Positive electrode active material, positive electrode containing the same, and lithium secondary battery

Abstract

The present invention relates to a positive electrode active material containing a lithium manganese-based oxyhalide having a composition represented by the following [Chemical Formula 1] and including a disordered rock-salt structure. [Chemical formula 1] Li 0.5+a Mn b M c O d X e In the above [Chemical Formula 1], M is at least one selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb and Ru, preferably Ti; X is a halogen element, preferably F;

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0050421 dated April 22, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery, and more particularly to a manganese-based positive electrode active material having a disordered rock salt structure, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0003] Recently, interest in energy storage technologies has been growing, and as applications expand to include mobile phones, camcorders and laptop computers, and even electric vehicles, efforts to research and develop electrochemical devices are becoming increasingly concrete.

[0004] Among electrochemical elements, there is growing interest in the development of rechargeable secondary batteries, and lithium-ion batteries, developed in the early 1990s, have attracted particular attention due to their advantages of high operating voltage and remarkably high energy density.

[0005] Lithium secondary batteries are generally manufactured by interposing a separator between a positive electrode containing a positive electrode active material made of a transition metal oxide containing lithium and a negative electrode containing a negative electrode active material capable of storing lithium ions, inserting the electrode assembly into a battery case, injecting a non-aqueous electrolyte that acts as a medium for transferring lithium ions, and then sealing it. The non-aqueous electrolyte generally consists of a lithium salt and an organic solvent capable of dissolving the lithium salt.

[0006] Recently, with the increasing demand for high-energy-density secondary batteries, such as those for electric vehicles, lithium-composite transition metal oxides, such as lithium nickel-cobalt-manganese oxide and lithium nickel-cobalt-manganese-aluminum oxide, which have a high energy density and layered structure, are mainly used as positive electrode active materials. However, as the demand for secondary batteries has surged, the prices of transition metals such as nickel and cobalt have risen, reducing their price competitiveness. Furthermore, the energy density increase of secondary batteries using existing lithium-composite transition metal oxides has reached its limit. Therefore, attempts are being made to develop Mn-based positive electrode active materials that offer superior price competitiveness.

[0007] Recently, manganese-based cathode active materials that are being actively researched include perlithitated manganese-rich cathode active materials in which Li2MnO3 rock salt structure and LiMO2 layered structure are mixed (e.g., Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O2) and positive electrode active materials having a partial spinel-disordered rock salt structure (e.g., Li 1.68 Mn 1.6 O 3.7 F 0.3 These include the following. In the case of perlithitated manganese-rich cathode active materials, while they have excellent capacity characteristics, their use is limited by their low rate-limiting characteristics due to their structural features, and they have the problem of reduced lifetime characteristics due to irreversible oxygen-redox reactions. In the case of cathode active materials with a partial spinel-disordered rock salt structure, while they have excellent rate characteristics and capacity characteristics, they still exhibit the problem of low lifetime characteristics. [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to solve the above-mentioned problems and provides a novel cathode active material that is based on relatively inexpensive manganese and contains a disordered rock salt structure, thereby exhibiting excellent capacity characteristics, rate characteristics, and lifetime characteristics.

Means for Solving the Problem

[0009] On one side, the present invention provides a positive electrode active material containing a lithium manganese-based oxyhalide having a composition represented by the following [Chemical Formula 1] and including a disordered rock-salt structure. [Chemical Formula 1] Li 0.5+a Mn b M c O d X e In the above [Chemical Formula 1], M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, preferably Ti, X is a halogen element, preferably F, 0 < a ≤ 0.7, 0.5 ≤ b < 1, 0 < c ≤ b / 2, 1.5 ≤ d ≤ 1.9, 0.1 ≤ e ≤ 0.5, and d + e ≤ 2.

[0010] The atomic ratio of cation elements to anion elements in the lithium manganese-based oxyhalide can be 0.75:1 to 1:1.

[0011] The primary particle size of the lithium manganese-based oxyhalide can be 50 nm to 300 nm.

[0012] According to one embodiment, the lithium manganese-based oxyhalide can have a composition represented by the following [Chemical Formula 1-1]. [Chemical Formula 1-1] Li 1+a1 Mn b1 M c1 O 2-e1 X e1 In the above [Chemical Formula 1-1], M is one or more elements selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, preferably Ti, and X is a halogen element, preferably F, and 0 <a1≦0.2、0.5≦b1<1、0<c1≦b1 / 2、0.1≦e1≦0.5である。

[0013] The lithium manganese-based oxyhalide represented by [Chemical Formula 1-1] above may have a single-phase structure with a disordered rock salt structure.

