Cathode active material for lithium secondary battery and method for manufacturing same

Abstract

Disclosed are a lithium manganese iron phosphate (LMFP) positive electrode active material for a lithium secondary battery and a method for manufacturing same. The positive electrode active material according to the present invention comprises: an LMFP represented by LiMnaFebPO4 (a + b = 1, a > 0, b > 0); and a carbon layer coated on the surface of the LMFP, and satisfies relational expression 1. [Relational expression 1] 1.65 ≤ (WcХ10) / S0 ≤ 2.0 In relational expression 1, Wc represents the content (wt%) of carbon in the positive electrode active material as measured using an element analyzer, and S0 represents the sum of surface areas (m2 / g) per unit mass of primary particles constituting one secondary particle of LMFP.

Description

Cathode active material for lithium secondary batteries and method for producing the same

[0001] The present invention relates to a lithium manganese iron phosphate (LMFP) cathode active material for a lithium secondary battery and a method for producing the same.

[0002] Lithium iron phosphate (LFP) cathode active material is an olivine structure composed of an octahedral site of FeO6 and a tetrahedral site of PO4, and is a material through which lithium ions are inserted and deintercalated through a one-dimensional pathway.

[0003] LFP cathode active material is a material with a main composition of Li, Fe, and P, and has a price advantage compared to NCA or NCM materials that mainly use Ni and Co, as the cost of metal minerals is lower.

[0004] In addition, the LFP cathode active material has a stable structure due to strong PO bonds, so it has the advantage of excellent thermal stability as there is no oxygen dissociation at high temperatures during charging.

[0005] In addition, LFP cathode active material has excellent life characteristics, and many electric vehicles using it have been produced in China.

[0006] However, LFP cathode active materials suffer from low energy density. To improve this, research is currently underway on lithium manganese iron phosphate (LMFP) cathode active materials, which substitute manganese (Mn) for the iron (Fe) in LFP cathode active materials.

[0007] LMFP cathode active material has the advantage of increasing energy density by about 15% while increasing operating voltage because it is richer in manganese compared to LFP cathode active material.

[0008] However, LMFP cathode active materials have the disadvantage of lower lithium ion diffusion rate and electrical conductivity compared to LFP cathode active materials. Research is being conducted to form a carbon layer on LMFP cathode active materials to increase their electrical conductivity. However, there is a problem that the carbon source affects the crystal growth of LFP during the sintering process, which reduces the initial discharge capacity and rate characteristics of the battery.

[0009] Therefore, a method for improving the initial discharge capacity and rate characteristics of LMFP cathode active materials is needed.

[0010] The purpose of the present invention is to provide a positive electrode active material for a lithium secondary battery having improved initial discharge capacity and rate characteristics, and a method for manufacturing the same.

[0011] In addition, an object of the present invention is to provide a positive electrode active material for a lithium secondary battery having improved electrical conductivity by uniformly coating carbon on the surface of LMFP, and a method for manufacturing the same.

[0012] The objectives of the present invention are not limited to those mentioned above. Other objectives and advantages of the present invention not mentioned above can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the objectives and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0013] The positive electrode active material according to the present invention is LiMn a Fe b It comprises an LMFP represented by PO4(a + b = 1, a > 0, b > 0); and a carbon layer coated on the surface of the LMFP; and is characterized in that it satisfies the following relational expression 1.

[0014] [Relationship 1]

[0015] 1.65 ≤ (W c Х10) / S0≤ 2.0

[0016] In the above relation 1, Wc is the carbon content (wt%) in the positive electrode active material measured using an elemental analyzer, and S0 is the surface area (m) per unit mass of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

[0017] The carbon content of the above carbon layer may be 1.5 to 1.8 wt% with respect to 100 wt% of the total positive electrode active material.

[0018] The above positive electrode active material may be spherical.

[0019] The above carbon may include at least one of glucose, sucrose, fructose, lactose, maltose, graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, a material having a crystal structure including graphene, and a material having a crystal structure including graphite.

[0020] The above positive electrode active material may further include one or more doping elements selected from Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, Y, P, V, and Sr.

[0021] In another embodiment, a cathode active material according to the present invention comprises lithium manganese iron phosphate (LMFP); and a carbon layer coated on the surface of the LMFP; and is characterized by satisfying the following relational expression 1.

[0022] [Relationship 1]

[0023] 1.65 ≤ (W c Х10) / S0≤ 2.0

[0024] In the above relation 1, W c is the carbon content (wt%) in the positive electrode active material measured using an elemental analyzer, and S0 is the surface area (m) per unit mass of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

[0025] The method for manufacturing a positive electrode active material according to the present invention comprises the steps of (a) mixing and grinding an LMFP precursor and a carbon precursor; (b) spray-drying the slurry obtained by the grinding; and (c) firing the powder obtained by the spray-drying to manufacture a positive electrode active material having a carbon layer coated on the surface of the LMFP; wherein the LMFP is LiMn a Fe b It is expressed as PO4(a + b = 1, a > 0, b > 0) and is characterized by satisfying the following relationship 1.

[0026] [Relationship 1]

[0027] 1.65 ≤ (W c Х10) / S0≤ 2.0

[0028] In the above relation 1, W c is the carbon content (wt%) in the positive electrode active material measured using an elemental analyzer, and S0 is the surface area (m) per unit mass of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

[0029] In the step of mixing and milling the above (a) LMFP precursor and carbon precursor, the average particle size (D50) of the slurry milled by mixing and milling the lithium precursor, phosphorus precursor, iron precursor, manganese precursor, and carbon precursor may be 100 to 240 nm.

[0030] In the above step (a), 1.5 to 1.8 wt% of the carbon precursor can be mixed with respect to the total 100 wt% of the LMFP precursor and the carbon precursor.

