Positive electrode material powder, positive electrode and lithium secondary battery comprising the same

Abstract

The present invention relates to an anode material powder comprising: a first anode active material comprising a first phosphate; and a second anode active material comprising a second phosphate; wherein the first phosphate is represented by a specific chemical formula 1 and the second phosphate is represented by a specific chemical formula 2, and the first anode active material is contained in greater quantities than the second anode active material, and the second anode active material has an average particle size D50 of 1.0 μm or less.

Description

Technology Field

[0001] The present invention relates to a positive electrode powder, a positive electrode containing the same, and a lithium secondary battery. Background Technology

[0003] A lithium secondary battery is generally manufactured by forming an electrode assembly by interposing a separator between a positive electrode containing a positive active material containing lithium and a negative electrode containing a negative 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 transmitting lithium ions, and then sealing it.

[0004] These lithium-ion batteries are used not only in portable electronic devices such as mobile phones and laptops but also in electric vehicles, and demand is surging recently due to the expansion of electric vehicle adoption. In particular, lithium-ion batteries used in electric vehicles require high energy density and thermal stability.

[0005] Meanwhile, lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium nickel-cobalt-manganese-based oxides, lithium manganese phosphate compounds, and lithium iron phosphate compounds are used as positive electrode active materials for lithium secondary batteries.

[0006] Among these, lithium iron phosphate-based compounds are widely used as cathode active materials for lithium secondary batteries due to their excellent thermal stability, superior lifespan characteristics, safety, and low cost; however, they have problems such as low operating voltage, relatively high energy density compared to other compounds, and difficulty in achieving excellent pressure density.

[0007] Therefore, there is a need to develop cathode powder capable of achieving excellent energy density and press density while realizing the advantages of lithium iron phosphate-based compounds, which possess superior lifespan characteristics and safety due to their excellent thermal stability. The problem to be solved

[0009] One objective of the present invention is to solve the above-mentioned problems, wherein the cathode material powder comprises a first cathode active material having a low manganese (Mn) content and a second cathode active material having a high manganese (Mn) content, wherein the first cathode active material is included in excess of the second cathode active material, and the average particle size D of the second cathode active material 50 By controlling the pressure to 1.0㎛ or less, the invention provides a cathode powder with excellent energy density, high discharge capacity and nominal voltage, while maintaining excellent press density.

[0011] In addition, another objective of the present invention is to solve the above-mentioned problems by providing a positive electrode and a lithium secondary battery comprising the positive electrode powder. means of solving the problem

[0013] [1] The present invention relates to a cathode material powder comprising: a first cathode active material comprising a first phosphate; and a second cathode active material comprising a second phosphate; wherein the first phosphate is represented by the following chemical formula 1 and the second phosphate is represented by the following chemical formula 2, and the first cathode active material is contained in greater quantities than the second cathode active material, and the second cathode active material has an average particle size D 50 This provides a cathode material powder having a thickness of 1.0㎛ or less.

[0014] [Chemical Formula 1]

[0015] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0016] In the above chemical formula 1,

[0017] M 1 It comprises one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and

[0018] -0.1≤x1≤0.1, 0.9≤a1≤1.0, 0.0≤b1≤0.1, and

[0019] [Chemical Formula 2]

[0020] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0021] In the above chemical formula 2,

[0022] M 2 It comprises one or more elements selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and

[0023] -0.1≤x2≤0.1, 0.2≤a2≤0.5, 0.0≤b2≤0.1.

[0024] [2] In the present invention [1], the first phosphoric acid may be LiFePO4.

[0025] [3] In the present invention [1] or [2], the second phosphate may be represented by the following chemical formula 2-1.

[0026] [Chemical Formula 2-1]

[0027] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0028] In the above chemical formula 2,

[0029] M 2 It comprises one or more elements selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and

[0030] -0.1≤x2≤0.1, 0.35≤a2≤0.45, 0.0≤b2≤0.1.

[0031] [4] In at least one of [1] to [3] above, the present invention is such that the first positive active material has an average particle size D 50 This can be 0.5㎛ to 10㎛.

[0032] [5] In at least one of [1] to [4] above, the present invention is such that the second positive active material has an average particle size D 50 This can be 0.3㎛ to 0.8㎛.

[0033] [6] In at least one of [1] to [5], the present invention may further include a coating layer comprising carbon disposed on the first and second phosphates, respectively, in which the first and second positive active materials are independently disposed.

[0034] [7] In the present invention [1] to [6], the carbon content in the coating layer containing carbon disposed on the first phosphate may be 0.1% to 5.0% by weight based on the total weight of the first positive active material.

[0035] [8] In the present invention [1] to [7], the carbon content in the coating layer containing carbon disposed on the second phosphate may be 0.5% to 5.0% by weight based on the total weight of the second positive active material.

[0036] [9] In at least one of [1] to [8], the weight ratio of the first positive active material and the second positive active material may be 60:40 to 90:10.

[0037]

[10] The present invention, in at least one of [1] to [9], wherein the average particle size D of the first positive active material 50 The average particle size D of the second positive active material is 50 It can be bigger.

[0038]

[11] In at least one of [1] to

[10] of the present invention, the molar ratio of Fe to Mn in the cathode material powder (Fe / Mn) may be 2.5 to 50.

[0039]

[12] In at least one of [1] to

[11] , the present invention may have a press density of 2.50 g / cc or more after pressing with a pressure of 3 ton.

