Iron sulfide based positive electrode active material powder

Abstract

The present invention concerns a positive electrode active material powder comprising iron disulfide, a sulfur source, a carbon source and a lithium based argyrodite compound and having a ratio A / B, wherein 0.05 < A / B < 0.40, with A representing the crystallite size of the lithium based argyrodite compound and B representing the crystallite size of iron disulfide.

Description

DescriptionTitleIron sulfide based positive electrode active material powderTechnical Field

[0001] The present disclosure concerns an iron sulfide positive electrode active material powder, in particular for an all solid state secondary battery. The present disclosure further concerns a method for manufacturing said positive electrode active material powder and an all solid state secondary battery comprising said positive electrode active material powder.Background

[0002] Sulfur composite electrodes in solid-state batteries offer several advantages leverage the high theoretical capacity of sulfur, which can significantly enhance the energy density of batteries. Additionally, sulfur is abundant, cost-effective, and environmentally friendly. However, the primary challenges include the intrinsic insulation of sulfur, which necessitates the use of conductive additives to ensure efficient electron transport. The volume expansion of sulfur during cycling can also lead to mechanical instability and loss of contact within the electrode. Furthermore, the formation of intermediate polysulfides can cause degradation of the solid-state electrolyte and reduce the overall efficiency of the battery.

[0003] There is still a need in the art to find ways to improve capacity, in particular capacity retention for such batteries, in particular having a high loading of positive electrode active material powder.Summary

[0004] The present disclosure concerns a positive electrode active material powder comprising iron disulfide, a sulfur source, a carbon source and a lithium based argyrodite compound and having a ratio A / B, wherein 0.05 < A / B < 0.40, with A being the crystallite size of the lithium based argyrodite compound, and B being the crystallite size of iron disulfide, as determined by X-ray diffraction analysis and Le Bail refinement.

[0005] The positive electrode active material powder of the present disclosure, in any embodiment or combination of embodiments may in particular be intended for an all solid state battery.

[0006] The inventors have found such positive electrode active material powder, when used in an all-solid-state battery, may provide increased capacity retention after 50 cycles of at least 55%, even at least 65%, in particular at a 50th cycle discharge capacity of more than 100mAh / g.

[0007] The present disclosure further concerns a method for preparing said positive electrode active material powder comprising in sequence:1) providing a first mixture comprising iron disulfide, a sulfur source, and a carbon source;2) milling the first mixture to obtain a milled first mixture;3) combining the milled first mixture with a lithium-based argyrodite compound to obtain a combined milled first mixture;4) milling the combined milled first mixture and lithium-based argyrodite so as to obtain a second milled mixture; and5) optionally, sieving the second milled mixture;to obtain a positive electrode active material powder.

[0008] The inventors have found that the so obtained positive electrode active material powder, when used in an all-solid-state battery, may provide increased capacity retention after 50 cycles of at least 55%, even at least 65%, in particular at a 50th cycle discharge capacity of more than 100mAh / g.

[0009] The positive electrode active material powder obtained by the method of the present disclosure, in any of its embodiments or combination of embodiments may comprise iron disulfide, a sulfur source, a carbon source and a lithium based argyrodite compound and presents having a ratio A / B, wherein 0.05 < A / B < 0.40, with A being the crystallite size of the lithium based argyrodite compound and B being the crystallite size of iron disulfide. The crystallite sizes are preferably determined from a Le Bail refinement using both phases of the X-Ray powder diffraction patterns. The crystallites sizes are calculated from the half-widths of all (hkl) planes of both phases included between 10 and 80° using a copper anticathode. Advantageously 0.05 < A / B < 0.40; more advantageously 0.05 < A / B < 0.35; 0.05 < A / B < 0.30; or even 0.10 < A / B < 0.25.

[0010] The positive electrode active material powder obtained by the method of the present disclosure, in any of its embodiments or combination of embodiments may inparticular be a positive electrode active material powder of the present disclosure, in an of its embodiments or combination of embodiments.

[0011] The present disclosure provides a all-solid-state secondary battery, in particular a Li ion rechargeable battery, comprising said positive electrode active material powder according to any embodiment or combination of embodiments of the present disclosure.

[0012] The present disclosure also provides the use of said battery in in an electrically powered device or system selected from the group consisting of: a portable computer, a tablet, a mobile phone, a telecommunication device, a power tool, mobile machinery, a robotic device, an energy storage system, an uninterruptible power supply system, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an extended-range electric vehicle, a fuel cell electric vehicle, a two-wheeler transportation system, a rail vehicle, a marine vessel, an aircraft, an aerospace system, a defense system, and a medical device.

