Cathode material powder, and cathode and lithium secondary battery comprising same

Abstract

The present invention relates to a cathode material powder comprising a cathode active material, the cathode active material comprising: a core; and a shell disposed on the surface of the core, wherein the core includes a first phosphate represented by chemical formula 1 according to the present invention, and the shell includes a second phosphate represented by chemical formula 2 according to the present invention.

Description

Cathode material powder, cathode and lithium secondary battery containing same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0102780, dated August 1, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a cathode material powder, a cathode containing the same, and a lithium secondary battery.

[0006]

[0007] Lithium secondary batteries are generally manufactured by forming an electrode assembly by interposing a separator between a positive electrode including a positive electrode active material containing lithium and a negative electrode including a negative electrode active material capable of storing lithium ions, inserting the electrode assembly into a battery case, injecting a non-aqueous electrolyte that serves as a medium for transferring lithium ions, and then sealing the electrode assembly.

[0008] These lithium secondary batteries are used not only in portable electronic devices such as mobile phones and laptops, but also in electric vehicles. Demand for these batteries has been rapidly increasing recently with the expansion of electric vehicles. In particular, lithium secondary batteries used in electric vehicles require high energy density and excellent charge-rate characteristics.

[0009] Meanwhile, lithium cobalt-based oxide, lithium nickel-based oxide, lithium manganese-based oxide, lithium nickel cobalt manganese-based oxide, lithium manganese phosphate compounds, and lithium iron phosphate compounds are used as positive electrode active materials for lithium secondary batteries.

[0010] Among these, lithium iron phosphate compounds have excellent thermal stability, excellent life characteristics and safety, and are inexpensive, so they are widely used as positive electrode active materials for lithium secondary batteries. However, they have the problem of low operating voltage, are relatively heavy compared to other compounds, and have low energy density, and it is difficult to implement excellent charge rate characteristics.

[0011] Therefore, there is a need to develop a cathode material powder that can realize the advantages of lithium iron phosphate compounds, such as excellent thermal stability, life characteristics, and safety, while also realizing excellent energy density and charge rate characteristics.

[0012]

[0013] One object of the present invention is to solve the above-described problems, and to provide a cathode powder having excellent energy density and excellent charge rate characteristics by including heterogeneous lithium manganese iron phosphate compounds in the core and the shell, and controlling the molar content of manganese (Mn) and iron (Fe) in each compound within a specific range.

[0014]

[0015] In addition, another object of the present invention is to solve the above-described problems by providing a cathode and a lithium secondary battery including the cathode material powder.

[0016]

[0017] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0018]

[0019] [1] The present invention provides a cathode material powder comprising a cathode active material, wherein the cathode active material comprises a core; and a shell disposed on a surface of the core; wherein the core comprises a first phosphorus oxide represented by the following chemical formula 1, and the shell comprises a second phosphorus oxide represented by the following chemical formula 2.

[0020] [Chemical Formula 1]

[0021] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0022] In the above chemical formula 1, M 1 Contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x1≤0.1, 0.5 <a1<1.0, 0.0≤b1≤0.1이며,

[0023] [Chemical Formula 2]

[0024] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0025] In the above chemical formula 2, M 2 It includes at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x2≤0.1, 0.0≤a2<0.5, 0.0≤b2≤0.1.

[0026] [2] In the present invention, in the above [1], the first phosphoric acid can be represented by the following chemical formula 1-1.

[0027] [Chemical Formula 1-1]

[0028] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0029] In the above chemical formula 1, M 1 It contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x1≤0.1, 0.6≤a1≤0.8, 0.0≤b1≤0.1.

[0030] [3] In the present invention, in the above [1] or [2], the second phosphoric acid can be represented by the following chemical formula 2-1.

[0031] [Chemical Formula 2-1]

[0032] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0033] In the above chemical formula 2, M 2 It contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x2≤0.1, 0.2≤a2≤0.4, 0.0≤b2≤0.1.

[0034] [4] In at least one of the above [1] to [3], the molar ratio of Fe to Mn (Fe / Mn) in the positive electrode active material may be 0.4 to 2.4.

[0035] [5] In at least one of the above [1] to [4], the volume ratio of the core and the shell may be 20:80 to 80:20.

[0036] [6] The present invention, in at least one of the above [1] to [5], the cathode material powder has an average particle diameter D 50 This can be 0.5㎛ to 2.0㎛.

[0037] [7] The present invention is characterized in that in at least one of the above [1] to [6], the cathode material powder has a BET specific surface area of ​​5 m2 / g to 30m 2 / g may be.

[0038] [8] In at least one of the above [1] to [7], the cathode material powder may have a press density of 2.40 g / cc or more measured after pressing at a pressure of 3 tons.

