DE102015215088A1 - MOF-silicon-carbon composite anode material - Google Patents

Abstract

The present invention relates to a method for producing a porous silicon composite, in particular silicon-carbon and / or -metal composite, and / or an anode material for a lithium cell and / or lithium battery. In order to provide an improved anode material for, in particular high-energy, lithium cells and / or lithium batteries, for example lithium-ion cells and / or lithium-ion batteries, a metal-organic framework compound (1 ) comprising silicon, pyrolyzed and / or reduced and / or calcined and / or oxidized and / or etched (1000). Moreover, the invention relates to a silicon composite, an anode material and a lithium cell and / or lithium battery.

Description

The present invention relates to a method for producing a porous silicon composite and / or anode material for a lithium cell and / or lithium battery, a silicon composite, an anode material and a lithium cell and / or lithium battery.

State of the art

Silicon is a promising anode material for lithium-ion cells because it can offer very high capacities, for example, of 3670 mAh / g at about 0.4 V versus lithium, and thus about ten times more than conventional graphite, and is also readily available and non-toxic ,

However, silicon has a low electrical conductivity as well as a limited reaction kinetics and lithium ion penetration, and therefore, silicon nanoparticles are conventionally used as the anode material.

In addition, when cyclizing a cell equipped with it, silicon undergoes extreme volume changes, for example up to 300%, which can result in a loss of mechanical integrity and thus a low cycle life of the anode material and the cell equipped therewith.

The publication WO 2012/028989 A1 relates to a process for producing a composite comprising carbon.

Disclosure of the invention

The present invention is a process for producing a porous silicon composite, in particular silicon-carbon and / or -metal composite, for example, silicon-carbon-metal composites, and / or an anode material for a lithium cell and / or Lithium battery, for example for a lithium-ion cell and / or lithium-ion battery.

In particular, in the process, a metal-organic framework compound comprising silicon is pyrolyzed and / or reduced and / or calcined and / or oxidized and / or etched.

A metal-organic framework compound (MOF) can be understood in particular to mean a crystalline, in particular porous, material, in particular an inorganic-organic hybrid material, which comprises metal ions and organic molecules, which are junctions and connecting elements, so-called Linkers between nodes form a one-dimensional, two-dimensional or three-dimensional framework. In this case, in particular individual metal ions, for example transition metal ions and / or metal ions of the second, third and / or fourth main group, in particular of the Periodic Table, and / or metal ion clusters, for example clusters of transition metal ions and / or metal ions of the second, third and / or fourth main group , serve as junctions and organic molecules as connecting elements, also referred to as traditional metal-organic framework (MOF) compounds. However, organic molecules can also serve as junctions and, in particular, individual metal ions, for example transition metal ions and / or metal ions of the second, third and / or fourth main group, and / or metal ion clusters, for example clusters of transition metal ions and / or metal ions of the second, third and / or Fourth main group, serve as connecting elements, which is also referred to as inverted metal-organic framework compound (IMOF). In particular, the nodes and connecting elements can build up a two-dimensional or three-dimensional, in particular three-dimensional, framework. The metal-organic framework compound may in particular be porous, for example microporous and / or mesoporous.

Under pyrolysis, in particular a thermo-chemical cleavage of organic compounds by high temperatures, for example from ≥ 200 ° C to ≤ 1000 ° C, for example from ≥ 500 ° C to ≤ 1000 ° C, and in particular without additionally supplied oxygen, for example, with exclusion of oxygen (anaerobic), in which a bond breaking is forced within large molecules into smaller molecules and in particular elemental carbon remains.

Calcination can be understood in particular to mean heating of a chemical, for example organic, compound to high temperatures, for example from ≥ 500 ° C. to ≦ 1200 ° C., in the presence of air or oxygen.

Etching may, in particular, be understood to mean a chemical removal, for example dissolution, of a chemical, for example organic, compound, by means of an etchant.

