Si-modified high-voltage spinel lnmo cathode material

Abstract

This invention provides an LNMO microparticle material comprising secondary particles, wherein the secondary particles are composed of a large number of crystals, and the crystals are composed of a large number of microcrystals, wherein the D of the secondary particles, as measured by laser diffraction according to ISO 13320:2020, is... 50 The particle size is from 4.0 µm to 25 µm, and wherein, as measured by scanning electron microscopy (SEM), the D of the crystal is... 50 The particle size is from 0.5 µm to 7.0 µm, and the LNMO particulate material is silicon-modified. In other aspects, the present invention also provides a method for manufacturing silicon-modified lithium nickel manganese oxide (LNMO) particulate material, and silicon-modified LNMO materials obtainable by the method according to the invention.

Description

[0001] This invention relates to improving the performance of high-voltage spinel lithium nickel manganese oxide (LNMO) cathode active materials in secondary lithium-ion batteries through silicon modification. Therefore, this invention relates to silicon-modified LNMO materials, such as high-voltage spinel LNMO cathode materials. This invention also provides a method for manufacturing silicon-modified LNMO materials.

[0002] Description of background technology

[0003] The growing market for rechargeable Li-ion batteries (LIBs) in electric vehicles, renewable energy, and consumer electronics necessitates the development of advanced batteries that are safe, cost-effective, and possess high energy and power densities. In this regard, lithium-ion batteries have dominated the market for portable electronic applications due to their superior energy and power density capabilities. Current trends are shifting towards the electrification of transportation and the development of large-scale energy storage systems (ESS) for various applications. Unfortunately, current lithium-ion batteries still suffer from poor safety, low energy density, and low power density, which severely hinders their widespread adoption in electric vehicles.

[0004] Currently, several materials, including LiCoO2, LiNiO2, LiMn2O4, and LiNi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.8 Mn 0.1 Co 0.1 O2 has been developed and used as a cathode material for lithium-ion batteries. However, these intercalated materials exhibit severe capacity decay and several safety issues.

[0005] Several reasons have been identified for this capacity decay and safety issue, including electrolyte degradation at higher cutoff voltages (>4.5V), structural instability, and the dissolution of metal ions in the electrolyte due to HF generation. Among the materials being developed for lithium-ion batteries, high-voltage spinel LiNi1 is... 0.5 Mn 1.5 O4 (LNMO) is a promising cathode material due to its high energy density and high power density, boasting a high theoretical capacity (~147 mAh g⁻¹) and a high operating voltage (~4.7 V, relative to Li₂). +The degradation of LNMO cathode materials is caused by the decomposition of the electrolyte at high operating voltages and temperatures (>45°C), resulting in poor cycle performance. This is due to parasitic reactions on the material surface, leading to rapid capacity decay. To alleviate LNMO-related problems, researchers have employed several methods, including morphology and particle size control, structural disorder and lithium concentration regulation, Mn / Ni cation doping, and surface modification. Surface modification has been widely recognized as a promising method for improving the performance of LNMO cathode materials.

[0006] Several material categories have been reported as coating materials, including oxides (ZrO2, SiO2, MgO, TiO2, SiO2, Al2O3) and ion conductors (Li7La3Zr2O). 12 Li 3x La 2 / 3-x TiO3, Li 1.3 Al 0.3 Ti 1.7 (PO4)3), conductive polymers, and conductive carbon. All these coatings reduce undesirable side reactions between the electrolyte and the cathode material, thus improving the performance of these materials. Among these categories of coatings, oxide coatings are simple and inexpensive, and have shown promising results in improving the performance of cathode materials operating under various conditions. These oxide coatings prevent undesirable side reactions between the cathode material surface and the electrolyte, resulting in improved structural stability and capacity retention. Recent reports of ZrO2 coatings on LNMO and lithium-rich oxide materials have shown extremely high rate performance, although the reasons for such high performance are not yet fully understood. Unfortunately, most of these surface modification methods are not commercially feasible for large-scale production, and it is difficult to control the thickness and uniformity of these coatings. Most of these coatings may also increase interfacial resistance, which hinders the migration of Li ions during insertion and extraction.

[0007] Therefore, there is a need in the field for high-voltage cathode materials with high theoretical capacity and high operating voltage, which exhibit improved cycle performance and capacity retention. Invention Overview

[0009] This invention addresses these problems in the prior art by providing a silicon-modified lithium nickel manganese oxide (LNMO) material with a specific particle morphology as described herein.

[0010] Therefore, in a first aspect, an LNMO microparticle material comprising secondary particles is provided, wherein the secondary particles are composed of a large number of crystals, and the crystals are composed of a large number of microcrystals.

[0011] The D of the secondary particles, as measured by laser diffraction according to ISO 13320:2020, is... 50The particle size is from 4.0 µm to 25 µm; and wherein, as measured by scanning electron microscopy (SEM), the D of the crystal is... 50 The particle size is 0.5 µm to 7.0 µm; and the LNMO microparticle material is silicon modified.

[0012] The present invention has also found that the silicon-modified LNMO microparticle material of the present invention can be advantageously used as a cathode material in lithium-ion batteries.

[0013] In a second aspect, the present invention provides a method for manufacturing silicon-modified lithium nickel manganese oxide (LNMO) particulate materials, the method comprising the following steps:

[0014] (a) Mixing the LNMO microparticle precursor with a solution of alkyl silicate in an organic or aqueous solvent,

[0015] (b) Remove the organic or aqueous solvent to obtain a dry mixture.

[0016] (c) The mixture is calcined in an oxygen-containing atmosphere at a temperature of 850°C to 1100°C to form silicon-modified LNMO particulate material.

[0017] Thirdly, the present invention provides a silicon-modified LNMO material obtainable by the method according to the present invention. Invention Details

[0019] Silicon-modified lithium nickel manganese oxide (LNMO) particulate materials

[0020] In a first aspect, the present invention provides a silicon (Si) modified particulate lithium nickel manganese oxide (LNMO) material comprising secondary particles, wherein the secondary particles consist of a large number of crystals, and said crystals consist of a large number of microcrystals. Although the present invention is described herein with respect to LNMO materials, preferably cobalt-free LNMO materials with silicon modification, the present invention is applicable to any LNMXO cathode active spinel-type material having a similar crystal structure, wherein X comprises one or more elements as defined herein, and wherein X may partially replace Ni and / or Mn in the LNMO material.