[0039] [9] In at least one of the above [1] to [8], the cathode material powder may further include a coating layer including carbon disposed on the shell.

[0040]

[0010] In the present invention, in the above [9], the content of carbon included in the coating layer may be 0.1 wt% to 5.0 wt% based on the total weight of the positive electrode active material.

[0041]

[0011] The present invention provides a positive electrode comprising a positive electrode powder according to at least one of the above [1] to

[0010] .

[0042]

[0012] The present invention provides a lithium secondary battery comprising: a positive electrode according to the above

[0011] ; a negative electrode disposed opposite the positive electrode; and an electrolyte.

[0043]

[0044] The positive electrode active material included in the positive electrode powder according to the present invention includes a phosphorus oxide represented by Chemical Formula 1 in the core and a phosphorus oxide represented by Chemical Formula 2 in the shell. The phosphorus oxide represented by Chemical Formula 1 has excellent electronic conductivity and lithium ion conductivity, and the phosphorus oxide represented by Chemical Formula 2 has a high operating voltage. Therefore, when the positive electrode powder according to the present invention is applied, the energy density and charge rate characteristics of a lithium secondary battery can be improved.

[0045]

[0046] Hereinafter, the present invention will be described in more detail.

[0047] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0048] The terms used in this invention are used solely to describe exemplary embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0049] In the present invention, it should be understood that terms such as “include,” “have,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0050] In the present invention, the “BET specific surface area” is measured by the BET method, and specifically, can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using BELSORP-mino II of BEL Japan.

[0051] In the present invention, "average particle diameter D 50 " means the particle size based on 50% of the volume cumulative particle size distribution of the particles. The average particle diameter D 50 can be measured using a laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0052]

[0053] The inventors of the present invention have conducted repeated research to improve the energy density and charge rate characteristics of lithium secondary batteries and have found that when a cathode powder is applied in which a lithium manganese iron phosphate compound having a high iron (Fe) content is included in the core and a lithium manganese iron phosphate compound having a high manganese (Mn) content is included in the shell, the energy density and charge rate characteristics of a lithium secondary battery can be improved, thereby completing the present invention.

[0054]

[0055] Hereinafter, the present invention will be described in detail.

[0056] The cathode material powder according to the present invention, the cathode comprising the same, and the lithium secondary battery comprise at least one of the following disclosed configurations, and may comprise any combination between technically possible configurations among the following configurations.

[0057]

[0058] cathode powder

[0059] Hereinafter, the cathode material powder according to the present invention will be described.

[0060] The cathode material powder according to the present invention is a cathode material powder containing a cathode active material,

[0061] The above positive active material comprises a core; and a shell disposed on the surface of the core; wherein the core comprises a first phosphorus oxide represented by the following chemical formula 1, and the shell comprises a second phosphorus oxide represented by the following chemical formula 2.

[0062] [Chemical Formula 1]

[0063] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0064] In the above chemical formula 1, M 1Contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x1≤0.1, 0.5 <a1<1.0, 0.0≤b1≤0.1이며,

[0065] [Chemical Formula 2]

[0066] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0067] In the above chemical formula 2, M 2 It includes at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x2≤0.1, 0.0≤a2<0.5, 0.0≤b2≤0.1.

[0068]

[0069] Lithium manganese phosphate compounds and lithium iron phosphate compounds with an olivine structure have a one-dimensional lithium ion diffusion path within the crystal structure, which presents a problem of low lithium ion conductivity during charge and discharge. Therefore, the average particle size of the compound must be controlled to the order of tens to hundreds of nanometers to perform charge and discharge at high output. However, if the average particle size of the compound is excessively small, there is a limit to increasing the solid content in the slurry, and there is a problem of low energy density due to the difficulty in implementing a high-density electrode due to the disadvantage of rolling.

[0070] In particular, lithium iron phosphate compounds exhibit higher electronic and lithium ion conductivity than lithium manganese phosphate compounds, resulting in superior charging output. Therefore, even if the average particle size is relatively large, the impact on battery performance is minimal, enabling the implementation of high-density electrodes. However, this is hampered by a low operating voltage and thus low energy density.

[0071] On the other hand, lithium manganese phosphate compounds have a high operating voltage and therefore a high energy density, but their charging output characteristics are poor, which limits the ability to increase the particle size of the compound, making it difficult to implement high-density electrodes.

[0072] To solve this problem, lithium manganese iron phosphate compounds (e.g., LiMn) with controlled molar ratio of iron and manganese in lithium phosphate were used. x Fe (1-x) A method of using PO4) as a cathode active material has been proposed, but there is a problem in that it is difficult to escape the trade-off relationship between the advantages and disadvantages of the lithium iron phosphate compound and the lithium manganese phosphate compound described above.

