A cathode active material for sodium batteries

Abstract

The present disclosure concerns a cathode active material for sodium batteries, wherein the cathode active material comprises Na, M, and O, wherein M comprises, relative M, Ni in an atomic content x, wherein 0.10 ≤ x ≤ 0.60; Fe in an atomic content y, wherein 0.0 ≤ y ≤ 0.60; Mn in an atomic content z, wherein 0.10 ≤ z ≤ 0.60; Zn in an atomic content q, wherein 0.0 < q ≤ 0.15; Ti in an atomic content f, wherein 0.0 < f ≤ 0.20; B in an atomic content a, wherein 0.0001 ≤ a ≤ 0.05 relative to M, x+y+z+q+f+a is 1, the Na / M ratio is between 0.8 to 1.5.

Description

DescriptionTitleA CATHODE ACTIVE MATERIAL FOR SODIUM BATTERIESTechnical Field

[0001] The present invention relates to a cathode active material for sodium batteries and a method for the manufacture thereof.Description of Related Art

[0002] A major drawback of sodium batteries is the sensitivity of its cathode active materials to expo-sure to ambient air. 03 phase layered oxides of Ni, Fe, and Mn were found to provide high levels of capacity as well as high voltage levels. The performance of these materials relies heavily on the predominance of an 03 phase, which however readily transforms into a P2 phase during battery manufacture.

[0003] Such a phase transformation readily occurs upon prolonged storage of the cathode active material in particular in the presence of humidity and also upon exposure to ambient air. Storage of such materials may thus be severely limited.Summary

[0004] An objective of the present disclosure is to provide a cathode active material for sodium batteries, with improved storage stability.

[0005] In a first aspect of the present disclosure provides a cathode active material for sodium batteries, wherein the cathode active material comprises Na, M, and O, wherein M comprises:a. Ni in an atomic content x, wherein 0.10 < x < 0.60 relative to M,b. Fe in an atomic content y, wherein 0.0 < y < 0.60 relative to M,c. Mn in an atomic content z, wherein 0.10 < z < 0.60 relative to M,d. Zn in an atomic content q, wherein 0.0 < q < 0.15 relative to M,e. Ti in an atomic content f, wherein 0.0 < f < 0.20 relative to M,f. B in an atomic content a, wherein 0.0001 < a < 0.05 relative to M, wherein x, y, z, q, f and a are measured by ICP-OES, x+y+z+q+f+a = 1 , the Na / M molar ratio ranges from 0.8 to 1.5.

[0006] The inventors found that cathode active material of the present disclosure in particular shows little degradation upon storage, in particular under humid conditions. Such degradation may be established as the loss of 03 phase material.

[0007] A further aspect of the present disclosure refers to a method for the manufacture of cathode active material for sodium batteries, in particular a cathode active material according the present disclosure according to any of its embodiments or combination of embodiments. The method comprises:a. providing a starting material comprising Na, M’, and O, in particular wherein M’ comprises:i. Ni in an atomic content x2, wherein 0.10 < x2 < 0.60 relative to M’, ii. Fe in an atomic content y2, wherein 0.0 < y2 < 0.60 relative to M’, iii. Mn in an atomic content z2, wherein 0.10 < z2 < 0.60 relative to M, iv. Zn in an atomic content q2, wherein 0.0 < q2 < 0.15 relative to M’, v. Ti in an atomic content f2, wherein 0.0 < f2 < 0.20 relative to M’, wherein x2, y2, z2, q2, and f2 are measured by ICP-OES, x2+y2+z2+q2+f2= 1 , the Na / M’ molar ratio is between 0.8 to 1.5;b. blending the starting material with a boron source, in particular boric acid, to obtain a first mixture;c. heating the first mixture up to a temperature Tmax of up to 600°C;d. cooling down the heated first mixture and to obtain the cathode active material;wherein the Boron source to starting material ratio added so as to obtain a B content in the cathode active material ranging from 500 ppm to 1500 ppm.Brief description of the figures

[0008] Figure 1 is an SEM image of a cathode active material according to an embodiment of the present disclosure.

[0009] Figure 2 is an SEM image of is an SEM image of a cathode active material not according to an embodiment of the present disclosure.Detailed Description

[0010] "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.

[0011] 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.

[0012] “D50” as used herein refers to a particle size at 50% of cumulative volume% distribution when measured by laser scattering method. The method of measuring D50 by laser scattering method is described herein below.

