Positive electrode active material blend for sodium-ion batteries

Abstract

The present disclosure concerns a positive electrode active material blend for sodium-ion batteries comprising a first cathode active material CAM1 and a second cathode active material CAM2 in a weight ratio CAM1 / CAM2 from 90:10 to 65:35 and wherein CAM1 has a particle size distribution value D501 ranging from 8.0 μm to 15.0 μm and CAM2 has a particle size distribution value D502 ranging from 3.0 μm to 6.0 μm, and wherein the positive electrode active material blend has a particle size distribution value D50b ranging from 5.0 µm to 9.0 µm.

Description

DescriptionTitlePositive electrode active material blend for sodium-ion batteriesTechnical Field

[0001] The present disclosure concerns a positive electrode active material blend for sodium-ion batteries, a method for the manufacture of said positive electrode active material and a sodium ion battery comprising the same.Description of Related Art

[0002] Sodium-ion secondary batteries are rechargeable batteries that use sodium ions (Na+) as charge carriers, similar to lithium-ion batteries but with sodium as the intercalating ion. These batteries are gaining attention due to the abundance of sodium, lower cost, and environmental benefits compared to lithium-ion batteries. Sodium-ion batteries still need improvement in their performance in comparison to lithium ion batteries.Summary

[0003] The present disclosure concerns a positive electrode active material blend for sodium-ion battery comprising a first cathode active material CAM1 and a second cathode active material CAM2 in a weight ratio CAM1 / CAM2 from 90:10 to 65:35 and whereinCAM1 comprises Na, Mi and O, wherein Mi comprises:

[0004] Ni in an atomic content a1 , wherein 0.10<a1<0.40 relative to Mi,

[0005] Fe in an atomic content b1, wherein 0.10<b1<0.40 relative to Mi,

[0006] Mn in an atomic content c1, wherein 0.10<c1<0.40 relative to Mi,

[0007] Zn in an atomic content q1 , wherein 0.0 < q1 < 0.10 relative to Mi,

[0008] Ti in an atomic content f1 , wherein 0.0 < f1 < 0.20 relative to Mi,

[0009] D’ in an atomic content d1, wherein 0 < d1 < 0.20 relative to Mi, wherein D’ is at least one element selected from the group of Li, Mg, Al, B, Si, K, Ca, Co, Cu, Sr, Zr, Nb, Mo, Sn, and W,wherein a1, b1 , c1, q1, f 1 , and d1 are measured by ICP-OES, and a1 +b1 +c1 +d1 +q1 +f1 =1 ;CAM2 comprises Na, M2 and 0, wherein M2 comprises:

[0010] Ni in an atomic content a2, wherein 0.10<a2<0.40 relative to M2,

[0011] Fe in an atomic content b2, wherein 0.10<b2<0.40 relative to M2,

[0012] Mn in an atomic content c2, wherein 0.10<c2<0.40 relative to M2,

[0013] Zn in an atomic content q2, wherein 0.0 < q2 < 0.10 relative to M2,

[0014] Ti in an atomic content f2, wherein 0.0 < f2 < 0.20 relative to M2,

[0015] D” in an atomic content d2, wherein 0 < d2 < 0.20 relative to M2, wherein D” is at least one element selected from the group of Li, Mg, Al, B, Si, K, Ca, Co, Cu, Sr, Zr, Nb, Mo, Sn, and W,wherein a2, b2, c2, q2, f2, and d2 are measured by ICP-OES, and a2+b2+c2+d2+q2+f2=1, andCAM1 has a particle size distribution value D50i ranging from 8.0 pm to 15.0 pm as determined by particle size distribution analysis, and CAM2 has a particle size distribution value D502 ranging from 3.0 pm to 6.0 pm as determined by particle size distribution analysis, and wherein the positive electrode active material blend has a particle size distribution value D50b ranging from 5.0 pm to 9.0 pm as determined by particle size distribution analysis.

[0016] The present disclosure also relates to a sodium-ion secondary battery comprising a positive electrode active material according to this disclosure. The present disclosure also relates to the use of a sodium-ion secondary battery according to this disclosure, in an electrically powered device or system selected from the group consisting of: a portable computer, a tablet, a mobile phone, a telecommunication device, a power tool, mobile machinery, a robotic device, an energy storage system, an uninterruptible power supply system, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an extended-range electric vehicle, a fuel cell electric vehicle, a two-wheeler transportation system, a rail vehicle, a marine vessel, an aircraft, an aerospace system, a defense system, and a medical device.