[0021] This invention achieves silicon modification of LNMO microparticles using a high-temperature synthesis with organosilicates as the Si source, also referred to as "silicon treatment." As described herein, in this high-temperature synthesis, Si is expected to act as a modifying element, resulting in a silicon phase on and / or within the LNMO microparticles, as analyzed by cross-sectional SEM. Therefore, silicon can exist as a bulk dopant within the material, as a surface dopant, or can form a separate phase along grain boundaries, a surface coating, or simply as a flux, or any combination thereof. Thus, the Si modification of this invention involves introducing silicon (Si) into the surface and bulk phase of LNMO materials. Silicon can exist as Si-based inorganic compounds, including SiO2 and Li2SiO3. Silicon can also exist as a Li-Si-O glassy phase or as an amorphous phase.

[0022] However, the aforementioned treatment can also result in silicon being present within the LNMO particles, thereby achieving silicon doping of the material. Therefore, even though the modification may be termed "surface modification," this does not preclude the possibility that the modification can also exist within the internal portion of the secondary particles. Thus, within the scope of this invention, silicon modification is not merely surface modification, but can also achieve silicon doping within the secondary particles or segregation at grain boundaries. Typically, silicon modification is uniformly distributed on the surface of the particles.

[0023] The silicon-modified lithium nickel manganese oxide (LNMO) material of the present invention is typically a cobalt-free lithium nickel manganese mixed oxide, which may contain additional elements, such as one or more elements selected from Mg, Ca, Zn, Fe, Al, Ti, Mo, W, Ta, Zr, B, Si, Cr, and Cu. These elements (multiple elements) may be present in the LNMO material, or may partially replace Ni and / or Mn in the LNMO material, in addition to Ni and Mn. Therefore, the LNMO material of the present invention can also be defined as an LNMXO material, where X is one or more elements as defined above. In this embodiment, the LNMXO material can also be defined by the following formula:

[0024] (i)LiNi 0.5-a X a Mn 1.5 O4, or

[0025] (ii)LiNi 0.5 X a Mn 1.5-a O4,

[0026] Where a is 0 to 0.1, preferably 0.01 to 0.06.

[0027] Most preferably, the LNMO material is high-voltage spinel LiNi. 0.5 Mn 1.5O4 material. The LNMO material of this invention is suitable for use as a positive electrode active material in secondary lithium-ion batteries. The morphology of the sample can be examined using a scanning electron microscope (SEM), and the type, content, and distribution of elements in the LNMO material can be examined using an energy-dispersive spectroscopy (EDS) instrument.

[0028] The microparticle structure of LNMO materials Figure 1 The diagram illustrates this. As shown, the LNMO particulate material comprises secondary particles, which are composed of a large number of relatively small crystals. These crystals consist of a large number of microcrystals.

[0029] The secondary particles are typically spherical. Preferably, the sphericity of the secondary particles is 1.0 to 0.80, more preferably 0.99 to 0.90, and even more preferably 0.98 to 0.95. The sphericity can be determined by methods well known in the art, and is preferably determined by the cross-section of the secondary particles.

[0030] As measured by laser diffraction according to ISO 13320:2020, the D of secondary particles... 50 The particle size is from 4.0 µm to 25 µm, and preferably from 5.0 µm to 20 µm, and more preferably greater than 5.0 µm, 6.0 µm, 7.0 µm, 8.0 µm, 10 µm or 12 µm, and more preferably less than 18 µm, 16 µm or 14 µm.

[0031] As measured by scanning electron microscopy (SEM), crystals can also be called "primary particles" with a density of D. 50 The particle size is from 0.5 µm to 7.0 µm, and preferably from 1.0 µm to 5.0 µm, and more preferably greater than 1.5 µm, 2.0 µm or 2.5 µm, and more preferably less than 6.0 µm, 5.0 µm or 4.0 µm.

[0032] As determined by XRD Rietveld refinement (Rietveld, HM (1969). “A profile refinement method for nuclear and magnetic structures”. Journal of Applied Crystallography. 2 (2): 65-71), the crystallite size ranges from 90 nm to 400 nm, preferably from 160 nm to 300 nm. XRD measurements were performed using a Bruker D8 X-ray diffraction analyzer (Bruker, Germany). The crystallite shape is typically tetrahedral, octahedral, and / or truncated octahedral, or a mixture thereof. Using the method described below, the crystallites of silicon-modified LNMO can be transformed into a favorable (truncated) octahedral shape, which improves the electrochemical performance of the material by providing a more stable surface.

[0033] Silicon-modified LNMO materials typically have the space group Fd⁻³m cubic phase and are also referred to in the art as “disordered spinel” materials. Alternatively, silicon-modified LNMO materials can also have the space group P4332, which is referred to in the art as “ordered spinel” materials. Typically, trace amounts of Li can be detected in both materials. x Ni 1-x O, due to the absence of nickel or oxygen, is frequently found in disordered LNMO materials. This impurity phase can be eliminated by synthesizing non-stoichiometric spinel LNMO materials. Stoichiometric spinel is generally defined in this art as LiNi. 0.5 Mn 1.5 O4 (with space group P4332 in XRD analysis, also commonly referred to in the art as "ordered LNMO"). Depending on the starting materials and process conditions, the particulate materials of this invention can also form non-stoichiometric compositions (with Fd-3m structures in XRD analysis, commonly referred to as "disordered LNMO"). Disordered materials can be defined by the following formula:

[0034] (I)LiNi 0.5-x Mn 1.5+x O4 (nickel deficiency)

[0035] (II) LiNi 0.5-x Mn 1.5+x O 4-d (Nickel deficiency and oxygen deficiency)

[0036] (III) LiNi 0.5 Mn 1.5 O 4-d (Hypoxia)

[0037] Where d and x are typically independent and range from 0 to 0.1, preferably from 0.01 to 0.06.

[0038] The crystal structure of LNMO materials can be analyzed using XRD measurements with Bruker D8 X-ray diffraction analysis (Bruker, Germany).

[0039] The present invention has unexpectedly discovered that silicon treatment of LMNO materials as described herein significantly improves the stability of the materials in half-cells and full-cells, and further improves cycle performance and capacity retention performance.