[0013] 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. To the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description and accompanying drawings. Embodiments of the different aspects of the invention can be combined with one another, unless it is specifically mentioned otherwise.

[0014] The cathode active material of the present disclosure may in particular comprise secondary particles comprising a plurality of primary particles, in particular at least 20 primary particles. Such a polycrystalline material may provide an higher contact area with the electrolyte in a battery, thus increasing the battery’s performance. At least about 30% of the particles, more preferably at least about 50% of the particles, constituting the powder observed in a Scanning Electron Microscope (SEM) image may be such secondary particles. The number of primary particles constituting the monolithic particle is determined in a field of view of at least about 45 pm x at least about 60 pm (i.e. of atleast about 2700 pm2), preferably of: at least about 100 pm x about 100 pm (i.e. of at least about 10,000 pm2). The particles in the image may 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. In the context of the present disclosure, primary particles may be distinguished from each other in a SEM image by observing grain boundaries between the primary particles. A grain boundary is defined as the interface between two primary particles, preferably wherein the atomic planes of the two primary particles are aligned to different orientations and meet as a crystalline discontinuity.

[0015] In the cathode active material of the present disclosure, Ni, Fe, Mn, Zn, and Ti may be uniformly distributed throughout the secondary and / or primary particles.

[0016] In an embodiment of the present disclosure, the cathode active material according to the first aspect, has a particle size distribution value D50 lower than 15 pm.

[0017] In an embodiment of the present disclosure, the cathode active material according to the first aspect, has a particle size distribution value D50 of at least 4pm.

[0018] In an embodiment of the present disclosure, the cathode active material according to the first aspect, has a particle size distribution value D50 ranging from about 5pm to about 7pm.

[0019] In a further implementation of the cathode active material according to the first aspect, the BXPS / BICP ratio is higher than 10, wherein BXPS is the content of boron relative to the total content of Ni, Fe, Mn, Zn, Ti and B, as measured by X-ray photo electron spectroscopy, and BICP is the B content relative to the total content of Ni, Fe, Mn, Zn, Ti and B, as measured by ICP-OES. In another embodiment, the BXPS / BICP ratio is higher than 20. In another embodiment, the BXPS / BICP ratio is higher than 40.

[0020] In an embodiment of the present disclosure, the cathode active material further comprises carbonate CO3 in a weight percentage ranging of at least 0.20 weight %.

[0021] In an embodiment of the present disclosure, the cathode active material further comprises carbonate CO3 in a weight percentage ranging of at most 0.35 weight %.

[0022] In an embodiment of the present disclosure, 0.20 < x < 0.50 relative to M, preferably 0.30 < x < 0.45 relative to M.

[0023] In an embodiment of the present disclosure, y is 0 relative to M.

[0024] In an embodiment of the present disclosure, 0.30 < z < 0.60 relative to M, preferably 0.40 < z < 0.55 relative to M.

[0025] In an embodiment of the present disclosure, 0.001 < q < 0.10 relative to M, preferably 0.005 < q < 0.07 relative to M, more preferably 0.01 < q < 0.07 relative to M.

[0026] In an embodiment of the present disclosure, 0.001 < f < 0.20 relative to M, preferably 0.01 < f < 0.15 relative to M, more preferably 0.05 < f < 0.12 relative to M.

[0027] In an embodiment of the present disclosure, 0.001 < a < 0.03 relative to M, preferably 0.005 < a < 0.020 relative to M, more preferably 0.007 < a < 0.015 relative to M.

[0028] In an embodiment of the present disclosure, the Na, M, and O content of the cathode active material is represented by the formula (I) NawNixiFeyiMnziZnqiTifiBaiO2, (I) wherein 0.80 < w < 1.50; 0.10 < x1 < 0.60; 0.0 < y1 < 0.60; 0.10 < z1 < 0.60; 0.0 < q1 < 0.15; 0.0 < f1 < 0.20; 0.0001 < a1 < 0.05; wherein x1, y1 , z1 , q1 , f1 and a1 are measured by ICP-OES, and x1 +y1 +z1 +q1 +f1 +a1 is 1.

[0029] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein 0.20 < x1 < 0.50, preferably 0.30 < x1 < 0.45.

[0030] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein y1 is 0.

[0031] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein 0.30 < z1 < 0.60, preferably 0.40 < z1 < 0.55.

[0032] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein 0.001 < q1 < 0.10, preferably 0.005 < q1 < 0.07, more preferably 0.01 < q1 < 0.07.