From the metal-organic framework compound, a porous silicon composite, in particular silicon-carbon and / or -metal composite, for example silicon-carbon-metal composite, can advantageously be produced, which has a defined adjustable, in particular the structure of the metal -organic framework derived, pore structure and Having pore size distribution and can be used as the anode material for lithium cells and / or lithium batteries, such as lithium-ion cells and / or lithium-ion batteries. Due to the, in particular defined adjustable, pore structure and pore size distribution advantageously an increase in volume of the silicon during cyclization, in particular in a lithium insertion, for example, optimally compensated and thereby improved cycle stability can be achieved. In addition, it is thus also possible to achieve rapid transport of lithium ions, for example by permeating the pores with a liquid electrolyte.

The metal ions of the metal-organic framework compound can advantageously, if appropriate by pyrolysis and / or reduction and / or calcination and / or oxidation, form mechanically stable and electrically conductive regions and thus improve the mechanical stability of the composite and the electrical contacting of the silicon.

The carbon of the organic molecules of the metal-organic framework compound can advantageously be at least partially converted into elemental carbon, for example by pyrolysis and / or reduction and / or calcination and / or oxidation, which likewise form electrically conductive regions and thus improved electrical contacting of the silicon.

However, the carbon of the organic molecules of the metal-organic framework compound may advantageously also be at least partially removed, for example burned out, for example by pyrolysis and / or reduction and / or calcination and / or oxidation, whereby the pore structure and / or pore size distribution are further adjusted can.

By etching, the pore structure and / or pore size distribution can advantageously also be set further.

By virtue of the method, it is advantageously possible to form a silicon composite, in particular mechanically stable, in particular silicon-carbon and / or metal composite, for example silicon-carbon-metal composite, in which silicon, in particular uniformly and / or finely distributed, for example, at the nano level or even even at the atomic level, is integrated into an electrically conductive matrix of carbon and / or metal and thereby enable a good and especially cyclization stable, electrical contacting of the silicon for electron transport and improved reaction kinetics and lithium ion penetration and which also provides sufficient porosity and thereby can compensate for the increase in volume of the silicon during cycling and thus in turn can provide improved cycle stability as well as fast lithium ion transport. In addition, this advantageously makes it possible to make the size of the composite particles variable and, for example, to use large composite particles, for example on a micrometer scale.

Overall, it is thus advantageously possible to provide an improved anode material for, in particular high-energy, lithium cells and / or lithium batteries, for example lithium-ion cells and / or lithium-ion batteries.

In one embodiment, the metal-organic framework compound has nodes and / or connecting elements comprising silicon.

In the context of another, alternative or additional embodiment, a, in particular gaseous, silicon precursor is or is sorbed, for example absorbed and / or adsorbed on the metal-organic framework compound. In this case, the metal-organic framework compound can have nodes and / or connecting elements which comprise at least one metal and / or silicon.

Thus, for example, metal-organic framework compounds of various types, for example metal-organic framework compounds of a first type, whose junctions and / or connecting elements comprise silicon, metal-organic framework compounds of a second type, whose junctions and / or connecting elements comprise at least one metal, for example, at least two metals and / or a metal cluster of at least one metal or of at least two metals, and thereby may optionally be free of silicon, and metal-organic framework compounds of a third type, their nodes and / or connecting elements silicon and at least one metal , For example, at least two metals and / or a metal cluster of at least one metal or at least two metals include. Metal-organic framework compounds of the second and third kind are used, for example, in US Pat Dalton Transactions, 2013, 42, pages 13806-13808 (Organosilicone linkers in metal organic frameworks: the tetrahedral tetrakis (4-tetrazolylphenyl) silane ligand). Metal-organic framework compounds of the second kind are also used, for example, in US Pat Coordination Chemistry Reviews, 2003, 246, p.169-184 , described.

In the case of a metal-organic framework of the first and third kind, the metal organic framework compound to form the silicon composite easily pyrolyzed and / or reduced. In this case, advantageously, the organic part is partially or completely removed, for example, burned, and a porous silicon-carbon composite or silicon composite can be obtained. In the case of a metal-organic framework compound of the third type, in particular a porous silicon-carbon-metal composite or silicon-metal composite can thus be obtained.

In the case of a metal-organic framework compound of the second type, in particular one, for example gaseous, silicon precursor can be sorbed, for example absorbed and / or adsorbed, on the metal-organic framework compound to form the silicon composite.