[0040] In a preferred embodiment, the silicon modification is SiO2 modification or includes SiO2 modification. Therefore, the modification includes SiO2 and is preferably composed of SiO2. Depending on the coating method, the modification may also consist of Li2SiO3 and / or Na2SiO3, other phases or mixtures thereof, or include Li2SiO3 and / or Na2SiO3, other phases or mixtures thereof. Using the methods described below, Si can be uniformly dispersed on the surface of the LNMO material, resulting in uniform particles with small differences in particle size and Si content.

[0041] Since SiO2 (or, alternatively, Li2SiO3 and / or Na2SiO3) is a non-conductive material, the amount of SiO2 present in the LNMO material of this invention is limited, and is typically 0.1 to 4.0 wt%, and preferably 0.5 wt% to 3.0 wt%, based on the weight of the LNMO material. Most preferably, the amount of SiO2 is 0.5 to 2.0 wt%, such as 0.5 to 1.5 wt%, based on the weight of the LNMO material. If the amount of SiO2 exceeds the upper limit, the conductivity of the material may decrease, leading to a decline in the electrochemical performance of the coated sample. If the amount of SiO2 is below the lower limit, the cycling performance and stability of the material may not be enhanced, and the desired effect may not be achieved.

[0042] Alternatively, the amount of silicon present in the LNMO material of the present invention can be calculated as the molar ratio of silicon to the transition metals nickel and manganese. Therefore, the molar ratio of Si / (Ni+Mn) is preferably 0.0005-0.03, more preferably 0.0008-0.015, and even more preferably 0.0015-0.01. The elemental content and molar ratio can be analyzed and calculated using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0043] The present invention has unexpectedly discovered that the size and shape of silicon-modified particles can be advantageously controlled by calcination temperature and the amount of silicon present in the silicon-modified material. Since silicon significantly increases crystallite growth, particle size and morphology can be varied and controlled based on the amount of silicon. Furthermore, silicon is believed to stabilize particle integrity, thereby achieving improved material stability.

[0044] from Figure 2 It is evident that higher SiO2 content results in larger crystal sizes. Therefore, based on the total weight of the LNMO material, using more than 0.5% by weight of SiO2 will result in secondary particles consisting of a smaller number of larger crystals, while less than 0.5% by weight of SiO2 will result in secondary particles consisting of a larger number of smaller (primary) crystals. Thus, the properties of silicon-modified materials can be advantageously controlled by the amount of SiO2 in the silicon-modified material, preferably more than 0.5% by weight.

[0045] The large, spherical secondary particles of the material of this invention result in high tap density and low specific surface area. The low specific surface area of ​​the silicon-modified LNMO of this invention can further improve cycle stability by reducing oxidative decomposition of the electrolyte and dissolution of metal ions from the cathode material, forming a more stable LNMO / electrolyte interface. Furthermore, the particulate material exhibits high particle density and low porosity. (From the cross-section of the material of this invention...) Figure 5 (d) Low porosity is clearly visible.

[0046] Therefore, as determined by Brunauer-Emmett-Teller (BET) surface area analysis, the specific surface area of ​​LNMO microparticles is preferably 0.1 to 0.5 m². 2 / g.

[0047] The tap density of the LNMO microparticle material according to the present invention is typically higher than 2.0 g·cm³. -3 Furthermore, it can achieve a value close to the theoretical maximum value for the packing of spherical particles of the same size, approximately 3.3 g·cm³. -3 Furthermore, depending on the particle size distribution, it can be even higher. Therefore, as determined according to ASTM B527-20, the tap density of the particulate material of the present invention is preferably 2.2 to 3.0 g·cm³. -3 More preferably 2.4 to 2.8 g·cm³ -3 The optimal value is approximately 2.6 g·cm³. -3 .

[0048] The silicon-modified LNMO material of the present invention can be advantageously used as a stable and high-capacity cathode material in Li-ion batteries.

[0049] Method for manufacturing silicon-modified LNMO particulate materials

[0050] The silicon-modified particulate LNMO material of the present invention can be obtained by mixing a particulate LNMO precursor material with a silicon (Si) source and then calcining it. The silicon source can also be referred to as a "coupling agent" or "surface modifier." In one embodiment, the material is obtained by a method in which only one coupling agent (surface modifier) ​​is used, preferably by a method in which only a Si source, i.e., a Si-containing compound, is used as the coupling agent (i.e., the surface modifier). In particular, the material is obtained by a method that does not involve any coupling agent or surface modifier that does not meet the conditions of the Si source. The method can be carried out by a wet method, i.e., a solution-based method, and by a semi-dry (initial wet) method in which only a small amount of solvent is used. Conversely, in the absence of a solvent, a dry method using nanoscale SiO2 materials generally will not yield uniform silicon modification of the LNMO particles.

[0051] In the wet process, the Si source is typically provided as a solution, preferably as an organosilicate solution, which is mixed with a solution or slurry of the LNMO precursor in a solvent. The wet process typically includes steps (a) to (d):

[0052] (a1) Mix the particulate LNMO precursor with an organic solvent or an aqueous solvent;

[0053] (a2) Provides a solution of an organosilicone ester in an organic solvent or an aqueous solvent, preferably a solution consisting of one or more solvents and an organosilicone ester or substantially a solution consisting of one or more solvents and an organosilicone ester;

[0054] (b) Mix the LNMO precursor with a solution of an organosilicate, such as an alkyl silicate;

[0055] (c) Remove the organic or aqueous solvent to obtain a dry mixture;

[0056] (d) The mixture is calcined in an oxygen-containing atmosphere at a temperature of 850°C to 1100°C to form silicon-modified LNMO microparticles.

[0057] The semi-dry process typically includes the following steps (a) to (d):

[0058] (a1) Provides particulate LNMO precursors in powder form;

[0059] (a2) Provides an organosilicone ester, such as an alkyl silicate ester, in an organic solvent or an aqueous solvent, wherein the organosilicone ester solution is preferably a solution consisting of a solvent and an organosilicone ester or substantially a solution consisting of a solvent and an organosilicone ester;

[0060] (b) While mixing, the organosilicate solution is added to the LNMO precursor;

[0061] (c) Remove the organic or aqueous solvent to obtain a dry mixture;

[0062] (d) The mixture is calcined in an oxygen-containing atmosphere at a temperature of 850°C to 1100°C to form silicon-modified LNMO microparticles.

