Lithium ion conducting composite material comprising at least one polymer and lithium ion conducting particles, and method for producing a lithium ion conductor from said composite material

Abstract

To provide a lithium ion conductive composite material having practically higher particle filling degree than one conventionally capable of being used, and containing at least one polymer and lithium ion conductive particle.SOLUTION: The problem is solved by a lithium ion conductive composite material containing at least one polymer and lithium ion conducive particle, the particle has spheroidicity Ψ of at least 0.7, the composite material contains at least 20 vol.% of particle when polydispersity index PI of particle diameter distribution is less than 0.7, or the composite material contains at least 30 vol.% of particles when the polydispersity index PI of particle diameter distribution is in a range of 0.7 to less than 1.2, or the composite material contains at least 40 vol.% of particle when the polydispersity index PI of particle diameter distribution is over 1.2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lithium ion conducting composite material comprising at least one polymer and lithium ion conducting particles, and to a method for producing a lithium ion conductor from said composite material. [Background technology]

[0002] In recent years, lithium-ion batteries and lithium batteries have become increasingly important, especially for electronic components or in the field of electric vehicles, due in particular to their high energy density, lack of memory effect, and very slow voltage drop. Lithium-ion batteries and lithium batteries generally represent a family of rechargeable battery types (also referred to as secondary battery types) that are used as storage media for the above-mentioned fields.

[0003] Lithium-ion or lithium batteries basically consist of three main structural units: an anode (negative electrode), a cathode (positive electrode), and a non-aqueous electrolyte located between the electrodes, which allows the movement of lithium ions during operation (charging or discharging). In lithium-ion batteries, the anode is usually based on graphite, into which lithium ions are inserted during charging and from which they are extracted during discharging. In contrast, in lithium batteries, elemental lithium is used as the anode.

[0004] Currently, commercially available lithium-ion batteries mainly use electrolytes in which lithium salts are dissolved in organic solvents, but these batteries have the disadvantage that they can self-destruct and, in extreme cases, catch fire when used improperly or overloaded.

[0005] To solve these problems, so-called lithium solid-state batteries have been investigated in recent years, in particular, in which the organic-based liquid electrolyte matrix is ​​replaced with a solid that also conducts lithium ions. In this case, the solid electrolyte can generally be used in various positions in the battery system. On the one hand, the use of a pure solid electrolyte as a separator, introduced between the electrodes to protect against undesired short circuits and thereby ensure the functionality of the entire system, is conceivable. For this purpose, the solid electrolyte can be incorporated into the battery either as a layer on one or both electrodes or as a self-supporting membrane. On the other hand, it is conceivable to blend it with the electrode active material. In this case, the solid electrolyte provides transport of the relevant charge carriers (lithium ions and electrons) to or from the electrode material and the conductive electrode, depending on whether the battery is being discharged or charged.

[0006] In principle, solid electrolytes can be polymer electrolytes or polyelectrolytes. In the former case, similar to liquid electrolytes, a lithium-based supporting salt is dissolved in a solid polymer matrix (often using polyethylene oxide for this purpose). The second type is a polymeric polyfunctional lithium salt. Similar to liquid-based electrolytes, both polymer electrolytes and polyelectrolytes usually have insufficient chemical and electrochemical stability with respect to elemental lithium and are therefore rather unsuitable for use in lithium batteries. However, as an alternative, purely inorganic solid ionic conductors can also be considered as a replacement for conventionally used organic-based liquid electrolytes. In terms of lithium ion conductivity, oxide-based (e.g., lithium-conducting mixed oxides with a garnet structure), phosphate-based, and sulfide-based lithium ion-conducting materials are discussed as being particularly promising. Certain embodiments of these materials have sufficient chemical and electrochemical stability with respect to elemental lithium. Therefore, they are suitable for use in lithium batteries. However, this does not apply to other representatives of the purely inorganic solid ionic conductor class. Therefore, in any case, the suitability of a corresponding material as a solid electrolyte in a lithium battery must be verified individually in each individual case. A third embodiment for lithium-conducting solids is the so-called hybrid electrolyte, which is a composite material in which particles made of an inorganic lithium-ion conducting material are incorporated into a lithium-conducting polymer matrix consisting of a polymer electrolyte or polyelectrolyte. Certain hybrid electrolyte embodiments also exhibit sufficient chemical and electrochemical stability with respect to elemental lithium and are capable of being used in lithium batteries.

[0007] Among purely inorganic lithium-ion conducting solid electrolytes, the sulfide compositions Li-SP and LiS-PS-P0 are sometimes produced by grinding the starting materials under protective gas followed by temperature treatment (also usually under protective gas). The production of Li-PS glass ceramics is described in U.S. Patent Application Publication Nos. 2005 / 0107239 (US20050107239 A1), 2009 / 159839 (US2009159839 A), and JP 2008-120666. LiS-PS-P0 can be produced either via a grinding process or via melting, as described by A. Hayashi et al., Journal of Non-Crystalline Solids 355 (2009) 1919-1923. Glass ceramics in the system Li2S-B2S3-Li4SiO4 can also be produced via the melting route and subsequent quenching, but this process step must be carried out in the absence of air (see US2009011339 A and Y. Seino et al., Solid State Ionics 177 (2006) 2601-2603). Attainable lithium ion conductivities are 2 × 10 at room temperature. -4 ~6×10 -3 S / cm. It should be noted that in the case of sulfide lithium-ion conducting solid electrolytes, production under protective gas and sometimes laborious grinding can make their production expensive. Furthermore, handling and storage under protective gas or at least in an anhydrous environment can often be disadvantageous for the production of lithium batteries in certain environments.

[0008] In contrast, solid lithium ion conductors based on oxides are characterized by easier, and thus more convenient, manufacturing and higher chemical stability. Phosphate-based compositions having a crystal layer, which have a crystal structure similar to NASICON (sodium superionic conductor), are mainly known. Generally, this is a glass ceramic, in which case the starting glass is first melted and then hot-formed (e.g., cast). The starting glass is ceramified in a second stage either directly (“bulk glass ceramic”) or as a powder (“sintered glass ceramic”). During ceramification, controlled crystallization can be carried out according to appropriately selected temperature and time, which enables adjustment of the structure of the glass ceramic optimized for lithium ion conductivity. Thereby, an improvement in conductivity on the order of more than 10 times can be achieved. The document of U.S. Patent Application Publication No. 2003 / 0205467 (US20030205467 A1) describes the production of a glass ceramic having a main crystal phase Li (1+x) (Al,Ga) x Ti (2-x) (PO4)3(0 < x ≦ 0.8). After crystallization, an ionic conductivity of 0.6 to 1.5×10 -3 S / cm was achieved. The starting glass is very sensitive to crystallization and must be quenched on a metal plate to avoid uncontrolled crystallization. This limits the possibility of shaping and the control of the structure in the glass ceramic.

