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

Abstract

The present invention relates to a cathode material powder comprising: a first cathode active material including a first phosphorous oxide; and a second cathode active material including a second phosphorous oxide, wherein the first phosphorous oxide is represented by a specific chemical formula 1, the second phosphorous oxide is represented by a specific chemical formula 2, the amount of the first cathode active material is greater than that of the second cathode active material, and the second cathode active material has an average particle diameter D50 of 1.0 µm or less.

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. 10-2024-0116233, dated August 28, 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 thermal stability.

[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, relatively heavy compared to other compounds, low energy density, and difficulty in achieving excellent press density.

[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, long-life characteristics, and safety, while also achieving excellent energy density and press density.

[0012]

[0013] One object of the present invention is to solve the above problems, and to include a first cathode active material having a low manganese (Mn) content and a second cathode active material having a high manganese (Mn) content in cathode powder, while including the first cathode active material in an amount greater than that of the second cathode active material, and having an average particle diameter D of the second cathode active material. 50 The purpose is to provide a cathode powder having excellent energy density by controlling the press density to 1.0㎛ or less and having high discharge capacity and nominal voltage.

[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] [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, the second phosphate is represented by the following chemical formula 2, and the first cathode active material is contained in a larger amount than the second cathode active material, and the second cathode active material has an average particle diameter D 50 This provides a cathode material powder having a size of 1.0㎛ or less.

[0018] [Chemical Formula 1]

[0019] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0020] In the above chemical formula 1,

[0021] 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,

[0022] -0.1≤x1≤0.1, 0.9≤a1≤1.0, 0.0≤b1≤0.1,

[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,

[0026] M 2 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,

[0027] -0.1≤x2≤0.1, 0.2≤a2≤0.5, 0.0≤b2≤0.1.

[0028] [2] In the present invention, in the above [1], the first phosphorus oxide may be LiFePO4.

[0029] [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.

[0030] [Chemical Formula 2-1]

[0031] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0032] In the above chemical formula 2,

[0033] M 2 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,

[0034] -0.1≤x2≤0.1, 0.35≤a2≤0.45, 0.0≤b2≤0.1.

[0035] [4] The present invention, in at least one of the above [1] to [3], the first positive electrode active material has an average particle diameter D 50 This can be 0.5㎛ to 10㎛.

[0036] [5] The present invention, in at least one of the above [1] to [4], the second positive electrode active material has an average particle diameter D 50 This can be 0.3㎛ to 0.8㎛.

[0037] [6] In at least one of the above [1] to [5], the first and second positive electrode active materials may further include a coating layer including carbon independently disposed on the first and second phosphates, respectively.

[0038] [7] In the present invention, in the above [1] to [6], the content of carbon included in the coating layer including carbon disposed on the first phosphate may be 0.1 wt% to 5.0 wt% based on the total weight of the first positive electrode active material.

[0039] [8] In the present invention, in the above [1] to [7], the content of carbon included in the coating layer including carbon disposed on the second phosphate may be 0.5 wt% to 5.0 wt% based on the total weight of the second positive electrode active material.

[0040] [9] In at least one of the above [1] to [8], the weight ratio of the first positive electrode active material and the second positive electrode active material may be 60:40 to 90:10.

[0041]

[0010] The present invention relates to at least one of the above [1] to [9], wherein the average particle diameter D of the first positive electrode active material 50 The average particle diameter D of the second positive electrode active material is 50 It can be bigger.

[0042]

[0011] In at least one of the above [1] to

[0010] , the molar ratio of Fe to Mn (Fe / Mn) in the cathode material powder may be 2.5 to 50.

[0043]

[0012] In at least one of the above [1] to

[0011] , the cathode material powder may have a press density of 2.50 g / cc or more measured after pressing at a pressure of 3 tons.

[0044]

[0013] The present invention provides a positive electrode comprising a positive electrode powder according to at least one of the above [1] to

[0012] .

[0045]

[0014] The present invention provides a lithium secondary battery comprising: a positive electrode according to the above

[0013] ; a negative electrode disposed opposite the positive electrode; and an electrolyte.

