Particulate electrode material with a coating of an inorganic-organic hybrid polymer and method for its production

Abstract

Coated particulate electrode material, comprising a particulate electrode material selected from the group consisting of lithium intercalating and lithium deintercalating substances, which has a coating of an ion-conducting, inorganic-organic hybrid polymer, wherein the hybrid polymer coating has a layer thickness in the range of 1 to 500 nm, characterized in that the inorganic-organic hybrid polymer contains an inorganic oxide framework consisting of ion-conducting Si-O-Li bonds.

Description

[0001] According to the invention, a particulate electrode material is provided which has a particle coating. The coating makes it possible to stabilize the crystal structure of the electrode material, counteract undesirable reactions between electrode and electrolyte materials, and thus improve electrode materials in terms of safety, durability, and high-voltage capability. Furthermore, a method for coating particulate electrode material is provided, with which the coated electrode material according to the invention can be produced. Finally, uses of the electrode material according to the invention are demonstrated.

[0002] The materials used so far were either metal oxides and metal fluorides such as Al2O3, ZrO2, AlF3, ZnO, etc. (US 2011 / 0 076 556 A1, US 2011 / 0 111 298 A1) or polymers such as PDDA.

[0003] While these materials provide chemical and electrochemical stabilization of the coated active material, this improvement is associated with increased resistance. This, in turn, adversely affects the energy and power density of the batteries. The poor ionic conductivity of the coating materials is primarily responsible for this increased resistance.

[0004] DE 10 2009 036 945 A1 discloses particles suitable as electrode material for the negative electrode of a battery operating according to the nickel-metal hydride battery principle. WO 2011 / 132 065 A1 discloses a composite material containing a positive electrode active material with a transition metal and a reaction suppressor with a polyanion structure, wherein the reaction suppressor covers a surface of the positive electrode active material. DE 199 46 066 A1 discloses polymer-coated lithium mixed oxide particles for improving the properties of electrochemical cells. Oskam et al. (Oskam, G.; Searson, PC; Jow, TR: Sol-Gel Synthesis of Carbon-Silica Gel Electrodes for Lithium Intercalation. In: Electrochemical and Solid-State Letters, Vol. 2 (12), 1999, 610-612) disclose a silica-based inorganic-organic gel that can be used as a binder for lithium-ion batteries.EP 1 926 163 A1 discloses a negative active material for a rechargeable lithium battery, comprising a core containing an active material capable of reversible electrochemical oxidation and reduction, and having a coating layer disposed on the surface of the core and containing a net-like structure comprising -OMO-, wherein M is selected from Si, Ti, Zr, Al or combinations thereof, and containing an organic functional group bonded to M as a side chain and selected from the group consisting of alkyl group, haloalkyl group, substituted or unsubstituted aryl group, and combinations thereof.

[0005] The object of the present invention was therefore to provide an electrode material which has a higher conductivity than the prior art.

[0006] The object is achieved by the coated electrode material according to claim 1, the method for coating particulate electrode material according to claim 12 and the use of the coated electrode material according to claim 16.

[0007] According to the invention, a coated particulate electrode material is provided, comprising a particulate electrode material selected from the group consisting of lithium-intercalating and lithium-deintercalating substances, which has a coating of an ion-conductive, inorganic-organic hybrid polymer, wherein the hybrid polymer coating has a layer thickness in the range of 1 to 500 nm, characterized in that the inorganic-organic hybrid polymer contains an inorganic-oxide framework consisting of ion-conductive Si-O-Li bonds.

[0008] According to the invention, the term “particulate” or “particle” refers not only to round bodies, but also, for example, to bodies in the form of flakes, rods, wires and / or fibers.

[0009] The properties of the hybrid polymers can be specifically tailored using various functional groups. This makes it possible to create a coating characterized by high stability, good flexibility, and, in particular, high ionic conductivity.

[0010] The electrode material coatings can therefore achieve conductivity values ​​of ≥ 10 -4 S / cm. The high lithium-ion conductivity of the hydride polymers facilitates ion transport into the electrode material, which has a positive effect on the energy and power density of the coated electrode material.

[0011] The thermal resilience of the hybrid polymers as well as their chemical and electrochemical stability also improve the safety, durability and high-voltage capability of the electrode materials coated with them.

[0012] Another advantage is the weight of a hybrid polymer coating. Hybrid polymer coatings are significantly lighter than previous coatings made of metal oxides or metal fluorides, which has a positive effect on the specific performance parameters of the battery.

[0013] The hybrid polymer coating is a highly elastic material. It is therefore particularly suitable for electrode materials with high volume expansion, such as silicon (expansion: 300% - 400%).

