Lithium nickel-based oxide as a cathode active material for lithium batteries

Abstract

The present disclosure relates to a cathode active material for lithium batteries, comprising lithium (Li), M, and oxygen (O), wherein M includes niobium (Nb) and 60 at% or more of nickel (Ni). Moreover, the cathode active material according to this disclosure presents a low carbon (carbonate salts) content. The present disclosure also relates to a method for manufacturing a cathode active material, and a battery comprising the cathode active material, for an electric vehicle or hybrid electric vehicle.

Description

LITHIUM NICKEL-BASED OXIDE AS A CATHODE ACTIVE MATERIAL FOR LITHIUM BATTERIESTECHNICAL FIELD

[0001] The present disclosure relates to a cathode active material for lithium batteries, comprising lithium (Li), M, and oxygen (O), wherein M includes niobium (Nb) and 60 at% or more of nickel (Ni). Moreover, the cathode active material according to this disclosure presents a low carbon (carbonate salts) content. The present disclosure also relates to a method for manufacturing a cathode active material, and a battery comprising the cathode active material, for an electric vehicle or hybrid electric vehicle.BACKGROUND ART

[0002] Modern batteries require high energy density as well as long cycle life, especially for automotive applications. Currently, NMC (lithium-nickel-manganese-cobalt oxide) or NCA (lithium-nickel-cobalt-aluminum oxide) are the most promising cathode active materials used in batteries for an electric vehicle or hybrid electric vehicle.

[0003] NMC materials comprise particles, usually of spherical shape, and according to the formula Lii+a(NibMncCod)i-aO2. Due to the lower price of nickel compared to cobalt, the NMC material with a higher Ni content and a lower Co content results in a cheaper cathode active material. In the context of this disclosure, the term "high Ni NMC" refers to NMC materials wherein the Ni content (b in the previous formula above) is at least 0.6, for example LiNi0.6Mn0.2Co0.2O2. The term "very high Ni NMC" refers to NMC materials wherein b is at least 0.8, for example LiNi0.94Mn0.03Co0.03O2.

[0004] The reversible capacity of the NMC material tends to increase as the Ni content increases. For example, NMC 622 (LiNi0.6Mn0.2Co0.2O2) presents higher reversible capacity compared to NMC 442 (LiNi0.4Mn0.4Co0.2O2), meaning that less weight or volume is required to achieve a certain energy demand.

[0005] However, as the Ni content increases, the amount of impurities present in the cathode active material also tend to increase, see US7648693. Impurities, such as hydroxide or carbonate salts known as soluble bases, often remain in the cathode active material causing gas generation in the cells (bulging), resulting in poor stability, poor cycling performance and raising safety issues.

[0006] Several alternatives have been investigated to improve the stability of the NMC composition, for example by adding metals such as Nb, to the cathode active material.

[0007] CN110392950 discloses a lithium-nickel-manganese composite oxide as cathode active material comprising a lithium-niobium compound on the surface of the powder particles. CN110392950 also discloses a method to obtain the coated cathode active material comprising the steps of wet mixing, filtering and drying, which increases the complexity of the manufacturing method reducing the throughput.

[0008] Moreover, CN106505195A also discloses a lithium battery comprising a cathode active material containing Nb. However, the cathode active material as disclosed in CN106505195A presents high-capacity fading. Capacity fading or capacity loss is a phenomenon observed in rechargeable battery usage where the charging capacity decreases with use. Therefore, although the addition of Nb seems to improve the discharge capacity of Ni-rich cathode active materials, it is not beneficial in terms of capacity retention. Additionally, the method disclosed in CN106505195A to obtain the cathode active material further comprises a washing step and a drying step, increasing the complexity of the manufacturing method and reducing the throughput.

[0009] JP2002151071A discloses a cathode active material powder comprising Li, Ni, Co, and further comprising a Li-Nb-O-based compound present at the surface of the powder particles. According to the data disclosed in JP2002151071A, the Li-Nb-O-based compound seems to improve the thermal stability of the cathode active material.

[0010] The presence of certain compounds at the surface of the cathode active material creates a physical barrier preventing direct contact between the cathode active material and the electrolyte of a battery. Therefore, coating a cathode active material might improve its stability and its battery performance.

[0011] Accordingly, there is a need for a cathode active material with improved electrochemical properties such as discharge capacity and / or capacity retention.

[0012] There is also a need for a method for manufacturing the above-mentioned cathode active material with high throughput, and also for a battery comprising said cathode active material.SUMMARY

[0013] In a first aspect, the present disclosure provides a cathode active material for lithium batteries, comprising Li, M, and O, wherein M comprises:Ni in an atomic content x, wherein 0.60 < x < 0.98 relative to M,Co in an atomic content y, wherein 0.005 < y < 0.30 relative to M,Mn in an atomic content z, wherein 0.005 < z < 0.30 relative to M,Nb in an atomic content a, wherein 0.001 < a < 0.10 relative to M, wherein x, y, z and a are determined by ICP-OES, x+y+z+a is 1, wherein the Li / M atomic ratio is between 0.8 to 1.5, wherein the cathode active material contains IJ2CO3 in a mass content lower than 0.5% relative to the total mass of the cathode active material, and wherein the ratio Nbxps / Nbicp > 1, wherein Nbxps is the Nb atomic content relative to M as determined by XPS analysis, and wherein Nbicp is the Nb atomic content relative to M as determined by ICP analysis.