[0040]

[13] The present invention provides an anode comprising an anode material powder according to at least one of [1] to

[12] .

[0041]

[14] The present invention provides a lithium secondary battery comprising: an anode according to

[13] ; a cathode positioned opposite to the anode; and an electrolyte. Effects of the invention

[0043] The cathode material powder according to the present invention comprises a first cathode active material comprising a phosphorylate represented by Formula 1 and a second cathode active material comprising a phosphorylate represented by Formula 2, wherein the first and second cathode active materials are included in a specific weight ratio, and the average particle size D of the second cathode active material 50 It is characterized by being 1.0 μm or less. The phosphate represented by Chemical Formula 1 has high electron conductivity, lithium ion conductivity, and discharge capacity, and the phosphate represented by Chemical Formula 2 has a high operating voltage. At this time, the first positive active material containing the phosphate represented by Chemical Formula 1 is included in a larger amount than the second positive active material to increase the press density, discharge capacity, and nominal voltage, while the average particle size D of the second positive active material 50 By controlling it, the press density can be further increased. Therefore, when the cathode material powder according to the present invention is applied, the energy density of the lithium secondary battery can be improved. Specific details for implementing the invention

[0045] The present invention will be described in more detail below.

[0046] Terms and words used in this specification and claims 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 invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0047] The terms used in this invention are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0048] In the present invention, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0049] In the present invention, "single particle type" refers to a particle formed by the aggregation of 50 or fewer sub-particles. The sub-particle unit constituting the single particle type is referred to as a nodule. Single particle type particles include a single particle consisting of one nodule and a pseudo-single particle which is a composite of 2 to 50 nodules.

[0050] The above “nodule” is a sub-particle unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline material that does not appear to have grain boundaries when observed at a field of view of 2,000 to 20,000 times using a scanning electron microscope.

[0051] In the present invention, "secondary particle" refers to a particle formed by the aggregation of more than 50 sub-particles. To distinguish it from the sub-particles constituting a single-particle type particle, the sub-particles constituting the secondary particle are called "primary particles."

[0052] In the present invention, the term “particle” is a concept that includes any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0053] In the present invention, the “BET specific surface area” is measured by the BET method, and specifically, can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BEL Japan’s BELSORP-mino II.

[0054] In the present invention, "average particle size D 50 "It refers to the particle size at the 50% standard of the volumetric cumulative particle size distribution of the particles. The above average particle size D 50 It can be measured using the laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0056] As a result of repeated research to improve the energy density of a lithium secondary battery, the inventors have provided a first positive electrode active material containing a phosphorus oxide with a high iron (Fe) content, which is included in a larger amount than a second positive electrode active material containing a phosphorus oxide with a relatively high manganese (Mn) content, wherein the average particle size D of the second positive electrode active material 50 The present invention was completed by discovering that the energy density (Wh / L) of a lithium secondary battery can be improved by applying a cathode material powder controlled to 1.0㎛ or less.

[0058] The present invention will be described in detail below.

[0059] The cathode material powder according to the present invention, the cathode including the same, and the lithium secondary battery comprise at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0061] Cathode material powder

[0062] Hereinafter, the anode material powder according to the present invention will be described.

[0063] The cathode material powder according to the present invention comprises: a first cathode active material comprising a first phosphate; and a second cathode active material comprising a second phosphate; wherein the first phosphate is represented by the following chemical formula 1 and the second phosphate is represented by the following chemical formula 2, the first cathode active material is contained in greater quantities than the second cathode active material, and the second cathode active material has an average particle size D 50 This is 1.0㎛ or less.

[0064] [Chemical Formula 1]

[0065] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0066] In the above chemical formula 1,

[0067] M 1 It comprises one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and

[0068] -0.1≤x1≤0.1, 0.9≤a1≤1.0, 0.0≤b1≤0.1, and

[0069] [Chemical Formula 2]

[0070] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0071] In the above chemical formula 2,

[0072] M 2 It comprises one or more elements selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and

[0073] -0.1≤x2≤0.1, 0.2≤a2≤0.5, 0.0≤b2≤0.1.

[0075] In the case of lithium manganese phosphate and lithium iron phosphate compounds having an olivine structure, they have one-dimensional lithium ion diffusion pathways within the crystal structure, which results in low lithium ion conductivity during charging and discharging. Therefore, charging and discharging can be performed even at high power levels only if the average particle size of the compound is controlled to the level of tens to hundreds of nanometers. 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 because it is difficult to realize a high-density electrode due to the disadvantage of rolling.

[0076] In particular, lithium iron phosphate-based compounds exhibit superior charge output compared to lithium manganese phosphate-based compounds due to their higher electronic and lithium ion conductivity. Consequently, even with relatively large average particle sizes, the impact on battery performance is minimal, enabling the realization of high-density electrodes; however, there is a problem of low energy density resulting from the low operating voltage.

[0077] Conversely, while lithium manganese phosphate-based compounds have high energy density due to their high operating voltage, they have poor charge output characteristics, which limits the ability to increase the average particle size of the compound and thus presents a problem in that it is difficult to realize high-density electrodes.

[0078] To address this, lithium iron manganese phosphate compounds in which the molar ratio of iron to manganese in the lithium phosphate is controlled (e.g., LiMn x Fe (1-x)Although the use of PO4 as a cathode active material has been proposed, there is a problem in that it is difficult to overcome the trade-off relationship between the advantages and disadvantages of the aforementioned lithium iron phosphate-based compounds and lithium manganese phosphate-based compounds, respectively.