[0073] Therefore, in order to solve the above-mentioned problem, the present invention seeks to apply a cathode material powder including a cathode active material including a lithium manganese iron phosphate compound having a high iron content in a core and a lithium manganese iron phosphate compound having a high manganese content in a shell to a lithium secondary battery.

[0074] At this time, the lithium manganese iron phosphate compound included in the core has a high iron content and thus has excellent charging output, and the lithium manganese iron phosphate compound included in the shell has a high manganese content and thus has a low charging output, but has a high energy density, and because it is included in the shell, the average particle size of the positive electrode active material can be increased. That is, when the above conditions are satisfied, a positive electrode active material having excellent energy density and excellent charging rate characteristics can be manufactured beyond the aforementioned trade-off relationship.

[0075] In contrast, when a lithium manganese iron phosphate compound having a high manganese content is included in the core, the difference between the outermost radius and the innermost radius from the center becomes larger than when the lithium manganese iron phosphate compound having a high manganese content is included in the shell. For example, assuming that the core and shell in a spherical particle with a radius of 0.5 μm have a volume ratio of 50:50, the difference (radius) between the outermost radius and the innermost radius from the center of the core is approximately 0.4 μm, and the difference (thickness) between the outermost radius and the innermost radius from the center of the shell is approximately 0.1 μm. That is, when a lithium manganese iron phosphate compound having a high manganese content is included in the core, the radius or thickness of the lithium manganese iron phosphate compound having a one-dimensional lithium ion diffusion path becomes thicker, which lengthens the diffusion path and causes a problem in which resistance due to manganese oxidation during the charging process increases further. In addition, since the average particle size cannot be sufficiently increased, problems such as low energy density and poor charging rate characteristics arise.

[0076] In addition, when manufacturing a core containing a lithium iron phosphate compound (e.g., LiFePO4) rather than a lithium manganese iron phosphate compound, there is a problem in that the lattice mismatch between the core and the shell is aggravated. Therefore, a high activation energy is required for lithium ions to pass through the boundary between the core and the shell during charge and discharge, resulting in a problem of poor charge rate characteristics.

[0077]

[0078] Hereinafter, the cathode material powder according to the present invention will be described in more detail.

[0079]

[0080] (1) Core

[0081] In the cathode material powder according to the present invention, the cathode active material includes a core, and the core includes a first phosphorus oxide represented by the following chemical formula 1.

[0082] [Chemical Formula 1]

[0083] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0084] In the above chemical formula 1, M 1 It includes at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, preferably, it may include at least one selected from the group consisting of Mg, Ti, V and Nb, and more preferably, it may include at least one selected from the group consisting of Ti and V. When the above conditions are satisfied, effects such as suppression of structural change during repeated charge and discharge of the positive electrode active material can be obtained.

[0085] The above x1 is -0.1 to 0.1. When the above range is satisfied, high capacity characteristics and high energy density per unit volume can be realized.

[0086] The above a1 is the molar fraction of iron (Fe) among all metals excluding lithium in the first phosphate, and is greater than 0.5 and less than 1.0. Preferably, it may be greater than 0.5, 0.55 or more, or 0.6 or more, and less than 1.0, 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less.

[0087] When the above a1 is 0.5 or less, manganese oxidation is aggravated, which causes a problem of increased resistance during the charging process, resulting in a deterioration in the charge rate characteristics. In addition, when the above a1 is 1.0, the lattice mismatch between the core and the shell is aggravated, which increases the activation energy during lithium diffusion, resulting in a high resistance, which causes a problem of poor charge rate characteristics. Therefore, when the above range is satisfied, the electronic conductivity and lithium ion conductivity are high, resulting in excellent charge output, and the particle size can be relatively controlled to achieve excellent energy density.

[0088] The above b1 is M among all metals except lithium in the first phosphate. 1 The molar fraction may be 0.0 or more and 0.1 or less. Preferably, it may be 0.001 or more, 0.002 or more, 0.003 or more, 0.004 or more, 0.005 or more, 0.006 or more, 0.007 or more, 0.008 or more, or 0.009 or more, and may be 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less. When the above range is satisfied, ionic conductivity and electrical conductivity may be improved.

[0089] Preferably, the core may include a first phosphate represented by the following chemical formula 1-1.

[0090] [Chemical Formula 1-1]

[0091] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0092] In the above chemical formula 1, M 1 It contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x1≤0.1, 0.6≤a1≤0.8, 0.0≤b1≤0.1.

[0093]

[0094] (2) Shell

[0095] In the cathode material powder according to the present invention, the cathode active material includes a shell disposed on the surface of the core, and the shell includes a second phosphorus oxide represented by the following chemical formula 2.

