Method for manufacturing boron-treated positive electrode active material

Abstract

This invention relates to a method for producing a boron-treated cathode active material, and to a boron-treated cathode active material obtainable from said method. The inventors believe that the boron-treated cathode active material of the present invention has a lithium boro oxide compound on its surface. The boron-treated cathode active material of the present invention has been demonstrated to exhibit extremely advantageous properties. For example, compared to an untreated deformed material, cycle stability is significantly improved, crosstalk between the cathode and anode is reduced even after 1000 cycles, and phase changes are reduced even after long-term cycling, while a stable cathode electrolyte interface is achieved.

Description

Technical Field

[0001] The present invention generally relates to a method for producing a boron-treated positive electrode active material and a boron-treated positive electrode active material obtainable by the method. The present invention further relates to a battery comprising the positive electrode active material and use of the battery.

Background Art

[0002] In recent years, small and lightweight electrical products, electronic devices, and communication devices have been rapidly developed. Similarly, electric vehicles, which have emerged as environmentally attractive means of transportation, have been widely adopted. These factors have brought about demand for improvement in the performance of secondary batteries used as power sources for such products. Furthermore, lithium secondary batteries have attracted attention as high-performance batteries due to their high energy density and high reference electrode potential.

[0003] The three main functional components of a lithium ion battery are a negative electrode (anode), a positive electrode (cathode), and an electrolyte. Although many variations exist, the negative electrode of a conventional lithium ion cell is typically made of carbon or metallic lithium, the positive electrode is typically made of a transition metal oxide (in particular, an oxide of cobalt, nickel, and / or manganese), and the electrolyte is typically a non-aqueous solvent containing a lithium salt. For example, a mixture of an organic carbonate and lithium hexafluorophosphate is a well-known liquid electrolyte for lithium ion batteries.

[0004] Demand for electric vehicles (EVs) has increased significantly due to widespread regulations on CO₂ emissions and rising gasoline prices. However, rechargeable electric vehicles can be inconvenient for customers because of their short mileage per charge and long charging time. To address this problem, many researchers are working on improving the energy density and rapid charging capability of lithium ion batteries. For improving energy density, increasing the operating voltage of a positive electrode active material is one of the most effective methods, but it is difficult. First, conventional battery electrolytes suffer from severe degradation during high-voltage operation. Second, high-nickel LiNix Co y Mn z Positive active materials such as O2 (x+y+z=1, NCM) are unstable when charged to over 4.5V, which consequently results in rapid capacity decay and safety problems. Thirdly, the selection of the transition metal composition for the positive electrode active material is important. Cobalt (Co) is commonly used to improve the stability of positive electrode active materials, but its price has risen significantly in recent years. As a result, LiNi 0.5 Mn 1.5 High-voltage cobalt-free lithium transition metal oxides having a spinel crystal structure such as O4 have attracted widespread attention. Their advantages include three-dimensional spinel crystal structure that enables rapid charging / discharging, high-potential operation (e.g., for LiNi 0.5 Mn 1.5 O4, 4.8V), and high theoretical capacity (e.g., for LiNi 0.5 Mn 1.5 O4, 147 mAh / g).

[0005] During charging and / or discharging of a lithium battery, the delithiated positive electrode active material slowly reacts with the non-aqueous electrolyte, which may lead to gradual degradation of the electrochemical performance of lithium-ion batteries using such positive electrode active materials. It has been demonstrated that treatment of positive electrode active materials with a metal such as boron (B) (for example, applying a thin surface layer of a metal compound onto the positive electrode active material, resulting in an increase in the amount of said metal in the surface layer) yields positive electrode active materials that exhibit higher stability compared to their corresponding counterparts lacking such a coating layer.

[0006] Du et al (RSC Adv. 2015, 5, 57293-57299) contemplates a wet coating process by treating LiNi 0.5 Mn 1.5 O2 powder with an ethanol solution of lithium hydroxide and boric acid. However, practical application of such positive electrode active materials has not yet been achieved, since high-voltage operation leads to rapid capacity decay during cycling.

[0007] US20150270550A1 discloses a compound of formula Lia Ni x Mn 2-x Fe y B z Disclosed is a positive electrode active material for a non-aqueous electrolyte secondary battery, which comprises a lithium-transition metal composite oxide represented by O4 (wherein a, x, y and z satisfy 1.00≦a≦1.30, 0.30≦x≦0.60, 0.003≦y≦0.200, and 0.003≦z≦0.200). In this composition, B is contained as a doping element rather than as a coating, which changes the core structure of the material and the properties thereof. The method for synthesizing the material comprises performing boron mixing (dry mixing) and lithiation simultaneously in the first step, which can also result in a different core structure and different properties of the material.

[0008] JP2012116720A relates to a lithium nickel manganese composite oxide having a spinel structure represented by formula (I): Li 1+x Ni 0.5-1 / 4x-1 / 4y Mn 1.5-3 / 4x-3 / 4y B y O4 (wherein x and y satisfy 0≦x≦0.025 and 0<y≦0.01, and the lithium nickel manganese composite oxide has a median diameter of 5 to 20 μm, a particle diameter coefficient of variation of 2.0 to 3.5%, and 0.30 to 1.30 m 2 / g BET specific surface area.) In this composition, B is contained as a doping element rather than as a coating, which changes the core structure of the material and the properties thereof. The method for synthesizing the material comprises performing boron mixing (wet mixing) and lithiation simultaneously in the first step, which can also result in a different core structure and different properties of the material. Summary of the Invention Problem to be Solved by the Invention

[0009] An object of the present invention is to provide a method for producing a spinel-type lithium transition metal oxide that has improved cycle performance when used as a positive electrode active material in a battery.

[0010] A further object of the present invention is to provide a spinel-type lithium transition metal oxide having improved cycle performance when used as a positive electrode active material in an electrochemical cell.

[0011] A further object of the present invention is to provide a spinel-type lithium transition metal oxide having improved phase stability and / or improved cathode electrolyte interface stability when used as a cathode active material in an electrochemical cell.

[0012] A further object of the present invention is to provide a spinel-type lithium transition metal oxide that exhibits a reduction in crosstalk between the positive and negative electrodes when used as a positive electrode active material in an electrochemical cell.

[0013] One or more of these objectives can be achieved by employing a solid mixing step between a precursor comprising a solid boron oxide source, preferably a solid lithium boro oxide source, and a solid lithium transition metal oxide having a spinel crystal structure.

[0014] While we do not wish to be bound by any theory, the inventors believe that the boron-treated cathode active material of the present invention, which contains a lithium boro oxide compound on the surface of the cathode active material, can be obtained by a solid mixing step between a precursor containing a solid boron oxide source, preferably a solid lithium boro oxide source, and a solid lithium transition metal oxide having a spinel crystal structure. The inventors believe that the lithium boro oxide compound on the surface is lithium metaborate (LiBO2).