[0079] Accordingly, to solve the aforementioned problem, the present invention comprises a first positive electrode active material containing a phosphoric acid with a high iron content (low manganese content) and a second positive electrode active material containing a phosphoric acid with a relatively high manganese content (low iron content), wherein the first positive electrode active material is included in greater quantities than the second positive electrode active material, and the second positive electrode active material has an average particle size D 50 We intend to apply this cathode material powder, which is 1.0㎛ or smaller, to lithium secondary batteries.

[0080] In this case, the first cathode active material with a high iron content (low manganese content) exhibits excellent charge output and superior discharge capacity (mAh / g) even when the average particle size is increased, while the second cathode active material with a high manganese content (low iron content) exhibits excellent operating voltage despite having a small average particle size. That is, if the first cathode active material possessing the above characteristics is included in a larger amount than the second cathode active material in the cathode powder, the energy density (Wh / L), which is the product of press density (g / cc), discharge capacity (mAh / g), and nominal voltage (V), is maximized, thereby enabling the production of a cathode powder capable of realizing excellent energy density.

[0081] Conversely, if the second positive active material is included in the positive material powder in an amount equal to the weight of the first positive active material, or if the second positive active material is included in a larger amount than the first positive active material, the nominal voltage is somewhat high due to the excess of the second positive active material; however, since the second positive active material cannot be properly mixed between the first positive active materials, the press density is low and the discharge capacity is small, resulting in a problem where the final energy density decreases.

[0082] Furthermore, when the cathode powder contains the first cathode active material alone, the discharge capacity is somewhat high, but since the second cathode active material is not included, the press density and nominal voltage are lowered, resulting in a problem of ultimately reduced energy density. Conversely, when the cathode powder contains the second cathode active material alone, the nominal voltage is somewhat high, but since the first cathode active material is not included, the press density and discharge capacity are lowered, resulting in a problem of ultimately reduced energy density.

[0083] Meanwhile, while including the first positive active material in the positive material powder in greater quantities than the second positive active material, the average particle size D of the second positive active material 50 If this exceeds 1.0㎛, it is difficult to improve energy density. Specifically, the average particle size D of the second cathode active material 50 If this exceeds 1.0㎛, the relatively large empty space between particles in the cathode material powder may result in a decrease in the press density of the cathode material powder, and the excessively large particle size restricts the rearrangement between particles in the cathode material powder, making it difficult to form a sufficiently dense structure during electrode rolling, which causes a problem of reduced energy density of the battery.

[0084] Accordingly, the first positive electrode active material comprising a phosphoric acid having a high iron content (low manganese content) and the second positive electrode active material comprising a phosphoric acid having a relatively high manganese content (low iron content), wherein the first positive electrode active material is included in greater quantities than the second positive electrode active material, and the average particle size D of the second positive electrode active material 50 By controlling it to 1.0㎛ or less, excellent energy density can be achieved while achieving excellent press density.

[0086] Hereinafter, the cathode material powder according to the present invention will be described in more detail.

[0088] (1) First positive active material

[0089] In the cathode material powder according to the present invention, the cathode material powder comprises a first cathode active material comprising a first phosphoric acid, and the first phosphoric acid is represented by the following chemical formula 1.

[0090] [Chemical Formula 1]

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

[0092] In the above chemical formula 1, M 1 The composition includes one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, preferably one or more selected from the group consisting of Mg, Ti, V, and Nb, and more preferably one or more selected from the group consisting of Ti and V. When the above conditions are satisfied, effects such as suppression of structural changes during repeated charging and discharging of the positive electrode active material can be obtained.

[0093] The above x1 is from -0.1 to 0.1. If the above range is satisfied, high capacity characteristics and high energy density per unit volume can be realized.

[0094] The above a1 is the mole fraction of iron (Fe) among the total metals excluding lithium in the first phosphate, and is 0.9 to 1.0. Preferably, it may be 0.9 or higher, 0.92 or higher, 0.95 or higher, 0.97 or higher, or 0.99 or higher, and may be 1.0 or lower, and more preferably, the above a1 may be 1.0.

[0095] If the above a1 is less than 0.9, there is a problem that the output characteristics may be poor due to low electron conductivity and lithium ion conductivity in the phosphate, and there is a limit to increasing the average particle size. Therefore, if the above range is satisfied, it may be desirable in that it is possible to realize a high-density electrode by appropriately increasing the average particle size while maintaining excellent output characteristics.

[0096] The above b1 is M among the total metals excluding lithium in the first phosphate. 1 The mole fraction may be 0.0 to 0.1. 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.

[0097] Preferably, the first phosphate may be LiFePO4.

[0099] According to one embodiment of the present invention, the first positive active material has an average particle size D 50 This can be 0.5㎛ to 10㎛, preferably 0.6㎛ to 7㎛, and more preferably 0.7㎛ to 5㎛. When the above range is satisfied, the first positive electrode active material can be appropriately distributed within the positive electrode powder, thereby enabling the realization of a high-density electrode, while also making it easy to increase the slurry solid content during electrode fabrication, which enables the realization of excellent energy density and processability, and is desirable in terms of achieving excellent discharge capacity.