[0017] The inventors have found that in sodium-ion batteries, such a positive electrode active material blend may lead to high discharge capacities at the same time as high pellet densities and high volumetric energy densities.Brief Description of the Drawings

[0018] Fig 1. SEM image of a cathode active material according to an embodiment of the present invention.Detailed Description

[0019] "about" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / -20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1 % or less, and still more preferably + / -0.1 % or less of and from the specified value, in so far such variations are appropriate to perform in the present disclosure. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed. Whether or not a numerical value or endpoint of a range in the specification recites “about,” the numerical value or endpoint of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0020] As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items, can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0021] “at%” signifies atomic percentage. The at% or “atomic percent” of a given element means a percentage of atoms of said element among all atoms in a claimed composition. Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) provides weight percent (wt%) of each element included in a material whose composition is determined by this technique. Conversion from wt% to at%, as is well known to the person skilled in the art, is as follows: at% of a first element Ei (Eati) in a material can be converted from a given wt% of said first element Ei (Ewti) in said material by applying the following formula,(^wtl I ^awi)Eatl x 100% ,T.i=i^wti I ^awi)wherein Eawiis a standard atomic weight (molecular weight) of the first element Ei, Ewti is wt% of an ithelement Ei, EaWiis a standard atomic weight (molecular weight) of said ithelement Ei, and n is an integer which represents the number of types of all elements included in the material.

[0022] Here within a range “from X to Y” or “between X and Y” or “ranging from X to Y” includes the endpoints X and Y.

[0023] The terms “comprises”, “comprising” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0024] In the following detailed description, preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. On the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description and accompanying drawings. Preferred embodiments of the different aspects of the invention can be combined with one another, unless it is specifically mentioned otherwise.

[0025] In an embodiment of the present disclosure, the sum of CAM1 and CAM2 are at least 90 wt% relative to the total mass of the positive electrode active material blend. In another embodiment, the sum of CAM1 and CAM2 are at least 95 wt%. In another embodiment, the sum of CAM1 and CAM2 are at least 98 wt%. In another embodiment, the positive electrode active material blend consists of CAM1 and CAM2.

[0026] In an embodiment of the present disclosure, CAMTs particle size distribution value D50i may be at least 8.0pm, at least 8.5pm, at least 9.0 pm, or at least 9.5 pm.

[0027] In an embodiment of the present disclosure, D50i may be at most 14.0 pm, at most 13.0 pm, at most 12.0 pm, at most 11.5 pm, at most 11.0 pm or at most 10.5 pm.

[0028] In an embodiment of the present disclosure, CAMTs particle size distribution value D50i may be about 10.0pm.

[0029] In an embodiment of the present disclosure, in CAM1, a1 may be at least 0.10 relative to Mi, at least 0.20 relative to Mi, or at least 0.30 relative to Mi.

[0030] In an embodiment of the present disclosure, a1 may be at most 0.40 relative to Mi or at most 0.35 relative to Mi.

[0031] In an embodiment of the present disclosure, in CAM1, a1 may be about 0.33 relative to Mi .

[0032] In an embodiment of the present disclosure, in CAM1, b1 may be at least 0.10 relative to Mi, at least 0.20 relative to Mi, or at least 0.30 relative to Mi.

[0033] In an embodiment of the present disclosure, b1 may be at most 0.40 relative to Mi or at most 0.35 relative to Mi.

[0034] In an embodiment of the present disclosure, in CAM1, b1 may be about 0.33 relative to Mi .

[0035] In an embodiment of the present disclosure, in CAM1, c1 may be at least 0.10 relative to Mi, at least 0.20 relative to Mi, or at least 0.30 relative to Mi.

[0036] In an embodiment of the present disclosure, c1 may be at most 0.40 relative to Mi or at most 0.35 relative to Mi.

[0037] In an embodiment of the present disclosure, in CAM1, c1 may be about 0.33 relative to Mi .

[0038] In an embodiment of the present disclosure, in CAM, q1 is 0 relative to Mi.

