DE3210096A1 - Solid proton conductor and its use - Google Patents

Abstract

A description is given of solid proton conductors based on an amorphic matrix material comprising proton-containing cations and a polar vehicle present in the matrix material which promotes the proton transfer, and of its use as a separator material or electrolyte for, for example, electrochemical cells.

Description

description

The invention relates to solid proton conductors and their use.

Proton-conducting solid materials have already become known, such as molybdophosphoric acid and tungstophosphoric acid (H3PW12040 ~ nH20), hydrogenuranyl phosphate (HU02P04 4H20) and hydrous ß-aluminum oxide (W.A.

England et al., Solid State Ionics 1 (1980) 231-249 and P.E. Childs et al., Journal of Power Sources 3 (1978) 105-114). It is also described been that aluminosilicates 1, for example zeolites, also represent ionic conductors (M. Bell et al., DBP, AZ P3 127821.3, 19 # 1,139 and U.S. Patent 3,186,875). In these publications it is also stated that certain solid proton conductors are used as separators for primary and secondary electrochemical cells, d. H. Batteries, can use (P.E. Childs et al., op. and U.S. Patent 3,186,875). Furthermore, T.

Takahashi et al. reported (Journal of Applied Electrochemistry 1o (1980) 41.5 to 416) that the solid proton conductor hydrogenuranyl phosphate (HUO2Po4-4H2o) can be used as an electrolyte for electrochromic display cells.

As is known, it is used for the manufacture of primary cells or secondary cells and electronic components often require electrolytes between electrodes bring in. The liquid electrodes normally used are from Disadvantage, as they are not easily designed as self-supporting structures and often give rise to corrosion problems. Fixed pro tone ladder have increased mechanical stability compared to liquid electrolytes the advantage that they are selective for the transport of one or only a few types of ions are. With the exception of zeolites and ß-aluminum oxide, those previously known react solid proton conductors like a Brönsted acid and are therefore only limited with one Number of electrode materials stable, but not with base metals such as for example iron, zinc, lead, aluminum and the like, which are often used for electrochemical Cells are used. Furthermore, some of the previously known solid proton conductors are very sensitive to reduction, for example the above-mentioned molybdophosphoric acid, are radioactive (e.g. HU02P0 4 # 4H20) or contain toxic heavy metal cations (for example Sb 20541320 or Sn02 # 2,3H20 etc.) Another major disadvantage is that in the conventional solid proton conductors, the water already irreversible at low temperatures (i.e. with destruction of the proton-conducting Phase) is delivered. In addition, most conventional solid proton conductors suffer because their conductivity is too low (see M.S. Whittingham et al., a.a.0.).

The object of the present invention is now to provide solid proton conductors indicate that are both simple and inexpensive to manufacture, those listed above Do not have disadvantages, have high conductivity and for the most diverse Electrochemical purposes can be used, namely as a separator material.

This object is now achieved by the solid proton conductor according to FIG Main claim. The subclaims relate to particularly preferred embodiments this subject of the invention as well as using this solid Proton conductor.

Research has shown that solid proton conductors are based an amorphous matrix material having proton-containing cations and one polar vehicles present therein show high proton conductivity, cheap and can be easily manufactured and not the corrosion and pollution problems have inherent to the conventional solid proton conductors.

The invention therefore relates to solid proton conductors which are characterized are due to an amorphous matrix material containing protons containing cations or Host network and a present in it, which promotes proton transport, polar vehicle or solvent.

The matrix material preferably contains cations containing protons Hydronium cations (1330) 1 ammonium cations (NH4 +), hydrazinium cations (N2H5 +) and / or organic amine cations, the latter being preferably cations based on at least one low molecular weight aliphatic, cycloaliphatic or aromatic amines having 1 to 6 carbon atoms, such as methylamine, ethylamine or pyridine.

These proton-containing cations are by ion exchange or by chemical reaction introduced into the matrix material or the host network. Next to These proton-containing cations are still the proton transport in the matrix material favoring polar vehicle or a polar phase, for example water, ammonia and / or contain an alcohol, since in this way the proton can be moved across the vehicle will.

It is believed that the proton transport of the invention Proton conductor takes place via a vehicle mechanism according to which the proton does not as such, but as a hydronium ion or ammonium ion (H3O +, NH4 + etc.) to the Vehicle, such as HO, NH3, etc., is transported in bound form. The mobile moves polar vehicles within the matrix material in the opposite direction and shows a diffusion coefficient corresponding to the proton conduction and behaves towards the environment like a Brönsted base, d. H. a proton acceptor.

The proton conduction takes place in the proton conductor according to the invention thus via a translational movement of proton-containing cations, such as H3O +, NH4 +, N2H5 +, 13 + -Pyridine, CH3NII3 +, etc., resulting from the formation of the proton-containing Cations used basic phase and the polar vehicle, such as water, ammonia or alcohols, preferably low molecular weight aliphatic alcohols with 1 to 6 Carbon atoms, such as in particular methanol or ethanol, are formed.