[0101] According to one embodiment of the present invention, the first positive active material has a BET specific surface area of ​​1 m² 2 / g to 30m 2It can be / g, and preferably 3m 2 / g to 20m 2 It can be / g, and more preferably 5m 2 / g to 15m 2 It may be / g. If the above range is satisfied, it may be advantageous in terms of making it easier to increase the slurry solid content during electrode fabrication and having excellent electrolyte impregnation properties.

[0103] According to one embodiment of the present invention, the first positive active material may be of a single particle type. Preferably, the first positive active material may be of a single particle type comprising 1 to 50 nodules, more preferably may be of a single particle type comprising 1 to 40 nodules, even more preferably may be of a single particle type comprising 1 to 30 nodules, even more preferably may be of a single particle type comprising 1 to 25 nodules, and even more preferably may be of a single particle type comprising 1 to 15 nodules. When the above conditions are satisfied, the contact area with the electrolyte is small, so there may be fewer side reactions with the electrolyte, excellent energy density may be achieved due to fewer pores within the particles, and durability may be improved due to a stable particle structure.

[0105] According to one embodiment of the present invention, the first positive electrode active material may further include a coating layer comprising carbon disposed on the first phosphate. When the above conditions are satisfied, the electronic conductivity of the positive electrode powder may be improved.

[0107] According to one embodiment of the present invention, the carbon content included in the coating layer containing carbon disposed on the first phosphate may be 0.1% to 5.0% by weight based on the total weight of the first positive active material, preferably 0.25% to 4.0% by weight, and more preferably 0.5% to 3.0% by weight. Satisfying the above range may be desirable in that it can improve the electronic conductivity of the first positive active material without acting as a resistor.

[0109] (2) Second positive active material

[0110] In the cathode material powder according to the present invention, the cathode material powder comprises a second cathode active material comprising a second phosphate, and the second phosphate is represented by the following chemical formula 2.

[0111] [Chemical Formula 2]

[0112] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0113] In the above chemical formula 2, M 2 It comprises one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, preferably, it may comprise one or more selected from the group consisting of Mg, Ti, V, and Nb, and more preferably, it may comprise one or more selected from the group consisting of Ti and V. When the above conditions are satisfied, effects such as suppression of structural changes during repeated charging and discharging of the positive electrode active material can be obtained.

[0114] The above x2 is from -0.1 to 0.1. If the above range is satisfied, high capacity characteristics and high energy density per unit volume can be realized.

[0115] The above a2 is the mole fraction of iron (Fe) among the total metals excluding lithium in the second phosphate, and is 0.2 to 0.5. Preferably, it may be 0.2 or more, 0.25 or more, 0.30 or more, or 0.35 or more, and may be 0.5 or less, 0.47 or less, or 0.45 or less, and more preferably, the above a2 may be 0.35 to 0.45.

[0116] If the above a2 is less than 0.2, the electron conductivity and lithium ion conductivity within the phosphoric acid are low, which may result in poor output characteristics, a small discharge capacity, and a limitation in increasing the average particle size. If the above a2 is greater than 0.5, the operating voltage is low, which may reduce energy density. Therefore, satisfying the above range may be desirable in that it allows for excellent output characteristics and enables the realization of a high-density electrode by appropriately increasing the average particle size.

[0117] The above b2 is M among the total metals excluding lithium in the first phosphate. 2 The mole fraction may be 0.0 to 0.1. 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.

[0118] Preferably, the second phosphate can be represented by the following chemical formula 2-1.

[0119] [Chemical Formula 2-1]

[0120] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2]PO4

[0121] In the above chemical formula 2,

[0122] M 2 It contains one or more elements 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, 0.35≤a2≤0.45, 0.0≤b2≤0.1.

[0124] According to one embodiment of the present invention, the second positive active material has an average particle size D 50 This is 1.0㎛ or less. Preferably, it may be 0.1㎛ or more, 0.15㎛ or more, 0.20㎛ or more, 0.25㎛ or more, or 0.30㎛ or more, and may be 1.0㎛ or less, 0.95㎛ or less, 0.90㎛ or less, 0.85㎛ or less, or 0.80㎛ or less, and more preferably, 0.3㎛ to 0.8㎛. When satisfying the above range, the second positive active material can be appropriately distributed within the positive material powder, thereby enabling the realization of a high-density electrode, while also facilitating the increase of slurry solid content during electrode fabrication, which enables the realization of excellent energy density and processability, and excellent discharge capacity.

[0126] According to one embodiment of the present invention, the second positive active material has a BET specific surface area of ​​1 m² 2 / g to 30m 2 It can be / g, preferably 2m 2 / g to 25m 2 It can be / g, and more preferably 5m 2 / g to 20m 2 It may be / g. If the above range is satisfied, it may be advantageous in terms of making it easier to increase the slurry solid content during electrode fabrication and having excellent electrolyte impregnation properties.

[0128] According to one embodiment of the present invention, the second positive active material may be of a single particle type. Preferably, the second positive active material may be of a single particle type comprising 1 to 50 nodules, more preferably may be of a single particle type comprising 1 to 40 nodules, even more preferably may be of a single particle type comprising 1 to 30 nodules, even more preferably may be of a single particle type comprising 1 to 25 nodules, and even more preferably may be of a single particle type comprising 1 to 15 nodules. When the above conditions are satisfied, the contact area with the electrolyte is small, so there may be fewer side reactions with the electrolyte, excellent energy density may be achieved due to fewer pores within the particles, and durability may be improved due to a stable particle structure.

