Positive electrode for a battery

Abstract

The present invention relates to a positive electrode comprising a positive electrode active material and a sulfide solid electrolyte with a low particle size, and additionally a conductive agent and a binder. The present invention further relates to a method for manufacturing said positive electrode and a battery comprising said positive electrode.

Description

DESCRIPTIONTitlePositive Electrode for a batteryTechnical field

[0001] The present invention relates to a positive electrode comprising a positive electrode active material and a sulfide solid electrolyte with a low particle size, and additionally a conductive agent and a binder. The present invention further relates to methods for manufacturing said positive electrode and a battery comprising said positive electrode.Description of related art

[0002] Solid-sate rechargeable batteries are of particular interest as they may reach particularly high energy density, combined with a higher level of safety because of the absence of flammable organic liquid electrolyte.

[0003] Various ways for improving the performance of solid-state rechargeable batteries are being explored. An important key to prepare 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. One way to achieve this is to prepare a positive electrode active material incorporated with a solid electrolyte material creating a better contact between them.

[0004] 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, so a way to mitigate this problem is to add a buffer layer to the positive active material, such as boron or niobium coating.

[0005] CN 11347143 A 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 and a sulfide solid electrolyte coating including a conductive auxiliary agent.

[0006] It is an object of the present invention to provide an improved positive electrode with an improved electrochemical performance, in particular regarding charge capacity (CQ1), discharge capacity (DQ1) and efficiency, simultaneously.SUMMARY

[0007] A positive electrode for a lithium-metal rechargeable battery comprising a current collector plate bearing an active material coating, the active material coating 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';D in a content a, wherein 0.0 at% < a < 5.0 at%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr; and wherein x + y + z + a is 100.0 at% and x, y, z and a are measured by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES);• particles of a sulfide solid electrolyte;• a conductive agent;• a binder; wherein the positive electrode active material has a particle size distribution value D50 lower than or equal to 2.0 pm and wherein the sulfide solid electrolyte has a particle size distribution value D50 lower or equal to 1.0 pm .

[0008] The inventors have found that the positive electrode described in this invention comprising a positive electrode active material with a D50 lower or equal to 2.0 pm and a sulfide solid electrolyte with a D50 lower or equal to 1.0 pm, surprisingly enhances the electrochemical performance of batteries, in particular regarding charge capacity (CQ1), discharge capacity (DQ1) and efficiency, simultaneously.

[0009] In another aspect of the invention there is a method for preparing the positive electrode material described in the invention.

[0010] In the following detailed description, preferred embodiments are described in detail to enable practice of the present disclosure. Although the present disclosure is described with reference to these specific preferred embodiments, it will be understood that the present disclosure is not limited to these preferred embodiments. To the contrary, the present disclosure includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description and accompanying drawings.Unless otherwise indicated, it is not meant that the alternatives, modifications, and equivalents described herein are understood as separate, non-combinable, embodiments. That is, provided it is technically feasible, the different parts of the present disclosure may be combined with one another.

[0011] "ICP-OES" as used herein refers to Inductively Coupled Plasma - Optical Emission Spectrometry. The method of determining metal compositions using ICP-OES and its meaning are described herein below.

[0012] "at%" signifies atomic percentage. The at% or "atomic percent" of a given element means a percentage of atoms of said element among all atoms in a claimed composition. ICP-OES provides weight percent (wt%) of each element included in a material whose composition is determined by this technique. Conversion from wt% to at%, as is well known to the person skilled in the art, is as follows: at% of a first element Ei Eati) in a material can be converted from a given wt% of said first element Ei EVM ) in said material by applying the following formula,

[0013] wherein Eawiis a standard atomic weight (molecular weight) of the first element Ei, Ewtiis wt% of an ithelement Ei, Eawiis a standard atomic weight (molecular weight) of said ithelement , and n is an integer which represents the number of types of all elements included in the material.

[0014] "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.

[0015] "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.

[0016] As used herein, a range of values "from X to Y" and "between X and Y" includes the endpoints X and Y.

[0017] "Milling" as used herein is the action of reducing the size of particles by a mechanical action submitting the particles to a stress. Some cracks will appear under the stress, and subsequently the particle will be broken in different parts.

