Positive electrode active material for secondary batteries

Abstract

The present invention provides a positive electrode active material that reduces residual lithium present in positive electrode active material particles, thereby improving capacity, efficiency, and output characteristics. [Solution] The positive electrode active material particles according to one aspect of the present invention contain sulfur (S) and boron (B), and when the ratio of sulfur (S) concentration (ppm) to boron (B) concentration (ppm) is S / B, the ratio 8 ≤ S / B ≤ 20.

Description

Technical Field

[0001] The present invention relates to positive electrode active material particles and a positive electrode active material for a secondary battery containing the same. More specifically, the present invention relates to positive electrode active material particles in which sulfur (S) and boron (B) are mixed and coated, and the coating content, coating conditions, and manufacturing method are controlled, and a positive electrode active material for a secondary battery containing the same.

Background Art

[0002] With the development of portable mobile electronic devices such as smartphones, MP3 players, and tablet PCs, the demand for secondary batteries capable of storing electrical energy has explosively increased. In particular, with the emergence of electric vehicles, medium and large-sized energy storage systems, and portable devices that require high energy density, the demand for lithium secondary batteries is increasing.

[0003] As a lithium composite oxide contained in the positive electrode active material, the most spotlighted substance recently is lithium nickel manganese cobalt oxide Li(Ni x Co y Mn2)O2 (where x, y, and z are the atomic fractions of independent oxide composition elements, 0 < x ≤ 1, 0 < y ≤ 1, 0 < z ≤ 1, and 0 < x + y + z ≤ 1).

[0004] This positive electrode active material has the advantage of exhibiting a high capacity because it is used at a higher voltage than LiCoO2, which has been actively studied and used as a positive electrode active material so far. In addition, since the Co content is relatively low, it has the advantage of being inexpensive.

[0005] However, such lithium composite oxides are accompanied by volume changes due to the intercalation and deintercalation of lithium ions during charge and discharge.

[0006] During charging and discharging, the primary particles of the lithium composite oxide undergo rapid volume changes, and repeated charging and discharging can cause cracks in the secondary particles, as well as collapse of the crystal structure or a phase transition of the crystal structure.

[0007] To compensate for these shortcomings, demand has begun to increase for high-nickel cathode active materials, which have a high nickel (Ni) content among all metals excluding lithium (Li) used in secondary batteries. [Overview of the project] [Problems that the invention aims to solve]

[0008] Due to the high Li / M ratio during the manufacturing of the positive electrode active material, the residual lithium content remaining in the positive electrode active material after firing is high, making cell manufacturing difficult due to the gelation phenomenon during electrode slurry production.

[0009] Furthermore, while a water washing process is introduced during the manufacturing of the positive electrode active material to remove residual lithium present within it, there is a problem in that the surface of the positive electrode active material particles is damaged during the water washing process, leading to a decrease in battery performance.

[0010] Furthermore, a problem arises where the particle crystallinity is inhibited and strain is induced by a stacking fault phenomenon caused by sulfur compounds, which are impurities present inside the precursor particles of the positive electrode active material.

[0011] In particular, high-nickel cathode active materials have the disadvantage of being more problematic due to the higher residual lithium content present in the particles, resulting in reduced stability and decreased output due to the high Ni content.

[0012] To solve the aforementioned problems, the present invention aims to manufacture a positive electrode active material that can improve both output and capacity characteristics by employing a non-water washing process during the manufacturing of the positive electrode active material to reduce damage to the positive electrode surface while significantly reducing residual lithium, by mixing and coating sulfur (S) and boron (B), and by controlling the coating content, coating conditions, and manufacturing method.

[0013] In addition, the present invention performs mixing and coating of sulfur (S) and boron (B) in a semi-wet spray process, optimizes the mixing content ratio, and discharges internal impurities such as sulfur compounds that induce the stacking fault phenomenon onto the surface of the positive electrode active material particles, aiming to produce a positive electrode active material that can significantly reduce the stacking fault phenomenon and strain and increase the particle crystallinity.

[0014] In addition, the present invention performs mixing and coating of sulfur (S) and boron (B) in a semi-wet spray process in a non-washing process, optimizes the mixing content ratio, and aims to produce a positive electrode active material with improved capacity, efficiency, and output characteristics compared to when sulfur (S) and boron (B) are used alone.

Means for Solving the Problems

[0015] The positive electrode active material particles according to one aspect of the present invention contain sulfur (S) and boron (B). When the ratio of the sulfur (S) concentration (ppm) to the boron (B) concentration (ppm) contained in the positive electrode active material particles is S / B, it can be 8 ≤ S / B ≤ 20.

[0016] As one aspect, the positive electrode active material particles contain sulfur (S) and boron (B). When the ratio of the sulfur (S) concentration (ppm) to the boron (B) concentration (ppm) contained in the positive electrode active material particles is S / B, it can be 10 ≤ S / B ≤ 15.

[0017] As one aspect, the boron (B) concentration (ppm) contained in the positive electrode active material particles can be 100 ppm to 600 ppm.

[0018] As one aspect, the sulfur (S) concentration (ppm) contained in the positive electrode active material particles can be 3,200 ppm to 5,000 ppm.

[0019] In one aspect, the positive electrode active material particles include a bulk region and a coating region, the coating region contains sulfur (S) and boron (B), and the sulfur (S) and boron (B) contained within the coating region may be present on a part of the surface of the bulk region.

[0020] In one aspect, the concentration (ppm) of sulfur (S) contained within the coating region may be greater than the concentration (ppm) of sulfur (S) contained in the positive electrode active material particles.

[0021] In one aspect, the positive electrode active material particles may contain Li2BO3.

[0022] In one aspect, the positive electrode active material particles may contain Li2SO4.