[0039] In an embodiment of the present disclosure, in CAM, f1 is 0 relative to Mi.

[0040] In an embodiment of the present disclosure, in CAM, d1 is 0 relative to Mi.

[0041] In an embodiment of the present disclosure, in CAM1, the atomic ratio Na / Mi ranges from 0.8 to 1.5.

[0042] In an embodiment of the present disclosure, CAM1 is according to a general formula (I) NaxiNiaiFebiMnciZnqiTifiD’diO2 (I), wherein 0.80<x1<1.50; 0.10<a1<0.40, 0.10<b1<0.40, 0.10<c1<0.40, 0.0 < q1 < 0.10, 0.0 < f1 < 0.20, 0 < d1 < 0.20, wherein x1 , a1 , b1 , c1 , q1 , f1 , and d1 are measured by ICP-OES, and a1 +b1 +c1 +d1 +q1 +f1 =1.

[0043] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein 0.20<a1<0.40.

[0044] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein 0.20<b1<0.40.

[0045] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein 0.20<c1<0.40.

[0046] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein q1 is 0.

[0047] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein f1 is 0.

[0048] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein d1 is 0.

[0049] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein 0.8<x1<1.50.

[0050] In an embodiment of the present disclosure, CAM1 is according to formula (I), wherein 0.80<x1<1.50; 0.20<a1<0.40; 0.20<b1<0.40; 0.20<c1<0.40; q1 is 0; f1 is 0; and d1 is 0.

[0051] In an embodiment of the present disclosure, CAM2’s particle size distribution value D502 may be at least 3.0pm, at least 3.5pm, or at least 4.0 pm.

[0052] In an embodiment of the present disclosure, D502 may be at most 6.0 pm, at most 5.5 pm, or at most 5.0 pm.

[0053] In an embodiment of the present disclosure, CAM2’s particle size distribution value D502 may be about 4.5 pm.

[0054] In an embodiment of the present disclosure, in CAM2, a2 may be at least 0.10 relative to M2, at least 0.20 relative to M2, or at least 0.30 relative to M2.

[0055] In an embodiment of the present disclosure, a2 may be at most 0.40 relative to M2 or at most 0.35 relative to M2.

[0056] In an embodiment of the present disclosure, in CAM2, a2 may be about 0.33 relative to M2.

[0057] In an embodiment of the present disclosure, in CAM2, b2 may be at least 0.10 relative to M2, at least 0.20 relative to M2, or at least 0.30 relative to M2.

[0058] In an embodiment of the present disclosure, b2 may be at most 0.40 relative to M2 or at most 0.35 relative to M2.

[0059] In an embodiment of the present disclosure, in CAM2, b2 may be about 0.33 relative to M2.

[0060] In an embodiment of the present disclosure, in CAM2, c2 may be at least 0.10 relative to M2, at least 0.20 relative to M2, or at least 0.30 relative to M2.

[0061] In an embodiment of the present disclosure, c2 may be at most 0.40 relative to M2 or at most 0.35 relative to M2.

[0062] In an embodiment of the present disclosure, in CAM2, c2 may be about 0.33 relative to M2.

[0063] In an embodiment of the present disclosure, in CAM2, q2 is 0 relative to M2.

[0064] In an embodiment of the present disclosure, in CAM2, f2 is 0 relative to M2.

[0065] In an embodiment of the present disclosure, in CAM2, d2 is 0 relative to M2.

[0066] In an embodiment of the present disclosure, in CAM2, the atomic ratio Na / M2 ranges from 0.8 to 1.5.In an embodiment of the present disclosure, CAM2 is according to a general formula (II) Nax2Nia2Feb2MnC2Znq2Tif2D”d2O2 (II), wherein 0.80<x2<1.50; 0.10<a2<0.40, 0.10<b2<0.40, 0.10<c2<0.40, 0.0 < q2 < 0.10, 0.0 < f2 < 0.20, 0 < d2 < 0.20, wherein x2, a2, b2, c2, q2, f2, and d2 are measured by ICP-OES, and a2+b2+c2+d2+q2+f2=1.

[0067] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein 0.20<a2<0.40.

[0068] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein 0.20<b2<0.40.