[0033] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein 0.001 < f1 < 0.20, preferably 0.01 < f1 < 0.15, more preferably 0.05 < f1 < 0.12.

[0034] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein 0.001 < a1 < 0.03, preferably 0.005 < a1 < 0.02, more preferably 0.007 < a1 < 0.015.

[0035] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein 0.15 < x1 < 0.50, 0.15 < y1 < 0.50, 0.15 < z1 < 0.50, q1 is 0 and f1 is 0.

[0036] In an embodiment of the present disclosure, the cathode active material is according to formula (I), wherein 0.20 < x1 < 0.50; y1 is 0; 0.30 < z1 < 0.60; 0.001 < q1 < 0.10; 0.001 < f1 < 0.20; and 0.001 < a1 < 0.03.

[0037] In an embodiment of the method of the present disclosure, calcination is performed under dry air, in particular performed under an atmosphere having a dew point of less than -20°C, preferably less than -30°C.

[0038] In an embodiment of the method of the present disclosure, the calcined blend is sieved.

[0039] In an embodiment of the method of the present disclosure, the starting material comprises secondary particles comprising a plurality of primary particles. Starting material secondary particles may in particular comprise at least 20 primary particles.

[0040] In an embodiment of the method of the present disclosure, Tmax ranges from 150°C to 500°C.

[0041] In an embodiment of the method of the present disclosure, after heating the first mixture up to a temperature Tmax, and before cooling, the first mixture is maintained at Tmax for a duration of at least 2h and of at most 10h.

[0042] In an embodiment of the method of the present disclosure, the starting material is obtained bya. providing a blend comprising a nickel-manganese hydroxide, sodium hydroxide, a source of zinc, preferably ZnO, and a source of Ti, preferably TiO2;b. mixing the blend, preferably under a dry atmosphere, preferably having a dew point of less than -20°C, more preferably of less than -30°C;c. calcining the mixed blend, preferably under a dry atmosphere, preferably having a dew point of less than -20°C, more preferably of less than -30°C, in particular in an alumina crucible or in a tray;d. optionally, sieving the calcined blend.

[0043] In an embodiment of the method of the present disclosure, the starting material comprises Na, M’, and O, wherein M’ comprises Ni in an atomic content x2, wherein 0.10 0.60 relative to M; Fe in an atomic content y2, wherein 0.00.60 relative to M’; Mn in an atomic content z2, wherein 0.100.60 relative to M; Zn in an atomic content q2, wherein 0.0 < q20.15 relative to M’; Ti in an atomic content f2, wherein 0.0 < f 20.20 relative to M’, wherein x2, y2, z2, q2, and f2 are measured by ICP-OES, x2+y2+z2+q2+f2= 1 , the Na / M’ molar ratio is between 0.8 to 1.5.

[0044] In an embodiment of the method of the present disclosure, during calcination for obtaining the starting material, the mixed blend may be held at a temperature in the range of 700°C to 1200°C for a duration of 6h to 24h.

[0045] The present disclosure further concerns a sodium battery comprising a cathode active material according to the present disclosure in any embodiment or combination of embodiments.

[0046] The present disclosure further concerns the use of a battery comprising a cathode active material according to the present disclosure in any embodiment or combination of embodiments 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 plugin 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.

[0047] Examples

[0048] Comparative Example 1 (CEX1) - To synthesize CEX1, 680.8 g of (Nio.45Mno.55)(OH)2 ( D50 = 4 pm), 320.88 g of NaOH (Sigma-Aldrich, pre-sieved using a 53pm mesh), 35.64 g of ZnO , 70.12 g of TiO2 precursors were weighed, and blended together in an intensive mixer for 2 min at 4000 rpm in a dry room under an atmosphere having a dew point of -34°C .

[0049] The resulting blended powder was transferred into an alumina crucible and calcined under dry air during a single step calcination process, holding at 950°C for for 12h.

[0050] The calcined powder was transferred immediately after cooling to a dry room where it was sieved using a 53pm mesh, then stored in a sealed aluminum bag before being subjected to further analysis. Figure 2 shows an SEM image of CEX1 . CEX1 had a composition of Nao.85[Nio.38Mno.48Zno.o4Tio.io]02.

