Lithium nickel-based composite oxides as positive electrode active materials for sulfide solid state rechargeable batteries

Abstract

The present invention relates to a positive electrode active material comprising Li, M 'and oxygen, where M' comprises Ni, Co, Mn, B, Q, where Q is an element other than Li, O, Ni, Co, Mn and B, and where the positive electrode active material has an enriched amount of B in a surface layer, and where the positive electrode active material comprises secondary particles comprising a plurality of primary particles having a low grain size.

Description

Technical Field

[0001] The present invention relates to a positive electrode active material for a solid-state battery pack, which contains Li, M', and O, where M' contains B. The present invention also relates to a method for manufacturing the positive electrode active material, a solid-state battery pack containing the positive electrode active material, and the use of the solid-state battery pack. Background Art

[0002] With the rapid progress in the development of small and lightweight electronic products, electronic devices, communication devices, etc., and the widespread emergence of the need for electric vehicles in terms of environmental issues, there is a demand for improving the performance of secondary battery packs used as power sources for these products. Among them, due to high energy density and high reference electrode potential, lithium secondary battery packs have attracted much attention as a high-performance battery pack.

[0003] During the charging process of a secondary battery pack, lithium ions are deintercalated from the cathode, transported through the electrolyte, and intercalated into the anode, while electrons are deintercalated from the cathode and injected into the anode through an external circuit (charger). During the use or discharge of the secondary battery pack, lithium ions are deintercalated from the anode, transported through the electrolyte, and intercalated into the cathode, while electrons flow through the external circuit to provide electrical work.

[0004] Commonly used cathode active materials are lithium transition metal oxides. During the charging and / or discharging of a lithium battery pack, the delithiated cathode active material reacts slowly with the non-aqueous electrolyte or solid electrolyte, resulting in a gradual degradation of the electrochemical performance of the lithium battery pack using such a cathode active material. It has been confirmed that coating the cathode active material with a metal such as B or Zr (i.e., applying a thin metal surface layer on the cathode active material, which results in an increase in the amount of the metal in the surface layer) causes the cathode active material to exhibit higher stability compared to its counterpart without the coating.

[0005] US 2020 / 0303720 A1 envisions a boron-coated positive electrode active material, which contains nickel, cobalt, and manganese in a ratio of 8:1:1, and is prepared by dry mixing the uncoated positive electrode active material with boron and then performing a heat treatment step at 300 °C for 5 hours.

[0006] Zhang et al. ((Adv. Energy Mater. 2020, 10, 1903778) describe a boron-coated positive electrode active material, which contains nickel, cobalt, and manganese in a ratio of 5:2:3, using a sol-gel method, in which triisopropyl borate is dissolved in ethanol, and then the uncoated positive electrode active material is dispersed in the solution, followed by removing the solvent and performing a subsequent heat treatment at 350 °C.

[0007] However, there is still a need to provide a positive electrode active material having an enriched amount of boron in the surface layer to improve the cycle efficiency of the resulting battery pack and / or reduce the polarization of the battery pack as much as possible.

[0008] One object of the present invention is to provide a positive electrode active material having an enriched amount of boron in the surface layer, which improves the cycle efficiency of the resulting battery pack.

[0009] Another object of the present invention is to provide a method for manufacturing the positive electrode active material.

[0010] Another object of the present invention is to provide a battery pack including the positive electrode active material.

[0011] Another object of the present invention is to provide the use of the battery pack. Summary of the Invention

[0012] In a first aspect, the object of the present invention is achieved by providing a positive electrode active material for a solid-state battery pack, the positive electrode active material including Li, M', and oxygen, wherein M' includes:

[0013] - Ni with a content of x, wherein 75.0 ≤ x < 100.0 mol% relative to M',

[0014] - Co with a content of y, wherein 0.0 ≤ y ≤ 15.0 mol% relative to M',

[0015] - Mn with a content of z, wherein 0.0 ≤ z ≤ 15.0 mol% relative to M',

[0016] - B with a content of b, wherein 0.01 ≤ b ≤ 1.5 mol% relative to M',

[0017] - Q with a content of q, wherein Q is an element other than Li, O, Ni, Co, Mn, and B, wherein 0.0 ≤ q ≤ 2.0 mol% relative to M', and,

[0018] - wherein x, y, z, b, and q are measured by ICP-OES,

[0019] - wherein x + y + z + b + q is 100.0 mol%,

[0020] wherein the positive electrode active material has an enriched amount of B in the surface layer, and

[0021] wherein the positive electrode active material includes secondary particles, and the secondary particles include a plurality of primary particles having a low grain size.

[0022] The present inventors have surprisingly found that the positive electrode active material of the present invention significantly improves the first discharge capacity of the battery pack, the cycling performance of the battery pack, and / or exhibits low polarization in a battery pack, particularly a sulfide solid-state battery pack.

[0023] Without wishing to be bound by any theory, the present inventors believe that the combination of an enriched amount of boron in the surface layer (i.e., the boron coating) and the positive electrode active material having a low grain size (i.e., secondary particles comprising primary particles having an average diameter between 100 nm and 400 nm) improves the first discharge capacity, enhances the cycling efficiency of the battery pack, and / or reduces the polarization in the battery pack.

[0024] Although boron-coated positive electrode active materials are already known in the art (see US 2020 / 0303720A1 or Zhang et al. (Adv. Energy Mater. 2020, 10, 1903778)), the present inventors are the first to report the synergistic effect of the boron coating with the low grain size of the positive electrode active material. US 2020 / 0303720 A1 or Zhang et al. (Adv. Energy Mater. 2020, 10, 1903778) does not disclose the crystalline size of the particles, nor does it describe or imply the synergistic effect of the boron coating with the low crystalline size of the particles.

[0025] In another aspect, the present invention provides a method for manufacturing the positive electrode active material.

[0026] In another aspect, the present invention provides a battery pack comprising the positive electrode active material.

[0027] In another aspect, the present invention provides the use of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 . XPS spectrum of the B1s peak of EX1.

[0029] Figure 2a . SEM image showing secondary particles of CEX3 comprising a plurality of primary particles, wherein the dashed line shows the region to be captured to obtain the average primary particle diameter.

[0030] Figure 2b . SEM image of CEX3 to obtain the average primary particle diameter. DETAILED DESCRIPTION

[0031] In the following detailed description, preferred embodiments are described in detail so that the present invention can be practiced. Although the present invention is described with reference to these specific preferred embodiments, it should be understood that the present invention is not limited to these preferred embodiments. On the contrary, the present invention includes numerous alternatives, modifications, and equivalents, as will become apparent from consideration of the following detailed description and the drawings.

[0032] As used herein and in the claims, the term "comprising" should not be construed as limited to the manners listed thereafter; it does not exclude other elements or steps. It should be construed as specifying the presence of the stated features, integers, steps, or components, but does not exclude the presence or addition of one or more other features, integers, steps, or components or groups thereof. Thus, the scope of the expression "a composition comprising components A and B" should not be limited to compositions consisting only of components A and B. This means that, for the purposes of the present invention, the only relevant components of the composition are A and B. Accordingly, the terms "comprising" and "including" encompass the more restrictive terms "consisting essentially of" and "consisting of".

[0033] As used herein and in the claims, the term "solid-state battery pack" refers to a battery or battery pack that includes only solid or substantially solid components such as solid electrodes (e.g., an anode and a cathode) and a solid electrolyte.

[0034] As used herein and in the claims, the term "positive electrode active material" (also referred to as cathode active material) is defined as a material that is electrochemically active in the positive electrode or cathode. The active material should be understood to be a material that is capable of capturing and releasing Li ions when subjected to a voltage change over a predetermined period of time.

[0035] In the context of the present invention, unless otherwise defined, the terms "solid" and "liquid" shall be considered to be solids and liquids under standard temperature and pressure conditions as defined by IUPAC. Herein, the boiling point and melting point shall be considered to be the boiling point and melting point under standard atmospheric pressure, i.e., at 101325 Pa.