[0046]

[0047] The cathode material powder according to the present invention comprises a first cathode active material including a phosphorus oxide represented by chemical formula 1 and a second cathode active material including a phosphorus oxide represented by chemical formula 2, and comprises the first and second cathode active materials in a specific weight ratio, wherein the average particle diameter of the second cathode active material is D 50 It is characterized by being 1.0㎛ or less. The phosphorus oxide represented by Chemical Formula 1 has high electronic conductivity, lithium ion conductivity and discharge capacity, and the phosphorus oxide represented by Chemical Formula 2 has high operating voltage. At this time, the first positive electrode active material including the phosphorus oxide represented by Chemical Formula 1 is included in greater quantity than the second positive electrode active material to increase the press density, discharge capacity and nominal voltage, while the average particle diameter D of the second positive electrode active material 50 By controlling the press density, the press density can be further increased. Therefore, when the cathode material powder according to the present invention is applied, the energy density of a lithium secondary battery can be improved.

[0048]

[0049] Hereinafter, the present invention will be described in more detail.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] In the present invention, "single-particle type" refers to a particle formed by an aggregation of 50 or fewer sub-particles. The sub-particle unit constituting a single-particle type particle is referred to as a nodule. Single-particle type particles include single particles composed of one nodule and pseudo-single particles that are composites of 2 to 50 nodules.

[0054] The above “nodule” is a sub-particle unit that constitutes a single particle and a pseudo-single particle, and may be a single crystal without a crystalline grain boundary, or a polycrystal with no apparent grain boundary when observed under a magnification of 2000 to 20000 times using a scanning electron microscope.

[0055] In the present invention, a "secondary particle" refers to a particle formed by an aggregation of more than 50 sub-particles. To distinguish it from the sub-particles that constitute a single particle, the sub-particles that constitute a secondary particle are referred to as "primary particles."

[0056] In the present invention, “particle” is a concept including any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0057] 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.

[0058] 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.

[0059]

[0060] The inventors of the present invention have conducted research to improve the energy density of a lithium secondary battery, and as a result, they have found that the first cathode active material including a phosphate having a high iron (Fe) content is included in a larger amount than the second cathode active material including a phosphate having a relatively high manganese (Mn) content, while the average particle diameter of the second cathode active material is D 50 The present invention was completed by finding that the energy density (Wh / L) of a lithium secondary battery can be improved when a cathode powder controlled to 1.0㎛ or less is applied.

[0061]

[0062] Hereinafter, the present invention will be described in detail.

[0063] 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.

[0064]

[0065] cathode powder

[0066] Hereinafter, the cathode material powder according to the present invention will be described.

[0067] The cathode material powder according to the present invention comprises a first cathode active material including a first phosphate; and a second cathode active material including a second phosphate; wherein the first phosphate is represented by the following chemical formula 1, the second phosphate is represented by the following chemical formula 2, and the first cathode active material is contained in a larger amount than the second cathode active material, and the second cathode active material has an average particle diameter D 50 This is less than 1.0㎛.

[0068] [Chemical Formula 1]

[0069] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0070] In the above chemical formula 1,

[0071] 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,

[0072] -0.1≤x1≤0.1, 0.9≤a1≤1.0, 0.0≤b1≤0.1,

[0073] [Chemical Formula 2]

[0074] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0075] In the above chemical formula 2,

[0076] M 2 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,

[0077] -0.1≤x2≤0.1, 0.2≤a2≤0.5, 0.0≤b2≤0.1.

[0078]

[0079] 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.

[0080] 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.

[0081] In contrast, lithium manganese phosphate compounds have a high operating voltage and therefore a high energy density, but their charging output characteristics are poor, making it difficult to implement high-density electrodes due to limitations in increasing the average particle size of the compound.

[0082] To solve this problem, lithium manganese iron phosphate compounds (e.g., LiMn) with controlled molar ratio of iron and manganese in lithium phosphate were prepared. 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.

[0083] Therefore, in order to solve the above-mentioned problem, the present invention includes a first positive electrode active material including a phosphate having a high iron content (low manganese content) and a second positive electrode active material including a phosphate having a relatively high manganese content (low iron content), wherein the first positive electrode active material is included in a larger amount than the second positive electrode active material, and the second positive electrode active material has an average particle diameter D 50 We aim to apply this positive electrode powder of 1.0㎛ or less to lithium secondary batteries.

