Positive electrode composite material

Abstract

The present invention relates to a positive electrode composite material comprising particles of a positive electrode material comprising Li, M', and O, wherein M' comprises Ni, Mn, Co, N', D, wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof, and wherein D is at least one element other than Li, Ni, Mn, Co, N' and O; further comprising a sulfide solid electrolyte coating.

Description

[0001] POSITIVE ELECTRODE COMPOSITE MATERIAL

[0002] TECHNICAL FIELD

[0003] The present invention relates to a positive electrode composite material comprising a positive electrode active material and a sulfide solid electrolyte. The present invention further relates to methods for manufacturing said composite materials and a battery comprising said composite materials.

[0004] BACKGROUND

[0005] The three primary functional components of a lithium-ion battery are the anode, the cathode, and the electrolyte. While many variations exist, the anode of a conventional lithium-ion cell is typically made from carbon or metallic lithium, the cathode is typically made from transition metal oxides (in particular oxides of cobalt, nickel and / or manganese), and the electrolyte is typically a non-aqueous solvent containing a lithium salt. For example, mixtures of organic carbonates with lithium hexafluorophosphate are well known liquid electrolytes for lithium-ion batteries.

[0006] A significant disadvantage of liquid electrolytes is that the compositions, in particular the solvents are inflammable, which poses a large safety risk during normal operation and in particular in case of an incident. Another disadvantage inherent to the liquid nature of the electrolyte are associated with risks of leakage and with increased risk of environmental pollution in case of a spill or leakage.

[0007] Recently, efforts have been made to develop solid electrolytes which allow the provision of a solid-state lithium-ion battery. Such solid-state batteries have significantly reduced EHS (environmental, health and safety) hazards. The solid-state electrolyte can act as an electrolyte as well as a separator, physically separating the anode and cathode material in order to prevent short-circuiting.

[0008] While in a liquid electrolyte based Li-ion battery, thanks to its fluidity, the liquid electrolyte impregnates the positive electrode and gets into very intimate contact with the positive electrode active material, allowing low electrode polarization and high utilization rate of active material, in a solid state electrolyte based battery, without liquid fluidity, it is challenging to obtain similar intimate contact between the solid electrolyte material and the positive electrode active material.

[0009] On top, the repeated electrode expansion and contraction during cycling further deteriorates the mechanical particle-to-particle contact between the solid electrolyte and positive electrode active material particles.

[0010] As a consequence, high polarization and low utilization rate of active materials are conventional drawbacks in solid-state lithium batteries.

[0011] An important key to realize solid state lithium batteries with competitive performances thus relies on the construction of a stable and intimate interface between the positive electrode active material and the solid electrolyte material. A way to achieve this is to prepare a positive electrode layer that includes an intimate mix of positive electrode active material together with the solid electrolyte material. As a result, the surface area of interface between solid electrolyte and positive electrode active material is increased resulting in a better and more stable contact between said solid electrolyte and the positive electrode active material particles.

[0012] However, it is known that the positive electrode active material reacts with the solid electrolyte creating a resistance against the movement of Li ions across the interface. It has been suggested in the prior art that a way to mitigate this problem is by treating the positive electrode active material particles surface with a buffer layer, such as H3BO3.

[0013] US2021 / 0305562 Al discloses a positive electrode composite material comprising a positive electrode active material, having a Ni / Co / Mn composition ratio of 0.33 / 0.33 / 0.33, with a niobium coating a sulfide solid electrolyte coating including a conductive auxiliary agent.

[0014] KR.20230095635 Al discloses a positive electrode composite material comprising a positive electrode active material, with a zirconium comprising first coating below a sulfide solid electrolyte comprising second coating. It is an object of the present invention to provide an improved positive electrode composite material, in particular a positive electrode composite material having an improved electrochemical performance.

[0015] SUMMARY OF THE INVENTION

[0016] The present inventors have found that one or more objects of the invention may be achieved by the provision of a positive electrode composite material comprising a lithium nickel manganese and / or cobalt oxide comprising metals selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof coated with a sulfide solid electrolyte. It was surprisingly found that such a positive electrode composite material may enhance the electrochemical performance of batteries.

[0017] In an aspect, the present invention concerns a positive electrode composite material comprising:

[0018] • Particles of a positive electrode active material comprising Li, M', and 0, wherein M' comprises: o Ni in a content x, wherein 45.0 at% < x < 95.0 at%, relative to M'; o Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M'; o Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 2.0 at%, relative to M', wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof; o D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, N' and O; and o wherein x + y + z + w+ q is 100.0 at% and x, y, z, w and q are measured by ICP-OES;

[0019] • and a sulfide solid electrolyte;

[0020] • wherein the sulfide solid electrolyte covers at least a part of the surface of the particles forming a coating.

[0021] In another aspect of the invention there is provided a method for preparing a positive electrode composite material, in particular a positive electrode composite material according to any embodiment defined herein, comprising the steps of: a) providing at least the following precursors: • a positive electrode active material comprising Li, M', and 0, wherein M' comprises: o Ni in a content x, wherein 45.0 at% < x < 95.0 at%, relative to M'; o Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M'; o Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 2.0 at%, relative to M', wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof; o D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, N' and O; and o wherein x + y + z + w+ q is 100.0 at% and x, y, z, w and q are measured by ICP-OES;

[0022] • a sulfide solid electrolyte;

[0023] • optionally a carbon-based conductive aid; b) mixing of the precursors to afford the positive electrode composite material of the present invention.

[0024] In another aspect of the invention, there is provided a battery comprising a positive electrode comprising the positive electrode composite material as described herein, a further solid electrolyte and an anode.

[0025] In another aspect of the invention, there is provided the use of a battery comprising the positive electrode composite material of the invention in motor vehicles, bicycles operated by electric motor, robots, aircraft (for example unmanned aerial vehicles including drones), ships, satellites or stationary energy stores.

[0026] BRIEF DESCRIPTION OF THE FIGURES

[0027] Figure 1 : a) SEM of EX3 (Li5.4PS4.4Cli.oBro.6), b) SEM of EX5 (Li3.5PS4Br0.25I0.25).

[0028] Figure 2: a) XPS of EX1-4 and CEX1, b) XPS of EX5 and CEX2.

[0029] Figure 3: Charge-discharge capacity of a) EX3 and CEX1, b) EX1-4 and c) EX5 and CEX2.

[0030] Figure 4: Electrochemical impedance spectra of a) EX3 and CEX1, b) EX1-4 and c) EX5 and CEX2. Figure 5: Schematic illustration of the coating thickness calculation from a SEM picture

[0031] DETAILED DESCRIPTION

[0032] In the following detailed description, 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 embodiments. To the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description.

[0033] The term "comprising", as used herein and in the claims, should not be interpreted as being restricted to the features 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 for example certain technical effects, the 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".

[0034] The term "solid-state battery" as used herein refers to a cell or a battery that includes only solid or substantially solid-state components such as positive electrode composite solid active material (e.g. anode, cathode and solid electrolyte).

[0035] The term "positive electrode composite material" and "cathode composite material" are synonyms and can be used interchangeably throughout this document.