[0036] Positive electrode active material

[0037] In a first aspect, the present invention relates to a positive electrode active material for a solid-state battery pack, which comprises Li, M', and oxygen, wherein M' comprises:

[0038] - Ni in an amount x, wherein 75.0 ≤ x < 100.0 mol% relative to M',

[0039] - Co in an amount y, wherein 0.0 ≤ y ≤ 15.0 mol% relative to M',

[0040] - Mn with a content of z, where 0.0 ≤ z ≤ 15.0 mol% relative to M',

[0041] - B with a content of b, where 0.01 ≤ b ≤ 1.5 mol% relative to M',

[0042] - Q with a content of q, where Q is an element other than Li, O, Ni, Co, Mn, and B, where 0.0 ≤ q ≤ 2.0 mol% relative to M', and,

[0043] - where x, y, z, b, and q are measured by ICP - OES,

[0044] - where x + y+ z + b + q = 100.0 mol%,

[0045] where the positive electrode active material has a B content B defined as b / (x + y + z + b), A ,

[0046] where the positive electrode active material has a B content B B ,where B B is determined by XPS analysis, where B B is expressed as the ratio of the mole fraction B measured by XPS analysis to the sum of the mole fractions of Ni, Mn, Co, and B,

[0047] where the ratio B B / B A > 40.0,

[0048] where the positive electrode active material comprises secondary particles, the secondary particles comprising a plurality of primary particles, and

[0049] where the primary particles have an average diameter between 100 nm and 400 nm, as determined by measuring the primary particle size in an image taken by SEM.

[0050] A preferred embodiment is the positive electrode active material of the present invention, where the content x of Ni ≥ 78.0 mol%, preferably x ≥ 80.0 mol%, more preferably x ≥ 82.0 mol%. In a preferred embodiment, the content x of Ni ≤ 98.0 mol%, preferably x ≤ 96.0 mol%, more preferably x ≤ 94.0 mol%. A more preferred embodiment is the positive electrode active material of the present invention, where the content x of Ni is between 78.0 mol% ≤ x ≤ 98.0 mol%, preferably between 80.0 mol% ≤ x ≤ 96.0 mol%, more preferably between 82.0 mol% ≤ x ≤ 94.0 mol%.

[0051] In a preferred embodiment, the positive electrode active material of the present invention has a Ni content x ≥ 78.0 mol%, preferably x ≥ 80.0 mol%, more preferably x ≥ 82.0 mol%. In a preferred embodiment, the Ni content x ≤ 90.0 mol%, preferably x ≤ 88.0 mol%, more preferably x ≤ 86.0 mol%. In a more preferred embodiment, the positive electrode active material of the present invention has a Ni content x in the range of 78.0 mol% ≤ x ≤ 90.0 mol%, preferably in the range of 80.0 mol% ≤ x ≤ 88.0 mol%, more preferably in the range of 82.0 mol% ≤ x ≤ 86.0 mol%.

[0052] In a preferred embodiment, the positive electrode active material of the present invention has a Ni content x ≥ 86.0 mol%, preferably x ≥ 88.0 mol%, more preferably x ≥ 90.0 mol%. In a preferred embodiment, the Ni content x ≤ 98.0 mol%, preferably x ≤ 96.0 mol%, more preferably x ≤ 94.0 mol%. In a more preferred embodiment, the positive electrode active material of the present invention has a Ni content x in the range of 86.0 mol% ≤ x ≤ 98.0 mol%, preferably in the range of 88.0 mol% ≤ x ≤ 96.0 mol%, more preferably in the range of 90.0 mol% ≤ x ≤ 94.0 mol%.

[0053] As those skilled in the art will understand, the amounts of Li and M' (preferably Li, Ni, Mn, Co, Q, and B) in the positive electrode active material are measured by inductively coupled plasma optical emission spectrometry (ICP-OES). For example, but not limited to this, an Agilent ICP 720-ES is used in the ICP-OES analysis.

[0054] In a preferred embodiment, the positive electrode active material of the present invention has a Co content y > 0.0 mol%, preferably y ≥ 2.0 mol%, more preferably y ≥ 3.0 mol%. In a preferred embodiment, the content y ≤ 13.0 mol%, preferably y ≤ 11.0 mol%, and more preferably y ≤ 9.0 mol%. In a preferred embodiment, the Co content is 0.0 mol% < y ≤ 13.0 mol%, preferably 2.0 mol% ≤ y ≤ 11.0 mol%, more preferably 3.0 mol% ≤ y ≤ 9.0 mol%.

[0055] A preferred embodiment is the positive electrode active material of the present invention, wherein the content z of Mn > 0.0 mol%, preferably z ≥ 1.0 mol%, more preferably z ≥ 2.0 mol%. In a preferred embodiment, the content z ≤ 10.0 mol%, preferably z ≤ 9.0 mol%, and more preferably z ≤ 8.0 mol%. In a preferred embodiment, the content of Mn is 0.0 mol% < z ≤ 10.0 mol%, preferably 1.0 mol% ≤ z ≤ 9.0 mol%, more preferably 2.0 mol% ≤ z ≤ 8.0 mol%.

[0056] As is known to those skilled in the art, the positive electrode active material of the present invention may contain impurities or be doped or coated, such that the overall positive electrode active material contains one or more elements other than Li, Ni, Mn, Co, B, and O, which is reflected in the parameter "Q" used herein. A preferred embodiment is the positive electrode active material containing Q according to the present invention, wherein Q is at least one element selected from the following: Al, Ti, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, V, W, Y, Zn, and Zr; preferably Al, Ti, Cr, Nb, S, Si, Y, Zr, and W; more preferably Al, Ti, Nb, Zr, and W.

[0057] A preferred embodiment is the positive electrode active material according to the present invention, wherein the content q of Q > 0.0 mol%, preferably q ≥ 0.25 mol%, more preferably q ≥ 0.5 mol%. In a preferred embodiment, the content q ≤ 1.75 mol%, preferably q ≤ 1.5 mol%, more preferably q ≤ 1.25 mol%. In a preferred embodiment, the content is 0.0 mol% < q ≤ 1.75 mol%, preferably 0.25 mol% ≤ q ≤ 1.5 mol%, more preferably 0.5 mol% ≤ q ≤ 1.25 mol%.

[0058] In certain preferred embodiments, the positive electrode active material is according to the present invention, wherein q = 0.0 mol%.

[0059] A preferred embodiment is the positive electrode active material of the present invention, wherein the content b of B satisfies b ≥ 0.1 mol%, preferably b ≥ 0.25 mol%, more preferably b ≥ 0.5 mol%. In a preferred embodiment, b ≤ 1.4 mol%, preferably b ≤ 1.3 mol%, more preferably b ≤ 1.2 mol%. In a preferred embodiment, 0.1 mol% ≤ b ≤ 1.4 mol%, preferably 0.25 mol% ≤ b ≤ 1.3 mol%, more preferably 0.5 mol% ≤ b ≤ 1.2 mol%.

[0060] A preferred embodiment is the positive electrode active material of the present invention, which has a Li / M' ratio, preferably a Li / (Ni + Mn + Co) ratio, greater than 0.90, preferably greater than 0.92, more preferably greater than 0.95. A preferred embodiment is the positive electrode active material of the present invention, which has a Li / M' ratio, preferably a Li / (Ni + Mn + Co) ratio, less than 1.10, preferably less than 1.08, more preferably less than 1.05. A preferred embodiment is the positive electrode active material of the present invention, which has a Li / M' ratio, preferably a Li / (Ni + Mn + Co) ratio, within the range of 0.90 - 1.10, preferably within the range of 0.92 - 1.08, more preferably within the range of 0.95 - 1.05. As those skilled in the art will understand, the Li / M' ratio, preferably the Li / (Ni + Mn + Co) ratio, is a molar ratio (mol / mol).

[0061] A preferred embodiment is the positive electrode active material of the present invention, which has a carbon content higher than 0.015 wt%, preferably higher than 0.020 wt%, more preferably higher than 0.030 wt% based on the total weight of the positive electrode active material. A preferred embodiment is the positive electrode active material of the present invention, which has a carbon content lower than 0.090 wt%, preferably lower than 0.075 wt%, more preferably lower than 0.060 wt% based on the total weight of the positive electrode active material. A preferred embodiment is the positive electrode active material of the present invention, which has a carbon content in the range of 0.015 wt.% to 0.090 wt.%, preferably in the range of 0.020 wt.% to 0.075 wt.%, more preferably in the range of 0.030 wt.% to 0.060 wt% based on the total weight of the positive electrode active material. As those skilled in the art should understand, the carbon content of the positive electrode active material of the present invention is measured by a carbon analyzer. For example, but not limited to this, a Horiba Emia-Expert carbon / sulfur analyzer can be used to measure the carbon content C.