However, in order to achieve, for example, a higher silicon content of the composite and thus a higher capacity, it may also be advantageous to sorb a, for example gaseous, silicon precursor onto a metal-organic framework compound of the first and third type.

In a further embodiment, the silicon precursor is or are sorbed into pores of the metal-organic framework compound, in particular absorbed and / or adsorbed. Thus, advantageously, increased capacity and improved cycle life can be achieved.

For example, the silicon precursor can be (initially) sorbed, in particular absorbed and / or adsorbed, and the metal-organic framework compound is (then) pyrolyzed and / or calcined and / or calcined and / or oxidized and / or etched with the silicon precursor ,

In a specific embodiment, the silicon precursor is (initially) sorbed, in particular absorbed and / or adsorbed, and the metal-organic framework compound is (are) pyrolyzed or calcined with the silicon precursor.

In a specific embodiment, the metal-organic framework compound has nodes and / or connecting elements which comprise at least one metal and / or silicon, in particular at least one metal, wherein the silicon precursor sorbs (initially) into pores of the metal-organic framework compound , in particular absorbed and / or adsorbed, and the metal-organic framework compound is (then) pyrolyzed or calcined with the silicon precursor. Thus, from a metal-organic framework compound of the second or third type, in particular of the third type, a silicon-metal composite, for example a silicon-carbon-metal composite, can be formed, in which the at least one metal provides an electrically conductive structure, which is provided with the silicon as active material.

Within the scope of a further embodiment, a, in particular gaseous, carbon precursor is or is sorbed, for example absorbed and / or adsorbed on the metal-organic framework compound. Thus, advantageously, a higher carbon content of the composite and thus improved electrical conductivity can be achieved and / or the porosity can be further adjusted and / or a protective layer can be formed.

In this case, the metal-organic framework compound can have nodes and / or connecting elements which comprise at least one metal and / or silicon. For example, the metal-organic framework compound may have nodes and / or interconnecting elements comprising silicon.

For example, the carbon precursor may be (initially) sorbed, in particular absorbed and / or adsorbed, and the metal-organic framework compound (s) pyrolyzed and / or calcined and / or calcined and / or oxidized and / or etched with the carbon precursor ,

Insofar as a metal-organic framework compound of the first or third kind is used, only the carbon precursor (and not a silicon precursor) may optionally be absorbed, for example absorbed and / or adsorbed.

However, to achieve, for example, a higher silicon content and carbon content of the composite, it may also be advantageous to sorb silicon precursor and carbon precursor.

For example, the silicon precursor and the carbon precursor may (initially) be sorbed, in particular absorbed and / or adsorbed, and the metal-organic framework compound then pyrolyzed and / or reduced with the silicon precursor and the carbon precursor and / or or calcined and / or oxidized and / or etched, in particular pyrolyzed or calcined.

The sorbing of the silicon precursor and the carbon precursor can be carried out, for example, simultaneously or sequentially, for example first the silicon precursor and then the carbon precursor or first the carbon precursor and then the silicon precursor. The fact that first the silicon precursor and then the carbon precursor is sorbed can advantageously be the carbon as Protective layer for the silicon of the silicon precursor and the metal-organic compound serve.

In a further embodiment, the carbon precursor is or are sorbed into pores of the metal-organic framework compound, in particular absorbed and / or adsorbed. Thus, advantageously, the mechanical and / or electrical integrity or stability and thus cycle resistance can be further improved.

In a further embodiment, the carbon precursor is (initially) sorbed, in particular absorbed and / or adsorbed, and the metal-organic framework compound is (then) pyrolyzed or calcined with the carbon precursor.

Within the scope of a specific embodiment, the metal-organic framework compound has nodes and / or connecting elements which comprise silicon and / or at least one metal, in particular silicon, wherein the carbon precursor sorbs (initially) into pores of the metal-organic framework compound, in particular absorbed and / or adsorbed, and (then) the metal-organic framework compound is pyrolyzed or calcined with the carbon precursor. Thus, from a metal-organic framework compound of the first or third type, in particular third type, a silicon composite, for example a silicon-carbon composite and / or a silicon-carbon-metal composite, are formed, in which the silicon as Active material is integrated into the structure, optionally wherein the at least one metal improves the electrical conductivity of the structure, and wherein the carbon forms an electrically conductive protective layer.