[0014] According to other embodiments, the lithium manganese-based oxyhalide may have a composition represented by the following [Chemical Formula 1-2]. [Chemical formula 1-2] Li 0.5+a2 Mn b2 M c2 O 2-e2 X e2 In the above [Chemical Formula 1-2], M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, preferably Ti, and X is a halogen element, preferably F, and 0 <a2<0.5、0.5≦b2<1、0<c2≦b2 / 2、0.1≦e2≦0.5である。

[0015] The lithium manganese-based oxyhalide having the composition represented by [Chemical Formula 1-2] above can have a multi-phase structure in which disordered rock salt structure, layered rock salt structure and spinel structure are mixed, and the proportion of the spinel phase in the lithium manganese-based oxide can be 75% or less, preferably 25% to 75%.

[0016] Furthermore, the lithium manganese-based oxyhalide represented by [Chemical Formula 1-2] has a (111) plane peak intensity I(111). S (400) plane peak intensity I(400) R Ratio I(400) R / I(111) S It is preferable that this value is 1 or greater.

[0017] In other aspects, the present invention provides a positive electrode containing the positive electrode active material according to the present invention and a lithium secondary battery containing the same. [Effects of the Invention]

[0018] The positive electrode active material according to the present invention contains a disordered rock salt structure and includes a lithium manganese-based oxyhalide doped with element M (wherein M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru). When doping a lithium manganese-based oxyhalide having a disordered rock salt structure with element M as in the present invention, the structural properties are controlled, and Mn 3+ The Jahn-Teller distortion caused by this process is mitigated, improving the reversibility of the oxygen redox reaction during charging and discharging, and significantly improving the cycle characteristics.

[0019] Furthermore, lithium manganese-based oxyhalides, in which some of the oxygen is replaced by halogens, contain large halogen elements with low negative charge (F - The presence of ) can lower the oxidation state of the transition metal, and by increasing the amount of stable transition metal oxidation / reduction, it is possible to achieve superior rate characteristics and cycle characteristics compared to conventional perlithitated manganese oxides. [Brief explanation of the drawing]

[0020] [Figure 1] This is an SEM image of the lithium manganese-based oxyhalide synthesized according to Example 1. [Figure 2] This is an SEM image of the lithium manganese-based oxyhalide synthesized by Example 2. [Figure 3] This is an SEM image of lithium manganese-based oxyhalides synthesized by the comparative example. [Figure 4] This is an SEM image of the lithium manganese-based oxyhalide synthesized by Example 3. [Figure 5]This is an SEM image of the lithium manganese-based oxyhalide synthesized according to Example 4. [Figure 6] This graph shows the life characteristics of lithium secondary batteries to which the lithium manganese-based oxyhalides synthesized in Examples 1 and 2 were applied. [Figure 7] This graph shows the life characteristics of lithium secondary batteries to which the lithium manganese-based oxyhalides synthesized in Comparative Example and Examples 3-4 were applied. [Figure 8] (A) is an HR-TEM (High-Resolution Transmission Electron Microscopy) image of the lithium manganese-based oxyhalide synthesized according to Example 4, and (B) is the result of SAED pattern measurement of the lithium manganese-based oxyhalide synthesized according to Example 4. [Figure 9] This is the XRD data for lithium manganese-based oxyhalides synthesized by the comparative example. [Figure 10] This is the XRD data for the lithium manganese-based oxyhalide synthesized by Example 3. [Figure 11] This is the XRD data for the lithium manganese-based oxyhalide synthesized according to Example 4. [Modes for carrying out the invention]

[0021] The present invention will be described in more detail below.

[0022] positive electrode active material The positive electrode active material according to the present invention has a disordered rock-salt structure and contains a lithium manganese-based oxyhalide doped with an M element (where M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru).