[0018] "Homogeneous" as used herein may refer to a state of a blend with different powdered substances in which the components are uniformly distributed throughout the mixture. In other words, every sample of the homogeneous mixture may exhibit almost the same proportions of each substance.Detailed description

[0019] In an embodiment, the first positive electrode active material 55 at% < x < 95 at%, preferably 65 at% < x < 92 at%, and more preferably 70 at% < x < 90 at%, relative to M'.

[0020] In an embodiment, the first positive electrode active material 2 at% < y < 20 at%, preferably 4 at% < y < 15 at%, and more preferably 5 at% < y < 10 at%, relative to M'.

[0021] In an embodiment, the first positive electrode active material 2 at% < z < 20 at%, preferably 4 at% < z < 15 at%, and more preferably 5 at% < z < 10 at%, relative to M'.

[0022] In an embodiment, the first positive electrode active material D comprises B, wherein 0.01 at% < a < 2 at%, preferably 0.02 at% < a < 1.0 at%, more preferably 0.05 at% < a < 0.5 at%, even more preferably 0.1 at% < a < 0.2 relative to M'.

[0023] Preferably, the particle size distribution of the positive electrode active material and the sulfide solid electrolyte is measured by laser scattering.

[0024] In an embodiment, the positive electrode active material has a particle size distribution value D50 lower than or equal 2.0 pm.

[0025] In an embodiment, the positive electrode active material has a particle size distribution value D50 of at least 0.5 pm, preferably at least 1.0 pm, more preferably at least 1.5 pm, even more preferably at about 2.0 pm.

[0026] In an embodiment, 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 consists of at least two primary particles and at most twenty primary particles as observed in a Scanning Electron Microscope (SEM) image.

[0027] In an alternative embodiment, the positive electrode active material comprises secondary particles wherein each of the secondary particles consists of at least twenty primary particles, in particular as observed in a SEM image.

[0028] 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

[0029] In an embodiment, the sulfide solid electrolyte comprises Li, P and S.

[0030] In a preferred embodiment, the sulfide solid electrolyte is according to the formula (I)Lie-tPSs-tXi+t (I) wherein -1.00 < t < 1.00 and X is at least one of F, Cl, Br and I.

[0031] In a preferred embodiment, -0.99 < t < 0.99, preferably -0.75 < t < 0.75, more preferably - 0.5 < t < 0.5, even more preferably t = 0.

[0032] In a preferred embodiment, X is F, Cl, Br and I, preferably X is Cl, Br and I, more preferably X is Cl and Br, even more preferably X is Cl.

[0033] In an embodiment, the sulfide solid electrolyte precursor has a particle size distribution value D50 of at least 0.25 pm, preferably D50 is at least 0.5 pm, more preferably D50 is at least 0.75 pm, even more preferably is at least 0.90 pm.

[0034] In an embodiment, the conductive agent is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, graphite; Carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide andpotassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used. In an embodiment of the positive electrode, the conductive agent comprises carbon black powder, carbon nanotube, or carbon nanofiber.

[0035] In an embodiment, the binder is a component that assists in the bonding of the active material and the conductive material and in the bonding to the current collector.

[0036] In an embodiment, the binder may include one or more of polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene (PE), and polypropylene, ethylene-propylene- diene monomer, sulfonated ethylene-propylene-diene monomer, styrenebutadiene rubber, fluorine rubber, various copolymers, etc. In an embodiment of the positive electrode, the binder comprises polyvinylidene fluoride (PVDF).

[0037] In an embodiment, the positive electrode comprises in weight % relative to relative to the total amount of positive electrode active material, sulfide solid electrolyte, conductive agent and binder:• a positive electrode active material content w, wherein 55% < w < 88.5%;• a sulfide solid electrolyte content h, wherein 10% < h < 30%;• a conductive agent content k, wherein 0.5% < k < 5%;• a binder content q, wherein 1% < q < 5%; and

[0038] wherein w+h + k+q = 100%.