[0009] In the documents of U.S. Patent No. 6030909 (US6030909) and U.S. Patent No. 6485622 (US6485622), GeO2 and ZrO2 are further introduced into the glass ceramic. GeO2 broadens the vitrification region and reduces the crystallization tendency. However, in practice, this beneficial effect is limited by the high raw material price of germanium. In contrast, ZrO2 brings about enhanced crystallization. The starting glasses cited in these documents have a tendency towards uncontrolled crystallization, and usually, quenching must be carried out to obtain a suitable starting glass.

[0010] Xu et al., in Electrochem. Commun., 6 (2004) 1233-1237 or Materials Letters, 58 (2004), 3428-3431, also reported 5.7 × 10 -4 ~6.8×10 -4 They describe Li2O-Cr2O3-P2O5 glass ceramics with high conductivities of 100 S / cm. However, these starting glasses also have to be rapidly cooled due to their strong tendency to crystallize.

[0011] Glass ceramics containing Fe2O3 have also been described (K. Nagamine et al., Solid State Ionics, 179 (2008) 508-515), where 3 × 10 -6 Ion conductivity of 1000 S / cm was found. However, the use of iron (or other polyvalent elements) often leads to the appearance of electronic conductivity, which must be avoided in solid electrolytes. Therefore, according to JP2008047412A, this glass ceramic is preferably used as a cathode material, since electronic conductivity is desired here to facilitate cathode contact.

[0012] US Patent Application Publication No. 2014 / 0057162 (US2014 / 0057162 A1) describes a lithium ion conductive phosphate-based glass ceramic having a densitometric value of at least 5×10 -7The glass-ceramic has an ionic conductivity of 0.15 S / cm, and because the starting glass has sufficient crystallization stability, it can be produced by casting from the melt without the need for rapid cooling. Furthermore, both the glass-ceramic and the starting glass have sufficient chemical stability in air, allowing for storage. This is made possible by the corresponding phosphate-based glass-ceramic containing Ta2O5 and / or Nb2O5. Ta2O5 and Nb2O5 can improve the crystallization stability of the glass because they can also be incorporated into the crystalline phase, which can positively influence ionic conductivity by increasing the proportion of crystalline phase.

[0013] Oxide-based inorganic solid ion conductor materials that are particularly important due to their high lithium ion conductivity are lithium-containing mixed oxides with a garnet structure, such as those described in DE 102007030604 A1. In this regard, materials containing zirconium and lanthanum have particularly good conductivity, which in their simplest form have the formula Li7La3Zr2O 12 The compound or compounds derived therefrom are often referred to as LLZO for short. The garnet occurs in two modifications: tetragonal and cubic. The cubic modification of LLZO is particularly important for lithium solid-state batteries, as it has high lithium ion conductivity. Further investigation of LLZO has shown that the formation of the cubic modification of LLZO can be stabilized, especially by adding additional doping metals, such as aluminum. In the context of this application, undoped or doped lithium lanthanum zirconium oxide or compounds derived therefrom will generally be referred to as LLZO. LLZO has proven chemically and electrochemically stable against elemental lithium, which is used as the anode in lithium batteries, and therefore has great potential for use as an electrolyte in corresponding systems.

[0014] Many methods for producing LLZO are described in the literature. For example, the so-called solid-state method for producing LLZO is known, as described, for example, in US Patent Application Publication No. 2010 / 047696 (US 2010 / 047696 A1) or US Patent Application Publication No. 2010 / 0203383 (US 2010 / 0203383 A1). In the method described in the last-mentioned document, the starting material, optionally pre-dried at temperatures up to 900 °C for 12 hours, is ground in a ball mill, then heated at temperatures between 900 and 1125 °C for 12 hours, and the resulting product is ground again in a ball mill. The resulting powder is then isostatically pressed and calcined again for 36 hours at a temperature in the range of 1230 °C. As an alternative to the solid-state method, attempts have been made to prepare precursors using sol-gel methods, which can then be further processed to the desired crystalline mixed oxides with a garnet structure. Such a method, sometimes referred to as the Pechini method, is described, for example, in Y. Shimonishi et al., Solid State Ionics 183 (2011) 48-53. In this case, lithium, lanthanum, and zirconium are used in the form of their nitrates and heated together in a mixture of water, citric acid, and ethylene glycol, forming a black solid that must then be heat-treated again at 350 ° C for 5 hours, after which an intermediate product in powder form is obtained, which can then be further processed into the desired final product. DE102013101145 A1 and DE102013224045 A1 describe the preparation of LLZO crystallizing into cubic or tetragonal crystals via a sol-gel process, sometimes starting from an alcohol and sometimes from an aqueous sol. A further sol-gel method for producing amorphous LLZO is known from US 2011 / 0053001 A1.