[0015] As demonstrated in the attached examples, the inventors have found that the boron-treated cathode active material of the present invention exhibits extremely advantageous properties. For example, compared to the untreated deformed material, cycle stability is significantly improved, crosstalk between the cathode and anode is reduced even after 1000 cycles, and even after long-term cycling, phase changes are reduced, and a stable cathode electrolyte interface is achieved. [Means for solving the problem]

[0016] In a first aspect of the present invention, a method for producing a boron-treated cathode active material is provided, and this method is a) A solid lithium boro oxide source, and / or b) One or more precursors comprising a solid boron oxide source and a first lithium source, The process includes a solid mixing step between the cathode active material, which is a solid lithium transition metal oxide having a spinel crystal structure, and the cathode active material.

[0017] In a further aspect of the present invention, a boron-treated cathode active material obtainable by the method is provided.

[0018] In a further aspect of the present invention, a battery containing the positive electrode active material is provided.

[0019] A further aspect of the present invention provides for the use of the battery in an electric vehicle. [Brief explanation of the drawing]

[0020] [Figure 1] The SEM image of Example 1 is shown. [Figure 2] The STEM-EELS mapping for Example 1 is shown. [Figure 3] (a) Full cell cycle performance, where black circles represent capacity values ​​and white circles represent Coulomb efficiency values; (b) Corresponding average charge / discharge voltage; (c) Charge / discharge profile for a different cycle than the LNMO cell; and (d) Charge / discharge profile for a different cycle than the boron-treated LNMO. [Modes for carrying out the invention]

[0021] The following detailed description details preferred embodiments to enable the implementation of the present invention. While the present invention is described with reference to these specific preferred embodiments, it will be understood that the present invention is not limited to these preferred embodiments. Conversely, the present invention includes numerous alternatives, variations, and equivalents, which will become apparent by considering the following detailed description and accompanying drawings.

[0022] As used herein and in the claims, the term “comprising” should not be construed as limiting to the means listed thereafter, nor as excluding other elements or steps. It should be construed as specifying the presence of the mentioned, described features, integers, steps, or components, but not as precluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Accordingly, the expression “composition comprising components A and B” should not be limited to a composition consisting solely of components A and B. This means that, with respect to the present invention, A and B are merely components that are relevant in the composition. Thus, the terms “comprising” and “including” encompass the more restrictive terms “consisting essentially of” and “consisting of.”

[0023] As used herein, the term “positive electrode active material” is also interchangeably referred to as “cathode active material.” As will be understood by those skilled in the art, the positive electrode polarity can be positive or negative depending on the operating mode of the electrochemical cell containing the positive electrode active material. As used herein, the terms “cathode active material” or “positive electrode active material” are defined as a material that is electrochemically active in the positive electrode or cathode. An active material should be understood as a material that, when subjected to a voltage change over a given period of time, is capable of capturing and releasing Li ions.

[0024] Manufacturing method In a first aspect of the present invention, a method for producing a boron-treated positive electrode active material is provided, and this production method is Step 1) a) A solid lithium boro oxide source, and / or b) Providing one or more precursors comprising a solid boron oxide source and a first lithium source, Step 2) Providing a positive electrode active material which is a solid lithium transition metal oxide having a spinel crystal structure, Step 3) A step of solid mixing one or more precursors from Step 1) and the positive electrode active material from Step 2), Step 4) includes the step of heating the mixture obtained in Step 3) to obtain a boron-treated positive electrode active material.

[0025] A very preferred embodiment is, Step 1) To provide one or more precursors comprising a solid lithium boro oxide source, Step 2) To provide a positive electrode active material which is a solid lithium transition metal oxide having a spinel crystal structure, Step 3) Solid mixing of one or more precursors from Step 1) and the positive electrode active material from Step 2), The present invention comprises step 4) heating the mixture obtained in step 3) to obtain a boron-treated positive electrode active material.

[0026] The inventors believe that the method of the present invention yields a lithium transition metal oxide having a spinel crystal structure with a lithium boro oxide-based compound on the surface of the lithium transition metal oxide, and preferably the lithium boro oxide compound is lithium metaborate (LiBO2).

[0027] It has been found that the simplest method for obtaining lithium boro oxide compounds on the surface of lithium transition metal oxides is simply to pre-synthesize (or purchase) lithium metaborate so that lithium metaborate can be provided in step 1) for processing the lithium transition metal oxide. Therefore, in this embodiment of the method, the solid lithium boro oxide source comprises lithium metaborate, and preferably the solid lithium boro oxide source is lithium metaborate.

[0028] However, lithium metaborate may also be prepared in situ (during the processing) by providing a solid boron oxide source and a solid lithium source. As will be understood by those skilled in the art, the identity of the lithium boron oxide on the resulting surface is influenced, among other things, by the ratio of lithium to boron provided during the preparation for the surface treatment. The inventors have found that, depending on the lithium transition metal oxide source used, residual reactive lithium on the surface of the lithium transition metal oxide may provide some or even all of the lithium necessary to react with boron oxide to form a lithium boron oxide compound, in particular lithium metaborate. Therefore, if a solid boron oxide source is provided in step 1), the amount of solid lithium source provided in step 1) depends on the amount of reactive lithium already present on the surface of the lithium transition metal oxide. Determining the appropriate amount of lithium transition metal oxide source to be used is within the scope of the routine skills of those skilled in the art. In some embodiments of the present invention, no lithium source is provided in step 1). As a result, all lithium in the lithium boron oxide compound on the surface originates from reactive lithium already present on the lithium transition metal oxide. Reactive lithium is any form of lithium that forms lithium boro oxide when it comes into contact with boric acid, such as lithium hydroxide.

[0029] In a preferred embodiment, the boron-treated cathode active material is in powder form.

[0030] The solid boron oxide source may be B2O3, H3BO3, B2O5, and Na2B4O7. In a preferred embodiment of the present invention, the boron oxide source is boric acid (H3BO3). The first lithium source may be LiOH, LiOH.H2O, Li2CO3, LiHCO3, and Li2O. In a preferred embodiment of the present invention, the first lithium source is lithium hydroxide (LiOH or LiOH.H2O).

[0031] In a preferred embodiment, one or more precursors are powders.

[0032] In a preferred embodiment, the positive electrode active material in step 2) is a powder.