[0039] In a preferred embodiment, the positive electrode comprises in weight % relative to relative to the total amount of positive electrode active material, sulfide solid electrolyte, conductive agent and binder:

[0040] a positive electrode active material content w, wherein 65 % < w < 80%;• a sulfide solid electrolyte content h, wherein 15 % < h < 25%;• a conductive agent content k, wherein 1% < k < 3%;• a binder content q, wherein 0.5% < q < 2%; and

[0041] wherein w+h + k+q = 100%.

[0042] In an embodiment, the positive electrode further comprises a current collector. The positive electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery. The current collector may comprise stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon coated aluminum or stainless steel coated with carbon, nickel,titanium or silver. Advantageously, the positive electrode current collector comprises aluminum, in particular an aluminum foil, a carbon coated aluminum foil or a stainless steel foil. Examples of JIS steel types include SUS304, SUS316L, and SUS310S for austenite type steel, and SUS436, SUS444, and SUS447J1 for ferrite type steel.

[0043] The present disclosure further concerns a method for preparing a positive electrode for lithium metal rechargeable battery, in particular a positive electrode according to an embodiment or combination of embodiments disclosed herein, comprising: a. Providing positive electrode material precursors comprising a positive electrode active material, a sulfide solid electrolyte, a conductive agent and a binder mixed homogeneously in a solvent, wherein the positive electrode active material has a particle size distribution value D50 lower than or equal to 2.0 pm and wherein the sulfide solid electrolyte has a particle size distribution value D50 lower than or equal to 1.0 pm; b. Providing a current collector; c. Coating the current collector by spreading the mixture on the current collector; and d. Drying and pressing the coated current collector.

[0044] In an embodiment of the method of the present disclosure, the positive electrode active material has a particle size distribution value D50 of at least 0.5 pm, preferably at least 1.0 pm, more preferably at least 1.5 pm, even more preferably at 2.0 pm.

[0045] In an embodiment of the method of the present disclosure, the sulfide solid electrolyte precursor has a particle size distribution value D50 of at least 0.25 pm, preferably D50 is at least 0.5 pm, more preferably D50 is at least 0.75 pm, even more preferably is at least 0.90 pm.

[0046] In an embodiment of step a) of the method of the present disclosure, the positive electrode active material may be provided in a total amount of 55 % to 90% by weight, preferably 60% to 80% by weight, and more preferably 65 % to 75% by weight, based on the total weight of solids. Solids exclude the solvent and may in particular comprise or consist of positive electrode active material, sulfide solid electrolyte, conductive agent and binder.

[0047] In an embodiment of step a) of the method of the present disclosure, the sulfide solid electrolyte may be provided in a total amount of 10 % to 30% by weight, preferably 15% to 25% by weight, and more preferably 20 % to 24% by weight, based on the total weight of solids. Solids exclude the solvent and may in particular comprise or consist of positive electrode active material, sulfide solid electrolyte, conductive agent and binder.

[0048] In an embodiment of step a) of the method of the present disclosure, the conductive material may be provided in an amount of 0.5% to 5% by weight, preferably 1.0% to 4% by weight, more preferably 1.5% to 3% by weight by weight, based on the total weight of solids. Solids exclude the solvent and may in particular comprise or consist of positive electrode active material, sulfide solid electrolyte, conductive agent and binder.

[0049] In an embodiment of step a) of the method of the present disclosure, the binder may be contained in an amount of 1% to 5% by weight, preferably 1.25% to 4% by weight, more preferably 1.5% to 3% by weight, based on the total weight of solids. Solids exclude the solvent and may in particular comprise or consist of positive electrode active material, sulfide solid electrolyte, conductive agent and binder.

[0050] In the method of the present disclosure, the solvent may include an organic solvent such as for example butyl acetate, heptane, hexane, butyl butylate, isobutyl isobutylate, xylene, mesitylene or N-methyl-2-pyrrolidone (NMP).

[0051] In an embodiment of step a) of the method of the present disclosure, the solid concentration including the positive electrode active material, the sulfide solid electrolyte, the conductive material and the binder is 40% to 80% by weight, preferably 45% to 75% by weight, more preferably 50% to 70% by weight. In the method of the present disclosure, the solvent may be provided in an amount that achieves a desirable viscosity for subsequent process steps.