[0062] A highly preferred embodiment is the positive electrode active material according to the present invention, which has the formula (I):

[0063] Li w2 Ni x2 Co y2 Mn z2 B b2 Q2 q2 O2 (I)

[0064] where 0.90 ≤ w2 ≤ 1.10, preferably 0.92 ≤ w2 ≤ 1.08, more preferably 0.95 ≤ w2 ≤ 1.05;

[0065] where 0.78 ≤ x2 ≤ 0.98, preferably 0.80 ≤ x2 ≤ 0.96, more preferably 0.82 ≤ x2 ≤ 0.94;

[0066] where 0.0 ≤ y2 ≤ 0.13, preferably 0.02 ≤ y2 ≤ 0.11, more preferably 0.03 ≤ y2 ≤ 0.09;

[0067] where 0.0 < z2 ≤ 0.10, preferably 0.01 ≤ z2 ≤ 0.09, more preferably 0.02 ≤ z2 ≤ 0.08;

[0068] where 0.001 ≤ b2 ≤ 0.014, preferably 0.0025 ≤ b2 ≤ 0.013, more preferably 0.005 ≤ b2 ≤ 0.012;

[0069] where 0.0 ≤ q2 ≤ 0.0175, preferably 0.0 ≤ q2 ≤ 0.015, more preferably 0.0 ≤ q2 ≤ 0.0125, and most preferably q2 is about 0.0;

[0070] where x2 + y2 + z2 + b2 + q2 = 1.00; and

[0071] where Q2 is an element other than Li, O, Ni, Co, Mn, and B.

[0072] As is known to those skilled in the art, the positive electrode active material of the present invention may contain impurities or be doped or coated, resulting in the overall positive electrode active material containing one or more elements other than Li, Ni, Mn, Co, B, and O, which is reflected in the parameter "Q2" used herein. A preferred embodiment is a positive electrode active material containing Q2 according to the present invention, where Q2 is at least one element selected from the following: Al, Ti, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, V, W, Y, Zn, and Zr; preferably Al, Ti, Cr, Nb, S, Si, Y, Zr, and W; more preferably Al, Ti, Nb, Zr, and W.

[0073] Surface layer

[0074] In the context of the present invention, the positive electrode active material is according to the present invention, where the positive electrode active material has a B content B defined as b / (x + y + z + b) A , where the positive electrode active material has a B content B B , where B B is determined by XPS analysis, where B B is expressed as the ratio of the mole fraction B measured by XPS analysis to the total mole fraction of Ni, Mn, Co, and B, where the ratio B B / B A > 40.0.

[0075] A more preferred embodiment relates to the positive electrode active material of the present invention, where the ratio B B / B A > 45.0, preferably the ratio B B / B A > 50.0, more preferably the ratio B B / B A > 60.0, even more preferably the ratio B B / BA > 70.0, most preferably the ratio B B / B A > 90.0.

[0076] A more preferred embodiment relates to the positive electrode active material of the present invention, wherein the ratio B B / B A < 1000.0, preferably the ratio B B / B A < 500.0, more preferably the ratio B B / B A < 200.0, even more preferably the ratio B B / B A < 150.0, most preferably the ratio B B / B A < 125.0.

[0077] A more preferred embodiment relates to the positive electrode active material of the present invention, wherein the ratio B B / B A is in the range of 45.0 to 1000.0, preferably the ratio B B / B A is in the range of 50.0 to 200.0, more preferably the ratio B B / B A is in the range of 60.0 to 125.0.

[0078] In certain preferred embodiments of the present invention, the positive electrode active material is according to the present invention,

[0079] ● wherein the content x of Ni is between 78.0 mol% ≤ x ≤ 90.0 mol%, preferably 80.0 mol% ≤ x ≤ 88.0 mol%, more preferably 82.0 mol% ≤ x ≤ 86.0 mol%, and

[0080] ● wherein the ratio B B / B A is in the range of 40.0 to 1000.0, preferably the ratio B B / B A is in the range of 45.0 to 100.0, more preferably the ratio B B / B A is in the range of 50.0 to 70.0.

[0081] In certain preferred embodiments of the present invention, the positive electrode active material is according to the present invention,

[0082] ● wherein the content x of Ni is between 86.0 mol% ≤ x ≤ 98.0 mol%, preferably 88.0 mol% ≤ x ≤ 96.0 mol%, more preferably 90.0 mol% ≤ x ≤ 94.0 mol%, and

[0083] ● wherein the ratio B B / B A is in the range of 60.0 to 1000.0, preferably the ratio B B / B A is in the range of 70.0 to 200.0, more preferably the ratio B B / B A is in the range of 90.0 to 125.0.

[0084] In the context of the present invention, B B is the ratio of the mole fraction of B to the sum of the mole fractions of Ni, Mn, Co, and B, wherein the mole fraction of B is measured in the region between a first point defined at the outer edge of the particles of the positive electrode active material according to the present invention and a second point at a certain distance from the first point. The distance by which the first point is separated from the second point is equal to the penetration depth of the XPS, and the penetration depth D' is between 1.0 and 10.0 nm. In particular, the penetration depth is the distance along the axis perpendicular to the virtual line tangent to the outer edge and passing through the first point. As will be understood by the person skilled in the art, a similar XPS analysis is carried out for the mole fractions of Ni, Mn, and Co.

[0085] Within the framework of the present invention, the outer edge of the particle is the boundary or outer limit that separates the particle from its external environment. Thus, the XPS analysis provides the atomic content of the elements in the uppermost layer of the particle, and the penetration depth is about 10.0 nm from the outer boundary of the particle. The outer boundary of the particle is also referred to as the "surface". For example, but the present invention is not limited thereto, the XPS analysis is carried out using a Thermo K-α+ spectrometer (Thermo Scientific).

[0086] Within the framework of the present invention, at% represents atomic percentage. The at% or "atomic percentage" concentration of a given element means what percentage of the atoms of the element are among all the atoms in the compound of interest. Furthermore, within the framework of the present invention, indicating at% is equivalent to mol% or "mole percentage".

[0087] In the context of the present invention, the positive electrode active material may comprise another surface layer, said another surface layer comprising Q, where Q is at least one element selected from the following: Al, Ti, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, V, W, Y, Zn, and Zr; preferably Al, Ti, Cr, Nb, S, Si, Y, Zr, and W; more preferably Al, Ti, Nb, Zr, and W, where the surface layer of B may be disposed on said another surface layer and / or said another surface layer may be disposed on the surface layer of B and / or the positive electrode active material may comprise a mixed surface layer, said mixed surface layer comprising the surface layer of B and said another surface layer.

[0088] Morphology

[0089] In the context of the present invention, the positive electrode active material of the present invention comprises polycrystalline grains, said polycrystalline grains comprising a plurality of primary grains, where the primary grains have an average diameter between 100 nm and 400 nm, as determined by measuring the primary grain size in an image taken by SEM.

[0090] As understood by those skilled in the art, polycrystalline grains are aggregated from 5 or more single-crystalline grains, preferably 10 or more single-crystalline grains, more preferably 50 or more single-crystalline grains. This can be observed by observing grain boundaries in appropriate microscopy techniques such as scanning electron microscopy (SEM). The aggregation of single-crystalline grains into polycrystalline grains occurs in post-treatment steps such as heat treatment steps. In the context of the present invention, if a grain consists of only one crystal grain or at most five crystal grains, preferably at most three crystal grains, as observed by scanning electron microscopy (SEM) or transmission electron microscopy (TEM), preferably by observing the grain boundaries of the grain, then the grain is considered to be single-crystalline. A grain boundary is defined as the interface between two crystal grains in a grain, preferably where the atomic planes of the two crystal grains are aligned with different orientations and meet with a crystallographic discontinuity.

[0091] Preferred embodiments relate to the positive electrode active material of the present invention, which comprises polycrystalline grains having a secondary grain median D50 value of less than 10 μm, preferably less than 8 μm, more preferably less than 5 μm. Preferred embodiments relate to the positive electrode active material of the present invention, which comprises polycrystalline grains having a secondary grain median D50 value of greater than 1 μm, preferably greater than 2 μm, more preferably greater than 3 μm. Preferred embodiments relate to the positive electrode active material of the present invention, which comprises polycrystalline grains having a secondary grain median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm. As understood by those skilled in the art, the particle size distribution (PSD) D50 of the positive electrode active material powder is measured by laser diffraction particle size analysis. For example, but not limited to this invention, Malvern Mastersizer 3000 can be used to measure the particle median D50. In a highly preferred embodiment, the particle size distribution (PSD) of the polycrystalline grains contained in the positive electrode active material of the present invention is measured by a secondary particle size analysis method, preferably where the particle size distribution (PSD) of the positive electrode active material is measured by laser diffraction particle size analysis using a Malvern Mastersizer 3000 with a Hydro MV wet dispersion attachment after dispersing each powder sample in an aqueous medium. More preferably, D50 is defined as the particle size at 50% of the cumulative volume % distribution obtained from a Malvern Mastersizer 3000 with a Hydro MV measuring device.

[0092] In certain preferred embodiments of the present invention and in the context of the present invention, the polycrystalline grains as defined herein are secondary grains. As understood by those skilled in the art, in these certain preferred embodiments, all embodiments regarding polycrystalline grains equally apply to secondary grains as defined in the present invention.