[0084] At this time, in the case of the first positive electrode active material having a high iron content (low manganese content), the charge output is excellent and the discharge capacity (mAh / g) is superior even if the average particle size is increased, and in the case of the second positive electrode active material having a high manganese content (low iron content), the operating voltage is excellent even if the average particle size is small. That is, when the first positive electrode active material having the above characteristics is included in the positive electrode powder in a larger amount than the second positive electrode active material, the energy density (Wh / L), which is the product of the press density (g / cc), the discharge capacity (mAh / g), and the nominal voltage (V), is maximized, so that a positive electrode powder capable of implementing an excellent energy density can be manufactured.

[0085] Conversely, when the second positive electrode active material is included in the positive electrode powder in an amount equal to the weight of the first positive electrode active material, or when the second positive electrode active material is included in a greater amount than the first positive electrode active material, the second positive electrode active material is excessive, so the nominal voltage is somewhat high, but the second positive electrode active material cannot be properly mixed with the first positive electrode active material, so the press density is low, the discharge capacity is small, and ultimately, there is a problem of a decrease in the energy density.

[0086] In addition, when the first positive electrode active material is included alone in the positive electrode powder, the discharge capacity is somewhat high, but since the second positive electrode active material is not included, the press density and nominal voltage are low, which ultimately leads to a problem of reduced energy density. Conversely, when the second positive electrode active material is included alone in the positive electrode powder, the nominal voltage is somewhat high, but since the first positive electrode active material is not included, the press density and discharge capacity are low, which ultimately leads to a problem of reduced energy density.

[0087] Meanwhile, while including the first positive electrode active material in the positive electrode powder in greater amounts than the second positive electrode active material, the average particle diameter D of the second positive electrode active material 50 If it exceeds 1.0㎛, it is difficult to improve the energy density. Specifically, the average particle diameter D of the second positive electrode active material 50 If this exceeds 1.0㎛, the relatively large void space between particles in the positive electrode powder may become larger, which may lower the press density of the positive electrode powder, and the excessively large particle size may limit rearrangement between particles in the positive electrode powder, which may make it difficult to form a sufficiently dense structure during electrode rolling, resulting in a problem of lowering the energy density of the battery.

[0088] Therefore, a first cathode active material comprising a phosphate having a high iron content (low manganese content) and a second cathode active material comprising a phosphate having a relatively high manganese content (low iron content), wherein the first cathode active material is included in greater quantity than the second cathode active material, and the second cathode active material has an average particle diameter D 50 By controlling it to 1.0㎛ or less, it is possible to achieve excellent press density while also achieving excellent energy density.

[0089]

[0090] Hereinafter, the cathode material powder according to the present invention will be described in more detail.

[0091]

[0092] (1) First positive electrode active material

[0093] In the cathode material powder according to the present invention, the cathode material powder includes a first cathode active material including a first phosphate, and the first phosphate is represented by the following chemical formula 1.

[0094] [Chemical Formula 1]

[0095] Li 1+x1 [Mn 1-a1-b1 Fe a1 M 1 b1 ]PO4

[0096] 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.

[0097] 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.

[0098] The above a1 is the molar 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 more, 0.92 or more, 0.95 or more, 0.97 or more, or 0.99 or more, and may be 1.0 or less, and more preferably, the above a1 may be 1.0.

[0099] When the above a1 is less than 0.9, the electronic conductivity and lithium ion conductivity within the phosphate are low, which can lead to poor output characteristics, and there is a problem in that there is a limit to increasing the average particle size. Therefore, when the above range is satisfied, it is desirable in that it is possible to implement a high-density electrode by appropriately increasing the average particle size while maintaining excellent output characteristics.

[0100] The above b1 is M among all metals except lithium in the first phosphate. 1 The molar fraction may be from 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.

[0101] Preferably, the first phosphate may be LiFePO4.