[0069] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein 0.20<c2<0.40.

[0070] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein q2 is 0.

[0071] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein f2 is 0.

[0072] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein d2 is 0.

[0073] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein 0.8<x2<1.50.

[0074] In an embodiment of the present disclosure, CAM2 is according to according to formula (II), wherein 0.80<x2<1.50; 0.20<a2<0.40; 0.20<b2<0.40; 0.20<c2<0.40; q2 is 0; f2 is 0; and d2 is 0.

[0075] In an embodiment of the present disclosure, the positive electrode active material blend for sodium-ion battery may have a particle distribution span ranging from 0.75 to 1.10. In particular, the span may be at least 0.76 or even at least 0.77. In particular, the span may be at most 1.09 or at most 1.08.

[0076] In an embodiment of the present disclosure, the weight ratio CAM1 / CAM2 may range from 90:10 to 70:30, in particular from 85:15 to 75:25. Particularly high pellet densities may be obtained in these weight ratio ranges.

[0077] In an embodiment of the present disclosure, CAM1 comprises first secondary particles consisting of a plurality of first primary particles, and CAM2 comprises second secondary particles consisting of a plurality of second primary particles. It was found that such secondary particles may show higher resistance to the stress and strain from volume changes during battery cycling than monolithic particles. The morphology of CAM1 and CAM2 may be confirmed by scanning electron microscopy (SEM) measurements.

[0078] In an embodiment of the present invention, the positive electrode material blend comprises Na, M and O, wherein M comprises

[0079] Ni in an atomic content a wherein 0.10<a<0.40 relative to M,

[0080] Fe in an atomic content b, wherein 0.10<b<0.40 relative to M,

[0081] Mn in an atomic content c, wherein 0.10<c<0.40 relative to M,

[0082] D in an atomic content d, wherein 0 < d < 0.20 relative to M, and wherein D is at least one element selected from the group of Li, Mg, Al, B, Si, K, Ca, Ti, Fe, Co, Cu, Zn, Sr, Zr, Nb, Mo, Sn, and W,wherein a, b, c, and d are measured by ICP-OES, and a+b+c+d=1.0

[0083] In an embodiment of the present disclosure, in the positive electrode material blend, the atomic ratio Na / M ranges from 0.8 to 1.5.In an embodiment of the present disclosure, the positive electrode material blend is according a general formula (III) NaxNiaFebMncZnqTifDdO2 (III), wherein 0.80<x<1.50; 0.10<a<0.40, 0.10<b<0.40, 0.10<c<0.40, 0.0 < q < 0.10, 0.0 < f < 0.20, 0 < d < 0.20, wherein x, a, b, c, q, f, and d are measured by ICP-OES, and a+b+c+d+q+f=1.

[0084] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein 0.20<a<0.40.

[0085] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein 0.20<b<0.40.

[0086] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein 0.20<c<0.40.

[0087] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein q is 0.

[0088] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein f is 0.

[0089] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein d is 0.

[0090] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein 0.8<x<1.50.

[0091] In an embodiment of the present disclosure, the positive electrode material blend is according to formula (III), wherein 0.80<x<1.50; 0.20<a<0.40; 0.20<b<0.40; 0.20<c<0.40; q is 0; f is 0; and d is 0.

[0092] In an embodiment of the present disclosure, CAM1 and CAM2 have identical compositions. In another embodiment, CAM1 and CAM2 have different compositions.

[0093] The present disclosure further concerns a method for preparing a positive electrode material blend, in particular a blend of the present disclosure according to any embodiment or combination of embodiments, comprising a first and a second positive electrode material, comprising:

[0094] For obtaining a first electrode active material CAM1 :

[0095] mixing a first starting material comprising a first sodium source and a first transition metal composite precursor P1 to obtain a first mixture; P1 having a particle size distribution value D50PI ranging from 8.0 pm to 15.0 pm;

[0096] heating the first mixture up to a temperature ranging from 700°C to 1000 °C, then crushing and sieving the heated first mixture to obtain a first electrode active material.

[0097] For obtaining a second positive electrode active material CAM2:

[0098] mixing a second starting material comprising a second sodium source and a second transition metal composite precursor P2 to obtain a second mixture, P2 having a particle size distribution value D50P2 ranging from 3.0 pm to 6.0 pm;

[0099] heating the second mixture up to a temperature ranging from 700°C to 1000 °C, then crushing and sieving the heated product to obtain a second electrode active material.