[0014] It has been found that a cathode active material according to this disclosure has an improved discharged capacity (DQ7) and capacity retention (Qirr %), when compared with the corresponding cathode active material without Nb. Additionally, the cathode active material according to this disclosure comprises a low carbon content (carbonate salts).

[0015] In a second aspect, the present disclosure provides a method for manufacturing said cathode active material, comprising the following steps:- mixing a metal-based precursor with a lithium source to obtain a first mixture;- heating the first mixture at a temperature between 600 °C to 800 °C to obtain a first heated material;- mixing the first heated material with a Nb containing compound to obtain a second mixture; and- heating the second mixture at a temperature between 200 °C and 800 °C to obtain the cathode active material.

[0016] Conventional method for manufacturing cathode active materials requires a washing step to reduce the content of impurities, such as soluble bases (LiOH and IJ2CO3). However, it has been found that the cathode active material obtainable by the method according to this disclosure may comprise a low carbon content, a low LiOH content and / or a low Li2COs content without a washing step, reducing the number of manufacturing steps and improving the throughput.

[0017] In a third aspect, the present disclosure provides a battery comprising a cathode active material according to the first aspect of this disclosure, for electric vehicles (such as, but not limited to battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, extended range electric vehicles, fuel cell electric vehicles) for passenger or heavy-duty applications, two-wheeler transportation, energy storage systems, portable electronic devices, power tools, robotic devices, uninterruptible power supplies systems, telecommunicationdevices, defense applications, medical devices and aviation, aerospace, rail or marine devices and transportation systems, among other applications.

[0018] Moreover, the cathode active material obtainable by this method comprises particles with a low specific surface area (SSA). A battery comprising a cathode active material having particles with low SSA might have an improved stability due to the lower interaction between the particles and the electrolyte of the battery.

[0019] In a fourth aspect, the present disclosure provides the use of a battery according to third aspect of this disclosure, in electric vehicles for passenger or heavy-duty applications, two-wheeler transportation, energy storage systems, portable electronic devices, power tools, robotic devices, uninterruptible power supplies systems, telecommunication devices, defense applications, medical devices and aviation, aerospace, rail or marine devices and transportation systems.DETAILED DESCRIPTION

[0020] In the following detailed description, preferred embodiments are described in detail to enable practice of the present invention. Although the present invention is described with reference to these specific preferred embodiments, it will be understood that the present invention is not limited to these preferred embodiments. In contrast, the present invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description.

[0021] The following terms are intended to have the meaning presented below and are useful in understanding the description and intended scope of this disclosure.

[0022] The term "comprising", as used herein and in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps, or components as referred to, but does not preclude 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. It means that with respect to the present disclosure, 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".

[0023] The term "cathode active material" (also known as CAM or positive electrode active material) refers to a material which is electrochemically active in a positive electrode or cathode. By active material, it must be understood to be capable of capturing and releasing Li ions when subjected to a voltage change over a predetermined period.

[0024] In the framework of the present disclosure, the content of a particular element of the periodic table signifies atomic percentage. The at% or "atomic percent" of a given element expression of a concentration means how many percent of all atoms in the concerned compound are atoms of said element. The designation at% is equivalent to mol% or "molar percent".

[0025] The term "XXPS" refers to the content of element X as measured by XPS analysis, wherein X is an element of the periodic table. For example, "Nbxps" refers to Nb content as measured by XPS analysis.

[0026] The term "XICP" refers to the content of element as measured by ICP-OES, wherein X is an element of the periodic table. For example, "Nbicp" refers to Nb content as measured by ICP-OES.

[0027] The term "Nbxps / Nbicp ratio" indicates the distribution of Nb in the cathode active material powder particles. For example, a Nbxps / Nbicp ratio = 1 indicates that Nb is present at the surface of the cathode active material powder particles. A Nbxps / Nbicp ratio > 1 indicates that Nb is mainly present at the surface of the cathode active material powder particles. A Nbxps / Nbicp ratio > 3 indicates that Nb is mostly present at the surface of the cathode active material powder particles.

[0028] The term "dry mixing" refers to a method step wherein two or more ingredients are mixed in solid state without the presence of a solvent, such as water, methanol, HCI or H2SO4.

[0029] As used herein, a range of values "between X and Y" include the endpoints of X and Y.

[0030] The term "Electric vehicles" includes hybrid electric vehicles include, Plug-in Hybrid Electric Vehicles, for passenger and freight, marine, air, aerospace and ground transportation.Cathode Active Material

[0031] In a first aspect, the present disclosure relates to a cathode active material for lithium batteries, wherein the cathode active material comprises Li, M, and O, wherein M comprises:Ni in an atomic content x, wherein 0.60 < x < 0.98 relative to M;Co in an atomic content y, wherein 0.005 < y < 0.30 relative to M;Mn in an atomic content z, wherein 0.005 < z < 0.30 relative to M;Nb in an atomic content a, wherein 0.001 < a < 0.10 relative to M; wherein x, y, z and a are determined by ICP-OES, wherein x+y+z+a is 1, wherein the Li / M atomic ratio is between 0.8 to 1.5, wherein the cathode active material contains IJ2CO3 in a mass content lower than 0.5% relative to the total mass of the cathode active material, and wherein the ratio Nbxps / Nbicp > 1, wherein Nbxps is the Nb atomic content relative to M as determined by XPS analysis, and wherein Nbicp is the Nb atomic content relative to M as determined by ICP analysis.