[0036] The term "positive electrode active material" and "cathode active material (CAM)" are synonyms and can be used interchangeably throughout this document.

[0037] The term "argyrodite-type crystal structure" as used herein refers to a crystal structure having a crystal structure or system similar to naturally existing AgsGeSe and U7PS6 (Argyrodite). The argyrodite-type crystal structure may be of orthorhombic symmetry and described in the F-43m space group. Alternately, the argyrodite-type crystal structure may be empirically determined for example, by X- ray diffraction by observing diffraction peaks around at 20=15.5±1°, 18±1°, 26±1°, 30.5±l° and 32 ±1° using CuKa-ray wavelength.

[0038] The term "thio-LISICON Region Il-type crystal structure" expresses any one of a Li4-xGel- xPxS4thio-LISICON Region Il-type crystal structure and a crystal structure similar to the Li4-xGel-xPxS4 thio-LISICON Region Il-type crystal structure. In addition, though the sulfide solid electrolyte (SSE) of the present embodiment may be one having the aforementioned thio-LISICON Region Il-type crystal structure or may be one having the thio-LISICON Region Il-type crystal structure as a main crystal, it is preferably one having the thio-LISICON Region II- type crystal structure as a main crystal. By X-ray diffraction by observing diffraction peaks, the Li4-xGel-xPxS4 thio-LISICON Region Il-type crystal structure gives diffraction peaks, for example, at around 20=20.1°, 23.9°, and 29.5°; and the crystal structure similar to the Li4-xGel-xPxS4 thio-LISICON Region Il-type crystal structure gives diffraction peaks, for example, at around 2. theta. =20.2° and 23.6° The position of these peaks may vary within a range of ±0.5°.

[0039] X-Ray diffraction (XRD) as referred to herein, refers to XRD experiments performed using Bruker D8 diffractometers equipped with Cu (Kal-Ka2) radiation in a 0-0 configuration. Preferably, an air-tight sample holder with a dome type is used. Preferably, the patterns were collected between 20 = 100- 550with a step size of 0.02 °.

[0040] "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.

[0041] Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES)

[0042] The composition of positive electrode active material powder is determined by the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method, in particular using an Agilent ICP 720-ES (Agilent Technologies). 2 gram of a powder sample of each example is dissolved into 10 mL high purity hydrochloric acid (at least 37 wt% HCI) in an Erlenmeyer flask. The flask is covered by a watch glass and heated on a hot plate at 380°C until complete dissolution of the sample. After being cooled to room temperature, the solution and the rinsing water of Erlenmeyer flask are transferred to a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with DI water up to the 250 mL mark, followed by complete homogenization.

[0043] The composition of positive electrode composite material powder is determined by the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method, in particular using an Agilent 5110. About 0.2 gram of a powder sample was first weighed into a microwave vessel in an inert glovebox before ImL DI water and 9mL concentrated nitric acid was added. The sample was placed in a microwave digester at 180 °C for 30 minutes before being diluted again by a factor of 10 for impurity analysis and 100 for matrix analysis. An internal standard is added prior to measurement via ICP-OES.

[0044] BET

[0045] To determine the specific surface area (SSA) of the positive electrode composite material powder the gas adsorption was conducted using the Brunauer-Emmett- Teller (BET) theory. Approx. 1 g of sample was weighed into a suitable sized gas adsorption sample vial in an inert atmosphere. The vial was sealed with an appropriate cap and transferred to a Micromeritics VacPrep 061 for pre-treatment. The sample was then heated to 160°C under vacuum for 60 minutes, and then nitrogen for 30 minutes. BET SSA is then measured using a Micromeritics TriStar 3020.

[0046] SEM

[0047] The cross-sectional particle samples were analyzed by Scanning Electron Microscope (SEM), in particular using a JEOL F100 Schottky Field Emission Scanning Electron Microscope (FEG-SEM). The samples were prepared in an inert environment / atmosphere. A straight section of a pelletized sample was placed on the edges between two pieces of conductive metal tape. The exposed edge was ion milled with a JEOL IB-19520CCP broad ion beam miller to prepare the cross-sectional area for analyses. Images of prepared samples were taken at magnifications ranging from lOOOx - 25000x, at accelerating voltages of 3 kV. XPS

[0048] The positive electrode composite material powder was measured using a X-ray photoelectron spectroscopy (XPS) using a THERMOFISHER. K-alpha system with a monochromatic Al Ko x-ray source. A small amount of powder sample was deposited onto a copper tape in a special inert transfer vessel. The vessel was transferred into the main chamber and a vacuum was applied to ensure the sample is not in contact with any atmospheric moisture. Whole-region survey (0 - 1350 eV) and high- resolution scans of elements of interest were collected for analysis.

[0049] In an aspect of the present invention is provided a positive electrode composite material comprising:

[0050] • particles of a positive electrode active material comprising Li, M', and O, wherein M' comprises: o Ni in a content x, wherein 45.0 at% < x < 95.0 at%, relative to M'; o Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M'; o Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 2.0 at%, relative to M', wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof; o D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, N' and O; and o wherein x + y + z + W+ q is 100.0 at% and x, y, z, w and q are measured by ICP-OES;

[0051] • and a sulfide solid electrolyte;

[0052] • wherein the sulfide solid electrolyte covers at least a part of the surface of the particles forming a surface coating.

[0053] In preferred embodiments the positive electrode active material is according to the invention comprising Li, M', and O, wherein M' comprises: o Ni in a content x, wherein 55.0 at% < x < 95.0 at%, relative to M'; o Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M'; o Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 1.5 at%, relative to M', wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof; o D in a content q, wherein 0.0 at% < q < 2.0 at%, r relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, N' and O; o wherein x + y + z + w + q is 100.0 at%; preferably wherein M' comprises: o Ni in a content x, wherein 60.0 at% < x < 90.0 at%, relative to M'; o Mn in a content y, wherein 0.0 at% < y < 30.0 at%, relative to M'; o Co in a content z, wherein 0.0 at% < z < 30.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 1.5 at%, relative to M'; o D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M'; more preferably wherein M' comprises: o Ni in a content x, wherein 70.0 at% < x < 85.0 at%, relative to M'; o Mn in a content y, wherein 5.0 at% < y < 20.0 at%, relative to M'; o Co in a content z, wherein 5.0 at% < z < 20.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 1.5 at%, relative to M'; o D in a content q, wherein 0.0 at% < q < 1.0 at%, relative to M'; even more preferably wherein M' comprises: o Ni in a content x, wherein 80.0 at% < x < 85.0 at%, relative to M'; o Mn in a content y, wherein 5.0 at% < y < 9.0 at%, relative to M'; o Co in a content z, wherein 5.0 at% < z < 9.0 at%, relative to M'; o N' in a content w, wherein 0.02 at% < w < 1.0 at%, relative to M', where N' is B; o D in a content q, wherein 0.0 at% < q < 0.5 at%, relative to M'.

[0054] In preferred embodiments the positive electrode active material is according to the invention, wherein 0.1 at% < w < 1.4 at%, preferably 0.25 at% < w < 1.3 at%, more preferably 0.5 at% < w < 1.0 at%. As appreciated by the skilled person the amount of Ni, Mn, Co, M' and D in the positive electrode active material is advantageously measured by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Worded differently, x, y, z, w and q are determined by ICP-OES.