[0052] The present disclosure further concerns a lithium metal secondary battery comprising a positive electrode according to an embodiment or any combination of embodiments disclosed herein.

[0053] The lithium metal secondary battery of the present disclosure may comprise a Li or Li alloy negative electrode. Example Li alloys are Li-Si, Li-Sn, Li-Ge, Li-AI, Li-In, Li-Mg.

[0054] The present invention further concerns the use of a battery according to any embodiment of the present disclosure in a portable computer, tablet, a mobilephone, an energy storage system, an electric vehicle or in a hybrid electric vehicle, preferably in an electric vehicle or in a hybrid electric vehicle.EXPERIMENTAL ANALYSIS USED IN THE EXAMPLES AND THE COMPARATIVE EXAMPLE

[0055] The following analysis methods are used in the Examples and the Comparative Example.A) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) measurement

[0056] The amount of Ni, Mn, Co, and D in the positive electrode active material powder is measured with the ICP-OES method by using an Agilent ICP 720-ES (Agilent Technologies). 2 grams of powder sample is dissolved into 10 mL of high purity hydrochloric acid (at least 37 wt% of HCI with respect to the total weight of solution) in an Erlenmeyer flask. The flask is covered by a glass and heated on a hot plate at 380 °C until complete dissolution of the precursor. After being cooled to room temperature, the solution of the Erlenmeyer flask is poured into a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with deionized water up to the 250 mL mark, followed by complete homogenization.B) Particle size analysis

[0057] The particle size distribution (PSD) of the positive electrode active material powder is measured by laser diffraction particle size analysis using a Malvern Mastersizer 3000 with a Hydro MV wet dispersion accessory after having dispersed each of the powder samples in an aqueous medium. In order to improve the dispersion of the powder, sufficient ultrasonic irradiation and stirring are applied, and an appropriate surfactant is introduced. D50 is defined as the particle size at 50% of the cumulative volume% distributions. PSD span is calculated according to the below equation:C) Sulfide solid-state rechargeable cell testCl) Sulfide solid-state rechargeable cell preparationCl.l) Negative electrode preparation

[0058] For the preparation of a negative electrode, Li foil (diameter 3 mm, thickness 100 pm) is placed centered on the top of In foil (diameter 9 mm, thickness 100 pm) and pressed to form Li-In alloy negative electrode.Cl.2) Separator preparation

[0059] For the preparation of a separator which also has a function of the solid electrolyte in a battery, the Li-P-S based solid electrolyte is pelletized with a pressure of 250 MPa to obtain 100 pm pellet thickness.Cl.3) Cell accembling

[0060] A sulfide solid-state rechargeable battery is assembled in an Ar-filled glovebox with such order from bottom to top: positive electrode comprising Al current collector with the coated part on the top - separator - negative electrode with Li side on the top - Cu current collector. The stacked components are pressed together with a pressure of 250 MPa and placed in an external cage to prevent air exposure.C2) Testing method

[0061] The testing method is a conventional "constant cut-off voltage" test. Each cell is cycled at 60 °C using a Toscat-3100 computer-controlled galvanostatic cycling station (from Toyo).

[0062] The schedule uses a 1C current definition of 160 mA / g. The initial charge capacity (CQ1) and discharge capacity (DQ1) are measured in constant current mode (CC) at C rate of 0.1 C in voltage range from 4.3 V to 2.5 V (Li / Li+) or from 3.7 V to 1.9 V (In-Li / Li+). The efficiency (%) of the irreversible capacity is obtained according to an equation below: 100(%).EXAMPLES

[0063] The present disclosure is further illustrated in the following examples.Positive electrode active material 1 (CAM1)