[0023] In one aspect, the positive electrode active material may further contain a coating oxide containing one or more selected from cobalt (Co), aluminum (Al), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), molybdenum (Mo), iron (Fe), nickel (Ni), barium (Ba), tungsten (W), yttrium (Y), niobium (Nb), and fluorine (F).

[0024] In one aspect, the positive electrode active material particles have a specific surface area measured by the nitrogen adsorption BET method of 0.42 m 2 / g to 0.5 m 2 / g.

[0025] A step of mixing and heat-treating a positive electrode active material precursor and a lithium-containing compound to produce a lithium composite oxide; a step of producing a coating solution containing a sulfur (S)-containing compound and a boron (B)-containing compound; and a step of spraying and heat-treating the produced coating solution onto the produced lithium composite oxide may be included.

[0026] In one embodiment, when the ratio of sulfur (S) concentration (ppm) to boron (B) concentration (ppm) contained in the coating liquid is defined as "S added / B added", then 1.4 ≤ S added / B added ≤ 5.0 is possible.

[0027] In one embodiment, the heat treatment temperature in the step of spraying the manufactured coating liquid onto the manufactured lithium composite oxide and heat treating it may be 250°C to 350°C.

[0028] In one embodiment, the process may further include, after the step of manufacturing the lithium composite oxide, and before the step of spraying the manufactured coating solution onto the manufactured lithium composite oxide and heat-treating it, the step of coating the manufactured lithium composite oxide with cobalt (Co).

[0029] The positive electrode active material according to one aspect of the present invention may include the positive electrode active material particles. [Effects of the Invention]

[0030] As one effect, the present invention provides a positive electrode active material that reduces residual lithium present in positive electrode active material particles and improves capacity, efficiency, and output characteristics. As one effect, the present invention provides a positive electrode active material that can significantly reduce stacking faults and strain, and increase particle crystallinity, by bringing internal impurities such as sulfur compounds that induce stacking faults due to precursors onto the surface of positive electrode active material particles.

[0031] As one effect, the present invention provides a positive electrode active material in which capacity, efficiency, and output are all improved. [Brief explanation of the drawing]

[0032] [Figure 1] Figure 1 shows SEM images of particle surfaces according to the embodiments and comparative examples of the present invention. [Figure 2] Figure 2 shows an SEM-EDS image of a particle cross-section produced by the manufacturing method of the present invention. [Figure 3]Figure 3 shows a SEM-EDS image of the particle surface produced by the manufacturing method of the present invention. [Figure 4] Figure 4 is an SEM-EDS image of a particle cross-section relating to Example 1 of the present invention. [Modes for carrying out the invention]

[0033] Expressions such as “including” as used herein should be understood as open-ended terms that may include other components.

[0034] As used herein, “preferred” and “preferred” refer to embodiments of the present invention that can provide certain advantages under certain conditions.

[0035] However, this does not intend to exclude other embodiments from the scope of the present invention.

[0036] Furthermore, singular forms used in the specification and attached claims may be intended to include plural forms unless otherwise indicated in the context.

[0037] In other words, the technical characteristics of any one particle may also refer to the technical characteristics of multiple particles, and can be intended to represent the average technical characteristics of multiple particles.

[0038] The numerical ranges used herein include lower and upper limits and all values ​​within those limits, increments logically derived from the form and width of the defined range, all values ​​that are doubly limited, and all possible combinations of upper and lower limits of numerical ranges that are limited in different forms.

[0039] Unless otherwise specified herein, values ​​outside the defined numerical range that may occur due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0040] The term "layer" includes not only shapes that are formed across the entire surface when observed in a plan view, but also shapes that are formed on only a portion of the surface.

[0041] In this specification, the meanings of "≦", "greater than or equal to", or "less than or equal to" may be replaced with the meanings of "<", "greater than", or "less than".

[0042] On the other hand, the technical features described below relate to one embodiment that achieves the effects intended for the present invention as described above.

[0043] In other words, a positive electrode active material according to one aspect of the present invention, by including the technical features of one aspect described below, can reduce residual lithium in the particles, remove sulfur impurities inside the particles originating from the precursor, increase crystallinity, and improve the capacity, efficiency, and output characteristics of a secondary battery.

[0044] This invention relates to positive electrode active material particles for secondary batteries and positive electrode active material containing a plurality of such particles.

[0045] The secondary battery of the present invention is not limited in type, as long as it is a battery that converts external electrical energy into chemical energy for storage and reuse.

[0046] As an example, the present invention may relate to a positive electrode active material for lithium-ion secondary batteries.

[0047] The present invention allows for the control of the coating content, coating conditions, and manufacturing method by mixing sulfur (S) and boron (B) in a coating to improve battery characteristics.

[0048] More specifically, the present invention allows for control of the mixing ratio when applying a mixed coating of sulfur (S) and boron (B), thereby controlling the mixed content in the bulk region and the coated region.

[0049] Furthermore, the present invention allows for a semi-wet spraying process in which aqueous sulfate solutions of sulfur (S)-containing compounds and boron (B)-containing compounds are sprayed onto the particle surface when applying a mixed coating of sulfur (S) and boron (B).

[0050] The semi-wet spraying process refers to the process of manufacturing a coating solution and spraying it onto the surface of particles.

[0051] Furthermore, in the present invention, when applying a mixed coating of sulfur (S) and boron (B), the heat treatment temperature can be controlled by a semi-wet spray process in which sulfate aqueous solutions of the sulfur (S)-containing compound and the boron (B)-containing compound are sprayed onto the fired product.

[0052] Furthermore, the present invention allows for the control of doping elements and additional coating elements, as well as the control of the doping and coating sequence and conditions.