[0055] A preferred embodiment is the positive electrode active material of the invention having a Li / M' molar ratio, in particular a Li / (Ni + Mn+Co) molar ratio (mol / mol), such that Li / M' > 0.90, > 0.92, or > 0.95 and / or such that Li / M' < 1.10, < 1.08, or < 1.05. In particular, Li / M' may be in the range of 0.90 to 1.10, in the range of 0.92 to 1.08, or in the range of 0.95 to 1.05.

[0056] In an embodiment M' consists of Ni, Mn, Co, N' and D. In particular, M' consists of Ni, Mn, Co, N' and D in any of the ratios as disclosed herein.

[0057] In an embodiment of the present invention, N' is one element selected from the group consisting B, Zr, Nb, Ti, and W; more preferably N' is one element selected from the group consisting B, Zr, Nb and Ti; even more preferably N' is one element selected from the group consisting B, Zr and Nb. Most particularly N' is B.

[0058] The positive electrode active material of the invention may comprise impurities or be doped or contain metals on the surface resulting in an overall positive electrode active material comprising one or more elements other than Li, Ni, Mn, Co, N' and O, which is reflected in the parameter "D" used herein with q > 0.0 mol%. In exemplary embodiments, the positive electrode active material comprises D, wherein D is at least one element selected from the group consisting of Al, Ba, Ca, Ce, Cr, Fe, La, Mg, Mo, Sr, Ti, V, W, Y, and Zn; particularly from the group consisting of Al, Ti, Cr, Y, and W; more particularly from the group consisting of Al, Ti, and W.

[0059] In certain advantageous embodiments of the present invention q = 0.0 mol%, relative to M'. In particular, such a composition may show no peak corresponding to D in an ICP-OES analysis.

[0060] In an embodiment of the present invention, the positive electrode composite material is devoid of any additional positive electrode active material. In preferred embodiments of the positive electrode active material according to the invention, the particles of positive electrode active material comprise a surface layer, wherein the surface layer comprises N'.

[0061] In preferred embodiments of the present invention, the positive electrode active material comprises single particles and / or secondary particles, wherein single particles consist each of a single primary particle and wherein each of the secondary particles consist of at least two primary particles and at most twenty primary particles, in particular as observed in a SEM image. At least 30% or at least 50% of the particles of positive electrode active material, in particular as observed in a SEM image, may be such single particles and / or secondary particles. The number of primary particles constituting single particles and / or secondary particles may be determined in a field of view of at least 45 pm x at least 60 pm ( / .e. of at least 2700 pm2), preferably of: at least 100 pm x 100 pm (i.e. of at least 10000 pm2). 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. In the context of the present invention primary particles are 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.

[0062] In preferred embodiments the positive electrode active material is according to the invention, wherein the surface layer has a maximum thickness of at least 5 nm, at least 10 nm, at least 20 nm, or at least 25 nm and / or of less than 60 nm, less than 50 nm, less than 40 nm, or less than 35 nm. In preferred embodiments the positive electrode active material is according to the invention, wherein the surface layer has a maximum thickness of from 5 to 60 nm, from 10 to 50 nm, from 20 to 40 nm, or from 25 to 35 nm, advantageously as determined by TEM-EDX.

[0063] In preferred embodiments the positive electrode active material is according to the invention, wherein the media particle size D50 of the positive electrode active material is between 1 and 15 pm, preferably between 2 and 10 pm, more preferably between 3 and 5 pm. In the positive electrode active material, the particles surface layer may be present on only a part of the particle surface. The particles of positive electrode active material may comprise the surface layer in at least 70 % of their surface of at least 80 %, at least 90%, or at least 95%. Preferably the particles of positive electrode active material may comprise the surface layer in the whole surface.

[0064] In an embodiment, the sulfur solid electrolyte coating has a thickness between 50 and 300 nm, preferably between 65 and 275 nm, more preferably between 80 and 250 nm.

[0065] In an embodiment, the sulfur solid electrolyte coating covers at least 70 % of the surface of the particles, preferably at least 80 %, more preferably at least 90 %, even more preferably at least 95 %, even more preferably at least 98 %, most preferably the whole surface of the particles.

[0066] In an embodiment of the positive electrode composite material of the present invention, the sulfide solid electrolyte comprises Li, P and S.

[0067] In preferred embodiments the sulfide solid electrolyte comprises at least one halogen element, preferably selected from F, Cl, Br and I, more preferably selected from Cl, Br and I. Indeed, throughout this patent application X may represent a single halogen as well as a mixture of two or more halogens.

[0068] In advantageous embodiments of the positive electrode composite material, the sulfide solid electrolyte is according to formula (I)

[0069] Li6-yPS5-yXl+y (I) wherein -0.5 < y < 1 and X is at least one of F, Cl, Br or I, X may thus be one of these elements or a combination of two, three or four of these elements

[0070] In preferred embodiments the sulfide solid electrolyte is according to formula (I), wherein -0.2 < y < 0.9, preferably 0 < y < 0.8, more preferably 0.2 < y < 0.7, even more preferably 0.5 < y < 0.7. In preferred embodiments the sulfide solid electrolyte is according to formula (I), wherein X is at least one of Cl, I and Br, more preferably at least one of Br and Cl. Advantageously X is a combination of Br and Cl.

[0071] In an alternative embodiment the sulfide solid electrolyte is according to formula (I), wherein at least 50 mol% of X represents Cl, preferably at least 80 mol% of X represents Cl, most preferably X represents Cl.

[0072] In an alternative embodiment the sulfide solid electrolyte is according to formula (I), wherein at least 50 mol% of X represents Br, preferably at least 80 mol% of X represents Br, most preferably X represents Br.

[0073] In advantageous embodiments of the positive electrode composite material is according to the invention, the sulfide solid electrolyte is according to formula (II)

[0074] U4-zPS4Xz (II) wherein 0 < z < 1.0 and X is at least one of F, Cl, Br or I, X may thus be one of these elements or a combination of two, three or four of these elements

[0075] In preferred embodiments the sulfide solid electrolyte is according to formula (II), wherein 0.1 < z < 1.0, preferably 0.2 < z < 0.9, more preferably 0.3 < z < 0.8, even more preferably 0.4 < z < 0.7.

[0076] In preferred embodiments the sulfide solid electrolyte is according to formula (II), wherein X at least one of Cl, Br and I, more preferably X at least one of Br and I. Advantageously X is a combination of Br and I.

[0077] In an alternative embodiment the sulfide solid electrolyte is according to formula (II), wherein at least 50 mol% of X represents Br, preferably at least 80 mol% of X represents Br, most preferably X represents Br.

[0078] In an alternative embodiment the sulfide solid electrolyte is according to formula (II), wherein at least 50 mol% of X represents I, preferably at least 80 mol% of X represents I, most preferably X represents I. In certain preferred embodiments the positive electrode composite material is according to the invention, wherein the sulfide solid electrolyte has an argyroditetype crystal structure or a thio-LISICON Region Il-type crystal structure.