[0013] In the following detailed description, preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. To the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description and accompanying drawings. Embodiments of the different aspects of the invention can be combined with one another, unless it is specifically mentioned otherwise.

[0014] Here within a range “between X and Y” or “from X to Y” includes the endpoints X and Y.

[0015] “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.

[0016] “D90” as used herein refers to a particle size at 90% of cumulative volume% distribution when measured by laser scattering method. The method of measuring D90 by laser scattering method is described herein below.

[0017] The term "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.

[0018] Here within and unless otherwise noted, the crystallite sizes A and B are determined from a Le Bail refinement using both phases of the X-Ray powder diffraction patterns. The crystallites sizes are calculated from the half-widths of all (hkl) planes of both phases included between 10 and 80° using a copper anticathode. Brief Description of the Figures

[0019] Fig 1. Represents X-ray diffraction spectra of examples and comparative examples.

[0020] Fig 2. Shows Scanning Electron Microscopy (SEM) images of example EX1 at two different magnifications.Detailed Description

[0021] In an embodiment of the positive electrode active material powder of the present disclosure, 0.05 < A / B < 0.35, advantageously 0.05 < A / B < 0.30, more advantageously 0.10 < A / B < 0.25. Too high A / B ratios were found to reduce battery capacity.

[0022] In an embodiment of the positive electrode active material powder of the present disclosure, the sulfur source is selected from the group consisting of cyclic octasulfur (S8) and cyclic S12 allotropes thereof.

[0023] In an embodiment of the positive electrode active material powder of the present disclosure, the carbon source comprises a carbon-based material such as carbon, carbon black, acetylene black and furnace black.

[0024] In an embodiment of the positive electrode active material powder of the present disclosure, comprises iron disulfide in a weight percentage x relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < x < 50wt%, 25wt% < x < 45wt%, 30wt% < x < 40wt%, or 30wt% < x < 35wt%.

[0025] In an embodiment of the positive electrode active material powder of the present disclosure, comprises the sulfur source in a weight percentage y relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < y < 50wt%, 25wt% < y < 45wt%, 30wt% < y < 40wt%, or 30wt% < y < 35wt%.

[0026] In an embodiment of the positive electrode active material powder of the present disclosure, comprises the carbon source in a weight percentage z relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < z < 50wt%, 25wt% < z < 45wt%, 30wt% < z < 40wt%, or 30wt% < z < 35wt%.

[0027] In an embodiment of the positive electrode active material powder of the present disclosure, the weight ratio of iron disulfide, sulfur source and carbon source is about 1:1:1.

[0028] In an embodiment of the positive electrode active material powder of the present disclosure, the lithium-based argyrodite compound comprises Lii2-m-t+(Mm+Y42-)Y2-t2-Xt- where 0 < t < 2, where M is one or more selected from Si, Ge, Sn, P, and As; Y is one or more selected from S, Se, Te, and X is F, Cl, Br, I or a combination of two or more of F, Cl, Br, and I.

[0029] In an embodiment of the positive electrode active material powder of the present disclosure, the lithium-based argyrodite compound comprises Lie-aPSs-aXi+a + b LiX, wherein1) a is about -0.3 to about 0.75,2) b is 0 to about 0.3, and3) X is selected from the group consisting of F, Cl, Br, I and any combination these halogens.

[0030] In an embodiment of the positive electrode active material powder of the present disclosure, the lithium-based argyrodite compound comprises LiePSsX is where X is F, Cl, Br, I or a combination of two or more of F, Cl, Br, and I.

[0031] In an embodiment of the positive electrode active material powder of the present disclosure, the weight ratio of the lithium-based argyrodite compound to the total weight of iron disulfide, sulfur source and carbon source ranges from 0.8: 1.2 to 1.2:0.8, from 0.9: 1.1 to 1.1 :0.9, or is about 1:1.

[0032] In an embodiment of the positive electrode active material powder of the present disclosure, the powder has a particle size distribution (PSD) value D90 of at least 120pm, advantageously at least 140pm, more advantageously of at least 160pm.

[0033] In an embodiment of the positive electrode active material powder of the present disclosure, the powder has a particle size distribution (PSD) value D90 of at most 220pm, advantageously at most 200pm, more advantageously of at most 180pm.

