WO1991003080A1

WO1991003080A1 - High-energy secondary battery

Info

Publication number: WO1991003080A1
Application number: PCT/EP1990/001298
Authority: WO
Inventors: Harald BÖHM; James Lowe Sudworth; Peter Barrow
Original assignee: Licentia Patent-Verwaltungs-Gmbh; Lilliwyte, S., A.
Priority date: 1989-08-16
Filing date: 1990-08-08
Publication date: 1991-03-07
Also published as: DE3926977C2; DE3926977A1

Abstract

The invention concerns a high-energy secondary battery cell with a casing containing a solid electrolyte (1) consisting of a $g(b)-aluminium-oxide ceramic material which conducts ions well and which divides the inside of the cell into a positive and a negative electrode (8, 9) and is connected to the positive and negative electrodes by electrically conducting parts of the casing. The solid electrolyte (1) is connected to these two casing parts by a connecting piece (3) made of low-conducting $g(b)-aluminium-oxide ceramic material.

Description

High energy secondary battery

description

The invention relates to a high-energy secondary battery cell with a housing in which there is a solid electrolyte made of good ion-conducting aluminum oxide ceramic, which separates the inside of the cell into a positive and a negative electrode and with an electrically conductive housing part of the positive and negative Electrode is connected.

High energy secondary batteries such as Na / S batteries or zebra batteries use a ceramic electrolyte to separate the positive and negative electrodes. Sodium-ion-conducting aluminum oxide is used as the electrolytic ceramic. This ceramic must be firmly bonded to the housing. to create two completely separate spaces for the positive electrode on the one hand and for the negative electrode on the other. In general, a U-tubular electrolyte is used, which is introduced into a cylindrical housing and is connected directly to the housing via a metal-ceramic connection. The interior in the U-tube is firmly closed by a cover, which cover is also firmly connected to the electrolyte ceramic by a metal-ceramic connection.

The solid electrolyte must have a low electrical resistance. Since the solid electrolyte is a polycrystalline material, the internal crystal and the resistance between the crystals must be low.

The connections of the electrolyte ceramic to the housing on the one hand or the cover on the other hand cannot be used directly as metal ceramic connections

-Ceramic are executed -. Rather, in a known high-energy secondary battery, a transition is formed in such a way that an additional CL-Al oxide ring is inserted, that is to say that the <-AIL oxide ring is placed on the upper edge of the U-tube as an intermediate piece and over a special glass through a melting process connected to the / ύ ceramic. The lid and housing, which also represent the two poles of the cell, are made of two metal ceramic connectors. connected to the. ^ - ring. The r ^ -A l-Ox i dri ng t then runs the + pole from the -Pol the cell. (GB-A-2190 236)

In another case, the β-ceramic is clamped with the glass ring through a pressure seal between the housing and cover. The housing and cover in turn represent the two poles of the cell.

Since these high-energy secondary batteries work at temperatures around 30θ "c and internal pressures also occur, high demands are placed on the sealing of the cells, in particular the transition from the ceramic to the ceramic has to meet high demands.

This means that the expansion coefficients of the j .. ceramic, the ceramic and the glass used must be matched to one another in such a way that this connection can be subjected to temperature fluctuations between room temperature and 400 ° C. without cracks occurring in the ceramic-glass-ceramic transition region . This transition zone is more critical the larger the diameter of the pipe. The same applies if one imagines a disk-shaped electrolyte on the one

is glazed. This area of the ceramic is not only sensitive in terms of the material, it also means additional work steps, namely the production of the rjc-Al oxide ring and the glazing of it

to theA- Kera ik.

Also known is a high-energy secondary battery cell with a housing and a solid electrolyte arranged therein, consisting of good ion-conducting i-aluminum oxide ceramic, which on its side facing a housing part is connected to the housing part via an intermediate layer (US-A-4131 694 ). This intermediate layer consists of aluminum oxide ceramic, in which the sodium ions are exchanged for divalent other ions. The layer is produced by immersing the solid electrolyte in a salt bath with the divalent ions. This creates the approximately 10θ m thick intermediate layer of other conductivity, which is based on the partial exchange of the sodium ions for the foreign ions. Sodium ions remain in the layer, which continue to cause conductivity. That is why there is still an ion migration in the intermediate layer. The ion migration weakens the metal-ceramic connection, which is attached in the region of the transition to the connection to the housing. The invention has for its object to develop such a high-energy secondary battery cell, which contains a solid electrolyte made of highly ion-conducting ^ -alumina ceramic, which separates the inside of the cell into a positive and a negative electrode, in such a way that between the solid electrolyte and the metallic Housing part has a well electrically insulating, temperature-resistant and longer life connection.