[0033] Lithium transition metal oxides having a spinel crystal structure are preferably lithium manganese-containing oxides such as lithium manganese-containing oxides represented by formula (I). [ka] (In the formula, M 1 is one or more elements selected from the group consisting of Ni, Co, Fe, and Al. M 2 is one or more elements selected from the group consisting of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce. (0 ≤ a ≤ 0.2, 0 ≤ x ≤ 1, and 0 ≤ z ≤ 0.5.)

[0034] M 1 It is preferably selected from the group consisting of Ni, Fe, and Al, and more preferably M 1 It is Ni.

[0035] In a preferred embodiment of the present invention, the lithium manganese-containing oxide is represented by formula (I), where, 0≦a≦0.1, preferably 0≦a≦0.01, more preferably 0≦a≦0.001, 0.1 ≤ x ≤ 0.9, preferably 0.3 ≤ x ≤ 0.7, more preferably 0.45 ≤ x ≤ 0.55, and / or 0 ≤ z ≤ 0.25, preferably 0 ≤ z ≤ 0.1, more preferably 0 ≤ z ≤ 0.01.

[0036] In some embodiments of the present invention, the lithium manganese-containing oxide is represented by formula (I), where, 0≦a≦0.1, preferably 0≦a≦0.01, more preferably 0≦a≦0.001, 0.3 ≤ x ≤ 0.7, more preferably 0.45 ≤ x ≤ 0.55, 0≦z≦0.25, preferably 0≦z≦0.1, more preferably 0≦z≦0.01.

[0037] In some embodiments of the present invention, the lithium manganese-containing oxide is represented by formula (I), where, M 1 It is selected from the group consisting of Ni, Fe, and Al, and preferably M 1 It is Ni, 0≦a≦0.1, preferably 0≦a≦0.01, more preferably 0≦a≦0.001, 0.3 ≤ x ≤ 0.7, more preferably 0.45 ≤ x ≤ 0.55, 0≦z≦0.25, preferably 0≦z≦0.1, more preferably 0≦z≦0.01.

[0038] In some embodiments of the present invention, the lithium manganese-containing oxide is represented by formula (I), where, M 1 It is selected from the group consisting of Ni, Fe, and Al, and preferably M 1 It is Ni, 0≦a≦0.1, preferably 0≦a≦0.01, more preferably 0≦a≦0.001, 0.3 ≤ x ≤ 0.7, more preferably 0.45 ≤ x ≤ 0.55, 0 ≤ z ≤ 0.01, preferably z = 0.

[0039] In a very preferred embodiment of the present invention, the lithium manganese-containing oxide is represented by formula (I), where, M 1 It is Ni, 0≦a≦0.1, preferably 0≦a≦0.01, more preferably 0≦a≦0.001, 0.3 ≤ x ≤ 0.7, preferably 0.45 ≤ x ≤ 0.55, more preferably 0.49 ≤ x ≤ 0.51, and / or 0 ≤ z ≤ 0.01, preferably z = 0.

[0040] In the most preferred embodiment of the present invention, the lithium manganese-containing oxide is represented by formula (I), where, M 1 It is Ni, 0≦a≦0.1, preferably 0≦a≦0.01, more preferably 0≦a≦0.001, 0.3 ≤ x ≤ 0.7, preferably 0.45 ≤ x ≤ 0.55, more preferably 0.49 ≤ x ≤ 0.51. 0 ≤ z ≤ 0.01, preferably z = 0.

[0041] In some embodiments of the present invention, the lithium manganese-containing oxide is represented by formula (I) (where a=0).

[0042] In some embodiments of the present invention, the lithium manganese-containing oxide is represented by formula (I) (where z=0).

[0043] In some embodiments of the present invention, the lithium manganese-containing oxide is LiNi 0.5 Mn 1.5 It is O4.

[0044] The parameters a, x, z, and a mentioned herein in relation to the composition of the positive electrode active material can be determined by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-OES), preferably by inductively coupled plasma mass spectrometry (ICP-MS).

[0045] In a preferred embodiment, the solid lithium transition metal oxide having a spinel crystal structure is a powder containing particles, the particles consisting of only one primary particle or at most 20 primary particles, as observed in the SEM image. Preferably, at least 30%, more preferably at least 50%, of the particles constituting the powder observed in the SEM image consist of only one primary particle or at most 20 primary particles. The number of primary particles constituting the particles is at least 45 μm x at least 60 μm (i.e., at least 2700 μm). 2 Preferably, at least 100 μm x 100 μm (i.e., at least 10,000 μm) 2 The field of view is determined by the SEM. The particles in the image should be well distributed to avoid overlap between particles. This can be achieved by pouring a small amount of powder sample into an adhesive attached to the SEM sample holder and blowing air to remove excess powder.

[0046] The order in which the components are added in mixing step 3) is not particularly limited. Step 3) may include a first step of mixing some of the components provided in steps 1) and / or 2), followed by adding the remaining components provided in steps 1) and / or 2). The mixing in step 3) may be carried out using any suitable means known to those skilled in the art, such as a simple mortar and pestle, shaft mixer, ribbon mixer, rotary drum, plow shear mixer, paddle mixer, or conical screw mixer. Step 3) may also include the pulverization or grinding of one or more of the precursors provided in step 1) or 2) using, for example, a ball mill, hammer mill, or pin mill.

[0047] According to a preferred embodiment of the present invention, the mixing in step 3) is a solid mixing. As used herein, a solid mixing means that all components to be mixed are in solid form. Therefore, there is no slurry, suspension, or solution to be mixed. It is not excluded that small amounts of solvent or lubricating additives may be added for the solid mixing, but the amount must be low at most so that only surface wetting of the dry materials to be mixed occurs, and no slurry, suspension, or solution is formed. The solid mixing in step 3) is substantially free of any added alcohol or water, preferably substantially free of any added solvent. As those skilled in the art will understand, water of hydration that may be present in one of the dry-mixed components is not considered added water. Preferably, the solid mixing of one or more precursors in step 1) and the cathode active material in step 2) is performed for 1 minute to 1 hour, more preferably 2 minutes to 30 minutes, and most preferably 5 minutes to 15 minutes. Preferably, the solid mixing of one or more precursors from step 1) and the positive electrode active material from step 2) is performed at a speed of 10 rpm to 10,000 rpm, more preferably 100 to 5,000 rpm, and most preferably 1,000 to 3,000 ppm.

[0048] The total amount of one or more precursors and solid lithium transition metal oxides mixed in step 3) is preferably more than 95% by weight of the total composition mixed in step 3), more preferably more than 98% by weight, and more preferably more than 99% by weight. In a preferred embodiment of the present invention, the total composition mixed in step 3) consists essentially of one or more precursors and solid lithium transition metal oxides.