[0053] Furthermore, the present invention can be carried out in a non-water washing process.

[0054] First, the positive electrode active material particles and positive electrode active material of the present invention will be described.

[0055] The positive electrode active material particles according to one aspect of the present invention may contain sulfur (S) and boron (B).

[0056] The inventors have confirmed that when sulfur (S) and boron (B) are mixed together with positive electrode active material particles to form a coating material, the capacity, efficiency, and output of the secondary battery can all be improved compared to when sulfur (S) and boron (B) are used individually.

[0057] In a more preferred embodiment, when the ratio of sulfur (S) concentration (ppm) to boron (B) concentration (ppm) contained in the positive electrode active material particles is denoted as S / B, S / B may be 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 20 or less, 18 or less, 15 or less, 14 or less, 13 or less, 12 or less, or 11 or less.

[0058] When applying a mixed coating of sulfur (S) and boron (B), not only the capacity and efficiency but also the output characteristics can be improved within the numerical range of the aforementioned concentration ratio of positive electrode active material particles.

[0059] In one embodiment, the boron (B) concentration (ppm) contained in the positive electrode active material particles may be 100 ppm or more, 150 ppm or more, 200 ppm or more, 250 ppm or more, 300 ppm or more, 600 ppm or less, 550 ppm or less, 500 ppm or less, 450 ppm or less, 400 ppm or less, or 350 ppm or less.

[0060] When applying a mixed coating of sulfur (S) and boron (B), it is possible to improve not only the capacitance characteristics but also the output characteristics within the numerical range of the boron (B) concentration of the positive electrode active material particles.

[0061] In one embodiment, the sulfur (S) concentration (ppm) contained in the positive electrode active material particles may be 3,200 or more, 3,500 ppm or more, 4,000 ppm or more, 5,000 ppm or less, or 4,500 ppm or less.

[0062] When applying a mixed coating of sulfur (S) and boron (B), it is possible to improve not only the capacitance characteristics but also the output characteristics within a numerical range related to the sulfur (S) concentration in the positive electrode active material particles.

[0063] In one embodiment, the positive electrode active material particles may include a bulk region and a coating region.

[0064] In one embodiment, the bulk region may be a lithium composite oxide.

[0065] In one embodiment, the bulk region may be a lithium composite oxide containing nickel (Ni).

[0066] In one embodiment, the lithium composite oxide can be represented by the following chemical formula 1. [Chemical formula 1] Li a Ni x M1 y M21-x-yO2 In the above chemical formula 1, M1 is selected from the group consisting of cobalt (Co), manganese (Mn), aluminum (Al), and combinations thereof, and M2 is selected from the group consisting of Zr, Mn, Al, B, S, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Na, K, Hf, Ta, Cu, and combinations thereof, with 0.9 ≤ a ≤ 1.2, 0.1 ≤ x < 1.0, 0.0 ≤ y ≤ 0.5, and 0.0 ≤ 1 - xyz ≤ 0.5.

[0067] In one embodiment, in the above chemical formula 1, a, which represents the mol% of lithium (Li) relative to the mol% of all transition metals excluding lithium (Li), may be 0.9 or more, 1.0 or more, 1.2 or less, 1.1 or less, or 1.05 or less.

[0068] In one embodiment, in the above chemical formula 1, x, which represents the mol% of nickel (Ni) relative to the mol% of all transition metals excluding lithium (Li), can be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more, and in particular, the present invention can be a high-nickel (high-Ni) oxide.

[0069] While such high-nickel cathode active materials have the advantage of high energy density, they also suffer from a problem where their lifetime characteristics deteriorate rapidly at room temperature and high temperatures due to increased structural instability caused by Li / Ni cation mixing, physical disruption of internal particles due to microcracks, and deepening electrolyte depletion as the Ni content increases.

[0070] Furthermore, the high Li / M ratio during the manufacturing of the positive electrode active material results in a high residual lithium content remaining in the positive electrode active material after firing, which makes cell manufacturing difficult due to gelation during electrode slurry production.

[0071] The present invention can solve such problems, which are particularly serious with high-nickel (high-Ni) cathode active materials, by coating a mixture of sulfur (S) and boron (B) and controlling the coating content, coating conditions, and manufacturing method.

[0072] In one embodiment, in the above chemical formula 1, if y represents the mol% of cobalt (Co) relative to the mol% of all transition metals excluding lithium (Li), then y may be 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less, 0.08 or less, or 0.06 or less.

[0073] In particular, the present invention may be a low-cobalt (Low-Co) oxide.

[0074] As battery demand surges, the price of cobalt (Co) is rising, which can lead to instability in the supply of cobalt (Co).

[0075] Therefore, in order to ensure price stabilization and resource stability of positive electrode active materials, it is required to reduce the cobalt (Co) content. However, lowering the cobalt (Co) content leads to problems such as a decrease in energy density, low-temperature characteristics, and rate characteristics.

[0076] The present invention can solve such problems, which are particularly enhanced in low-cobalt (Low-Co) cathode active materials, by coating a mixture of sulfur (S) and boron (B) and controlling the coating content, coating conditions, and manufacturing method.

[0077] In one embodiment, in the above chemical formula 1, if y means Al and / or Mn mol% relative to the total transition metal mol% excluding lithium (Li), then y may be 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less, 0.1 or more, 0.2 or more, or 0.3 or more.

[0078] In one embodiment, the coating region may be a region distinct from the lithium composite oxide particles, which constitute the bulk region.

[0079] On the other hand, when coating lithium composite oxide particles according to one aspect of the present invention, some of the coating elements may be present within the lattice structure of the primary particles contained in the lithium composite oxide particles.