[0130] According to one embodiment of the present invention, the second positive electrode active material may further include a coating layer comprising carbon disposed on the second phosphate. When the above conditions are satisfied, the electronic conductivity of the positive electrode powder may be improved.

[0132] According to one embodiment of the present invention, the carbon content included in the coating layer containing carbon disposed on the second phosphate may be 0.5% to 5.0% by weight based on the total weight of the first positive active material, preferably 0.8% to 4.0% by weight, and more preferably 1.0% to 3.0% by weight. Satisfying the above range may be desirable in that it can improve the electronic conductivity of the first positive active material without acting as a resistor.

[0134] According to one embodiment of the present invention, the first and second positive electrode active materials may each independently include a coating layer comprising carbon disposed on the first and second phosphates.

[0136] The cathode material powder according to the present invention contains more of the first cathode active material than the second cathode active material. Preferably, the weight ratio of the first cathode active material and the second cathode active material may be 55:45 to 95:5, and more preferably 60:40 to 90:10. When the above range is satisfied, the first cathode active material and the second cathode active material are appropriately mixed, so that the energy density is excellent, with high discharge capacity and nominal voltage.

[0138] According to one embodiment of the present invention, the average particle size D of the first positive active material 50 The average particle size D of the second positive active material is 50 It can be larger. When the above conditions are satisfied, unlike the second positive active material in which electron conductivity and lithium ion conductivity decrease when the average particle size is large, the electron conductivity and lithium ion conductivity of the first positive active material are not decreased, and the second positive active material with a small average particle size can adequately fill the voids between the first positive active materials with a large average particle size, so excellent press density can be achieved and excellent energy density characteristics can be realized.

[0140] According to one embodiment of the present invention, the molar ratio of Fe to Mn (Fe / Mn) in the cathode material powder may be 2.5 to 50, preferably 3.5 to 20, and more preferably 4.5 to 10. The molar ratio of Fe to Mn (Fe / Mn) in the cathode material powder may differ from the composition of the phosphate present in the first cathode active material and / or the second cathode active material, respectively. When the above range is satisfied, excellent energy density can be achieved.

[0142] According to one embodiment of the present invention, the pressing density of the cathode material powder measured after pressing with a pressure of 3 ton may be 2.50 g / cc or higher, preferably 2.50 g / cc to 3.00 g / cc, more preferably 2.52 g / cc to 2.90 g / cc, and even more preferably 2.54 g / cc to 2.80 g / cc. For example, the pressing density may be measured by taking 1 g of the cathode material powder, placing it in a cylindrical metal mold with a diameter of 1.3 cm, and pressing it with a load of 3 ton. When the above range is satisfied, it is easy to manufacture a high-density electrode, thereby enabling the realization of excellent energy density.

[0144] anode

[0145] Hereinafter, the anode according to the present invention will be described.

[0146] The anode according to the present invention comprises the aforementioned anode material powder. Preferably, the anode may comprise an anode active material layer comprising the aforementioned anode material powder, and more preferably, may comprise an anode current collector; and an anode active material layer located on the anode current collector and comprising the aforementioned anode active material.

[0148] Hereinafter, each component of the anode according to the present invention will be described in detail.

[0150] (1) Positive current collector

[0151] Various positive current collectors used in the relevant technical field may be used as the positive current collector. For example, the positive 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 current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. The positive current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0153] (2) Positive active material layer

[0154] The positive active material layer may be located on the positive current collector, and preferably, may be located on one or both sides of the positive current collector. The positive active material layer may be a single layer or a multilayer structure of two or more layers.

[0155] The above positive active material layer may include a positive material powder, a positive conductive material, and a positive binder according to the present invention.

[0156] The above positive active material may be included in an amount of 90% to 99% by weight, preferably 92% to 98% by weight, and more preferably 94% to 98% by weight, based on the total weight of the positive active material layer. If the above range is satisfied, the energy density and capacity characteristics of the lithium secondary battery to which the positive material is applied can be improved.

[0157] The above-mentioned positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. 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, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; 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. The above-mentioned positive electrode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the positive electrode active material layer.

[0158] The above-mentioned anode binder serves to improve adhesion between anode material particles and adhesion between the anode material and the anode current collector. Specific examples include fluoropolymer-based binders comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose-based binders comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol-based binders comprising polyvinyl alcohol; polyolefin-based binders comprising polyethylene or polypropylene; polyimide-based binders; and polyester-based binders. Examples include silane-based binders, and one of these alone or a mixture of two or more may be used. The anode binder may be included in an amount of 1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the anode active material layer.

[0160] The anode may be manufactured by methods known in the art. For example, the anode may be manufactured by mixing anode material powder, an anode binder, and an anode conductive material in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling, or by casting the anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector. In this case, the solvent for the anode slurry may be any anode slurry solvents generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or a mixture thereof, but is not limited thereto. The solvent may be used in an amount that dissolves or disperses the anode active material, the anode conductive material, and the anode binder, and has a viscosity such that the cathode slurry can be uniformly coated.

[0162] lithium secondary battery

[0163] Hereinafter, a lithium secondary battery according to the present invention will be described.

[0164] A lithium secondary battery according to the present invention comprises: a positive electrode according to the present invention; a negative electrode disposed opposite to 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.

[0165] Since the anode above is the same as described above, the remaining components excluding the anode will be described below.

[0167] (1) Cathode

[0168] In a lithium secondary battery according to the present invention, the negative electrode comprises 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.