[0100] mixing the first and second positive electrode active material powders, so as to obtain the positive electrode active material blend.

[0101] In an embodiment of the method of the present disclosure, the positive electrode material blend obtained by the method is a positive electrode material blend of the present disclosure according to any embodiment or combination of embodiments disclosed herein.

[0102] In an embodiment of the present disclosure, the first and second sodium sources are Na2CO3.

[0103] In an embodiment of the present disclosure, the first and second transition metal composite precursors are independently chosen from an oxide, an oxyhydroxide, or a hydroxide of transition metals.

[0104] In an embodiment of the present disclosure the transition metals in P1 comprise

[0105] Ni in an atomic content a3 wherein 0.10<a3<0.40 relative to the sum of all transition metals,

[0106] Fe in an atomic content b3, wherein 0.10<b3<0.40 relative to the sum of all transition metals,

[0107] Mn in an atomic content c3, wherein 0.10<c3<0.40 relative to the sum of all transition metals,wherein a3, b3, and c3 are measured by ICP-OES.

[0108] In an embodiment of the present disclosure the transition metals in P2 comprise

[0109] Ni in an atomic content a4 wherein 0.10<a4<0.40 relative to the sum of all transition metals,

[0110] Fe in an atomic content b4, wherein 0.10<b4<0.40 relative to the sum of all transition metals,

[0111] Mn in an atomic content c4, wherein 0.10<c4<0.40 relative to the sum of all transition metals,wherein a4, b4, and c4 are measured by ICP-OES.

[0112] In an embodiment of the method of the present disclosure, the first positive electrode active material is of the composition of CAM1 according to any embodiment or combination of embodiments disclosed herein above.

[0113] In an embodiment of the method of the present disclosure, the second positive electrode active material is of the composition of CAM2 according to any embodiment or combination of embodiments disclosed herein above.

[0114] Pressed density (PD) - The pressed density is measured as follows: 3 g of powder is filled into a pellet die with a diameter "d" of 1.30 cm. A uniaxial load of 2.8 tons, corresponding to a pressure of 207MPa, is applied for 30 seconds. After relaxing the load, the thickness "t" of the pressed powder is measured. The pellet density in g / cm3is then calculated as follows: PD=3 / (irx(d / 2)2xt).

[0115] Scanning Electron Microscopy (SEM) - The morphology of positive electrode active materials is analyzed by a Scanning Electron Microscopy (SEM) technique. The measurement is performed using a ZEISS SIGMA 300 under a high vacuum environment of 8x1 O’6Pa at 25 °C. 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 dry air to remove the excess powder.

[0116] Particle size - The particle size distribution (PSD) of the positive electrode active material powders is measured using a Malvern Mastersizer 3000 equipped with anAero S dry dispersion accessory. The powders are introduced into the instrument through a dry feeder system, where they are dispersed in a stream of compressed air. To ensure effective dispersion and prevent agglomeration, the air pressure is set at 2 bars. The D50 values - D50i, D502, D50i2 - are defined as the particle size at which 50% of the cumulative volume is smaller and 50% is larger. The PSD Span refers to the width of a particle size distribution. It is calculated using the formula: Span = (D90 - D10 / D50, where: D90 is the particle size below which 90% of the sample's volume is contained, D10 is the particle size below which 10% of the sample's volume is contained, and D50 is the median particle size, meaning 50% of the sample's volume is below this size. This formula gives an indication of how far apart the 10% and 90% points are normalized with the midpoint.