[0031] In the above LMFP, the sum of iron (Fe) and manganese (Mn): lithium (Li) can be mixed in a molar ratio of 1:1.00 to 1.08.

[0032] In the above step (c), the calcination can be performed in an inert atmosphere and at 630 to 700°C.

[0033] In the above step (a), the carbon precursor may include at least one of glucose, sucrose, fructose, lactose, maltose, graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, a material having a crystal structure including graphene, and a material having a crystal structure including graphite.

[0034] In the above step (a), one or more dispersants selected from the group consisting of citric acid, fumaric acid, adipic acid, succinic acid, tartaric acid, glutarinc acid, maleic acid, oxalic acid, malonic acid, and ascorbic acid may be further mixed.

[0035] In the above step (a), one or more doping elements of Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, Y, P, V, and Sr may be further mixed.

[0036] When further mixing Ti as the above doping element, in LMFP, the sum of iron (Fe) and manganese (Mn): titanium (Ti) can be mixed in a molar ratio of 1:0.003 to 0.007.

[0037] In another embodiment, a method for manufacturing a positive electrode active material according to the present invention includes the steps of (a) mixing and pulverizing a lithium manganese iron phosphate (LMFP) precursor and a carbon precursor; (b) spray-drying a slurry obtained by the pulverization; and (c) calcining a powder obtained by the spray-drying to manufacture a positive electrode active material having a carbon layer coated on the surface of the LMFP; and is characterized in that it satisfies the following relational expression 1.

[0038] [Relationship 1]

[0039] 1.65 ≤ (W c Х10) / S0≤ 2.0

[0040] In the above relation 1, W c is the carbon content (wt%) in the positive electrode active material measured using an elemental analyzer, and S0 is the surface area (m) per unit mass of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

[0041] A lithium secondary battery according to the present invention is characterized by including a positive electrode including the positive electrode active material described above; a negative electrode; and an electrolyte.

[0042] The cathode active material for a lithium secondary battery and the method for manufacturing the same according to the present invention have the effect of improving electrical conductivity by uniformly coating carbon on the surface of LMFP.

[0043] Accordingly, a lithium secondary battery using the LMFP-based positive electrode active material of the present invention has the effect of improving the initial discharge capacity and rate characteristics.

[0044] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0045] Figure 1 is a diagram of the present invention (W c This is a graph showing the initial discharge capacity according to Х10) / S0.

[0046] Figure 2 is (W) of the present invention c This is a graph showing the rate characteristics according to Х10) / S0.

[0047] The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily practice the technical idea of ​​the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0048] Hereinafter, the phrase "any configuration is placed on (or below)" a component or "on (or below)" a component may mean that any configuration is placed in contact with the upper surface (or lower surface) of said component, and that other configurations may be interposed between said component and any configuration placed on (or below) said component.

[0049] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component.

[0050] Hereinafter, a cathode active material for a lithium secondary battery and a method for manufacturing the same according to some embodiments of the present invention will be described.

[0051] Research is being conducted on lithium manganese iron phosphate (LMFP) cathode active material, which substitutes manganese (Mn) for the iron (Fe) in lithium iron phosphate (LFP) cathode active material.

[0052] LMFP cathode active materials have the disadvantage of lower lithium ion diffusion rate and electrical conductivity compared to LFP cathode active materials.

[0053] Research is being conducted to form a carbon layer on the LMFP cathode active material to increase the electrical conductivity of the LMFP cathode active material, but there is a problem that the initial discharge capacity and rate characteristics are reduced as the carbon raw material affects the crystal growth of LFP during the sintering process.

[0054] As mentioned above, the LMFP cathode active material has low electrical conductivity, so high electrochemical performance (discharge capacity, rate characteristics, etc.) can be obtained by coating it with carbon or an ion conductor to improve the electrical conductivity.

[0055] However, if the carbon or ion conductor coating amount is too small, sufficient conductivity is not secured. Conversely, if the carbon or ion conductor coating amount is too large, performance deteriorates due to a decrease in the content of positive electrode active material within the positive electrode.

[0056] Accordingly, the inventors of the present invention found that it is most important to control the amount of carbon coating per area on which carbon can be coated within the LMFP cathode active material.

[0057] The inventor of the present invention coats carbon on the surface of the LMFP positive electrode active material, and the carbon content (weight %) coated on the entire positive electrode active material is “W c ” is the surface area per unit mass of the primary particles constituting one secondary particle of LMFP (m 2 / g) The result of dividing by the sum “S0”, [Relationship 1] 1.65 ≤ (W c When Х10) / S0≤ 2.0 is satisfied, the electrical conductivity is improved, and the initial discharge capacity and rate characteristics at room temperature are improved.

[0058] The above S0 is the specific surface area of ​​the secondary particle (m 2 / g), it is calculated as the sum of the surface areas of the primary particles in the secondary particles / {(volume of the secondary particle having the D50 of the positive electrode active material as a diameter) X (true density of the positive electrode active material)}, and is a value proportional to the sum of the surface areas per unit mass of the primary particles constituting the slurry.

[0059] In general, the primary particle size of the positive electrode active material obtained by drying the slurry with a spray dryer and calcining it and the slurry particle size are different from each other, and the particle size distribution also shows different characteristics, but the smaller the slurry particle size, the smaller the D50 and average size of the primary particles of the positive electrode active material.

[0060] That is, it can be seen that the slurry particle size and the D50 and average size of the primary particles constituting the positive electrode active material are proportional.

[0061] From this point of view, it was assumed that the particle size distribution of the crushed slurry and the particle size distribution of the primary particles within the secondary particles of LMFP were similar.