[0023] Conventional positive electrode active materials generally have a crystalline structure consisting of an ordered layered structure or an ordered spinel structure, in which the lithium layer and the transition metal layer are separated. However, such conventional positive electrode active materials require the use of high-grade transition metals such as nickel or cobalt, and when lithium desorption occurs in large amounts in the lithium layer, phase transition occurs, which limits the improvement of energy density. In contrast, positive electrode active materials having a disordered rock salt structure, as in the present invention, have the advantage of minimizing the loss of conductive networks due to increased positive electrode active material volume, as there is no other lithium layer, thus reducing the occurrence of phase transition due to lithium desorption. Furthermore, there is less volume change due to charging and discharging.

[0024] Specifically, the lithium manganese-based oxyhalide according to the present invention may have a composition represented by the following [Chemical Formula 1].

[0025] [Chemical formula 1] Li 0.5+a Mn b M c O d X e

[0026] In the above [Chemical Formula 1], M can be one or more elements selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, and is preferably Ti. When the element M is doped into a lithium manganese-based oxyhalide having a disordered rock salt structure, as in the present invention, structural control can be achieved by Mn 3+ This reduces the Jahn-Teller distortion, improving the reversibility of the oxygen redox reaction during charging and discharging, and resulting in improved lifespan characteristics.

[0027] On the one hand, X can be a halogen element, preferably F, Cl, Br, and / or I, more preferably F. When a part of oxygen is substituted by a halogen, the presence of a halogen element with a higher electronegativity than oxygen enables charge balance between cations and anions even when lithium is added in excess of stoichiometry. Compared with conventional over-lithiated manganese-based oxides, excellent rate characteristics and cycle characteristics can be achieved.

[0028] The 0.5 + a represents the atomic ratio of Li in the lithium manganese-based oxyhalide, and can be 0 < a ≤ 0.7, 0.02 ≤ a ≤ 0.7, 0.02 ≤ a ≤ 0.5, 0 < a ≤ 0.2, 0.02 ≤ a ≤ 0.2, or 0.2 ≤ a ≤ 0.7. The positive electrode active material of the present invention preferably contains Li in excess of the stoichiometric ratio. When Li is contained in excess of the stoichiometric ratio, the high-capacity characteristics are improved, and based on the four faces of the tetrahedral site, the improvement effect of the rate characteristics is further excellent due to the increase in the amount of lithium with 0 (0-TM) or 1 (1-TM) transition metal. However, since lithium excess may reduce the electronic conductivity of the material and thus reduce the overall conduction characteristics, the atomic ratio of Li in the lithium manganese-based oxyhalide is preferably 1.2 or less.

[0029] The b represents the atomic ratio of Mn in the lithium manganese-based oxyhalide, and can be 0.5 ≤ b < 1, 0.5 ≤ b ≤ 0.9, or 0.6 ≤ b ≤ 0.8. When the atomic ratio of manganese satisfies the above range, excellent capacity characteristics can be achieved.

[0030] The c represents the atomic ratio of the doping element M in the lithium manganese-based oxyhalide, and can be 0 < c ≤ b / 2, 0.05 ≤ c ≤ b / 2, or 0.1 ≤ c ≤ b / 2. When the atomic ratio of the doping element M satisfies the above range, a cathode active material with excellent capacity characteristics, rate characteristics, and life characteristics can be realized. If the content of the doping element M increases too much, the capacity and rate characteristics of the cathode active material may decrease. If the content of the doping element M is too small, the improvement effect on the life characteristics is not significant.

[0031] The d represents the atomic ratio of oxygen in the lithium manganese-based oxyhalide, and can be 1.5 ≤ d ≤ 1.9, 1.7 ≤ d ≤ 1.9, 1.5 ≤ d ≤ 1.7, or 1.75 ≤ d ≤ 1.85.

[0032] The e represents the atomic ratio of the halogen element X in the lithium manganese-based oxyhalide, and can be 0.1 ≤ e ≤ 0.5, 0.1 ≤ e ≤ 0.4, or 0.1 ≤ e ≤ 0.3. When the atomic ratio of the halogen element satisfies the above range, the charge balance between cations and anions can be properly maintained, and excellent rate characteristics and cycle characteristics can be realized.

[0033] On the other hand, in Chemical Formula 1, d + e ≤ 2 can be satisfied, and preferably, d + e can be 2.

[0034] On the other hand, in the lithium manganese-based oxyhalide, the atomic ratio of the cation elements (i.e., Li, Mn, and M elements) to the anion elements (i.e., oxygen and halogen elements) can be 0.75:1 to 1:1. When the atomic ratio of the cation elements to the anion atoms satisfies the above range, a disordered rock salt structure can be smoothly formed.