[0032] In one embodiment, the cathode active material comprises Ni in an atomic content x, wherein 0.70 < x < 0.98 relative to M. In another embodiment, 0.80 < x < 0.98 relative to M. In another embodiment, 0.90 < x < 0.98 relative to M. For example, x is 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97 or 0.98, relative to M.

[0033] In one embodiment, the cathode active material comprises Co in an atomic content y, wherein 0.01 < y < 0.15 relative to M. In another embodiment, 0.01 < y < 0.10 relative to M. For example, y is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10 relative to M.

[0034] In one embodiment, the cathode active material comprises Mn in an atomic content z, wherein 0.01 < z < 0.15 relative to M. In another embodiment, 0.01 < z < 0.10 relative to M. For example, z is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10, relative to M.

[0035] In one embodiment, the cathode active material comprises Nb in an atomic content a, wherein 0.001 < a < 0.05 relative to M. In another embodiment, 0.001 < a < 0.01 relative to M. For example, a is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009 or 0.01, relative to M.

[0036] In one embodiment of the cathode active material, the Li / M atomic ratio is between 0.9 and 1.2. In another embodiment, the Li / M atomic ratio is between 0,95 and 1.1. For example, the Li / M atomic ratio is 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04 or 1.05.

[0037] In one embodiment, the cathode active material comprises Ni in an atomic content x, wherein 0.70 < x < 0.98 relative to M; Mn in an atomic content y, wherein 0.01 < y < 0.15relative to M; Co in an atomic content z, wherein 0.01 < z < 0.15 relative to M; Nb in an atomic content a, wherein 0.001 < a < 0.01 relative to M, and a Li / M atomic ratio between 0.9 and 1.2.

[0038] In one embodiment, the cathode active material is according to the formula (I) LiwNixiMnyiCoziNbaiO?, wherein 0.80 < w < 1.50; 0.60 < xl < 0.98; 0.005 < yl < 0.30; 0.005 < zl < 0.30; 0.001 < al < 0.10; wherein xl, yl, zl and al are determined by ICP- OES, and xl+yl+zl+a l is 1, wherein the cathode active material contains IJ2CO3 in a mass content lower than 0.5% relative to the total mass of the cathode active material, and wherein the ratio Nbxps / Nbicp > 1.

[0039] In one embodiment, the cathode active material is according to the formula (I), wherein 0.70 < xl < 0.98. In another embodiment, 0.80 < xl < 0.98. In another embodiment, 0.90 < xl < 0.98. For example, xl is 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97 or 0.98.

[0040] In one embodiment, the cathode active material is according to the formula (I), wherein 0.01 < yl < 0.15. In another embodiment, 0.01 < yl < 0.10. For example, yl is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10.

[0041] In one embodiment, the cathode active material is according to the formula (I), wherein 0.01 < zl < 0.15. In another embodiment, 0.01 < zl < 0.10. For example, zl is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10.

[0042] In one embodiment, the cathode active material is according to the formula (I), wherein 0.001 < al < 0.05. In another embodiment, 0.001 < al < 0.01. For example, al is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009 or 0.01.

[0043] In one embodiment, the cathode active material is according to the formula (I), wherein 0.9 < w < 1.2. In another embodiment, 0.95 < w < 1.1. For example, w is 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04 or 1.05.

[0044] In one embodiment, the cathode active material is according to the formula (I), wherein 0.9 < w < 1.2; 0.70 < xl < 0.98; 0.01 < yl < 0.15; 0.01 < zl < 0.15; 0.001 < al < 0.01.

[0045] In one embodiment, the cathode active material comprises IJ2CO3 in a mass content equal to or lower than 0.4% relative to the total mass of the cathode active material, asmeasured by titration analysis method. In another embodiment, the U2CO3 mass content is equal to or lower than 0.3%. In another embodiment, the U2CO3 mass content is equal to or lower than 0.25%.

[0046] In one embodiment, the cathode active material further comprises LiOH in a mass content equal to or lower than 0.7% relative to the total mass of the cathode active material, as measured by titration analysis method. In another embodiment, the LiOH mass content is equal to or lower than 0.6%. In another embodiment, the LiOH mass content is equal to or lower than 0.5%. In another embodiment, the LiOH mass content is equal to or lower than 0.4%. In another embodiment, the LiOH mass content is equal to or lower than 0.35%.

[0047] In one embodiment, the cathode active material comprises carbon in a content equal to or lower than 0.08 % relative to the total mass of the cathode active material, as measured by carbon analysis method. In another embodiment, the carbon content is equal to or lower than 0.06 % relative to the total mass of the cathode active material. In another embodiment, the carbon content is equal to or lower than 0.05 % relative to the total mass of the cathode active material. For example, 0.03 %, 0.035 %, 0.04 %, 0.045 % or 0.05 %, relative to the total mass of the cathode active material.