In a further embodiment, the silicon precursor comprises or is at least one silane, for example monosilane (SiH ₄ ).

In a further embodiment, the carbon precursor comprises or is at least one alkyne, for example acetylene (HC≡CH), and / or at least one alkene, for example ethylene (H ₂ C =CH ₂ ) and / or propylene, and / or at least an alkane, for example methane (CH ₄ ) and / or ethane (C ₂ H ₆ ), and / or carbon monoxide (CO). For example, the carbon precursor may include or be acetylene and / or methane.

In a further embodiment, the metal-organic framework compound comprises nodes comprising at least one metal and connecting elements comprising silicon. In this case, for example, a silane and / or siloxane can be used as a connecting element. For example, the metal-organic framework compound may comprise copper as junctions and a silane, for example tetrakis (4-tetrazolylphenyl) silane, especially tetrahedral, as linking elements. Such a metal-organic framework compound is, for example, in Dalton Transactions, 2013, 42, pages 13806-13808 (Organosilicone linkers in metal organic frameworks: the tetrahedral tetrakis (4-tetrazolylphenyl) silane ligand).

In another embodiment, the metal-organic framework compound comprises nodes comprising silicon, and connecting elements comprising at least one metal. In this case, for example, Si (O-) ₄ can be used as a node.

Within the scope of a further embodiment, the metal-organic framework compound comprises copper and / or Si (O) ₄ , in particular copper, as a junction and / or a silane and / or siloxane, in particular silane, for example tetrakis (especially tetrahedral) (4). Tetrazolylphenyl) silane, as a connecting element.

The metal-organic framework compound or the at least one metal may, for example, at least one transition metal, for example copper (Cu), titanium (Ti), iron (Fe), nickel (Ni) and / or zinc (Zn), and / or at least one metal the second main group, in particular of the Periodic Table, for example magnesium (Mg), and / or at least one metal of the third main group, in particular of the Periodic Table, for example aluminum (Al), and / or at least one metal of the fourth main group, in particular of the Periodic Table, for example tin (Sn), and / or at least one metal of the fifth main group, in particular of the Periodic Table, include or be.

A transition metal may, in particular, be understood as meaning an element which has an atomic number of 21 to 30, 39 to 48, 57 to 80 and 89 to 112 in the periodic table.

In particular, the metal-organic framework compound or the at least one metal can be at least one transition metal, for example copper, titanium, iron, nickel and / or zinc, and / or at least one metal of the second main group, for example magnesium, and / or at least one metal of the third Main group, for example aluminum, and / or at least one metal of the fourth main group, such as tin, include or be.

In a further embodiment, the metal-organic framework compound or the at least one metal comprises or is copper and / or aluminum and / or titanium and / or Iron and / or magnesium and / or zinc and / or nickel and / or tin. In particular, the metal-organic framework compound or the at least one metal may comprise copper.

In particular, the metal-organic framework compound can also be a metal-organic framework compound whose nodes and / or connecting elements have at least two metals and / or a metal cluster of at least one metal or of at least two metals. The at least two metals (likewise) may be selected from the group of transition metals, for example copper (Cu), titanium (Ti), iron (Fe), nickel (Ni) and / or zinc (Zn), and / or metals of second main group, for example magnesium (Mg), and / or metals of the third main group, for example aluminum (Al), and / or metals of the fourth main group, for example tin (Sn), and / or metals of the fifth main group.

Within the scope of an embodiment, the metal-organic framework connection has nodes and / or connection elements which comprise a metal cluster. Thus, advantageously, a particularly high electrical conductivity can be achieved.

Composites prepared by the process may be used in terms of pore size and / or pore size distribution and / or morphology by, for example, transmission electron microscopy (TEM) and / or Scanning Electron Microscopy (SEM) and / or the nature of the art Metal-organic framework compounds using Fourier transform infrared spectroscopy (FTIR) are investigated.