[0051] Example 1 (Ex1) had a composition of Nao.85[Nio.378iMno.4776Zno.o398Tio.o995Bo.oo497 ]O2. CEX1 as starting material and boric acid powders were blended together in an intensive mixer for 2 min at 4000 rpm in a dry room under an atmosphere having a dew point of -34°C. The targeted amount of H3BO3 in the blend was set at 500 ppm. The mixed blend was transferred into an alumina crucible and calcined in a furnace under oxygen during a single step calcination process with a ramp of 5°C / min until the annealing temperature of 250°C, which was held for 6h. cooled down at rate of 1°C / min and unloaded at 80°C. The resulting powder was transferred immediately to a dry room where it was sieved using a 53pm mesh, then stored in a sealed aluminum bag before being subjected to further analysis. Figure 1 shows an SEM picture of EX1 .

[0052] Example 2 (Ex2), having a composition of Nao.85tNio.3762Mno.4752Zno.o396Tio.o99 BO.OO99]02, was prepared in the same way as Ex1 except that the targeted amount of H3BO3 in the blend was set at 1000 ppm.

[0053] Example 3 (Ex3), having a composition of Nao.8s[ Nio.3744Mno.4729Zno.o394Tio.o985 Bo.oi47]02,was prepared in the same way as Ex1 except that the targeted amount of H3BO3 in the blend was set at 1500 ppm.

[0054] Example 4 (Ex4) was prepared in the same way as Ex1 except that the annealing temperature was 350°C.

[0055] Example 5 (Ex5) was prepared in the same way as Ex2 except that the annealing temperature was 350°C.

[0056] Example 6 (Ex6) was prepared in the same way as Ex3 except that the annealing temperature was 350°C.

[0057] Example 7 (Ex7) was prepared in the same way as Ex1 except that the annealing temperature was 450°C.

[0058] Example 8 (Ex8) was prepared in the same way as Ex2 except that the annealing temperature was 450°C.

[0059] Example 9 (Ex9) was prepared in the same way as Ex3 except that the annealing temperature was 450°C.

[0060] Comparative Example 2 (CEX2). CEX1 as starting material was transferred into an alumina crucible and calcined in a furnace under oxygen during a single step calcination process with a ramp of 5°C / min until the annealing temperature of 250°C, which was held for 6h. cooled down at rate of 1°C / min and unloaded at 80°C. The resulting powder was transferred immediately to a dry room where it was sieved using a 53pm mesh, then stored in a sealed aluminum bag before being subjected to further analysis.

[0061] Comparative Example 3 (CEX3) was prepared in the same way as CEx2 except that the annealing temperature was 350°C.

[0062] Comparative Example 4 (CEX4) was prepared in the same way as CEx2 except that the annealing temperature was 450°C.

[0063] Powder X-ray diffraction (PXRD) - To identify the crystalline phases of the prepared materials, powder XRD patterns were collected in the 29 range of 10-130° using Co Ka X-rays (1.79 A at 45 kV and 40 mA) on an D8 X-ray diffractometer (Broker) with acquisition time 11 min. The samples were tested in a sample holder in a dry room (-34°C DP), to prevent exposure to moisture. Rietveld refinement was performed with the following phases: 03-type structure with space group R3m, undersodiated phase P2 (P 63 / m m c) and metal oxide (Fm-3m), which corresponds to Nio.8Zno.2O phase due to lattice parameter a=4.2 A. For the sample after moistures exposure the following phases were used for the refinement: 03 (R-3m), P3 (R3m) and metal oxide (Fm-3m).

[0064] Scanning Electron Microscopy (SEM) - The morphology of coated positive electrode active materials was analyzed by a Scanning Electron Microscopy (SEM) technique.

[0065] The measurement was performed using a Jeol JSM-F100 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. SEM analysis confirmed that all examples and comparative examples comprised secondary particles comprising at least 20 primary particles.

[0066] Particle size distribution (PSD) - Data about the particle size distribution (PSD) such as particle size at set percentile (such as D10, D50, D90) and span are preferably obtained by a laser PSD measurement method, i.e. D10 describes an equivalent diameter value where ten percent of the sample has a smaller particle size and ninety percent of the sample has a larger particle size. Moreover then span is defined as: Span = (D90 -D10) / D50. Here, the PSD was measured using a Malvern Mastersizer 3000 with Aero S powder dispersion accessory. Samples are first loaded into a sample feed tray on top of a hopper in preparation for measurement. In order to improve the dispersion of the powder, sufficient pressure control is applied, as well as suited sample feed rate.