[0048] In one embodiment, the cathode active material comprises soluble bases in a content equal to or lower than 400 pmol per gram of the cathode active material, as measured by titration analysis method. In another embodiment, the soluble bases content is equal to or lower than 350 pmol per gram of the cathode active material. For example, 240 pmol, 250 pmol, 260 pmol, 270 pmol, 280 pmol, 290 pmol, 300 pmol, 310 pmol, 320 pmol, 330 pmol, 340 pmol or 350 pmol, per gram of the cathode active material.

[0049] In one embodiment, the cathode active material has a specific surface area between 0.1 m2 / g and 0.5 m2 / g. In another embodiment, the specific surface is between 0.2 m2 / g and 0.4 m2 / g. In another embodiment, the specific surface area is between 0.2 m2 / g and 0.35 m2 / g. For example, 0.21 m2 / g, 0.22 m2 / g, 0.23 m2 / g, 0.24 m2 / g, 0.25 m2 / g, 0.26 m2 / g, 0.27 m2 / g, 0.28 m2 / g, 0.29 m2 / g, 0.30 m2 / g, 0.31 m2 / g, 0.32 m2 / g, 0.33 m2 / g, 0.34 m2 / g or 0.35 m2 / g.

[0050] In one embodiment, the cathode active material comprises Nb in a content Nbxps and a content Nbicp, wherein the ratio Nbxps / Nbicp > 1. In another embodiment, the ratio Nbxps / Nbicp > 2. In another embodiment, the ratio Nbxps / Nbicp > 3. In another embodiment, the ratio Nbxps / Nbicp > 10.

[0051] In one embodiment, the cathode active material comprises particles having a crystalline size between 80 nm and 140 nm, as measured by XRD Rietveld refinement. In another embodiment, the crystalline size is between 90 nm and 130 nm. In another embodiment, the crystalline size is between 100 nm and 125 nm. For example, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm or 125 nm.

[0052] In one embodiment, the cathode active material is according to the formula (I), wherein 0.9 < w < 1.2; 0.80 < xl < 0.98; 0.01 < yl < 0.15; 0.01 < zl < 0.15; and 0.001 < al < 0.01, and having a IJ2CO3 mass content lower than 0.35 %, a LiOH mass content lower than 0.6 %, relative to the total mass of the cathode active material, a specific surface area lower than 0.35 m2 / g, a ratio Nbxps / Nbicp > 2 and a crystalline size between 100 nm and 125 nm.

[0053] It has been found that the discharge capacity (DQ7) of a lithium battery comprising a cathode active material according to this disclosure is higher than the corresponding lithium battery comprising a cathode active material without Nb. Additionally, a cathode active material according to this disclosure also shows an improved capacity retention when compared with the corresponding cathode active material without Nb, see Table V of the results section.Method for Manufacturing a Cathode Active Material

[0054] In a second aspect, the present disclosure relates to a method for manufacture the cathode active material according to the first aspect, wherein the method comprises the following steps:- mixing a metal-based precursor with a lithium source to obtain a first mixture;- heating the first mixture at a temperature between 600 °C and 800 °C to obtain a first heated material;- mixing the first heated material with a Nb source to obtain a second mixture; and- heating the second mixture at a temperature between 200 °C and 800 °C to obtain the cathode active material.

[0055] The cathode active material according to the first aspect of the present disclosure may be obtained by a method according to the second aspect of the present disclosure. In detail, the technical features of the first aspect of the present disclosure, e.g., the specific composition of the cathode active material, specific ratio Nbxps / Nbicp, specific surface area,and the low content of U2CO3 and LiOH may be achieved by the method according to the second aspect of the present disclosure.

[0056] In one embodiment of the method, the metal-based precursor comprises Ni, Mn, and Co. In another embodiment, the metal-based precursor is according to the formula (II) Nix2Mny2Coz2(OH)2, wherein 0.60 < x2 < 0.98; 0.005 < y2 < 0.30; 0.005 < z2 < 0.30; wherein x2, y2 and z2 are measured by ICP-OES, and x2+y2+z2 is 1.

[0057] In one embodiment of the method, the metal-based precursor is according to formula (II), wherein 0.70 < x2 < 0.98. In another embodiment, 0.80 < x2 < 0.98. In another embodiment, 0.90 < x2 < 0.98. For example, x2 is 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97 or 0.98.

[0058] In one embodiment of the method, the metal-based precursor is according to formula (II), wherein 0.01 < y2 < 0.15. In another embodiment, 0.01 < y2 < 0.10. For example, y2 is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10.

[0059] In one embodiment of the method, the metal-based precursor is according to formula (II), wherein 0.01 < z2 < 0.15. In another embodiment, 0.01 < z2 < 0.10. For example, z2 is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10.

[0060] In one embodiment of the method, the metal-based precursor is according to formula (II), wherein 0.70 < x2 < 0.98; 0.01 < y2 < 0.15; and 0.01 < z2 < 0.15. For example, Nio.94Mno.o3Coo.o3(OH)2.