[0079] In certain preferred embodiments the positive electrode composite material is according to the invention, wherein the sulfide solid electrolyte has a purity of at least 90%, preferably at least 95%, more preferably at least 99%, in particular as determined by XRD.

[0080] In an embodiment of the positive electrode composite material of present invention, the weight ratio (w / w) of the positive electrode active material to the sulfide solid electrolyte is less than 99: 1 preferably less than 90: 10, more preferably less than 85: 15, most preferably less than 80:20, even most preferably less than 70:30.

[0081] In an embodiment of the positive electrode composite material of present invention, the weight ratio (w / w) of the positive electrode active material to the sulfide solid electrolyte is at least 50:50, preferably is at least 60:40, more preferably at least 65:35, most preferably at least 70:30. In certain preferred embodiments the weight ratio (w / w) of the positive electrode active material to the sulfide solid electrolyte is between 85: 10 and 99: 1. In certain preferred embodiments the weight ratio (w / w) of the positive electrode active material to the sulfide solid electrolyte is between 90: 10 and 99: 1.

[0082] In an embodiment of the positive electrode composite material of present invention, the specific surface area of the composite material is at least 0.3 m2 / g, preferably at least 0.4 m2 / g, more preferably at least 0.5 m2 / g.

[0083] In an embodiment of the positive electrode composite material of present invention, the specific surface area of the composite material is of less than 1.5 m2 / g, preferably less than 1.25 m2 / g, even more preferably less than 1.0 m2 / g.

[0084] In an embodiment of the positive electrode composite material of present invention, the specific surface area of the composite material is between 0.3 and 1.5 m2 / g, preferably between 0.4 and 1.25 m2 / g, more preferably between 0.5 and 1.0 m2 / g. Here within the specific surface area may in particular be determined by BET. In an optional embodiment of the present invention, the positive electrode composite material further comprises a conductivity aid, in particular a carbon-based conductivity aid. The carbon-based conductivity aid may be any carbon-rich material, such as any material comprising at least 95 wt% carbon, preferably any material comprising at least 99 wt% carbon. Examples of suitable materials are graphite, carbon black, carbon fibers, carbon nanotubes, graphene and combinations thereof. A highly preferred carbon-based conductivity aid which the inventors have found to exhibit improved electrochemical performance compared to other carbon-based conductivity aids when employed in the solid composite cathode compositions of the present invention is carbon black. Carbon black is known to the skilled person and includes variants such as acetylene black or super C65.

[0085] In an optional embodiment of the present invention, the positive electrode composite material comprises the carbon-based conductivity aid in an amount of at least 0.5 wt%, preferably at least 1 wt%, more preferably at least 3 wt%. Here within, the weight percentage (wt%) of the carbon-based conductivity aid is the weight percentage by total weight of the positive electrode composite material.

[0086] In an embodiment of the present invention, the positive electrode composite material comprises the carbon-based conductivity aid is present in an amount of less than 12 wt%, preferably less than 9 wt%, more preferably less than 7 wt%.

[0087] In an embodiment of the present invention, the positive electrode composite material comprises the carbon-based conductivity aid as described herein is present in the solid composite cathode composition of the present invention in an amount between 0.5 and 12 wt%, preferably between 1 and 9 wt%, more preferably between 3 and 7 wt%.

[0088] In an embodiment of the present invention, the combined amount of the positive electrode active material, the sulfide solid electrolyte and optional carbon-based conductivity aid is at least 90 wt% by total weight of the positive electrode composite material, preferably at least 95 wt% (by total weight of the positive electrode composite material), more preferably at least 98 wt% (by total weight of the positive electrode composite material). In an embodiment of the present invention, the positive electrode composite material consists essentially of the positive electrode active material having the surface layer comprising N' as defined herein, the sulfide solid electrolyte as defined herein and optionally the carbon-based conductivity aid as defined herein.

[0089] When provided in a solid state battery, the positive electrode composite material according to an embodiment or combination of embodiments of the invention may enable a direct current internal resistance (DCIR.) between 10 and 45 Ohmcm2, preferably between 15 and 40 Ohmcm2, more preferably between 20 and 35 Ohmcm2and thus enhance the battery's electrochemical performance.

[0090] The present invention further provides a method for preparing a positive electrode composite material, in particular according to an embodiment or combination of embodiments described herein, comprising the following steps: a) providing at least the following precursors:

[0091] • a positive electrode active material comprising Li, M', and O, wherein M' comprises: o Ni in a content x, wherein 45.0 at% < x < 95.0 at%, relative to M'; o Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M'; o Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 2.0 at%, relative to M', wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof; o D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, N' and O; and o wherein x + y + z + W+ q is 100.0 at% and x, y, z, w and q are measured by ICP-OES;

[0092] • a sulfide solid electrolyte;

[0093] • optionally a carbon-based conductive aid; b) mixing of the precursors to afford the positive electrode composite material.

[0094] In an embodiment of the present invention, the precursor positive electrode active material comprises Li, M' and O, wherein M' comprises - Ni in a content x, wherein 55.0 at% < x < 95.0 at%, relative to M';

[0095] - Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M';

[0096] - Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M';

[0097] - N' in a content w, wherein 0.01 at% < w < 1.5 at%, relative to M'; wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof;

[0098] - D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, and O;

[0099] - wherein x + y + z + w + q is 100.0 at%; preferably wherein M' comprises:

[0100] - Ni in a content x, wherein 60.0 at% < x < 90.0 at%, relative to M';

[0101] - Mn in a content y, wherein 0.0 at% < y < 30.0 at%, relative to M';

[0102] - Co in a content z, wherein 0.0 at% < z < 30.0 at%, relative to M';

[0103] - N' in a content w, wherein 0.01 at% < w < 1.5 at%, relative to M';

[0104] - D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M'; more preferably wherein M' comprises:

[0105] - Ni in a content x, wherein 70.0 at% < x < 85.0 at%, relative to M';

[0106] - Mn in a content y, wherein 5.0 at% < y < 20.0 at%, relative to M';

[0107] - Co in a content z, wherein 5.0 at% < z < 20.0 at%, relative to M';

[0108] - N' in a content w, wherein 0.01 at% < w < 1.5 at%, relative to M';

[0109] - D in a content q, wherein 0.0 at% < q < 1.0 at%, relative to M'; even more preferably wherein M' comprises:

[0110] - Ni in a content x, wherein 80.0 at% < x < 85.0 at%, relative to M';

[0111] - Mn in a content y, wherein 5.0 at% < y < 9.0 at%, relative to M';

[0112] - Co in a content z, wherein 5.0 at% < z < 9.0 at%, relative to M';

[0113] - N' in a content w, wherein 0.02 at% < w < 1.0 at%, , relative to M', where N' is B;

[0114] - D in a content q, wherein 0.0 at% < q < 0.5 at%, , relative to M'.