[0096] [Chemical Formula 2]

[0097] Li 1+x2 [Mn 1-a2-b2 Fe a2 M2 b2 ]PO4

[0098] In the above chemical formula 2, M 2 It includes at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, preferably, it may include at least one selected from the group consisting of Mg, Ti, V and Nb, and more preferably, it may include at least one selected from the group consisting of Ti and V. When the above conditions are satisfied, effects such as suppression of structural change during repeated charge and discharge of the positive electrode active material can be obtained.

[0099] The above x2 is -0.1 to 0.1. When the above range is satisfied, high capacity characteristics and high energy density per unit volume can be realized.

[0100] The above a2 is the mole fraction of iron (Fe) among all metals excluding lithium in the second phosphate, and is less than 0.5. Preferably, it may be 0.05 or more, 0.10 or more, 0.15 or more, or 0.20 or more, and less than 0.5, 0.45 or less, or 0.40 or less.

[0101] When the above a2 is 0.5 or more, the average content of manganese (Mn) in the positive electrode active material decreases, and the content of manganese (Mn) included in the shell is low, which causes a problem of reduced energy density. Therefore, when the above range is satisfied, excellent energy density can be achieved by relatively increasing the content of manganese (Mn) while greatly controlling the average particle size of the positive electrode material powder.

[0102] The above b2 is M among all metals except lithium in the second phosphate. 2The molar fraction may be 0.0 or more and 0.1 or less. Preferably, it may be 0.001 or more, 0.002 or more, 0.003 or more, 0.004 or more, 0.005 or more, 0.006 or more, 0.007 or more, 0.008 or more, or 0.009 or more, and may be 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less. When the above range is satisfied, ionic conductivity and electrical conductivity may be improved.

[0103] Preferably, the shell may include a second phosphate represented by the following chemical formula 2-1.

[0104] [Chemical Formula 2-1]

[0105] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0106] In the above chemical formula 2, M 2 It contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x2≤0.1, 0.2≤a2≤0.4, 0.0≤b2≤0.1.

[0107]

[0108] The molar ratio of Fe to Mn (Fe / Mn) in the positive electrode active material may be 0.4 to 2.4, preferably 0.42 to 2.34, and more preferably 0.66 to 1.5. The molar ratio of Fe to Mn (Fe / Mn) in the positive electrode active material may be different from the composition of the phosphate present in each of the core and / or the shell, and refers to the molar ratio of Fe to Mn in the positive electrode active material including the core and the shell. When the above range is satisfied, excellent charging output can be realized, while also achieving excellent energy density.

[0109]

[0110] The volume ratio of the core and shell may be 20:80 to 80:20, preferably 30:70 to 70:30, and more preferably 40:60 to 60:40. When the above range is satisfied, excellent charging output characteristics and energy density can be realized while greatly increasing the particle size.

[0111]

[0112] The above cathode material powder has an average particle diameter D 50 This may be 0.5㎛ to 2.0㎛, preferably 0.7㎛ to 1.5㎛, and more preferably 0.8㎛ to 1.2㎛. When the above range is satisfied, the press density of the positive electrode powder is high, so that a high-density electrode can be realized, and at the same time, the slurry solid content can be easily increased during electrode production, so that excellent energy density and processability can be realized, and excellent charge output characteristics can be realized, which is preferable. In addition, the positive electrode powder according to the present invention includes a lithium manganese iron phosphate compound rich in manganese (Mn), but is arranged in a shell layer in the positive electrode active material, so that even if the above-mentioned average particle size is satisfied, excellent charge output characteristics can be realized.

[0113]

[0114] The above cathode material powder has a BET specific surface area of ​​5 m 2 / g to 30m 2 / g can be, preferably 10m 2 / g to 25m 2 / g can be, more preferably 12m 2 / g to 20m 2 / g. When the above range is satisfied, it may be easy to increase the slurry solid content during electrode production, and it may be preferable in terms of excellent electrolyte impregnation properties.

[0115]

[0116] The above cathode material powder may have a press density measured after pressing at a pressure of 3 tons of 2.40 g / cc or more, preferably 2.40 g / cc to 3.00 g / cc, more preferably 2.45 g / cc to 2.90 g / cc, and even more preferably 2.46 g / cc to 2.80 g / cc. For example, the press density may be measured by collecting 1 g of the cathode material powder, placing it in a cylindrical metal mold having a diameter of 1.3 cm, and pressing it at a load of 3 tons. When the above range is satisfied, it is easy to manufacture a high-density electrode, and thus excellent energy density can be realized.

[0117]

[0118] The above cathode material powder may further include a coating layer comprising carbon disposed on the shell. When the above conditions are satisfied, the electronic conductivity of the cathode material powder may be improved.

[0119]

[0120] The content of carbon included in the above coating layer may be 0.1 wt% to 5.0 wt%, preferably 0.25 wt% to 4.0 wt%, and more preferably 0.5 wt% to 3.0 wt%, based on the total weight of the positive electrode powder. When the above range is satisfied, it may be preferable in that it may improve the electronic conductivity of the positive electrode powder without acting as a resistor.