[0170] The above-mentioned negative 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 above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0172] The above negative electrode active material layer may be located on the negative electrode current collector, and specifically, may be located on one or both sides of the negative electrode current collector. The above negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers.

[0173] When the negative electrode active material layer is a multilayer structure composed of two or more layers, the types and / or contents of the negative electrode active material, negative electrode binder, and / or negative electrode conductive material in each layer may differ from one another. 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.

[0174] Meanwhile, as the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. 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 alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used.

[0175] Meanwhile, both low-crystallinity carbon and high-crystallinity carbon can be used as the aforementioned carbonaceous materials. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, 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.

[0176] Preferably, the cathode active material may be a carbon-based cathode active material, wherein the carbon-based cathode 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 cathode active material may include natural graphite and artificial graphite.

[0177] The above carbon-based negative electrode active material has an average particle size D 50 This can be 0.1㎛ to 30㎛, preferably 0.5㎛ to 30㎛.

[0178] The above-mentioned negative electrode active material may be included in an amount of 80% to 98% by weight, preferably 90% to 98% by weight, and more preferably 93% to 98% by weight, 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.

[0180] Meanwhile, the above-mentioned cathode active material layer may further include a cathode conductive material and / or a cathode binder together with the cathode active material.

[0181] The cathode conductive material is used to impart conductivity to the cathode, and in the battery being constructed, it can be used without special restrictions as long as it has electronic conductivity without causing chemical changes. Specific examples include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, 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 one of these alone or a mixture of two or more of them may be used.

[0182] The above-mentioned cathode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the cathode active material layer.

[0183] The above-mentioned cathode binder serves to improve adhesion between cathode active material particles and adhesion between the cathode active material and the cathode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, 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 alone or a mixture of two or more may be used.

[0184] The above-mentioned cathode binder may be included in an amount of 0.1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the cathode active material layer.

[0186] The above cathode may be manufactured by methods known in the art. For example, the cathode may be manufactured by mixing a cathode active material, a cathode binder, and / or a cathode conductive material in a solvent to prepare a cathode slurry, applying the cathode slurry onto a cathode current collector, and then drying and rolling, or by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0187] Meanwhile, solvents commonly used in the relevant technical field may be used as the solvent for the cathode slurry, for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or mixtures thereof, but are not limited thereto. The solvent may be used in an amount that dissolves or disperses the cathode active material, cathode conductive material, and cathode binder, and has a viscosity such that the cathode slurry can be uniformly coated.

[0189] (2) Electrolyte

[0190] The electrolyte according to the present invention may include a lithium salt and an organic solvent.

[0191] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, more preferably 0.1 to 3.0 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 allow lithium ions to move effectively.

[0193] 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.

[0194] The above-mentioned 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.

[0195] In addition, the above-mentioned linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and as a representative example, 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 may be used, and specifically, it may include ethylmethyl carbonate (EMC).

[0196] Specific examples of the above linear ester-based organic solvent may 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.

[0197] The above-mentioned cyclic ester-based organic solvent may include at least one organic solvent selected from the group consisting of butyrolactone, valerolactone, and caprolactone.

[0198] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0200] Meanwhile, in addition to the electrolyte components, the above electrolyte may additionally include other additives for the purpose of improving the lifespan characteristics of the battery, suppressing the reduction of battery capacity, and improving the discharge capacity of the battery.

[0201] These other additives may include at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt contained in the electrolyte, as representative examples.

[0202] Specifically, the above other additives are vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sulfone (PS), 1,4-butane sulfone, ethene sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, 1-methyl-1,3-propene sulfone, ethylene sulfate (ESA), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), tetraphenyl borate, lithium oxalyl difluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, Examples include 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 bis-oxalate toborate (LiB(C2O4)2)) and LiBF4.

[0203] The above other additives may be included in an amount of 0.01 to 20 weight% based on the total weight of the electrolyte, and preferably in an amount of 0.05 to 5.0 weight%. If the content of the above other additives is less than 0.01 weight%, the effect of improving low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is negligible, and if the content of the above other additives exceeds 20 weight%, there is a possibility that excessive side reactions may occur within the electrolyte during charging and discharging of the battery. In particular, when the above SEI film-forming additives are added in excess, they may not decompose sufficiently at high temperatures and may remain as unreacted substances or precipitated within the electrolyte at room temperature. Accordingly, side reactions that degrade the lifespan or resistance characteristics of the secondary battery may occur.

[0205] (3) Separator

[0206] The above separator physically separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions; any separator typically used in lithium secondary batteries can be used without any special restrictions. In this case, the separator may be interposed between the positive electrode and the negative electrode.

[0207] Specifically, a porous polymer film made of a polyolefin-based 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, 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 may optionally be used in a single-layer or multi-layer structure.

[0209] Meanwhile, the above lithium secondary battery may have a nominal voltage of 3.20V or higher, preferably 3.38V to 3.80V, more preferably 3.40V to 3.75V, and even more preferably 3.45V to 3.70V. The above nominal voltage refers to the average voltage value during discharge of the lithium secondary battery.

[0210] Since the energy density (Wh / L) of a lithium secondary battery can be calculated as the product of press density (g / cc), discharge capacity (mAh / g), and nominal voltage (V), the energy density may increase as the nominal voltage increases. However, according to the present invention, even if the nominal voltage is high, if the press density and discharge capacity are low, the final energy density of the lithium secondary battery may decrease. Therefore, if the above range is satisfied, the energy density of the lithium secondary battery can be improved.