[0115] Preferably, the precursor sulfide solid electrolyte is the sulfide solid electrolyte as described herein above. As is appreciated by the skilled person and in embodiments of the method of the invention all the embodiments related to the positive electrode composite material according to the first aspect of the invention apply mutatis mutandis to the method of manufacturing the positive electrode composite material according to the invention. For example, the various embodiments relating to identify the positive electrode active material, the surface layer and the sulfide solid electrolyte, (relative) amounts of the positive electrode active material and the sulfide solid electrolyte and purity level, as explained herein in the context of the positive electrode composite material, are equally applicable to the method for manufacturing a positive electrode composite material according to the invention.

[0116] In advantageous embodiments of the method of the present invention, the mixing of the precursors of step b) is performed at a mixing speed of at least 10 rpm, preferably a mixing speed of at least 50 rpm, most preferably a mixing speed of at least 100 rpm.

[0117] In advantageous embodiments of the method of the present invention the mixing of the precursors of step b) is performed at a mixing speed of at most 500 rpm, preferably a mixing speed of at most 400 rpm, most preferably a mixing speed of at most 300 rpm.

[0118] In advantageous embodiments of the method of the present invention the mixing of the precursors of step b) is performed at a mixing speed of 10 - 500 rpm, preferably a mixing speed of 50 - 400 rpm, most preferably a mixing speed of 100 - 300 rpm.

[0119] In advantageous embodiments of the method of the present invention the mixing of the precursors of step b) is performed for at least 5 minutes, preferably at least 0.5 hour, most preferably at least 1 hour.

[0120] In advantageous embodiments of the method of the present invention the mixing of the precursors of step b) is for at most 6 hours, preferably at most 3 hours, most preferably at most 90 minutes.

[0121] In advantageous embodiments of the method of the present invention the mixing of the precursors of step b) is between 5 minutes and 6 hours, preferably between 0.5 hour and 3 hours, most preferably between 60 and 90 minutes. In advantageous embodiments of the method of the present invention the mixing of the precursors mixture of step b) occurs at a temperature of at least 5 °C, preferably at least 10 °C, more preferably at least 15 °C.

[0122] In advantageous embodiments of the method of the present invention the mixing precursors mixture of step b) occurs at a temperature of less than 50 °C, preferably less than 40 °C, more preferably less than 30 °C.

[0123] In advantageous embodiments of the method of the present invention the mixing of the precursors of step b) occurs at a temperature between 5 and 50 °C, preferably a temperature between 10 and 40 °C, more preferably a temperature between 15 and 30 °C.

[0124] In certain preferred embodiments the method is according to the invention, the mixing of the precursors of step b) is performed

[0125] • with a mixing speed of 10 - 500 rpm, preferably a mixing speed of 50 - 400 rpm, most preferably a mixing speed of 100 - 300 rpm; and

[0126] • with a mixing time between 5 min and 6 hours, preferably between 0.5 hours and 3 hours, most preferably between 60 and 90 minutes.

[0127] In a further aspect the invention concerns the positive electrode composite material obtainable by the method according to the second aspect of the invention. As appreciated by the skilled person all the embodiments related to the positive electrode composite material according to the first aspect of the invention and all the embodiments related to the method of manufacturing the positive electrode composite material according to the second aspect of the invention apply mutatis mutandis to the positive electrode composite material obtainable by the method according to the second aspect of the invention. For example, the various embodiments relating to identify the positive electrode active material, the surface layer and the sulfide solid electrolyte, (relative) amounts of the positive electrode active material coated and the sulfide solid electrolyte and purity level as explained herein in the context of the positive electrode composite material, are equally applicable to the method for manufacturing a positive electrode composite material according to the invention.

[0128] A further aspect of the invention concerns a battery comprising a positive electrode, a further solid electrolyte and a negative electrode layer. The positive electrode comprises the positive electrode composite material according to the invention, as described herein.

[0129] The further solid electrolyte according to the invention is disposed between the positive electrode and the negative electrode. The solid electrolyte may be a known solid electrolyte used in solid-state lithium ion batteries, and examples thereof include a sulfide solid electrolyte, an oxide solid electrolyte, and a halide solid electrolyte, and among them, a sulfide solid electrolyte is preferable. Preferably the sulfide solid electrolyte contained in the further solid electrolyte is the sulfide solid electrolyte as described herein.

[0130] The negative electrode according to the invention contains at least a negative electrode active material. The negative electrode active material can contain a solid electrolyte, preferably the sulfide solid electrolyte as described herein. The negative electrode active material is not particularly limited, and examples thereof include a metal active material, a carbon active material, and an oxide active material.

[0131] In a preferred embodiment the battery is a solid-state battery, preferably a lithium solid-state battery.

[0132] A further aspect of the invention concerns a use of the positive electrode composite material according to the invention in a battery, preferably a solid-state-battery, most preferably a lithium solid-state-battery.

[0133] A further aspect of the present invention concerns a use of the battery according to the invention in either one of a portable computer, a tablet, a mobile phone, an energy storage system, an electric vehicle or in a hybrid electric vehicle, preferably in an electric vehicle or in a hybrid electric vehicle

[0134] EXAMPLES

[0135] Description of methods

[0136] Synthesis protocol for the positive electrode active material

[0137] Positive electrode active material with B in surface layer (NMC811-B)

[0138] • Step 1 : Co-precipitation

[0139] A transition metal-based precursor with a metal composition Ni0.86Mn0.07Co0.07 (NMC811) was prepared by a co-precipitation process in a large-scale continuous stirred tank reactor (CSTR.) with mixed nickel manganese cobalt sulfates, sodium hydroxide, and ammonia.

[0140] • Step 2: First heating

[0141] The precursor prepared in Step 1 was heated at 400 °C for 7 hours in an oxidizing atmosphere to obtain a heated product.

[0142] • Step 3: First mixing

[0143] The precursor prepared from Step 2 was mixed with LiOH in an industrial blender to obtain a first mixture having a lithium to metal (Ni, Mn, and Co) ratio of 0.96.

[0144] • Step 4: Second heating

[0145] The first mixture from Step 3 was heated at 890 °C for 11 hours in an oxidizing atmosphere to obtain a first heated product.

[0146] • Step 5: Wet bead milling

[0147] The first heated product from Step 4 was bead milled in a solution containing 0.5 mol% Co with respect to the total molar contents of Ni, Mn, and Co in the first heated product followed by drying and sieving process to obtain a milled product. The bead milling solid to solution weight ratio was 6:4 and was conducted for 20 minutes.

[0148] • Step 6: Second mixing

[0149] The milled product obtained from Step 5 was mixed in an industrial blender with 1.5 mol% Co from CO3O4 and 7.5 mol% Li from LiOH, each with respect to the total molar contents of Ni, Mn, and Co in the milled product to obtain a second mixture.

[0150] • Step 7: Third heating

[0151] The second mixture from Step 6) was heated at 760 °C for 10 hours in an oxidizing atmosphere followed by crushing and sieving with 250 ppm of alumina powder to obtain a third heated product.

[0152] • Step 8: Third mixing

[0153] The second heated product from Step 7) was mixed with H3BO3 as B source to obtain a third mixture comprising 1000 ppm of B with respect to the total molar amount of Ni, Mn, and Co of the third heated material. • Step 9: Fourth heating

[0154] The third mixture from Step 8) was heated at 310°C for 7 hours under an oxygen atmosphere to obtain NMC811-B.