[0063] There are no particular limitations on the organosilicone ester, which can be any silane coupling agent known in the art, such as trimethoxysilane γ-methacrylate (KH-570). Preferably, the organosilicone ester is an alkyl silicate. The alkyl group of the alkyl silicate can be any alkyl group having 1-8 carbon atoms, such as methyl, ethyl, propyl and / or isopropyl. More preferably, the alkyl silicate is tetraethyl orthosilicate (TEOS).

[0064] The solvent used in steps (a1) and / or (a2) is typically ethanol or isopropanol, but may also be any solvent suitable for dissolving organosilicates, such as solvents suitable for dissolving TEOS. Since TEOS reacts rapidly with water, the solvent is typically an organic solvent, and ethanol is most preferably used. However, aqueous solvents, water, or mixtures of aqueous and organic solvents may also be used, provided the reaction conditions are adjusted accordingly. Therefore, in alternative embodiments, the solvent may be an aqueous solvent, or it may also be water.

[0065] In the wet process, the concentration of the alkyl silicate solution, such as TEOS solution, is typically from 15.0 g / L to 200 g / L, and preferably from 60 g / L to 120 g / L. Conversely, in the semi-dry process, the concentration of the alkyl silicate solution is typically from 3.0 g / L to 110 g / L, and preferably from 16 g / L to 55 g / L. If the concentration of the alkyl silicate solution is higher than these upper limits, uniform distribution of Si on the LNMO surface may not be achieved. If the concentration of the alkyl silicate solution is lower than these lower limits, the beneficial effects of improved rate stability and electrochemical performance may not be achieved.

[0066] Furthermore, in the wet process, the total amount of solvent used per dose of LNMO material is typically 3.0 to 8.0 l (solvent) / kg (LNMO), preferably 3.5 to 6.0 l / kg, and optimally about 4.0 l / kg.

[0067] In addition, in the semi-dry process, the total amount of solvent used per dose of LNMO material is typically 0.5 to 3.0 l (solvent) / kg (LNMO), preferably 0.6 to 2.0 l / kg, more preferably 0.8 to 1.5 l / kg, and the optimal amount is about 1 l / kg.

[0068] Steps (a) and (b) are typically performed at temperatures ranging from 0°C to 70°C, such as at room temperature of 20-25°C, or at temperatures ranging from 40°C to 60°C.

[0069] In the semi-dry process, an alkyl silicate solution is typically added dropwise to LNMO powder and mixed simultaneously to obtain a mud-like mixture, i.e., a semi-dry mixture.

[0070] Step (b) typically involves mixing the organosilicate and the LNMO precursor. Mixing can be carried out at the aforementioned temperatures, for example, with continuous stirring for 1–12 hours, such as 2–6 hours. In a semi-dry process, stirring can continue until the solvent, such as ethanol, is completely added.

[0071] In the wet process, the solvent is typically removed in step (c) by evaporation under atmospheric or reduced pressure, such as in a rotary evaporator, for example, at 100 to 400 mbar. Depending on the solvent used, solvent removal is typically carried out at room temperature, such as 20-25°C, or at elevated temperatures, such as 30°C to 80°C.

[0072] Drying is routinely carried out at a temperature above the boiling point of the solvent used in the method. When ethanol or isopropanol is used as the solvent, drying is typically carried out at a temperature of 80°C to 150°C, for example, 100°C to 120°C, until complete removal of the solvent is achieved.

[0073] In a further preferred embodiment, the method further includes a pre-calcination step, in which the mixture obtained in step (b) is treated at a temperature of 400°C to 700°C for 2-8 hours. The pre-calcination temperature is typically lower than the temperature used in the subsequent calcination step (d).

[0074] The oxygen-containing atmosphere in step (d) is usually air, but it can also be any oxygen-containing atmosphere, including pure oxygen.

[0075] Calcination (step (d)) is typically carried out at 850°C to 1100°C, preferably at 850°C to 1000°C, and more preferably at about 900°C. During the heat treatment, LNMO crystallizes, and alkali metal silicates may decompose and react with the LNMO surface to achieve silicon modification. It has been unexpectedly discovered that the size and shape of the silicon-modified particles can be advantageously controlled using the calcination temperature. Furthermore, the growth of primary crystals with specific shapes during the heat treatment results in excellent electrochemical performance. Figure 2It is evident that higher calcination temperatures result in larger crystal sizes. Therefore, calcination temperatures between 900°C and 1100°C will produce secondary particles consisting of a smaller number of larger crystals; while temperatures below 900°C, such as 850°C to below 900°C, will result in secondary particles consisting of a larger number of smaller (primary) crystals. Thus, the properties of silicon-modified materials can be advantageously controlled using calcination temperature.

[0076] Temperatures above 900°C can lead to the formation of oxygen-deficient phases. These oxygen-deficient phases often contain undesirable amounts of NiO or Li. x Ni 1-x O (x is typically 0 to 0.1), indicating partial decomposition of LNMO, which may result in lower capacity of the generated particulate material. Subsequent annealing at lower temperatures, such as 600°C to 800°C, preferably 650°C to 750°C, for example at about 700°C, can lead to oxygen reintegration into the lattice, as well as the NiO phase or Li. x Ni 1-x The reintegration of the O phase into LNMO with the P4332 space group results in a larger capacity. Furthermore, as mentioned above, LNMO with the Fd-3m space group can form a Ni-deficient phase. Therefore, an annealing step following the calcination step is likely desirable.

[0077] Calcination is usually carried out for 2 to 24 hours, preferably 6 to 20 hours, and most preferably 8 to 16 hours.

[0078] In an alternative embodiment, the method of the present invention relates to a lithium-free (Li) precursor material mixed with a silicon source as described above. In this embodiment, the mixture of the lithium-free precursor material and the silicon source is subsequently treated with a lithium (Li) source.

[0079] Therefore, this alternative method for manufacturing silicon-modified lithium nickel manganese oxide (LNMO) particulate materials typically includes the following steps:

[0080] (a) A solution of a nickel-manganese particulate precursor material with an alkyl silicate in an organic solvent or an aqueous solvent, preferably consisting of one or more organic solvents or aqueous solvents and an organosilicone, or substantially consisting of one or more organic solvents or aqueous solvents and an organosilicone.