[0064] A positive electrode active material CAM1 was obtained through following steps:1) First mixing: Nio.85Mno.o7Coo.o8(OH)2powder was homogeneously mixed with LiOH to prepare a first mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co was 1.04 at% .2) First heating : the first mixture was heated at 880 °C for 11 hours under oxygen atmosphere followed by cooling, grinding, and sieving to prepare a first heated material.3) Wet milling : the first heated material was milled with beads in an aqueous solution containing CoSC followed by filtering and drying to prepare a milled material having D50 of between 3 pm and 3.5 pm, wherein 0.5 at% Co relative to total amount of Ni, Mn, and Co in the first heated material.4) Second mixing: the milled material was mixed with LiOH and CO3O4 homogeneously to prepare a second mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co is 0.99 and 1.5 at% Co relative to total amount of Ni, Mn, and Co in the milled material was added.5) Second heating: the second mixture was heated at 760 °C for 9 hours under oxygen atmosphere followed by cooling and grinding to prepare a second heated material.6) Third mixing : the second heated material was mixed with AI2O3 and H3BO3 to prepare a third mixture, wherein 500 ppm Al relative to amount of the second heated material was added and then 1000 ppm B relative to amount of the second heated material was added.7) Third heating: the third mixture was heated at 350 °C for 7 hours to obtain a positive electrode active material CAM1.Positive electrode active material 2 (CAM2)

[0065] A positive electrode active material CAM2 was obtained through following steps:1) First mixing: Nio.85Mn0.o7Coo.o8(OH)2powder was homogeneously mixed with LiOH and N2O5 to prepare a first mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co was 1.04 and 0.5 at% Nb relative to total amount of Ni, Mn, and Co was added.2) First heating : the first mixture was heated at 885 °C for 10 hours under oxygen atmosphere followed by cooling, grinding, and sieving to prepare a first heated material.3) Wet milling: the first heated material was milled with beads in deionized water followed by filtering and drying to prepare a milled material having D50 of between 1.25 pm and 1.35 pm and D100 less than 3.5 pm.4) Second mixing: the milled material was mixed with LiOH homogeneously to prepare a second mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co is 0.99.5) Second heating: the second mixture was heated at 700 °C for 10 hours under oxygen atmosphere followed by cooling and grinding to prepare a second heated material.6) Third mixing: the second heated material was mixed with H3BO3 to prepare a third mixture, wherein 2000 ppm B relative to amount of the second heated material was added.7) Third heating: the third mixture was heated at 300 °C for 6 hours to obtain a positive electrode active material CAM2.Comparative Example 1 (CEX1)

[0066] A positive electrode CEX1 was obtained by preparing a slurry containing CAM1, SEI, carbon (Super-P, Timcal), and binder (R.C-10, Arkema) in butyl acetate solvent with mass ratio of 75:21.5:2: 1.5, wherein SEI has a D50 value of 3.7 pm and PSD span of 1.5, purchased from POSCO JK SOLID SOLUTION. The slurry was cast on one side of an aluminum foil followed by drying the slurry coated foil in a vacuum oven to obtain a positive electrode. The obtained positive electrode is punched with a diameter of 10 mm wherein the active material loading amount is around 4 mg / cm2.Comparative Example 2 (CEX2)

[0067] A positive electrode CEX2 was obtained following the same method of preparing CEX1 except that SE2 was used instead of SEI as a solid electrolyte, wherein SE2 has a D50 value of 1.0 pm and PSD span of 2.6, purchased from POSCO JK SOLID SOLUTION.Comparative Example 3 (CEX3)

[0068] A positive electrode CEX3 was obtained following the same method of preparing CEX1 except that CAM2 was used instead of CAM1 as an active material.Example 1 (EXI)

[0069] A positive electrode EXI was obtained following the same method of preparing CEX2 except that CAM2 was used instead of CAM1 as an active material.Table 1. Summary of PSD results of CAM1, CAM2, SEI, and SE2Table 2. Summary of electrochemical testing results of CEX1, CEX2, CEX3, and EXI.Results discussion

[0070] According to Table 2, when the positive electrode is prepared with NMC 811 with a particle size D50 3.5 pm (CEX1) and LPSCI with a particle size D50 3.7 pm the initial charge capacity (CQ1) is 233.4 mAh / g and the initial discharge capacity (DQ1) is 213 mAh / g, these values increase to 234.6 and 222.9 mAh / g, respectively, when the particle size D50 of the LPSCI decreases from 3.7 to 1.0 pm (CEX2). This suggests that a smaller particle size of LPSCI has a positive effect in the final performance of the positive electrode.