In a high-energy secondary battery cell which has an intermediate piece between the solid electrolyte and the electrically conductive housing part, the object is achieved in that the intermediate piece consists of less conductive J-aluminum oxide ceramic. At a

High-energy secondary battery cell, which has an intermediate layer in the area of the connection point, the object is achieved according to the invention in that the intermediate layer is formed as a coating of magnesium oxide or silicon dioxide. The non-conductive or poorly conductive / 3 ceramic is produced by changing the composition of the beta ceramic.

If predominantly boehmite is used as raw material, the proportion of stabilizing ions required can be reduced from the usual 0.7 to 0.2 or 0.1% by weight of lithium oxide. The resistance of a mass containing 0.2% lithium oxide is 15 .5-2'cm at 275 C, while the mass containing 0.7% lithium oxide has only 8 J -_- cm.

A further increase in resistance can be achieved by inserting a boehmite that is not well crystalline, for example Bacasol from BA Chemicals, into the raw material. The material made from a well crystalline boehmite has a resistance of 8 -52 * cm at 275 ^C C, while a material prepared from Bacasol raw material has 4.25 ^ - cm. By using a combination of Bacasol raw material and low lithium content the resistance of the _j-alumina by about an order of magnitude can be increased.

Another possibility is

to produce, which is completely doped with magnesium oxide or lithium oxide. Such a substance has the formula Na ₂ gAlι ₀ 0i7 - this substance has no gaps in the sodium conducting level, so that the sodium ion diffusion is severely hindered. Furthermore, the resistance of a fy'-alumina solid electrolyte can be increased by blocking the sodium ion diffusion at the grain boundaries. A number of foreign substances in the raw material can increase the resistance of the aluminum oxide pellets. The two most important are calcium oxide and silicon oxide. With calcium oxide additives, the formation of intercrystalline calcium aluminate phases has hindered the migration of mobile sodium ions to such an extent that the measured one Resistance increased exponentially with the calcium content at 300 ° C. With silicon oxide, the addition of a few percent by weight increased the resistance of β-aluminum oxide by a factor of 10. A similar effect can be observed if silicon oxide is used for doping "aluminum.

The sodium ions are ion exchangeable in the _c "alumina. Many different (V'-alumina were made by ion exchange with molten salts. The sodium - ^ '- alumina has the lowest ionic resistance of all, but the exchange of a small amount of sodium for a slower moving one ion reduces the sodium mobility. the total resistance can thereby be higher than that of the fully exchanged material with slow mobile ions. Therefore, an increase in resistance by replacing a low sodium content to a large 1 ⁺ ion, for example, cesium, or a 2 ⁺ Ion, for example barium, strontium or calcium, or a 3 ⁱ ion, for example the rare earths. The direct generation of the mixed sodium "-aluminium oxide is preferred here, for example La ³⁺ - o" -aluminium oxides produced by direct sintering.

To increase the resistance of the β "alumina, one or more of the methods described above may be used in any combination. The method selected may depend on whether a part is made and sintered with the beta alumina during firing or whether one two-step joining method is used to press the two objects together, and the high resistance material can also be applied to the edge of the solid electrolyte as a coating or screen printed product.

The material that changes the resistance can be used for the coating of material with high resistance. The cover therefore needs not being of the i "type of alumina, it may contain just those impurities that block the grain boundary path and / or increase the doping level and / or introduce slower moving ions. This alters the / 3" alumina on the surface of its edges to so to increase the resistance of the material at the edges.

There are three main process categories for producing a solid electrolyte with a poorly conductive connection to the housing parts. The first is the production of a solid electrolyte from / -. "-Alumina and a ring made of a modified ^>" - alumina with high resistance and the connection of these two parts. The second is to make a solid electrolyte and then increase the resistance at the edges. The third is to manufacture tools for a dry press or automatic press, which allow the ceramic product to be pressed in one process step.

A solid "aluminum oxide" electrolyte disk can be made by a number of processes, the simplest of which is pressing in an automatic press. The blanks from this process provide flat surfaces. The ring made from modified ^ "aluminum oxide can also be pressed an automatic press, using an appropriate shape. In order to improve the flatness of the surfaces to be connected to one another, processing in the raw state can be carried out. In order to connect the ring made of modified / T'-aluminum oxide and the solid electrolyte, which, apart from being disc-shaped, for example, also cylindrical, for example, by sintering, the ring is placed on the solid electrolyte. There are two ways to burn the two parts:

a) With the hollow cylindrical or disk-shaped solid electrolyte at the bottom and the ring at the top, both parts are sintered together, whereby a suitable refractory material can be placed on the upper end of the ring in order to improve the sintering together due to a weight load.

b) With the ring at the bottom and the hollow cylindrical or disk-shaped solid electrolyte at the top, the weight of the solid electrolyte can support the sintering together. If the weight of the solid electrolyte If an additional weight is not sufficient, for example a suitable refractory material.