[0034] In an embodiment of the positive electrode active material powder of the present disclosure, A is at least 2 nm or at least 5 nm.

[0035] In an embodiment of the positive electrode active material powder of the present disclosure, A is at most 45 nm, at most 40 nm, at most 35 nm, at most 30 nm, at most 25 nm or at most 20 nm.

[0036] In an embodiment of the positive electrode active material powder of the present disclosure, B is at least 40 nm, at least 40 nm or at least 60 nm.

[0037] In an embodiment of the positive electrode active material powder of the present disclosure, B is at most 90 nm, at most 80 nm, or at most 70 nm.

[0038] In an embodiment of the method of the present disclosure, the first mixture is provided in a ball-milling crucible, in particular comprising balls comprising zirconia, alumina or tungsten carbide.

[0039] In an embodiment of the method of the present disclosure, the milled first mixture and the lithium-based argyrodite compound are combined in a ball-milling crucible, in particular comprising zirconia balls. Advantageously, milling the combined milled first mixture and lithium-based argyrodite is performed in a ball mill.

[0040] In an embodiment of the method of the present disclosure, the sulfur source is selected from the group consisting of cyclic octasulfur (S8) and cyclic S12 allotropes thereof.

[0041] In an embodiment of the method of the present disclosure, herein the carbon source comprises a carbon-based material such as carbon, carbon black, acetylene black and furnace black.

[0042] In an embodiment of the method of the present disclosure, the first mixture comprises iron disulfide in a weight percentage x’ relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < x’ < 50wt%, 25wt% < x’ < 45wt%, 30wt% < x’ < 40wt%, or 30wt% < x’ < 35wt%.

[0043] In an embodiment of the method of the present disclosure, the first mixture comprises the sulfur source in a weight percentage y’ relative to the total weight ofiron disulfide, sulfur source and carbon source of 20wt% < y’ < 50wt%, 25wt% < y’ < 45wt%, 30wt% < y’ < 40wt%, or 30wt% < y’ < 35wt%.

[0044] In an embodiment of the method of the present disclosure, the first mixture comprises the carbon source in a weight percentage z’ relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < z’ < 50wt%, 25wt% < z’ < 45wt%, 30wt% < z’ < 40wt%, or 30wt% < z’ < 35wt%.

[0045] In an embodiment of the method of the present disclosure, in the first mixture, the weight ratio of iron disulfide, sulfur source and carbon source is about 1:1:1.

[0046] In an embodiment of the method of the present disclosure, milling the first mixture is performed at a milling speed ranging from 400 to 6000 rpm.

[0047] In an embodiment of the method of the present disclosure, milling the first mixture is performed for a duration ranging from 60 to 70h.

[0048] In an embodiment of the method of the present disclosure, the lithium-based argyrodite compound comprises Lii2-m-t+(Mm+Y42-)Y2-t2’Xt_or LiePSsX , where 0 < t < 2 and where M is one or more selected from Si, Ge, Sn, P, and As; Y is one or more selected from S, Se, Te, and X is F, Cl, Br, I or a combination of two or more of F, Cl, Br, I.

[0049] In an embodiment of the method of the present disclosure, the milled first mixture and lithium-based argyrodite compound are combined in a weight ratio ranging from 0.8:1.2 to 1.2:0.8, from 0.9:1.1 to 1.1:0.9, or of about 1:1.

[0050] In an embodiment of the method of the present disclosure, milling the combined milled first mixture and lithium-based argyrodite is performed at a milling speed ranging from 340 to 380 rpm.

[0051] In an embodiment of the method of the present disclosure, milling the combined milled first mixture and lithium-based argyrodite is performed for a duration ranging from 12 to 16h.

[0052] In an embodiment of the method of the present disclosure, at least one milling step is performed under an atmosphere comprising an inert gas, in particular under Ar, Ne, Kr, or N2.

[0053] The present disclosure further concerns an all-solid-state secondary battery, comprising:1) a positive electrode layer comprises a positive electrode active material powder according to any embodiment or combination of embodiments of the present disclosure;2) a negative electrode layer; and3) a solid electrolyte layer between the positive electrode layer and the negative electrode layer.

[0054] In an embodiment of the all-solid-state secondary battery of the present disclosure, the negative electrode layer comprises Li metal or a Li alloy.