[0049] The total amount of one or more precursors mixed in step 3) is preferably the total weight of the solid lithium transition metal oxide mixed at a rate of at least 0.1% by weight (in step 3), preferably the total weight of the solid lithium transition metal oxide mixed at a rate of at least 0.5% by weight (in step 3), and more preferably the total weight of the solid lithium transition metal oxide mixed at a rate of at least 1% by weight (in step 3). The total amount of one or more precursors mixed in step 3) is preferably the total weight of the solid lithium transition metal oxide mixed at a rate of 0.1 to 10% by weight (in step 3), preferably the total weight of the solid lithium transition metal oxide mixed at a rate of 0.5 to 5% by weight (in step 3), and more preferably the total weight of the solid lithium transition metal oxide mixed at a rate of 1 to 3% by weight (in step 3).

[0050] In a particularly preferred embodiment of the present invention, a method for producing a boron-treated positive electrode active material is provided, and this method is Step 1) To provide solid lithium metaborate, Step 2) To provide a solid lithium transition metal oxide having a spinel crystal structure, Step 3) Solid mixing of lithium metaborate from Step 1) and lithium transition metal oxide having a spinel crystal structure from Step 2), Step 4) includes heating the mixture obtained in Step 3).

[0051] The heating step 4) is carried out at a temperature of at least 200°C, preferably at least 400°C, and more preferably at least 500°C. The heating step 4) is carried out at a temperature of up to 800°C, preferably at most 700°C, and more preferably at most 600°C. From the viewpoint of achieving a uniform surface treatment, a very preferred temperature is in the range of 550 to 650°C, such as in the range of 580 to 620°C. The total time the mixture obtained in step 3) is subjected to that temperature is preferably at least 5 minutes, at least 10 minutes, or at least 30 minutes, for example, in the range of 5 minutes to 48 hours, preferably in the range of 10 minutes to 24 hours, and more preferably in the range of 30 minutes to 20 hours. From the viewpoint of achieving a uniform surface treatment, a very preferred time the mixture obtained in step 3) is subjected to the temperature is in the range of 7 to 13 hours, and more preferably in the range of 8.5 to 11.5 hours. The heating in step 4) is preferably carried out in an inert atmosphere or air, preferably in air.

[0052] After heating in step 4), a micronization step may be performed to reduce the amount and / or size of aggregates formed during heating.

[0053] In a more preferred embodiment of this method, step 1) is: The steps include providing a second lithium source and a further boron source, The steps include mixing a polymer, a first alcohol, a second lithium source, and a further boron source to obtain a liquid mixture, The step of heating the liquid mixture to a temperature of at least 40°C and at most 100°C, preferably at least 50°C and at most 90°C, more preferably at least 75°C and 85°C, most preferably about 80°C to obtain an intermediate product, The process may optionally involve washing the obtained intermediate product with a second alcohol to obtain a washed product. The method further comprises the step of drying and grinding the intermediate product or the washed product to obtain a solid lithium boro oxide source.

[0054] Therefore, as will be understood by those skilled in the art, the solid lithium boro oxide source obtained by the aforementioned method is the solid lithium boro oxide source provided in step 1) of the method of the present invention.

[0055] Further boron sources may be B2O3, H3BO3, B2O5, and Na2B4O7. In a preferred embodiment of the present invention, the further boron source is boric acid (H3BO3). The second lithium source may be LiOH, LiOH·H2O, Li2CO3, LiHCO3, and Li2O. In a preferred embodiment of the present invention, the second lithium source is lithium hydroxide (LiOH or LiOH·H2O).

[0056] The polymer may be any polymer suitable for dissolving in the first alcohol to obtain a liquid mixture. Suitable polymers include polyethylene glycol, hydroxypropyl methylcellulose, polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyacrylic acid copolymer, sodium carboxymethylcellulose, polyethylene oxide, polyvinyl acetate, polyvinyl alcohol acetal, polyvinylpyrrolidone, or polyoxyethylene-polyoxypropylene block copolymer. In preferred embodiments of the present invention, the polymer is polyvinylpyrrolidone. A polymer suitable for the method of the present invention, particularly polyvinylpyrrolidone, may have any molecular weight. For example, although not limited to the present invention, polyvinylpyrrolidone may have a weight-average molecular weight (M) of 1,000 to 1,000,000 g / mol, preferably 10,000 to 500,000 g / mol, more preferably 25,000 to 100,000 g / mol, and most preferably about 50,000 g / mol. w These polymers may have [specific properties]. Such polymers are commercially available.

[0057] The first alcohol may be any alcohol suitable for dissolving the polymer to obtain a liquid mixture. The first alcohol may be an alcohol, e.g., methanol, ethanol, propanol, butanol, or a glycol, e.g., ethylene glycol, propylene glycol, buteryene glycol, or HO(CH2CH2O) n CH2CH2OH (wherein n is an integer from 1 to 10, preferably an integer from 2 to 8, more preferably an integer from 2 to 5, and most preferably n is 3) may also be used. In a preferred embodiment of the present invention, the first alcohol is a glycol, preferably tetraethylene glycol (HO(CH2CH2O)3CH2CH2OH).

[0058] The molar concentration (mol / L or M) of the polymer in the first alcohol is 0.01 to 1 M, preferably 0.1 to 0.8 M, more preferably 0.2 to 0.4 M, and most preferably about 0.3 M.

[0059] The second alcohol is an alcohol, such as methanol, ethanol, propanol, butanol, or a glycol, such as ethylene glycol, propylene glycol, buteryene glycol, or HO(CH2CH2O) n CH2CH2OH (wherein n is an integer from 1 to 10, preferably an integer from 2 to 8, more preferably an integer from 2 to 5, and most preferably n is 3) may also be used. In a preferred embodiment of the present invention, the second alcohol is an alcohol, preferably ethanol.

[0060] In a preferred embodiment of this method, the first alcohol is different from the second alcohol.

[0061] In a preferred embodiment of this method, the molar ratio (mol / mol) of the amount of boron in the further boron source to the amount of lithium in the second lithium source is 5:1 to 1:5, preferably 3:1 to 1:3, more preferably 2:1 to 1:2, and most preferably about 1:1.

[0062] Product-by-process In a further aspect of the present invention, a boron-treated cathode active material obtainable by the method according to the present invention is provided.