[0081] (b) Remove the organic or aqueous solvent to obtain a dry mixture;

[0082] (c) Add a lithium source (e.g., lithium hydroxide and / or lithium carbonate) to the dried mixture obtained in step (b); and

[0083] (d) The mixture is calcined in an oxygen-containing atmosphere at a temperature of 850°C to 1100°C to form silicon-modified LNMO microparticles.

[0084] In this embodiment, a lithium-free precursor material can be used. The (typically lithium-free) nickel-manganese precursor material may contain transition metals, i.e., nickel and manganese-containing carbonates, oxides, or hydroxides, such as nickel-manganese carbonates, nickel-manganese oxides, or nickel-manganese hydroxides, which may contain additional elements as described above. The precursor material can be obtained substantially by methods as described herein, such as spray drying, hydrothermal methods, or co-precipitation. The precursor material is mixed with a silicon source as described above. The resulting mixture is then mixed with a lithium source, such as lithium carbonate or lithium hydroxide, and calcined as described above. Therefore, for steps (c) and (d), the above description of the method of the present invention for obtaining Si-modified particulate material using a lithium-containing LNMO precursor material is applied in the same manner to this alternative embodiment using a (typically lithium-free) precursor, wherein the Li source is added only in a subsequent step after mixing the precursor material with the Si source. Furthermore, an additional heat treatment step may be performed after step (b), typically carried out at a temperature in the range of 300-700°C for 4-12 hours.

[0085] Preparation of LNMO precursor materials

[0086] There are no particular limitations on the LNMO precursor materials used in the above methods, and they can be obtained by methods described in the art, such as spray drying, hydrothermal methods, or coprecipitation. Coprecipitation is a feasible commercial method with benefits such as scalability, allowing control over particle size and morphology, and low cost, and is therefore preferred for the preparation of LNMO precursor materials.

[0087] In addition to these methods, combinatorial methods are described, in which a precursor, such as a transition metal carbonate, oxide, or hydroxide, is prepared by co-precipitation and then reacted with a stoichiometric amount of a lithium compound to generate the final product. Co-precipitation can be carried out with or without an additional cryogenic heating step, typically at temperatures between 300 and 600°C. Such a cryogenic heating step may be desirable for the formation of oxides. In lithium-ion battery materials, co-precipitation is currently widely used to prepare transition metal hydroxide precursors. However, alternatively, co-precipitation using carbonate precursors can be used.

[0088] For example, LNMO precursor materials can be obtained by batch or continuous co-precipitation methods.

[0089] For example, DE102023116756.1 describes a continuous co-precipitation method. In a first method step, an aqueous solution of a transition metal salt is continuously mixed with an aqueous solution of a carbonate in a continuous stirred tank reactor in the presence of an aqueous solution of an organic additive. Continuous mixing results in the continuous precipitation of the transition metal carbonate in the reactor. Therefore, the precipitated transition metal carbonate exists in the reactor as a solid suspension and can be continuously removed.

[0090] In a preferred embodiment, the co-precipitation method includes the following steps:

[0091] (i) Provide a solution containing ammonia, manganese salt and nickel salt to obtain a nickel manganese hydroxide precursor.

[0092] (ii) Mix the nickel-manganese hydroxide precursor with lithium hydroxide, and

[0093] (iii) Calcine at 400°C to 900°C for 6-20 hours in an oxygen-containing atmosphere.

[0094] There are no particular limitations on the manganese and / or nickel salts, and any salt can be sufficient to be water-soluble as a solution under the reaction conditions applied during the coprecipitation process. Typically, at least one of the manganese and nickel salts is a nitrate or a sulfate, with nitrates being particularly preferred.

[0095] Nickel and manganese salts are typically used in a specific ratio to achieve a Mn / Ni stoichiometry of 4:1 to 2:1, such as about 3:1. Alternatively, nickel and manganese salts are typically used in a specific ratio to achieve a Ni ratio of 4:1 to 2:1. 0.5-x Mn 0.5+x The stoichiometry, where x is between 0 and 0.6.

[0096] Typical methods include LNMO precursor materials, such as those derived from nickel manganese hydroxides, for example, Ni 0.25 Mn 0.75The hydroxide precursor obtained from (OH)₂ is impregnated with LiOH, such as LiOH·H₂O, and heated at a temperature of 400°C to 700°C, for example, about 450°C, for 2-10 hours, such as about 6 hours, and is referred to as an LNMO precursor in the method for manufacturing silicon-modified LNMO materials. In a preferred embodiment, an alkyl silicate, such as TEOS, is provided as an ethanol solution and added to the LNMO material. Preferably, TEOS is the only surface modifier added to the LNMO material. The material mixture can be heated to 700-1100°C, more preferably at about 850°C for 6-16 hours, such as about 12 hours. Furthermore, a typical method preferably includes a two-step heat treatment. In other words, a typical method preferably does not include any additional heating steps, i.e., heat treatment, other than the two steps defined above (heating at a temperature of 400°C to 700°C and heating at a temperature of 700-1100°C).

[0097] The LNMO precursor material obtained by the above method is preferably a particulate material containing D 50 The particle size is 4 µm to 30 µm, preferably 7 µm to 20 µm spherical particles.

[0098] Therefore, on the other hand, the present invention provides a silicon-modified, such as SiO2-modified LNMO material, which can be obtained by the methods described herein, preferably by the co-precipitation method described herein.

[0099] Attached Figure Description

[0100] Figure 1 : A schematic diagram of silicon-modified LNMO secondary particles, which are composed of crystals and microcrystals.

[0101] Figure 2 SEM images of silicon-free LNMO (SF1-SF3) and silicon-modified LNMO (W1-W9) materials with different primary crystal sizes obtained under different method conditions.

[0102] Figure 3 XRD patterns of Si-free LNMO (SF2) and silicon-modified LNMO (W5) materials.

[0103] Figure 4 SEM images and elemental mappings of (a) Si-free LNMO (SF2) and (bc) silicon-modified LNMO (W5).

[0104] Figure 5 SEM images of silicon-modified LNMO materials (W4-W6) with different primary crystal sizes and cross-sections of Si-LNMO (W6) secondary particles.