[0102]

[0103] According to one embodiment of the present invention, the first positive electrode active material has an average particle diameter D 50 This may 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 material powder, thereby realizing a high-density electrode, while also making it easy to increase the slurry solid content during electrode production, thereby realizing excellent energy density and processability, and is preferable in that it can realize excellent discharge capacity.

[0104]

[0105] According to one embodiment of the present invention, the first positive electrode active material has a BET specific surface area of ​​1 m 2 / g to 30m 2 / g can be, preferably 3m 2 / g to 20m 2 / g can be, more preferably 5m 2 / g to 15m 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.

[0106]

[0107] According to one embodiment of the present invention, the first positive electrode active material may be in the form of a single particle. Preferably, the first positive electrode active material may be in the form of a single particle containing 1 to 50 nodules, more preferably in the form of a single particle containing 1 to 40 nodules, even more preferably in the form of a single particle containing 1 to 30 nodules, even more preferably in the form of a single particle containing 1 to 25 nodules, and even more preferably in the form of a single particle containing 1 to 15 nodules. When the above conditions are satisfied, the contact area with the electrolyte may be small, thereby reducing side reactions with the electrolyte, the number of pores in the particles may be small, thereby realizing excellent energy density, and the particle structure may be stable, thereby improving durability.

[0108]

[0109] 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 material powder may be improved.

[0110]

[0111] According to one embodiment of the present invention, the content of carbon included in the coating layer including carbon disposed on the first phosphate 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 first positive electrode active material. When the above range is satisfied, it may be preferable in that the electronic conductivity of the first positive electrode active material may be improved without acting as a resistor.

[0112]

[0113] (2) Second positive electrode active material

[0114] In the cathode material powder according to the present invention, the cathode material powder includes a second cathode active material including a second phosphate, and the second phosphate is represented by the following chemical formula 2.

[0115] [Chemical Formula 2]

[0116] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4

[0117] 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.

[0118] 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.

[0119] The above a2 is the molar 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.

[0120] When the above a2 is less than 0.2, there are problems such as low electronic conductivity and lithium ion conductivity within the phosphate, which may result in poor output characteristics, low discharge capacity, and limitations in increasing the average particle size. When the above a2 exceeds 0.5, the operating voltage may be low, which may reduce the energy density. Therefore, when the above range is satisfied, it may be desirable in that it is possible to implement a high-density electrode by appropriately increasing the average particle size while maintaining excellent output characteristics.

[0121] The above b2 is M among all metals except lithium in the first phosphate. 2 The molar fraction may be from 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.

[0122] Preferably, the second phosphate may be represented by the following chemical formula 2-1.

[0123] [Chemical Formula 2-1]

[0124] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2]PO4

[0125] In the above chemical formula 2,

[0126] 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.

[0127]

[0128] According to one embodiment of the present invention, the second positive electrode active material has an average particle diameter 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, it may be 0.3㎛ to 0.8㎛. When the above range is satisfied, the second positive electrode active material can be appropriately distributed within the positive electrode material powder, so that a high-density electrode can be implemented, and at the same time, it is easy to increase the slurry solid content during electrode production, so that excellent energy density and processability can be implemented, and it is preferable in that excellent discharge capacity can be implemented.

[0129]

[0130] According to one embodiment of the present invention, the second positive electrode active material has a BET specific surface area of ​​1 m 2 / g to 30m 2 / g can be, preferably 2m 2 / g to 25m 2 / g can be, more preferably 5m 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.

[0131]

[0132] According to one embodiment of the present invention, the second positive electrode active material may be in the form of single particles. Preferably, the second positive electrode active material may be in the form of single particles containing 1 to 50 nodules, more preferably in the form of single particles containing 1 to 40 nodules, even more preferably in the form of single particles containing 1 to 30 nodules, even more preferably in the form of single particles containing 1 to 25 nodules, and even more preferably in the form of single particles containing 1 to 15 nodules. When the above conditions are satisfied, the contact area with the electrolyte may be small, thereby reducing side reactions with the electrolyte, the number of pores in the particles may be small, thereby realizing excellent energy density, and the particle structure may be stable, thereby improving durability.

[0133]

[0134] 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 material powder may be improved.