[0062] And, since the particle size of the pulverized slurry is the same as the particle size of the primary particles constituting the pulverized slurry, the particle size of the primary particles constituting the pulverized slurry is the D50 value obtained by measuring the particle size of the pulverized slurry.

[0063] The inventor of the present invention calculated the sum of the surface areas of the primary particles constituting the slurry using the particle size measurement data (volume) of the slurry after wet milling or the primary particle size distribution data of the CP-SEM cross-section.

[0064] The sum of the surface areas of the primary particles constituting the above slurry was calculated by calculating the value of (volume of primary particles of a specific size) × (ratio of primary particles of that size) for each particle size and then adding them all together.

[0065] Afterwards, the above calculated surface area sum was divided by the mass of the secondary particles, which is "the volume of the secondary particles having the diameter D50 of the particle size measurement data (Volume) of the active material X the true density of the positive electrode active material", to obtain S0.

[0066] The mass of the secondary particles was obtained by multiplying the volume of the secondary particles by the true density of the LMFP active material. The true density was arbitrarily set to 3.2 g / cc.

[0067] The volume of the secondary particles of the positive electrode active material was calculated by measuring the particle size of the LMFP positive electrode active material to obtain the D50 value and assuming that the shape of the secondary particles was spherical.

[0068] In the process of calculating the surface area and volume of primary particles, all particles were assumed to be spherical.

[0069] The actual C content of the active material, W, was determined using a Flashsmart CHNS / O elemental analyzer from ThermoFisher. C was obtained. And (W c Х10) / S0 was set to relation 1.

[0070] (W) of the present invention c If the Х10) / S0 value is less than 1.65, the electrical conductivity of the lithium secondary battery is not sufficiently secured. Conversely, (W c When the Х10) / S0 value exceeded 2.0, the performance of the lithium secondary battery deteriorated due to a decrease in the content of the LMFP cathode active material in the cathode.

[0071] [Relationship 1] of the present invention 1.65 ≤ (W c It has technical significance in that the electrochemical performance of a lithium secondary battery can be secured only when Х10) / S0≤ 2.0 is satisfied.

[0072] Therefore, it was confirmed that the carbon coating amount per area calculated from the carbon content of the LMFP cathode active material has a significant effect on the room temperature initial discharge capacity and rate characteristics of a lithium secondary battery.

[0073] <Cathode active material for lithium secondary batteries>

[0074] The positive electrode active material according to the present invention is LiMn a Fe bIt is characterized by including an LMFP represented by PO4(a + b = 1, a > 0, b > 0) and a carbon layer coated on the surface of the LMFP, and satisfying the following relational expression 1.

[0075] [Relationship 1]

[0076] 1.65 ≤ (W c Х10) / S0≤ 2.0

[0077] In the above relation 1, W c is the carbon content (wt%) in the cathode active material measured using a Flashsmart CHNS / O elemental analyzer from ThermoFisher, and S0 is the surface area (m) per unit mass of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

[0078] The positive electrode active material according to the present invention is LiMn a Fe b Contains lithium manganese iron phosphate (LMFP) represented by PO4(a + b = 1, a > 0, b > 0).

[0079] LMFP has a secondary particle form formed by the agglomeration of multiple primary particles.

[0080] In the present invention, “primary particle” means the smallest particle unit that can be distinguished as a single lump when observing the cross-section of a positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains.

[0081] Here, “crystal grain” refers to a region where atoms within a primary particle are distinguished in the form of a lattice structure with a certain direction.

[0082] The above “secondary particle” refers to an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated together by physical or chemical bonding between the primary particles without any intentional aggregation or assembly process for the primary particles.

[0083] In this specification, a polycrystal is referred to as a material in which primary particles are aggregated to form spherical secondary particles.

[0084] LiMn a Fe b In LMFP represented by PO4(a + b = 1), a > 0, b > 0 may be present, and preferably a ≥ 0.4, b ≥ 0.4 may be present.

[0085] Here, the molar ratio of Mn and Fe can be approximately 0.5:0.5 to 0.6:0.4.

[0086] By satisfying the molar ratio of Mn and Fe to be approximately 0.5:0.5 to 0.6:0.4, the theoretical energy density is further improved.

[0087] If the molar ratio of Mn is too low, the energy density will not improve.

[0088] Conversely, if the molar ratio of Mn is too high, the stability of the lithium secondary battery may be reduced, which may cause quality problems.

[0089] Therefore, it is desirable that the molar ratio of Mn and Fe be approximately 0.5:0.5 to 0.6:0.4.

[0090] The average particle diameter (D50) of the primary particles constituting the LMFP slurry may be 100 to 240 nm, and preferably 170 to 220 nm.

[0091] As the slurry particle size becomes smaller, the average particle diameter of the primary particles in the LMFP active material also becomes smaller.

[0092] When the primary particles constituting the LMFP active material are smaller, the distance traveled by lithium ions within the primary particles decreases, allowing lithium ions to move more easily. As a result, the electrochemical performance of the LMFP cathode material can be improved.

[0093] However, if the size of the primary particles constituting the LMFP active material is reduced too much, it affects the physical properties, such as reducing the density of the cathode material, and there is a limit to improving the electrochemical performance.

[0094] From this point of view, it is desirable that the average particle diameter (D50) of the primary particles constituting the slurry satisfies 100 to 240 nm.

[0095] In the present invention, “average particle diameter (D50)” means a particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve (meaning a circle-equivalent diameter, and all particle sizes hereinafter mean circle-equivalent diameters).

[0096] The above average particle diameter (D50) can be measured, for example, using the laser diffraction method.

[0097] In order to improve the low electrical conductivity of the LMFP positive electrode active material, the present invention includes a carbon layer coated on the surface of the LMFP.