[0080] This is described as lithium composite oxide particles being doped, and the lithium composite oxide particles with respect to the bulk region are defined to include all of these doped regions.

[0081] In another aspect, when coating lithium composite oxide particles according to one aspect of the present invention, some of the coating elements may form a coating region where the coating material is present.

[0082] Such coating materials may be present on the surface of secondary particles of lithium composite oxide particles and / or at the grain boundaries between primary particles of lithium composite oxide.

[0083] In this context, the grain boundary between primary particles refers to the region that includes the space between primary particles and the entire surface of the primary particles.

[0084] In one embodiment, the coating region may contain sulfur (S) and boron (B).

[0085] The sulfur (S) and boron (B) contained within the coating region may be present on a portion of the surface of the bulk region.

[0086] In other words, unlike the wet process in which active material particles are immersed in a coating solution, the sulfur (S) and boron (B) contained within the coating region may not cover the entire surface of the bulk region.

[0087] On the other hand, the coating region may be formed on the surface of the bulk region, or it may be formed at the grain boundaries between primary particles present on the surface portion of the bulk region.

[0088] On the other hand, the surface portion refers to the area up to where a coating region exists, formed by the coating material seeping through the space between primary particles.

[0089] On the other hand, in one embodiment, the area ratio of the region on the surface of the bulk region in which sulfur (S) and boron (B) contained in the coating region exist may be 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less.

[0090] In one embodiment, the thickness of the coating region formed on the surface of the bulk region may be 1 nm or more, 10 nm or more, 1 μm or less, 500 nm or less, 300 nm or less, or 100 nm or less.

[0091] In one embodiment, the sulfur (S) concentration (ppm) contained within the coating region may be greater than the sulfur (S) concentration (ppm) contained within the positive electrode active material particles. That is, the weight percentage of sulfur (S) contained within the coating region relative to the total weight percentage of the coating region may be greater than the weight percentage of sulfur (S) contained within the positive electrode active material particles relative to the total weight percentage of the positive electrode active material particles.

[0092] In this case, due to the manufacturing method of the present invention, the sulfur (S) introduced will be present on the particle surface rather than inside the particle, and sulfur (S) impurities that were present in the precursor particles will also come to the particle surface. Therefore, the sulfur (S) concentration (ppm) contained in the coating region may be greater than the sulfur (S) concentration (ppm) contained in the positive electrode active material particles.

[0093] In one embodiment, the sulfur (S) concentration (ppm) contained within the coating region may be greater than the sulfur (S) concentration (ppm) contained within the bulk region.

[0094] In one embodiment, the boron (B) concentration (ppm) contained within the coating region may be greater than the boron (B) concentration (ppm) contained within the positive electrode active material particles.

[0095] In other words, the weight percentage of boron (B) contained within the coating region, based on the total weight percentage of the coating region, may be greater than the weight percentage of boron (B) contained within the positive electrode active material particles, based on the total weight percentage of the positive electrode active material particles.

[0096] In this case, the boron (B) introduced will be present on the particle surface rather than inside the particle, according to the manufacturing method of the present invention.

[0097] In one embodiment, the boron (B) concentration (ppm) contained within the coating region may be greater than the boron (B) concentration (ppm) contained within the bulk region.

[0098] In one embodiment, 90% or more, or even 100%, of the boron (B) introduced during the coating of the positive electrode active material particles may be present in the coating region.

[0099] In one embodiment, boron(B) may not be present in the bulk region, but may be present only in the coating region.

[0100] The positive electrode active material particles may contain Li2BO3.

[0101] This invention can reduce residual lithium by proceeding in a non-water washing process, thereby reducing damage to the surface of positive electrode active material particles, while converting compounds containing residual lithium such as LiOH and Li2BO3 into coating materials such as Li2BO3, and further reducing residual lithium.

[0102] In one embodiment, the Li2BO3 may exist as a coating material on a portion of the surface of the bulk region.

[0103] Furthermore, the Li2BO3 can also be formed at grain boundaries between primary particles present on the surface of the bulk region.

[0104] In one embodiment, the Li2BO3 concentration (ppm) contained in the positive electrode active material particles may be 100 ppm or more, 300 ppm or more, 500 ppm or more, 700 ppm or more, 1,000 ppm or more, 3,500 ppm or less, 3,000 ppm or less, 2,500 ppm or less, 2,000 ppm or less, 1,500 ppm or less, or 1,000 ppm or less.

[0105] On the other hand, the boron (B) introduced in this invention may exist in an amorphous glassy state in addition to the Li2BO3 mentioned above.

[0106] On the other hand, in one embodiment, the present invention controls the heat treatment temperature to preferably be within 280°C to 320°C when coating with boron(B), so that boron(B) is not doped into the particle lattice structure and can be present as a coating material on or in the surface portion of the bulk region.

[0107] In one embodiment, the positive electrode active material particles may contain Li2SO4.

[0108] This invention can reduce residual lithium by proceeding in a non-water washing process, thereby reducing damage to the surface of the positive electrode active material particles, while converting compounds containing residual lithium such as LiOH and Li2BO3 into coating materials such as Li2SO4.

[0109] In one embodiment, the Li2SO4 concentration (ppm) contained in the positive electrode active material particles may be 2,000 ppm or more, 3,000 ppm or more, 4,000 ppm or more, 5,000 ppm or more, 6,000 ppm or more, 7,000 ppm or more, 8,000 ppm or more, 10,000 ppm or more, 16,000 ppm or less, 14,000 ppm or less, 12,000 ppm or less, 10,000 ppm or less, 8,000 ppm or less, 6,000 ppm or less, or 4,000 ppm or less.