[0093] Preferred embodiments relate to the positive electrode active material of the present invention, which comprises polycrystalline particles, the polycrystalline particles comprising a plurality of primary particles, wherein the primary particles have an average diameter greater than 150 nm, preferably greater than 175 nm, more preferably greater than 200 nm. Preferred embodiments relate to the positive electrode active material of the present invention, which comprises polycrystalline particles, the polycrystalline particles comprising a plurality of primary particles, wherein the primary particles have an average diameter less than 375 nm, preferably less than 350 nm, more preferably less than 300 nm. Preferred embodiments relate to the positive electrode active material of the present invention, which comprises polycrystalline particles, the polycrystalline particles comprising a plurality of primary particles, wherein the primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm. In a highly preferred embodiment, the average diameter of the primary particles is measured by a primary particle size analysis method, preferably by measuring the primary particle size in an image taken by SEM. As understood by those skilled in the art, the average diameter of the primary particles is measured by a primary particle size analysis method, wherein the diameter of the primary particles is calculated by using ImageJ software (ImageJ 1.52a, National Institutes of Health, USA) according to the following steps:

[0094] ● Step 1) Open the file containing the SEM image of the positive electrode active material magnified 10,000 times, wherein the image is taken at the central part of the secondary particles.

[0095] ● Step 2) Set the scale according to the SEM magnification.

[0096] ● Step 3) Use the "polygon selection" tool to draw lines along the edges of at least 50 particles following the primary particle edges. If truncated, exclude the particles at the image edges.

[0097] ● Step 4) Measure the area of the selected drawn primary particles from the "Set measurement parameters and area" box.

[0098] ● Step 5) Calculate the particle diameter of each measured area by assuming the particles are spherical in shape according to and obtain the average primary particle diameter of at least 50 particles.

[0099] As understood by those skilled in the art and in a highly preferred embodiment of the present invention, the secondary particles comprise the B content B as defined herein A 、the B content B as defined herein B and the ratio B as defined herein B / B A .

[0100] In certain preferred embodiments of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, wherein

[0101] ● The polycrystalline particles have a secondary particle median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm, and

[0102] ● The primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm.

[0103] In certain preferred embodiments of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, where

[0104] ● The polycrystalline particles have a secondary particle median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm, and

[0105] ● Ratio B B / B A is in the range of 45.0 to 1000.0, preferably ratio B B / B A is in the range of 50.0 to 200.0, more preferably ratio B B / B A is in the range of 60.0 to 125.0.

[0106] In certain preferred embodiments of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, where

[0107] ● The primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm, and

[0108] ● Ratio B B / B A is in the range of 45.0 to 1000.0, preferably ratio B B / B A is in the range of 50.0 to 200.0, more preferably ratio B B / B A is in the range of 60.0 to 125.0.

[0109] In a preferred embodiment of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, where

[0110] ● The polycrystalline particles have a secondary particle median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm.

[0111] ● The primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm, and

[0112] ● Ratio B B / B A is in the range of 50.0 to 1000.0, preferably ratio B B / B A is in the range of 70.0 to 200.0, more preferably ratio B B / B A is in the range of 90.0 to 125.0.

[0113] In certain preferred embodiments of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, which polycrystalline particles comprise a plurality of primary particles, wherein

[0114] ● The polycrystalline particles have a secondary particle median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm, and

[0115] ● wherein the content x of Ni is between 78.0 mol% ≤ x ≤ 90.0 mol%, preferably 80.0 mol% ≤ x ≤ 88.0 mol%, more preferably 82.0 mol% ≤ x ≤ 86.0 mol%, and

[0116] ● wherein ratio B B / B A is in the range of 40.0 to 1000.0, preferably ratio B B / B A is in the range of 45.0 to 100.0, more preferably ratio B B / B A is in the range of 50.0 to 70.0.

[0117] In certain preferred embodiments of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, which polycrystalline particles comprise a plurality of primary particles, wherein

[0118] ● The primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm,

[0119] ● wherein the content x of Ni is between 78.0 mol% ≤ x ≤ 90.0 mol%, preferably 80.0 mol% ≤ x ≤ 88.0 mol%, more preferably 82.0 mol% ≤ x ≤ 86.0 mol%, and

[0120] ● wherein the ratio B B / B A is in the range of 40.0 to 1000.0, preferably the ratio B B / B A is in the range of 45.0 to 100.0, more preferably the ratio B B / B A is in the range of 50.0 to 70.0.

[0121] In a preferred embodiment of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, wherein

[0122] ● the polycrystalline particles have a secondary particle median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm,

[0123] ● the primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm, and

[0124] ● wherein the content x of Ni is between 78.0 mol% ≤ x ≤ 90.0 mol%, preferably 80.0 mol% ≤ x ≤ 88.0 mol%, more preferably 82.0 mol% ≤ x ≤ 86.0 mol%, and

[0125] ● wherein the ratio B B / B A is in the range of 40.0 to 1000.0, preferably the ratio B B / B A is in the range of 45.0 to 100.0, more preferably the ratio B B / B A is in the range of 50.0 to 70.0.

[0126] In certain preferred embodiments of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, wherein

[0127] ● the polycrystalline particles have a secondary particle median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm, and

[0128] ● wherein the content x of Ni is between 86.0 mol% ≤ x ≤ 98.0 mol%, preferably 88.0 mol% ≤ x ≤ 96.0 mol%, more preferably 90.0 mol% ≤ x ≤ 94.0 mol%, and

[0129] ● wherein the ratio B B / B A is in the range of 60.0 to 1000.0, preferably the ratio B B / B A is in the range of 70.0 to 200.0, more preferably the ratio B B / B A is in the range of 90.0 to 125.0.

[0130] In certain preferred embodiments of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, wherein

[0131] ● The primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm,

[0132] ● wherein the content x of Ni is between 86.0 mol% ≤ x ≤ 98.0 mol%, preferably 88.0 mol% ≤ x ≤ 96.0 mol%, more preferably 90.0 mol% ≤ x ≤ 94.0 mol%, and

[0133] ● wherein the ratio B B / B A is in the range of 60.0 to 1000.0, preferably the ratio B B / B A is in the range of 70.0 to 200.0, more preferably the ratio B B / B A is in the range of 90.0 to 125.0.

[0134] In a preferred embodiment of the present invention, the positive electrode active material of the present invention comprises polycrystalline particles, and the polycrystalline particles comprise a plurality of primary particles, wherein

[0135] ● The polycrystalline particles have a secondary particle median D50 value between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm,

[0136] ● The primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm, and

[0137] ● wherein the content x of Ni is between 86.0 mol% ≤ x ≤ 98.0 mol%, preferably 88.0 mol% ≤ x ≤ 96.0 mol%, more preferably 90.0 mol% ≤ x ≤ 94.0 mol%, and

[0138] ● wherein the ratio B B / B A is in the range of 60.0 to 1000.0, preferably the ratio B B / B A is in the range of 70.0 to 200.0, more preferably the ratio B B / B A is in the range of 90.0 to 125.0.

[0139] On the other hand, the present invention provides a secondary particle-based positive electrode active material for a solid-state battery pack, which contains Li, M', and oxygen, wherein M' contains:

[0140] - Ni with a content x, wherein 75.0 ≤ x < 100.0 mol% relative to M',

[0141] - Co with a content y, wherein 0.0 ≤ y ≤ 15.0 mol% relative to M',

[0142] - Mn with a content z, wherein 0.0 ≤ z ≤ 15.0 mol% relative to M',

[0143] - B with a content b, wherein 0.01 ≤ b ≤ 1.5 mol% relative to M',

[0144] - Q with a content q, wherein Q is an element other than Li, O, Ni, Co, Mn, and B, wherein 0.0 ≤ q ≤ 2.0 mol% relative to M', and,

[0145] - wherein x, y, z, b, and q are measured by ICP-OES,

[0146] - wherein x + y + z + b + q is 100.0 mol%,

[0147] wherein the positive electrode active material has a B content B defined as b / (x + y + z + b) A ,

[0148] wherein the positive electrode active material has a B content B B wherein B B is determined by XPS analysis, wherein B Bexpressed as the ratio of the molar fraction B, as measured by XPS analysis, to the sum of the molar fractions of Ni, Mn, Co, and B, where the ratio B B / B A > 40.0,

[0149] wherein the secondary particles comprise a plurality of primary particles, and

[0150] wherein the primary particles have an average diameter between 100 nm and 400 nm, as determined by measuring the primary particle size in an image taken by SEM.