[0063] Preferably, the boron-treated positive electrode active material is Step 1) Provide one or more precursors comprising a solid lithium boro oxide source, The steps of providing a second lithium source and a further boron source as described herein, The steps include mixing the polymer described herein, the first alcohol described herein, the second lithium source described herein, and the further boron source described herein to obtain a liquid mixture, The step of heating the liquid mixture to a temperature of at least 40°C and a maximum of 100°C to obtain an intermediate product, Optionally, the obtained intermediate product is washed with a second alcohol as described herein to obtain a washed product, The process includes the steps of drying and grinding the intermediate product or washed product to obtain a solid lithium boro oxide source, Step 2) Providing a positive electrode active material which is a solid lithium transition metal oxide having the spinel crystal structure described herein, Step 3) A step of solid-mixing one or more precursors from Step 1) with the positive electrode active material of Step 2) as described herein, Step 4) can be obtained by a method comprising the step of heating the mixture obtained in Step 3) described herein to obtain a boron-treated cathode active material.

[0064] In a preferred embodiment, the boron-treated cathode active material obtainable by the method according to the present invention has a spinel crystal structure.

[0065] In a preferred embodiment, the boron-treated cathode active material obtainable by the method according to the present invention comprises lithium, M', and oxygen, wherein M' is Ni with content x' such that 5.0 ≤ x' < 60.0 at% relative to M', Mn with content y' such that 20.0 ≤ y' ≤ 90.0 at% relative to Mn, B with content z', where it is 0.0 relative to M'. <z’≦10.0at%である、Bと、 D having a content of d', where 0.0 ≤ d' ≤ 2.0 at% relative to M', and D is at least one element selected from the group consisting of Al, Ba, Ca, Ce, Co, Cr, Fe, La, Mg, Mo, Nb, S, Sr, Ti, V, W, Y, Zn, and Zr, and includes Here, x', y', z', and d' are measured by ICP-MS. Here, x'+y'+z'+d' is 100.0at%.

[0066] As will be understood by those skilled in the art, the amounts of x', y', z', and d' in the positive electrode active material are measured by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-OES), preferably by inductively coupled plasma mass spectrometry (ICP-MS).

[0067] In a more preferred embodiment, Ni is present in content x' such that it is 10.0 ≤ x' ≤ 60.0 at% relative to M', preferably 15.0 ≤ x' ≤ 50.0 at% relative to M', and more preferably 20.0 ≤ x' ≤ 40.0 at% relative to M'.

[0068] In a more preferred embodiment, Mn is present in a content y' of 30.0 ≤ y' ≤ 85.0 at% relative to M', preferably 50.0 ≤ y' ≤ 80.0 at% relative to M', and more preferably 60.0 ≤ y' ≤ 78.0 at% relative to M'.

[0069] In a more preferred embodiment, B has a content b' of 0 ≤ b' ≤ 8.0 at% relative to M', preferably 0.1 ≤ b' ≤ 5.0 at% relative to M', and more preferably 0.5 ≤ b' ≤ 1.0 at% relative to M'.

[0070] In a very preferred embodiment, D is at least one element selected from the group consisting of Al, Zr, Cr, Nb, S, Si, Ti, Y, W, preferably Al, Zr, and W.

[0071] A preferred embodiment is a boron-treated positive electrode active material obtainable by the method according to the present invention, having a Li / M' ratio (mol / mol), preferably a Li(Ni+Mn) ratio of >0.90, preferably >0.92, more preferably >0.95. A preferred embodiment is a boron-treated positive electrode active material obtainable by the method according to the present invention, having a Li / M' ratio, preferably a Li / (Ni+Mn) ratio of <1.10, preferably <1.08, more preferably <1.05. A preferred embodiment is a boron-treated positive electrode active material obtainable by the method according to the present invention, having a Li / M' ratio, preferably a Li / (Ni+Mn) ratio in the range of 0.90 to 1.10, preferably in the range of 0.92 to 1.08, more preferably in the range of 0.95 to 1.05, even more preferably in the range of 0.99 to 1.01, most preferably about 1.00.

[0072] In certain preferred embodiments, the boron-treated cathode active material obtainable by the method according to the present invention has a lithium boro oxide compound, particularly lithium metaborate, on the surface of a solid lithium transition metal oxide.

[0073] A particular preferred embodiment relates to the boron-treated positive electrode active material obtainable by the method according to the present invention, wherein the boron-treated positive electrode active material obtainable by the method according to the present invention has a boron content B B It has B B However, the boron content B, which is measured by XPS analysis and expressed as a mole fraction B relative to the total amount of Ni, Mn, and B, and which can be obtained by the method according to the present invention, is defined as z' / (x'+y'+z'). A It has ratio B B / B A It is >30.

[0074] A particular more preferred embodiment relates to the boron-treated cathode active material obtainable by the method according to the present invention, wherein ratio B B / B A >35, preferably ratio B B / B A >40, more comfortably compared to B B / B A It is >45.

[0075] A particular more preferred embodiment relates to the boron-treated cathode active material obtainable by the method according to the present invention, wherein ratio B B / B A <90, preferably ratio B B / B A <70, Comfort ratio B B / B A It is <55. A particular more preferred embodiment relates to the boron-treated cathode active material obtainable by the method according to the present invention, wherein ratio B B / B A The range is 35 to 90, preferably ratio B B / B A The ratio is in the range of 40 to 70, and more preferably ratio B B / B A The range is 45 to 55.

[0076] In the context of this invention, X-ray photoelectron spectroscopy (XPS) analysis was performed using Kratos AXIS Supra. XPS was performed using 10 -8The system operates using a 15kV Al anode source at a Torr vacuum level. All XPS measurements are collected using an automated neutralization device during acquisition. Survey scans are collected with a 1.0eV step size, followed by high-resolution scans with a 0.1eV step size. All data are calibrated using the C 1s peak at 284.8eV. The sample transfer process is airtight to avoid any possibility of degradation. Curve fitting is performed in CasaXPS Version 2.3.19PR1.0 using Shirley-type background processing and Scofield sensitivity coefficients. The line shape GL(30) is a Gauss / Lorentz function with 70% Gaussian lines and 30% Lorentz lines.

[0077] In a more preferred embodiment, the boron-treated cathode active material obtainable by the method according to the present invention, preferably having a spinel crystal structure, is represented by formula (II). [ka] (In the formula, M 3 is one or more elements selected from the group consisting of Ni, Co, Fe, and Al, and M 4 is one or more elements selected from the group consisting of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce, where 0≦a''≦0.2, 0≦x''≦1, 0≦z''≦0.5, and 0 <b’’≦0.01である。)

[0078] M 3 It is preferably selected from the group consisting of Ni, Fe, and Al, and more preferably M 3 It is Ni. In a preferred embodiment of the present invention, the boron-treated positive electrode active material obtainable by the method according to the present invention is represented by formula (II), where, 0≦a''≦0.1, preferably 0≦a''≦0.01, more preferably 0≦a''≦0.001, 0.1≦x’’≦0.9, preferably 0.3≦x’’≦0.8, more preferably 0.45≦x’’≦0.75, 0≦z’’≦0.25, preferably 0≦z’’≦0.1, more preferably 0≦z’’≦0.01, and / or 0<b’’≦0.01, preferably 0.001≦b’’≦0.05, more preferably 0.005≦b’’≦0.01.