[0014] According to the invention, the inorganic-organic hybrid polymer contains an inorganic-oxide framework consisting of ionically conductive Si-O-Li bonds. This greatly increases the ionic conductivity in the inorganic regions of the polymer. To improve material properties, particularly conductivity, the inorganic-oxide framework can additionally contain elements selected from the group consisting of B, Zr, Al, Ti, Ge, P, As, Mg, Ca, Cr, and W.

[0015] The coated electrode material according to the invention can be characterized in that the hybrid polymer contains a lithium salt. By incorporating a lithium salt into the hybrid polymer network, conductivity can also be achieved in the organic regions of the hydride polymer. This can further increase conductivity.

[0016] According to the invention, the hybrid polymer coating has a layer thickness in the range from 1 to 500 nm, preferably from 1 to 50 nm, particularly preferably from 1 to 20 nm, in particular from 1 to 10 nm.

[0017] The electrode material can be selected from the group consisting of carbons, alloys of Si, Li, Ge, Sn, Al, Sb, etc., Li4Ti5O 12 , Li 4-y A y Ti 5-x M x O 12 (A = Mg, Ca, Al; M = Ge, Fe, Co, Ni, Mn, Cr, Zr, Mo, V, Ta or a combination thereof), Li(Ni,Co,Mn)O2, Li 1+x (M,N) 1-x O2 (M = Mn, Co, Ni or a combination thereof; N = Al, Ti, Fe, Cr, Zr, Mo, V, Ta, Mg, Zn, Ga, B, Ca, Ce, Y, Nb, Sr, Ba, Cd or a combination thereof), (Li,A) x (M,N) z O v-w X w(A = alkali metal, alkaline earth metal, lanthanide or a combination thereof; M = Mn, Co, Ni or a combination thereof; N = Al, Ti, Fe, Cr, Zr, Mo, V, Ta, Mg, Zn, Ga, B, Ca, Ce, Y, Nb, Sr, Ba, Cd or a combination thereof; X = F, Si), LiFePO4, (Li,A)(M,B)PO4 (A or B = alkali metal, alkaline earth metal, lanthanide or a combination thereof; M = Fe, Co, Mn, Ni, Ti, Cu, Zn, Cr or a combination thereof), LiVPO4F, (Li,A)2(M,B)PO4F (A or B = alkali metal, alkaline earth metal, lanthanide or a combination thereof; M = Fe, Co, Mn, Ni, Ti, Cu or a combination thereof), Li3V2PO4, Li(Mn,Ni)2O4, Li 1+x (M,N) 2-x O a (M = Mn; N = Co, Ni, Fe, Al, Ti, Cr, Zr, Mo, V, Ta or a combination thereof) and mixtures or combinations thereof.

[0018] The inorganic-organic hybrid polymer is based on the cohydrolysis and cocondensation of organically substituted silanes with hydrolyzable functionalities. The inorganic framework of the hybrid polymers preferably consists primarily of a Si-O-Si network, into which Li is incorporated according to the invention, creating an inorganic-oxide framework consisting of ion-conductive Si-O-Li bonds. Optionally, additional elements, preferably semimetals or metals selected from the group M = B, Ge, Al, Zr, and Ti, can be incorporated as heteroatoms, thus creating additional Si-OM and MOM bonds. This allows material properties such as conductivity as well as thermal, chemical, and electrochemical stability to be specifically adjusted.

[0019] However, the type of organic modification used also has a significant influence on the material properties. The toughness and flexibility of the hybrid polymer can be influenced, for example, by using unreactive groups that act as network modifiers, such as alkyl, phenyl, (per)fluoroalkyl, (per)fluoroaryl, polyether, isocyanate, or nitrile groups, as well as organic carbonates. Reactive groups that act as network formers, such as vinyl, methacrylic, allyl, styryl, cyanurate, or epoxy groups, can be used to build an additional organic network through polymerization reactions.

[0020] Lithium salts, for example, can be incorporated into this network to achieve ionic conductivity in these areas as well. Covalent bonds exist between the inorganic and organic phases.

[0021] Preferably, the hybrid polymer coating has a lithium ion conductivity in the range of 10 -7 S / cm to 1 S / cm, preferably from 10 -6 S / cm to 5 · 10 -3 S / cm, especially 10 -4 up to 10 -3 S / cm, on.

[0022] In a preferred embodiment, the hybrid polymer coating is elastic and preferably has an E-modulus of 10 kPa to 100 MPa, particularly preferably 10 kPa to 1 MPa.

[0023] In a further preferred embodiment, only temperatures above 300 °C lead to thermal decomposition of the hybrid polymer coating.

[0024] The coated electrode material can be used at potentials up to ≥ 5 V vs Li / Li + be electrochemically stable.

[0025] In addition, the coated electrode material can be characterized by an operating life of 100 to 100,000 cycles.