[0015] German Patent Application Publication No. 102014116378 (DE102014116378 A1) discloses the production of LLZO in the form of a glass ceramic. Glass ceramic is understood to mean a material produced by melting techniques, as described above for phosphate-based solid lithium ion conductors, and subsequently converted into a glass ceramic. The glass ceramic contains an amorphous fraction of at least 5% by weight. The amorphous fraction has a positive effect on the conductivity. However, the amorphous fraction should be no more than 40% by weight, preferably no more than 30% by weight, since otherwise the overall conductivity would be reduced. A further advantage of producing it as a glass ceramic is that its structure can be directly influenced by controlled crystallization, which can further positively influence the conductivity. The glass ceramic described in German Patent Application Publication No. 102014116378 advantageously has a crystallinity of at least 5×10 -5 S / cm, preferably at least 1 × 10 -4 S / cm. In some cases, the ionic conductivity can be significantly higher. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] US Patent Application Publication No. 2005 / 0107239 [Patent Document 2] US Patent Application Publication No. 2009 / 159839 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-120666 [Patent Document 4] US Patent Application Publication No. 2009 / 011339 [Patent Document 5] US Patent Application Publication No. 2003 / 0205467 [Patent Document 6] U.S. Patent No. 6,030,909 [Patent Document 7] U.S. Patent No. 6,485,622 [Patent Document 8] Japanese Patent Application Laid-Open No. 2008-047412 [Patent Document 9] US Patent Application Publication No. 2014 / 0057162 [Patent Document 10] German Patent Application Publication No. 102007030604 [Patent Document 11] US Patent Application Publication No. 2010 / 047696 [Patent Document 12] US Patent Application Publication No. 2010 / 0203383 [Patent Document 13] German Patent Application Publication No. 102013101145 [Patent Document 14] German Patent Application Publication No. 102013224045 [Patent Document 15] US Patent Application Publication No. 2011 / 0053001 [Patent Document 16] German Patent Application Publication No. 102014116378 [Non-patent literature]

[0017] [Non-Patent Document 1] A. Hayashi et al., Journal of Non-Crystalline Solids 355(2009)1919-1923 [Non-patent document 2] Y.Seino et al., Solid State Ionics 177(2006)2601-2603 [Non-patent document 3] Xu et.al., Electrochem. Commun., 6(2004)1233-1237 [Non-patent document 4] Xu et.al., Materials Letters, 58(2004),3428-3431 [Non-Patent Document 5] K. Nagamine et al., Solid State Ionics, 179(2008)508-515 [Non-patent document 6] Y.Shimonishi et al, Solid State Ionics 183(2011)48-53 Summary of the Invention [Problem to be solved by the invention]

[0018] The present invention aims to provide a lithium ion conducting composite material comprising at least one polymer and lithium ion conducting particles, which composite material should have a substantially higher particle loading than previously achievable. It should be easily and economically manufacturable. It is also an object of the present invention to find a method for producing a lithium ion conductor from said composite material. [Means for solving the problem]

[0019] The object of the present invention is to provide a lithium ion conductive composite material comprising at least one polymer and lithium ion conductive particles, the particles have a sphericity Ψ of at least 0.7, and the composite material contains at least 20% by volume of the particles, the particle size distribution of which has a polydispersity index PI of less than 0.7; or the composite material contains at least 30% by volume of the particles with a particle size distribution polydispersity index PI in the range of 0.7 to less than 1.2; or The composite material contains at least 40% by volume of the particles with a particle size distribution polydispersity index PI greater than 1.2. The lithium ion conductive composite material solves this problem.

[0020] Here, the sphericity Ψ is a parameter that indicates how spherical a particle is. According to the definition by H. Wadell, the sphericity Ψ of a particle is calculated as the ratio of the surface area of ​​a sphere of equal volume to the surface area of ​​the particle:

number

[0021] Typical sphericity values ​​Ψ for different types of particles are: Sphere: 1.0 Droplets, bubbles, round particles: 0.7-1.0 Angular grain: 0.45~0.6 Acicular particles: 0.2~0.45 Platelet: 0.06~0.16 Particles with very rough surfaces: 10 -8 ~10 -4

[0022] In the context of the present invention, a high sphericity Ψ is achieved when Ψ has a value of at least 0.7.

[0023] In the context of the present invention, the polydispersity index PI of a particle size distribution is the d 90 Value and d 10 It is understood as the base 10 logarithm of the quotient from the value: PI=log(d 90 / d 10 )

[0024] Generally, higher particle packing can be achieved in composites and composite precursors when the particle size distribution is broader, ie, when the polydispersity index PI has a higher value.

[0025] d value for determining PI, especially d 90 value and d 10 Value definitions The particles of a powder are generally distinguished by their equivalent spherical diameter, which is measured independently of their sphericity Ψ, and are divided into selected classes according to their size. To describe the particle size distribution, the proportion of each particle class present in the powder is measured.

[0026] Here, different types of quantities are used: if particles are counted, the type of quantity is number, whereas in the case of a metric it is mass, and in the case of a uniform density ρ it is volume, as well as from length, projection and surface.

[0027] A distinction is made between: Quantity type: Index r: Number 0 Length 1 area 2 Volume (mass) 3

[0028] The conventional quantitative means for describing particle size distribution in powders is the cumulative distribution Q r The index r indicates the type of quantity according to the table above.

[0029] Cumulative distribution function Q r (d) denotes the normalized quantity of all particles with an equivalent diameter less than or equal to d. Below we explicitly define the cumulative distribution of the two most conventional quantity types: · Number of particles (r=0) N i is the diameter under consideration, d i Let d be the number of all particles examined that have a diameter d such that:

number

number

[0030] In relation to the present invention, i The value is Q3(d i ) is understood to be the equivalent diameter value whose cumulative distribution function takes the following values: d 10 : Q3(d 10) = 10%, that is, 10 mass% of the particles are d 10 having a diameter of d 50 : Q3(d 50 ) = 50%, that is, 50% of the particles are d 50 having a diameter of d 90 : Q3(d 90 ) = 90%, that is, 90% of the particles are d 90 having a diameter of d 99 : Q3(d 99 ) = 99%, that is, 99% of the particles are d 99 having a diameter of d 100 : Q3(d 100 ) = 100%, that is, 100% of the particles are d 100 It has the following diameters:

[0031] In the context of this application, the term polydispersity index can be understood synonymously with the term polydispersity index.

[0032] The composite material according to the invention can be a) in one embodiment used directly as a lithium ion conductor, or b) in a further embodiment used as an intermediate product for further processing into a lithium ion conductor.

[0033] It has been surprisingly found that particles having a sphericity Ψ of at least 0.7 can be used to achieve substantially higher particle packing. Thus, composite materials according to the invention are available that contain at least 20% by volume of particles having a polydispersity index PI of the particle size distribution less than 0.7, or at least 30% by volume of particles having a polydispersity index PI of the particle size distribution greater than or equal to 0.7 and less than 1.2, or at least 40% by volume of particles having a polydispersity index PI of 1.2 or greater.

[0034] In a particularly preferred embodiment of the present invention, the particles have a sphericity Ψ of at least 0.8, particularly preferably at least 0.9.

