RU2153736C2 - Plate manufacturing process for chemical current source - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: lithium foil sheets alternating with intermetallic compound layers are jointly subjected to heat treatment at lithium melting temperature. Intermetallic compound layer is prepared from its powder having particle size of 40 to 350 micron mixed up with asbestos by filtering water slurry onto planar surface, proportion of ingredients being as follows, mass percent: intermetallic compound - 89-97; asbestos - 3-11; this procedure is followed by drying the layer obtained. EFFECT: facilitated procedure. 1 tbl, 2 ex

Description

 The present invention relates to chemical current sources, and in particular to a method for manufacturing an electrode of a chemical current source based on lithium intermetallic compounds, for example, Li-Si, Li-Si-Al, Li-Si-B, etc. Electrodes from these alloys are used in heat sources current (TIT) and current sources with aprotic electrolytes.

 Various methods are known for manufacturing electrodes from lithium alloys. The most commonly used are: pyrometallurgical [1], which consists in fusing lithium with alloy components, grinding, mixing with electrolyte and pressing, and the metal matrix method, which in the element acts as a current collector, is a powder of lithium alloy prepared by the pyrometallurgical method. The disadvantages of the pyrometallurgical method is, firstly, its lack of manufacturability: the method requires special equipment (an electric furnace with an inert medium, a mill, a press, etc.). Secondly, highly toxic aerosols of lithium compounds, even if precautionary measures are taken, fall into the air of the production room. The disadvantage of the impregnation method is that in this way it is impossible to produce an electrode of high specific capacity, a matrix cannot be made smaller than certain sizes.

 The method consists in joint heat treatment in the pre-loaded state of lithium with other components of the alloy at a temperature above the melting point of lithium.

 The method includes the following operations: production of lithium foil, production of a perforated aluminum mesh, preparation of a paste from a powder with a binder - sodium metasilicate, applying a silicon paste to an aluminum mesh, drying, heat treatment of a mesh with a silicon layer, joint embossing of a package consisting of lithium foil , aluminum perforated mesh and aluminum mesh coated with silicon. Then, cutting and rolling of the electrode blanks in the casing and heat treatment of the electrode at a temperature above the melting point of lithium is performed. Using the thermal diffusion method, it is possible to obtain electrodes with high specific characteristics. However, the method involves many operations, some of them, for example, the manufacture of aluminum perforated mesh, applying paste to the mesh, embossing lithium with alloy components, etc. uncontrollable and do not provide the possibility of obtaining electrodes with reproducible characteristics.

 In order to simplify the method, we offer the following method of manufacturing an electrode. A layer of an intermetallic component is obtained from a powder mixture of an intermetallic component with particle sizes of 40 to 350 μm with asbestos by filtering an aqueous suspension containing an intermetallic component of 89-97 wt.%, Asbestos of 11-3 wt.%, On a flat surface and the casting is dried. Then blanks are cut out from it, equal in size to the future electrode for joint heat treatment of them in a pressed state with lithium foil of the same size.

 We used asbestos in the form of fibers as a fibrous binder, which forms a stable suspension in water, which is very important because it allows castings to be obtained with a layer of evenly distributed powder of an intermetallic component (CI) and asbestos. The ratio of the amount of lithium and the component of the intermetallic compound (silicon, aluminum, boron, etc.) is chosen so as to obtain an alloy (intermetallic compound) of a given composition.

The advantages of the proposed method:
1) simplicity of the process. The operations disappear: the manufacture of a perforated aluminum mesh, the preparation of a lithium-mesh component of an intermetallic package, the embossing of a package in embossed rolls.

Castings can be produced outside the lithium electrode manufacturing area and used as needed, as the shelf life of dried castings is unlimited;
2) the proposed method allows for trouble-free production, because waste generated after cutting blanks are used in the subsequent manufacture of the suspension component of the intermetallic asbestos-water.