[0105] Figure 6 Si-free LNMO (SF2) and silicon-modified LNMO (W5) in half-cell (LNMO relative to Li / Li) + Comparison of rate performance in LNMO (SF2) and Si-LNMO (W5): (a) Rate performance, (b) Cyclic performance comparison, (cd) Constant current charge / discharge curves of Si-free LNMO (SF2) and Si-LNMO (W5).

[0106] Figure 7 Comparison of the cycling performance of Si-free LNMO (SF2) and silicon-modified LNMO (W5) in a full-cell configuration (LNMO vs. graphite) at room temperature (25°C).

[0107] Figure 8 Cycling of Si-free LNMO (SF2) and silicon-modified LNMO (W5) at elevated temperatures (45°C) in a full-cell configuration (LNMO versus graphite).

[0108] Figure 9 In a half-cell (LNMO relative to Li / Li) + The graph shows a comparison of the rate performance of Si-free LNMO (SF2) and Si-modified LNMO using wet coating (W5) and semi-dry coating (SD1) methods, respectively.

[0109] Figure 10 Comparison of charge / discharge curves of Si-modified LNMO using wet coating (W5) and semi-dry coating (SD1).

[0110] Figure 11 A graphical comparison of the cycling performance of Si-free LNMO (SF2) and Si-modified LNMO using wet coating (W5) and semi-dry coating (SD1) methods in a full cell (LNMO versus graphite).

[0111] Figure 12 SEM detailed images of grain boundaries in silicon-modified LNMO (W5) (a)-(c) and element mapping in the detailed images (d)-(g).

[0112] Figure 13 Silicon-modified, non-stoichiometric LNMO material LiNi 0.45 Mn 1.55 SEM image of O4. Example

[0113] The present invention will be further illustrated and described below through non-limiting experimental embodiments.

[0114] The following lists the acronyms for Si-free LNMO materials and Si-modified materials synthesized using wet coating and semi-dry methods, as described in the examples below. The numbers next to the acronyms refer to different samples synthesized using similar methods but under different synthesis conditions (temperature or degree of Si modification).

[0115] Methods / Materials acronym sample Si-free LNMO SF SF1-SF3 wet coating method W W1-W9 Semi-dry method SD SD1

[0116] Example 1 - Precursor Synthesis

[0117] High-density LiNi was synthesized using a two-step method. 0.5 Mn 1.5 O4 (LNMO): (1) Precursor synthesis; (2) Precursor lithiation. First, the precursor Ni was synthesized in a continuously stirred reactor (CSTR) using a co-precipitation technique. 0.25 Mn 0.75 (OH)₂. This involves using an aqueous solution containing ammonia, nickel nitrate, and manganese nitrate, maintaining a 3 / 1 Mn / Ni ratio. Co-precipitation yields dense, micron-sized spherical particles. Subsequently, the synthesized precursor is mixed with lithium hydroxide and subjected to low-temperature annealing at 450°C for 6 hours in ambient air. This LNMO precursor material is then used to prepare Si-free LNMO and Si-modified LNMO materials.

[0118] Example 2 - Silicon Treatment

[0119] 2.1 Wet Coating Method

[0120] First, 90 mL of ethanol was transferred to a beaker (solution 1) and heated to 50°C with continuous stirring. Then, 15 g of LNMO precursor was added to solution 1. Here, LNMO precursor refers to precursor obtained by mixing Ni... 0.25 Mn 0.75LNMO material was synthesized by heat treatment of (OH)₂ precursor and LiOH at 450 °C for 6 h. Simultaneously, 30 mL of ethanol was added to another beaker (solution 2) at 50 °C and stirred for 30 min. Then, tetraethyl orthosilicate (TEOS) corresponding to the target amount of Si in Si-LNMO was added to solution 2, and the mixture was stirred for another 30 min. Finally, the TEOS solution (solution 2) was added dropwise to solution 1. The temperature was raised to 60 °C, and the LNMO / TEOS was stirred for approximately 6 h. The solution was then transferred to a rotary evaporator (Büchi) to remove the ethanol solution. The rotary evaporator water bath temperature was set to 60 °C, and a pressure of 350 mbar was applied to remove the ethanol. The LNMO / TEOS was then transferred to a drying oven set at 120 °C overnight. Finally, LNMO / TEOS was heat-treated at different temperatures (850 °C, 900 °C, and 1000 °C) to synthesize Si-LNMO material. For Si-free LNMO materials, LNMO is heat-treated only at 850℃, 900℃ and 1000℃.

[0121] 2.2 Semi-dry method (initial wet method)

[0122] First, an ethanol solution of TEOS was prepared by adding tetraethyl orthosilicate (TEOS) to ethanol and stirring continuously at 50°C for 30 minutes, resulting in a TEOS solution with a concentration of approximately 35 g / L. The amount of TEOS was adjusted to 18 to 52 g / L to meet the silicon (Si) content required for Si-modified LNMO materials. Furthermore, the total solvent used for each volume of LNMO material was 1 L / kg. Simultaneously, 15 grams of LNMO precursor material was placed in a mortar and pestle. Here, the LNMO precursor refers to the precursor obtained by mixing Ni... 0.25 Mn 0.75 LNMO material was synthesized by heat treatment of (OH)₂ precursor with LiOH at 450 °C for 6 h. Subsequently, a TEOS / ethanol solution was carefully added dropwise to the dried LNMO material under continuous stirring to ensure uniform distribution of TEOS on the LNMO particles. This process yielded a clay-like material. The LNMO / TEOS mixture was then dried overnight in an oven at 120 °C to remove the solvent. Finally, LNMO / TEOS was heat-treated at different temperatures (850 °C, 900 °C, and 1000 °C) to synthesize Si-modified LNMO material, achieving the desired modification. For Si-free LNMO material, LNMO was heat-treated only at 850 °C, 900 °C, and 1000 °C.

[0123] Example 3 - XRD Measurement of Si-Modified LNMO Material

[0124] The LNMO materials prepared in Examples 2.1 and 2.2 were analyzed by XRD measurement and SEM elemental mapping.