[0055] In an embodiment of the all-solid-state secondary battery of the present disclosure, the solid electrolyte layer is selected from argyrodite Lii2-m-t+(Mm+Y42-)Y2-t2-Xt- , where M is one or more selected from Si, Ge, Sn, P, As, Y is one or more selected from S, Se, Te, where X is one or more selected from Cl, Br, and I, and where 0 < t < 2, glass ceramic LisPS4 and LiyPsSu, LGPS type electrolyte.Analytical methods

[0056] Scanning Electron Microscopy (SEM) - The morphology of positive electrode active material powders is analyzed by a Scanning Electron Microscopy (SEM) technique. The measurement is performed in a dry room with a -40 dew point using a ZEISS SIGMA 300 under a high vacuum environment of 8x1 O’6Pa at 25 °C. The particles in the image should be well distributed therefore avoiding overlap between particles. This can be achieved by pouring a small amount of powder sample to the adhesive attached on the SEM sample holder and blowing dry air to remove the excess powder.

[0057] Powder X-ray Diffraction (XRD) - XRD patterns are recorded on a Broker D8 Advance X-ray diffractometer in the 10-80 degree 2-theta range in a 0.015 degree scan step. Scan speed is set to 3.0 degrees per minute. The copper target X-ray tube is operated at 40KV and 40mA. The LynxEye XE-T detector is used to capture diffracted X-rays at 3.3 degree opening. The collected XRD patterns comprise KAIpha Cu radiations with typical wavelengths KAIphal =1.5418 A. The incident beam optic setup comprises a 1 -degree divergence slit (DS) and 2.5 degree vertical Soller slit. The diffracted beam optic setup includes an automatic anti-scatter slit (SS), and 2.5degree vertical Seller slit. To prevent fluctuations the temperature is kept near room temperature all the time.

[0058] Particle size distribution (PSD) - The particle size is measured using a Microtrac MRB Granulometer equipped with a SYNC particle analyzer. To improve the dispersion of the positive electrode active material powder examples, sufficient ultrasonic irradiation and stirring is applied, and an appropriate surfactant is introduced. D10, D50, and D90 are defined as the particle size at 10%, 50%, and 90% of the cumulative volume % distribution, respectively.

[0059] Chronoamperometry - Chronoamperometry was used to measure the electronic conductivity of the positive electrode active material powder. A BioLogic Potentiostat was used to do all the measurement. The voltage was set at 20mV for 15 min. The measurement were performed in the same home-made cell than the cycling as described in the next part. 70 mg of materials was pelletized under 250 MPa for 3 min and 250 MPa were applied during the measurements.All solid state battery (SSB) preparation and electrochemical testing

[0060] Negative electrode preparation - For the preparation of negative electrode, lithium foil (diameter 5 mm) is placed centered on the top of indium foil (diameter 7 mm) and pressed to form Li-ln alloy negative electrode.

[0061] Separator - For the preparation of separator which also has a function of the solid electrolyte in a battery, the Li-P-S-CI based solid electrolyte is pelletized with a pressure of 375 MPa in a home-made cell with a diameter of 7 mm.

[0062] Cell assembly - A sulfide solid-state rechargeable battery is assembled in an argon-filled glovebox. The positive electrode active material powder was spread on one side of separator and pressed under 250 MPa and the negative electrode was attached to the other side of the separator under 125 MPa. The loading, i.e. the weight of the coated positive electrode per unit area, was 39 mg / cm2The cell was then put into a pouch cell and a constant pressure of 50 MPa was applied.

[0063] SSB Testing - Each cell is cycled a potentiostat from BioLogic. The initial discharge capacity (DQ1 ) are measured in constant current mode (CC) at C rate of 20 C and 10 C in voltage range 2.4 V to 0.9 V (lnLi / Li+). DQ20 and DQ50 is the discharge capacity at the 20th and 50th cycle, respectively.Examples and comparative examples

[0064] Example 1 - An electrode active material labelled as EX1 is prepared according to the following steps:1) 2 g of iron disulfide (purchased from LTS Research Laboratories Inc.), 2 g of octasulfur, and 2 g of super P carbon black were mixed and placed in a 250 ml ball-milling crucible filled with 60 g of zirconia ball (5 mm diameter).2) The mixture from step 1) was subjected to ball milling in a planetary ball mill at 500 rpm for 64 h with 5 min of performance and 15 min of rest to obtain a fine powder. The ball milling process was performed in a glove box filled with inert gas.3) 1 g of fine powder from step 2) was mixed with a 1 g of LiePSsCI and then placed in a 50 ml ball-milling crucible filled with 6 g of zirconia ball (10 mm diameter).4) The mixture from step 3) was subjected to ball milling in a planetary ball mill at 360 rpm for 15.5 h with 15 min of performance and 5 min of rest to obtain a second fine powder. The ball milling process was performed in a glove box filled with inert gas.5) The second fine powder from step 4) was sieved with a 50 pm sieve to obtain the positive electrode active material powder EX1.