[0035] On the other hand, the lithium manganese-based oxyhalide can be in the form of primary particles and / or secondary particles formed by the aggregation of multiple primary particles, where the primary particle size can be 50 nm to 300 nm, preferably 50 nm to 250 nm. When the primary particle size satisfies this range, the surface-to-bulk ratio increases, which has the effect of eliminating the drawbacks of materials having low ionic conductivity.

[0036] According to one embodiment, the lithium manganese-based oxyhalide may have a composition represented by the following [Chemical Formula 1-1].

[0037] [Chemical formula 1-1] Li 1+a1 Mn b1 M c1 O 2-e1 X e1

[0038] In the above [Chemical Formula 1-1], M and X are as defined in [Chemical Formula 1]. That is, M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, preferably Ti, and X can be a halogen element, preferably F.

[0039] The above 1+a1 represents the atomic ratio of Li in the lithium manganese-based oxyhalide, and 0 <a1≦0.2、0.02≦a1<0.2、または0.02≦a1≦0.15であることができる。

[0040] The b1 in question represents the atomic ratio of Mn within the lithium manganese-based oxyhalide, and can be 0.5 ≤ b1 < 1, 0.6 ≤ b1 < 1, or 0.6 ≤ b1 ≤ 0.9.

[0041] The aforementioned c1 represents the atomic ratio of the doping element M in the lithium manganese-based oxyhalide, and 0 <c1≦b1 / 2、0.05≦c1≦b1 / 2、または0.1≦c1≦b1 / 2であることができる。

[0042] The aforementioned e1 represents the atomic ratio of halogen element X in the lithium manganese-based oxyhalide, and can be 0.1 ≤ e1 ≤ 0.5, 0.1 ≤ e1 ≤ 0.4, or 0.1 ≤ e1 ≤ 0.25.

[0043] On the other hand, the lithium manganese-based oxyhalide represented by [Chemical Formula 1-1] can have a disordered rock salt structure phase, and preferably consists of a single-phase disordered rock salt structure. Conventional perlithitated manganese oxides require a large amount of lithium excess for smooth lithium movement within the structure, which conversely forms a large amount of transition metal-deficient oxide. Transition metals are essential to eliminate instability within the structure that occurs during charging (delithiation reaction) in the positive electrode, but such transition metal-deficient oxides (lithium-excess oxides) increase structural instability. Therefore, in the present invention, the lithium excess amount (a1) is reduced to 0.2 at% or less to minimize the transition metal deficiency phenomenon in the positive electrode, thereby ensuring structural safety, and structural stability is further improved by doping with element M. In this way, by using manganese-based oxyhalides with low lithium excess and doping, stability within the positive electrode structure is achieved, structural changes in the positive electrode active material are suppressed during charging and discharging, and the effect of significantly improving the life characteristics can be obtained.

[0044] According to other embodiments, the lithium manganese-based oxyhalide may have a composition represented by the following [Chemical Formula 1-2].

[0045] [Chemical formula 1-2] Li 0.5+a2 Mn b2 M c2 O 2-e2 X e2

[0046] In the above [Chemical Formula 1-2], M and X are as defined in [Chemical Formula 1]. That is, M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, preferably Ti, and X can be a halogen element, preferably F.

[0047] The aforementioned 0.5+a2 represents the atomic ratio of Li within the lithium manganese-based oxyhalide, and 0 <a2<0.5、0.1≦a2<0.5、または0.2≦a2≦0.4であることができる。

[0048] The b2 parameter represents the atomic ratio of Mn within the lithium manganese-based oxyhalide, and can be 0.5 ≤ b2 < 1, 0.6 ≤ b2 < 1, or 0.65 ≤ b2 ≤ 0.95.

[0049] The aforementioned c2 represents the atomic ratio of the doping element M in the lithium manganese-based oxyhalide, and 0 <c2≦b2 / 2、0.05≦c2≦b2 / 2、または0.1≦c2≦b2 / 2であることができる。

[0050] The aforementioned e2 represents the atomic ratio of halogen element X in the lithium manganese-based oxyhalide and can be 0.1 ≤ e2 ≤ 0.5, 0.1 ≤ e2 ≤ 0.4, or 0.1 ≤ e2 ≤ 0.25.