[0035] In a further embodiment, the composite material preferably contains at least 25 vol. % of the particles, and particularly preferably at least 30 vol. % of the particles, when the polydispersity index PI of the particle size distribution has a value of less than 0.7, preferably contains at least 35 vol. % of the particles, and particularly preferably contains at least 40 vol. % of the particles, when the polydispersity index PI of the particle size distribution has a value of 0.7 or more and less than 1.2, or preferably contains at least 45 vol. % of the particles, and particularly preferably contains at least 50 vol. % of the particles, when the polydispersity index PI of the particle size distribution has a value of 1.2 or more.

[0036] Preferably, the polymer comprises at least one of the following compounds: Polyethylene oxide Polyethylene oxide derivatives Polyvinyl butyral.

[0037] Additionally, the use of the following polymers is contemplated: polyacrylonitrile, polyester, polypropylene oxide, ethylene oxide / propylene oxide copolymers, polyethylene oxide crosslinked with trifunctional urethane, poly(bis(methoxy-ethoxy-ethoxide))phosphazene (MEEP), triol-type polyethylene oxide crosslinked with difunctional urethane, poly((oligo)oxyethylene) methacrylate-co-alkali metal methacrylate, polymethyl methacrylate (PMMA), polymethylacrylonitrile (PMAN), polysiloxanes and their copolymers and derivatives, polyvinylidene fluoride or polyvinylidene chloride and their copolymers and derivatives, poly(chlorotrifluoroethylene), poly(ethylene-chlorotrifluoroethylene), poly(fluorinated ethylene-propylene), acrylate-based polymers, condensed or crosslinked combinations thereof, and / or physical mixtures thereof.

[0038] The polymer may contain at least one lithium ion conducting compound, in particular lithium bistrifluoromethanesulfonimidate, as lithium ion conducting compound.

[0039] Further usable supporting salts include LiAsF6, LiClO4, LiSbF6, LiPtCl6, LiAlCl4, LiGaCl4, LiSCN, LiAlO4, LiCF3CF2SO3, Li(CF3)SO3(LiTf), LiC(SO2CF3)3, phosphate-based lithium salts, preferably LiPF6, LiPF3(CF3)3(LiFAP) and LiPF4(C2O4)(LiTFOB), borate-based lithium salts, preferably LiBF4, LiB(C2O4)2(LiBOB), LiBF2(C2O4)(LiDFOB), LiB(C2O4)(C3O4)(LiMOB), Li(C2F5BF3)(LiFAB) and Li2B 12 F 12 (LiDFB), and / or lithium salts of sulfonyl imides, preferably LiN(FSO2)2 (LiFSI), LiN(SO2CF3)2 (LiTFSI) and / or LiN(SO2C2F5)2 (LiBETI), come into consideration.

[0040] In addition to the above polymer electrolytes, polyelectrolytes can also be used selectively. + as counterions, such as polystyrene sulfonate (PSS), or polymerized ionic liquids based on imidazolium, pyridinium, phosphonium, or guanidium, which have a discrete number of chemically bound ionic groups and are therefore inherently lithium ion conductive.

[0041] The lithium ion conducting particles are preferably made from at least one lithium ion conducting compound, in particular at least one of the following lithium ion conducting compounds: Lithium lanthanum zirconate (LLZO) Lithium Aluminum Titanium Phosphate (LATP) Compounds with a garnet-type crystal structure, in particular those having the empirical formula Li 7+x-y M x II M 3-x III M 2-y IV M y V O 12 [In the formula, M II is a divalent cation, M III is a trivalent cation, M IV is a tetravalent cation, M V is a pentavalent cation, where: Advantageously, 0≦x<3, more preferably 0≦x≦2, 0≦y<2, and particularly preferably 0≦y≦1. Materials having a garnet-type crystal structure having the formula: Compounds with the same crystal structure as NaSICon, especially those with the empirical formula Li 1+x-y M 5+ y M 3+ x M 4+ 2-x-y (PO4)3 [In the formula, x and y are in the range of 0 to 1 and (1+xy)>1; and M is a +3, +4, or +5 cation. or a compound derived therefrom It consists of:

[0042] The particles preferably have an average particle size in the range of 0.02 μm to 100 μm. Two ranges, 0.2 μm to 2 μm and 5 μm to 70 μm, are particularly preferred. One of the two ranges, 0.2 μm to 2 μm or 5 μm to 70 μm, is also particularly preferred.

[0043] In a further preferred embodiment, in the case of the lithium ion conductive composite material, the interfacial resistance for lithium ion conductivity between the polymer and the particles is reduced due to the surface modification of the particles, and thus the lithium ion conductivity is higher than in the case of a comparable composite material in which the interfacial resistance between the polymer and the particles is not reduced.

[0044] Preferably, the particles are produced using at least one of the following methods: Spray calcination (especially using pulse reactor technology) Filamentation from molten salts · Dropletization Glass sphere manufacturing.

[0045] Regardless of whether the purely inorganic solid lithium-ion conductor is oxide-, phosphate-, or sulfide-based, all of the production methods described so far in the prior art have in common that the lithium-ion conductive material obtained in each step is either monolithic or at least undefined coarse-grained, and must be further refined, usually by a milling process, to be brought into its final application form as a powder with a defined particle size and particle size distribution. In many cases, the particle size to be achieved is in the μm or sub-μm range. This only makes further processing possible. This includes, in particular, the incorporation of the hybrid electrolyte into a polymer, polymer electrolyte, or polyelectrolyte for final production. On the other hand, this involves compacting or incorporation into a ceramic slurry and further processing in a molding step (e.g., tape casting) to form a ceramic green body, which is then sintered to finally convert it into a ceramic component made of the purely inorganic solid ion conductor.

[0046] By means of a comminution process, such as the milling process described above, it is not actually possible to produce spherical powder particles, but rather fragmented particles with corners and edges are formed, which therefore have a sphericity significantly lower than 0.7.

[0047] Non-spherical particles of one and the same material are significantly more difficult to process in many applications than their spherical counterparts with the same particle size and particle size distribution. This is particularly true when incorporated into thermoplastic matrices (e.g., when producing hybrid electrolytes) and liquid matrices (e.g., when producing ceramic slurries). For the same volumetric filling level, the viscosity of a particle-filled formulation with non-spherical particles is significantly higher than that of spherical particles made of the same material, even with comparable particle sizes or particle size distributions. Conversely, in the case of spherical embodiments, corresponding formulations can have significantly higher filling levels than non-spherical embodiments. This is due to the increased internal friction of formulations filled with non-spherical particles, which tend to get stuck when they pass each other within the formulation due to the influence of external shear forces. In contrast, spherical particles can pass each other better.

