KR20130033369A - Novel metal-organic frameworks as electrode material for lithium ion accumulators - Google Patents

Abstract

The present invention relates to an electrode material suitable for lithium ion accumulators and comprising a porous metal organic structure, wherein the structure comprises lithium ions and optionally at least one additional metal ion and at least one at least bidentate organic compound, at least one of at least two Site organic compounds are based on dihydroxydicarboxylic acids that can be reversibly oxidized into quinoid structures. The present invention also relates to such porous metal organic structures, uses of the structures, and also lithium ion accumulators comprising such electrode materials.

Description

Novel metal organic structure as electrode material for lithium ion storage battery {NOVEL METAL-ORGANIC FRAMEWORKS AS ELECTRODE MATERIAL FOR LITHIUM ION ACCUMULATORS}

The present invention is suitable for lithium ion accumulators and includes an electrode material comprising a porous metal-organic framework, the metal organic structure itself, the use of the metal organic structure, and also the electrode material. It relates to a storage battery including.

Lithium ion batteries or lithium ion accumulators have a high energy density and are thermally stable. Here, the fact that when lithium is used high battery voltage is obtained because of its high negative standard potential.

However, the high reactivity of elemental lithium requires the provision of special lithium sources and electrolytes.

In relatively recent developments, porous organic structures are described which contain lithium ions and are therefore mainly suitable for lithium ion batteries or accumulators.

Thus, for example, G. de Combarieu et al., Chem. Mater. 21 (2009), 1602-1611, describe the electrochemical stability of porous metal organic structures based on iron terephthalate in lithium ion batteries.

G. Ferey et al., Angewandte Chemie 119 (2007), 3323-3327 describe additional Li / Fe based metal organic structures possessing reversible redox and sorption properties. Here too, terephthalic acid acts as an organic ligand in the metal organic structure.

Despite being an electrode material based on metal organic structures known from the prior art for lithium ion batteries, in terms of their suitability as electrode material, in particular the electrochemical capacity of the electrode material (very particularly on a mass basis) There is still a need for an improved system.

It is therefore an object of the present invention to provide such an electrode material. The object is achieved by an electrode material suitable for lithium ion accumulators and comprising a porous metal organic structure, wherein the structure comprises lithium ions and optionally one or more additional metal ions and one or more at least didentate organic compounds. And at least one bidentate organic compound is based on a dihydroxydicarboxylic acid which can be reversibly oxidized into a quinoid structure.

A further aspect of the invention is a porous metal organic structure as described herein.

The use of dihydroxydicarboxylic acids that can be reversibly oxidized to quinoid structures or derivatives thereof has been found to be particularly suitable for lithium ion accumulators and to provide structures with good capacity / mass values.

The porous metal organic structure of the present invention firstly comprises lithium ions. The lithium ions may be partially bonded, in particular ionic, to the deprotonated hydroxyl functional groups herein. Lithium ions can also function to constitute the skeleton of the structure. In this case, it is sufficient that only lithium ions are present in the structure.

In addition, one or more other metal ions other than lithium may optionally be present. Thus, the ions participate in the formation of the metal organic structure. Thus, for example, additional metal ions may be present in addition to lithium ions. Likewise, it is possible for two, three, four or five or more additional metal ions to be present. Here, the metal ions can be derived from one metal or various metals. If two or more metals are derived from one and the same metal, these metals must be in different oxidation states.

In a preferred embodiment, the porous metal organic structure of the present invention does not contain additional metal ions other than lithium ions.

In alternative embodiments, the porous metal organic structures of the present invention comprise one or more additional metal ions in addition to lithium. The one or more additional metal ions are preferably selected from the group consisting of metal cobalt, iron, nickel, copper, manganese, chromium, vanadium and titanium. Cobalt, iron, nickel and copper are more preferred. Cobalt and copper are even more preferred.

One or more at least bidentate organic compounds are required to form the porous metal organic structure of the present invention. Therefore, it is possible that either at least one bidentate ligand organic compound or a plurality of different bidentate organic compounds is present. At least 2, 3, 4 or 5 or more bidentate organic compounds may be present in the structures of the present invention.

One or more at least bidentate organic compounds are based on dihydroxydicarboxylic acids that can be reversibly oxidized to a quinoid structure.

In this regard, "quinoid" means in particular that two hydroxyl groups can be oxidized to an oxo group. "Reversibly" especially means that the oxidation can be carried out again after reduction.