[0051] Lithium manganese-based oxyhalides having the composition represented by the above [Chemical Formula 1-2] can have a multi-phase structure in which disordered rock salt structure, layered rock salt structure, and spinel structure are mixed.

[0052] In disordered rock-salt structures, transition metals and lithium are disorderly dispersed at the 16c and 16d sites of octahedra. Lithium movement within the structure is limited to when there are zero (0-TM) or one (1-TM) transition metals on each of the four faces of a tetrahedral site, resulting in typically low rate characteristics. In contrast, in ordered spinel structures, transition metals like manganese are all located at the 16d sites of octahedra, while lithium is located at the 8a sites of tetrahedra. This creates an 0-TM Li environment where no transition metals are present on any of the faces of the tetrahedral sites, facilitating lithium diffusion. Furthermore, the structure forms a three-dimensional lithium network, resulting in high rate characteristics. Therefore, as described above, when a multiphase structure is present in which disordered rock salt structures and spinel structures are mixed, an improvement in rate characteristics can be obtained compared to when it consists only of a single phase of disordered rock salt structures.

[0053] Here, the proportion of the spinel phase in the lithium manganese oxide can be 75% or less, preferably 25% to 75%. When the proportion of the spinel phase satisfies the above range and the proportion of the rock salt structure increases, structural changes in the positive electrode active material during charging and discharging are suppressed, and the effect of significantly improving the lifespan characteristics can be obtained.

[0054] Furthermore, in the XRD data of the lithium manganese-based oxyhalide represented by [Chemical Formula 1-2] above, the (111) plane peak intensity I(111) S (400) plane peak intensity I(400) R Ratio I(400) R / I(111) S It can be 1 or more, preferably 1 to 2, and more preferably 1 to 1.5. I(400) R / I(111) S When the above range is met, the improvement effect on lifespan characteristics is excellent.

[0055] On the other hand, the lithium manganese-based oxyhalide having the disordered rock salt structure can be synthesized by mechanochemically mixing a lithium source, a manganese source, a halogen source, and a doping element M source. For example, the lithium manganese-based oxyhalide according to the present invention can be produced by introducing a lithium source, a manganese source, a halogen source, and a doping element M source into a high-energy ball mill apparatus and then mixing them using a ball-mill method.

[0056] For example, Li2O, Li2O2, Li2MnO3, or a combination thereof can be used as the lithium source, and for example, Mn2O3, MnO2, Li2MnO3, or a combination thereof can be used as the manganese source, but are not limited thereto. For example, LiF, MnF2, or a combination thereof can be used as the halogen source, and for example, an oxide of element M such as TiO2 can be used as the doping element M source, but are not limited thereto.

[0057] On the other hand, the source can be mixed in an amount that satisfies the atomic ratio of Li, Mn, M, and O in the lithium manganese-based oxyhalide to be ultimately produced.

[0058] Furthermore, the ball-mill mixing can be carried out for 25 to 50 hours at a stirring speed of 300 to 600 rpm, preferably 400 to 500 rpm, and can be done by adding two types of stainless steel balls of different sizes.

[0059] positive electrode Next, the positive electrode according to the present invention will be described.

[0060] The positive electrode according to the present invention includes a positive electrode active material layer containing the positive electrode active material according to the present invention. Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and containing the positive electrode active material.

[0061] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector can usually have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to increase the adhesion strength of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric.

[0062] Furthermore, the positive electrode active material layer may include a conductive material and a binder in addition to the positive electrode active material described above.

[0063] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material can usually be contained in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0064] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0065] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode. For example, the positive electrode can be manufactured by mixing a positive electrode active material, a binder, and / or a conductive material in a solvent to produce a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling it. Here, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0066] The solvent can be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more can be used. The amount of solvent used should be such that it dissolves or disperses the positive electrode active material, conductive material, and binder, and has a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode, taking into consideration the coating thickness of the slurry and the manufacturing yield.

[0067] Alternatively, the positive electrode can be manufactured by casting the positive electrode slurry onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0068] Lithium-ion battery Next, the lithium secondary battery according to the present invention will be described.

[0069] The lithium secondary battery of the present invention includes the positive electrode according to the present invention. Specifically, the lithium secondary battery includes a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. The lithium secondary battery may further optionally include a battery container for housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0070] In the lithium secondary battery described above, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0071] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0072] The negative electrode active material layer selectively includes a binder and a conductive material together with the negative electrode active material.