[0048] When using spherical particles, it is actually very important that the filled formulation achieves a significantly higher volumetric filling degree under comparable conditions. For example, in hybrid electrolytes, the increased incorporation of inorganic solid electrolytes consisting of spherical particles can achieve significantly better lithium-ion conductivity, since the lithium-ion conductivity of the inorganic component is usually higher than that of the polymer-based matrix. When spherical particles are used in the formulation, the ceramic slurry remains pourable even at a relatively high filling degree. The resulting green body after drying of the solvent still has a significantly lower porosity, which results in significantly less shrinkage during the final sintering step. Artifacts often associated with sintering shrinkage (e.g., crack formation) can thus be significantly reduced by their effect.

[0049] Therefore, in view of the prior art, there is a need for a lithium ion conducting solid electrolyte material in powder form that is composed of microscale or submicroscale particles and has a high degree of sphericity Ψ.

[0050] For example, the following methods are available: Glass sphere production: A route for producing particles from lithium-ion conductive materials takes advantage of the fact that these materials can also be produced via the glass-ceramic route. For this purpose, in a conventional melting process, ideally a crystal-free green glass is first melted and then ceramized during a subsequent heating step to convert it into the actual glass-ceramic. In principle, the glass melt used in the first process step can be subjected to a conventional thermoforming process used for producing glass spheres upon cooling. The following method approaches are conceivable: In the method disclosed in U.S. Pat. No. 3,499,745, a molten glass jet is impinged on a striking wheel, and if a sufficiently large force is generated, the jet breaks into partial strands, so-called filaments. Subsequently, the jet passes first through a heated zone, a cooling zone, and finally into a collection zone. After the filaments are formed, the tendency for surface tension to minimize acts, causing the filaments to become round. According to EP 1135343 B1, sufficient sphericity is reached after a relaxation time T, which can be described by the formula T = (d × μ) / σ, has elapsed from the time of filament formation. In this formula, d is the diameter of the sphere formed, μ is the viscosity of the filament, and σ is the surface tension of the filament during the relaxation time. Instead of a striking wheel, a rotor can also be used, as described in U.S. Pat. No. 3,495,961. Another known method for producing glass spheres involves expanding a combustion gas stream through a molten glass stream to break the glass into individual particles. Such a method is disclosed in U.S. Pat. No. 3,279,905. Alternatively, glass particles with relatively low sphericity can be (partially) remelted and rounded by being brought into a flame, as described, for example, in German Patent Application DD 282675 A5.

[0051] Filamentation of molten salt: Analogous to the formation of spherical droplets from a molten glass jet due to the aforementioned filament formation and subsequent relaxation effect that reduces surface energy, this can also be achieved from a jet of material originating from molten salt. To achieve this, a similar technical approach can be followed, noting that the viscosity of molten glass can differ significantly from that of molten salt, depending on the temperature selected in each case. The droplet-like material must first be converted into a preceramic intermediate stage, often porous but shape-stable except for isotropic shrinkage, by passing it through a hotter zone, and then subsequently converted into a solid lithium-ion conductor, either at this stage or in another additional subsequent heating step. Ideally, this results in densely sintered spheres of solid lithium-ion conductor material.

[0052] Spray calcination (using pulse reactor technology): When using a pulse reactor, as disclosed in DE 10111938 A1, DE 102006027133 A1, DE 102006039462 A1 or EP 1927394 A1, a gaseous or liquid mixture in the form of a solution, suspension or dispersion containing all components for producing a lithium-ion conductive material is introduced, in the latter case by fine atomization, into a pulsed hot gas stream, which in this case is itself generated in the hot gas generator of the reactor by burning natural gas or hydrogen together with ambient air. The prevailing temperature is 500-1500°C, depending on the location of the spray introduction point. An intermediate product is formed in the pulsed hot gas stream, which is then converted to its final form by further thermal post-treatment in the same or another reactor. In the former case, the reactor may be equipped with an additional fuel supply, which follows the pulsed hot gas stream to the spray introduction point.

[0053] Dropletization method: In the dropletization method, starting from an aqueous or solvent-based salt solution or sol as precursor for the lithium-ion conducting material or from a nanoparticle solution of the lithium-ion conducting material, this is converted into droplets via a suitable nozzle device. After formation, the droplets are optionally dried directly in a suitable process gas stream, as described, for example, in U.S. Patent No. 4,043,507 (US4,043,507) or U.S. Patent No. 5,500,162 (US5,500,162), or first stimulated to further agglomerate by bringing them into a suitable liquid medium, followed by aging, washing, and drying, as disclosed in U.S. Patent No. 5,484,559 (US5,484,559), U.S. Patent No. 6,197,073 (US6,197,073), U.S. Patent Application Publication No. 2004 / 0007789 (US2004 / 0007789 A1), or International Publication No. 2015 / 014930 A1. The spherical porous green bodies thus produced are then consolidated in a subsequent sintering step into lithium-ion conductive ceramic bodies with high sphericity.

[0054] Furthermore, this object is achieved by a method for producing a lithium-ion conductor, in which the composite material according to the invention is sintered, in particular under the action of elevated temperature and / or elevated pressure.

[0055] Both the lithium ion conductive composite material according to the present invention and the lithium ion conductor produced from the lithium ion conductive composite material can be used as lithium ion conductive parts or components of such parts depending on the needs and scope of application.

[0056] Furthermore, formulations for producing composite precursors for hybrid electrolytes or ceramic slurries for producing sintered purely inorganic solid lithium-ion conductor components are described in which the viscosity of particle-filled formulations at the same volumetric filling level is significantly higher when non-spherical particles are used than when particles with high sphericity Ψ produced according to the present invention are used, provided that the particle size or particle size distribution in both cases is the same.

[0057] Furthermore, formulations for producing composite precursors for hybrid electrolytes or ceramic slurries for producing sintered, purely inorganic, solid lithium-ion conductor components are described, in which the corresponding formulations can have a significantly higher degree of filling in the spherical embodiment than in the non-spherical embodiment, without essentially changing the viscosity, again under the condition that the particle size and particle size distribution are essentially the same in both cases.