[0151] In a highly preferred embodiment of the positive electrode active material based on secondary particles, all embodiments related to the positive electrode active material according to the first aspect of the present invention are applicable, mutatis mutandis, to the positive electrode active material based on secondary particles. For example, each embodiment regarding the characteristics and amounts of Li, M', B B 、B A 、primary and secondary particle sizes is equally applicable to the positive electrode active material based on secondary particles.

[0152] Method

[0153] In a second aspect, the present invention provides a method for manufacturing a positive electrode active material for a solid-state battery pack, the method comprising the following successive steps:

[0154] - Preparing a lithium transition metal-based oxide compound,

[0155] - Mixing the lithium transition metal-based oxide compound with a B source to obtain a mixture, and

[0156] - Heating the mixture at a temperature between 250 °C and less than 500 °C for a time between 1 hour and 20 hours to obtain the positive electrode active material powder.

[0157] In a highly preferred embodiment of the method for manufacturing the positive electrode active material of the present invention, the positive electrode active material is according to the first aspect of the present invention. As understood by those skilled in the art, in the case where the method for manufacturing the positive electrode active material of the present invention provides a positive electrode material according to the first aspect of the present invention, all embodiments related to the positive electrode active material according to the first aspect of the present invention are applicable, mutatis mutandis, to the method for manufacturing the positive electrode active material according to the first aspect of the present invention. For example, each embodiment regarding the characteristics and amounts of Li, M', B B 、B A 、primary and secondary particle sizes is equally applicable to the method for preparing the positive electrode active material.

[0158] In a preferred embodiment of the method, the lithium transition metal-based oxide compound comprises Li, M'', and oxygen, where M'' comprises Ni, Mn, Co, and Q, and Q is at least one element selected from the following: Al, Ti, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, V, W, Y, Zn, and Zr; preferably Al, Ti, Cr, Nb, S, Si, Y, Zr, and W; more preferably Al, Ti, Nb, Zr, and W. Preferably, the lithium transition metal-based oxide used is generally prepared by a lithiation method, which is a method of heating a mixture of a transition metal oxide precursor and a lithium source at a temperature of preferably at least 500 °C and at most 1000 °C. Generally, the transition metal precursor is prepared by co-precipitating one or more transition metal sources such as salts, preferably sulfates or nitrates, more preferably sulfates, of elements Ni, Mn, and / or Co in the presence of an alkali metal compound such as an alkali metal hydroxide, for example sodium hydroxide and / or ammonia. Preferably, the lithium source is metallic lithium or a lithium salt, preferably a lithium salt such as LiOH.

[0159] In a preferred embodiment, mixing the lithium transition metal-based oxide compound with the B source is dry mixing the lithium transition metal-based oxide compound with the B source. As understood by those skilled in the art, dry mixing means not adding any additional solvent or liquid to the mixture of the lithium transition metal-based oxide compound and the B source.

[0160] In a preferred embodiment, the B source is boric acid (H3BO3), boron oxide (B2O3), or a borate such as sodium tetrahydroxyborate (NaB(OH)4), trisodium orthoborate (Na3BO3), sodium perborate (Na2H4B2O8), sodium metaborate (Na3B3O6), etc. Preferably, the B source is boric acid (H3BO3).

[0161] In a preferred embodiment, the amount of the B source added is B present in the B source of at least 0.1 mol% relative to M'', preferably B present in the B source of at least 0.25 mol%, more preferably at least 0.5 mol% relative to M''. In a preferred embodiment, the amount of the B source added is B present in the B source of at most 1.4 mol% relative to M'', preferably B present in the B source of at most 1.3 mol%, more preferably at most 1.2 mol% relative to M''. In a preferred embodiment, the amount of the B source added is B present in the B source between 0.1 mol% and 1.4 mol% relative to M', preferably B present in the B source between 0.25 mol% and 1.3 mol%, more preferably between 0.5 mol% and 1.2 mol% relative to M''.

[0162] In a preferred embodiment of the method, the heating temperature of the mixture is higher than 275 °C, preferably higher than 300 °C, and most preferably higher than 325 °C. In a preferred embodiment of the method, the heating temperature of the mixture is lower than 450 °C, preferably lower than 400 °C, and more preferably lower than 375 °C. In a preferred embodiment of the method, the heating temperature of the mixture is between 275 °C and 450 °C, preferably between 300 and 400 °C, and more preferably between 325 and 375 °C.

[0163] In a preferred embodiment, the heating time of the mixture is more than 2 hours, preferably more than 3 hours, and more preferably more than 4 hours. In a preferred embodiment, the heating time of the mixture is less than 15 hours, preferably less than 12 hours, and preferably less than 10 hours. In a preferred embodiment, the heating time of the mixture is between 2 hours and 15 hours, preferably between 3 hours and 12 hours, and more preferably between 4 hours and 10 hours.

[0164] In a certain preferred embodiment, the heating of the mixture

[0165] - The temperature is between 275 °C and 450 °C, preferably between 300 and 400 °C, and more preferably between 325 and 375 °C; and

[0166] - The time is between 2 hours and 15 hours, preferably between 3 hours and 12 hours, and more preferably between 4 hours and 10 hours.

[0167] A preferred embodiment of the method is to heat the mixture in an oxidizing atmosphere. Preferably, the oxidizing atmosphere contains oxygen, such as air, or consists of oxygen.

[0168] In a more preferred embodiment, the heating is carried out in a furnace.

[0169] The method defines the product

[0170] In a third aspect, the present invention relates to a positive electrode active material obtainable by the method according to the second aspect of the present invention.

[0171] As will be understood by those skilled in the art, all embodiments relating to the positive electrode active material according to the first aspect of the present invention and / or the method according to the second aspect of the present invention are, with appropriate modifications, applicable to the positive electrode active material obtainable by the method according to the present invention. For example, each of the various explanations regarding Li, M’, B B 、B A, embodiments of the characteristics and amounts of the primary and secondary particle sizes are equally applicable to the positive electrode active materials obtainable by the methods for manufacturing positive electrode active materials.

[0172] Battery pack

[0173] In a fourth aspect, the present invention relates to a battery pack comprising the positive electrode active material according to the first aspect of the present invention and / or the positive electrode active material obtainable by the method according to the third aspect of the present invention.

[0174] In a preferred embodiment, the battery pack is a solid-state battery pack. Preferably, the solid-state battery pack comprises a sulfide-based electrolyte. Preferably, the electrolyte is a sulfide-based solid electrolyte, and more preferably, the electrolyte contains Li, P, and S. Generally, the following sulfur-containing compounds Li6PS5X can be suitably used, where X is F, Br, Cl, or I, preferably Br or Cl; thio-LISICON (Li 3.25 Ge 0.25 P 0.75 S4), Li2S-P2S5-LiCl, Li2S-SiS2, LiI-Li2S-SiS2, Li2S-P2S5-LiCl, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, Li3PS4, Li7P3S 11 , LiI-Li2S-B2S3, Li3PO4-Li2S-SiS2, Li3PO4-Li2S-SiS2, Li3PO4-Li2S-SiS2, Li 10 GeP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 and / or Li7P3S 11 . In a highly preferred embodiment, the battery pack is a sulfide solid-state battery pack.

[0175] Preferably, the solid-state battery pack further comprises an anode, and the anode contains an anode active material. Suitable electrochemically active anode materials are those known in the art. For example, the anode may contain graphite carbon, metallic lithium, or a lithium-containing metal alloy (such as a Li-In alloy) as the anode active material.

[0176] In a preferred embodiment, the battery pack according to the present invention has a first discharge capacity of at least 190 mAh / g, more preferably at least 200 mAh / g, and most preferably at least 210 mAh / g. As understood by those skilled in the art, the first discharge capacity (DQ1) is measured in a constant current mode (CC) at a C-rate of 0.1 C within a voltage range of 4.3 V to 2.5 V (Li / Li + ), or 3.7 V to 1.9 V (InLi / Li + ).

[0177] In a preferred embodiment, the battery pack according to the present invention has an efficiency of at least 88%, preferably at least 90%, and most preferably at least 92%. As understood by those skilled in the art, in the determination of the battery pack efficiency, the initial charge capacity (CQ1) and the discharge capacity (DQ1) are measured in a constant current mode (CC) at a C-rate of 0.1 C within a voltage range of 4.3 V to 2.5 V (Li / Li + ), or 3.7 V to 1.9 V (In-Li / Li + ). The efficiency (%) of the reversible capacity is obtained according to the following formula:

[0178] .

[0179] Preferably, the 1C current is defined as 160 mA / g in the solution.

[0180] In a preferred embodiment, the battery pack according to the present invention has a polarization (CV1 - DV1) of less than 100 mV, preferably less than 80 mV, and more preferably less than 60 mV. As understood by those skilled in the art, in the determination of the battery pack polarization, the difference between the average voltage of the initial charge (CV1) and the average voltage of the initial discharge (DV1) is used to determine the amount of polarization of the positive electrode:

[0181] .