[0135]

[0136] According to one embodiment of the present invention, the content of carbon included in the coating layer including carbon disposed on the second phosphate may be 0.5 wt% to 5.0 wt%, preferably 0.8 wt% to 4.0 wt%, and more preferably 1.0 wt% to 3.0 wt%, based on the total weight of the first positive electrode active material. When the above range is satisfied, it may be preferable in that the electronic conductivity of the first positive electrode active material may be improved without acting as a resistor.

[0137]

[0138] According to one embodiment of the present invention, the first and second positive electrode active materials may further include a coating layer including carbon independently disposed on the first and second phosphates, respectively.

[0139]

[0140] The cathode material powder according to the present invention contains the first cathode active material in greater quantity 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 press density is high, and the discharge capacity and nominal voltage are high, thereby providing excellent energy density.

[0141]

[0142] According to one embodiment of the present invention, the average particle diameter D of the first positive electrode active material 50 The average particle diameter D of the second positive electrode active material is 50 It can be larger. When the above conditions are satisfied, unlike the second positive electrode active material whose electronic conductivity and lithium ion conductivity are reduced when the average particle size is large, the electronic conductivity and lithium ion conductivity of the first positive electrode active material are not reduced, and the second positive electrode active material with a small average particle size can appropriately fill the gaps between the first positive electrode active material with a large average particle size, so that the press density is excellent and excellent energy density characteristics can be realized.

[0143]

[0144] According to one embodiment of the present invention, the molar ratio of Fe to Mn (Fe / Mn) in the cathode 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 powder may be different from the composition of the phosphate present in each of the first cathode active material and / or the second cathode active material. When the above range is satisfied, excellent energy density can be realized.

[0145]

[0146] According to one embodiment of the present invention, the positive electrode powder may have a press density measured after pressing at a pressure of 3 tons of 2.50 g / cc or more, 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 press density may be measured by collecting 1 g of the positive electrode 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, thereby realizing excellent energy density.

[0147]

[0148] anode

[0149] Hereinafter, the anode according to the present invention will be described.

[0150] 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.

[0151]

[0152] Hereinafter, each component of the anode according to the present invention will be described in detail.

[0153]

[0154] (1) Positive current collector

[0155] 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.

[0156]

[0157] (2) Positive electrode active material layer

[0158] 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.

[0159] 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.

[0160] 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.

[0161] The above-described positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and has electronic conductivity 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 of these may be used alone or a mixture of two or more 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.

[0162] 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.

[0163]

[0164] 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.

[0165]

[0166] lithium secondary battery

[0167] Hereinafter, a lithium secondary battery according to the present invention will be described.

[0168] 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 include a separator interposed between the positive electrode and the negative electrode.

[0169] Since the above anode is the same as described above, the remaining components excluding the anode will be described below.

[0170]

[0171] (1) Cathode

[0172] 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.

[0173]

[0174] 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.

[0175]

[0176] 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.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] 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.

[0181] 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㎛.

[0182] 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.

[0183]

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189]

[0190] 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.

[0191] 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.

[0192]

[0193] (2) Electrolyte

[0194] The electrolyte according to the present invention may include a lithium salt and an organic solvent.

[0195] 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.

[0196]

[0197] 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.

[0198] 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.

[0199] 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).

[0200] 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.

[0201] The above cyclic ester organic solvent may include at least one organic solvent selected from the group consisting of butyrolactone, valerolactone, and caprolactone.

[0202] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0203]

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208]

[0209] (3) Membrane

[0210] 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.

[0211] 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.

[0212]

[0213] Meanwhile, the lithium secondary battery may have a nominal voltage of 3.20 V or higher, preferably 3.38 V to 3.80 V, more preferably 3.40 V to 3.75 V, and even more preferably 3.45 V to 3.70 V. The nominal voltage refers to an average voltage value during discharge of the lithium secondary battery.

[0214] The energy density (Wh / L) of a lithium secondary battery can be calculated as the product of the press density (g / cc), the discharge capacity (mAh / g), and the nominal voltage (V), so that the energy density can 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 small, the energy density of the final lithium secondary battery can decrease. Therefore, when the above range is satisfied, the energy density of the lithium secondary battery can be improved.