The ring and the disk-shaped solid electrolyte can also be produced by the rolling process, continuous casting process and by extrusion. The ring shape is particularly suitable for the extrusion process, although problems may arise when cutting the extruded piece. The continuous casting process or rolling can be used to produce a disk-shaped solid electrolyte. When using the continuous casting process and / or the extrusion process, a higher level of the binder is used. Either by applying pressure in the presence of heat or by using a solvent for the binder, two parts can be joined together as blanks. Therefore, there is rather a hermetic connection between the solid electrolyte and the ring.

The application of a high-resistance coating requires the production of a coating material and the application of the coating. The solid electrolyte can be produced by any of the methods described above.

The coating is generally made by a wet process whereby the ingredients for the coating are milled with a suitable liquid (usually water). The coating is preferably applied by brushing, but spraying or dipping can also be used. When spraying or dipping, the area of the 3 "aluminum oxide that is not to be coated must be covered. The coating can also be applied as a dry powder that is evenly distributed on the surface. When fired, the powder melts and adheres to the surface Other methods of applying a high-resistance coating to a ceramic body are electrophoretic deposition and chemical deposition, but these methods are more complex than the wet method.

After the coating has been applied, the ceramic body is left to dry, if necessary, and then fired in an oven in the customary manner.

With carefully designed tools for dry pressing or die casting, it is possible to manufacture the ceramic body in a single operation. There are two filling openings, one for the "- Aluminum oxide powder and one for the modified 3 "aluminum oxide powder. The procedure is as follows: First the ring part of the mold is filled and then the disc part. Then pressure is exerted on the mold content, so that the two parts not only solidify but also The individual raw body can then be sintered in a suitable furnace using kiln furniture.

In all three production processes, the expression /! "- aluminum oxide powder not only refers to / s" aluminum oxide powder, but also to powder which, when fired, converts to a V'-aluminum oxide ceramic. The term modified "alumina powder refers not only to a powder that is a modified /" ^-A - ^um ".rπump powder, but also to a powder that turns into a modified / V'-alumina powder when fired and is non-conductive or is poorly conductive.

The firing of all components takes place at a firing temperature that gives a product with sufficient density and is carried out in a suitable firing aid.

The invention is described in more detail below with reference to exemplary embodiments shown in a drawing, from which further details, features and advantages result.

Show it:

Figure 1 shows a part of a high energy secondary battery cell in longitudinal section;

Figure 2 shows a part of another embodiment of a

High energy secondary battery cell in longitudinal section.

A Hochenergiesekundärbatteπ ^' ezelle contains a good ion-conductive cylindrical solid electrolyte 1 made of -Al-oxide ceramic, one end 2 of which is connected to a less conductive, for example annular, intermediate piece 3 made of little or non-conductive (j-Al-oxide ceramic). The intermediate piece 3 is connected at its end 4 facing away from the solid electrolyte to a cover 5, which is made of metal, for example From the end 4, extending radially outwards, a metal ring 6 is fastened to the intermediate piece 3, which is part of the housing and is connected to a cylindrical housing section 7. The cover 5 is also part of the housing. The solid electrolyte 1 separates the positive 8 and negative 9 electrodes within the cell. The electrode 9 consists, for example, of sodium.

FIG. 2 shows an embodiment in which a solid electrolyte 1 made of highly ion-conductive aluminum oxide ceramic is provided with a low or non-conductive coating 10 on and near its ends. The cover 5 and the metal ring 6 are connected to the coating 10. Otherwise, the arrangement according to FIG. 2 corresponds to that of FIG. 1.

In the case of the combination of the i-ceramic with high Na ion conductivity with a second ceramic having poor or no conductivity, the procedure is such that the highly conductive electrolyte ceramic is pressed in the known manner in the form of a disk, a U-tube or a tube. The non-conductive or poorly conductive A ceramic is pressed into rings which have such a geometry that they can be connected to the edge zones of the highly conductive ceramic (FIG. 1). These poorly conductive - ceramic rings can be sintered extra; they are then provided with metal rings over a metal-ceramic connection. These rings of poorly conducting ^ ceramics are then connected to the well leitendenf ~ ^Kera roi ^k through a glass seal. 11

However, it is also possible to connect the highly conductive ceramic to the poorly conductive ceramic, both in green condition, by pressing and then to sinter together. This creates an electrolyte ceramic, the edge zone with a poorly conductive ^ ceramic. is provided. This electrolyte ceramic is provided in its poorly conductive edge zone with metal rings via a ceramic-metal connection. In both cases, that is, in the case where the poorly conductive / coated ceramic is glazed to the highly conductive ^ ceramic, or in the case where both ceramics are sintered, the electrolyte ceramics are attached to the two metal rings the housing, or with the cover, which represent the two poles, connected by welding.