[0121]

[0122] anode

[0123] Hereinafter, the anode according to the present invention will be described.

[0124] The positive electrode according to the present invention comprises the positive electrode material powder described above. Preferably, the positive electrode may comprise a positive electrode active material layer comprising the positive electrode material powder described above, and more preferably, a positive electrode current collector; and a positive electrode active material layer positioned on the positive electrode current collector and comprising the positive electrode active material described above.

[0125]

[0126] Hereinafter, each component of the anode according to the present invention will be described in detail.

[0127]

[0128] (1) Positive current collector

[0129] As the positive electrode current collector, various positive electrode current collectors used in the relevant technical field can be used. For example, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0130]

[0131] (2) Positive electrode active material layer

[0132] The positive electrode active material layer may be positioned on the positive electrode current collector, and preferably, may be positioned on one or both sides of the positive electrode current collector. The positive electrode active material layer may have a single layer or a multilayer structure of two or more layers.

[0133] The above positive electrode active material layer may include a positive electrode material powder, a positive electrode conductive material, and a positive electrode binder according to the present invention.

[0134] The positive electrode active material may be included in an amount of 90 wt% to 99 wt%, preferably 92 wt% to 98 wt%, and more preferably 94 wt% to 98 wt%, based on the total weight of the positive electrode active material layer. When the above range is satisfied, the energy density and capacity characteristics of a lithium secondary battery to which the positive electrode is applied can be improved.

[0135] The above-described positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples 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, and carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types of these may be used. The positive electrode conductive material may typically be included in an amount of 0.1 to 10 wt%, preferably 0.1 to 8 wt%, and more preferably 0.1 to 5 wt%, based on the total weight of the positive electrode active material layer.

[0136] The above positive electrode binder serves to improve adhesion between positive electrode particles and adhesion between the positive electrode and the positive electrode current collector, and specific examples thereof include a fluororesin binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber binder including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; a cellulose binder including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol binder including polyvinyl alcohol; a polyolefin binder including polyethylene and polypropylene; a polyimide binder; and a polyester binder. And silane binders, etc. can be mentioned, and one of these can be used alone or a mixture of two or more can be used. The positive electrode binder can be included in an amount of 1 to 10 wt%, preferably 0.5 to 10 wt%, and more preferably 1 to 8 wt% based on the total weight of the positive electrode active material layer.

[0137]

[0138] The positive electrode can be manufactured by a method known in the art. For example, the positive electrode can be manufactured by mixing positive electrode material powder, positive electrode binder, and positive electrode conductive material in a solvent to manufacture positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, drying, and rolling, or by casting the positive electrode slurry onto a separate support, peeling the support, and laminating the resulting film onto a positive electrode current collector. At this time, as the solvent of the positive electrode slurry, positive electrode slurry solvents generally used in the art can be used, and examples thereof include, but are not limited to, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or mixtures thereof. The solvent can be used in an amount that dissolves or disperses the positive electrode active material, positive electrode conductive material, and positive electrode binder, and has a viscosity that allows the negative electrode slurry to be uniformly coated.

[0139]

[0140] lithium secondary battery

[0141] Hereinafter, a lithium secondary battery according to the present invention will be described.

[0142] A lithium secondary battery according to the present invention comprises: a positive electrode according to the present invention; a negative electrode positioned opposite the positive electrode; and an electrolyte. Optionally, the lithium secondary battery according to the present invention may further comprise a separator interposed between the positive electrode and the negative electrode.

[0143] Since the above anode is the same as described above, the remaining components excluding the anode will be described below.

[0144]

[0145] (1) Cathode

[0146] In a lithium secondary battery according to the present invention, the negative electrode includes a negative electrode active material layer including a negative electrode active material, and specifically, may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.

[0147]

[0148] The negative electrode 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., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0149]

[0150] The negative electrode active material layer may be positioned on the negative electrode current collector, and specifically, may be positioned on one or both sides of the negative electrode current collector. The negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers.

[0151] When the negative electrode active material layer has a multilayer structure composed of two or more layers, each layer may have different types and / or contents of the negative electrode active material, negative electrode binder, and / or negative electrode conductive material. By forming the negative electrode active material layer into a multilayer structure and varying the composition of each layer, the performance characteristics of the battery, such as rapid charging performance and output characteristics, can be appropriately controlled.

[0152] Meanwhile, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0 <β< 2), metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used.

[0153] Meanwhile, both low-crystalline carbon and high-crystalline carbon can be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0154] Preferably, the negative electrode active material may be a carbon-based negative electrode active material, and at this time, the carbon-based negative electrode active material may include, for example, natural graphite, artificial graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or a combination thereof. More preferably, the carbon-based negative electrode active material may include natural graphite and artificial graphite.