[0155] ICP-OES protocol

[0156] The cathode active material example as described herein below is measured by the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method using an Agilent ICP 720-ES (Agilent Technologies). 2 gram of a powder sample of each example is dissolved into 10 mL high purity hydrochloric acid (at least 37 wt% HCI) in an Erlenmeyer flask. The flask is covered by a watch glass and heated on a hot plate at 380°C until complete dissolution of the sample. After being cooled to room temperature, the solution and the rinsing water of Erlenmeyer flask are transferred to a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with DI water up to the 250 mL mark, followed by complete homogenization.

[0157] Table 1 : ICP-OES values for NMC811-B.

[0158] The median particle size D50 of the positive electrode active material with B in surface layer (NMC811-B) was found to be between 3 and 5 pm.

[0159] Synthesis protocol for the positive electrode composite material

[0160] • Step 1 : Mixing protocol of the positive electrode active material and the sulfide solid electrolyte (SSE)

[0161] All the synthesis work and sample treatment were carried out in Argon filled glovebox with O2 level <10 ppm and H2O level <0.5 ppm. Different formulations of the positive composite active material were prepared, in which the weight ratio (w / w%) of the NMC811-B with the sulfide solid electrolyte (SSE) were respectively 90: 10 and 89.1 : 10.9. The positive electrode active material and the sulfide solid electrolyte (SSE), was Li5.4PS4.4CI1.0Br0.6 (I) or Li3.5PS4Bro.25Io.25 (II), were weighted to obtain a 1.57, 1.75 or 3 g batch mixture. The mixture was transferred into a FRITSCH Planetary Micro Mill PULVERISETTE 7 premium line or classic line using 50 mL zirconia ball-milling jar along with 15-55 g of zirconia balls of 2 to 5 mm diameter (the ball : powder ratio was 6 : 1 in mass). The mixture was milled between 150 to 300 rpm for 5 to 90 min to obtain a homogeneous mixture. Each cycle constituted in 5-minute milling and 5-minute rest and reversing the direction of milling for every cycle. After 5 to 90 min of milling time, the ball-milling jars were opened in the glovebox to recover the mixed powder and the same passed through a sieve with a mesh size of 100 pm to obtain the final mixture of NMC811-B and SSE. At the end, approximately 80 wt% of the material was recovered.

[0162] ICP-OES protocol

[0163] The samples were measured by the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method using an Agilent 5110. About 0.2 gram of a powder sample was first weighed into a microwave vessel in an inert glovebox before ImL DI water and 9mL concentrated nitric acid was added. The sample was placed in a microwave digester at 180 °C for 30 minutes before being diluted again by a factor of 10 for impurity analysis and 100 for matrix analysis. An internal standard is added prior to measurement via ICP-OES and results are reported in at%.

[0164] BET

[0165] To determine the specific surface area (SSA) of the samples the gas adsorption was conducted using the Brunauer-Emmett-Teller (BET) theory Approx. 1 g of sample was weighed into a suitable sized gas adsorption sample vial in an inert atmosphere. The vial was sealed with an appropriate cap and transferred to a Micromeritics VacPrep 061 for pre-treatment. The sample was then heated to 160°C under vacuum for 60 minutes, and then nitrogen for 30 minutes. BET SSA is then measured using a Micromeritics TriStar 3020.

[0166] SEN

[0167] The cross-sectional particle samples was analyzed by JEOL F100 Schottky Field Emission Scanning Electron Microscope (FEG-SEM). The samples were prepared in an inert environment / atmosphere. A straight section of a pelletized sample was placed on the edges between two pieces of conductive metal tape. The exposed edge was ion milled with a JEOL IB-19520CCP broad ion beam miller to prepare the cross- sectional area for analyses. Images of prepared samples were taken at magnifications ranging from lOOOx - 25,000x, at accelerating voltages of 3 kV. o Calculation of the coating thickness by SEN image analysis

[0168] A model was built to perform semantic image segmentation based on a small set of manually labeled SEM images. This model allows to process new images that are masks pixelwise. With these masks advanced metrics are derived. As shown on Figure 5, the coating (2) thickness was calculated by taking N random points within a particle (1) and generating a line (3, 4) originating from each point. Then the amount of coating pixels are starting at the border of the particle until the first noncoated pixel, denoted between the small lines (5) in Figure 5 is calculated. The obtained values are averaged to obtain the coating thickness. As shown on Figure 5, the particles may be only partially coated.

[0169] XPS

[0170] The samples were measured by X-ray photoelectron spectroscopy (XPS) using a THERMOFISHER. K-alpha system with a monochromatic Al Ko x-ray source. A small amount of powder sample was deposited onto a copper tape in a special inert transfer vessel. The vessel was transferred into the main chamber and a vacuum was applied to ensure the sample is not in contact with any atmospheric moisture. Whole-region survey (0 - 1350 eV) and high-resolution scans of elements of interest were collected for analysis. o Calculation of coating coverage by XPS data analysis

[0171] To calculate the coverage rate of the sulfide solid electrolyte, Li5.4PS4.4CI1.0Br0.6 (I) or Li3.5PS4Br0.25I0.25 (II), coating on the particles, XPS spectra were fitted via ThermoFisher Avantage software. The atomic percentages of all elements in the positive electrode composite material (the positive electrode active material and the sulfide solid electrolyte), were added together, and the ratios between the sums calculated. The ratios represent the coverage rate. The formula is below.

[0172] SE coverage rate: (Ep + Es + Eci + EBr + Ei) *100 / (Ep + Es + Eci + EBP + ENI + Erm + Eco + EB) Ep: P percentage, Es: S percentage, Eci: Cl percentage, EBI-: Br percentage, Ei: I percentage, ENI: Ni percentage, EMn : Mn percentage, Ec0: Co percentage, EB: B percentage

[0173] Battery testing

[0174] • Positive electrode fabrication

[0175] The positive electrode composite material, the Li5.4PS4.4Cli.oBro.6 (I) or Li3.5PS4Br0.25I0.25 (II) and acetylene black (AB, conductive auxiliary agent) were weighed in a glove box. The total weight of the powder was about 1 g and a mass ratio was 75 : 22 : 3. Then, the weighed powders were put in a ZrC mill pot with 34 g of ZrO2 balls (<p=2 mm), and they were dry mixed using a roller bench. The rotation speed was 230 rpm, and time was 60 min. The mixed powder was taken out from the ball mill container and passed through a sieve with a mesh size of 100 pm to obtain the positive electrode.