[0125] Figure 3 The illustration shows the XRD patterns of Si-free LNMO (SF2) and silicon-modified LNMO materials. Both can be identified as Fd3̅m cubic phases, also referred to in the literature as disordered spinel. Small amounts of NiO or Li were detected in both materials. x Ni 1-x O, which is usually found in disordered LNMO materials due to the absence of nickel or oxygen.

[0126] Table 1 lists the ICP results for Si-free LNMO (SF2) and Si-LNMO materials (W5), confirming their near-stoichiometric composition (Mn / Ni≈3 / 1). Both Si-free LNMO and Si-LNMO materials exhibit a spherical morphology with micron-sized secondary particles, and their D... 50 They are approximately 14 µm and 16.5 µm respectively. Figure 4 ).

[0127] Table 1: ICP analysis results of Si-free LNMO and Si-modified LNMO (Si-LNMO).

[0128]

[0129] Elemental mapping confirmed the uniform distribution of Si on the particle surface. The grain size of silicon-free LNMO was approximately 200 nm, while that of Si-modified LNMO was 285 nm (which could be controlled), with a slight increase in lattice parameters and cell volume. Refined parameters and grain size are listed in Table 2.

[0130] Table 2: Rietveld refinement parameters and particle size distribution of Si-free LNMO and Si-modified LNMO (Si-LNMO).

[0131]

[0132] *Comparative materials for reference purposes

[0133] Furthermore, the primary particles of Si-LNMO transform into a well-defined (truncated) octahedral shape. Figure 4 , 5 It is known that it provides more stable surface-enhanced electrochemical properties. Figure 4 SEM images and elemental mappings of (a) Si-free LNMO and (b) Si-LNMO are shown. Furthermore, Figure 12This image shows grain boundaries in silicon-modified LNMO (W5) and the elemental distribution in the corresponding elemental maps (d)-(g). From the Si map (g), it is clear that Si aggregates at the grain boundaries and is able to form separate phases along these boundaries. Furthermore, the size of the primary crystals can be controlled by adjusting the synthesis conditions (calcination temperature and Si concentration). Figure 5 As shown, the physical and electrochemical properties of Si-LNMO can be controlled over a wide range.

[0134] The larger secondary particles result in a high tap density and a low specific surface area (0.2 m² g⁻¹ for Si-LNMO). The lower specific surface area of ​​Si-LNMO can further improve cycle stability by reducing oxidative decomposition of the electrolyte and dissolution of metal ions from the cathode material, thus forming a more stable LNMO / electrolyte interface.

[0135] In addition to the stoichiometric LNMO composition described above, the concept of this invention has also been validated in silicon-modified non-stoichiometric LNMO, particularly in the synthesis and testing of silicon-modified non-stoichiometric LNMO material LiNi. 0.45 Mn 1.55 O4. SEM images showing morphological features in non-stoichiometric materials, such as... Figure 13 As shown. More specifically, the primary particles clearly have a (truncated) octahedral shape.

[0136] Example 4 - Electrochemical Results

[0137] By measuring the half-cell (LNMO relative to Li / Li) + The rate performance, cycle performance, and constant current charge / discharge curves of the Si-modified LNMO materials prepared in Examples 2.1 and 2.2 were analyzed.

[0138] Figure 6 The figures illustrate a comparison of rate performance between Si-free LNMO and Si-LNMO. All electrochemical measurements were performed using standard electrolyte LP30 (1M LiPF6 EC: DMC 1:1 wt%) without any stabilizing additives. Active material loading was 9-10 mg cm⁻¹. -2 All measurements were performed in a coin cell (CR2023) configuration. Lithium metal (450 µm) was used as the counter electrode, and two glass fiber sheets were used as the separator. 150 µl of electrolyte was used for all cells, and all half-cell measurements were performed at 25 °C.

[0139] Both materials exhibited nearly similar rate performance up to C / 2. However, at higher C rates, Si-LNMO demonstrated superior rate performance. At 5C and 10C, Si-LNMO exhibited discharge capacities of approximately 118 and 90 mAh g⁻¹, respectively. In contrast, Si-free LNMO retained only 103 and 77 mAh g⁻¹ at 5C and 10C, respectively. Furthermore, compared to Si-free LNMO, Si-LNMO exhibited superior cycling performance at 1C / 1C. Both Si-free LNMO and Si-LNMO exhibited capacities of approximately 118 and 123 mAh g⁻¹, respectively. After 140 cycles, Si-free LNMO and Si-LNMO showed capacity retention of approximately 94% and 98%, respectively. The charge / discharge curves indicate that Si-LNMO has a slightly higher Mn content. 3+ Content. Additionally, compared to silicon-free LNMO, Si-LNMO exhibits a lower overpotential, especially at high C rates, which may be related to the improved kinetics resulting from silicon modification.

[0140] To compare the effect of silicon modification on the long-term stability of full cells, the material was also tested in a full-cell configuration (LNMO / graphite). Full cells were also tested in a coin cell (CR2032) configuration. As with the half-cell tests, measurements were performed using the conventional electrolyte LP30 (1M LiPF6 EC: DMC 1:1 wt%). The active material loading at the LNMO cathode was 18–19 mg cm⁻¹. -2 Graphite was used as the negative electrode, with a content of approximately 8.9 mg cm⁻¹. -2 (3 mAh cm) -2 Active material loading was performed. The N / P ratio was set to approximately 1.2. Additionally, two glass fibers were used as separators, and all cells used 150 µl of electrolyte.

[0141] Cyclic stability was analyzed at 25°C and 45°C. Figure 7 The cycling performance of Si-free LNMO and Si-LNMO at 25 °C was compared. The results show that after 500 cycles, compared to Si-free LNMO,

[0142] Si-LNMO exhibited better capacity retention. Specifically, after 500 cycles, Si-free LNMO and Si-LNMO retained approximately 75.14% and 84.5% of their initial capacity, respectively.

[0143] LNMO / graphite full cells were also tested at elevated temperatures (45°C). During the initial cycling period, both materials exhibited similar capacity decay due to severe electrolyte decomposition and consumption of active lithium. However, as... Figure 8As shown, Si-LNMO exhibits slower capacity decay during further cycling. Notably, Si-LNMO demonstrates excellent cycling stability at 45°C. Si-free and Si-LNMO cycles for 96 and 196 cycles, respectively, achieving 80% state of equilibrium (SOH). Furthermore, Si-LNMO exhibits higher coulombic efficiency (CE), which directly impacts capacity retention. It is anticipated that Si modification hinders direct contact between the LNMO interface and the electrolyte, thereby reducing electrolyte decomposition (side reactions) and ultimately improving capacity retention.