[0079] In some embodiments of the present invention, the boron-treated positive electrode active material obtainable by the method according to the present invention is represented by formula (II), wherein 0≦a’’≦0.1, preferably 0≦a’’≦0.01, more preferably 0≦a’’≦0.001, 0.3≦x’’≦0.8, preferably 0.45≦x’’≦0.75, 0≦z’’≦0.25, preferably 0≦z’’≦0.1, more preferably 0≦z’’≦0.01, 0<b’’≦0.01, preferably 0.001≦b’’≦0.05, more preferably 0.005≦b’’≦0.01.

[0080] In some embodiments of the present invention, the boron-treated positive electrode active material obtainable by the method according to the present invention is represented by formula (II), wherein M 3 is selected from the group consisting of Ni, Fe and Al, preferably M 3 is Ni, 0≦a’’≦0.1, preferably 0≦a’’≦0.01, more preferably 0≦a’’≦0.001, 0.3≦x’’≦0.8, more preferably 0.45≦x’’≦0.75, 0≦z’’≦0.25, preferably 0≦z’’≦0.1, more preferably 0≦z’’≦0.01, 0<b’’≦0.01, preferably 0.001≦b’’≦0.05, more preferably 0.005≦b’’≦0.01.

[0081] In some embodiments of the present invention, the boron-treated positive electrode active material obtainable by the method according to the present invention is represented by formula (II), where, M 3 It is selected from the group consisting of Ni, Fe, and Al, and preferably M 3 It is Ni, 0≦a''≦0.1, preferably 0≦a''≦0.01, more preferably 0≦a''≦0.001, 0.3 ≤ x'' ≤ 0.8, more preferably 0.45 ≤ x'' ≤ 0.75, 0 ≤ z'' ≤ 0.01, preferably z'' = 0, 0.001 ≤ b'' ≤ 0.05, preferably 0.005 ≤ b'' ≤ 0.01.

[0082] In a very preferred embodiment of the present invention, the boron-treated cathode active material obtainable by the method according to the present invention is represented by formula (II), where, M 3 It is Ni, 0≦a''≦0.1, preferably 0≦a''≦0.01, more preferably 0≦a''≦0.001, 0.3 ≤ x'' ≤ 0.8, more preferably 0.45 ≤ x'' ≤ 0.75, 0 ≤ z'' ≤ 0.01, preferably z'' = 0, and / or 0.001 ≤ b'' ≤ 0.05, preferably 0.005 ≤ b'' ≤ 0.01.

[0083] In the most preferred embodiment of the present invention, the boron-treated positive electrode active material obtainable by the method according to the present invention is represented by formula (II), where, M 3 It is Ni, 0≦a''≦0.1, preferably 0≦a''≦0.01, more preferably 0≦a''≦0.001, 0.3≦x''≦0.8, more preferably 0.45≦x''≦0.75, most preferably 0.45≦x''≦0.55 or 0.70≦x''≦0.75, 0 ≤ z'' ≤ 0.01, preferably z'' = 0, 0.001 ≤ b'' ≤ 0.05, preferably 0.005 ≤ b'' ≤ 0.01.

[0084] In some embodiments of the present invention, the boron-treated cathode active material obtainable by the method according to the present invention is represented by formula (II), where a = 0. In some embodiments of the present invention, the boron-treated cathode active material obtainable by the method according to the present invention is represented by formula (II), where z=0.

[0085] As will be understood by those skilled in the art, the amounts of a'', x'', z'', and b'', in the positive electrode active material are measured by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-OES), preferably by inductively coupled plasma mass spectrometry (ICP-MS).

[0086] In a preferred embodiment, the boron-treated cathode active material obtainable by the method according to the present invention, preferably having a spinel crystal structure, is a powder containing particles, the particles consisting of only one primary particle or at most 20 primary particles, as observed in SEM images. Preferably, at least 30%, and more preferably at least 50%, of the particles observed in SEM images consist of only one primary particle or up to 20 primary particles. The number of primary particles constituting the particles is at least 45 μm x at least 60 μm (i.e., at least 2700 μm). 2 Preferably, at least 100 μm x 100 μm (i.e., at least 10,000 μm) 2 The field of view is determined by the SEM. The particles in the image should be well distributed to avoid overlap between particles. This can be achieved by pouring a small amount of powder sample into an adhesive attached to the SEM sample holder and blowing air to remove excess powder.

[0087] battery In a third aspect, the present invention relates to a battery comprising a boron-treated positive electrode active material obtainable by the method according to the present invention.

[0088] In preferred embodiments, the battery may include a liquid electrolyte such as a lithium salt in an organic solvent. A suitable example is LiPF6 in ethylene carbonate (EC) and / or ethylmethyl carbonate (EMC), for example, 1 M LiPF6 in EC:EMC = 3:7 (vol%).

[0089] Preferably, the battery further comprises an anode containing an anode active material. Suitable electrochemically active anode materials are materials known in the art. For example, the anode may include graphite-carbon or a metal alloy containing lithium. Preferably, the anode contains graphite-carbon.

[0090] In a preferred embodiment, the battery according to the present invention has an efficiency of at least 80%, preferably at least 82%, more preferably at least 84%, and most preferably at least 85%.

[0091] In a preferred embodiment, the battery according to the present invention has a first discharge capacity of at least 100.0 mAh / g, preferably at least 110.0 mAh / g, and most preferably at least 115.0 mAh / g.

[0092] As will be understood by those skilled in the art, the electrochemical performance of all cells, including efficiency and primary discharge capacity, is tested at room temperature using either the Neware Battery Test System (Neware Technology Ltd., China) or the Arbin BT2000 instrument (Arbin instrument, USA). The voltage range is 3.3 to 4.85V.

[0093] use In a fourth aspect, the present invention relates to the use of a boron-treated positive electrode active material obtainable by the method according to the present invention in a battery.

[0094] A preferred embodiment is the use of a boron-treated cathode active material obtainable by the method according to the present invention in a battery for increasing the efficiency of the battery and / or increasing the first discharge capacity of the battery.

[0095] In a fifth aspect, the present invention relates to the use of a battery according to the present invention in one of the following: a portable computer, a tablet, a mobile phone, an energy storage system, an electric vehicle, or a hybrid electric vehicle, preferably in an electric vehicle or a hybrid electric vehicle. [Examples]

[0096] Experimental tests used in the examples The following analytical methods are used in the examples.

