTAB).

[0150] Example 5

[0151] In Example 3, Li-SiOx / C coated with Li3PO4 was prepared by carrying out the same procedure as in Example 3, except that 0.11 g of LiOH was additionally mixed with 30.10 g of Al(H2PO4) in a 30 g solution of ethanol containing 0.05 g of cetrimonium bromide (CTAB).

[0153] Comparative Example 1

[0154] The pre-lithiated core particle Li-SiOx / C(0) prepared in Example 1 above <x≤2)를 비교 음극재로 사용하였다.

[0156] Comparative Example 2

[0157] In Example 2 above, the average particle size (D) that is not pre-lithiated as a core particle 50 SiOx / C(0) having a carbon coating layer on a surface with a thickness of 6 μm <x≤2) 100 g를 사용한 것을 제외하고는 실시예 2와 동일하게 실시하여 Al(PO3)3가 코팅된 SiOx / C를 제조하였다.

[0159] Comparative Example 3

[0160] Li-SiOx / C coated with Al(PO4) was prepared by carrying out the same procedure as in Example 2 above, except that Al(PO4) was used instead of Al(H2PO4)3 in Example 2 above and the process of sequential heat treatment at 700°C for 6 hours was omitted.

[0162] Experimental Example 1

[0163] The presence or absence of pre-lithiation of the Al(PO3)3 coated Li-SiOx / C cathode core prepared in Example 2 and the presence or absence of an Al(PO3)3 coating layer on the surface were analyzed.

[0164] (1) Analysis of pre-lithiated Li-SiOx / C core particles

[0165] The pre-lithiated Li-SiOx / C core particles obtained in Example 2 were subjected to XRD (D8 ENDEAVOR, Bruker, λ1.5406 Å, 2θ=10~90°) analysis. At this time, the non-lithiated SiOx / C core particles of Comparative Example 2 were also analyzed as comparative data, and the results are shown in Figures 1 and 2.

[0166] In the core particles of Example 2, peaks of lithium-containing compounds such as Si and lithium silicate were observed (see Fig. 1). However, in the core particles of Comparative Example 2, no peaks corresponding to lithium-containing compounds were observed (see Fig. 2).

[0168] (2) Coating layer analysis

[0169] XPS analysis (K-Alpha+, Thermo Fischer Scientific Inc., X-ray source: monochromatic Al Kalpha (1486.6 eV)) was performed to confirm the Al(PO3)3 coating layer on the surface of the Al(PO3)3-coated Li-SiOx / C cathode material prepared in Example 2.

[0170] At this time, Li-SiOx / C of Comparative Example 1 and Al(PO3)3 (Sigma Aldrich) were analyzed together as comparative data, and the results are shown in Table 1 below.

[0171]

[0172] As shown in Table 1 above, it was confirmed that the ratio of Al / P on the surface of the cathode material of Example 2 was at the same level as Al(PO3)3, and through this, it was confirmed that an Al(PO3)3 coating layer was formed.

[0174] Experimental Example 2

[0175] A cathode material slurry was prepared using the cathode materials of Examples 1 to 5 and Comparative Examples 1 and 3, and the amount of gas generated was measured, and the results are shown in Table 2 below.

[0176] Each cathode material was mixed with graphite in a weight ratio of 1:4 to obtain a mixed cathode material, and a cathode material slurry was prepared by mixing Super-C65 as a conductive material and carboxymethyl cellulose and styrene-butadiene rubber binder as binders in a weight ratio of 96.3:1.0:1.1:1.6 in a water solvent. Subsequently, the cathode material slurry was placed in an aluminum pouch, sealed, and stored in a 60°C oven to measure the change in volume of the pouch over time, and the amount of gas generated per mass of each cathode material was calculated by dividing the difference in volume change by the weight of the cathode material used.

[0177]

[0178] As shown in Table 2 above, the amount of gas generated in the cathode materials of Examples 1 to 5 was significantly reduced compared to Comparative Example 1. Specifically, after 16 hours of storage, Examples 1 to 5 showed almost no gas generation, with a calculated value of 0 ml / g. Even after 136 hours of storage, the amount of gas generated was almost at the level of 1 to 3 ml / g, or was 33 or 43 ml / g, which was half the level of gas generated in Comparative Example 1 after 16 hours of storage. Through this, it can be confirmed that the cathode material according to the present invention, by including an inorganic coating layer, can suppress the generation of hydrogen in the slurry caused by LiOH byproducts even when prepared as an aqueous cathode material slurry.

[0179] In addition, the amount of gas generated in the cathode material of Comparative Example 3 increased significantly after storage for 16 and 64 hours compared to the cathode materials of Examples 1 to 5, and the cathode material of Comparative Example 3 was manufactured by coating metal phosphate onto core particles without heat treatment. Through this, it was confirmed that even if an inorganic coating layer is present on the surface of pre-lithiated silicon-based oxide core particles, the gas generation suppression effect is almost non-existent or significantly poor in the case of a coating layer obtained without heat treatment.

[0181] Experimental Example 3

[0182] Half cells were prepared using the cathode materials of Examples 1 to 5 and Comparative Examples 1 to 3, respectively, and battery characteristics were measured, and the results are shown in Table 3 below.