The proton conductors according to the invention preferably contain as amorphous Matrix material an inorganic and / or organic material, which with advantage Brönsted acid groups, such as carboxylic acid groups, sulfonic acid groups 3 and / or phosphate groups (P04) as functional groups. Matrix materials suitable according to the invention are in particular cellulose or cellulose derivatives, such as carboxymethyl cellulose, and amorphous silicates such as glasses and / or precipitated exilic acid. It has shown, that celluloses which contain a Bronsted acid as a functional group and moreover contain a minimum amount of water adsorbed as a polar vehicle, high proton conduction exhibit. However, when in contact with water, such proton conductors take so much water on that their ion selectivity is severely impaired. According to a preferred Embodiment of the invention, however, one can use the proton selectivity of these matrix materials increase considerably by increasing the lipophilic character of the cellulose, so that it can only absorb a little water. Preferably one effects this increase in the lipophilic character through esterification, etherification and / or reduction the hydroxyl groups of cellulose. The organic matrix materials used according to the invention have the advantage that they can be dissolved in organic solvents and in this Way very easy to process into foils and / or thin layers.

The production of amorphous, water-containing silicates and their application as thermoplastics have already been described in the literature (J. Moriya and M. Nogami, J. Non-Crystalline Solids 38 and 39 (1980) 667; R.F.

Bartholomew and J.W.H. Schreuers, J. Non-Crystalline Solids 38 and 39 (1980) 679; R.F. Bartholomew, P.A. Tick and S.D. Stookey, J. Non-Crystalline Solids 38 and 39 (1980) 637 and U.S. Patent 3,912,481). It has now been shown that these amorphous hydrous silicates by introducing proton-containing cations and the polar vehicle can be given proton-conducting properties, so that in this way solid proton conductors are obtained which are like a Bronsted acid or a Brönsted base react.

The inorganic amorphous matrix material used is preferably the very open silica network of glasses or the very open structure of pure precipitated silica. Is it brought about by ion exchange or by chemical reaction a substance with a basic reaction to the matrix material (e.g. Nu4, N2135 +, t H + -pyridine, H -amine) one and above out another portion of the polar vehicle (e.g. water) for reduction the local electric field strength, a proton conductor according to the invention is obtained, in which the proton is mobile together with the vehicle. According to another preferred embodiment of the invention Brönsted acid groups in the matrix material introduces (e.g. phosphate groups), so also form less basic vehicles, like water, with protons proton-containing cations (e.g. H30), which are the desired Cause proton conductivity.

Particularly preferred solid proton conductor with an inorganic, amorphous matrix material contain at least 50% by weight SiO2.

In a further preferred embodiment of the invention comprise these solid proton conductors based on an inorganic, amorphous matrix material at least So wt .-% Si02, at least 0.1 wt .-% P 205 or NH3 (as N134) and at least 1 GewO-90 water.

It has also been shown that the solid proton conductor according to the invention because of their low necessary water content and their weak basic behavior do not cause any corrosion problems with the electrodes in contact with them, so that they are particularly good as separator material or electrolyte for primary or secondary electrochemical cells, fuel cells, electrolysis cells, electrochromic Displays, electronic storage elements (e.g. timers, memory elements, etc.) and the like suitable. In particular, they can be used with advantage where in addition to a high proton conductivity, a high diffusion coefficient of water is also necessary is, for example for metal / air cells and metal-metal-oxide cells, since the opposite transport of protons and water molecules gross one 02 - trans- port results.

The invention therefore also relates to the use of the invention solid proton conductor according to claim 19 as a separator material or electrolyte for primary and secondary electrochemical cells, fuel cells, electrolysis cells, electrochromic displays and electronic storage elements.

The following examples serve to further illustrate the invention.

Example 1 Carboxymethyl cellulose (Servacel type CM23) is compressed at a pressure of 1O7 Pa and brings the material with the saturation vapor pressure equilibrium of water at room temperature. A material is obtained with a -4 -1 -1 specific proton conductivity of 2 x 10 ohms 1 cm Example 2 In one Three-necked flask fitted with a reflux condenser, a dropping funnel and a stirrer is equipped, 20 g of carboxylmethyl cellulose (Servacel type CM 23) are presented and a mixture of 200 ml of pure acetic acid is added dropwise while stirring and while cooling with ice, 100 ml of acetic anhydride and 10 ml of the purest sulfuric acid. Then stir during an additional 90 minutes and heat the mixture to complete the reaction during 70 minutes at 450C. The reaction is started by adding ice water while cooling with ice stopped.

The product is filtered off and washed until the supernatant Solution has a specific conductivity less than 10 6 ohms 1 cm 1. Then you dry the material gently.