[0098] In general, during the firing process, the carbon raw material may affect the crystal growth of LFP, which may cause problems such as a decrease in the initial discharge capacity and rate characteristics.

[0099] However, in the present invention, this problem was solved by calculating the carbon coating amount per area from the carbon content of the LMFP positive electrode active material.

[0100] In the present invention, carbon is coated on the surface of the LMFP positive electrode active material, and the carbon content (weight %) coated on the entire positive electrode active material is “W c ” is the surface area per unit mass of the primary particles constituting one secondary particle of LMFP (m 2 / g) divided by the sum “S0”.

[0101] [Relationship 1]

[0102] 1.65 ≤ (W c Х10) / S0≤ 2.0

[0103] More preferably 1.68 ≤ (W c Х10) / S0≤ 2.0 may be.

[0104] In the above relation 1, W c is the carbon content (weight %) in the cathode active material measured using a Flashsmart CHNS / O elemental analyzer from ThermoFisher.

[0105] The above S0 is the surface area per unit mass (m) of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

[0106] To set the value of relation 1 to 1 to 10, W c Relationship 1 can be satisfied by multiplying by 10 or dividing the left and right sides by 10, and in the present invention, W c Multiplied by 10.

[0107] In equation 1, 1.65 ≤ (W c When Х10) / S0≤ 2.0 is satisfied, the electrical conductivity is improved, which has the effect of improving the initial discharge capacity and rate characteristics at room temperature.

[0108] In equation 1 (W c If the Х10) / S0 value is less than 1.65, there is a problem that the electrical conductivity of the lithium secondary battery is not sufficiently secured. On the other hand, (W c If the Х10) / S0 value exceeds 2.0, there is a problem that the performance of the lithium secondary battery deteriorates due to a decrease in the content of the LMFP positive electrode active material.

[0109] Therefore, the carbon coating amount per area (W) calculated from the carbon content of the LMFP cathode active material c By satisfying X10) / S0 of 1.65 to 2.0, the room temperature initial discharge capacity and rate characteristic effects of a lithium secondary battery can be secured.

[0110] From this point of view, the carbon content of the carbon layer may be 1.5 to 1.8 wt%, and preferably 1.54 to 1.77 wt%, with respect to 100 wt% of the entire positive electrode active material.

[0111] Since the carbon content of the carbon layer satisfies 1.5 to 1.8 wt%, carbon or a conductive coating can be sufficiently formed on the surface of all primary particles, and there is a beneficial effect in satisfying the above relational expression 1. In particular, since carbon is uniformly dispersed in the positive electrode active material, there is an effect of improving the electrical conductivity of the lithium secondary battery and further improving the room temperature initial discharge capacity and room temperature rate characteristics.

[0112] The carbon may include at least one of glucose, sucrose, fructose, lactose, maltose, graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, a material having a crystal structure including graphene, and a material having a crystal structure including graphite, and preferably may include glucose.

[0113] The above positive electrode active material may further include one or more doping elements selected from Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, Y, P, V, and Sr, and preferably may further include a Ti doping element.

[0114] By including more doping elements in the positive electrode active material, high-temperature life and thermal stability can be further improved.

[0115] The positive electrode active material coated with a carbon layer on the surface of the LMFP may be a spherical secondary particle, and spherical may also mean a shape close to a spherical shape.

[0116] In this way, the cathode active material of the present invention coats a carbon layer on LMFP, and [Relationship 1] 1.65 ≤ (W c By satisfying X10) / S0≤ 2.0, the room temperature initial discharge capacity and room temperature rate characteristics of a lithium secondary battery can be improved.

[0117] <Method for manufacturing positive electrode active material>

[0118] The method for manufacturing a positive electrode active material according to the present invention is characterized by including a step of mixing and grinding an LMFP precursor and a carbon precursor, a step of spray-drying a slurry obtained by the grinding, and a step of calcining a powder obtained by the spray-drying to manufacture a positive electrode active material having a carbon layer coated on the surface of LMFP.

[0119] Step of mixing and grinding the LMFP precursor and carbon precursor

[0120] As LMFP precursors, a lithium precursor, a phosphorus precursor, an iron precursor, and a manganese precursor are prepared, and the LMFP precursor and carbon precursor are mixed and milled, and then pulverized for 4 to 5 hours.

[0121] The lithium (Li) precursor may include at least one of Li2CO3, Li(OH), Li(OH)·H2O, LiNO3, and LiH2PO4, and preferably may include at least one of Li2CO3 and LiH2PO4.

[0122] The phosphorus (P) precursor may include at least one of lithium dihydrogen phosphate (LiH2PO4) and FePO4. The lithium dihydrogen phosphate (LiH2PO4) can be obtained by reacting lithium phosphate (Li3PO4), an intermediate product, with a phosphoric acid (H3PO4) solution during the process of producing lithium carbonate or lithium hydroxide in a salt lake.

[0123] The iron (Fe) precursor may include FePO4, etc.

[0124] The manganese (Mn) precursor may include Mn3O4, etc.

[0125] In the above LMFP, the main elements iron (Fe) and manganese (Mn): lithium (Li) can be mixed in a molar ratio of 1:1.00 to 1.08.

[0126] Additionally, in the above LMFP, the sum of the main elements iron (Fe) and manganese (Mn): titanium (Ti) can be mixed in a molar ratio of 1:0.003 to 0.007.

[0127] In order to improve the electrical conductivity of a lithium secondary battery, 1.5 to 1.8 wt% of the carbon precursor can be mixed with respect to the total 100 wt% of the LMFP precursor and the carbon precursor, and preferably 1.54 to 1.77 wt% can be mixed.