[0117] Coin cell preparation - The method comprises forming a slurry comprising a positive electrode active material powder, a conductive material (Super P, Timcal), and a binder (KF#9700, Kureha) in a weight ratio of 92:4.0:4.0, respectively, in a solvent (NMP, Mitsubishi). The slurry is homogenized using a high-speed homogenizer. The homogenized slurry is then uniformly applied to one side of an aluminum foil substrate using a doctor's blade coater with a gap of 230 pm. The coated foil is subsequently dried in an oven at a temperature of 120 °C. Following the drying step, the coated foil is pressed using a calendaring tool and then subjected to a second drying process in a vacuum oven to ensure complete removal of the solvent from the electrode film. The coin cell is assembled within an argon-filled glovebox to prevent contamination. A separator (glass microfiber filter) is placed between the positive electrode and a piece of sodium foil, which serves as the negative electrode. An electrolyte solution comprising 0.6M NaPFe in a mixture of propylene carbonate (PC) and fluoroethylene carbonate (FEC) in a volume ratio of 3:7 is added between the separator and the electrodes. The coin cell is then sealed to prevent electrolyte leakage, completing the assembly process.

[0118] Coin cell testing - The tests for discharge capacity (DQ) and irreversible capacity (Qirr) are performed using coin cells with electrodes consisting of 92 wt% of the cathode active material described in this invention. The electrode loading is approximately 9.5 mg / cm2. The discharge capacity for the first cycle (DQ1) is measured within the voltage range of 4.0-2.2 V at a rate of 1C (expressed in mAh / g) at a temperature of 25°C.Examples and comparative examples

[0119] The first positive electrode active material CAM1 was obtained in a dry room through the following steps:

[0120] Mixing: Nio.3Feo.3Mno.3(OH)2 precursor, having a PSD value D50 of about 9.6 pm, was homogeneously mixed with Na2COs to prepare a mixture, wherein molar ratio of Na to total amount of Ni, Fe, and Mn was 1.02;

[0121] Heating: the mixture was heated at 900 °C for 12 hours under air atmosphere followed by cooling, crushing, and sieving so as to obtain a positive electrode active material CAM 1 of composition Nai.o2Nio.33Feo.33Mno.3302(D50i = 9.69 pm)

[0122] The second positive electrode active material CAM2 was obtained in a dry room through the following steps:

[0123] Mixing: Nio.3Feo.3Mno.3(OH)2, having a PSD value D50 of about 4.4 pm, was homogeneously mixed with Na2CO3 to prepare a mixture, wherein molar ratio of Na to total amount of Ni, Fe, and Mn was 1.02;

[0124] Heating: the mixture was heated at 900 °C for 12 hours under air atmosphere followed by cooling, crushing, and sieving so as to obtain a positive electrode active material CAM 2 of composition Na1.02Ni0.33Fe0.33Mn0.33O2 (D502 = 4.44 pm).

[0125] Example 1 - Positive electrode active material blend EX1 was obtained by blending CAM1 and CAM2 homogeneously, using a mass ratio of CAM1 to CAM2 is 90:10.

[0126] Example 2 - Positive electrode active material blend EX2 was obtained by blending CAM1 and CAM2 homogeneously, using a mass ratio of CAM1 to CAM2 is 85:15.

[0127] Example 3 - Positive electrode active material blend EX3 was obtained by blending CAM1 and CAM2 homogeneously, using a mass ratio of CAM1 to CAM2 is 80:20.

[0128] Example 4 - Positive electrode active material blend EX4was obtained by blending CAM1 and CAM2 homogeneously, using a mass ratio of CAM1 to CAM2 is 75:25.

[0129] Example 5 - Positive electrode active material blend EX5 was obtained by blending CAM1 and CAM2 homogeneously, using a mass ratio of CAM1 to CAM2 is 70:30.

[0130] Comparative Example 1 - Positive electrode active material CEX1 comprised with CAM2 100%.

[0131] Comparative Example 2 - Positive electrode active material CEX2 comprised with CAM1 100%.

[0132] Comparative Example 3 - Positive electrode active material blend CEX3 was obtained by blending CAM1 and CAM2 homogeneously, using a mass ratio of CAM1 to CAM2 is 65:35.

[0133] The prepared examples and comparative examples were analyzed using pressed density test, Scanning Electron Microscopy (SEM), Particle Size Distribution test (PSD), and coin cell test to evaluate their characteristics, morphology, and electrochemical performance.