[0155] The above carbon-based negative electrode active material has an average particle diameter D 50 This may be 0.1㎛ to 30㎛, preferably 0.5㎛ to 30㎛.

[0156] The above negative electrode active material may be included in an amount of 80 wt% to 98 wt%, preferably 90 wt% to 98 wt%, and more preferably 93 wt% to 98 wt%, based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies the above range, excellent energy density can be achieved.

[0157]

[0158] Meanwhile, the negative electrode active material layer may further include a negative electrode conductive material and / or a negative electrode binder together with the negative electrode active material.

[0159] The negative electrode conductive material is used to provide conductivity to the negative electrode, and can be used without any special restrictions as long as it does not cause a chemical change in the battery to be constructed and has electronic conductivity. Specific examples include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon fiber, and carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and among these, one type alone or a mixture of two or more types may be used.

[0160] The above negative electrode conductive material may be included in an amount of typically 0.1 to 10 wt%, preferably 0.1 to 8 wt%, and more preferably 0.1 to 5 wt%, based on the total weight of the negative electrode active material layer.

[0161] The above negative electrode binder serves to improve adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0162] The above negative electrode binder may be included in an amount of 0.1 to 10 wt%, preferably 0.5 to 10 wt%, and more preferably 1 to 8 wt%, based on the total weight of the negative electrode active material layer.

[0163]

[0164] The above negative electrode can be manufactured by a method known in the art. For example, the negative electrode can be manufactured by mixing a negative electrode active material, a negative electrode binder, and / or a negative electrode conductive material in a solvent to manufacture a negative electrode slurry, applying the negative electrode slurry onto a negative electrode current collector, and then drying and rolling the resulting film, or by casting the negative electrode slurry onto a separate support, and then peeling the resulting film from the support and laminating the resulting film onto a negative electrode current collector.

[0165] Meanwhile, solvents commonly used in the art may be used as the solvent for the negative electrode slurry, and examples thereof include, but are not limited to, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or mixtures thereof. The solvent may be used in an amount that dissolves or disperses the negative electrode active material, the negative electrode conductive material, and the negative electrode binder, and provides a viscosity that allows the negative electrode slurry to be uniformly coated.

[0166]

[0167] (2) Electrolyte

[0168] The electrolyte according to the present invention may include a lithium salt and an organic solvent.

[0169] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, 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 within the range of 0.1 to 5.0 M, and preferably 0.1 to 3.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0170]

[0171] The above organic solvent may include at least one of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent.

[0172] The above cyclic carbonate-based organic solvent is a high-viscosity organic solvent, and may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0173] In addition, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and representative examples thereof include at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and specifically, may include ethylmethyl carbonate (EMC).

[0174] Specific examples of the linear ester organic solvent include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0175] The above cyclic ester organic solvent may include at least one organic solvent selected from the group consisting of butyrolactone, valerolactone, and caprolactone.

[0176] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0177]

[0178] Meanwhile, in addition to the electrolyte components, the electrolyte may additionally include other additives for the purpose of improving the life characteristics of the battery, suppressing battery capacity reduction, and improving the discharge capacity of the battery.

[0179] These other additives may include, as representative examples, at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt included in the electrolyte.

[0180] Specifically, the other additives include vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, 1-methyl-1,3-propene sultone, ethylene sulfate (Esa), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), tetraphenylborate, lithium oxalyldifluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, One or more compounds selected from the group consisting of 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, fluorobenzene, triethanolamine, ethylenediamine, tetravinylsilane, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF3)2 (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bisoxalatoborate (LiB(C2O4)2) and LiBF4) may be mentioned.

[0181] The above-mentioned other additives may be included in an amount of 0.01 to 20 wt% based on the total weight of the electrolyte, and preferably 0.05 to 5.0 wt%. If the content of the above-mentioned other additives is less than 0.01 wt%, the effects of improving the low-temperature output of the battery and the high-temperature storage characteristics and high-temperature life characteristics are minimal, and if the content of the above-mentioned other additives exceeds 20 wt%, there is a possibility that excessive side reactions occur in the electrolyte during charge and discharge of the battery. In particular, when the above-mentioned SEI film forming additives are added in excessive amounts, they may not be sufficiently decomposed at high temperatures and may exist as unreacted substances or precipitated substances in the electrolyte at room temperature. Accordingly, side reactions that reduce the life or resistance characteristics of the secondary battery may occur.

[0182]

[0183] (3) Membrane

[0184] The above separator physically separates the anode and cathode and provides a passage for lithium ions to move. Any separator typically used in lithium secondary batteries may be used without any special restrictions. In this case, the separator may be interposed between the cathode and cathode.