[0067] Inductively coupled plasma optical emission spectroscopy (ICP-OES) - The compositions of all examples and comparative examples was measured by the inductively coupled plasma (ICP) method using an Agilent 720 ICP-OES. 1 gram of powder sample is dissolved into 50 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 was covered by a watch glass and heated on a hot plate at 380 °C until the powder is completely dissolved. After being cooled to room temperature, the solution from the Erlenmeyer flask was poured into a first 250 mL volumetric flask. Afterwards, the first volumetric flask was filled with deionized water up to the 250 mL mark, followed by a complete homogenization process (1stdilution). An appropriate amount of the solution from the first volumetric flask was taken out by a pipette and transferred into a second 250 mL volumetric flask for the 2nddilution, where the second volumetric flask was filled with an internal standard element and 10 % hydrochloric acid up to the 250 mL mark and then homogenized. Finally, this solution was used for ICP-OES measurement.

[0068] X-ray Photoelectron Spectroscopy (XPS) - In the present invention, X-ray photoelectron spectroscopy (XPS) is used to analyze the surface of positive electrode active material powder particles. 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 positive electrode active material powder particles, XPS measurement is carried out using a Thermo K-a+ spectrometer. Monochromatic Al Ka radiation (hu=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. C1s peak having a maximum intensity (or centered) at a binding energyof 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. Curve fitting is done with CasaXPS Version 2.3.19PR1.0 using a Shirley-type background treatment and Scofield sensitivity factors. The fitting parameters are according to Table 1. Line shape GL(30) is the Gaussian / Lorentzian product formula with 70% Gaussian line and 30% Lorentzian line. LA(a, [3, m) is an asymmetric line-shape where a and p define tail spreading of the peak and m define the width.

[0069] Table 1 XPS fitting parameter for B1s.

[0070] Base content measurement - the base content is a material surface property that can be quantitatively measured by the analysis of reaction products between the surface and water. A surface reaction occurs when powder is immersed into water. During the reaction, the pH of the water increases (as basic compounds dissolve) and the base is quantified by a pH titration. The result of the titration is the “soluble base content”. 25 ml of ethylene glycol (Merck) are weighed into a centrifugal tube of 50ml. Subsequently, 6.25 g of Na-cathode powder are added, and the mixture is stirred for 30 min in Turbula Mixer at 50RPM. The resulting slurry is then separated in centrifuge (Rotanta 460) for 5 minutes at 4000RPM. 20 g of the clear EG is added to 180 g of deionized water to form a 10wt% EG / H2O solution. An automatic titrator (Methrohm) is employed to identify the two equivalence points using 0.1M HCI (Titripac Merck). The first equivalence point corresponds to the neutralization of NaOH and Na2CO3, while the second equivalence point corresponds to NaHCO3 (referred to as CO3hereafter).

[0071] Coin cell assembly - The coin cell is assembled inside of an argon-filled glovebox to prevent contamination. 2 separators (Glass Fiber, Whatman) are placed between the positive electrode and a piece of sodium foil, which serves as the negative electrode. An electrolyte solution comprising 0.6 M NaPF6 in polyethylene carbonate (PC) with 2% FEC additive is dropped between the separator and the electrodes. The coin cell is then sealed to prevent electrolyte leakage, completing the assembly process.

[0072] Cycling protocol - 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 11 mg / cm2. The discharge capacity for the first cycle (DQ1) is measured within the voltage range of [4.2 V - 2.2 V] at a rate of 0.1 C (expressed in mAh / g) at a temperature of 25°C.

[0073] Table 2. Summary of the coating process for the preparation of positive electrode active material.

[0074] Table 3. Composition of examples and comparative example from ICP and XPS and their corresponding electrochemical properties from coin-cell test of the pristine examples

[0075] Particle size distribution data and 03 weight percentages after Oh, 3h, and 72h of storage are shown in Table 4.

[0076] Table 4

[0077] As can be seen in Table 1 , examples 1 to 9 show improved amounts of 03 weight percentage after prolonged exposure to an humid atmosphere, in particular of up to 72h, and thus provide better stability than the respective CE1 to CE4 having undergone the same heating steps.