[0176] • Solid-state battery cell

[0177] First step, to make the separator, about 100 mg of pure Li5.4PS4.4CI1.0Br0.6 (I) or Li3.5PS4Br0.25I0.25 (II) was pressed by stainless steel SUS pistons (<p= 10 mm) and compacted by pressing at 1.5 ton / cm2. Then, about 20.4 mg of the respective positive electrode composite material, NMC811-B + Li5.4PS4.4CI1.0Br0.6 (I) + AB (EX1-4 and CEX4), NMC811-B + Li3.5PS4Br0.25I0.25 (II) + AB (EX5) and NMC111-B + Li3.5PS4Br0.25I0.25 (II) + AB (CEX3) or the positive electrode material + Li5.4PS4.4CI1.0Br0.6 (I) or Li3.5PS4Br0.25I0.25 + AB (CEX1 and CEX2) is weighted and placed on top of the separator and pressed at 3.8 ton / cm2. Then, a carbon coated Al foil was placed on the positive electrode layer. Finally, a Ti and Li metal anode are placed under the separator, and the newly assembled positive electrode / solid electrolyte layer / negative electrode sandwich is pressed at 1.3 ton / cm2and bolted to apply pressure at 2N . This all-solid-state battery cell was enclosed using SUS bottle to prevent exposure to air.

[0178] • Battery cycling

[0179] The solid-state battery cell was kept at a constant temperature bath at 60 °C for 4h. Then, the battery was charged using constant current (CC) and constant voltage (CV) After CV charging, the battery was discharged using CC. The battery was rested for 30 min after every charging and discharging. The cut off voltage was 2.5 to 4.3 V. The cut off condition of CV charge was when a current flows for more than 1.5 h at 4.3 V, or when a current equivalent to 0.05C flows at 4.3 V. In the first and second charging cycles, the battery was charged and discharged at 0.382 mA / cm2 (CC), which corresponds to 0.1C.

[0180] After the 2nd cycle, the battery was kept in the constant temperature bath at 25 °C for 20 h. Then the battery was charged and discharged at 0.1C and 1 / 3C in the third cycle and fourth cycle, respectively.

[0181] DCR measurement

[0182] After 4th cycle, the battery was still kept in the same temperature bath to measure direct current resistance (DCR.). After the 4th cycle, the battery was charged at 0.1C up to 3.81V. Then different current was applied and discharged from 3.81 V. DCR was calculated from 5 points and its slope of voltage and discharge current. At each point, different discharge constant current (1.51, 4.53, 7.54, 10.6 and 15.1 mA / cm2) was applied for 30 sec then voltage was recorded. The battery was rested for lOmin after discharge. Then, 0.1C was applied for charging cycle to 3.81 V.

[0183] ACR measurement

[0184] After DCR measurement, the battery was still kept in the same temperature bath to measure alternating Current Resistance (ACR), and it was measured at 3.81 V. The amplitude of ACR measurement was 10 mV. The frequency range was 10E6 to 0.1Hz.

[0185] Examples

[0186] Tables 2 and 3 display the specific experimental conditions for the examples EX1-5 and CEX1-4 synthesized via the general synthesis protocol described above.

[0187] The EX1-4 were prepared with Li5.4PS4.4CI1.0Br0.6 (I) and the comparative example (CEX1) is only NMC811-B (Table 3). The comparative example 4 (CEX4) was synthesized with the same sulfide solid electrolyte, but with agate mortar (Table 3). The EX5 was prepared with Li3.5PS4Br0.25I0.25 (II) and the first comparative example (CEX2) is only NMC811-B, while the second comparative example (CEX3) used the same sulfide solid electrolyte (SSE), but with different cathode active material and synthesis conditions (Tables 2,3). Table 2. Experimental conditions for the examples EX1-5 and CEX1-4 - part 1.

[0188] Table 3. Experimental conditions for the examples EX1-5 and CEX1-4 - part 2. SEM pictures demonstrate that the surface of the positive electrode active material is covered with a coating of Li5.4PS4.4CI1.0Br0.6 (I), in figure la (EX3), and with the

[0189] Li3.5PS4Br0.25I0.25 (II), in figure lb (EX5).

[0190] XPS spectra demonstrate that the B and Ni signals from the positive electrode active material (CEX1-2) is suppressed by the sulfide solid coating (EX1-5) with both types of sulfide solid electrolyte, Li5.4PS4.4CI1.0Br0.6 (I) (Figure 2a) and Li3.5PS4Br0.25I0.25 (II) (Figure 2b). Table 2 and 3 display the characterization results for the examples EX1-5 and CEX1- 4. The characterization techniques were first focused on the properties of the material, by measuring thickness, coverage rate and surface area (BET) and then in the electrochemical properties, by measuring the charge / discharge capacity (Figure 3), current internal resistance (DCIR.) and electrochemical impedance spectroscopy (EIS) (Figure 4). Differential voltage (dV / dQ) curve and coulombic efficiency were also obtained from the charge / discharge capacity data. Table 4. The characterization results for the examples EX1-5 and CEX1-4 - part 1.

[0191] *: Not coated by SE.

[0192] Table 5. The characterization results for the examples EX1-5 and CEX1-4 - part 2.

[0193] - Results discussion with the SSE, Li5.4PS4.4CI1.0Br0.6 (I)

[0194] The ball milling synthesis procedure for preparing Examples 1 to 4 was optimized in terms of ball size, number of milling cycles, milling time, and speed, as detailed in Table 4 and 5. This optimization resulted in samples exhibiting different properties, ranging from 81 to 331 nm in thickness, from 70 to 99 % in coverage rate, and from 0.59 to 1.16 m2 / g in BET as shown in Table 4.

[0195] Several electrochemical tests were performed and the results for EX1-4 where compared with CEX1 (NMC8111-B) are shown in Table 5.

[0196] By looking at the charge / discharge results in Table 5 and the charge / discharge curves in Figure 3a, it is possible to observe that cell capacity of EX3 is higher than CEX1, demonstrating the positive effect of the SE coating layer. Further comparison of EX1-3 with the EX4, as illustrated in Table 5 and Figure 3b, reveals an increase in cell capacity in the order of EX3 > EX2 > EXI > EX4. This trend suggests that the thickness of the SE layer influences the charge / discharge capacity of the cell, reaching a positive benefit around 300 nm (EX4). Table 5 also shows the standing voltage in dq / dv curve during charge and discharge process, revealing that EX3 has the higher charge capacity at lower voltage (3.56 V) and a higher discharge capacity at higher voltage (4.27 V). A comparison of all examples, EX1-4, with CEX1, shows superior results in the standing voltage of dq / dv for EX1-4 EX3 shows the highest efficiency.

[0197] Additionally, as shown in Table 5, the direct current internal resistance (DCIR) of EX1-3 (23, 32 and 30 Ohmcm2, respectively) is significantly lower than that of CEX1 (36 Ohmcm2). This suggests that the SE coating layer in positive electrode composite material decreased interface resistance between the Li5.4PS4.4CI1.0Br0.6 (I) electrolyte and positive electrode material. When comparing EX1-2 to EX3, the DCIR values of EX3 is smaller than that of EX1-2 and EX4 (41 Ohmcm2), which suggests that an excessive increase of thickness in SE coating layer gives a negative effect. The electrochemical impedance spectroscopy (EIS) shown in Figure 4a and 4b exhibits a behavior consistent with the DCIR results, with EX3 demonstrating the smallest resistance. The EX4 indicates that there may be a limit in thickness from which the SE coating layer on the positive electrode active material no longer exhibits a beneficial effect (below 331 nm).

[0198] An additional comparative example CEX4, was prepared using an agate mortar instead of the ball milling method (Table 3). In Table 5, it is possible to observe that all the electrochemical tests show inferior performances when compared with the EX1-4.