With regard to further technical features and advantages of the method according to the invention, reference is hereby explicitly made to the explanations in connection with the composite according to the invention, the anode material according to the invention and the cell and / or battery according to the invention and to the figures and the description of the figures.

Further objects are a silicon composite, in particular a silicon-carbon and / or metal composite, for example a silicon-carbon-metal composite, and / or an anode material for a lithium cell and / or lithium battery, in particular for a lithium-ion cell and / or lithium-ion battery. The composite or the anode material may in particular be produced by a method according to the invention. The composite or the anode material may in particular be porous.

In particular, the silicon composite may be a silicon-carbon-metal composite comprising silicon and carbon and at least one metal, in particular copper and / or aluminum and / or titanium and / or iron and / or magnesium and / or zinc and / or Nickel and / or tin.

The anode material according to the invention may in particular comprise a silicon composite according to the invention.

With regard to further technical features and advantages of the composite and anode material according to the invention, reference is hereby explicitly made to the explanations in connection with the method according to the invention and the cell and / or battery according to the invention and to the figures and the description of the figures.

In addition, the invention relates to a lithium cell and / or lithium battery, for example a lithium-ion cell and / or lithium-ion battery, which is a silicon composite according to the invention, for example silicon-carbon and / or metal Composite, in particular silicon-carbon-metal composite, and / or an inventive anode material comprises.

With regard to further technical features and advantages of the cell and / or battery according to the invention, reference is hereby explicitly made to the explanations in connection with the method according to the invention, the composite according to the invention and the anode material according to the invention and to the figures and the description of the figures.

drawings

Further advantages and advantageous embodiments of the subject invention are illustrated by the drawings and explained in the following description. It should be noted that the drawings have only descriptive character and are not intended to limit the invention in any way. Show it

1 a flow diagram illustrating an embodiment of a method according to the invention for producing a porous silicon composite of a metal-organic framework compound;

2 a flow diagram illustrating a further embodiment of a method according to the invention for producing a porous silicon composite from a metal-organic framework compound by sorption of a silicon precursor; and

3 a flow diagram illustrating a further embodiment of a method according to the invention for producing a porous silicon-carbon composite of a metal-organic framework compound by sorption of a carbon precursor.

1 shows that in one embodiment of the method, a metal-organic framework compound 1 which comprises silicon, for example as an anchor point and / or connecting element, pyrolyzed and / or reduced and / or calcined and / or oxidized and / or etched 1000 becomes. This is a porous silicon composite 10 educated.

2 shows that in another embodiment of the method, first on a metal-organic framework compound 1 which comprises silicon, for example as an anchor point and / or connecting element, and / or on a metal-organic framework compound 2 which comprises at least one metal, for example as an anchor point and / or connecting element, and optionally as such may be silicon-free, a silicon precursor Si is sorbed 100 , in particular absorbed and / or adsorbed, and the metal-organic framework compound with the silicon precursor 1' then pyrolyzed or calcined 1000 ' becomes. This is a porous silicon composite 10 ' educated.

3 shows that in a further embodiment of the method, first on a metal-organic framework compound 1 ; 1' which silicon, for example, as a point of account and / or connecting element 1 ; and / or at least one metal as an anchor point and / or connecting element and, for example, a sorbed silicon precursor 1' comprises a carbon precursor C sorbed 110 , in particular absorbed and / or adsorbed, and the metal-organic framework compound with the carbon precursor 1'' then pyrolyzed or calcined 1000 '' becomes. This is a porous silicon composite 10 '' educated.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2012/028989 A1 [0005]

Cited non-patent literature

• Dalton Transactions, 2013, 42, pages 13806-13808 [0021]
• Coordination Chemistry Reviews, 2003, 246, p.169-184 [0021]
• Dalton Transactions, 2013, 42, pages 13806-13808 [0041]

Claims (15)