[0058] According to the present invention, the lithium ion conductive material produced in the form of spherical particles with particle sizes in the μm or subμm range can be incorporated as a filler into polymer electrolytes or polyelectrolytes, with the corresponding composites generally referred to as hybrid electrolytes. For this purpose, it can be optionally pressed into a compact using a suitable tool or incorporated into a ceramic slurry (with or without the addition of a binder) and subjected to a suitable molding process (e.g., tape casting), and in both cases sintered at a temperature that forms a purely inorganic, ion-conducting compact. Both application forms of the hybrid electrolyte and the purely inorganic, ceramic, solid ion conductor can be used as solid electrolytes in next-generation rechargeable lithium-ion or lithium batteries, such as solid-state lithium batteries (all-solid-state batteries (ASSB)) or lithium-air batteries. On the one hand, it can be used as a separator, i.e., inserted between electrodes, where it protects the electrodes from undesired short circuits and thereby ensures the functionality of the entire system. For this purpose, the corresponding composites can be incorporated into the battery as solid electrolytes, either as layers on one or both electrodes or as free-standing films. Alternatively, they can be mixed with the electrode active materials, either by incorporating them into the hybrid electrolyte formulation in the case of hybrid electrolytes or by co-sintering with them in the case of purely inorganic ceramic electrolytes. In this case, the solid electrolyte provides for the transport of the relevant charge carriers (lithium ions and electrons) to and from the electrode material and the conductive electrode, depending on whether the battery is being discharged or charged. [Example]

[0059] Example of production of lithium ion conductive particles having a high sphericity Ψ of at least 0.7 from lithium ion conductive materials 1. Preparation of spherical LAGP particles (A) Direct molding from green glass melt The starting glass for the final lithium-ion conducting phosphate-based glass ceramic with the composition 5.7% by weight LiO, 6.1% by weight AlO, 37.4% by weight GeO and 50.8% by weight PO was melted in a flow crucible at a temperature of 1650°C.

[0060] The glass melt was maintained at 1600 °C in the selected melting device. It was then ejected through a 2 mm diameter nozzle attached to the bottom of the crucible. The resulting glass jet was dropped onto an 8 mm thick striking wheel with 53 teeth and an outer diameter of 135 mm, rotating around its axis at 5000 rpm. In this way, the glass stream was filamented into individual partial strands and accelerated at an inclination angle of 20–30° measured relative to the horizontal. It then passed through a 3 m long tube furnace configured in a curved shape to mimic the trajectory of the filamentary glass stream and heated to 1550 °C with two gas burners. The longitudinally formed filaments were deformed into spheres due to the tendency of surface energy to minimize. After exiting the tube furnace, the glass spheres were further cooled in air until they achieved sufficient morphological stability and were finally collected in a collection vessel.

[0061] The cooled, largely X-ray amorphous green glass spheres produced by the above-mentioned thermoforming process were nucleated for 2–4 h in the temperature range of 500–600 °C, followed by further temperature treatment at a maximum temperature of 850 °C with a holding time of 12 h, to ceramize and thus convert into the final lithium-ion conducting glass-ceramic.

[0062] (B) Forming by rounding non-spherical green glass particles The starting glass for the final lithium-ion conducting phosphate-based glass-ceramic with the composition 5.7 wt.% LiO, 6.1 wt.% AlO, 37.4 wt.% GeO and 50.8 wt.% PO was melted in a flow crucible at a temperature of 1650 °C.

[0063] The glass melt was held at a temperature of 1600°C in the selected melter. It exited through a 2 mm diameter nozzle attached to the bottom of the crucible and flowed into a gap between two counter-rotating water-cooled rollers, where it was quenched to form a green glass ribbon. The green glass ribbon was mechanically singulated into small pieces with a hammer.

[0064] The glass fragments are roughly crushed by preliminary crushing in a ball mill, and then the particle size d 100 The powder fraction having a particle size of <100 μm was sieved. In a further subsequent step, this sieved green glass powder was dry-milled in an opposed jet mill. 10 = 0.9 μm, d 50 = 5 μm, d 90 = 13 μm and d 99 The particles were further subdivided to a particle size distribution of 18 μm.

[0065] By bringing the powder into an oxyhydrogen gas flame, the glass particles are re-melted and rounded due to the tendency of the surface energy to be minimized. After emerging from the flame, the particles are cooled and placed in a collection vessel.

[0066] The cooled, largely X-ray amorphous green glass spheres produced by the above-mentioned thermoforming process were nucleated for 2–4 h in the temperature range of 500–600 °C, followed by further temperature treatment at a maximum temperature of 850 °C with a holding time of 12 h, to ceramize and thus convert into the final lithium-ion conducting glass-ceramic.

[0067] 2. Filamentation of molten salt In the first step, a zirconium-containing precursor powder was prepared as follows: 5.0 kg (50.0 mol) of acetylacetone was added dropwise to 23.4 kg (50.0 mol) of zirconium-n-propoxide (70% solution) in a round-bottom flask while stirring. The resulting reaction mixture was stirred for 60 minutes at room temperature. 2.7 kg (150.0 mol) of distilled water was then added thereto for hydrolysis. After a reaction time of approximately 1 hour, the resulting prehydrolyzate was completely dried in a rotary evaporator. A sample of the resulting powder was then heated (900°C / 5 hours) to measure the oxide content.

[0068] 1.77 kg (5.0 mol) of ZrO equivalent of the zirconium-containing precursor powder (oxide content: 35% by mass) produced in the previous step was added to a ball mill together with 2.5 kg (7.5 mol) of lanthanum acetate sesquihydrate, 1.95 kg (19.2 mol) of lithium acetate dihydrate, and 0.15 kg (0.61 mol) of aluminum chloride hexahydrate, where they were milled for 4 hours to produce a powder mixture as homogeneous as possible. 40 mm diameter AlO balls were used as milling balls for this purpose.