[0026] The lithium salt is preferably selected from the group consisting of LiC-IO4, LiAlO4, LiAlCl4, LiPF6, LiSiF6, LiBF4, LiBr, LiIl, LiSCN, LiSbF6, LiAsF6, LiTfa, LiDFOB, LiBOB, LiTFSI, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiN(C2FsSO2)2, LiC(CF3SO2)3, LiC(C2F5SO2)3.

[0027] Furthermore, the invention provides a process for producing a coated particulate electrode material according to the invention, in which a) a sol of an organically modified, polysiloxane-containing material is provided and mixed with electrode material selected from the group consisting of lithium-intercalating and lithium-deintercalating substances, and with at least one organic solvent; and b) the organic solvent is separated, producing electrode material with a nanostructured hybrid polymer coating; and c) the electrode material with the nanostructured hydride polymer coating is isolated, dried and cured.

[0028] A sol is a colloidal dispersion in a solvent.

[0029] In step a), at least one lithium salt and / or at least one hardener can be added.

[0030] The organic solvent is preferably selected from the group consisting of organic solvents which dissolve the organically modified, polysiloxane-containing material.

[0031] The method according to the invention can be characterized in that a) is dried at a temperature of 30 to 50 °C for 20 to 40 minutes; and / or b) cured at a temperature of 70 to 150 °C for 0.5 to 5 hours.

[0032] The process according to the invention is used to produce the electrode material according to the invention.

[0033] It is further proposed to use a hybrid polymer coating containing a sol-gel material produced from organically substituted silanes with hydrolyzable functionalities and optionally with lithium salt for coating particulate electrode material.

[0034] Furthermore, the coated electrode material according to the invention can be used in energy storage devices, preferably in rechargeable lithium batteries and / or double-layer capacitors.

[0035] The subject matter of the invention will be explained in more detail with reference to the following example and the following figures, without wishing to restrict it to the specific embodiments shown here. Fig. 1 shows the model structure of an electrode material 1 coated with hybrid polymer 2. Fig. Figure 2 shows the detection of a complete hybrid polymer coating on Li(Ni,Co,Mn)O2 using an ESCA depth profile. Fig. Figure 3 shows a conductivity measurement of a hybrid polymer material containing LiClO4. Fig. Figure 4 shows the force-displacement diagram of an elastic hybrid polymer material (grey: measurement, black: fit of the measurement). Fig. Figure 5 shows the DSC / TG measurements under argon atmosphere of hybrid polymer material with LiClO4 (•) and without LiClO4 (x). Fig. Figure 6 shows the cyclic voltammogram of a hybrid polymer material containing LiClO4 (AE = Pt and GE = Li) Example - Process for producing a hybrid polymer coating on a particulate electrode materialSynthesis of a Li + -conductive hydride polymer (= coating material)

[0036] In a 250 ml flask, 152 g (0.29 mol) of 2-methoxypolyethyleneoxypropyltrimethoxysilane are stirred with 2.634 g of lithium hydroxide (Mixture 1).

[0037] In parallel, 23.6 g (0.1 mol) of 3-glycidyloxypropyltrimethoxysilane and 140 g of diethyl carbonate are weighed into a 100 ml flask, and 2.7 g (0.15 mol) of distilled water are added (Mixture 2). The mixture is stirred.

[0038] After reaching the clear point of mixture 2, the homogeneous mixture 1 is added to it.

[0039] After a few days, the solvent is evaporated at 40 °C and a pressure of 28 mbar. Coating process

[0040] In a 1-liter flask, 30 g of electrode material are weighed under argon. Then, 400 g of dimethyl carbonate and 0.9 g of coating material (optionally with lithium salt or 0.01 g of boron trifluoride ethylamine complex) are added.

[0041] The flask is slowly moved on a rotary evaporator purged with argon. After approximately 30 minutes, evaporation begins at 40 °C, down to a pressure of 12 mbar.

[0042] Finally, the temperature is increased to 80 °C and the mixture is rotated for 1 hour under these conditions.