[0097] A) Inductively coupled plasma-mass spectrometry (ICP-MS) In this specification, the elemental content of the positive electrode active material in the examples and comparative examples described below is measured by ICP-MS analysis using Thermo iCAP RQ ICP-MS. 0.2 grams of the powder sample is dissolved in 2 mL of high-purity hydrochloric acid in a glass vial overnight in a fume hood. The vial is then filled with 17 mL of deionized water and subsequently homogenized completely. 18 μL is pipettered and transferred to a 15 mL polypropylene centrifuge tube for a second dilution. The centrifuge tube is then filled with 11 mL of matrix solution and subsequently homogenized. Finally, this solution is used for measurement.

[0098] B) XPS XPS analysis was performed using Kratos AXIS as described above. XPS was 10 -8 The system operates using a 15kV Al anode source at a Torr vacuum level. All XPS measurements are collected using an automated neutralization device during acquisition. Survey scans are collected with a 1.0 eV step size, followed by high-resolution scans with a 0.1 eV step size. All data are calibrated using the C 1s peak at 284.8 eV. The sample transfer process is airtight to avoid any possibility of degradation.

[0099] Curve fitting is performed in CasaXPS Version 2.3.19PR1.0 using Shirley-type background processing and Scofield sensitivity coefficients. The fitting parameters are given in Table 1a. The linear shape GL(30) is a Gaussian / Lorentz function with 70% Gaussian lines and 30% Lorentz lines. [Table 1a]

[0100] For the Ni and Co peaks, constraints are set for each defined peak according to Table 1b. [Table 1b]

[0101] The B surface content determined by XPS is expressed as the atomic fraction obtained by dividing the B in the particle's surface layer by the total content of Ni, Mn, and B in that surface layer. This is calculated as follows: [ka]

[0102] C) Coin Cell C1) Electrode fabrication To evaluate the electrochemical performance, electrodes were prepared using Example 1 and Comparative Example 1. 3 mAh / cm² 2For the cathode load, SPC65 (carbon black, TIMCAL Ltd.) is used as the conductive agent and HSV900 (PVDF, Arkema Inc.) as the binder in a mass ratio of 90:5:5. The mixture is then thoroughly dissolved in an appropriate amount of N-methyl-2-pyrrolidone (NMP, ≥99%, Sigma-Aldrich) and mixed using a Thinky Mixer to form a slurry. The slurry is cast onto an Al foil and dried overnight in a vacuum oven at 80°C, followed by drying at a high temperature of 120°C for 1 hour. The electrode is punched out into a cathode disk with a diameter of 12.7 mm, and the active material load is approximately 24 mg / cm³. 2 That is the case.

[0103] C2) Electrode Assembly CR2032 is assembled with a 94% active material mass ratio using graphite electrodes provided by the Ningbo Institute of Materials Technology & Engineering (NIMTE). The graphite electrodes are punched into 13 mm diameter anode disks, with a designed N / P ratio of approximately 1.1. Celgard 2325 is used as the separator. 1 M LiPF6 (Gotion, USA) in EC:EMC = 3:7 (vol%) is indicated as the baseline electrolyte. All coin cells are assembled in an Ar-filled glove box under humidity control (H2O < 0.5 ppm), and 50 μL of electrolyte is used for each coin cell.

[0104] C3) Performance Evaluation After assembly, the coin cells (CR2032) are evaluated by cycling them at a rate of C / 3 (1C = 147mA / g) after two formation cycles at C / 10. The electrochemical performance of all cells is tested at room temperature using either the Neware Battery Test System (Neware Technology Ltd., China) or the Arbin BT2000 instrument (Arbin instrument, USA). The voltage range is 3.3–4.85V.

[0105] The present invention is further illustrated by the following examples:

[0106] Example 1 Example 1 was prepared according to the following steps. 1) Prepare lithium transition metal oxides (LNMOs) having a spinel crystal structure according to the following: a. Preparation of transition metal precursors: Metal composition Ni 0.5 Mn 1.5 Nickel-based transition metal powders containing [specific properties] were prepared by a coprecipitation process in a large-scale continuous stirred tank reactor (CSTR) containing mixed nickel manganese sulfate, sodium hydroxide, and ammonia. b. A transition metal precursor is mixed with a lithium source to obtain a first mixture having a molar ratio of lithium to metal (Ni + Mn) of 0.5. c. The first mixture is heated at a temperature of 1055°C in a flow of dry air, and then pulverized to obtain a lithium transition metal oxide having a spinel crystal structure. 2) Dissolve 0.03 mol of polyvinylpyrrolidone (PVP) (MW = 50,000 g / mol) in 100 mL of tetraethylene glycol (TTEG) to obtain a second mixture. 3) Dissolve 0.015 mol of LiOH·H2O in the second mixture, then add 0.015 mol of H3BO3 to obtain a liquid mixture. 4) Heat the liquid mixture to 80°C for 2 hours, then cool it to room temperature to obtain the intermediate product. 5) Wash the intermediate product seven times with ethanol to obtain a washed intermediate product. 6) The washed intermediate product is dried at 80°C for 24 hours, and then pulverized to obtain solid lithium boro oxide source powder. 7) The lithium transition metal oxide prepared in step 1) is mixed with solid lithium boro oxide source powder in a weight ratio of 100:2 using a Thinky Mixer at 2000 rpm for 10 minutes to obtain a third mixture. 8) The third mixture is heated at 600°C for 10 hours, then cooled and pulverized to obtain the powder of Example 1.

[0107] Comparative Example 1 Comparative Example 1 was prepared according to the following steps: 1) Prepare a lithium transition metal oxide having a spinel crystal structure according to the following: a. Preparation of transition metal precursors: Metal composition Ni 0.5 Mn 1.5 Nickel-based transition metal powders containing [specific properties] were prepared by a coprecipitation process in a large-scale continuous stirred tank reactor (CSTR) containing mixed nickel manganese sulfate, sodium hydroxide, and ammonia. b. A transition metal precursor is mixed with a lithium source to obtain a first mixture having a lithium molar ratio of 0.5 to metal (Ni + Mn). c. The first mixture is heated in dry air at a temperature of 1055°C, and then pulverized to obtain a lithium transition metal oxide having a spinel crystal structure. 2) 1.259 grams of LiOH·H2O and 3.710 grams of H3BO3 are mixed in ethanol to obtain a second mixture having a Li / B molar ratio (mol / mol) of 1:2. 3) Add 10 grams of lithium transition metal oxide to the second mixture to obtain a third mixture. 4) Stir the third mixture while heating at 80°C until the solvent evaporates to obtain the fourth mixture. 5) The fourth mixture is pressed into pellets, heated at 500°C for 10 hours, and then pulverized after cooling to obtain the powder of Comparative Example 1.