[0069] After sieving, the powder mixture was added to an Al2O3 flow crucible, where it was heated to 300°C, just above the melting point of anhydrous lithium acetate (280-285°C). Molten salt was formed and poured through a 2 mm diameter nozzle attached to the bottom of the crucible. The resulting molten salt jet was dropped onto an 8 mm thick striking wheel with 53 teeth and an outer diameter of 135 mm, rotating around its axis at 5000 rpm. The molten salt jet thus filamented into individual strands, accelerating at an inclination angle of 20-30° relative to the horizontal. It then passed through a 3 m long tube furnace configured in a curved shape that mimicked the trajectory of the filamentary molten salt jet. The furnace was electrically heated to maintain a moderate temperature of 300-320°C in the inlet region, further maintaining the molten salt. The initially elongated filaments transformed into spheres while still liquid due to the tendency of surface energy to minimize. In the subsequent region, the temperature was selected to be significantly higher, reaching approximately 900°C. This constituted the first stage of calcining the liquid spheres, forming intermediate porous preceramic particles. After exiting the tube furnace, they were further cooled by air flow and ultimately collected in a collection vessel.

[0070] The porous preceramic particles were consolidated into spheres of the final lithium-ion conducting LLZO material in a further calcination step at 1050°C in a furnace with a holding time of 7-8 hours.

[0071] 3. Preparation of spherical LLZO particles by spray calcination using a pulse reactor method 2.3 kg (4.7 mol) of zirconium acetylacetonate was dissolved in at least 10.0 kg (556 mol) of distilled water in a suitable reaction vessel. 2.4 kg (7 mol) of lanthanum acetate sesquihydrate was dissolved in 10 kg (556 mol) of distilled water in a further reaction vessel. 1.8 kg (18 mol) of lithium acetate dihydrate and 0.14 kg (0.58 mol) of aluminum chloride hexahydrate were dissolved in 5.0 kg (278 mol) of distilled water in a third reaction vessel. After the components were completely dissolved, the solutions were combined and the resulting reaction mixture was stirred at room temperature for 12 hours.

[0072] The solution is conveyed into a pulse reactor with a volumetric flow rate of 3 kg / h using a peristaltic pump, where it is finely sprayed into the reactor through a 1.8 mm titanium nozzle and heat-treated there, with the combustion chamber temperature maintained at 1030°C and the resonance tube temperature at 1136°C. The ratio of the amount of combustion air to the amount of fuel (natural gas) is 10:1 (air:gas).

[0073] The powder is loaded into a square corundum crucible and placed in a box furnace, where the material is brought to a temperature of 1050°C in an air atmosphere to completely consolidate the spherical fine particles of LLZO.

[0074] 4. Fabrication of spherical LLZO particles by the dropletization method First, the LLZO material is melted in a so-called skull crucible, as described, for example, in DE 19939782 C1. A water-cooled crucible is used for this purpose, creating a colder protective layer around the material to be melted during melting. Therefore, the crucible material does not melt during the melting process. Energy is introduced into the melt by high-frequency coupling via an induction coil surrounding the melt. A prerequisite for this is sufficient conductivity of the melt, which, in the case of lithium garnet melts, is a high lithium content. Lithium vapor is generated during the melting process, which can easily be compensated for by excess lithium. For this reason, a lithium excess of 1.1 to 2 times is typically used.

[0075] The raw materials were mixed according to the following composition and charged into an open-top skull crucible: 14.65% by weight Li2O, 56.37% by weight La2O3, 21.32% by weight ZrO2, and 7.66% by weight Nb2O5. To achieve a certain minimum conductivity, the mixture first had to be preheated. For this purpose, burner heating was used. After reaching the coupling temperature, further heating and homogenization of the melt was achieved by high-frequency coupling via an induction coil. To improve the homogenization of the melt, it was stirred with a water-cooled stirrer.

[0076] Materials produced by this route can in principle be converted into glass-ceramic materials with a predominant garnet-type crystalline phase either by direct solidification from the melt or by rapid quenching followed by a subsequent temperature treatment (ceramization). In the examples described here, the direct rapid quenching approach was chosen.

[0077] In this case, the material is obtained as a monolithic block and subjected to various coarse comminution steps, for example by processing with hammers and chisels in a first stage, the resulting fragments being comminuted in a jaw crusher in a second stage, and the resulting coarse powder is further pre-comminuted in a planetary mill and subsequently sieved in a third stage to obtain a particle size d 100 This powder was converted into a powder with a particle size of <100 μm in a further subsequent step by underwater grinding carried out in an attritor. 10 = 0.14 μm, d 50 = 0.42 μm, d 90 = 1.87 μm and d 99 The LLZO was further reduced to a particle size distribution of 2.92 μm. The solids content of the LLZO in the milling slurry used was approximately 30%. To stabilize the particles, a dispersant (Dolapix CE 64 or Dolapix A88, Zschimmer & Schwarz GmbH & Co. KG) was added to the LLZO before milling, which proved to be quite workable at a rate of 1.0% based on the LLZO content in the suspension.

[0078] For further processing, the solids content of the milled slurry was increased to a content of 60% by partially evaporating the water in a rotary evaporator in order to obtain a suitable mix ratio in terms of viscosity.

[0079] Subsequently, ammonium alginate was added as a binder in an amount of 1.0%.

[0080] From the slurry, shape-stable green bodies of 0.3 to 2.5 mm in size were obtained by immersing and reacting the slurry in a solution of aluminum lactate or an inorganic or organic acid through a nozzle and / or cannula using the dropletization method.

[0081] Subsequently, sintered spheres were formed from this by a sintering process, which was carried out in an air atmosphere at a temperature of 1150°C under standard pressure.