[0128] By satisfying the content of the carbon precursor of 1.5 to 1.8 wt%, carbon is uniformly coated on the surface of the positive electrode active material, which has a beneficial effect in improving the electrical conductivity of the lithium secondary battery.

[0129] The carbon precursor may be a mixture of at least one of glucose, sucrose, fructose, lactose, maltose, graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, a material having a crystal structure including graphene, and a material having a crystal structure including graphite, and preferably, glucose may be mixed.

[0130] In addition, one or more dispersants selected from the group consisting of citric acid, fumaric acid, adipic acid, succinic acid, tartaric acid, glutarinc acid, maleic acid, oxalic acid, malonic acid, and ascorbic acid may be further mixed, and citric acid may be further mixed, preferably.

[0131] In the process of manufacturing a cathode active material, by further mixing a dispersant, the precursors in the slurry are uniformly dispersed, which is advantageous in manufacturing an olivine-based LMFP cathode active material for lithium secondary batteries of excellent quality.

[0132] For 100 wt% of the total precursor constituting the positive electrode active material, up to 10 wt% of the dispersant may be further mixed, and specifically up to 5 wt% may be further mixed, but this is not limited thereto.

[0133] In the step of mixing and pulverizing the LMFP precursor and the carbon precursor, one or more doping elements selected from Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, Y, P, V, and Sr may be further mixed, and preferably, a Ti doping element may be further mixed.

[0134] In the process of manufacturing the positive electrode active material, high-temperature life and thermal stability can be further improved by mixing more doping elements.

[0135] LMFP precursor and carbon precursor can be mixed and milled and pulverized for 4 to 5 hours. Immediately after pulverization, the smaller the average particle size (D50) of the LMFP slurry, the more nano-sized particles are formed, and the formed nano-sized particles can form secondary particles.

[0136] The average particle size (D50) of the slurry may be 100 to 240 nm, preferably 170 to 220 nm.

[0137] To ensure that the average particle size (D50) of the slurry is 100 to 240 nm, grinding can be performed using beads and wet milling methods.

[0138] The rotation speed can be performed at 500 to 4000 rpm, and preferably at 1000 to 3000 rpm.

[0139] In the present invention, the electrochemical performance of an LMFP cathode material can be improved by reducing the average particle size of the slurry through grinding using a wet milling method.

[0140] That is, by lowering the average particle size of the slurry to 240 nm or less through grinding, there is a beneficial effect in controlling the average particle size of the secondary particles constituting the positive electrode active material and the primary particles constituting the secondary particles.

[0141] Step of spray drying the slurry obtained by grinding

[0142] In the spray drying step of the slurry obtained by grinding, spray drying can be performed using a spray dryer.

[0143] The injection pressure of the spray dryer may be 0.5 to 2 bar, preferably 1 to 1.5 bar. The temperature of the main chamber may be 200 to 300°C, preferably 220 to 260°C. In addition, the outlet temperature of the spray dryer may be set to 80 to 160°C, preferably 100 to 130°C.

[0144] By setting the spray pressure, main chamber temperature, and outlet temperature of the spray dryer as described above, a spherical powder can be obtained from the slurry through spray drying. The spherical powder can be a secondary particle constituting the LMFP.

[0145] A step of manufacturing a positive electrode active material having a carbon layer coated on the surface of LMFP by calcining the powder obtained by spray drying.

[0146] The powder obtained by spray drying is loaded into a sintering furnace. Thereafter, by sintering at high temperatures for a predetermined period of time in an atmosphere continuously supplied with inert gas, a positive electrode active material for a lithium secondary battery having a carbon layer coated on the surface of the LMFP can be manufactured.

[0147] The above calcination can be performed in an inert atmosphere at 630 to 700°C for 1 to 10 hours, preferably for 3 to 8 hours.

[0148] It is advantageous to exhibit the performance of the positive electrode active material when the sintering temperature and sintering time are 1 to 10 hours at 630 to 700°C.

[0149] In this way, the positive electrode active material manufactured through the steps of mixing and milling an LMFP precursor and a carbon precursor in the present invention, spray drying, and calcining has a structure in which a carbon layer is coated on the surface of the LMFP.

[0150] As mentioned above, LMFP is LiMn a Fe b It is expressed as PO4(a + b = 1, a > 0, b > 0) and satisfies the following relationship 1.

[0151] [Relationship 1]

[0152] 1.65 ≤ (W c Х10) / S0≤ 2.0

[0153]

[0154] Lithium secondary battery

[0155] A lithium secondary battery according to the present invention is characterized by including a positive electrode, a negative electrode, and an electrolyte including the positive electrode active material described above.

[0156] At this time, the 0.1C discharge capacity of the lithium secondary battery may be 150 mAh / g or more, preferably 152 mAh / g or more, and more preferably 152 to 160 mAh / g.

[0157] Additionally, the lithium secondary battery may have a 0.1C charge / discharge efficiency of 97% or more.

[0158] anode

[0159] A lithium secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator, among which the positive electrode includes a positive electrode material including a positive electrode active material, a conductive material, and a binder, and a current collector.

[0160] The positive electrode according to the present invention comprises a current collector, and a positive electrode material disposed on at least one surface of the current collector and including the positive electrode active material described above.

[0161] Therefore, a detailed description of the positive electrode active material will be omitted.

[0162] Cathode materials serve as a lithium source in lithium secondary batteries and are a key material that determines battery capacity and average voltage.

[0163] The cathode material may include a binder and a conductive material.

[0164] The above binder serves to attach the positive electrode active material particles well to each other and also to attach the positive electrode active material well to the current collector.

[0165] Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0166] The above conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery to be constructed. Examples of conductive materials that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0167] The above positive electrode is manufactured by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector.