[0061] In one embodiment of the method, the lithium source is LiOH, Li2COs or a mixture thereof.

[0062] In one embodiment of the method, the metal-based precursor is dry mixed with the lithium source.

[0063] In one embodiment of the method, the first mixture is heated at a temperature between 600 °C and 750 °C. For example, at 600 °C, 650 °C, 700 °C or 750 °C.

[0064] In one embodiment of the method, the first mixture is heated for a time between 2 hours and 20 hours. In another embodiment, for a time between 8 hours to 15 hours. For example, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours.

[0065] In one embodiment of the method, the niobium source is niobium oxide or lithium niobium oxide. For example, the niobium source is NbO, NbO?, Nb?O3, Nb?O5 or LiNbOs.

[0066] In one embodiment of the method, the first heated material is dry mixed with Nb20s.

[0067] In one embodiment of the method, the first heated material is dry mixed with a 0.05 mol% to 5 mol% of Nb20s. In another embodiment, the first heated material is dry mixed with 0.1 mol% to 0.5 mol% of Nb20s. For example, 0.1 mol%, 0.15 mol%, 0.2 mol%, 0.25 mol%, 0.3 mol%, 0.35 mol%, 0.4 mol%, 0.45 mol% or 0.5 mol%, of Nb20s.

[0068] In one embodiment of the method, the second mixture is heated at a temperature between 300 °C and 800 °C. For example, at 300 °C, 350 °C, 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C or 800 °C.

[0069] In one embodiment of the method, the second mixture is heated for a time between 2 hours and 15 hours. In another embodiment, for a time between 5 hours and 10 hours. For example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0070] In one embodiment, the method for manufacturing the cathode active material comprises the following steps: dry mixing Nio.94Mno.o3Coo.o3(OH)2 with LiOH in a blender, to obtain a first mixture having a Li / (Ni, Mn, and Co) atomic ratio of 1.03, heating the first mixture in an oxygen atmosphere at 740 °C for 12 hours to obtain a first heated material, dry mixing the first heated mixture with 0.1 mol% to 0.5 mol% of Nb20s to obtain a second mixture, and heating the second mixture at a temperature between 400 °C to 700 °C for 8 hours.Battery

[0071] In a third aspect, the present disclosure relates to a battery comprising the cathode active material according to the first aspect, or a cathode active material obtainable by the method according to the second aspect.

[0072] As appreciated by a person skilled in the art, all embodiments directed to the cathode active material according to the first aspect may apply mutatis mutandis to the second and third aspect of the present disclosure. Additionally, this disclosure is intended to cover the combination of all embodiments listed above.EXPERIMENTAL ANALYSIS USED IN THE EXAMPLES

[0073] The following analysis methods are used in the Examples.A) Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) analysis

[0074] The amount of Li, Ni, Co, Mn and Nb in the cathode active material powder is measured with the ICP-OES method by using an Agilent ICP 720-ES (Agilent Technologies). 2 grams of powder sample is dissolved into 10 mL of high purity hydrochloric acid (at least 37 wt% of HCI with respect to the total weight of solution) in an Erlenmeyer flask. The flask is covered by a glass and heated on a hot plate at 380 °C until complete dissolution of the powder. After being cooled to room temperature, the solution of the Erlenmeyer flask is poured into a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with deionized water up to the 250 mL mark, followed by complete homogenization.B) Brunauer-Emmett-Teller (BET) analysis

[0075] The specific surface area (SSA) of the cathode active material is measured with the Brunauer-Emmett-Teller (BET) method by using a Micromeritics Tristar II 3020. A powder is heated at 300 °C under nitrogen (N2) gas for 1 hour prior to the measurement in order to remove adsorbed species. The dried powder is put into the sample tube. The sample is then de-gassed at 30 °C for 10 minutes. The instrument performs the nitrogen adsorption test at 77 K. By obtaining the nitrogen isothermal absorption / desorption curve, the total specific surface area of the sample in m2 / g is derived.C) Titration analysis

[0076] To measure the total base content present in a sample by pH titration, two steps are performed:(a) the reparation of solution, and(b) pH titration. The detailed explanation of each step is as follows:

[0077] Step (a): The preparation of solution : 4 grams of cathode active material powder is mixed within 100 mL of deionized water and stirred for 10 min in a sealed glass flask. After stirring, the powder suspension is filtered to obtain the solution.

[0078] Step (b) : pH titration : 90 mL of the solution prepared in step (a) is used for pH titration by using 0.1M HCI. The flow rate is 0.5 mL / min and the pH value is recorded every 3 seconds. The pH titration profile (pH value as a function of added HCI) shows two clear equivalence (or inflection) points. The first equivalence point (corresponding to a HCI quantify of EPl) at around pH 7.4 results from the reaction of OH- and COs2-with H+. The second equivalencepoint (corresponding to a HCI quantify of EP2) at around pH 4.7 results from the reaction of HCOs’ with H+. It is assumed that the dissolved base in deionized water is either LiOH (with a quantify 2x(EPl-EP2)) or IJ2CO3 (with a quantify 2*(EP2-EP1)). The obtained values for LiOH and Li2COs are the result of the reaction of the surface with deionized water.