[0212] 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 achieve excellent output characteristics even under low temperature conditions, it can be particularly usefully applied in the field of electric vehicles.

[0213] According to another embodiment of the present invention, a battery module comprising a lithium secondary battery according to the present invention as a unit cell and a battery pack comprising the same are provided.

[0214] The above battery module or battery pack can 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.

[0216] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are intended only to enable a person skilled in the art to fully understand and easily implement the present invention, and the scope of the rights of the present invention is not limited to the following embodiments.

[0218] Example 1

[0219] (1) Preparation of the first positive active material

[0220] LiFePO4 was prepared by mixing Li2CO3, FeC2O4, and (NH4)2HPO4 in an aqueous solution at a molar ratio of 0.5:1:1 and then calcining at a temperature of 790°C.

[0221] After that, the obtained phosphorus was washed and dried, mixed with glucose, and then heat-treated to produce a phosphorus with a carbon coating layer formed.

[0222] Afterwards, the phosphorus oxide with the formed carbon coating layer was crushed and classified to produce the first positive active material.

[0224] (2) Preparation of the second positive active material

[0225] Li2CO3, MnCO3, FeC2O4, and (NH4)2HPO4 were mixed in an aqueous solution at a molar ratio of 0.5:0.6:0.4:1, and then calcined at a temperature of 650°C to obtain LiMn 0.6 Fe 0.4 PO4 was manufactured.

[0226] After that, the obtained phosphorus was washed and dried, mixed with glucose, and then heat-treated to produce a phosphorus with a carbon coating layer formed.

[0227] Afterwards, the phosphorus oxide with the formed carbon coating layer was crushed and classified to produce a second positive active material.

[0229] (3) Preparation of cathode material powder

[0230] The first cathode active material and the second cathode active material prepared above were mixed in a weight ratio of 80:20 to prepare a cathode material powder.

[0232] Example 2

[0233] A cathode material powder was prepared in the same manner as in Example 1, except that the first cathode active material and the second cathode active material prepared in Example 1 were mixed in a weight ratio of 70:30.

[0235] Comparative Example 1

[0236] A cathode material powder was prepared in the same manner as in Example 1, except that the first cathode active material and the second cathode active material prepared in Example 1 were mixed in a weight ratio of 50:50.

[0238] Comparative Example 2

[0239] LiFePO4 was prepared by mixing Li2CO3, FeC2O4, and (NH4)2HPO4 in an aqueous solution at a molar ratio of 0.5:1:1 and then calcining at a temperature of 790°C.

[0240] After that, the obtained phosphorus was washed and dried, mixed with glucose, and then heat-treated to produce a phosphorus with a carbon coating layer formed.

[0241] Subsequently, the phosphate with a carbon coating layer formed thereon, i.e., the positive active material, was crushed and classified to produce positive material powder.

[0243] Comparative Example 3

[0244] Li2CO3, MnCO3, FeC2O4, and (NH4)2HPO4 were mixed in an aqueous solution at a molar ratio of 0.5:0.3:0.7:1, and then calcined at a temperature of 650°C to obtain a composition of LiMn 0.3 Fe 0.7 A phosphoric acid of PO4 was prepared.

[0245] After that, the obtained phosphorus was washed and dried, mixed with glucose, and then heat-treated to produce a phosphorus with a carbon coating layer formed.

[0246] Subsequently, the phosphate with a carbon coating layer formed thereon, i.e., the positive active material, was crushed and classified to produce positive material powder.

[0248] Comparative Example 4

[0249] The second positive active material of Comparative Example 4 was prepared in the same way as the second positive active material prepared in Example 1, except that it was calcined under a temperature condition of 750℃.

[0250] After that, the first positive active material prepared in Example 1 and the second positive active material of Comparative Example 4 were mixed in a weight ratio of 80:20 to prepare a positive material powder.

[0252] Average particle size D of the manufactured cathode material powder 50 After measuring, the aforementioned cathode material powder was summarized and shown in Table 1 below.

[0254] Cathode material powder First positive active material Second positive active material Molar ratio of Fe to Mn in cathode material powder (Fe / Mn) First phosphate composition Average particle size D 50 (㎛) weight ratio Secondary phosphate composition Average particle size D 50 (㎛) weight ratio Example 1 LiFePO4 0.95 80 LiMn 0.6 Feb 0.4 PO4 0.43 20 7.33 Example 2 LiFePO4 0.95 70 LiMn 0.6 Feb 0.4 PO4 0.43 30 4.56 Comparative Example 1 LiFePO4 0.95 50 LiMn 0.6 Feb 0.4 PO4 0.43 50 2.33 Comparative Example 2 LiFePO4 0.95 100 - - Comparative Example 3 - LiMn 0.3 Feb 0.7 PO4 0.47 100 2.33 Comparative Example 4 LiFePO4 0.95 80 LiMn 0.6 Feb 0.4 PO4 1.03 20 7.33

[0255] Experimental Example 1: Energy Density Measurement

[0256] 1) Press density measurement

[0257] After taking 1g of the cathode material powder prepared in Examples 1-2 and Comparative Examples 1-4, it was placed in a cylindrical metal mold with a diameter of 1.3cm and pressed with a load of 3 ton. Then, the height of the pressed mold was measured with a vernier caliper to measure the press density.