[0110] In one embodiment, the Li2SO4 concentration (ppm) may include not only the concentration due to sulfur (S) added for coating, but also the concentration (ppm) that results from sulfur (S)-containing impurities present in the precursor particles coming to the particle surface and forming Li2SO4.

[0111] In one embodiment, the Li2SO4 may exist as a coating material on a portion of the bulk region surface and at grain boundaries between primary particles present on the surface portion of the bulk region.

[0112] On the other hand, in one embodiment, the present invention controls the heat treatment temperature to preferably be within 280°C to 320°C when applying a sulfur (S) coating, so that the sulfur (S) is not doped into the particle lattice structure and can be present as a coating material on or in the surface portion of the bulk region.

[0113] Furthermore, in order to further improve battery characteristics, the present invention allows for the application of a sulfur (S) and boron (B) mixed coating in a tertiary heat treatment step, and enables control of doping and coating elements, their content, and heat treatment conditions in the primary and secondary heat treatments.

[0114] More specifically, doping can be achieved by mixing doping elements into precursor particles and performing a primary heat treatment.

[0115] For example, the doping element may be a substance selected from the group consisting of Zr, Mn, Al, B, S, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Na, K, Hf, Ta, Cu, and combinations thereof.

[0116] Most preferably, aluminum (Al) can be used as a doping element during the primary heat treatment.

[0117] In one embodiment, the molar percentage of aluminum (Al) present in the positive electrode active material of the present invention may be 0.7 mol% to 1.4 mol%.

[0118] The present invention can further improve the lifespan of a secondary battery by doping aluminum (Al) before mixing and coating sulfur (S) and boron (B).

[0119] In one aspect, the positive electrode active material may further include a coating oxide containing one or more selected from cobalt (Co), aluminum (Al), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), molybdenum (Mo), iron (Fe), nickel (Ni), barium (Ba), tungsten (W), yttrium (Y), niobium (Nb), and fluorine (F) as a coating material.

[0120] Most preferably, the lifespan of the secondary battery can be further improved by coating cobalt (Co) before mixing and coating sulfur (S) and boron (B).

[0121] As an example, the cobalt (Co) oxide may contain Li p Co q O r 、Co q O r 、and / or may be included in an LCO-like structure.

[0122] On the other hand, the LCO-like structure may be, for example, amorphous or spinel-structured as an intermediate that may exist during the formation of the cobalt (Co) oxide of LiCoO2.

[0123] On the other hand, in one aspect, dry coating can be performed when coating the cobalt (Co).

[0124] In this case, a part of the cobalt (Co) in the coating precursor can be doped into the lattice structure of the primary particles, and a part can exist on the particle surface and at grain boundaries between primary particles in the form of an oxide containing cobalt (Co).

[0125] In one embodiment, the coating region of the present invention may include a coating oxide represented by the following chemical formula 2. [Chemical formula 2] Li p M3 q O r In the above chemical formula 2, M3 is one or more selected from cobalt (Co), sulfur (S), and boron (B), and 0 ≤ p ≤ 10, 0 <q≦8、2≦r≦13である。

[0126] As an example, the coating oxide may be an oxide composed of lithium and an element represented by M3, or an oxide of M3.

[0127] For example, M3 may contain sulfur (S) and boron (B), or it may contain all of cobalt (Co), sulfur (S), and boron (B).

[0128] In one embodiment, the positive electrode active material particles have a specific surface area of ​​0.42 m² as measured by the nitrogen adsorption BET method. 2 / g or more, 0.5m 2 It may be less than / g.

[0129] Since the positive electrode active material particles produced by the manufacturing method of the present invention have a specific surface area within the aforementioned numerical range, their capacity and lifespan performance can be further improved.

[0130] In one aspect, the lithium composite oxide particles relating to the bulk region may be secondary particles formed by the aggregation of primary particles.

[0131] For example, the secondary particles may consist of 2 to 10, 10 to 100, 100 to 1000, 1000 to 10000, or 10000 or more primary particles.

[0132] The primary particles and secondary particles may each independently have a rod-like, elliptical, and / or amorphous shape.

[0133] In one embodiment, the average major axis length of the primary particles may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, 10 μm or less, 5 μm or less, or 3 μm or less.

[0134] In one embodiment, the average aspect ratio (long axis length / short axis length) of the primary particles may be 1.0 or greater, 1.2 or greater, 1.5 or greater, 2.0 or greater, 10.0 or less, 7.0 or less, or 5.0 or less.

[0135] In one embodiment, the secondary particles are spherical, with an average diameter (D 50 ) may be 1 μm or larger, 5 μm or larger, 10 μm or larger, 30 μm or smaller, 20 μm or smaller, or 15 μm or smaller.

[0136] In this invention, the average diameter (D 50 This value represents the particle size at the 50% point of the area cumulative distribution by particle size, and can be measured using laser diffraction.

[0137] Specifically, after dispersing the powder to be measured in a dispersion medium, it can be introduced into a commercially available laser diffraction particle size analyzer. The difference in diffraction patterns due to particle size as the particles pass through the laser beam can then be measured to calculate the particle size distribution.

[0138] In another aspect, the nickel (Ni)-based lithium composite oxide particles may be single particles, and if the single particle consists of one crystallite, it may be in a single crystal form, and the average diameter (D) of the single particle 50 ) can be between 0.1 μm and 30 μm.

[0139] On the other hand, the aforementioned single particles may also exist in contact with each other.

[0140] Next, a method for producing the positive electrode active material particles and positive electrode active material of the present invention will be described.

[0141] The coating content, coating conditions, and manufacturing method of the positive electrode active material particles of the present invention can be controlled by the manufacturing method described below.

[0142] First, a hydroxide precursor or an oxide precursor can be prepared as the positive electrode active material precursor.