[0215]

[0216] 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.

[0217] 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.

[0218] 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.

[0219]

[0220] 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.

[0221]

[0222] Example 1

[0223] (1) Preparation of the first positive electrode active material

[0224] 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 a temperature of 790°C.

[0225] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and then heat-treated to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0226] Afterwards, the phosphorus oxide having a carbon coating layer formed thereon was pulverized and classified to manufacture a first positive electrode active material.

[0227]

[0228] (2) Manufacturing of the second positive electrode active material

[0229] Li2CO3, MnCO3, FeC2O4, (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℃ to obtain LiMn 0.6 Fe0.4 PO4 was manufactured.

[0230] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and then heat-treated to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0231] Afterwards, the phosphorus oxide having a carbon coating layer formed thereon was pulverized and classified to manufacture a second positive electrode active material.

[0232]

[0233] (3) Manufacturing of cathode material powder

[0234] The first positive electrode active material and the second positive electrode active material manufactured above were mixed in a weight ratio of 80:20 to manufacture positive electrode material powder.

[0235]

[0236] Example 2

[0237] A cathode material powder was manufactured in the same manner as in Example 1, except that the first cathode active material and the second cathode active material manufactured in Example 1 were mixed in a weight ratio of 70:30.

[0238]

[0239] Comparative Example 1

[0240] A cathode material powder was manufactured in the same manner as in Example 1, except that the first cathode active material and the second cathode active material manufactured in Example 1 were mixed in a weight ratio of 50:50.

[0241]

[0242] Comparative Example 2

[0243] 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 a temperature of 790°C.

[0244] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and then heat-treated to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0245] Afterwards, the phosphate having a carbon coating layer formed thereon, i.e., the cathode active material, was pulverized and classified to produce cathode material powder.

[0246]

[0247] Comparative Example 3

[0248] Li2CO3, MnCO3, FeC2O4, (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℃ to obtain a composition of LiMn 0.3 Fe 0.7 PO4 phosphorus oxide was prepared.

[0249] Afterwards, the obtained phosphorus oxide was washed and dried, mixed with glucose, and heat-treated to produce a phosphorus oxide having a carbon coating layer formed thereon.

[0250] Afterwards, the phosphate having a carbon coating layer formed thereon, i.e., the cathode active material, was pulverized and classified to produce cathode material powder.

[0251]

[0252] Comparative Example 4

[0253] The second positive electrode active material of Comparative Example 4 was manufactured in the same manner as the second positive electrode active material manufactured in Example 1, except that it was fired at a temperature of 750°C.

[0254] After that, the first positive electrode active material manufactured in Example 1 and the second positive electrode active material of Comparative Example 4 were mixed in a weight ratio of 80:20 to manufacture positive electrode material powder.

[0255]

[0256] Average particle diameter D of the manufactured cathode material powder 50 After measuring, the cathode material powder mentioned above was organized and shown in Table 1 below.

[0257]

[0258] Cathode material powder, first cathode active material, second cathode active material, molar ratio of Fe to Mn in cathode material powder (Fe / Mn), first phosphate composition, average particle size D 50 (㎛) Weight ratio of second phosphate composition average particle size D 50 (㎛)Weight ratioExample 1LiFePO40.9580LiMn 0.6 Fe 0.4 PO40.43207.33Example 2LiFePO40.9570LiMn 0.6 Fe 0.4 PO40.43304.56Comparative Example 1LiFePO40.9550LiMn 0.6 Fe 0.4 PO40.43502.33Comparative Example 2LiFePO40.95100--Comparative Example 3-LiMn 0.3 Fe 0.7 PO40.471002.33Comparative Example 4LiFePO40.9580LiMn 0.6 Fe 0.4 PO41.03207.33

[0259] Experimental Example 1: Energy Density Measurement

[0260] 1) Press density measurement

[0261] After collecting 1 g of the cathode material powder manufactured in Examples 1 to 2 and Comparative Examples 1 to 4, 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.

[0262] The measurement results are shown in Table 2 below.