[0134] The summary of the blending of the examples and comparative examples, along with the morphology and corresponding electrochemical properties, are shown in Table 1. The indicated discharge capacity and volumetric energy density are calculated from the first charge / discharge cycle.0135] Table 1Initial Discharge Volumetric energy D50i D502CAM 1: CAM 2 Blend D50 Pellet densityID Blend PSD Span capacity DQ1 density (Wh / L)(pm) (pm) weight ratio (pm) (g / cm3)(mAh / g)EX1 9.69 4.44 90:10 9.06 0.773 3.02 147.4 1379 EX2 9.69 4.44 85:15 8.74 0.913 3.04 145.5 1371 EX3 9.69 4.44 80:20 8.55 0.926 3.07 146.1 1391 EX4 9.69 4.44 75:25 8.19 1.027 3.06 146.6 1393 EX5 9.69 4.44 70:30 7.92 1.079 3.05 145.4 1375 CEX1 9.69 4.44 0:100 4.44 1.296 2.71 142.6 1199 CEX2 9.69 4.44 100:0 9.69 0.702 2.72 147.1 1240 CEX3 9.69 4.44 65:35 7.74 1.135 3.05 141.8 1344

[0136] As can be seen in Table 1 on EX1 to EX5 with a CAM1 :CAM2 weight ratio of at least 90:10 and less than 65:35, particularly high discharge capacities are obtained at the same time as high pellet densities and high volumetric energy densities. CAM1:CAM2 weight ratios of at most 80:20 and not less than 75:25 provide particularly high pellet densities, as shown in EX3 and EX4.

[0137] CEX1, and CEX3 provide lesser discharge capacities whereas CEX1 and CEX2 provide low volumetric energetic densities compared to EX1 to EX5.

Claims

Claims1. A positive electrode active material blend for sodium-ion battery comprising a first cathode active material CAM1 and a second cathode active material CAM2 in a weight ratio CAM1 / CAM2 of from 90:10 and to 65:35,wherein CAM1 comprises Na, Mi and O, wherein Mi comprises: - Ni in an atomic content a1 wherein 0.10<a1<0.40 relative to Mi,- Fe in an atomic content b1, wherein 0.10<b1<0.40 relative to Mi,- Mn in an atomic content c1 , wherein 0.10<c1<0.40 relative to Mi,- Zn in an atomic content q1 , wherein 0.0 < q0.10 relative to Mi,- Ti in an atomic content f1 , wherein 0.0 < f0.20 relative to Mi ,- D’ in an atomic content d1, wherein 0 < d1 < 0.20 relative to Mi,wherein D’ is at least one element selected from the group of Li, Mg, Al, B, Si, K, Ca, Co, Cu, Sr, Zr, Nb, Mo, Sn, and W, wherein a1, b1, c1, q1, f 1 , and d1 are measured by ICP-OES, and a1 +b1 +c1 +d1 +q1 +f1 =1 ,wherein CAM2 comprises Na, M2 and O, wherein M2 comprises: - Ni in an atomic content a2 wherein 0.10<a2<0.40 relative to M2,- Fe in an atomic content b2, wherein 0.10<b2<0.40 relative to M2,- Mn in an atomic content c2, wherein 0.10<c2<0.40 relative to M2,- Zn in an atomic content q2, wherein 0.0 < q20.10 relative to M2,- Ti in an atomic content f2, wherein 0.0 < f20.20 relative to M2,- D” in an atomic content d2, wherein 0 < d2 < 0.20 relative to M2,wherein D” is at least one element selected from the group of Li, Mg, Al, B, Si, K, Ca, Co, Cu, Sr, Zr, Nb, Mo, Sn, and W, wherein a2, b2, c2, f2, q2, and d2 are measured by ICP-OES, and a2+b2+c2+d2+f2+q2=1 ,and CAM1 has a particle size distribution value D50i ranging from 8.0 pm to 15.0 pm as determined by particle size distribution analysis, and CAM2 has a particle size distribution value D502 ranging from 3.0 pm to 6.0 pm as determined by particle size distribution analysis, and wherein the positive electrode active material blend has a particle size distribution value D50b ranging from 5.0 pm to 9.0 pm as determined by particle size distribution analysis.

2. A positive electrode active material blend according to claim 1, wherein 0.20<a1<0.40 relative to Mi, and 0.20<a2<0.40 relative to M2.

3. A positive electrode active material blend according to claim 1 or 2, wherein 0.20<b1<0.40 relative to Mi, and 0.20<b2<0.40 relative to M2.