For the purposes of the present invention, the term "derived" means that one or more at least bidentate organic compounds are present in some or all deprotonated form relative to the carboxyl functional groups. Moreover, it is preferable that at least one at least bidentate organic compound is also at least partially deprotonated in a reduced state with respect to its hydroxy group to bind lithium ions, usually via ionic bonding. Moreover, the term "derived" means that one or more at least bidentate organic compounds may bear additional substituents. Thus, one or more independent substituents such as amino, methoxy, halogen or methyl groups may be present in addition to the carboxyl functional groups. It is preferred that there are no further substituents or only F substituents. For the purposes of the present invention, the term "derived" also means that carboxyl functional groups may exist as sulfur analogues. Sulfur analogs are -C (= 0) SH and its tautomers and -C (S) SH. It is preferred that no sulfur analogue is present.

In addition to these one or more at least bidentate organic compounds, the metal organic structure may also comprise one or more monodentate ligands.

At least one bidentate organic compound should have a parent molecule capable of forming a quinoid system. This is particularly achieved by the parent molecule having a double bond system conjugated with an oxo group, in particular by the presence of C-C double bonds. Such parent molecules are known to those skilled in the art. Examples are benzene, naphthalene, phenanthrene or similar parent molecules. Thus, they carry at least hydroxy / hydroxyl groups and carboxy / carboxylate groups.

In a preferred embodiment, the dihydroxydicarboxylic acid is dihydroxybenzenedicarboxylic acid, in particular 2,5-dihydroxyterephthalic acid,

The porous metal organic structures of the present invention can in principle be produced in the same way as comparable metal organic structures known from the prior art. In particular, mention may be made of lithium-based metal organic structures as described in WO-A 2010/012715.

The preparation of doped or impregnated metal organic structures is described, for example, in EP-B 1 785 428 and EP-A 1 070 538. As described, for example, in US Pat. No. 5,648,508, apart from conventional methods of making porous metal organic structures (MOF), the structures can also be produced by electrochemical methods. The metal organic structures produced by this method possess very good properties.

A further aspect of the invention is a storage battery comprising the electrode material of the invention.

The production of accumulators according to the invention is known in principle from the prior art for the production of lithium ion accumulators or lithium ion batteries. See, for example, DE-A 199 16 043. Since the structural principles for the storage battery or battery are the same, it can be referred to later as a lithium ion battery or battery for the sake of simplicity.

Electrode materials suitable for the reversible storage of lithium ions are usually fixed to the power outlet electrodes by a binder.

In charging the cell, electrons flow through an external voltage source and lithium cations flow through the electrolyte to the anode material. When a cell is used, lithium cations flow through the electrolyte, while electrons flow through the rod from the anode material to the cathode material.

To avoid short circuits in the electrochemical cell, an electrically insulating layer through which cations can nevertheless pass is present between the two electrodes. It may be a solid electrolyte or a conventional separator.

In the manufacture of many electrochemical cells, for example in the case of lithium ion batteries in the form of round cells, the necessary battery foils / films, namely cathode foils, anode foils, and separator foils, are combined by a rolling device to form a battery roll. do. In a conventional lithium ion battery, the cathode foil and the anode foil are connected to the power outlet electrode in the form of, for example, aluminum or copper foil. Such metal foils ensure sufficient mechanical stability.

On the other hand, the separator film must withstand mechanical stress on its own, which stress does not pose a problem, for example in the case of conventional separator films based on polyolefins of the thickness used.

The invention also provides the use of the porous metal organic structure according to the invention in electrode materials for lithium ion accumulators.

The electrode material of the present invention is particularly suitable for use in storage batteries. The electrode material can basically be used in electrochemical cells.

The invention therefore also provides an electrochemical cell comprising the electrode material according to the invention and also provides the use of the porous metal organic structure according to the invention in an electrode material for an electrochemical cell.

The drawings are as follows.

1 shows the XRD analysis of Li-2,5-dihydroxyterephthalic acid MOF. Here, as in FIGS. 3 to 5, the intensity I (Lin (coefficient)) is shown as a function of the 2 theta scale 2θ.

2 shows SEM analysis of Li-2,5-dihydroxyterephthalic acid MOF.

3 shows the XRD analysis of Li-Co-2,5-dihydroxyterephthalic acid MOF.

4 shows the XRD analysis of Co-2,5-hydroxyterephthalic acid MOF.

5 shows the XRD analysis of Cu-2,5-dihydroxyterephthalic acid MOF.