[0263]

[0264] 2) Measurement of discharge capacity and nominal voltage

[0265] 2-1) Manufacturing of lithium secondary battery half cells

[0266] Each of the cathode material powders manufactured in Examples 1 to 2 and Comparative Examples 1 to 4, 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.

[0267] Lithium metal was used as the cathode.

[0268] 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.

[0269]

[0270] 2-1) Discharge capacity measurement

[0271] 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 discharge capacity was measured.

[0272] The measurement results are shown in Table 2 below.

[0273]

[0274] 2-2) Nominal voltage measurement

[0275] 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.

[0276] The average voltage (nominal voltage) at this time was measured and shown in Table 2 below.

[0277]

[0278] 3) Energy density measurement

[0279] The energy density (Wh / L) was calculated by multiplying the press density (g / cc) measured in 1) above and the discharge capacity (mAh / g) and nominal voltage (V) measured in 2) above.

[0280] The measurement results are shown in Table 2 below.

[0281]

[0282] Press Density (g / cc)Discharge Capacity (mAh / g)Nominal Voltage (V)Energy Density (Wh / L)Example 12.541563.451367Example 22.561533.491367Comparative Example 12.491493.541312Comparative Example 22.461583.371310Comparative Example 32.151573.581208Comparative Example 42.471543.451312

[0283] Through the above Table 2, the composition, weight ratio, and average particle diameter D of the first and second positive electrode active materials according to the present invention 50 It can be seen that the cathode material powders of Examples 1 to 2 that satisfy the range have a superior energy density than the cathode material powders of Comparative Examples 1 to 4 that do not.

Claims

1. A cathode material powder comprising a first cathode active material including a first phosphorus oxide; and a second cathode active material including a second phosphorus oxide; The above first phosphate is represented by the following chemical formula 1, The above second phosphate is represented by the following chemical formula 2: Contains more of the first positive electrode active material than the second positive electrode active material, The above second positive electrode active material has an average particle diameter D 50 This positive electrode powder is less than 1.0㎛: [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, -0.1≤x1≤0.1, 0.9≤a1≤1.0, 0.0≤b1≤0.1, [Chemical Formula 2] Li 1+x2 [Mn 1-a2-b2 Fe a2 M 2 b2 ]PO4 In the above chemical formula 2, M 2 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, -0.1≤x2≤0.1, 0.2≤a2≤0.5, 0.0≤b2≤0.

1.

2. In claim 1, The above first phosphate is LiFePO4, a cathode material powder.

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 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, -0.1≤x2≤0.1, 0.35≤a2≤0.45, 0.0≤b2≤0.

1.

4. In claim 1, The above first positive electrode active material has an average particle diameter D 50 This positive electrode powder is 0.5㎛ to 10㎛.

5. In claim 1, The above second positive electrode active material has an average particle diameter D 50 This positive electrode powder is 0.3㎛ to 0.8㎛.

6. In claim 1, A cathode material powder, wherein the first and second cathode active materials further include a coating layer including carbon independently disposed on the first and second phosphates, respectively.

7. In claim 5, A cathode material powder, wherein the content of carbon included in the coating layer including carbon disposed on the first phosphate is 0.1 wt% to 5.0 wt% based on the total weight of the first cathode active material.

8. In claim 5, A cathode material powder, wherein the content of carbon included in the coating layer including carbon disposed on the second phosphate is 0.5 wt% to 5.0 wt% based on the total weight of the second cathode active material.

9. In claim 1, A cathode material powder, wherein the weight ratio of the first cathode active material and the second cathode active material is 60:40 to 90:

10.

10. In claim 1, Average particle diameter D of the above first positive electrode active material 50 The average particle diameter D of the second positive electrode active material is 50 Larger, positive electrode powder.

11. In claim 1, A cathode material powder having a molar ratio of Fe to Mn (Fe / Mn) of 2.5 to 50.

12. In claim 1, The above cathode material powder is a cathode material powder having a press density of 2.50 g / cc or more measured after pressing at a pressure of 3 tons.

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

14. A lithium secondary battery comprising: a positive electrode of claim 13; a negative electrode disposed opposite the positive electrode; and an electrolyte.