[0143] Next, the prepared precursor and lithium-containing compound can be mixed and subjected to a first heat treatment to produce a lithium composite oxide.

[0144] Furthermore, more preferably, a doping element-containing compound can be mixed during the first heat treatment and carried out together. For example, the doping element may be aluminum (Al).

[0145] Furthermore, more preferably, the first heat treatment temperature may be 740°C to 780°C.

[0146] Next, if an additional coating other than sulfur (S) and boron (B) is to be applied, a primary coated lithium composite oxide can be produced by mixing the first heat-treated lithium composite oxide with a compound containing the first coating element and then performing a second heat treatment.

[0147] In this case, the first coating element may more preferably be cobalt (Co).

[0148] Furthermore, more preferably, the cobalt (Co)-containing compound is a solid and can be carried out in a dry coating process.

[0149] Furthermore, more preferably, the second heat treatment temperature may be 680°C to 720°C.

[0150] A coating solution containing sulfur (S) and boron (B) compounds can be manufactured as follows.

[0151] First, a coating solution can be prepared by weighing a sulfur (S)-containing compound and a boron (B)-containing compound and adding them to a solvent.

[0152] Next, the manufactured coating liquid can be sprayed onto the manufactured lithium composite oxide (lithium composite oxide or first coated lithium composite oxide) using a spray method, and then a third heat treatment can be performed to produce a positive electrode active material.

[0153] In this case, for example, the sulfur (S)-containing compound may be a sulfate compound, and the boron (B)-containing compound may be H3BO3.

[0154] In this case, when the ratio of sulfur (S) by weight % (relative to particles) to boron (B) by weight % (relative to particles) added is defined as "S added / B added", the "S added / B added" ratio may be 1.4 or greater, 1.5 or greater, 2.0 or greater, 2.5 or greater, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less.

[0155] In particular, when the ratio of S input to B input is 2.0 ≤ 4.0, the initial charge / discharge capacity performance can be maximized.

[0156] During the production of positive electrode active material particles according to the present invention, the sulfur (S) concentration (ppm) introduced may be 500 ppm to 2000 ppm, 800 ppm to 1600 ppm, and more preferably 1000 ppm to 1400 ppm, based on the positive electrode active material being mixed.

[0157] During the production of positive electrode active material particles according to the present invention, the boron (B) concentration (ppm) introduced may be 100 ppm to 600 ppm, 300 ppm to 500 ppm, and more preferably 400 ppm to 450 ppm, based on the positive electrode active material being mixed.

[0158] In one embodiment, the third heat treatment temperature may be 250°C to 350°C, more preferably 280°C to 320°C.

[0159] The present invention, by mixing and coating sulfur (S) and boron (B) in this manner and controlling the coating content, coating conditions, and manufacturing method, can increase particle crystallinity and further improve battery characteristics compared to dry or wet coating by bringing internal impurities such as sulfur compounds that induce stacking faults onto the surface of the positive electrode active material particles.

[0160] The present invention, by coating a mixture of sulfur (S) and boron (B) in this manner and controlling the coating content, coating conditions, and manufacturing method, converts residual lithium present in the particles, such as LiOH and Li2BO3, into substances such as Li2BO3 and Li2SO4, thereby improving capacity, efficiency, and output characteristics.

[0161] On the other hand, when sulfur (S) and boron (B) coatings are performed after cobalt (Co) coating, more preferably after dry coating, the capacity and lifespan may be improved compared to when cobalt (Co) coating is not performed before sulfur (S) and boron (B) coating.

[0162] A positive electrode according to one aspect of the present invention includes the positive electrode active material.

[0163] Apart from the use of the aforementioned positive electrode active material, the positive electrode has a known structure and can be manufactured according to known manufacturing methods.

[0164] The binder, conductive material, and solvent are not particularly limited, as long as they can be used on the positive electrode current collector of a secondary battery.

[0165] A secondary battery according to one aspect of the present invention includes the positive electrode active material.

[0166] The aforementioned secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and an electrolyte between the positive electrode and the negative electrode, but is not particularly limited as long as it can be used as a secondary battery.

[0167] The following describes embodiments of the present invention in more detail.

[0168] Manufacturing of positive electrode active material <Example 1> (a) Precursor preparation: An aqueous solution of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O mixed in a molar ratio of 91:4.5:4.5 was added to the reactor while stirring, along with NaOH and NH4OH. The reactor temperature was maintained at 45°C, and the precursor synthesis reaction proceeded while N2 gas was introduced into the reactor.

[0169] After the reaction is complete, wash and dehydrate the Ni 0.91 Co 0.045 Mn 0.045 A hydroxide precursor with (OH)2 composition was obtained.

[0170] (b) First heat treatment The hydroxide precursor obtained in step (a) above was mixed with LiOH (Li / Metal molar ratio = 1.00), which is a lithium raw material, and Al(OH)3 so that the Al content was 1.0 mol% based on the metal elements other than lithium in the precursor, to prepare a mixture.

[0171] Next, the furnace in an O2 atmosphere was heated to 760°C for 6 hours, the mixture was heat-treated for 10 hours, and then cooled in the furnace to obtain the primary oxide.

[0172] (c) Second heat treatment A mixture was prepared by mixing the primary oxide obtained in step (b) with Co(OH)2 and LiOH 1.0 mol%, which were weighed to have a Co content of 1.0 mol% based on the metal elements excluding lithium in the primary oxide.

[0173] Next, the furnace in an O2 atmosphere was heated to 700°C for 2 hours, the mixture was heat-treated for 8 hours, and then cooled in the furnace to obtain a secondary oxide.