[0079] The following definitions are used for data analysis: LiOH (wt%) is the weight percentage of the amount of LiOH over the amount of sample. Li2COs (wt%) is the weight percentage of the amount of Li2COs over the amount of sample. Total base content (pmol / g) is the amount of LiOH and Li2COs over a gram of sample, i.e. the amount of micro mol of HCI needed to neutralize the base of 1 gram of cathode active material.D) Carbon analysis

[0080] The content of carbon of the cathode active material powder is measured by Horiba Emia-Expert carbon / sulfur analyzer. 1 gram of the cathode active material powder is placed in a ceramic crucible in a high frequency induction furnace. 1.5 grams of tungsten and 0.2 grams of tin are added into the crucible as accelerators. The powder is heated at a programmable temperature wherein gases produced during the combustion are then analyzed by Infrared detectors. The analysis of CO2 and CO determines the carbon concentration. The carbon concentration has a direct relation with the content of carbonate salts, such as Li2COs, present on the sample.E) X-Ray diffraction (XRD) analysis

[0081] The X-ray diffraction pattern of the cathode active material is collected with a Rigaku X-Ray Diffractometer (Ultima IV) using a Cu-Ka radiation source (40kV, 40mA) emitting at a wavelength of 1.5418 A. The instrument configuration is set at: a 1° Soller slit (SS), a 10mm divergent height limiting slit (DHLS), a 1° divergence slit (DS) ad a 0.3 mm reception slit (RS). The diameter of the goniometer is 158 mm. For the XRD, diffraction patterns are obtained in the range of 50to 85° (20) with a scan speed of 1.0° per min and a step-size of 0.02° per scan. The crystallite sizes are calculated from the diffraction angle and the full width at half maximum (FWHM) of the peak of the (104) plane obtained from the X-ray diffraction pattern using the known Scherrer equation:KA 0COS0T : Crystallite size (nm), being the mean size of the ordered (crystalline) domains, which may be smaller or equal to the grain sizeK: Scherrer constant, 0.9A: X-ray wavelength (CuKa = 1.5418 A) : Full width at half maximum (FWHM)9: XRD peak position, one half of 29

[0082] The peak of the (104) plane is observed at (around) 44.5±1° and (003) peak observed at (around) 18.6±1° which are assigned to a crystal structure with space group R-3m. All the Rietveld refinements of the XRD patterns were done with the FullProf program.F) X-ray Photoelectron Spectroscopy (XPS) analysis

[0083] The surface of the cathode active material is analyzed by using X-ray photoelectron spectroscopy (XPS). In XPS measurement, the signal is acquired from the first few nanometers (e.g. 1 nm to 10 nm) of the uppermost part of a sample, i.e. surface layer. Therefore, all elements measured by XPS are contained in the surface layer. For the surface analysis of cathode active material powder particles, XPS measurement is carried out using a Thermo K-a+ spectrometer (Thermo Scientific) https: / / www.thermofisher.com / order / catalog / product / IQLAADGAAFFACVMAHV).

[0084] Monochromatic Al Ka radiation (hv=1486.6 eV) is used with a spot size of 400 pm and measurement angle of 45°. A wide survey scan to identify elements present at the surface is conducted at 200 eV pass energy. Cis peak having a maximum intensity (or centered) at a binding energy of 284.8 eV is used as a calibrate peak position after data collection. Accurate narrow-scans are performed afterwards at 50 eV for at least 10 scans for each identified element to determine the precise surface composition.

[0085] Curve fitting is done with CasaXPS Version2.3.19PR1.0 (Casa Software, http: / / www.casaxps.com / ) using a Shirley-type background treatment and Scofield sensitivity factors. The fitting parameters are according to Table I. Line shape GL(30) is the Gaussian / Lorentzian product formula with 70 % Gaussian line and 30 % Lorentzian line. LA(a, P, m) was an asymmetric line-shape where a and define tail spreading of the peak and m define the width.Table I: XPS fitting parameter for Ni2p, Mn2p, Co2p, Nb3d.

[0086] For Mn and Co peaks, constraints are set for each defined peak according to Table II. All Ni3p peaks related including Ni3p3, Ni3pl, Ni3p3 satellite, and Ni3pl satellite are not quantified.Table II: XPS fitting Constraints for Ni2p, Mn2p, Co2p, and Nb3d.

[0087] The Nb surface contents (Nbxps) as determined by XPS is expressed as an atomic content of Nb in the surface layer of the particles divided by the total content of Ni, Mn, and Co in said surface layer. It is calculated as follow:NbxpsThe information of XPS peak position can be easily obtained in the regions and components report specification after fitting is conducted.