[0108] Comparative Example 2 Comparative Example 2 was prepared according to the same method as Comparative Example 1, with the exception that the molar ratio of LiOH·H2O to H3BO3 in step 2 was 1:1, and the heating temperature in step 5) was 600°C.

[0109] result Figure 2 shows the STEM-EELS mapping of boron-treated LNMO. For the surface portion, a lithium boro oxide compound that does not contain Ni / Mn was demonstrated on the LNMO surface, confirming its presence on the LMNO surface.

[0110] Figure 3 shows (a) full cell cycle performance, where black circles represent capacity values ​​and white circles represent Coulomb efficiency values, (b) the corresponding average charge / discharge voltage, (c) the charge / discharge profile for a different cycle than the LNMO cell, and (d) the charge / discharge profile for a different cycle than the boron-treated LNMO. As shown in Figure 3(a), the capacity retention after 1000 cycles (capacity after 1000 cycles / initial capacity) is 18.1% for untreated LNMO and 46.1% for boron-treated LNMO. Untreated LNMO shows a steep slope at the start up to about 70 cycles, followed by a large capacity drop during this interval, and then a rapid cycle degradation until about 300 cycles. In contrast, boron-treated LNMO shows a slower degradation at the start, followed by a stable slope after 100 cycles and a stable Coulomb efficiency of 99.9%. It can be inferred that the lithium boro oxide compound present on the surface of the LMNO minimizes side reactions with the electrolyte. Figure 3(b) also shows that the boron-treated LNMO has a more stable charge / discharge voltage from the start, demonstrating its improved performance. Figures 3(c) and (d) show the charge / discharge profiles of untreated and boron-treated LNMO full cells. The charge plateau of the untreated LNMO cell shifts to a higher voltage range, while the discharge plateau shifts to a lower range, suggesting an increase in internal impedance, but at the same time, both charge and discharge capacities decrease rapidly, which means a rapid loss of active lithium stock. The charge / discharge plateau of the boron-treated LNMO shifts much less than that of the untreated sample, meaning that the lithium boro oxide compound plays a significant role in controlling the internal impedance. Regarding the length of the constant voltage (CV) section at 4.85V, the boron-treated LNMO remained constant over the cycle, while the CV section of the untreated LNMO extended from 100 cycles. This suggests that lithium from the positive electrode was not sufficiently deintercalated during charging, resulting in low and unstable Coulomb efficiency. [Table 2]

[0111] Table 2 summarizes the results for Example 1, Comparative Example 1, and Comparative Example 2. In the XPS analysis, B B A value greater than 0 indicates that B is present on the surface of the cathode active material, as is the case with XPS measurements where the signal is acquired from the top of the sample, i.e., the first few nanometers of the surface layer (e.g., 1 nm to 10 nm). On the other hand, B from ICP-MS measurements A This represents the total B content of the particles. Therefore, a B greater than 1 B / B A The ratio of XPS results to ICP-MS results indicates that B is mainly present on the surface of the positive electrode active material.

Claims

1. A method for producing a boron-treated positive electrode active material, Step 1) a) A solid lithium boro oxide source, and / or b) Providing one or more precursors comprising a solid boron oxide source and a first lithium source, Step 2) Providing a positive electrode active material which is a solid lithium transition metal oxide having a spinel crystal structure, Step 3) A step of solid mixing the one or more precursors from Step 1) and the positive electrode active material from Step 2), A method comprising step 4) heating the mixture obtained in step 3) to obtain the boron-treated cathode active material.

2. The method according to claim 1, wherein the one or more precursors include the solid lithium boro oxide source.

3. Step 1) The solid lithium boron oxide source is - A step of providing a second lithium source and a further boron source, - A step of mixing the polymer, the first alcohol, the second lithium source, and the further boron source to obtain a liquid mixture, - The step of heating the liquid mixture to a temperature of at least 40°C and a maximum of 100°C to obtain an intermediate product, - Optionally, the intermediate product obtained is washed with a second alcohol to obtain a washed product. The method according to claim 2, which can be obtained by the steps of: drying and grinding the intermediate product or the washed product to obtain the solid lithium boro oxide source.

4. The method according to claim 3, wherein the polymer is polyvinylpyrrolidone.

5. The method according to claim 3 or 4, wherein the first alcohol is a glycol, preferably tetraethylene glycol.

6. The method according to any one of claims 3 to 5, wherein the second lithium source is lithium hydroxide.

7. The method according to any one of claims 3 to 6, wherein the further boron source is boric acid.

8. The method according to any one of claims 3 to 7, wherein the molar ratio of the amount of boron in the further boron source to the amount of lithium in the second lithium source is 2:1 to 1:2, preferably about 1:

1.

9. The method according to any one of claims 1 to 8, wherein the temperature in step 4) is at least 200°C, preferably at least 400°C, and more preferably at least 500°C.

10. The method according to any one of claims 1 to 9, wherein the heating time in step 4) is in the range of 5 minutes to 48 hours, preferably in the range of 10 minutes to 24 hours, and more preferably in the range of 30 minutes to 20 hours.

11. The method according to any one of claims 1 to 10, wherein the total amount of the one or more precursors mixed in step 3) is 0.1 to 10% by weight of the total weight of the solid lithium transition metal oxide mixed in step 3), preferably 0.5 to 5% by weight of the total weight of the solid lithium transition metal oxide mixed in step 3), and more preferably 1 to 3% by weight of the total weight of the solid lithium transition metal oxide mixed in step 3).

12. A boron-treated cathode active material having a spinel crystal structure, obtainable by the method described in any one of claims 1 to 11, preferably according to the method described in any one of claims 3 to 11.

13. It contains lithium, M', and oxygen, where M' is - Ni with content x' such that 5.0 ≤ x' < 60.0 at% relative to M', - Mn with content y', where 20.0 ≤ y' ≤ 90.0 at% relative to M', - B with content z' such that 0.0 < z' ≤ 10.0 at% relative to M', - A D having a content of d', where 0.0 ≤ d' ≤ 2.0 at% relative to M', and D is at least one element selected from the group consisting of Al, Ba, Ca, Ce, Co, Cr, Fe, La, Mg, Mo, Nb, S, Sr, Ti, V, W, Y, Zn, and Zr, and comprises - Here, x', y', z', and d' are measured by ICP-MS, The positive electrode active material according to claim 12, wherein x' + y' + z' + d' in the formula is 100.0 at%.

14. A battery comprising the positive electrode active material according to claim 12 or 13.

15. Use of the battery according to claim 14 in an electric vehicle or a hybrid electric vehicle.

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