In the case of the generation of the non-conductive or poorly conductive edge zone With coatings one proceeds as follows: the highly conductive ß-electrolytic ceramic is manufactured in the usual way by pressing. This can take the form of disks, tubes or U-tubes. In the green state, the ceramic produced in this way is provided with a coating of Mg oxide or Si dioxide in its edge area. This coating is produced by immersing the ceramic in a suspension of Mg oxide or Si dioxide in a liquid, for example water, with its edge zones one or more times. After drying and the subsequent firing at the usual production temperature of the ceramic, an electrolyte body is formed, the edge zones of which are poor or non-conductive. The two metal rings are attached to these edge zones by means of metal-ceramic connections which are produced using known techniques. The electrolyte ceramic is in turn connected to the housing and cover of the cell via the two metal rings. This is the case with tubular cells, with flat cells with disc-shaped electrolytes the two rings are welded to the two housing shells.

Claims

High energy secondary battery patent claims

1. High-energy secondary battery with a housing in which there is a solid electrolyte made of good ion-conducting f -aluminum-oxide ceramic, which separates the inside of the cell into a positive and a negative electrode and, via an intermediate piece, each with an electrically conductive housing part of the positive and negative electrode, characterized in that the intermediate piece consists of less conductive ß-aluminum oxide ceramic.

2.High-energy secondary battery cell with a housing in which there is a solid electrolyte made of good ion-conducting (?> Aluminum oxide ceramic), which separates the inside of the cell into a positive and a negative electrode and with an electrically conductive housing part of the positive and negative Electrode is connected, the solid electrolyte being provided with an intermediate layer in the region of the connection point to the two housing parts, characterized in that the intermediate layer is a coating of magnesium oxide or

Silicon dioxide is formed.

3. High-energy secondary battery according to claim 1, characterized in that larger ions are provided instead of Na ions in the less conductive f> oxide ceramic.

4. High-energy secondary battery according to claim 1, characterized in that the less conductive (-oxide ceramic is mainly made from boehmite and has less than 0.2 wt .-% of lithium oxide.

5. High-energy secondary battery according to claim 4, characterized in that the boehmite is weakly crystalline.

6. High-energy secondary battery according to claim 1, characterized in that the less conductive f-oxide ceramic is heavily doped with magnesium or lithium oxide.

7. High-energy secondary battery according to claim 6, characterized in that the less conductive -Oxide ceramic made of Na ₂ MgAlιoOι? ^' exists.

8. High-energy secondary battery according to claim 1, characterized in that the low-conductivity ß-oxide ceramic is made of a material containing a few percent by weight of calcium oxide.

9. High-energy secondary battery according to claim 1, characterized in that the low-conductivity, oxide ceramic is made of a material containing a few percent by weight of silicon.

10. High-energy secondary battery according to claim 3, characterized in that the larger ions are lanthanum ions or ions of the rare earth metals.

11. High-energy secondary battery according to claim 3, characterized in that the larger ions are calcium ions.

12. High-energy secondary battery according to claim 3, characterized in that the larger ions are barium, strontium or calcium ions.

13. A method for producing a solid electrolyte containing an intermediate piece for a high-energy secondary battery according to claim 1 or one of claims 3 to 12, characterized in that materials made of good ion-conducting β-aluminum oxide ceramic each with a press in the form of the solid electrolyte and Bring intermediate piece and that the solid electrolyte and the intermediate piece are then placed on top of one another and sintered.

14. The method according to claim 13, characterized in that the solid electrolyte lies on the intermediate piece during sintering.

15. The method according to claim 14, characterized in that the intermediate piece lies on the solid electrolyte during sintering and is additionally loaded by a weight.

16. A method for producing a solid electrolyte containing an intermediate piece for a high-energy secondary battery according to claim 1 or one of claims 3 to 12, characterized in that the intermediate piece and the solid electrolyte separating the interior of the cell are each produced by injection molding, then in the raw state under pressure Exposure to heat or a solvent and then sintered.

17. A method for producing a non-conductive or poorly conductive coating on a solid electrolyte of a high-energy secondary battery according to claim

2, characterized in that the coating material ^" is mixed with a liquid, that the solid electrolyte is dipped into the mixture when the parts to be kept free are covered, sprayed with the mixture or coated with the mixture, and that the solid electrolyte is then burned with the coating .

18. A method for producing a non-conductive or poorly conductive coating on a solid electrolyte of a high-energy secondary battery according to claim 2, characterized in that a coating material is applied to the solid electrolyte by electrophoretic or chemical deposition and that the solid electrolyte is then burned.

19. A method for producing a good ion-conducting solid electrolyte with an intermediate piece according to claim 1 or one of claims 3 to 12, characterized in that a shape matched to the shape of the solid electrolyte and intermediate piece is successively filled with the ion-conducting material and then with the material of the intermediate piece pressure is exerted on the contents of the mold and the molded body is then sintered.