[0174] (d) Third heat treatment After weighing H3BO3 to the secondary oxide obtained in step (c) above to a concentration of 0.235 wt%, DIW was added to produce a coating solution to a concentration of 7.5 wt% of H3BO3.

[0175] ((NH4)2)SO4 was weighed to a concentration of 0.5 wt% relative to the secondary cathode active material and then added to the coating solution. The prepared coating solution was then mixed with the secondary oxide by spraying it onto the secondary oxide in a controlled quantity.

[0176] The mixture was heated in an O2 atmosphere furnace to 300°C for 1 hour, then heat-treated for 8 hours, and finally cooled in the furnace to obtain a positive electrode active material (average particle size 14 μm).

[0177] <Example 2> The cathode active material was manufactured in the same manner as in Example 1, except that in step (d) of Example 1, ((NH4)2)SO4 was weighed to a concentration of 0.25 wt% relative to the secondary cathode active material and then added to the coating solution.

[0178] <Example 3> The cathode active material was manufactured in the same manner as in Example 1, except that in step (d) of Example 1, ((NH4)2)SO4 was weighed to 0.75 wt% relative to the secondary cathode active material and then added to the coating solution.

[0179] <Comparative Example 1> The positive electrode active material was produced in the same manner as in Example 1, except that H3BO3 and ((NH4)2)SO4 were not added in step (d) of Example 1.

[0180] <Comparative Example 2> The positive electrode active material was manufactured in the same manner as in Example 1, except that ((NH4)2)SO4 was not added to the coating solution in step (d) of Example 1.

[0181] <Comparative Example 3> The cathode active material was produced in the same manner as in Example 1, except that in step (d) of Example 1, only (NH4)2SO4 was added to the DIW without adding H3BO3.

[0182] <Comparative Example 4> The positive electrode active material was produced in the same manner as in Example 1, except that in step (d) of Example 1, H3BO3 was weighed and added to the secondary oxide in an amount of 0.5 wt%.

[0183] <Comparative Example 5> The positive electrode active material was produced in the same manner as in Example 1, except that in step (d) of Example 1, H3BO3 was weighed and added to the secondary oxide in an amount of 1.0 wt%.

[0184] <Comparative Example 6> The positive electrode active material was produced in the same manner as in Example 1, except that in step (d) of Example 1, 0.235 wt% of H3BO3 and 0.5 wt% of ((NH4)2)SO4 were mixed in a dry state with the secondary oxide and then heat-treated.

[0185] <Comparative Example 7> The positive electrode active material was produced in the same manner as in Example 1, except that in step (d) of Example 1, 0.235 wt% of H3BO3 was mixed with the secondary oxide in a dry state and then heat-treated.

[0186] Manufacturing of lithium-ion batteries A cathode slurry was prepared by dispersing 96 wt% of the cathode active material produced according to the above examples and comparative examples, 2 wt% of artificial graphite, and 2 wt% of PVDF binder in 8 g of N-methyl-2-pyrrolidone (NMP).

[0187] The aforementioned positive electrode slurry was uniformly applied to a 15 μm thick aluminum foil and vacuum-dried at 135°C to produce a positive electrode for a lithium secondary battery.

[0188] A coin cell was manufactured using a lithium foil as the counter electrode against the positive electrode, a porous polyethylene membrane (Celgard 2300, thickness: 25 μm) as the separation membrane, and an electrolyte containing ethylene carbonate and ethyl methyl carbonate mixed in a volume ratio of 3:7 with LiPF6 present at a concentration of 1.15 M.

[0189] <Experimental Example 1> SEM-EDS Figure 1 shows SEM images of the particle surface according to the above examples and comparative examples.

[0190] Figure 1 shows that the coating is applied to only a portion of the particle surface.

[0191] Figure 2 shows SEM-EDS images of the cross-section of positive electrode active material particles depending on the manufacturing method.

[0192] As shown in Figure 2, when boron (B) and sulfur (S) are semi-wet spray coated, compared to when no spraying is performed and when only boron (B) is semi-wet spray coated, it can be confirmed that the impurity sulfur (S) present inside the particles due to the precursor comes relatively to the surface of the particles and forms a coated area.

[0193] Figure 3 shows SEM-EDS images of the surface of cathode active material particles depending on the manufacturing method.

[0194] As shown in Figure 3, when boron (B) and sulfur (S) are semi-wet spray coated, compared to when boron (B) and sulfur (S) are dry coated, it can be confirmed that impurity sulfur (S) present inside the particles due to the precursor comes relatively to the surface of the particles and forms a coated area.

[0195] Figure 4 shows an SEM-EDS image of a particle cross-section according to Example 1 of the present invention.

[0196] Figure 4 shows that a cobalt (Co) coating layer is formed on the particle surface.

[0197] <Experimental Example 2> Analysis of Residual Lithium Content The results of the analysis of the residual lithium content of the positive electrode active material in the examples and comparative examples of the present invention are shown in Table 1 below.

[0198] In this invention, residual lithium is measured by the amount of 0.1 M HCl used until the pH becomes 4 by pH titration.

[0199] First, add 5g of oxide to 100ml of DIW, stir for 15 minutes, and then filter.

[0200] Next, 50 ml of the filtered solution was taken, 0.1 M HCl was added to it, and the amount of HCl consumed due to the pH change was measured to determine Q1 and Q2. The residual LiOH and Li2BO3 were then calculated according to the following formula. M1= 23.94 (LiOH molecular weight) M2= 73.89 (Li2BO3 molecular weight) LiOH(ppm) = {((Q1-Q2) * M1 * HCl concentration * DIW(g)) / (solution(g) * powder(g))} * 10,000 Li2BO3(ppm) = {(2 * Q2 * M2 / 2 * HCl concentration * DIW(g)) / (solution(g) * powder(g))} * 10,000

[0201] According to Table 1 below, in Examples 1 to 3, where both boron (B) and sulfur (S) were added, the residual lithium content was reduced compared to Comparative Examples 1 to 3, where neither was added. [Table 1]

[0202] According to Table 1 above, it can be confirmed that when both boron (B) and sulfur (S) are coated, the residual lithium present in the particles is reduced compared to when neither is coated or when only boron (B) or sulfur (S) is coated.