6 shows SEM analysis of Cu-2,5-dihydroxyterephthalic acid MOF.

Example

Example  One: Li -2,5- Dihydroxyterephthalic acid MOF Synthesis of

Experimental Method

Starting material Mol calculated

1) 2,5-dihydroxyterephthalic acid 151.5 mmol 30.0 g 30.0 g

2) lithium hydroxide 606.0 mmol 14.3 g 14.3 g

3) DMF 8.17 mol 600.0 g 600.0 g

4) Water 11.6 mol 210.0 g 210.0 g

In a glass beaker, 2,5-dihydroxyterephthalic acid was dissolved in DMF. In a second glass beaker, lithium hydroxide was dissolved in water. This solution was added dropwise to the first yellow solution. Immediately before the end of the addition, the solution became cloudy and turned to a green suspension. This was filtered after an hour and the solid washed four times with 100 ml of DMF each time. The filter cake was dried overnight at room temperature under reduced pressure.

Product weight: 35.9 g

Color: Yellowish Green

Solids concentration: 4.2%

Yield based on Li: 77.9%

Analyze :

Langmuir SA (preactivation at 130 ° C.): 13 m ² / g (BET: 9 m ² / g)

Chemical analysis :

42.1 g / 100 g of carbon

Oxygen 41.1 g / 100 g

Nitrogen 4.7 g / 100 g

Li 9.0 g / 100 g

Example  2: Co -2,5- Dihydroxyterephthalic acid MOF ( Co - DHBDC - MOF )of Li  Doping

Experimental Method

Starting material Mol calculated

1) Co-DHBDC MOF 5.0 g 5.0 g

2) Lithium hydroxide 25 mmol 0.6 g 0.6 g

3) DMF 1.09 mol 80.0 g 80.0 g

4) 0.5 mol 9.0 g 9.0 g water

In a glass beaker, Co-2,5-dihydroxyterephthalic acid MOF (see 2a) was suspended in DMF. In a second glass beaker, lithium hydroxide was dissolved in water. This solution was added dropwise to the first red suspension. The suspension turned slightly dark red. After 2 hours, the suspension was filtered and the solid washed four times with 100 ml of DMF each time. The filter cake was dried overnight at room temperature under reduced pressure and then at 130 ° C. for 16 hours under reduced pressure.

Product weight: 5.5 g

Color: brownish green

Solids concentration: 5.8%

Yield based on Li: 88%

Analyze :

Langmuir SA (pre-activated at 130 ° C): 169 m ² / g (BET: 125 m ² / g)

Chemical analysis :

32.0 g / 100 g of carbon

Oxygen 37.4 g / 100 g

Nitrogen 5.1 g / 100 g

Co 21.1 g / 100 g

Li 9.0 g / 100 g

Example  2a: Co -2,5- Dihydroxyterephthalic acid MOF Synthesis of

Starting material :

1) 64.85 g, Co (NO ₃ ) ₂ × 6 H ₂ O

2) 33.25 g, 2,5-dihydroxyterephthalic acid

Solvent :

1) 3500 ml (3325 g), DMF

2) 175 ml, H ₂ O

Experiment method :

a) Synthesis: 2,5-dihydroxyterephthalic acid and cobalt nitrate were dissolved in a 4 L flask, heated to 100 ° C. over 1.5 hours and stirred at 100 ° C. under N ₂ for 8 hours.

b) Post-treatment: filtered at room temperature under N ₂ , washed with 1000 ml of DMF 1000 ml / MeOH, split the filtrate in half and in each case extracted with 600 ml of MeOH overnight (16 h).

c) Drying: carried out over the weekend at room temperature under reduced pressure.

Color: Orange

Yield: 47.2 g

Solids concentration: 1.31%

Yield based on Co: 92.0%

Analyze :

Langmuir SA (pre-activated at 130 ° C.): 1311 m ² / g (BET: 961 m ² / g)

Chemical analysis :

30.8 g / 100 g of carbon

Co 25.5 g / 100 g

Example  3: Cu -2,5- Dihydroxyterephthalic acid MOF ( Cu - DHBDC MOF )of Li  Doping

Starting material Mol calculated

5) Cu-DHBDC MOF 5.0 g 5.0 g

6) Lithium hydroxide 80.8 mmol 0.6 g 0.6 g

7) DMF 1.09 mol 80.0 g 80.0 g

8) water 0.5 mol 9.0 g 9.0 g

In a glass beaker, Cu-2,5-dihydroxyterephthalic acid MOF (see 3a) was suspended in DMF. In a second glass beaker, lithium hydroxide was dissolved in water. This solution was added dropwise to the first suspension. After 2 hours, the suspension was filtered and the solid washed four times with 100 ml of DMF each time. The filter cake was dried overnight at room temperature under reduced pressure and then for 16 hours at 130 ° C. under reduced pressure.