Lithium foil waste after cutting blanks is melted under a layer of liquid paraffin, and the resulting ingot is again rolled into foil;
3) the method allows to obtain electrodes of a given composition by the content of lithium and other components (varying their ratio), a given capacity and thickness (by varying the amount of lithium foil and asbestos-component castings).

 The set of distinguishing features of the invention in the literature is not found.

 Example No. 1.

 The manufacture of the electrode of LiSi according to the proposed method of silicon powder of different dispersion.

 Polycrystalline silicon was ground in a ball mill and sieved through sieves: 1) 0040, 2) 035. In the first case, a uniform casting could not be made from a powder with a particle size of less than 40 microns, because in water, it formed suspended particles that settled on top of asbestos.

 In the manufacture of castings of an intermetallic component of silicon particles larger than 350 microns in size, the casting “crumbles”, because large silicon particles form the bottom layer.

 Good durable castings of the component of the intermetallic compound are obtained using powder - a mixture of different disperse compositions between 40 and 350 microns. Their thickness, depending on the absolute amounts of the powder component and asbestos, is from 0.3 to 0.85 mm.

 Example No. 2.

 The manufacture of the LiSi electrode according to the proposed method with different ratios of the components of intermetallic (KI) and asbestos in the form of castings from an aqueous suspension containing different ratios of KI and asbestos. For this, an aqueous suspension was prepared from silicon and aluminum powders of a fraction of 40–350 μm and asbestos. The ratios of KI and asbestos were checked by KI-A, wt.%: 98-2; 97-3; 94-6; 89-11; 88-12.

After drying, blanks with a diameter of 35 mm were cut out from the casting. In a case with a diameter of 35.5 mm made of a strip of mild steel 0.05 mm thick, parts were placed: a cast of KI with a diameter of 35 mm, a lithium foil disk with a diameter of 35 mm with a thickness of 0.29 mm, 2 castings of KI with a diameter of 35 mm. The body was rolled. The electrode was pressed and subjected to heat treatment in a pressed state at a temperature of 350 ± 20 ^o C for 20 minutes

 The fabricated electrode is a disk with a diameter of 35 mm and a thickness of 0.85 mm. The electrical characteristics of the electrodes at different ratios of KI-asbestos in the casting of the component of the intermetallic are shown in the table.

 From the test results it follows that the characteristics of the elements with electrodes made in accordance with the invention are higher in comparison with the control, however, with a KI-asbestos ratio of 88-12 wt.%, The characteristics deteriorate. Therefore, we offer the ratio of KI-asbestos: KI - 89-97 wt.%, Asbestos - 11-3 wt.%.

 From the test results it follows that the characteristics of the elements with electrodes made in accordance with the invention are higher in comparison with the control, however, with a KI-asbestos ratio of 88-12 wt.%, The characteristics deteriorate. Therefore, we offer the ratio of KI-asbestos: KI - 89-97 wt.%, Asbestos - 11-3 wt.%.

 From the above examples, it follows that with a significant simplification of the method of manufacturing the electrodes (eliminating the operations of cutting through the aluminum mesh, annealing the mesh, applying silicon paste to the mesh, drying the mesh with paste, embossing the bag, etc.), the electrodes are better compared to the prototype (control elements) electrical characteristics.

Literature
1. EC Gay, DE Vissers, Nen-Ping Yao, FY Martino. Power sourses 6 edited by DH Collins. London, NY 1977, p. 735.

 2.4011372 A, 03.24.1977.

Claims (1)

A method of manufacturing an electrode of a chemical current source by jointly heat-treating in a compressed state lithium foil sheets alternating with layers of intermetallic components at a temperature higher than the lithium melting temperature, characterized in that the layer of the intermetallic component is obtained from a mixture of its powder with particle sizes of 40 - 350 μm s asbestos by filtering the aqueous suspension on a flat surface in the following ratio of the components of the mixture, wt.%:
Intermetallic Component - 89 - 97
Asbestos - 3 - 11
and subsequent drying of the obtained layer.

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