[0258] The measurement results are shown in Table 2 below.

[0260] 2) Measurement of discharge capacity and nominal voltage

[0261] 2-1) Manufacture of Lithium Secondary Battery Half Cells

[0262] A positive electrode slurry was prepared by mixing the respective positive electrode powders prepared in Examples 1 and 2 and Comparative Examples 1 to 4, a positive electrode conductive material (Super P), and a positive electrode binder (PVdF) in N-methylpyrrolidone in a weight ratio of 95:2:3. The positive electrode slurry was applied onto an aluminum current collector, dried, and rolled to produce a positive electrode.

[0263] The cathode used lithium metal.

[0264] An electrode assembly was manufactured by interposing a porous polyethylene separator between the anode and cathode manufactured as described above, and after placing the electrode assembly inside a case, an electrolyte was injected into the case to manufacture a lithium secondary battery. At this time, the electrolyte was prepared by dissolving 1.2 M concentration lithium hexafluorophosphate (LiPF6) in an organic solvent mixed with ethylene carbonate and dimethyl carbonate in a weight ratio of 3:7.

[0266] 2-1) Measurement of Discharge Capacity

[0267] After activating the lithium secondary batteries manufactured above, they were charged at 25°C with a constant current of 0.1C until the voltage reached 4.2V, and then discharged with a constant current of 0.1C until the voltage reached 2.5V to measure the 0.1C discharge capacity.

[0268] The measurement results are shown in Table 2 below.

[0270] 2-2) Nominal Voltage Measurement

[0271] After activating the lithium secondary batteries manufactured above, they were charged at 25°C with a constant current of 0.1C until the voltage reached 4.2V, and then discharged with a constant current of 0.1C until the voltage reached 2.5V.

[0272] The average voltage (nominal voltage) at this time was measured and is shown in Table 2 below.

[0274] 3) Energy Density Measurement

[0275] The energy density (Wh / L) was calculated by multiplying the press density (g / cc) measured in 1) above, the discharge capacity (mAh / g) and the nominal voltage (V) measured in 2) above.

[0276] The measurement results are shown in Table 2 below.

[0278] Press density (g / cc) Discharge capacity (mAh / g) Nominal voltage (V) Energy density (Wh / L) Example 1 2.54 156 3.45 1367 Example 2 2.56 153 3.49 1367 Comparative Example 1 2.49 149 3.54 1312 Comparative Example 2 2.46 158 3.37 1310 Comparative Example 3 2.15 157 3.58 1208 Comparative Example 4 2.47 154 3.45 1312

[0279] Through Table 2 above, the composition, weight ratio, and average particle size D of the second positive active material of the first and second positive active materials according to the present invention 50 It can be seen that the energy density of the cathode material powder of Examples 1 to 2, which satisfy the range, is superior to that of the cathode material powder of Comparative Examples 1 to 4, which do not.

Claims

Claim 1 A cathode material powder comprising: a first cathode active material comprising a first phosphate; and a second cathode active material comprising a second phosphate; wherein the first phosphate is represented by the following chemical formula 1 and the second phosphate is represented by the following chemical formula 2, the first cathode active material is contained in greater quantities than the second cathode active material, and the average particle size D of the first cathode active material 50 The average particle size D of the second positive active material is 50 Larger than, and the second positive active material has an average particle size D 50 Cathode material powder with a particle size of 1.0㎛ or less: [Chemical Formula 1]Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4 In the above chemical formula 1, M 1 ... comprises one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, -0.1≤x1≤0.1, 0.9≤a1≤1.0, 0.0≤b1≤0.1, and [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 contains one or more elements 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≤0.5, 0.0≤b2≤0.

1. Claim 2 A cathode material powder according to claim 1, wherein the first phosphate is LiFePO4. Claim 3 In claim 1, the cathode material powder, wherein the second phosphate is 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 one or more elements 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, 0.35≤a2≤0.45, 0.0≤b2≤0.

1. Claim 4 In claim 1, the first positive active material has an average particle size D 50 Anode material powder having a thickness of 0.5㎛ to 10㎛. Claim 5 In claim 1, the second positive active material has an average particle size D 50 Anode material powder having a thickness of 0.3㎛ to 0.8㎛. Claim 6 A cathode material powder according to claim 1, wherein the first and second cathode active materials each independently comprise a coating layer containing carbon disposed on the first and second phosphates. Claim 7 A cathode material powder according to claim 5, wherein the carbon content included in the coating layer containing carbon disposed on the first phosphate is 0.1% to 5.0% by weight based on the total weight of the first cathode active material. Claim 8 A cathode material powder according to claim 5, wherein the carbon content included in the coating layer containing carbon disposed on the second phosphate is 0.5% to 5.0% by weight based on the total weight of the second cathode active material. Claim 9 A cathode material powder according to claim 1, wherein the weight ratio of the first cathode active material and the second cathode active material is 60:40 to 90:

10. Claim 10 delete Claim 11 A cathode material powder according to claim 1, wherein the molar ratio of Fe to Mn (Fe / Mn) in the cathode material powder is 2.5 to 50. Claim 12 The cathode material powder of claim 1, wherein the pressed density measured after pressing with a pressure of 3 ton is 2.50 g / cc or more. Claim 13 An anode comprising the anode material powder of claim 1. Claim 14 A lithium secondary battery comprising: a positive electrode of claim 13; a negative electrode disposed opposite to the positive electrode; and an electrolyte.

Images