[0071] The results of Table 2, also show that when the positive electrode is prepared with NMC811 with a particle size D50 2.0 pm and LPSCI with a particle size D50 3.7 pm (CEX3) the values of CQ1 and DQ1 decrease to 226.9 mAh / g and 211.8 mAh / g, respectively, when compared with CEX1 and CEX2 (Table 1).

[0072] However, when the positive electrode is prepared with NMC811 with a particle size D50 2.0 pm and LPSCI with a particle size D50 1.0 pm (EXI) the values of CQ1 and DQ1 are 234.9 mAh / g and 225.2 mAh / g, respectively. These results surprisingly show that, the best charge / discharge results (Table 2), are obtained when NMC811 and SE have the smallest particle size, 2 pm and 1 pm, respectively.When looking at efficiency, EXI shows also the highest value, 95.9 %, in comparison with CEX1-3.

Claims

CLAIMS1. A positive electrode for a lithium-metal rechargeable battery comprising a current collector plate bearing an active material coating, the active material coating 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';- D in a content a, wherein 0.0 at% < a < 5.0 at%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr; and wherein x + y + z + a is 100.0 at% and x, y, z and a are measured by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES);• particles of a sulfide solid electrolyte;• a conductive agent;• a binder;• wherein the positive electrode active material has a particle size distribution value D50 lower than or equal to 2.0 pm and wherein the sulfide solid electrolyte has a particle size distribution value D50 lower or equal to 1.0 pm.

2. The positive electrode composite according to claim 1, wherein 55 at% < x < 95 at%, preferably 65 at% < x < 92 at%, and more preferably 70 at% < x <90 at%, relative to M'.

3. The positive electrode composite according to claim 1 or 2, wherein 2 at% < y < 20 at%, preferably 4 at% < y < 15 at%, and more preferably 5 at% < y < 10 at%, relative to M'.

4. The positive electrode according to any one preceding claim, wherein 2 at% < z < 20 at%, preferably 4 at% < z < 15 at%, and more preferably 5 at% < z < 10 at%, relative to M'.

5. The positive electrode according to any one preceding claim, wherein D comprises at least B and wherein 0.01 at% < a < 2 at%, preferably 0.02 at% < a < 1.0 at%, more preferably 0.05 at% < a < 0.5 at%, even more preferably 0.1 at% < a < 0.2 relative to M'.

6. The positive electrode 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 consists of at least two primary particles and at most twenty primary particles as observed in a Scanning Electron Microscope (SEM) image.

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

8. The positive electrode according to any one preceding claim, wherein the sulfide solid electrolyte is according to the formula (I)Lie-tPSs-tXi+t (I) wherein -1.00 < t < 1.00 and X is at least one of F, Cl, Br or I.

9. The positive electrode according to claim 8, wherein -0.99 < t < 0.99, preferably -0.75 < t < 0.75, more preferably - 0.5 < t < 0.5, even more preferably t = 0.

10. The positive electrode according to any one preceding claim, wherein the positive electrode comprises in weight % relative to the total amount of positive electrode active material, sulfide solid electrolyte, conductive agent and binder:• a positive electrode active material content w, wherein 55% < w < 88.5 %;• a sulfide solid electrolyte content h, wherein 10% < h < 30%;• a conductive agent content k, wherein 0.5% < k < 5%;• a binder content q, wherein 1% < q < 5%; andwherein w+h+k+q = 100%.

11. A method for preparing a positive electrode for a lithium metal rechargeable battery according to any one of claims 1 to 10, comprising the steps of: a. Providing positive electrode material precursors comprising a positive electrode active material, a sulfide solid electrolyte, a conductive agent, and a binder mixed homogeneously in a solvent, wherein the positive electrode active material has a particle size distribution value D50 lower than or equal to 2.0 pm and wherein the sulfide solid electrolyte has a particle size distribution value D50 lower than or equal to 1.0 pm; b. Providing a current collector; c. Coating the current collector by spreading the mixture on the current collector; and d. Drying and pressing the coated current collector.

12. A lithium metal secondary battery comprising a positive electrode according to any one of claims 1 to 10.

13. Use of a battery according to claim 12 in either one of a portable computer, 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.

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