[0168] Since such electrode manufacturing methods are widely known in the art, a detailed description thereof will be omitted herein. Examples of the solvent used include, but are not limited to, N-methylpyrrolidone.

[0169] The above-mentioned collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0170] cathode

[0171] The above negative electrode includes a current collector and a negative electrode material formed on the current collector, and the negative electrode material may include a negative electrode active material.

[0172] The above negative active material may include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0173] The material capable of reversibly intercalating / deintercalating the lithium ions may be, for example, a carbon material, and any carbon-based negative electrode active material generally used in the lithium secondary battery may be used.

[0174] For example, the carbon-based negative electrode active material may be crystalline carbon, amorphous carbon, or a combination thereof.

[0175] As the above lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0176] Examples of materials capable of doping and dedoping the lithium include Si, SiOx (0 < x < 2), Si-Y alloy (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn).

[0177] Examples of the above transition metal oxides include vanadium oxide, lithium vanadium oxide, etc.

[0178] The above cathode material also includes a binder and may optionally further include a conductive material.

[0179] The above binder can play a role in attaching the negative electrode active material particles well to each other and also attaching the negative electrode active material well to the current collector.

[0180] The above conductive material is used to provide conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed.

[0181] The above-mentioned current collector may be selected from the group consisting of, for example, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.

[0182] The above negative and positive electrodes can be manufactured by mixing an active material, a conductive material, and a binder in a solvent to manufacture an active material composition, and applying the composition to a current collector. The present invention does not limit the method for manufacturing the electrodes.

[0183] The above solvent may include, but is not limited to, N-methylpyrrolidone.

[0184] electrolyte

[0185] The above electrolyte may be a non-aqueous electrolyte or a solid electrolyte, and one in which a lithium salt is dissolved is used.

[0186] The non-aqueous electrolyte may include an organic solvent, and the non-aqueous organic solvent may serve as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0187] Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, and 2-methyltetrahydrofuran; nitriles such as acetonitrile; and amides such as dimethylformamide. These may be used singly or in combination.

[0188] In particular, a mixed solvent of a cyclic carbonate and a chain carbonate can be preferably used.

[0189] Additionally, as an electrolyte, a gel polymer electrolyte impregnated with an electrolyte solution in a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li3N may be used.

[0190] The above lithium salt is a substance that is dissolved in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes.

[0191] The lithium salt mentioned above can be applied without limitation to those commonly used in the art as long as they do not hinder the purpose of the present invention.

[0192] For example, the lithium salt may be one selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiSbF6, LiAlO4, LiAlCl4, LiCl, and LiI.

[0193] Depending on the type of the lithium secondary battery, a separator may exist between the positive and negative electrodes.

[0194] As such separators, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and of course, mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc. may be used.

[0195] Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used, and can be classified into cylindrical, square, coin, and pouch types depending on the shape, and can be divided into bulk type and thin film type depending on the size.

[0196] The structure and manufacturing method of the battery are not limited in the present invention.

[0197] Hereinafter, specific examples of positive electrode active materials for lithium secondary batteries and their manufacturing methods will be examined.

[0198] 1. Manufacturing of positive electrode active materials for lithium secondary batteries

[0199] Example 1

[0200] 800 g of pure water, 4.8 g of citric acid, 25.7 g of glucose, 26.9 g of Li2CO3, 5.1 g of LiH2PO4, 102.2 g of FePO4, 77.5 g of Mn3O4, and 0.7 g of TiO2 were placed in a bead mill (NETZSCH MINISERIES model) containing 500 g of 0.3 mm zirconia beads, and milling was performed for 4 hours at a milling rpm value set to 3000.

[0201] The slurry obtained by the above grinding was spray-dried using a spray dryer. The spray dryer's injection pressure was set at 1.5 bar, the main chamber temperature at 240°C, and the outlet temperature at 105°C. 30 g of the powder obtained by the above spray drying was placed in a graphite saga and calcined at 650°C for 6 hours under a nitrogen atmosphere to produce an LMFP cathode active material.

[0202] At the raw material input stage, the raw materials were input so as to satisfy the molar ratios of Li / (Fe+Mn) = 1.03, P / (Fe+Mn) = 1.00, and Ti / (Fe+Mn) = 0.5 mol% (0.005).

[0203] Examples 2 to 4

[0204] An LMFP positive electrode active material was manufactured using the same manufacturing method as in Example 1, except that the firing temperature in the reduction firing step was changed to Example 2: 700°C, Example 3: 680°C, and Example 4: 630°C.

[0205] At the raw material input stage, raw materials were input so as to satisfy the molar ratios of Li / (Fe+Mn) = 1.03, P / (Fe+Mn) = 1.00, and Ti / (Fe+Mn) = 0.5 mol %.

[0206] Example 5

[0207] An LMFP positive electrode active material was manufactured using the same manufacturing method as Example 1, except that the grinding time was adjusted to 5 hours in the raw material grinding step and the calcination temperature in the reduction calcination step was changed to 670°C.

[0208] At the raw material input stage, raw materials were input so as to satisfy the molar ratios of Li / (Fe+Mn) = 1.03, P / (Fe+Mn) = 1.00, and Ti / (Fe+Mn) = 0.5 mol%.

[0209] Comparative Examples 1 to 3

[0210] An LMFP positive electrode active material was manufactured using the same manufacturing method as Example 1, except that 0.5 mm zirconia beads were used in the raw material grinding step, the grinding time was adjusted to 3 hours, and the firing temperature was changed to Comparative Example 1: 650°C, Comparative Example 2: 670°C, and Comparative Example 3: 630°C.