[0144] Figure 9 This paper compares the rate performance of Si-free LNMO (SF2), Si-modified LNMO synthesized using wet coating (W5), and semi-dry coating (SD1). Compared to Si-free LNMO, both the wet-coating and semi-dry methods showed enhanced performance of the Si-modified LNMO. All materials exhibited very similar performance up to C / 2, yielding a discharge capacity of approximately 126 mAh g⁻¹; however, at higher C-rates, the wet-coating and semi-dry Si-modified materials outperformed the Si-free LNMO. Considering the standard deviation of more than three tested cells, the semi-dry and wet-coating materials performed identically. The wet-coating and semi-dry Si-modified materials maintained approximately 120 mAh g⁻¹ at 5C and 10C, respectively. -1 and 90 mAh g -1 The capacity is [missing information], while the silicon-free material only maintains approximately 100 mAh g [missing information]. -1 and 78 mAh g -1 The discharge capacity. Furthermore, from Figure 9 The cycling data in (b) clearly show that, compared with Si-modified LNMO materials, Si-free LNMO materials exhibit lower capacity and faster capacity decay.

[0145] Figure 10 The charge / discharge curves of Si-modified LNMO materials synthesized using a wet coating method (W5) and a semi-dry coating method (SD1) were compared. The Si-modified LNMO materials synthesized using both methods exhibited almost identical charge / discharge curves at different C-rates. The capacity provided by the 4.0 V plateau was also similar for both materials, which is attributed to the presence of Mn in the LNMO materials. 3+ The amount is related. Since both materials were synthesized under similar conditions and both exhibited similar low-voltage (4.0 V) discharge capacities, they appear to have similar Mn content. 3+ .

[0146] Figure 11The performance of full cells (LNMO vs. graphite) using Si-free LNMO (SF2), wet-coated LNMO (W5), and semi-dry LNMO (SD1) methods was compared. In the full cells, the wet-coated Si-modified LNMO exhibited the best capacity retention. Si-free LNMO showed the fastest capacity decay. However, compared to Si-free LNMO, the semi-dry Si-modified LNMO showed significantly improved capacity retention, but still lower than the wet-coated method. The optimal capacity retention of the wet-coated Si-modified LNMO compared to the semi-dry method is likely due to the uniform coating on the LNMO material. After 1000 cycles using a C / 2-1C cycling scheme, the Si-free LNMO and the semi-dry Si-modified LNMO retained 71% and 75% of their initial discharge capacity, respectively.

[0147] In summary, experiments demonstrate that Si modification of LMNO materials significantly improves their stability in both half-cells and full-cells. At elevated temperatures (45°C), the full-cell configuration (LNMO / graphite) shows substantial improvement, a key criterion for LMNO stability evaluation. Therefore, the novel Si-modified LNMO material according to the present invention exhibits significantly enhanced stability due to silicon treatment, specific primary particle shape, and design. Compared to Si-free LNMO, Si-modified LNMO demonstrates superior rate performance, long-term cycling in full-cell (LNMO / graphite) conditions, and a relatively stable LNMO / electrolyte interface.

Claims

1. A lithium nickel manganese oxide (LNMO) particulate material, wherein the LNMO particulate material comprises secondary particles. The secondary particles are composed of a large number of crystals, and the crystals are composed of a large number of microcrystals. The D of the secondary particles, as measured by laser diffraction according to ISO 13320:2020, is... 50 The particle size ranges from 4.0 µm to 25 µm, and The D of the crystal, as measured by scanning electron microscopy (SEM), is among them. 50 The particle size ranges from 0.5 µm to 7.0 µm, and wherein The LNMO microparticle material is silicon modified.

2. The LNMO particulate material of claim 1, wherein the secondary particles have a D 50 particle size of 5.0 pm to 20 pm.

3. The LNMO particulate material of claim 1 or 2, wherein the crystals have a D 50 particle size of 1.0 pm to 5.0 pm.

4. The LNMO microparticle material according to any one of the preceding claims, wherein the crystallite size is 180 nm to 400 nm, as measured by XRD Rietveld refinement.

5. The LNMO particulate material according to any one of the preceding claims, wherein the silicon modification comprises SiO2.

6. The LNMO particulate material according to any one of the preceding claims, wherein the molar ratio of Si / (Ni+Mn) is 0.0005-0.

03.

7. Use of the LNMO particulate material according to any one of the preceding claims as a positive electrode material in a lithium-ion battery.

8. A method for manufacturing silicon-modified lithium nickel manganese oxide (LNMO) particulate materials, the method comprising the following steps: (a) Mixing the LNMO microparticle precursor with a solution of alkyl silicate in an organic or aqueous solvent, (b) Remove the organic solvent or aqueous solvent to obtain a dry mixture. (c) The mixture is calcined in an oxygen-containing atmosphere at a temperature of 850°C to 1100°C to form silicon-modified LNMO particulate material.

9. The method according to claim 8, wherein the alkyl silicate is tetraethyl orthosilicate (TEOS).

10. The method according to claim 8 or 9, wherein the method further comprises a pre-calcination step of treating the mixture of step (b) at a temperature of 400°C to 700°C for 2 to 8 hours.

11. The method according to any one of claims 8-10, wherein the organic solvent is ethanol or isopropanol.

12. The method according to any one of claims 8-11, wherein the calcination step (c) is carried out at a temperature of 850°C to 1000°C for 6 h to 20 h.

13. The method according to any one of claims 8-12, wherein the mixing in step (a) is carried out at a temperature of 25°C to 60°C.

14. A silicon-modified LNMO material, which can be obtained by the method according to any one of claims 8-13.

15. The LNMO particulate material according to any one of claims 1-6, the use of the LNMO particulate material according to claim 7, the method according to any one of claims 8-13, or the silicon-modified LNMO material according to claim 14, wherein the LNMO particulate material is defined by the following formula: LiNi 0.5-x Mn 1.5+x O4, Where x is 0 to 0.1, preferably 0.01 to 0.06.

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