Annular cathode electrode structures for sodium sulphur cells

In a sodium sulphur cell, an annular cathodic electrode structure having a porous matrix of electronically-conductive material impregnated with an electro-chemical reactant material comprising sulphur/polysulphides which is solid at room temperature, said electrode structure comprising a plurality of segments shaped as elongated members of trapezoidal form in cross-section, each of which segments is joined to at least one of its neighbouring segments along a longer edge of the segment, which edge is an edge defined by the end of the longer parallel side of the trapezoid in cross-section and in which the fibres extend predominantly in directions normal to said parallel sides, with each segment comprising a plurality of stacked strips each cut from a sheet with the surfaces of the strip formed from the major surfaces of the sheet lying in substantially radial planes with respect to the axis of the annular structure and the cut surfaces defining portions of the parallel faces of a trapezoidal-form segment.

A cathodic electrode structure for a sodium sulphur cell comprising a sheet cut from a compressible block of electronically-conductive fibrous material which is chemically resistant to a hot cathodic reactant containing sulphur/polysulphides, the fibres in the block predominantly extending parallel to a given plane in the block and being randomly oriented in said plane, which block has been sliced into sheets by cutting the block in a plurality of planes normal to said one plane to form at least one sheet in which substantially all of the fibres have a component of direction normal to the plane of the sheet, the sheet having a series of parallel grooves constituted by compressed regions of fibrous material extending across a major surface of the sheet, the grooves having sloping sides defining segments of trapezoidal section between adjacent grooves with fibres lying normal to the parallel surfaces of the trapezoids between the grooves, the fibrous sheet being impregnated with the cathodic reactant.

A cathodic electrode structure for a sodium sulphur cell comprising a slice cut from a compressible block of electronically-conductive fibrous material which is chemically resistant to a hot cathodic reactant containing sulphur/polysulphides, the fibres in the block predominantly extending in one direction, which block has been sliced into sheets by cutting in a plurality of planes normal to said one direction to form at least one sheet in which the fibres lie predominantly normal to the plane of the sheet, the sheet having a series of parallel grooves with sloping sides defining segments of trapezoidal section extending across a major surface of the sheet, the grooves being constituted by compressed regions of the fibrous material, with the fibres lying predominantly normal to the parallel surfaces of the trapezoidal segments between the compressed regions, and the fibrous sheet being impregnated with the cathodic reactant.