Claims

[1] Coated particulate electrode material comprising a particulate electrode material selected from the group consisting of lithium-intercalating and lithium-deintercalating substances, which has a coating of an ion-conductive, inorganic-organic hybrid polymer, wherein the hybrid polymer coating has a layer thickness in the range of 1 to 500 nm, characterized by that the inorganic-organic hybrid polymer contains an inorganic-oxide framework consisting of ion-conductive Si-O-Li bonds. [2] Coated electrode material according to claim 1, characterized by that the hybrid polymer coating has a layer thickness in the range from 1 to 50 nm, particularly preferably from 1 to 20 nm, in particular from 1 to 10 nm. [3] Coated electrode material according to one of claims 1 or 2, characterized bythat the electrode material is selected from the group consisting of carbons, alloys of Si, Li, Ge, Sn, Al, Sb, etc., Li4Ti5O 12 , Li 4-y A y Ti 5-x M X O 12 (A = Mg, Ca, Al; M = Ge, Fe, Co, Ni, Mn, Cr, Zr, Mo, V, Ta or a combination thereof), Li(Ni,Co,Mn)O2, Li 1+x (M,N) 1-x O2 (M = Mn, Co, Ni or a combination thereof; N = Al, Ti, Fe, Cr, Zr, Mo, V, Ta, Mg, Zn, Ga, B, Ca, Ce, Y, Nb, Sr, Ba, Cd or a combination thereof), (Li,A) x (M,N) z O v-w X w(A = alkali metal, alkaline earth metal, lanthanide or a combination thereof; M = Mn, Co, Ni or a combination thereof; N = Al, Ti, Fe, Cr, Zr, Mo, V, Ta, Mg, Zn, Ga, B, Ca, Ce, Y, Nb, Sr, Ba, Cd or a combination thereof; X = F, Si), LiFePO4, (Li,A)(M,B)PO4 (A or B = alkali metal, alkaline earth metal, lanthanide or a combination thereof; M = Fe, Co, Mn, Ni, Ti, Cu, Zn, Cr or a combination thereof), LiVPO4F, (Li,A)2(M,B)PO4F (A or B = alkali metal, alkaline earth metal, lanthanide or a combination thereof; M = Fe, Co, Mn, Ni, Ti, Cu or a combination thereof), Li3V2PO4, Li(Mn,Ni)2O4, Li 1+x (M,N) 2-x O a (M = Mn; N = Co, Ni, Fe, Al, Ti, Cr, Zr, Mo, V, Ta or a combination thereof) and mixtures or combinations thereof. [4] Coated particulate electrode material according to one of the preceding claims, characterized bythat the inorganic-oxidic framework additionally contains oxidic heteroatoms selected from the group consisting of B, Zr, Al, Ti, Ge, P, As, Mg, Ca, Cr, W and / or organic substituents (primarily bonded to Si) made of vinyl, alkyl, acrylic, methacrylic, epoxy, PEG, aryl, styryl, (per)fluoroalkyl, (per)fluoroaryl, nitrile, isocyanate or organic carbonates, and / or vinyl, allyl, acrylic, methacrylic, styrene, epoxy or cyanurate functionalities. [5] Coated electrode material according to one of the preceding claims, characterized by that the hybrid polymer contains a lithium salt. [6] Coated electrode material according to one of the preceding claims, characterized by that the lithium salt is selected from the group consisting of LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSiF6, LiBF4, LiBr, LiIl, LiSCN, LiSbF6, LiAsF6, LiTfa, LiDFOB, LiBOB, LiTFSI, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiC(C2F5SO2)3. [7] Coated electrode material according to one of the preceding claims, characterized by that the hybrid polymer coating has a lithium ion conductivity in the range of 10 -7 S / cm to 1 S / cm, preferably from 10 -6 S / cm to 5 · 10 3 S / cm, especially 10 -4 S / cm to 10 -3 S / cm. [8] Coated electrode material according to one of the preceding claims, characterized by that the hybrid polymer coating is elastic and preferably has an E-modulus of 10 kPa to 100 MPa, particularly preferably 10 kPa to 1 MPa. [9] Coated electrode material according to one of the preceding claims, characterized by that the hybrid polymer coating only decomposes thermally at temperatures above 300 °C. [10] Coated electrode material according to one of the preceding claims, characterized by that the coated electrode material at potentials ≥ 5 V vs. Li / Li +is electrochemically stable. [11] Coated electrode material according to one of the preceding claims, characterized by that the coated electrode material has a service life of 100 to 100,000 cycles. [12] A process for producing a coated particulate electrode material according to any one of the preceding claims, in which a) A sol of an organically modified, polysiloxane-containing material is provided and mixed with electrode material selected from the group consisting of lithium-intercalating and lithium-deintercalating substances, and with at least one organic solvent; and b) the organic solvent is separated, producing electrode material with a nanostructured hybrid polymer coating; and c) the electrode material with the nanostructured hydride polymer coating is isolated, dried and cured. [13] Method according to claim 12, characterized by that in step a) at least one lithium salt and / or at least one hardener is additionally added. [14] Method according to one of claims 12 or 13, characterized by that the organic solvent is selected from the group consisting of organic solvents which dissolve the organically modified, polysiloxane-containing material. [15] Method according to one of claims 12 to 14, characterized by , that a) is dried at a temperature of 30 to 50 °C for 20 to 40 minutes; and / or b) cured at a temperature of 70 to 150 °C for 0.5 to 5 hours. [16] Use of the coated electrode material according to one of claims 1 to 11 in energy storage devices, preferably in rechargeable lithium batteries and / or double-layer capacitors.

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