[0185] Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, 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, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0186]

[0187] The lithium secondary battery according to the present invention as described above can be usefully applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs). Since the lithium secondary battery according to the present invention can realize excellent output characteristics even under low-temperature conditions, it can be particularly usefully used in the electric vehicle field.

[0188] According to another embodiment of the present invention, a battery module including a lithium secondary battery according to the present invention as a unit cell and a battery pack including the same are provided.

[0189] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0190]

[0191] Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are intended to enable those skilled in the art to fully understand and easily practice the present invention, and the scope of the present invention is not limited to the following examples.

[0192]

[0193] Example 1

[0194] Li2CO3, MnCO3, FeC2O4, (NH4)2HPO4 were mixed in an aqueous solution at a molar ratio of 0.5:0.3:0.7:1, and calcined at 180℃ for 12 hours to obtain LiMn 0.3 Fe 0.7 PO4 was manufactured.

[0195] After that, an aqueous solution containing Li2CO3, MnCO3, FeC2O4, (NH4)2HPO4 in a molar ratio of 0.5:0.7:0.3:1 and the obtained LiMn 0.3 Fe 0.7 After mixing PO4 in an aqueous solution and calcining at 180℃ for 12 hours, the composition of the core is LiMn 0.3 Fe 0.7 PO4, and the composition of the shell is LiMn 0.7 Fe 0.3 A phosphorus oxide called PO4 was prepared.

[0196] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and heat-treated at 700°C for 12 hours to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0197] Afterwards, the phosphorus oxide having a carbon coating layer formed was pulverized and classified to produce cathode powder.

[0198]

[0199] Comparative Example 1

[0200] Li2CO3, MnCO3, FeC2O4, (NH4)2HPO4 were mixed in an aqueous solution at a molar ratio of 0.5:0.6:0.4:1, and calcined at 180℃ for 12 hours to obtain LiMn 0.6 Fe 0.4 PO4 was manufactured.

[0201] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and heat-treated at 700°C for 12 hours to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0202] Afterwards, the phosphorus oxide having a carbon coating layer formed was pulverized and classified to produce cathode powder.

[0203]

[0204] Comparative Example 2

[0205] LiFePO4 was manufactured by mixing Li2CO3, FeC2O4, and (NH4)2HPO4 in an aqueous solution at a molar ratio of 0.5:1:1 and calcining at 180°C for 12 hours.

[0206] After that, the obtained LiFePO4 was mixed with an aqueous solution containing Li2CO3, MnCO3, (NH4)2HPO4 in a molar ratio of 0.5:1:1 in the aqueous solution phase, and then calcined at 180°C for 12 hours to manufacture a phosphorus oxide having a core composition of LiFePO4 and a shell composition of LiMnPO4.

[0207] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and heat-treated at 700°C for 12 hours to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0208] Afterwards, the phosphorus oxide having a carbon coating layer formed was pulverized and classified to produce cathode powder.

[0209]

[0210] Comparative Example 3

[0211] LiMnPO4 was prepared by mixing Li2CO3, MnCO3, and (NH4)2HPO4 in an aqueous solution at a molar ratio of 0.5:1:1 and calcining at 180°C for 12 hours.

[0212] After that, the obtained LiMnPO4 was mixed with an aqueous solution containing Li2CO3, FeC2O4, and (NH4)2HPO4 in a molar ratio of 0.5:1:1 in the aqueous solution phase, and then calcined at 180°C for 12 hours to manufacture a phosphorus oxide having a core composition of LiMnPO4 and a shell composition of LiFePO4.

[0213] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and heat-treated at 700°C for 12 hours to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0214] Afterwards, the phosphorus oxide having a carbon coating layer formed was pulverized and classified to produce cathode powder.

[0215]

[0216] Average particle diameter D of the manufactured cathode material powder 50 After measuring the BET surface area, the cathode material powders mentioned above were organized and shown in Table 1 below.

[0217]

[0218] Composition of the positive electrode powder coreComposition of the shellMolar ratio of Fe to Mn in the positive electrode active material (Fe / Mn)Average particle size D 50 (㎛)BET specific surface area (m 2 / g) Example 1 LiMn 0.3 Fe 0.7 PO4LiMn 0.7 Fe 0.3 PO40.670.8812Comparative Example 1LiMn 0.6 Fe 0.4 PO40.670.4816Comparative Example 2LiFePO4LiMnPO40.670.8912Comparative Example 3LiMnPO4LiFePO40.670.8812

[0219] Experimental Example 1: Press Density Measurement

[0220] After collecting 1 g of the cathode material powder manufactured in Example 1 and Comparative Examples 1 to 3, it was placed in a cylindrical metal mold with a diameter of 1.3 cm and pressed with a load of 3 tons. Thereafter, the height of the pressed mold was measured using a vernier caliper to determine the press density.