Product weight: 5.5 g

Color: brown

Solids concentration: 5.8 wt%

Analyze :

Langmuir SA (pre-activated at 200 ° C): 577 m ² / g (BET: 430 m ² / g)

Chemical analysis :

Cu 33.0 g / 100 g

Li 3.7 g / 100 g

Example  3a: Cu -2,5- Dihydroxyterephthalic acid MOF Synthesis of

Starting material :

2 × 34.2 g, Cu (NO ₃ ) ₂ × 3 H ₂ O = 2 × 141.6 mmol

           M = 241.6 g / mol

2 x 13.3 g, 2,5-dihydroxyterephthalic acid = 2 x 67.13 mmol

               M = 198.13 g / mol

Solvent :

2 × 700 ml, DMF, Density: 0.95 g / ml = 1300 g

2 × 35 ml, H ₂ O

Experimental method : 2 × 2 L batch

Synthesis: 2,5-dihydroxyterephthalic acid and copper nitrate were dissolved in a 2 × 2 L flask, heated to 100 ° C. over 1.5 hours and stirred at 100 ° C. for 8 hours.

Work up: filtered at room temperature under N ₂ , wash with 2 × 250 ml DMF / 4 × 250 ml MeOH and extract the residue with 330 ml MeOH overnight (16 h).

Drying: carried out for 48 hours at room temperature under reduced pressure.

Activation: carried out at 130 ° C. for 16 hours under reduced pressure.

Color: reddish brown

Yield: 40.7 g

Solids concentration: 2.8%

Metal Analysis: Cu: 39%

Analyze :

Langmuir SA (pre-activated at 130 ° C): 1183 m ² / g (BET: 879 m ² / g)

Chemical analysis :

26.3 g / 100 g of carbon

Cu 39 g / 100 g

Electrochemical Characterization

NMP (N-methyl-2-pyrroli) with 1.5 g MOF, 0.75 g Super P (conductive carbon black additive, Timcal), 0.12 g KS (conductive graphite additive, Timcal), 0.75 g PVDF (polyvinylidene fluoride) Don) was mixed in 50 ml and stirred for 10 hours.

The dispersion was applied to the Al foil by a doctor blade and dried at 120 ° C. under reduced pressure for 10 hours.

Test of Electrochemical Cells According to the Invention

In order to characterize the composite electrochemically, electrochemical cells were constructed. Anode: 50 μm thick Li foil; Separator: Freundenberg 2190 (Freundenberg); Cathode: Al foil with MOF as described above; Electrolyte: EC (ethylene carbonate) / DEC (diethyl carbonate) 3: 7% by volume with 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ).

Charging and discharging of the cells were performed at a current of 0.02 mA. The results are summarized in Table 1 below.

[Table 1]

MOF material potential region, V capacity, mAh / g, MOF

Example 1 1.5-4.8 240

Example 2 1.5-4.8 175

Example 3 1.5-4.8 260

Claims (10)

An electrode material suitable for a lithium ion accumulator and comprising a porous metal-organic framework, the structure comprising lithium ions and optionally one or more additional metal ions and one or more at least bidentate organic compounds Wherein the at least one bidentate organic compound is based on a dihydroxydicarboxylic acid that can be reversibly oxidized into a quinoid structure. The electrode material of claim 1 comprising one or more additional metal ions. The electrode material of claim 2, wherein the one or more additional metal ions are selected from the group consisting of metal cobalt, iron, nickel, copper, manganese, chromium, vanadium and titanium. The electrode material according to any one of claims 1 to 3, wherein the dihydroxydicarboxylic acid is dihydroxybenzenedicarboxylic acid. The electrode material according to any one of claims 1 to 4, wherein the dihydroxydicarboxylic acid is 2,5-dihydroxyterephthalic acid. The porous metal organic structure according to any one of claims 1 to 5. Use of the porous metal organic structure according to claim 6 in electrode materials for lithium ion accumulators. A storage battery comprising the electrode material according to any one of claims 1 to 5. An electrochemical cell comprising the electrode material according to any one of claims 1 to 5. Use of the porous metal organic structure according to claim 6 in electrode materials for electrochemical cells.

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