[0065] The prepared EX1 are analyzed using Scanning Electron Microscopy (SEM), X- ray Diffraction (XRD), Particle Size Distribution (PSD), Chronoamperometry (CA), and SSB cell test to evaluate their characteristics, morphology, and electrochemical performance.

[0066] Example 2 - An electrode active material labelled as EX2 is prepared according to the following steps:1) 2 g of iron disulfide (purchased from Sigma-Aldrich), 2 g of octasulfur, and 2 g of super P carbon black were mixed and placed in a 250 ml ball-milling crucible filled with 60 g of zirconia balls (5 mm diameter).2) The mixture from step 1) was subjected to ball milling in a planetary ball mill at 500 rpm for 64 h with 5 min of performance and 15 min of rest to obtain a finepowder. The ball milling process was performed in a glove box filled with inert gas.3) 1 g of fine powder from step 2) was mixed with a 1 g of LiePSsCI and then placed in a 50 ml ball-milling crucible filled with 6 g of zirconia ball (10 mm diameter).4) The mixture from step 3) was subjected to ball milling in a planetary ball mill at 360 rpm for 15.5 h with 15 min of performance and 5 min of rest to obtain a second fine powder. The ball milling process was performed in a glove box filled with inert gas.5) The second fine powder from step 4) was sieved with a 50 pm sieve to obtain the positive electrode active material powder EX2.

[0067] The prepared EX2 are analyzed using Scanning Electron Microscopy (SEM), X- ray Diffraction (XRD), Particle Size Distribution (PSD), Chronoamperometry (CA), and SSB cell test to evaluate their characteristics, morphology, and electrochemical performance.

[0068] Comparative Example 1 - An electrode active material labelled as CEX1 is prepared according to the following steps:1) 7 g of iron disulfide (purchased from Sigma-Aldrich) were placed in a 50 ml ball-milling crucible filed with 70 g of zirconia balls (5 mm diameter) and the powder was subjected to ball-milling in a planetary ball mill at 500 rpm for 64 h with 5 min of performance and 15 min of rest to obtain a milled-iron disulfide. The ball milling process was performed in a glove box filled with inert gas.2) 2 g of milled-iron disulfide from step 1), 2 g of octasulfur, and 2 g of super P carbon black were mixed and placed in a 250 ml ball-milling crucible filled with 60 g of zirconia ball (5 mm diameter).3) The mixture from step 2) was subjected to ball milling in a planetary ball mill at 500 rpm for 64 h with 5 min of performance and 15 min of rest to obtain a fine powder. The ball milling process was performed in a glove box filled with inert gas.4) 1 g of fine powder from step 3) was mixed with a 1 g of LiePSsCI and then placed in a 50 ml ball-milling crucible filled with 6 g of zirconia ball (10 mm diameter).5) The mixture from step 4) was subjected to ball milling in a planetary ball mill at 360 rpm for 15.5 h with 15 min of performance and 5 min of rest to obtain a second fine powder. The ball milling process was performed in a glove box filled with inert gas.6) The second fine powder from step 5) was sieved with a 50 pm sieve to obtain the positive electrode active material powder CEX1.

[0069] The prepared CEX1 are analyzed using Scanning Electron Microscopy (SEM), X- ray Diffraction (XRD), Particle Size Distribution (PSD), Chronoamperometry (CA), and SSB cell test to evaluate their characteristics, morphology, and electrochemical performance.