Process for producing a porous silicon composite, in particular a silicon-carbon and / or metal composite, ( 10 ; 10 '; 10 '' ) and / or an anode material for a lithium cell and / or lithium battery, in particular for a lithium-ion cell and / or lithium-ion battery, in which a metal-organic framework compound ( 1 ; 1'; 1'' ), which comprises silicon, pyrolyzed and / or reduced and / or calcined and / or oxidized and / or etched ( 1000 ; 1000 '; 1000 '' ) becomes. Process according to claim 1, wherein the metal-organic framework compound ( 1 ) Has nodes and / or connecting elements comprising silicon, and / or wherein at the metal-organic framework ( 1 ; 2 ), in particular gaseous, silicon precursor (Si) is sorbed, in particular absorbed and / or adsorbed, ( 100 ) is or is. Process according to claim 2, wherein the silicon precursor (Si) is present in pores of the metal-organic framework ( 1 ; 2 ) sorbed ( 100 ) is or is. A method according to claim 2 or 3, wherein the silicon precursor (Si) sorbs ( 100 ) and the metal-organic framework compound with the silicon precursor ( 1' ) is pyrolyzed or calcined ( 1000 ' ) becomes. Method according to one of claims 1 to 4, wherein the metal-organic framework ( 1 ; 2 ) Has nodes and / or connecting elements, which comprise at least one metal and / or silicon, wherein the silicon precursor (Si) in pores of the metal-organic framework ( 1 ; 2 ) sorbed ( 100 ) and the metal-organic framework compound with the silicon precursor ( 1' ) is pyrolyzed or calcined ( 1000 ' ) becomes. Method according to one of claims 1 to 5, wherein at the metal-organic framework ( 1 ; 1' ), in particular gaseous, carbon precursors (C) are sorbed, in particular absorbed and / or adsorbed, ( 110 ) becomes. The method of claim 6, wherein the carbon precursor (C) in pores of the metal-organic framework ( 1 ; 1' ) sorbed ( 110 ) becomes. Process according to claim 6 or 7, wherein the carbon precursor (C) sorbs ( 110 ) and the metal-organic framework compound with the carbon precursor ( 1'' ) is pyrolyzed or calcined ( 1000 '' ) becomes. Process according to any one of claims 6 to 8, wherein the metal-organic framework compound ( 1 ; 1' ) Has nodes and / or connecting elements comprising silicon and / or at least one metal, wherein the carbon precursor (C) in pores of the metal-organic framework ( 1 ; 1' ) sorbed ( 110 ) and the metal-organic framework compound with the carbon precursor ( 1'' ) is pyrolyzed or calcined ( 1000 '' ) becomes. Method according to one of claims 2 to 9, wherein the silicon precursor (Si) comprises or is monosilane, and / or wherein the carbon precursor (C) comprises or is acetylene and / or methane. Method according to one of claims 1 to 10, wherein the metal-organic framework ( 1 ; 2 ; 1' ) Nodes comprising at least one metal and connecting elements comprising silicon, or nodes comprising silicon, and connecting elements comprising at least one metal. Method according to one of claims 1 to 11, wherein the metal-organic framework ( 1 ; 2 ; 1' ) or the at least one metal comprises copper and / or aluminum and / or titanium and / or iron and / or magnesium and / or zinc and / or nickel and / or tin, in particular copper. Process according to any one of claims 1 to 12, wherein the metal-organic framework compound ( 1 ; 2 ; 1' ) Copper or Si (O-) ₄ as a node, and / or a silane and / or siloxane, in particular tetrakis (4-tetrazolylphenyl) silane, as a connecting element. Silicon composite, in particular silicon-carbon and / or -metal composite, ( 10 ; 10 '; 10 '' ) and / or anode material for a lithium cell and / or lithium battery, in particular for a lithium-ion cell and / or lithium-ion battery, produced by a method according to one of claims 1 to 13, in particular wherein the composite is a silicon-carbon-metal composite containing silicon and carbon and at least one metal, in particular copper and / or aluminum and / or titanium and / or iron and / or magnesium and / or zinc and / or nickel and / or tin, includes. Lithium cell and / or lithium battery, in particular lithium-ion cell and / or lithium-ion battery, comprising a composite ( 10 ; 10 '; 10 '' ) and / or an anode material according to claim 14.

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