[0183] Each cathode material was mixed with Super-C65, a conductive material, and Li-PAA, a binder, in a weight ratio of 70:15:15 to prepare a cathode slurry, which was then coated onto a copper foil and subjected to drying, rolling, and punching processes to manufacture a cathode.

[0184] A lithium metal was used as the counter electrode, a porous polyethylene separator was placed between the negative electrode and the lithium metal, and a coin half-cell was manufactured by injecting an electrolyte in which 1 M LiPF6, 1.5 wt% VC, and 0.5 wt% PS were dissolved in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:70.

[0185] After leaving the above coin half-cell idle for 24 hours, 0.005-1.5 V vs. Li / Li + In the section, the charge was charged to 0.005 V with a constant current (CC) of 0.1 C, then charged with a constant voltage (CV) until the charging current reached 0.02 C, and discharged with a constant current (CC) of 0.1 C to measure the charge / discharge capacity and initial efficiency of the first cycle.

[0186] In addition, the charge / discharge capacity up to 30 cycles of Examples 2 and 4 and Comparative Example 1 was compared and is shown in FIGS. 3 and 4.

[0187]

[0188] Through Table 3, Figure 3, and Figure 4 above, it was confirmed that the initial efficiency of Examples 1 to 5 is excellent and the capacity retention rate is also excellent.

[0189] Generally, silicon-based oxide cathode materials have a high initial capacity, but due to volume expansion and surface side reactions during charging and discharging, a large amount of lithium inserted into the cathode during initial charging cannot return to the anode, resulting in a problem of a large initial irreversible capacity, which can also be confirmed from the results of Comparative Example 2.

[0190] In addition, pre-lithiated silicon-based oxide cathode materials have volume expansion and capacity degradation issues during charging and discharging, which can be confirmed by the fact that the capacity retention rate of Comparative Example 1 shown in FIGS. 3 and 4 is significantly lower than that of the example.

[0192] From the above results, it was confirmed that the cathode material according to the present invention comprises a core containing silicon oxide particles and a lithium-containing compound and an inorganic coating layer surrounding the core, thereby suppressing hydrogen generation and exhibiting excellent initial capacity characteristics, as well as excellent capacity retention rate and storage stability.

Claims

Claim 1 A core comprising silicon oxide particles; and one or more lithium-containing compounds selected from lithium silicate, lithium disilicate, and lithium silicide; and includes an inorganic coating layer surrounding the core, wherein the inorganic coating layer comprises a metal phosphate, a metal phosphate derivative, or a lithium oxide-nonmetal phosphate complex, and wherein the metal phosphate is 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 wherein the metal phosphate derivative comprises a metal phosphate-derived unit and a boric acid-derived unit and comprises at least one selected from lithium borate-derived units, and the metal phosphate derivative is [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 is 1, 2 or 3. Claim 2 A cathode material according to claim 1, wherein the silicon oxide particles comprise a carbon coating layer on their surface. Claim 3 delete Claim 4 In claim 1, the cathode material wherein the lithium oxide-nonmetal phosphate composite is Li2O-BPO4. Claim 5 A cathode material according to paragraph 2, wherein the thickness of the carbon coating layer is 1 nm to 1 μm. Claim 6 A cathode material according to claim 1, wherein the thickness of the inorganic coating layer is 0.1 nm to 1 μm. Claim 7 A cathode material according to claim 1, wherein the coating layer further comprises a cationic surfactant. Claim 8 In claim 7, the cathode material wherein the cationic surfactant is cetrimonium bromide. Claim 9 A method for manufacturing a negative electrode material according to claim 1, comprising the steps of: mixing silicon oxide particles and lithium powder and heat-treating to form core particles (S1); reacting the core particles with a composition for forming a coating layer (S2); and calcining at 700°C to 900°C (S3), wherein the composition for forming a coating layer comprises a metal phosphate precursor, or comprises at least one selected from a metal phosphate precursor and lithium hydroxide, boric acid, and lithium borate, or comprises a non-metal phosphate, boric acid, and lithium borate, and wherein the lithium borate is at least one selected from Li3BO3 and Li2B4O7. Claim 10 A method for manufacturing a cathode material according to claim 9, wherein the reaction of step S2 is performed by mechanically grinding the core particles and the composition for forming the coating layer in a solvent-free environment. Claim 11 A method for manufacturing a cathode material according to claim 9, wherein the reaction of step S2 is performed by mixing a core particle and a composition for forming a coating layer in a solvent, and the composition for forming a coating layer further comprises at least one selected from an organic solvent and a cationic surfactant. Claim 12 A method for manufacturing a cathode material according to claim 9, 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. Claim 13 A method for manufacturing a cathode material according to claim 9, wherein the lithium hydroxide is LiOH. Claim 14 delete Claim 15 A method for manufacturing a cathode material according to claim 9, wherein the non-metallic phosphate is NH4H2PO4. Claim 16 A cathode comprising a conductive metal current collector; and a cathode material layer provided on at least one surface of the current collector, wherein the cathode material layer comprises the cathode material of claim 1. Claim 17 A lithium secondary battery comprising a negative electrode according to claim 16; a positive electrode; and a separator and an electrolyte interposed between the positive electrode and the negative electrode.

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