[0070] Comparative Example 2 - An electrode active material labelled as CEX2 is prepared according to the following steps:1) 7 g of iron disulfide (purchased from Sigma-Aldrich) were placed in a 50 ml ball-milling crucible filed with 70 g of zirconia balls (5 mm diameter) and the powder was subjected to ball-milling in a planetary ball mill at 500 rpm for 64 h with 5 min of performance and 15 min of rest to obtain a milled-iron disulfide. The ball milling process was performed in a glove box filled with inert gas.2) 2 g of milled-iron disulfide from step 1), 2 g of octasulfur, and 2 g of vapor- grown carbon fiber were mixed and placed in a 250 ml ball-milling crucible filled with 60 g of zirconia ball (5 mm diameter).3) The mixture from step 2) was subjected to ball milling in a planetary ball mill at 500 rpm for 64 h with 5 min of performance and 15 min of rest to obtain a fine powder. The ball milling process was performed in a glove box filled with inert gas.4) 1 g of fine powder from step 3) was mixed with a 1 g of LiePSsCI and then placed in a 50 ml ball-milling crucible filled with 6 g of zirconia ball (10 mm diameter).5) The mixture from step 4) was subjected to ball milling in a planetary ball mill at 360 rpm for 15.5 h with 15 min of performance and 5 min of rest to obtain a second fine powder. The ball milling process was performed in a glove box filled with inert gas.6) The second fine powder from step 5) was sieved with a 50 pm sieve to obtain the positive electrode active material powder CEX2.

[0071] The prepared CEX2 are analyzed using Scanning Electron Microscopy (SEM), X- ray Diffraction (XRD), Particle Size Distribution (PSD), Chronoamperometry (CA), and SSB cell test to evaluate their characteristics, morphology, and electrochemical performance.

[0072] Comparative Example 3 - An electrode active material labelled as CEX3 is prepared according to the following steps:1) 5 g of iron disulfide (purchased from Sigma-Aldrich) were placed in a 50 ml ball-milling crucible filed with 70 g of zirconia balls (5 mm diameter) and cyclohexane solution (purchased from Sigma-Aldrich) was added to the crucible until the balls and powder were covered. The wet powder was subjected to ballmilling in a planetary ball mill at 400 rpm for 16 h with 5 min of performance and 15 min of rest to obtain a milled-iron disulfide. The ball milling process was performed in a glove box filled with inert gas.2) 2 g of wet milled-iron disulfide from step 1 ), 2 g of octasulfur, and 2 g of super P carbon black were mixed and placed in a 250 ml ball-milling crucible filled with 60 g of zirconia ball (5 mm diameter).3) The mixture from step 2) was subjected to ball milling in a planetary ball mill at 500 rpm for 64 h with 5 min of performance and 15 min of rest to obtain a fine powder. The ball milling process was performed in a glove box filled with inert gas.4) 1 g of fine powder from step 3) was mixed with a 1 g of LiePSsCI and then placed in a 50 ml ball-milling crucible filled with 6 g of zirconia ball (10 mm diameter).5) The mixture from step 4) was subjected to ball milling in a planetary ball mill at 360 rpm for 15.5 h with 15 min of performance and 5 min of rest to obtain asecond fine powder. The ball milling process was performed in a glove box filled with inert gas.6) The second fine powder from step 5) was sieved with a 50 pm sieve to obtain the positive electrode active material powder CEX3.

[0073] The prepared CEX3 are analyzed using Scanning Electron Microscopy (SEM), X- ray Diffraction (XRD), Particle Size Distribution (PSD), Chronoamperometry (CA), and SSB cell test to evaluate their characteristics, morphology, and electrochemical performance.

[0074] Table 1. Crystallite size ratio of the examples and comparative examples raw materials.

[0075] Table 2. Particle size from PSD measurement of the positive electrode active material powders

[0076] Table 3. Electrochemical properties of the positive electrode active material powders

[0077] Figure 1 presents the XRD patterns of FeS2-Li6PSsCI composites alongside those of FeS2 and LiePSsCI. The absence of an S peak in each FeS2-LiePSsCI composite pattern indicates successful amorphization of sulfur. The prominent peak around 20° arises from the airtight dome used for XRD analysis. For the FeS2-LiePSsCI composites, the reduced intensity and broadening of FeS2 and LiePSsCI peaks after ball milling suggest partial amorphization of both precursors. The degree of amorphization varies with the composite preparation, as reflected by differences in peak intensities and widths across the XRD patterns. Table 1 presents the crystallite sizes of FeS2 and LiePSsCI, and the ratio of LiePSsCI to FeS2 crystallite sizes is also provided. The lowest ratio, which is below 0.25, is observed for composites synthesized with pristine FeS2 (EX1 and EX2). Intermediate ratios, ranging from 0.4 to 0.7, are found in FeS2-LiePSsCI composites prepared using Super P and milled FeS2 as precursors (CEX1 and CEX3). Finally, a higher ratio (>1) is observed for FeS2-LiePSsCI, likely resulting from the inclusion of VGCF as a conductive additive.