The carboxymethyl cellulose acetate obtained in this way is in a dichloromethane / methanol mixture (90/10) soluble and can be poured process into thin layers or foils. These are compact, brittle and of gray color. The specific conductivity of this material is at a level of humidity of 80% in the proton form 5 x 10 ## 5 Ohm 1 cm 1 and in the Na form only 6 x 10 ohm cm Example 3 A melted at 11000C and treated in air Glass cooled to room temperature with the composition 20% Na2O, 78% SiO2 and 2% P205 at a pressure of 2 bar for 24 hours with steam at one temperature from 1400C. This increases the volume of the material by a factor of about 1.3, while the water content increases to about 13% and the Na2O content increases drops by about 2%. A transparent and mechanically stable material is obtained, which at room temperature has a proton conductivity of 5 x 10 ## Ohm 1 cm 1 (Ea = 0 # 4 eV). Reduced after equilibrium with the ambient air the water content is about 2.5%, with the proton conductivity then at 2 x 10 ## Ohm 1cm 1 <Ea = 0.63 eV).

Example 4 5 g of silica (SiO xH20, Merck No. 657) 2 are added 2 in 250 ml of one with ammonium carbonate ((N134) 2CO3) or

Ammonium chloride (NH4Cl) saturated solution and leaves she there with constant stirring for a day at a temperature of 800C.

In this way, the free silanol groups of the silica become one Surface connection with the ammonium ions present in the solution is a [(R-SiO) - + NH4 +].

The product is filtered off and washed with water until the solution has a conductivity of less than 10-6 ohm-1 cm-1. The material leaves now squeeze into hard pills that depend on the partial pressure of the water of the surrounding area up to 25% 1320. The proton conductivity is then 5 x 10 3 Ohm 1cm 1. A possible water release is reversible and influences the Dimensional stability of the compacts not.

Claims (19)

Solid proton conductors and their uses Claims Fixed proton conductors, g e k e n n n z e i c h n e t d u r c h containing cations containing protons, amorphous matrix material and a proton transport that is present in it, polar vehicle. 2. Proton conductor according to claim 1, d a d u r c h g e k e n n z e i c h n e t that as proton-containing cations they are hydronium cations and ammonium cations (NH4 +), hydrazinium cations (N2H5) and / or organic amine cations (H + -amine) contain. 3. Proton conductor according to claim 2, d a d u r c h g e k e n n z e i c h n e t that the organic amine cation a cation based at least one low molecular weight, aliphatic, cycloaliphatic or aromatic Amine with 1 to 6 carbon atoms, preferably based on methylamine, Is ethylamine or pyridine. 4. proton conductor according to claims 1 to 3, d a -d u r c h g e it is not stated that they are polar as favoring proton transport Vehicles contain water, ammonia and / or an alcohol. 5. proton conductor according to claim 4, d a d u r c h g e k e n n z e i c h n e t that they have at least one low molecular weight aliphatic alcohol Contain alcohol with 1 to 6 carbon atoms, preferably methanol or ethanol. 6. proton conductor according to one of the preceding claims, d a d u Noted that it is an inorganic matrix material as an amorphous matrix material and / or contain organic material. 7. proton conductor according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the amorphous matrix material Brönsted acid groups as functional Contains groups. 8. proton conductor according to claim 7, d a d u r c h g e k e n n z e i c h n e t that the amorphous matrix material as Brönsted acid groups, carboxylic acid groups, Contains sulfonic acid groups and / or phosphate groups. 9. proton conductor according to claims 6 to 8, d a -d u r c h g e it is not indicated that it is used as an amorphous matrix material cellulose and / or contain a cellulose derivative. 10. Proton conductor according to claim 9, d a d u r c h g e k e n n z e i n e t that it is a cellulose or a cellulose derivative with increased lipophilic properties Character included. 11. Proton conductor according to claim lo, d a d u r c h g e k e n n z e i c h n e t that they contain a cellulose or a cellulose derivative, their lipophilic character due to esterification, etherification and / or reduction of the hydroxyl groups has been increased. 12. Proton conductor according to claims 1o and 11, d a d u r c h g It is not noted that it is carboxymethylcellulose as a cellulose derivative or carboxymethyl cellulose acetate. 13. Proton conductor according to claims 6 to 8, d a -d u r c h g e it is not stated that the amorphous matrix material used is an amorphous silicate and / or contain precipitated silica. 14. Proton conductor according to claim 13, d a d u r c h g e k e n n z e i c h n e t that they contain a glass as amorphous silicate. 15. Proton conductor according to claims 13 or 14, d a d u r c h g It is not noted that they contain at least 50% by weight of SiO2. 16. Proton conductor according to claim 15, d a d u r c h g e k e n n z e i c h n e t that they contain at least 50 wt .-% SiO2, at least 0.1 wt .-% P 205 and contain at least 1% by weight 1320. 17. Proton conductor according to claim 15, d a d u r c h g e k e n n z e i c h n e t that they contain at least 50% by weight of Sir2, at least 0.1% by weight of NH3 (as Nu4) and contain at least 1% by weight of H20. 18. Proton conductor according to the preceding claims, d a d u r c h e k e n n n z e i n e t that they are in the form of a film and / or a thin Layer present. 19. Use of the solid proton conductor according to claims 1 to 18 as separator material or electrolyte for primary and secondary electrochemical Cells, fuel cells, electrolytic cells, electrochromic displays and electronic Storage elements.