4. A positive electrode active material blend according to any of the claims 1 to 3, wherein 0.20<c1<0.40 relative to Mi.and 0.20<c2<0.40 relative to M2.

5. A positive electrode active material blend according to any of the claims 1 to 4, wherein q1 is 0 relative to Mi, and q2 is 0 relative to M2.

6. A positive electrode active material blend according to any of the claims 1 to 5, wherein f1 is 0 relative to Mi, and f2 is 0 relative to M2.

7. A positive electrode active material blend according to any of the claims 1 to 6, wherein d1 is 0 relative to Mi, and d2 is 0 relative to M2.

8. A positive electrode active material blend according to any of the claims 1 to 7, having a particle distribution span ranging from 0.75 to 1.10.

9. A positive electrode active material blend according to any of the claims 1 to 8, wherein the sum of CAM1 and CAM2 are at least 90 wt% relative to the total mass of the positive electrode active material blend.

10. A positive electrode active material blend according to any of the claims 1 to 9, comprising CAM1 , wherein CAM1 is according to formula (I) NaxiNiaiFebiMnciZnqiTifiD’diO2 (I), wherein 0.80<x1<1.50, 0.20<a1<0.40, 0.20<b1<0.40, 0.20<c1<0.40, q1 is 0, f1 is 0, d1 is 0, wherein x1, a1, b1, c1, q1, f 1 , and d1 are measured by ICP-OES, and a1 +b1 +c1 +d1 +q1 +f1 =1 ; and CAM2, wherein CAM2 is according to formula (II) Nax2Nia2Feb2MnC2Znq2Tif2D”d2O2 (II), wherein 0.80<x2<1.50; 0.20<a2<0.40, 0.20<b2<0.40, 0.20<c2<0.40, q2 is 0, f2 is 0, d2 is 0, wherein x2, a2, b2, c2, q2, f2, and d2 are measured by ICP-OES, and a2+b2+c2+d2+q2+f2=1.

11. Method for preparing a positive electrode material blend according to any of the claims 1 to 10, comprising:For obtaining a first electrode active material CAM1 :- mixing a first starting material comprising a first sodium source and a first transition metal composite precursor P1 to obtain a first mixture; P1 having a particle size distribution value D50PI ranging from 8.0 pm to 15.0 pm;- heating the first mixture up to a temperature ranging from 700°C to 1000 °C, then crushing and sieving the heated first mixture to obtain a first electrode active material.For obtaining a second positive electrode active material CAM2:- mixing a second starting material comprising a second sodium source and a second transition metal composite precursor P2 to obtain a second mixture, P2 having a particle size distribution value D50P2 ranging from 3.0 pm to 6.0 pm;- heating the second mixture up to a temperature ranging from 700°C to 1000 °C, then crushing and sieving the heated product to obtain a second electrode active material, and- mixing the first and second positive electrode active material powders, so as to obtain the positive electrode active material blend.

12. Method according to claim 11, wherein P1 comprises Ni in a content a3 wherein 0.10s£a3s=0.40 relative to the sum of all transition metals, Fe in a content b3, wherein 0.10s£b3s=0.40 relative to the sum of all transition metals, Mn in a content c3, wherein 0.10s£c3s=0.40 relative to the sum of all transition metals, wherein a3, b3, and c3 are measured by ICP-OES.

13. Method according to claim 11 or 12, wherein P2 comprises Ni in a content a4 wherein 0.10s£a4s=0.40 relative to the sum of all transition metals, Fe in a content b4, wherein 0.10s£b4s=0.40 relative to the sum of all transition metals, Mn in a content c4, wherein 0.10s£c4s=0.40 relative to the sum of all transition metals, wherein a4, b4, and c4 are measured by ICP-OES.

14. Sodium-ion secondary battery comprising a positive electrode active material blend according to any of the claims 1 to 10.

15. The use of a sodium-ion secondary battery according to claim 14, in an electrically powered device or system selected from the group consisting of: a portable computer, a tablet, a mobile phone, a telecommunication device, a power tool, mobile machinery, a robotic device, an energy storage system, an uninterruptible power supply system, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an extended-range electric vehicle, a fuel cell electric vehicle, atwo-wheeler transportation system, a rail vehicle, a marine vessel, an aircraft, an aerospace system, a defense system, and a medical device.

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