[0211] Comparative Examples 4 to 6

[0212] An LMFP positive electrode active material was manufactured using the same manufacturing method as Example 1, except that the grinding time was adjusted to 2 hours in the raw material grinding step and the firing temperature was changed to Comparative Example 4: 650°C, Comparative Example 5: 670°C, and Comparative Example 6: 630°C.

[0213] Comparative Example 7

[0214] An LMFP cathode active material was manufactured using the same manufacturing method as Example 2, except that the input amounts of Li2CO3 and LiH2PO4 were increased to satisfy the molar ratios of Li / (Fe+Mn) = 1.09 and P / (Fe+Mn) = 1.02 in the raw material grinding step.

[0215] Comparative Example 8

[0216] An LMFP cathode active material was manufactured using the same manufacturing method as Example 1, except that the raw material input was changed to citric acid 5.1 g, glucose 27.6 g, Li2CO3 30.1 g, LiH2PO4 103.3 g, FePO4 100.5 g, and Mn3O4 76.2 g, and the calcination temperature in the reduction calcination step was set to 670°C. (→ Li / (Fe+Mn) = 1.09, P / (Fe+Mn) = 1.00)

[0217] Comparative Example 9

[0218] An LMFP cathode active material was manufactured using the same manufacturing method as Example 1, except that the raw material input amounts were changed to 5.1 g of citric acid, 27.3 g of glucose, 27.4 g of Li2CO3, 108.8 g of LiH2PO4, 99.2 g of FePO4, and 75.3 g of Mn3O4, and the calcination temperature in the reduction calcination step was set to 670°C. (→ Li / (Fe+Mn) = 1.09, P / (Fe+Mn) = 1.04)

[0219] 2. Physical property evaluation method and results

[0220] 1) Calculation of S0 of LMFP cathode active material

[0221] The particle size of the slurry immediately after wet grinding was measured using a Mastersizer 3000 from Malvern Panalytical.

[0222] Using the above measured slurry particle size distribution data, the sum of the surface areas per unit mass of the primary particles constituting the slurry was calculated.

[0223] First, the sum of the surface areas of the primary particles constituting the slurry was calculated by calculating the (volume of primary particles of a specific size) × (ratio of primary particles of the corresponding size) values ​​for each particle size and then adding them all together. Afterwards, the calculated value was divided by the mass of the secondary particles of the active material (volume of secondary particles having a diameter of D50 of the particle size measurement data (Volume) X true density of the positive electrode active material) to obtain S0.

[0224] S0: Sum of the surface areas of the primary particles constituting the secondary particles / {(Volume of the secondary particle with a diameter of D50 of the positive electrode active material) X (True density of the positive electrode active material)}

[0225] 2) Carbon content analysis

[0226] The carbon content of the LMFP cathode active material was measured using a Flashsmart CHNS / O elemental analyzer from ThermoFisher.

[0227] 3) Electrochemical evaluation

[0228] A slurry for manufacturing an electrode plate was prepared by adding 4.3 g of NMP to 4.5 g of LMFP cathode active material, 0.25 g of Super P, and 3.125 g of liquid binder KF7208 (PVDF 8 wt.%, Kureha).

[0229] The above slurry was coated on Al foil using a doctor blade, dried at 130°C for 2 hours, and then rolled to produce a positive electrode plate having a thickness of 0.07 to 0.09 mm.

[0230] The above positive electrode plate was punched to a size suitable for a CR2032 coin cell, and a coin half-cell was manufactured using the punched positive electrode plate, lithium metal negative electrode plate, and EL5 electrolyte.

[0231] Electrochemical evaluation was performed by aging the above half-cell at 25°C for 23 hours and then conducting a charge-discharge test. Specifically, one formation cycle (2.5–4.4 V) was performed at 0.1 C charge / discharge, and then the charge rate was fixed at 0.1 C and the discharge rates were measured once each at 0.1, 0.33, 1.0, 2.0, 5.0, and 10.0 C. (The capacity based on 1C was set to 150 mAh / g.)

[0232] [Table 1]

[0233]

[0234] Examples 1 to 5 satisfy the molar ratio of elements, grinding time, spray drying, and firing conditions when adding raw materials of the present invention.

[0235] Examples 1 to 5 showed that the average particle size (D50) of the pulverized slurry was 187 to 202 nm.

[0236] Examples 1 to 5 showed that the value of equation 1 was 1.65 to 2.0 when 1.5 to 1.8 wt% of carbon was coated on the LMFP surface.

[0237] Accordingly, the room temperature initial discharge capacity of the lithium secondary battery was 150 mAh / g or more, and at the same time, the room temperature charge / discharge efficiency was 97% or more.

[0238] Comparative Examples 1 to 3 had a lower grinding time than Example 1, and the average particle size (D50) of the grinded slurry was 334 nm.

[0239] Comparative examples 1 to 3 exceeded the upper limit of 2.0 of relational expression 1, and the room temperature initial discharge capacity of the lithium secondary battery was considerably low.

[0240] Comparative Examples 4 to 6 had a lower grinding time than Comparative Examples 1 to 3, and the average particle size (D50) of the ground slurry was 394 nm.

[0241] Comparative examples 4 to 6 exceeded the upper limit of 2.0 of relational expression 1, and the room temperature initial discharge capacity of the lithium secondary battery was considerably low.

[0242] Comparative Example 7 satisfied the average particle size (D50) of the crushed slurry of 240 nm or less, but the carbon content was less than 1.5 wt%, which was lower than the lower limit of equation 1.

[0243] Comparative Example 7 showed that the room temperature initial discharge capacity and room temperature charge / discharge efficiency of the lithium secondary battery were low.

[0244] Comparative Example 8 satisfied the average particle size (D50) of the crushed slurry of 240 nm or less, but the carbon content was less than 1.5 wt%, which was lower than the lower limit of equation 1.