[0088] Nb coating is determined by a ratio of Nbxps / Nbicp. If Nbxps / Nbicp exceeds 1.0, it is regarded that Nb coating is conducted.G) Scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM- EDS) analysis

[0089] The content of Ni, Mn, Co, and Nb based on a total amount of the transition metals of the cathode active material are analyzed by a scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS) technique. The SEM-EDS is performed on a JEOL JSM 7100F SEM equipment with a 50mm2X-MaxNEDS sensor from Oxford instruments. The particles in the image should be well distributed therefore avoiding overlap between particles. This can be achieved by pouring a small amount of powder sample to the adhesive attached on the SEM sample holder and blowing air to remove the excess powder.H) Coin cell analysisHl) Coin cell preparation

[0090] For the preparation of a positive electrode, a slurry that contains a cathode active material powder, conductor (Super P, Timcal), binder (KF#9305, Kureha) - with a formulation of 96.5: 1.5:2.0 by weight - in a solvent (NMP, Mitsubishi) is prepared by a high-speed homogenizer. The homogenized slurry is spread on one side of an aluminum foil using a doctor blade coater with a 170 pm gap. The slurry coated foil is dried in an oven at 120 °C and then pressed using a calendaring tool. Then it is dried again in a vacuum oven to completely remove the remaining solvent in the electrode film. A coin cell is assembled in an argon-filled glovebox. A separator (Celgard 2320) is located between a positive electrode and a piece of lithium foil used as a negative electrode. IM LiPFe in EC / DMC (1 :2) is used as electrolyte and is dropped between separator and electrodes. Then, the coin cell is completely sealed to prevent leakage of the electrolyte.H2) Testing method

[0091] The testing method is a conventional "constant cut-off voltage" test. The conventional coin cell test in the present disclosure follows the schedule shown in Table III. Each cell is cycled at 25 °C using a Toscat-3100 computer-controlled galvanostatic cycling station (from Toyo).

[0092] The schedule uses a 1C current definition of 220 mA / g in the 4.3 V to 3.0 V / Li metal window range. The capacity fading rate (QF) is obtained according to an equation below wherein DQ1 is the discharge capacity at the first cycle.QF (% / 100 cycles) = 100 100Table III: Cycling schedule for coin cell testing methodEXAMPLES

[0093] The present disclosure is further illustrated in the following examples.Example 1

[0094] A cathode active material, further called EXI is obtained through following steps:1) Dry mixing the metal-based precursor Nio.94Mno.o3Coo.o3(OH)2 with LiOH in an industrial blender to obtain a first mixture having a Li / (Ni, Mn, and Co) ratio of 1.03.2) Heating the first mixture in an oxygen atmosphere at 740 °C for 12 hours to obtain a first heated material.3) Dry mixing the first heated mixture with 0.25 mol% of Nb2Os to obtain a second mixture.4) Heating the second mixture at 400 °C for 8 hours under an oxygen atmosphere and cooling to room temperature to obtain the cathode active material EXI.Example 2

[0092] EX 2 is prepared according to the same method as EX 1, except that the second heating temperature in step 4) is 500 °C.Example 3

[0093] EX 3 is prepared according to the same method as EX 1, except that the second heating temperature in step 4) is 600 °C.Example 4

[0094] EX 4 is prepared according to the same method as EX 1, except that the second heating temperature in step 4) is 700 °C.Comparative Example 1

[0095] A cathode active material, further called as CEX 1 is obtained through following steps:1) Dry mixing the metal-based precursor Nio.94Mno.o3Coo.o3(OH)2 with LiOH in an industrial blender to obtain a first mixture having a Li / (Ni, Mn, and Co) ratio of 1.03.2) Heating the first mixture in an oxygen atmosphere at 740 °C for 12 hours to obtain a first heated material.3) Heating the first heated material at 400 °C for 8 hours under an oxygen atmosphere and cooled to room temperature to obtain the cathode active material CEX 1.Comparative Example 2

[0096] CEX 2 is prepared according to the same method as CEX 1, except that the second heating temperature in step 3) is 500 °C.Comparative Example 3

[0097] CEX 3 is prepared according to the same method as CEX 1, except that the second heating temperature in step 3) is 600 °C.Comparative Example 4

[0098] CEX 4 is prepared according to the same method as CEX 1, except that the second heating temperature in step 3) is 700 °C.RESULTSTable IV: SSA, Nbxps, Nbxps / Nbicp ratio, carbon content, U2CO3 content, LiOH content and total base content of the examples and comparative examples.

[0099] In Table IV, the XPS analysis results of Nb (Nbxps) are compared with the ICP-OES results of Nb (Nbicp). A Nbxps / Nbicp ratio higher than 0 indicates the presence of Nb on the surface of the cathode active material. Additionally, a Nbxps / Nbicp ratio higher than 1 indicates that Nb is mainly on the surface of the cathode active material.

[0100] The Nbxps / Nbicp ratios of EX3 and EX4 are higher than 1, confirming the presence of Nb on the surface of the particles.

[0101] On the other hand, all the examples (EXI to EX4) have a lower carbon content than the corresponding comparative examples (CEX1 to CEX4). A lower carbon content is directly related with a lower content of carbonate salts, such as IJ2CO3. Therefore, a cathode active material according to this disclosure has a lower content of IJ2CO3, and might have an improved stability and battery performance compared to a cathode active material without Nb.

[0102] EXI and EX2 also present a lower total base content when compared with CEX1 and CEX2, indicating that they might minimize bulging effect and have improved stability.