Claims

Claims

1. A cathode active material for sodium batteries, wherein the cathode active material comprises Na, M, and 0, wherein M comprises:a. Ni in an atomic content x, wherein 0.10 < x < 0.60 relative to M,b. Fe in an atomic content y, wherein 0.0 < y < 0.60 relative to M,c. Mn in an atomic content z, wherein 0.10 < z < 0.60 relative to M, d. Zn in an atomic content q, wherein 0.0 < q < 0.15 relative to M,e. Ti in an atomic content f, wherein 0.0 < f < 0.20 relative to M,f. B in an atomic content a, wherein 0.0001 < a < 0.05 relative to M, wherein x, y, z, q, f and a are measured by ICP-OES, x+y+z+q+f+a = 1 , and wherein the Na / M molar ratio ranges from 0.8 to 1.5.

2. A cathode active material according to claim 1 , having a particle size distribution value D50 lower than 10 pm.

3. A cathode active material according to claim 1 or 2, wherein 0.001 < a < 0.03 relative to M, preferably 0.005 < a < 0.02 relative to M, more preferably 0.007 < a < 0.015 relative to M.

4. A cathode active material according to claim 1 , wherein the Na, M, and 0 content of the cathode active material, is represented by the formula (I) NawNixiFeyiMnziZnqiTifiBaiO2, wherein 0.80 < w < 1.50; 0.10 < x1 < 0.60; 0.0 < y1 < 0.60; 0.10 < z1 < 0.60; 0.0 < q1 < 0.15; 0.0 < f1 < 0.20; 0.0001 < a1 < 0.05; wherein x1 , y1 , z1 , q1 , f1 and a1 are measured by ICP-OES, and x1+y1+z1+q1+f1+a1 is 1.

5. A cathode active material according to claim 4, wherein 0.20 < x1 < 0.50, y1 is 0, 0.30 < z1 < 0.60, 0.001 < q1 < 0.10, 0.001 < f1 < 0.20, and wherein 0.001 < a1 < 0.03.

6. A cathode active material according to any of the claims 1 to 5, wherein the BXPS / BICP ratio is higher than 10, wherein BXPS is the content of boron relative to the total content of Ni, Fe, Mn, Zn, Ti and B, as measured by X-ray photo electron spectroscopy, and BICP is the B content relative to the total content of Ni, Fe, Mn, Zn, Ti and B, as measured by ICP-OES.

7. A method for manufacturing a cathode active material according to any of the claims 1 to 6, wherein the method comprises the following steps:a. providing a starting material comprising Na, M’, and 0, in particular wherein M’ comprises:i. Ni in an atomic content x2, wherein 0.100.60 relative to M’,ii. Fe in an atomic content y2, wherein 0.00.60 relative to M’, iii. Mn in an atomic content z2, wherein 0.100.60 relative to M,iv. Zn in an atomic content q2, wherein 0.0 < q20.15 relative to M’, v. Ti in an atomic content f2, wherein 0.0 < f20.20 relative to M’, wherein x2, y2, z2, q2, and f2 are measured by ICP-OES, x2+y2+z2+q2+f2= 1 , the Na / M’ molar ratio is between 0.8 to 1.5; b. blending the starting material with a boron source, in particular boric acid, to obtain a first mixture;c. heating the first mixture up to a temperature Tmax of up to 600°C;d. cooling down the heated first mixture and to obtain the cathode active material ;wherein the Boron source to starting material ratio added so as to obtain a B content in the cathode active material ranging from 500 ppm to 1500 ppm.

8. A method according to claim 7, wherein the sodium metal oxide is according to formula (II) Nar2Nix2Fey2Mnz2ZnqiTifiO2, wherein 0.10 < x2 < 0.60; 0.0 < y2 < 0.60; 0.10 < z2 < 0.60; 0.0 < q2 < 0.15; 0.0 < f2 < 0.20; wherein x2, y2, z2, q2 and f2 are measured by ICP-OES, and x2+y2+z2+q2+f2 is 1.

9. A method according to claim 7 or 8, wherein the sodium metal oxide has a particle size distribution value D50 ranging of not more than 20pm, preferably of not more than 15pm, more preferably of not more than 10pm.

10. A method according to any of the claims 7 to 9, wherein 150°C < Tmax — 500°C.

11. A method according to any of the claims 7 to 10, wherein the B source is boric acid H3BO3.

12. A method according to any of the claims 7 to 11 , wherein after heating the first mixture up to a temperature Tmax, the first mixture is maintained at Tmax for a duration of at least 2h and of at most 10h.

13. A method according to any of the claims 7 to 12, wherein mixing the metal-based precursor oxide with the B source is performed under an atmosphere having a dew point of less than -20°C, preferably less than -30°C.

14. A battery comprising a cathode active material according to any of the claims 1 to 6.

15. Use of a 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, a two-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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