[0245] Comparative Example 8 showed that the room temperature initial discharge capacity and room temperature charge / discharge efficiency of the lithium secondary battery were very low.

[0246] Comparative Example 9 satisfied the average particle size (D50) of the crushed slurry of 240 nm or less, but the carbon content exceeded 1.8 wt%, which was higher than the upper limit of equation 1.

[0247] Comparative Example 9 showed that the room temperature initial discharge capacity and room temperature charge / discharge efficiency of the lithium secondary battery were low.

[0248] Figure 1 is a diagram of the present invention (W c Х10) / S0 is a graph showing the initial discharge capacity according to the present invention, and Fig. 2 is a graph showing the initial discharge capacity according to the present invention (W c This is a graph showing the rate characteristics according to Х10) / S0.

[0249] In Figures 1 and 2, the X-axis is (W c The value is Х10) / S0.

[0250] Referring to FIGS. 1 and 2, Examples 1 to 5 satisfied Equation 1, thereby exhibiting a room temperature initial discharge capacity of 150 mAh / g or more and a room temperature charge / discharge efficiency of 97% or more.

[0251] On the other hand, Comparative Examples 1 to 9 did not satisfy Equation 1, exhibiting an initial discharge capacity at room temperature of less than 150 mAh / g, and a charge / discharge efficiency at room temperature dropping from around 97% to 79%.

[0252] From these results, it can be seen that the carbon coating amount per area calculated from the carbon content of the LMFP cathode active material has a significant influence on the room temperature initial discharge capacity and rate characteristics of a lithium secondary battery.

[0253] Although the present invention has been described with reference to the drawings exemplified above, it is to be understood that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications may be made by those skilled in the art within the scope of the technical idea of ​​the present invention. Furthermore, even if the operational effects according to the configuration of the present invention have not been explicitly described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be acknowledged.

Claims

1. LiMn a Fe b LMFP represented by PO4(a + b = 1, a > 0, b > 0); and A carbon layer coated on the surface of the LMFP; A positive electrode active material satisfying the following relational expression 1. [Relationship 1] 1.65 ≤ (W c Х10) / S0≤ 2.0 In the above relation 1, W c is the carbon content (wt%) in the positive electrode active material measured using an elemental analyzer, and S0 is the surface area (m) per unit mass of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

2. In paragraph 1, The carbon content of the above carbon layer is A positive electrode active material of 1.5 to 1.8 wt% relative to 100 wt% of the total positive electrode active material.

3. In paragraph 1, The above positive electrode active material is a positive electrode active material having a spherical shape.

4. In paragraph 1, The above carbon is a cathode active material comprising at least one of glucose, sucrose, fructose, lactose, maltose, graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, a material having a crystal structure including graphene, and a material having a crystal structure including graphite.

5. In paragraph 1, The above positive electrode active material further comprises one or more doping elements selected from Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, Y, P, V, and Sr. 6.(a) A step of mixing and pulverizing an LMFP precursor and a carbon precursor; (b) a step of spray drying the slurry obtained by the above grinding; and (c) a step of manufacturing a positive electrode active material having a carbon layer coated on the surface of LMFP by firing the powder obtained by the above spray drying; The above LMFP is LiMn a Fe b It is expressed as PO4(a + b = 1, a > 0, b > 0), A method for manufacturing a positive electrode active material satisfying the following relational expression 1. [Relationship 1] 1.65 ≤ (W c Х10) / S0≤ 2.0 In the above relation 1, W c is the carbon content (wt%) in the positive electrode active material measured using an elemental analyzer, and S0 is the surface area (m) per unit mass of the primary particles constituting one secondary particle of LMFP. 2 / g) is the sum.

7. In paragraph 6, In the step of mixing and pulverizing the LMFP precursor and carbon precursor above (a), A method for producing a cathode active material, wherein the average particle size (D50) of the slurry obtained by mixing and milling a lithium precursor, a phosphorus precursor, an iron precursor, a manganese precursor, and a carbon precursor is 100 to 240 nm.

8. In paragraph 6, A method for producing a cathode active material, wherein in step (a) above, 1.5 to 1.8 wt% of a carbon precursor is mixed with respect to the total 100 wt% of the LMFP precursor and the carbon precursor.

9. In paragraph 7, In the above LMFP, A method for manufacturing a cathode active material in which the sum of iron (Fe) and manganese (Mn) and lithium (Li) are mixed in a molar ratio of 1:1.00 to 1.

08.

10. In paragraph 6, A method for producing a positive electrode active material, wherein in the step (c) above, calcination is performed in an inert atmosphere and at 630 to 700°C.

11. In paragraph 6, A method for producing a cathode active material, wherein in the step (a), the carbon precursor comprises at least one of glucose, sucrose, fructose, lactose, maltose, graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, a material having a crystal structure including graphene, and a material having a crystal structure including graphite.

12. In paragraph 6, A method for producing a positive electrode active material, wherein in the step (a), at least one dispersant selected from the group consisting of citric acid, fumaric acid, adipic acid, succinic acid, tartaric acid, glutarinc acid, maleic acid, oxailic acid, malonic acid, and ascorbic acid is further mixed.

13. In paragraph 6, A method for producing a positive electrode active material, wherein in the step (a) above, one or more doping elements of Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, Y, P, V, and Sr are further mixed.

14. In paragraph 13, When Ti is further mixed as the above doping element, In LMFP, a method for manufacturing a cathode active material in which the sum of iron (Fe) and manganese (Mn): titanium (Ti) is mixed in a molar ratio of 1:0.003 to 0.

007.

15. A positive electrode comprising the positive electrode active material of any one of claims 1 to 5; cathode; and A lithium secondary battery comprising an electrolyte.

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