[0103] Additionally, all examples (EXI to EX4) comprise particles with a low specific surface area (SSA), specifically lower than 0.33 m2 / g. Therefore, a battery comprising a cathode active material according to this disclosure might present an improved stability due to a lower interaction between the cathode active material particles and the electrolyte of a battery.Table V: Electrochemical properties (DQ7 and Qirr %) and crystalline size of the examples and the comparative examples.

[0104] The discharge capacity (DQ7) of EX2 is higher (218 mAh / g) than the DQ7 of corresponding comparative example CEX2 (216 mAh / g). A similar effect is also observed with EX3 and EX4 when compared with the corresponding CEX3 and CEX4.

[0105] Additionally, the irreversible capacity (Qirr %) of EXI is lower (8.5 %) than the CEX1(9.0 %). Therefore, a cathode active material according to this disclosure presents a higher discharge capacity (DQ7) and / or lower capacity fading.

Claims

CLAIMS1. A cathode active material for lithium batteries, wherein the cathode active material comprises Li, M, and O, wherein M comprises:Ni in an atomic x, wherein 0.60 < x < 0.98 relative to M;Co in an atomic y, wherein 0.005 < y < 0.30 relative to M;Mn in an atomic z, wherein 0.005 < z < 0.30 relative to M;Nb in an atomic a, wherein 0.001 < a < 0.10 relative to M; wherein x, y, z and a are determined by ICP-OES, x+y+z+a is 1, wherein the Li / M atomic ratio is between 0.8 to 1.5, wherein the cathode active material contains Li2COs in a mass content lower than 0.5% relative to the total mass of the cathode active material, as measured by titration analysis, and wherein the ratio Nbxps / Nbicp > 1, wherein Nbxps is the Nb atomic content relative to M as determined by XPS analysis, and wherein Nbicp is the Nb atomic content relative to M as determined by ICP analysis2. A cathode active material according to claim 1, having a specific surface area between 0.1 m2 / g and 0.5 m2 / g.

3. A cathode active material according to claim 1 or 2, comprising Nb in a content Nbicp and a content Nbxps, wherein the ratio Nbxps / Nbicp > 2.

4. A cathode active material according to any of the claims 1 to 3, wherein the cathode active material is according to the formula (I) LiwNixiMnyiCoziNbaiO2, wherein 0.80 < w < 1.50; 0.60 < xl < 0.98; 0.005 < yl < 0.30; 0.005 < zl < 0.30; 0.001 < al < 0.10; wherein xl, yl, zl and al are determined by ICP-OES, and xl+yl+zl+al is 1.

5. A cathode active material according to claim 4, wherein 0.80 < xl < 0.98, 0.01 < yl < 0.07, 0.01 < zl < 0.07.

6. A cathode active material according to claim 4 or 5, wherein 0.002 < al < 0.01.

7. A cathode active material according to any of the claims 1 to 6, wherein the total carbon content is lower than 0.08 % relative to the total mass of the cathode active material, as measured by carbon analysis.

8. A cathode active material according to any of the claims 1 to 7, wherein the Li2COs content is lower than 0.4 % relative to the total mass of the cathode active material, as measured by titration analysis.

9. A cathode active material according to any of the claims 1 to 8, wherein the total base content is lower than 400 pmol per gram of the cathode active material, as measured by titration analysis.

10. A method for manufacturing a cathode active material according to any of the claims 1 to 9, wherein the method comprises the following steps:- mixing a metal-based precursor with a lithium source to obtain a first mixture;- heating the first mixture at a temperature between 600 °C and 800 °C to obtain a first heated material;- mixing the first heated material with a Nb source to obtain a second mixture; and- heating the second mixture at a temperature between 200 °C and 800 °C to obtain the cathode active material.

11. A method according to claim 10, wherein the metal-based precursor is according to formula (II) NiX2Mny2Coz2(OH)2, wherein 0.60 < x2 < 0.98; 0.005 < y2 < 0.30; 0.005 < z2 < 0.30; wherein x2, y2 and z2 are measured by ICP-OES, and x2+y2+z2 is 1.

12. A method according to claim 10 or 11, wherein the lithium source is LiOH, IJ2CO3 or a mixture thereof; and the Nb source is NbO, NbC>2, Nb2Os, Nb2Os or LiNbOs.

13. A method according to any of the claims 10 to 12, wherein the metal-based precursor is dry mixed with LiOH; and wherein the first heated material is dry mixed with Nb2Os.

14. A battery comprising a cathode active material according to any of the claims 1 to 9, for electric vehicles (such as, but not limited to battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, extended range electric vehicles, fuel cell electric vehicles) for passenger or heavy-duty applications, two-wheeler transportation, energy storage systems, portable electronic devices, power tools, robotic devices, uninterruptible power supplies systems, telecommunication devices, defense applications, medical devices and aviation, aerospace, rail or marine devices and transportation systems, among other applications.

15. The use of a battery according to claim 14, in electric vehicles for passenger or heavy- duty applications, two-wheeler transportation, energy storage systems, portable electronic devices, power tools, robotic devices, uninterruptible power supplies systems, telecommunication devices, defense applications, medical devices and aviation, aerospace, rail or marine devices and transportation systems.

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