[0182] Preferably, to calculate CV1, the power capacity in watt-hours (Wh) is divided by CQ1, and the discharge power capacity (W C1 ) in the first cycle is calculated from the area under the plotted voltage (V)-capacity (mAh / g) relationship graph. Preferably, DV1 is calculated by dividing the discharge power capacity (W D1 ) in the first cycle by DQ1.

[0183] Use

[0184] In a fifth aspect, the present invention relates to the use of the positive electrode active material according to the first aspect of the present invention and / or the positive electrode active material obtainable by the method according to the third aspect of the present invention in a battery pack.

[0185] A preferred embodiment is the use of the positive electrode active material in a battery pack, preferably a solid-state battery pack, more preferably a sulfide solid-state battery pack, to improve the efficiency of the battery pack and / or increase the first discharge capacity of the battery pack and / or reduce the polarization of the battery pack.

[0186] In a sixth aspect, the present invention relates to the use of a battery pack according to the present invention in any one of a portable computer, a tablet computer, 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.

[0187] Examples

[0188] Experimental analysis used in the examples

[0189] The following analysis methods were used in the examples.

[0190] A) Inductively coupled plasma optical emission spectrometry (ICP-OES) measurement

[0191] The amounts of Li, Ni, Co, Mn, and B in the positive electrode active material powder were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES) using an Agillent ICP 720-ES (Agilent Technologies). 2 g of the powder sample was dissolved in 10 mL of high-purity hydrochloric acid (HCl at least 37 wt% relative to the total weight of the solution) in a conical flask. The flask was covered with glass and heated on a hot plate at 380 °C until the precursor was completely dissolved. After cooling to room temperature, the solution in the conical flask was poured into a 250 mL volumetric flask. Thereafter, the volumetric flask was filled with deionized water to the 250 mL graduation line and then completely homogenized.

[0192] B) X-ray photoelectron spectroscopy (XPS) measurement

[0193] The surface of the positive electrode active material was analyzed by using X-ray photoelectron spectroscopy (XPS). In XPS measurement, signals were obtained from the uppermost part of the sample, i.e., the first few nanometers (e.g., 1 nm to 10 nm) of the surface layer. Therefore, all elements measured by XPS are contained in the surface layer.

[0194] For the surface analysis of the positive electrode active material powder particles, XPS measurements were carried out using a Thermo K-α+ spectrometer. Monochromatic Al Kα radiation (hν = 1486.6 eV) was used, with a spot size of 400 μm and a measurement angle of 45°. A wide scan was performed at a pass energy of 200 eV to identify the elements present on the surface. The C1s peak with the maximum intensity (or centered) at a binding energy of 284.8 eV was used as the calibration peak position after data collection. Subsequently, at least 10 precise narrow scans of 50 eV were performed for each identified element to determine the precise surface composition.

[0195] Curve fitting was carried out using CasaXPS version 2.3.19PR1.0 (Casa Software), with Shirley-type background processing and Scofield sensitivity factors. The fitting parameters were based on Table 2a. The line shape GL(30) is a Gaussian / Lorentzian product formula with 70% Gaussian line and 30% Lorentzian line. LA(α, β, m) is an asymmetric line shape, where α and β define the tail extension of the peak, and m defines the width.

[0196] Table 1a. XPS fitting parameters for Ni2p, Mn2p, Co2p, and B1s.

[0197]

[0198] For the Mn and Co peaks, constraints were set for each defined peak according to Table 1b.

[0199] Table 1b. XPS fitting constraints for Mn2p and Co2p.

[0200]

[0201] The B surface content as determined by XPS is expressed as the mole fraction of B in the surface layer of the particles divided by the total content of Ni, Co, Mn, and B in the surface layer. It is calculated as follows:

[0202] Fraction of B = B B =

[0203] After fitting, the information on the XPS peak positions can be easily obtained in the area and component report specifications. Figure 1 The XPS spectrum of B for EX1 is shown.

[0204] C) Scanning electron microscopy (SEM) measurements

[0205] The morphology and primary particle size of the positive electrode active material were analyzed by scanning electron microscopy (SEM) technique. Using a JEOL JSM 7100F at 25 °C at 9.6x10-5 Measurements are carried out in a high-vacuum environment of Pa.

[0206] D) Particle size

[0207] D-1) Secondary particle size analysis

[0208] After dispersing each powder sample in an aqueous medium, the particle size distribution (PSD) of the positive electrode active material is measured by laser diffraction particle size analysis using a Malvern Mastersizer 3000 with a Hydro MV wet dispersion attachment. To improve the dispersion of the powder, sufficient ultrasonic irradiation and stirring are applied, and an appropriate surfactant is introduced. D50 is defined as the particle size at 50% of the cumulative volume % distribution obtained from the Malvern Mastersizer 3000 with a Hydro MV measuring device.

[0209] D-2) Primary particle size analysis

[0210] The diameter of the primary particles is calculated using ImageJ software (ImageJ 1.52a, National Institutes of Health, USA) according to the following steps:

[0211] Step 1) Open the file containing the SEM image of the positive electrode active material magnified 10,000 times, where the image is taken at the central part of the secondary particles. Figure 2a An example of such an image is shown, where the dashed line indicates the area to be captured corresponding to Figure 2b the area to be captured.

[0212] Step 2) Set the scale bar according to the SEM magnification.

[0213] Step 3) Use the "Polygon selection" tool to draw lines along the edges of the primary particles for at least 50 particles. If truncated, exclude the particles at the image edges.

[0214] Step 4) Measure the area of the selected drawn primary particles from the "Set measurement parameters and area" box.

[0215] Step 5) Calculate the particle diameter for each measured area by assuming the particles are spherical in shape according to and obtain the average primary particle diameter of at least 50 particles.

[0216] E) Carbon analysis

[0217] The carbon content of the positive electrode active material powder was measured by a Horiba Emia-Expert carbon / sulfur analyzer. 1 g of the positive electrode active material powder was placed in a ceramic crucible in a high-frequency induction furnace. 1.5 g of tungsten and 0.2 g of tin were added to the crucible as accelerators. The powder was heated at a programmable temperature, and the gas generated during combustion was then analyzed by an infrared detector. The carbon concentration was determined by analyzing CO2 and CO.

[0218] F) Sulfide solid-state rechargeable battery pack testing

[0219] F-1) Preparation of sulfide solid-state rechargeable battery pack

[0220] Positive electrode preparation:

[0221] To prepare the positive electrode, a slurry of the positive electrode active material powder, Li-P-S-based solid electrolyte, carbon (Super-P, Timcal), and binder (RC-10, Arkema) in butyl acetate solvent, formulated at 64.0:30.0:3.0:3.0 by weight, was mixed in a glove box filled with Ar. The slurry was cast on one side of an aluminum foil, and then the foil coated with the slurry was dried in a vacuum oven to obtain the positive electrode. The obtained positive electrode was punched with a diameter of 10 nm, with an active material loading of 4 mg / cm 2 or so.

[0222] Negative electrode preparation:

[0223] To prepare the negative electrode, a Li foil (3 mm in diameter, 100 μm thick) was centered on an In foil (10 nm in diameter, 100 μm thick) and pressed to form a Li-In alloy negative electrode.

[0224] Separator preparation:

[0225] To prepare the separator that also functions as a solid electrolyte in the battery pack, the Li-P-S-based solid electrolyte was granulated at a pressure of 250 MPa to obtain a pellet thickness of 100 μm.

[0226] Battery assembly:

[0227] The sulfide solid-state rechargeable battery pack was assembled in a glove box filled with Ar, and the assembly order from bottom to top was: positive electrode (including Al current collector, coated part facing up) - separator - negative electrode (Li side facing up) - copper current collector. The stacked components were pressed together with a pressure of 250 MPa and placed in an external cage to prevent air exposure.

[0228] F-2) Test method

[0229] The test method is the conventional "constant cut-off voltage" test. The conventional battery tests in the present invention follow the scheme shown in Table 2. Each battery is cycled at 60 °C using a Toscat-3100 computer-controlled constant current cycling station (from Toyo).

[0230] The scheme is defined using a 1C current of 160 mA / g. The initial charge capacity (CQ1) and discharge capacity (DQ1) are measured at a C-rate of 0.1 C in constant current mode (CC) within the voltage range of 4.3 V to 2.5 V (Li / Li + ) or 3.7 V to 1.9 V (In-Li / Li + ). The efficiency (%) of the reversible capacity is obtained according to the following formula:

[0231] .