[0073] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides that can be doped and dedoped with lithium; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and one or more mixtures of these can be used.

[0074] Furthermore, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Typical low-crystallinity carbons include soft carbon and hard carbon, while typical high-crystallinity carbons include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0075] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material can usually be contained in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0076] The binder plays a role in improving adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0077] The negative electrode active material layer can also be manufactured, for example, by applying a negative electrode slurry containing a negative electrode active material and selectively a binder and conductive material onto a negative electrode current collector and drying it, or by casting the negative electrode slurry onto another support, peeling it off this support, and then laminating the resulting film onto the negative electrode current collector.

[0078] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent moisture-absorbing capacity for the electrolyte are particularly preferred. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and can be selectively used as single-layer or multi-layer structures.

[0079] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0080] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0081] The organic solvent can be used without particular limitations as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group, which can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0082] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, more preferably 0.1 to 3.0 M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance due to having appropriate conductivity and viscosity, and lithium ions can move effectively.

[0083] In addition to the electrolyte components, the electrolyte may further contain additives for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. For example, the additives may be, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcoholamine, cyclic ether, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, either alone or in combination. The additives may be present in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, relative to the total weight of the electrolyte.

[0084] As described above, lithium secondary batteries containing the positive electrode active material according to the present invention exhibit excellent discharge capacity, output characteristics, and capacity retention rate stably, making them useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0085] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0086] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0087] Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0088] Example 1 In the PM200 high-energy equipment, Li2O, Li2O2, MnO, MnF2, and TiO2 were added in a weight ratio of 0.0510:0.2050:0.6118:0.1012:0.0432. Then, with 10 5mm balls and 5 10mm balls of stainless steel (based on a 1g batch) added, dry milling was performed at 450 rpm for 33 hours. 1.05 Mn 0.90 Ti 0.05 O 1.8 F 0.2 They were synthesized.

[0089] Synthesized Li 1.05 Mn 0.90 Ti 0.05 O 1.8 F 0.2 A differential scanning electron microscope image of the powder is shown in Figure 1. The synthesized Li shown in Figure 1. 1.05 Mn 0.90 Ti 0.05 O 1.8F 0.2 It can be confirmed that this is a secondary particle morphology in which primary particles of a size of 50 nm to 300 nm are aggregated.

[0090] Example 2 In the PM200 high-energy equipment, Li2O, Li2O2, MnO, MnF2, and TiO2 were added in a weight ratio of 0.0999:0.1302:0.5117:0.1026:0.1665. Then, with 10 5mm stainless steel balls and 5 10mm stainless steel balls added in a 1g batch, dry milling was performed at 450 rpm for 33 hours. 1.05 Mn 0.76 Ti 0.19 O 1.8 F 0.2 They were synthesized.

[0091] Synthesized Li 1.05 Mn 0.76 Ti 0.19 O 1.8 F 0.2 A differential scanning electron microscope image of the powder is shown in Figure 2. Refer to Figure 2 for synthesized Li 1.05 Mn 0.76 Ti 0.19 O 1.8 F 0.2 It can be confirmed that this is a secondary particle morphology in which primary particles of a size of 50 nm to 300 nm are aggregated.

[0092] Comparative Example In the PM200 high-energy equipment, Li2MnO3, Mn2O3, MnO2, and MnF2 were added in a weight ratio of 0.6029:0.2803:0.0392:0.0856, and then, with 10 5mm stainless steel balls and 5 10mm stainless steel balls added in a 1g batch, dry milling was performed at 450rpm for 33 hours. 0.89 Mn 0.80 O 1.85 F 0.15 They were synthesized.

[0093] Synthesized Li 0.89 Mn 0.80 O1.85 F 0.15 The differential scanning electron microscope image of the powder is shown in FIG. 3. Referring to FIG. 3, the synthesized Li 0.89 Mn 0.80 O 1.85 F 0.15 can be confirmed to be in the form of secondary particles aggregated from primary particles with a size of 50 nm to 300 nm.

[0094] Example 3 Into the PM200 high energy equipment, Li2MnO3, Mn2O3, MnO2, MnF2 and TiO2 were charged at a weight ratio of 0.6068:0.0394:0.2023:0.0861:0.0736. Then, 10 5-mm balls and 5 10-mm balls made of stainless steel based on a 1-g batch were added, and dry milling was carried out at 450 rpm for 33 hours to synthesize Li 0.89 Mn 0.725 Ti 0.075 O 1.85 F 0.15 .