[0221] The measurement results are shown in [Table 2] below.

[0222]

[0223] Experimental Example 2: Evaluation of Charging Rate Characteristics

[0224] 1) Manufacturing of lithium secondary battery half cells

[0225] Each of the cathode material powders manufactured in Example 1 and Comparative Examples 1 to 3, the cathode conductive material (Super P), and the cathode binder (PVdF) were mixed in a weight ratio of 95:2:3 in N-methyl pyrrolidone to prepare a cathode slurry. The cathode slurry was applied onto an aluminum current collector, dried, and rolled to prepare a cathode.

[0226] Lithium metal was used as the cathode.

[0227] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive and negative electrodes manufactured as described above, and the electrode assembly was placed inside a case, and an electrolyte was injected into the case to manufacture a lithium secondary battery. At this time, the electrolyte was manufactured by dissolving 1.2 M lithium hexafluorophosphate (LiPF6) in an organic solvent mixed with ethylene carbonate and dimethyl carbonate at a weight ratio of 3:7.

[0228]

[0229] 2) Evaluation of charging rate characteristics

[0230] After activating the above-mentioned manufactured lithium secondary batteries, they were charged at a constant current of 0.1 C at 25°C until the voltage reached 4.2 V, and then discharged at a constant current of 0.1 C until the voltage reached 2.5 V, and the 0.1 C charge capacity was measured.

[0231] Afterwards, the battery was charged to 4.2 V with a constant current of 2.0 C and the 2.0 C charge capacity was measured.

[0232] Using the measured 0.1C and 2.0C charging capacities, the charging rate characteristics were evaluated as follows.

[0233] Charge rate characteristics (%): (2.0C charge capacity) / (0.1C charge capacity) × 100

[0234]

[0235] The measurement results are shown in [Table 2] below.

[0236]

[0237] Press density (g / cc) Filling rate characteristics (%) Example 12.4679.7 Comparative example 12.3977.5 Comparative example 22.4577.6 Comparative example 32.4669.1

[0238] Through the above Table 2, it can be seen that the positive electrode powder that satisfies the composition of the phosphorus oxides included in the core and shell according to the present invention has a superior press density than the positive electrode powder that does not.

[0239] In addition, it can be seen that in the case of a lithium secondary battery using a cathode material powder that satisfies the composition of phosphorus oxides included in the core and shell according to the present invention, the charge rate characteristics are superior to those of a lithium secondary battery that does not.

Claims

1. A cathode powder containing a cathode active material, The above positive electrode active material includes a core; and a shell disposed on the surface of the core; The above core comprises a first phosphate represented by the following chemical formula 1, The above shell is a cathode powder comprising a second phosphate represented by the following chemical formula 2: [Chemical Formula 1] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4 In the above chemical formula 1, M 1 Contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x1≤0.1, 0.5 <a1<1.0, 0.0≤b1≤0.1이며, [Chemical Formula 2] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4 In the above chemical formula 2, M 2 It includes at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x2≤0.1, 0.0≤a2<0.5, 0.0≤b2≤0.

1.

2. In claim 1, The above first phosphate is a cathode material powder represented by the following chemical formula 1-1: [Chemical Formula 1-1] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4 In the above chemical formula 1, M 1 It contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x1≤0.1, 0.6≤a1≤0.8, 0.0≤b1≤0.

1.

3. In claim 1, The above second phosphorus oxide is a cathode material powder represented by the following chemical formula 2-1: [Chemical Formula 2-1] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4 In the above chemical formula 2, M 2 It contains at least one selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y, and -0.1≤x2≤0.1, 0.2≤a2≤0.4, 0.0≤b2≤0.

1.

4. In claim 1, A cathode material powder having a molar ratio of Fe to Mn (Fe / Mn) in the cathode active material of 0.4 to 2.

4.

5. In claim 1, A cathode material powder having a volume ratio of the core and shell of 20:80 to 80:

20.

6. In claim 1, The above cathode material powder has an average particle diameter D 50 This positive electrode powder is 0.5㎛ to 2.0㎛.

7. In claim 1, The above cathode material powder has a BET specific surface area of ​​5 m 2 / g to 30m 2 / g, positive electrode powder.

8. In claim 1, The above cathode material powder is a cathode material powder having a press density of 2.40 g / cc or more measured after pressing at a pressure of 3 tons.

9. In claim 1, The cathode material powder further comprises a coating layer comprising carbon disposed on the shell.

10. In claim 9, A cathode material powder having a carbon content included in the coating layer of 0.1 wt% to 5.0 wt% based on the total weight of the cathode active material.

11. A cathode comprising the cathode material powder of claim 1.

12. A lithium secondary battery comprising: a positive electrode of claim 11; a negative electrode disposed opposite the positive electrode; and an electrolyte.