[0232] The polarization amount of the positive electrode is determined using the difference between the average voltage of the initial charge (CV1) and the average voltage of the initial discharge (DV1). To calculate CV1, the power capacity in watt-hours (Wh) is divided by CQ1. The discharge power capacity (W C1 ) in the first cycle is calculated from the area under the plotted voltage (V)-capacity (mAh / g) relationship. DV1 is calculated by dividing the discharge power capacity (W D1 ) in the first cycle by DQ1:

[0233] .

[0234] Table 2. Cycling scheme for the test method of the sulfide solid-state rechargeable battery pack

[0235]

[0236] The present invention is further illustrated in the following examples.

[0237] Comparative Example 1

[0238] The positive electrode active material CEX1 is obtained through the following steps:

[0239] 1) Preparation of the mixture: 100.00 grams of Ni 0.85 Mn 0.07 Co 0.08 (OH)2 and 25.38 grams of anhydrous LiOH are uniformly mixed to obtain the mixture.

[0240] 2) Heating: The mixture obtained from step 1) is heated in an O2 atmosphere at 765 °C for 10 hours and cooled to room temperature to obtain the positive electrode active material CEX1.

[0241] Example 1

[0242] The positive electrode active material EX1 is obtained through the following steps:

[0243] 1) Prepare the first mixture: Mix 100.00 g of Ni 0.85 Mn 0.07 Co 0.08 (OH)2 and 25.38 g of anhydrous LiOH uniformly to obtain the first mixture.

[0244] 2) First heating: Heat the first mixture obtained from step 1) in an O2 atmosphere at 765 °C for 10 hours and cool to room temperature.

[0245] 3) Prepare the second mixture: Mix 100.00 g of the first heated material obtained from step 2) and 0.37 g of H3BO3 uniformly to obtain the second mixture.

[0246] 4) Second heating: Heat the second mixture obtained from step 3) in an O2 atmosphere at 350 °C for 6 hours. Cool the second heated material to room temperature, crush and sieve it to obtain the positive electrode active material EX1.

[0247] Comparative Example 2

[0248] The positive electrode active material CEX2 is prepared in the same manner as CEX1, except that the mixture is heated at 785 °C in step 2).

[0249] Example 2

[0250] The positive electrode active material EX2 is prepared in the same manner as EX1, except that the first mixture is heated at 785 °C in step 2).

[0251] Comparative Example 3

[0252] The positive electrode active material CEX3 is obtained through the following steps:

[0253] 1) Prepare the mixture: Mix 100.00 g of Ni 0.92 Mn 0.03 Co 0.05 (OH)2 and 25.34 g of anhydrous LiOH uniformly to obtain the mixture.

[0254] 2) Heating: Heat the mixture prepared in step 1) in an O2 atmosphere at 720 °C for 10 hours and cool to room temperature to obtain the positive electrode active material CEX3.

[0255] Example 3

[0256] The positive electrode active material EX3 is obtained through the following steps:

[0257] 1) Prepare the first mixture: Mix 100.00 g of Ni 0.92 Mn 0.03 Co 0.05 (OH)2 and 25.34 g of anhydrous LiOH uniformly to obtain the first mixture.

[0258] 2) First heating: Heat the first mixture obtained from step 1) in an O2 atmosphere at 720 °C for 10 hours and cool to room temperature.

[0259] 3) Prepare the second mixture: Mix 100.00 g of the first heated material obtained from step 2) and 0.37 g of H3BO3 uniformly to obtain the second mixture.

[0260] 4) Second heating: Heat the second mixture obtained from step 3) in an O2 atmosphere at 350 °C for 6 hours. Cool the second heated material to room temperature, crush and sieve it to obtain the positive electrode active material EX3.

[0261] Comparative Example 4

[0262] The positive electrode active material CEX4 is prepared in the same manner as CEX3, except that the mixture is heated at 750 °C in step 2).

[0263] Example 4

[0264] The positive electrode active material EX4 is prepared in the same manner as EX3, except that the first mixture is heated at 750 °C in step 2).

[0265] Comparative Example 5.1

[0266] The positive electrode active material CEX5.1 is obtained through the following steps:

[0267] 1) Prepare the mixture: Mix 100.0 g of Ni 0.625 Mn 0.175 Co 0.200 (OH)2 and 26.8 g of LiOH uniformly to obtain the mixture.

[0268] 2) Heating: Heat the mixture obtained from step 1) in a stream of dry air at 860 °C for 10 hours and cool to room temperature to obtain the positive electrode active material CEX5.1.

[0269] Comparative Example 5.2

[0270] The positive electrode active material CEX5.2 is obtained through the following steps:

[0271] 1) Prepare the first mixture: Mix 100.0 g of Ni 0.625 Mn 0.175 Co 0.200 (OH)2 and 26.8 g of LiOH uniformly to obtain the first mixture.

[0272] 2) First heating: Heat the first mixture obtained from step 1) at 860 °C for 10 hours while flowing dry air and then cool it to room temperature.

[0273] 3) Prepare the second mixture: Mix 50.0 g of the first heated material obtained from step 2) and 0.27 g of H3BO3 uniformly to obtain the second mixture.

[0274] 4) Second heating: Heat the second mixture obtained from step 3) at 350 °C for 7 hours in an O2 atmosphere. Cool the second heated material to room temperature, crush it and sieve it to obtain the positive electrode active material CEX5.2.

[0275] Comparative Example 6

[0276] The positive electrode active material CEX6 is prepared in the same manner as CEX1, except that the mixture is heated at 805 °C in step 2).

[0277] Example 5

[0278] The positive electrode active material EX5 is prepared in the same manner as EX1, except that the first mixture is heated at 805 °C in step 2).

[0279] Comparative Example 7.1

[0280] The positive electrode active material CEX7.1 is prepared in the same manner as CEX1, except that the mixture is heated at 815 °C in step 2).

[0281] Comparative Example 7.2

[0282] The positive electrode active material CEX7.2 is prepared in the same manner as EX1, except that the first mixture is heated at 815 °C in step 2).

[0283] Comparative Example 8.1

[0284] The positive electrode active material CEX8.1 is prepared in the same manner as CEX1, except that the mixture is heated at 825 °C in step 2).

[0285] Comparative Example 8.2

[0286] The positive electrode active material CEX8.2 was prepared in the same manner as EX1, except that in step 2), the first mixture was heated at 825 °C.

[0287] Table 3. Chemical composition, B B / B A Ratio and average primary particle diameter summary

[0288]

[0289] Composition relative to the total molar content of Ni, Co, Mn, and B

[0290] B B is the mole fraction of B relative to the total molar content of Ni, Co, Mn, and B according to XPS analysis

[0291] B A is the mole fraction of B relative to the total molar content of Ni, Co, Mn, and B according to ICP-OES analysis

[0292] n / a: Not applicable

[0293] Table 4. Electrochemical property summary

[0294]

[0295] Table 3 summarizes the chemical composition, B B / B A ratio, average primary particle diameter, and secondary particle size distribution (PSD) of all examples and comparative examples. Table 4 summarizes the electrochemical properties such as DQ1, efficiency, and polarization (CV1 - DV1) of the examples and comparative examples.

[0296] The average primary particle diameters of CEX1 and EX1 are smaller than those of CEX2 and EX2, where the average primary particle diameters of CEX1 and EX1 are 215 nm, while those of CEX2 and EX2 are 264 nm. The average primary particle diameter of CEX3 and EX3 is 202 nm, which is smaller than the average primary particle diameter of CEX4 and EX4, which is analyzed to be 274 nm. As a representative, in Figure 2a the SEM image of CEX3 is shown.Figure 2b The image contains lines and numbers for identifying primary particles to obtain the average primary particle diameter.

[0297] In Table 3, for EX1, EX2, EX3, EX4, EX5, CEX5.2, CEX7.2, and CEX8.2, the XPS analysis results of B (B B ) were compared with the ICP - OES results of B (B A ). B B results higher than 0 indicate that the B exists on the surface of the positive electrode active material because it is related to XPS measurement, and the signal of XPS measurement is obtained from the first few nanometers (e.g., 1 nm to 10 nm) of the uppermost part of the sample. On the other hand, the B A from ICP - OES measurement is the B content of the whole particle. Therefore, the ratio of the XPS result to the ICP - OES result such as B B / B A indicates that the B mainly exists on the surface of the positive electrode active material. The higher the B B / B A value corresponds to more B existing on the surface of the positive electrode active material. Figure 1 is representative of the XPS spectrum showing the B1s peak of EX1.