[0095] The synthesized Li 0.89 Mn 0.725 Ti 0.075 O 1.85 F 0.15 The differential scanning electron microscope image of the powder is shown in FIG. 4. Referring to FIG. 4, the synthesized Li 0.89 Mn 0.725 Ti 0.075 O 1.85 F 0.15 can be confirmed to be in the form of secondary particles aggregated from primary particles with a size of 50 nm to 300 nm.

[0096] Example 4 Into the PM200 high energy equipment, Li2MnO3, Mn2O3, MnO2, MnF2 and TiO2 were charged at a weight ratio of 0.6107:0.0397:0.1232:0.0867:0.0148. Then, 10 5-mm balls and 5 10-mm balls made of stainless steel based on a 1-g batch were added, and dry milling was carried out at 450 rpm for 33 hours to synthesize Li 0.89 Mn0.65 Ti 0.15 O 1.85 F 0.15 They manufactured it.

[0097] Synthesized Li 0.89 Mn 0.65 Ti 0.15 O 1.85 F 0.15 A differential scanning electron microscope image of the powder is shown in Figure 5. Refer to Figure 5 for the synthesized Li 0.89 Mn 0.65 Ti 0.15 O 1.85 F 0.15 It can be confirmed that this is a secondary particle morphology in which primary particles of a size of 50 nm to 300 nm are aggregated.

[0098] Experimental Example 1: Evaluation of Lifetime Characteristics In a FRISTCH Premium Line 7 facility, lithium manganese-based oxyhalides produced in Examples 1-4 and Comparative Examples were added to SUPER P in a weight ratio of 7:2. The mixture was then mixed at 300 rpm for 30 minutes, and SUPER P was coated onto the surface of the lithium manganese-based oxyhalides to produce the cathode active material.

[0099] The manufactured positive electrode active material, conductive material (SUPER P), and binder (PVDF 5120) were mixed in N-methylpyrrolidone (NMP) in a weight ratio of 7:2:1 to produce a positive electrode mixture. This mixture was then applied to an aluminum current collector, dried, and rolled to produce a positive electrode.

[0100] The negative electrode active material used was a lithium metal foil with a thickness of 0.2 mm.

[0101] An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes produced as described above. After inserting the electrode assembly into a battery case, an electrolyte was injected to produce a lithium secondary battery. The electrolyte used was a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 volume ratio, in which LiPF6 was dissolved at a concentration of 1 M.

[0102] For each lithium secondary battery manufactured as described above, the life characteristics were evaluated by measuring the discharge capacity while performing 30 or 50 charge-discharge cycles. One cycle consisted of charging in CC-CV mode at 25°C until the voltage reached 4.8V at 0.1C, maintaining CV mode until the charging current was 0.05C or less, and then discharging to 1.5V at a constant current of 0.1C. The measurement results are shown in Figures 6 and 7.

[0103] Figure 6 is a graph showing the life characteristics of lithium secondary batteries to which lithium manganese-based oxyhalides synthesized in Examples 1-2 were applied, and Figure 7 is a graph showing the life characteristics of lithium secondary batteries to which lithium manganese-based oxyhalides synthesized in Comparative Examples and Examples 3-4 were applied.

[0104] As shown in Figures 6 and 7, lithium secondary batteries using Ti-doped lithium manganese-based oxyhalides in Examples 1-4 exhibit superior lifespan characteristics compared to lithium secondary batteries using undoped lithium manganese-based oxyhalides in the Comparative Example.

[0105] Experimental Example 2 The crystal structure of the lithium manganese-based oxyhalide synthesized in Example 4 was determined by HR-TEM (High-Resolution Transmission Electron Microscopy) analysis and SAED (Specific Area Electron Diffraction) analysis.

[0106] The measurement results are shown in Figure 8. Figure 8(A) is an HR-TEM (High-Resolution Transmission Electron Microscopy) image of the lithium manganese-based oxyhalide synthesized in Example 4, and Figure 8(B) is the result of the SAED pattern measurement of the lithium manganese-based oxyhalide synthesized in Example 4.

[0107] Referring to Figure 8, it can be confirmed that the lithium manganese-based oxyhalide of Example 4 has a multi-phase structure in which disordered rock salt structure (DRX), layered rock salt structure (Layered), and spinel structure (Spinel) are present.