[0203] <Experimental Example 3> ICP Content Analysis The results of the content analysis of the positive electrode active material by ICP analysis in the above examples and comparative examples are shown in Table 2 below.

[0204] In this invention, ICP analysis was performed by dissolving the positive electrode active material produced according to the above examples and comparative examples in hydrochloric acid, nitric acid, and hydrofluoric acid solvents to prepare a sample solution. Then, the sample solution was diluted 2000 times and placed in an ICP-OES (Avio 500, PerkinElmer) to measure the weight of each element contained in the positive electrode active material relative to the total weight of the positive electrode active material. [Table 2]

[0205] <Experimental Example 4> BET Specific Surface Area Analysis The BET specific surface area analysis results of the positive electrode active materials in the above examples and comparative examples are shown in Table 3 below.

[0206] In this invention, the BET specific surface area was calculated from the amount of nitrogen gas adsorbed under liquid nitrogen temperature (77K) using a gas adsorption specific surface area measuring device (MicrotracBEL, BELSORP-mini II) after pre-treating 5g of positive electrode active material at 200°C for 3 hours. [Table 3]

[0207] <Experimental Example 5> Battery Characteristic Analysis The results of the battery characteristic analysis for lithium secondary batteries based on the above examples and comparative examples are shown in Table 4 below.

[0208] In this invention, initial charge / discharge capacity was measured using an electrochemical analyzer (Toyo, Toscat-3100) through charge / discharge experiments applied at 25°C, a voltage range of 2.7V to 4.3V, and a discharge rate of 0.05C. The initial charge capacity and initial discharge capacity were measured, and the initial reversible efficiency was calculated.

[0209] Furthermore, C-rate measurements were performed using an electrochemical analyzer (Toyo, Toscat-3100) through charge-discharge experiments applied at 25°C, a voltage range of 2.5V to 4.25V, and discharge rates of 0.1C to 1.0C, thereby measuring the output efficiency (C-rate) at 1.0C / 0.1C. [Table 4]

[0210] According to Table 4 above, it can be confirmed that Examples 1 to 3 show improvements in capacity, efficiency, and C-rate performance compared to Comparative Examples 1 to 5.

Claims

1. The positive electrode active material particles contain sulfur (S) and boron (B), and when the ratio of sulfur (S) concentration (ppm) to boron (B) concentration (ppm) in the positive electrode active material particles is S / B, then 8 ≤ S / B ≤ 20.

2. The positive electrode active material particles according to claim 1, wherein 10 ≤ S / B ≤ 15.

3. The positive electrode active material particles according to claim 1, wherein the boron (B) concentration (ppm) contained in the positive electrode active material particles is 100 ppm to 600 ppm.

4. The positive electrode active material particles according to claim 1, wherein the sulfur (S) concentration (ppm) contained in the positive electrode active material particles is 3,200 ppm to 5,000 ppm.

5. The positive electrode active material particle according to claim 1, wherein the positive electrode active material particle comprises a bulk region and a coating region, the coating region comprises sulfur (S) and boron (B), and the sulfur (S) and boron (B) contained in the coating region are present on a portion of the surface of the bulk region.

6. The positive electrode active material according to claim 5, wherein the sulfur (S) concentration (ppm) contained within the coating region is greater than the sulfur (S) concentration (ppm) contained in the positive electrode active material particles.

7. In claim 1, the positive electrode active material particles are Li 2 BO 3 Positive electrode active material particles containing [the specified element].

8. In claim 1, the positive electrode active material particles are Li 2 SO 4 Positive electrode active material particles containing [the specified element].

9. The positive electrode active material particle according to claim 1, further comprising a coating oxide containing one or more selected from cobalt (Co), aluminum (Al), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), molybdenum (Mo), iron (Fe), nickel (Ni), barium (Ba), tungsten (W), yttrium (Y), niobium (Nb), and fluorine (F).

10. In claim 1, the specific surface area measured by the nitrogen adsorption BET method is 0.42 m². 2 / g or 0.5 m 2 Positive electrode active material particles, which are / g.

11. A method for producing positive electrode active material particles according to claim 1, comprising the steps of: producing a lithium composite oxide by mixing and heat-treating a positive electrode active material precursor and a lithium-containing compound; producing a coating solution containing a sulfur (S)-containing compound and a boron (B)-containing compound; and spraying and heat-treating the produced coating solution onto the produced lithium composite oxide.

12. A method for producing positive electrode active material particles, according to claim 11, wherein when the ratio of sulfur (S) concentration (ppm) to boron (B) concentration (ppm) contained in the coating liquid is defined as "S input / B input", the ratio is 1.4 ≤ S input / B input ≤ 5.

0.

13. A method for producing positive electrode active material particles, according to claim 11, wherein the heat treatment temperature in the step of spraying the manufactured coating liquid onto the manufactured lithium composite oxide and heat treating it is 250°C to 350°C.

14. A method for producing positive electrode active material particles, further comprising the step of coating the produced lithium composite oxide with cobalt (Co) after the step of producing the lithium composite oxide and before the step of spraying the produced coating solution onto the produced lithium composite oxide and heat-treating it; according to claim 11.

15. A positive electrode active material comprising positive electrode active material particles according to claim 1.

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