[0298] Relative to the total molar content of Ni, Co, Mn, and B, the positive electrode active materials EX1, EX2, EX3, EX4, EX5, and CEX5.2 contain 0.9 mol% of B. The B B / B AThe values are 65.6, 56.7, 101.1, 88.9, 61.8, and 72.2 respectively, which confirms the presence of B on the surface of the particles according to the present invention. The solid-state rechargeable battery pack containing EX1 has a DQ1 value of 207.7 mAh / g, which is higher than the DQ1 value of 178.1 mAh / g for the battery pack containing CEX1. In addition, the efficiency and CV1 - DV1 of the battery pack containing EX1 are 90.3% and 48.6 mV, while the efficiency and CV1 - DV1 of the battery pack containing CEX1 are 87.8% and 83.4 mV, indicating that the battery pack containing EX1 has improved electrochemical stability. The DQ1 value of the battery pack containing EX2 is 204.2 mAh / g, while the DQ1 value of the battery pack containing CEX2 is 173.9 mAh / g, the DQ1 value of the battery pack containing EX3 is 223.8 mAh / g, while the DQ1 value of the battery pack containing CEX3 is 188.1 mAh / g, and the DQ1 value of the battery pack containing EX4 is 208.3 mAh / g, while the DQ1 value of the battery pack containing CEX4 is 207.7 mAh / g. The efficiency of the battery pack containing EX2 or EX3 is superior to that of the battery pack containing CEX2 or CEX3. The efficiency of the battery pack containing EX2 is 88.8%, while the efficiency of the battery pack containing CEX2 is 80.1%, and the efficiency of the battery pack containing EX3 is 93.0%, while the efficiency of the battery pack containing CEX3 is 83.1%. The CV1 - DV1 of the battery pack containing EX2 is 56.2 mV, while the CV1 - DV1 of the battery pack containing CEX2 is 91.9 mV, the CV1 - DV1 of the battery pack containing EX3 is 79.1 mV, while the CV1 - DV1 of the battery pack containing CEX3 is 106.5 mV, and the CV1 - DV1 of the battery pack containing EX4 is 78.9 mV, while the CV1 - DV1 of the battery pack containing CEX4 is 133.8 mV. The battery pack containing EX5 has improved electrochemical properties such as DQ1, efficiency, and CV1 - DV1 compared to the battery pack containing CEX6. The DQ1, efficiency, and CV1 - DV1 of the battery pack containing EX5 are 186.8 mAh / g, 83.8%, and 39.5 mV respectively, while the DQ1, efficiency, and CV1 - DV1 of the battery pack containing CEX6 are 179.7 mAh / g, 81.6%, and 58.6 mV respectively.

[0299] The positive electrode active material CEX5.2 has B of 72.2 B / B AThe value indicates that B is present on the surface of the particles, while CEX5.1 does not contain B on the surface of the particles. Although the solid-state rechargeable battery pack containing CEX5.2 has improved DQ1 and reversible capacity efficiency compared to the battery pack containing CEX5.1, when the positive electrode active material contains B on the surface, CV1 - DV1 increases from 19.2 mV to 30.3 mV.

[0300] The positive electrode active material CEX7.2 has a B value of 31.0 B / B A value, and the average primary particle diameter of CEX7.2 is 454 nm. The positive electrode active material CEX8.2 has a B value of 30.4 B / B A value and the average primary particle diameter of CEX8.2 is 533 nm, which indicates that both CEX7.2 and CEX8.2 contain B on the surface of the particles. Compared with the DQ1 and efficiency of CEX7.1, the DQ1 and efficiency of CEX7.2 are improved, where CEX7.1 does not contain B on the surface of the particles. Compared with the DQ1 and efficiency of CEX8.1, the DQ1 and efficiency of CEX8.2 are improved, where CEX8.1 does not contain B on the surface of the particles. Although the DQ1 and efficiency are improved, for both CEX7.2 and CEX8.2, the CV1 - DV1 value is worse, where the BB / BA of CEX7.2 and the B B / B A of CEX8.2 are both lower than 40.0.

[0301] It is significantly observed that the combination of an average primary particle diameter in the range of 170 nm to 350 nm or 400 nm and a B B / B A value higher than 40.0 can achieve the object of the present invention, that is, to provide a positive electrode active material having improved first discharge capacity, improved rate efficiency, and / or improved polarization.

Claims

1. A positive electrode active material for a solid-state battery pack, the positive electrode active material comprising Li, M', and oxygen, wherein M' comprises: - Ni with a content of x, where 75.0 ≤ x < 100.0 mol% relative to M', - Co with a content of y, where 0.0 ≤ y ≤ 15.0 mol% relative to M', - Mn with a content of z, where 0.0 ≤ z ≤ 15.0 mol% relative to M', - B with a content of b, where 0.01 ≤ b ≤ 1.5 mol% relative to M', - Q with a content of q, where Q is an element other than Li, O, Ni, Co, Mn, and B, where 0.0 ≤ q ≤ 2.0 mol% relative to M', and, - where x, y, z, b, and q are measured by ICP-OES, - where x + y + z + b + q is 100.0 mol%, wherein the positive electrode active material has a B content B defined as b / (x + y + z + b) A , wherein the positive electrode active material has a B content of B B , where B B is determined by XPS analysis, where B B is expressed as the ratio of the mole fraction of B measured by XPS analysis to the total mole fraction of Ni, Mn, Co, and B where ratio B B / B A > 40.0, where the positive electrode active material comprises secondary particles containing a plurality of primary particles, and where the primary particles have an average diameter between 100 nm and 400 nm, which is determined by measuring the primary particle size in an image taken by SEM.

2. The positive electrode active material according to claim 1, wherein the ratio B B / B A > 45.0, preferably B B / B A > 50.0, and most preferably B B / B A > 60.

0.

3. The positive electrode active material according to claim 1 or 2, wherein the ratio B B / B A < 1000.0, preferably < 200.0, more preferably < 125.

0.

4. The positive electrode active material according to any one of the preceding claims, wherein x ≥ 78.0 mol%, preferably x ≥ 80.0 mol%, more preferably x ≥ 82.

0.

5. The positive electrode active material according to any one of the preceding claims, wherein x ≤ 98.0 mol%, preferably x ≤ 96.0 mol%, more preferably x ≤ 94.0 mol%.

6. The positive electrode active material according to any one of the preceding claims, wherein the Co content is 0.0 mol% < y ≤ 13.0 mol%, preferably 2.0 mol% ≤ y ≤ 11.0 mol%, more preferably 3.0 mol% ≤ y ≤ 9.0 mol%.

7. The positive electrode active material according to any one of the preceding claims, wherein the Mn content is 0.0 mol% < z ≤ 10.0 mol%, preferably 1.0 mol% ≤ z ≤ 9.0 mol%, more preferably 2.0 mol% ≤ z ≤ 8.0 mol%.

8. The positive electrode active material according to any one of the preceding claims, wherein 0.1 mol% ≤ b ≤ 1.4 mol%, preferably 0.25 mol% ≤ b ≤ 1.3 mol%, more preferably 0.5 mol% ≤ b ≤ 1.2 mol%.

9. The positive electrode active material according to any one of the preceding claims, wherein the median size D50 of the secondary particles is between 1 and 10 μm, preferably between 2 and 8 μm, more preferably between 3 and 5 μm, which is determined by laser diffraction particle size analysis.

10. The positive electrode active material according to any one of the preceding claims, wherein the primary particles have an average diameter between 150 and 375 nm, preferably between 175 and 350 nm, more preferably between 200 and 300 nm.

11. The positive electrode active material according to any one of the preceding claims, wherein the positive electrode active material has a Li / M' ratio (mol / mol) in the range of 0.90 – 1.10, preferably in the range of 0.92 – 1.08, more preferably in the range of 0.95 – 1.

05.

12. The positive electrode active material according to any one of the preceding claims, wherein Q is at least one element selected from the following: Al, Ti, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, V, W, Y, Zn, and Zr; preferably Al, Ti, Cr, Nb, S, Si, Y, Zr, and W; more preferably Al, Ti, Nb, Zr, and W.

13. A method for manufacturing a positive electrode active material for a solid-state battery pack, wherein the positive electrode active material is the positive electrode active material according to any one of claims 1 to 12, and the method comprises the following consecutive steps: - preparing a lithium transition metal-based oxide compound, - mixing the lithium transition metal-based oxide compound with a B source to obtain a mixture, and - heating the mixture at a temperature between 250 °C and less than 500 °C for a time between 1 hour and 20 hours to obtain a positive electrode active material powder.

14. The method according to claim 13, wherein heating the mixture is carried out in an oxidizing atmosphere.

15. A solid-state battery pack comprising the positive electrode active material according to claims 1 to 12.

16. The solid-state battery pack according to claim 15, wherein the solid-state battery pack comprises a sulfide-based solid electrolyte containing Li, P, and S.

17. Use of the solid-state battery pack according to claim 15 or 16 in any one of a portable computer, a tablet computer, 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.

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