[0108] Experimental Example 3 The X-ray diffraction (XRD) patterns of the lithium manganese-based oxyhalide powders synthesized by the Comparative Example, Example 3, and Example 4 were measured and are shown in Figures 9 to 11. Figure 9 shows the XRD data for the Comparative Example, Figure 10 shows the XRD data for Example 3, and Figure 11 shows the XRD data for Example 4.

[0109] Referring to Figures 9 to 11, in the case of the Ti-doped lithium manganese-based oxyhalides of Examples 3 and 4, (400) R The peak is (111) S While it outperformed the peak, the lithium manganese-based oxyhalide in the comparative example, which was not doped with Ti, showed (400) R Peak and (111) S It can be confirmed that the peaks have similar intensities. Specifically, I(400) in Example 3 R / I(111) S The ratio is 1.95, and I(400) in Example 4 R / I(111) S The ratio is 1.15, and the comparative example I(400) R / I(111) S The ratio was shown to be 0.95.

[0110] Furthermore, the XRD data analysis revealed that the ratio of spinel phase to rock salt phase (disordered rock salt phase + layered rock salt phase) was 72.6% in Example 3, 60.5% in Example 4, and 76.4% in the comparative example. This confirmed that the ratio of spinel phase decreases when Ti doping is performed.

Claims

1. It has the composition represented by the following [Chemical Formula 1] and has a disordered rock salt structure. It contains lithium manganese-based oxyhalides, including rock-salt structure. The positive electrode active material having a primary particle size of 50 nm to 300 nm for the lithium manganese-based oxyhalide: [Chemical formula 1] Li ０．５＋ａ Mn ｂ M ｃ O ｄ X ｅ In the above [Chemical Formula 1], M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, and X is a halogen element with 0 < a ≤ 0.7, 0.5 ≤ b < 1, 0 < c ≤ b / 2, 1.5 ≤ d ≤ 1.9, 0.1 ≤ e ≤ 0.5, and d + e ≤ 2.

2. The positive electrode active material according to claim 1, wherein the molar ratio of the cation element to the anion element in the lithium manganese-based oxyhalide is 0.75:1 to 1:

1.

3. The positive electrode active material according to claim 1, wherein in the above [Chemical Formula 1], M is Ti and X is F.

4. The lithium manganese-based oxyhalide is the positive electrode active material according to claim 1, having a composition represented by the following [Chemical Formula 1-1]: [Chemical formula 1-1] Li １＋ａ１ Mn ｂ１ M ｃ１ O ２－ｅ１ X ｅ１ In the above [Chemical Formula 1-1], M is one or more elements selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, and X is a halogen element with 0 < a1 ≤ 0.2, 0.5 ≤ b1 < 1, 0 < c1 ≤ b1 / 2, and 0.1 ≤ e1 ≤ 0.

5.

5. The positive electrode active material according to claim 4, wherein the lithium manganese-based oxyhalide has a single-phase structure with a disordered rock salt structure.

6. The positive electrode active material according to claim 1, wherein the lithium manganese-based oxyhalide has a composition represented by the following [Chemical Formula 1-2]. [Chemical formula 1-2] Li ０．５＋ａ２ Mn ｂ２ M ｃ２ O ２－ｅ２ X ｅ２ In the above [Chemical Formula 1-2], M is one or more selected from the group consisting of Ti, Ni, Zr, V, Co, Sn, Fe, Ir, Cr, Pb, and Ru, and X is a halogen element with 0 < a² < 0.5, 0.5 ≤ b² < 1, 0 < c² ≤ b² / 2, and 0.1 ≤ e² ≤ 0.

5.

7. The lithium manganese-based oxyhalide has a multi-phase structure in which disordered rock salt structure, layered rock salt structure and spinel structure are mixed, as described in claim 6.

8. The positive electrode active material according to claim 7, wherein the proportion of spinel structures in the lithium manganese-based oxyhalide is 75% or less.

9. The lithium manganese-based oxyhalide has a peak intensity of I(111) on the (111) plane. Ｓ (400) plane peak intensity I(400) Ｒ Ratio I (400) Ｒ / I(111) Ｓ The positive electrode active material according to claim 6, wherein the value is 1 or more.

10. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 9.

11. A lithium secondary battery comprising the positive electrode described in claim 10.

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