[0199] - Results discussion with the SSE, Li3.5PS4Br0.25I0.25 (II)

[0200] Several electrochemical tests were performed and the results for EX5 where compared with CEX2 (NMC811-B) and CEX3, as shown in Table 4 and 5.

[0201] Initially, by examining the charge / discharge results in Table 5 and the charge / discharge curves in Figure 3c, it can be observed that the cell capacity of EX5 surpasses that of CEX2, demonstrating the positive effect of the SE coating layer. The same outcome is observed when comparing EX5 with CEX3, suggesting that the thickness of the SE layer and composition of positive electrode active material influence the charge / discharge capacity of the cell. Furthermore, Table 5 also presents the standing voltage in dq / dv curve during charge and discharge process, revealing that EX5 has a higher charge capacity at a lower voltage (3.51 V) and a higher discharge capacity at a higher voltage (4.27 V) compared to CEX2 (3.61 V and 4.22 V, respectively) and CEX3 (3.60 V and 4.27 V, respectively). EX5 shows the highest efficiency.

[0202] Additionally, as shown in Table 5, the direct current internal resistance (DCIR) of EX5 (34 Ohmcm2) is significantly lower than that of CEX2 (63 Ohmcm2). This suggests that the SE coating layer in positive electrode composite material decreased interface resistance between the Li3.5PS4Bro.25Io.25 (II) electrolyte and positive electrode material. When comparing EX5 to CEX3, the DCIR value of EX5 is smaller than that of CEX3 (45 Ohmcm2), which suggests that there is an optimum thickness of SE coating layer. The Electrochemical Impedance Spectroscopy (EIS) results in Figure 4 c) exhibit a behavior consistent with the DCIR results, with EX5 demonstrating lower resistance.

Claims

CLAIMS1. A positive electrode composite material comprising :• particles of a positive electrode active material comprising Li, M', and 0, wherein M' comprises:- Ni in a content x, wherein 45.0 at% < x < 95.0 at%, relative to M';- Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M';- Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M';- N' in a content w, wherein 0.01 at% < w < 2.0 at%, relative to M', wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof;- D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, N' and O; and- wherein x + y + z + w+ q is 100.0 at% and x, y, z, w and q are measured by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES);• and a sulfide solid electrolyte;• wherein the sulfide solid electrolyte covers at least a part of the surface of the particles forming a coating.

2. The positive electrode composite material according to claim 1, wherein N' is one element selected from the group consisting of B, Zr, Nb, Ti, Sr and W; preferably N' is one element selected from the group consisting B, Zr, Nb, Ti, and W; more preferably N' is one element selected from the group consisting B, Zr, Nb and Ti; even more preferably N' is one element selected from the group consisting B, Zr and Nb.

3. The positive electrode composite material according to claim 1 or 2, wherein- Ni in a content x, wherein 70.0 at% < x < 85.0 at%, relative to M';- Mn in a content y, wherein 5.0 at% < y < 20.0 at%, relative to M';- Co in a content z, wherein 5.0 at% < z < 20.0 at%, relative to M';- N' in a content w, wherein 0.01 at% < w < 1.5 at%, relative to M'.

4. The positive electrode composite material according to claim 3, wherein 0.1 at% < w < 1.4 at%, preferably 0.25 at% < w < 1.3 at%, more preferably 0.5 at% < w < 1.0 at%.

5. The positive electrode composite material according to any one preceding claim, wherein the positive electrode active material comprises single particles and / or secondary particles, wherein each of the single particles consist of only one primary particle and each of the secondary particles consist of at least two primary particles and at most twenty primary particles as observed in a Scanning Electron Microscope (SEM) image.

6. The positive electrode composite material according to any one preceding claim, wherein the coating has a thickness between 50 and 300 nm, preferably between 65 and 275 nm, more preferably between 80 and 250 nm.

7. The positive electrode composite material according to any one preceding claim, wherein the coating covers at least 70 % of the surface of the particles, preferably at least 80 %, more preferably at least 90 %, even more preferably at least 95 %, even more preferably at least 98 %, most preferably the whole surface of the particles.

8. The positive electrode composite material according to any one preceding claim, wherein a specific surface area of the positive electrode composite material is between 0.3 and 1.5 m2 / g, preferably between 0.4 and 1.25 m2 / g, more preferably between 0.5 and 1.0 m2 / g.

9. The positive electrode composite material according to any one preceding claim, having a median particle size D50 of the positive electrode active material is between 1 and 15 pm, preferably between 2 and 10 pm, more preferably between 3 and 5 pm.

10. The positive electrode composite material according to any one preceding claim, wherein the solid sulfide electrolyte comprises Li, P and S.

11. The positive electrode composite material according to any one preceding claim, wherein the solid sulfide electrolyte is according to the formula (I)Li6-yPS5-yXl+y (I)wherein -0.5 < y < 1 and X is at least one of F, Cl, Br or I.

12. The positive electrode composite material according to claim 11, wherein -0.2 < y < 0.9, preferably 0 < y < 0.8, more preferably 0.2 < y < 0.7, even more preferably 0.5 < y < 0.

713. The positive electrode composite material according to any one of claims 1 to10, wherein the sulfide solid electrolyte is according to the formula (II)Li4-zPS4Xz (II) wherein 0 < z < 1 and X is at least one of F, Cl, Br or I.

14. The positive electrode composite material according to claim 13, wherein 0.1 < z < 1.0, preferably 0.2 < z < 0.9, more preferably 0.3 < z < 0.8, even more preferably 0.4 < z < 0.

715. The positive electrode composite active material according to any one preceding claim, wherein the weight ratio (w / w) of the positive electrode active material to the sulfide solid electrolyte is at least 70:30, preferably at least 80:20, even more preferably at least 85: 15, most preferably at least 90: 10.

16. A method for preparing the positive electrode composite material according to any one of claims 1 to 15, comprising the steps of: a) providing at least the following precursors:• a positive electrode active material comprising Li, M', and O, wherein M' comprises: o Ni in a content x, wherein 45.0 at% < x < 95.0 at%, relative to M'; o Mn in a content y, wherein 0.0 at% < y < 40.0 at%, relative to M'; o Co in a content z, wherein 0.0 at% < z < 40.0 at%, relative to M'; o N' in a content w, wherein 0.01 at% < w < 2.0 at%, relative to M', wherein N' is selected from the group consisting of B, Zr, Nb, Ti, Sr, W and combinations thereof;o D in a content q, wherein 0.0 at% < q < 2.0 at%, relative to M', wherein D is at least one element other than Li, Ni, Mn, Co, N' and 0; and o wherein x + y + z + w+ q is 100.0 at% and x, y, z, w and q are measured by ICP-OES;• a sulfide solid electrolyte;• optionally a carbon-based conductive aid; b) mixing of the precursors to afford the positive electrode composite material.

17. The positive electrode composite material obtainable by the method according to claim 16.

18. A battery comprising a positive electrode comprising the positive electrode composite material according to any one of claims 1-15 or 17, a further solid electrolyte and a negative electrode.

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