[0078] Based on Table 2, the examples and comparative examples contain secondary particles having D50 ranging from 10 to 40 pm. The largest D90 values are recorded for composites synthesized with pristine FeS2 powders (EX1 and EX2), while composites with milled FeS2 (CEX1, CEX2, and CEX3) display smaller D90 values. Additionally, the choice of carbon additive has minimal impact on particle size, as CEX1 (with Super P) and CEX2 (with VGCF) show comparable D10, D50, and D90 values.

[0079] Table 3 summarizes the electrochemical performance of five FeS2-LiePSsCI composites, each with a loading of 39 mg / cm2. EX1 and EX2 demonstrate strongcapacity retention after 50 cycles, underscoring their stability and suitability as positive electrode active material powders. Composites CEX1, CEX2 and CEX3, having too low A / B ratios, exhibit rapid capacity loss.

[0080] Notably, in EX1 and EX2 large specific capacity even when a relatively large amount of a positive electrode active material powder is loaded.

Claims

Claims

1. A positive electrode active material powder comprising iron disulfide, a sulfur source, a carbon source, and a lithium based argyrodite compound; wherein the sulfur source is selected from cyclic octasulfur (S8) and cyclic S12 allotropes thereof; wherein the carbon source is selected from carbon, carbon black, acetylene black and furnace black, wherein the positive electrode active material has a ratio A / B between 0.05 and 0.40, wherein A is the crystallite size of the lithium based argyrodite compound, and B is the crystallite size of iron disulfide, as determined by X-ray diffraction analysis and Le Bail refinement.

2. Positive electrode active material powder according to claim 1 , wherein 0.05 < A / B < 0.35.

3. Positive electrode active material powder according to claim 1 or claim 2, wherein 0.05 < A / B < 0.30.

4. Positive electrode active material powder according to any of the claims 1 to 3, wherein the sulfur source is octasulfur.

5. Positive electrode active material powder according to any of the claims 1 to 4, wherein the carbon source is carbon black.

6. Positive electrode active material powder according to any of the claims 1 to 5, wherein iron disulfide is in a weight percentage x relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < x < 50wt%, and / or the sulfur source is in a weight percentage y relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < y < 50wt%, and / or the carbon source is in a weight percentage z relative to the total weight of iron disulfide, sulfur source and carbon source of 20wt% < z < 50wt%.

7. Positive electrode active material powder according to any of the claims 1 to 6, wherein the lithium-based argyrodite compound comprises Lie-aPSs-aXi+a + b LiX, wherein a is about -0.3 to about 0.75, b is 0 to about 0.3, and X is selected from the group consisting of F, Cl, Br, I and any combination thereof.

8. Positive electrode active material powder according to any of the claims 1 to 7, wherein the lithium-based argyrodite compound comprises LiePSsCI.

9. Positive electrode active material powder according to any of the claims 1 to 8, wherein the powder has a particle size distribution D90 of at least 120pm

10. Positive electrode active material powder according to any of the claims 1 to 9, wherein A is at least 2 nm or at least 5 nm.

11. Method for preparing a positive electrode active material powder according to any of the claims 1 to 10, comprising the following steps:1) providing a first mixture comprising iron disulfide, a sulfur source, and a carbon source;2) milling the first mixture to obtain a milled first mixture;3) combining the milled first mixture with a lithium-based argyrodite compound to obtain a combined milled first mixture;4) milling the combined milled first mixture and lithium-based argyrodite so as to obtain a second milled mixture;5) optionally, sieving the second milled mixture;to obtain a positive electrode active material powder.

12. Method according to claim 11, wherein the milling step 4) is performed in a ball mill.

13. Method according to claim 11 or 12, wherein the milled first mixture and lithium-based argyrodite compound are combined in a weight ratio ranging from 0.8: 1.2 to 1.2:0.8, from 0.9: 1.1 to 1.1:0.9, or of about 1:1.

14. All-solid-state secondary battery, comprising:1) a positive electrode layer comprising a positive electrode active material powder according to any one of claims 1 to 10;2) a negative electrode layer; and3) a solid electrolyte layer between the positive electrode layer and the negative electrode layer,

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

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