[0082] Example for the preparation of a formulation for a lithium ion conducting composite material, filled with at least 20% by volume of lithium ion conducting particles when the polydispersity index PI of the particle size distribution is less than 0.7, or at least 30% by volume of corresponding particles when the polydispersity index PI of the particle size distribution is greater than 0.7 and less than 1.2, or at least 40% by volume of corresponding particles when the polydispersity index PI of the particle size distribution is greater than 1.2: 1. Preparation of a composite material according to the present invention (preparation of a hybrid electrolyte membrane based on polyethylene oxide (PEO) / lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) polymer electrolyte filled with LLZO particles) Molar mass 4 x 10 6 1.4 g of polyethylene oxide (PEO, Dow Chemical) with a molecular weight of 1.0001 g / mol was dried in vacuum for 48 hours at 50° C. The polymer was found to consist of particles with a sphericity of 0.92 and a particle size distribution of d 10 = 1.22 μm, d 50 = 2.77 μm, d 90 = 5.85 μm, d 998.5 g of lithium lanthanum zirconium oxide powder with a particle size distribution of 9.01 μm was added. The polydispersity index of the particle size distribution according to the invention is PI=0.681. The mixture was then vigorously ground in a mortar. The powder was then subjected to a mortar pre-heating at 120° C. for 24 hours in a vacuum (10° C.). The powder had a purity of more than 99%, suitable for battery applications. -7 The mixture was mixed with 0.6 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 3M) dried under 100 bar. All components were vigorously mixed in a mortar until a homogeneous paste was formed. This resulted in a PEO / LiTFSI polymer electrolyte matrix with a lithium ion:ethylene oxide monomer unit ratio (Li:EO) of 1:15, in which 50% by volume of inorganic solid lithium ion conductor was embedded. The hybrid electrolyte thus prepared was vacuum-packed into a pouch and then heat-treated overnight at 100 °C, followed by pressing at 100 °C under a pressure of 50 kN (50–750 kg / cm). 2 The composite membrane was hot pressed (Servitec Polystat 200 T-Press) to obtain a composite membrane with a thickness of approximately 100 μm.

[0083] The same procedure yielded the following particle size distribution: 10 = 0.44 μm, d 50 = 1.24 μm, d 90 = 3.50 μm, d 99 Hybrid electrolyte membranes were produced using LLZO powder consisting of non-spherical particles (Ψ=0.48) with a particle size distribution of 6.94 μm. The polydispersity index of the particle size distribution was PI=0.900 in accordance with the present invention. However, in this case, only 4.6 g of LLZO powder was effectively incorporated into the PEO / LiTFSI polymer electrolyte matrix, meaning that hybrid electrolytes could only be produced with a maximum volume content of 29 vol.%.

[0084] 2. Production of the lithium ion conductor according to the invention from the composite material according to the invention (production of a purely inorganic sintered solid electrolyte membrane using a tape casting method based on a casting slurry filled with LATP particles) 11.4 g of polyvinyl butyral (PVB) with a molecular weight of 35,000 g / mol (containing, in addition to vinyl butyral units, 1.7% by weight of vinyl acetate and 18.9% by weight of vinyl alcohol units) was dissolved in 68.4 g of a solvent mixture consisting of ethanol:toluene (4:6). The viscosity of the solution was 200-450 mPa·s. 5.7 g of dioctyl phthalate, which acts as a plasticizer, was added to the mixture. Finally, the mixture was dissolved in a dissolver to form particles with a sphericity of 0.94 and a particle size distribution of the following value: d 10 = 0.81 μm, d 50 = 2.23 μm, d 90 = 5.17 μm, d 99 200 g of lithium aluminum titanium phosphate (LATP) glass ceramic powder with a particle size distribution of 8.46 μm was introduced and dispersed. The polydispersity index of the particle size distribution in this case was 0.805 according to the invention. The resulting casting material had a viscosity of 4000-5000 mPa·s. The glass ceramic powder content was approximately 43% by volume.

[0085] The homogeneous material thus produced was subsequently degassed by vacuum technology. The degassed material was fed to a conventional tape casting process in a film stretching device and thus cast into a tape approximately 0.3 mm thick (measured after drying). The green tape thus produced was then cut into individual pieces according to the desired shape.

[0086] The individualized tape pieces were finally sintered at 1000°C for 4 hours to form densified LATP membranes, with a shrinkage of approximately 9%.

[0087] The same procedure yielded a particle size distribution with the following values: d 10 = 0.68 μm, d 50 = 1.74 μm, d 90 = 3.86 μm, d 99Purely inorganic solid lithium-ion conductor membranes were fabricated using LATP powder consisting of non-spherical particles (Ψ = 0.46) with a diameter of 7.21 μm. The polydispersity index of the particle size distribution was PI = 0.754 according to the present invention. However, in this case, only 90 g of LATP powder could be effectively incorporated into the binder solution consisting of PVB, dioctyl phthalate, and ethanol:toluene; thus, tape-casting slurries could only be produced with a volume content of up to 28 vol.% without significantly exceeding the target viscosity of 4000-5000 mPa·s. Due to the significantly reduced solid content, shrinkage during sintering was approximately 15%.

Claims

1. 1. A lithium ion conducting composite material comprising at least one polymer and lithium ion conducting particles, the particles have a sphericity Ψ of at least 0.7, and The composite material contains at least 20% by volume of the particles with a particle size distribution polydispersity index PI greater than 0 and less than 0.7; and The polydispersity index PI is calculated by PI=log(d 90 / d 10 ); The lithium ion conductive composite material.

2. The polymer may comprise the following compound: polyethylene oxide, - polyethylene oxide derivatives, ・Polyvinyl butyral The lithium ion conductive composite material according to claim 1, characterized in that it comprises at least one of the following:

3. 3. A lithium ion conducting composite material according to claim 1, characterized in that the polymer contains at least one lithium ion conducting compound.

4. the particles comprising a lithium ion conducting compound: lithium lanthanum zirconate (LLZO), Lithium aluminum titanium phosphate (LATP), - Compounds having a garnet-type crystal structure, A compound having the same crystal structure as NaSICon The lithium ion conductive composite material according to any one of claims 1 to 3, characterized in that it comprises at least one of the following:

5. 5. The lithium ion conductive composite material according to claim 1, wherein the particles have an average particle size of 0.02 μm to 100 μm.

6. 6. The lithium ion conductive composite material according to claim 1, wherein the interfacial resistance for lithium ion conductivity between the polymer and the particles is reduced due to surface modification of the particles, so that the lithium ion conductivity is higher than that of a comparable composite material in which the interfacial resistance between the polymer and the particles is not reduced.

7. 7. A lithium ion conducting composite material according to any one of claims 1 to 6, characterized in that the particles are produced by means of spray calcination.

8. 8. A method for producing a lithium ion conducting composite material according to any one of claims 1 to 7, characterized in that the particles are produced using spray calcination or filamentation or dropletization from molten salts or glass sphere production.

9. 8. A method for producing a lithium ion conductor, characterized in that the composite material according to any one of claims 1 to 7 is sintered under the action of elevated temperature and / or elevated pressure.

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