Patent GB-1422292-A (GB)
Title: Electrodes for lead accumulators
IPC: H01M4/74
Filed: 1974-02-11
Abstract: 1422292 Electrode plates for lead-acid batteries BATTELLE MEMORIAL INSTITUTE 11 Feb 1974 [12 Feb 1973] 06193/74 Heading H1B An electrode comprises a glass fibre felt having impregnated therein by a filtration process a lead-based powder which after electrochemical treatment constitutes the active material. Preferably, before the impregnation step, the fibres of the felt are coated with a lead or lead alloy. In one method, Example 1, for the continuous production of positive electrodes the glass fibre felt comprises a continuous band of width 300 mm. and thickness 1 mm., the method comprising the following steps: A(ii) the fibres are metallized by projecting molten lead-antimony alloy on to both sides of the felt band while it moves between two flame-type projection units. A(iii) to permit subsequent formation of electrode contact lugs a median longitudinal zone 30 mm. wide of the metallized band is subjected to a second treatment as A(ii) and the zone is then compressed between rollers to eliminate the open pores. B(i) the band is continuously impregnated to introduce a lead-based powder into the spaces between the felt fibres. The powder consists of a mixture of PbO and Pb. B(ii) the impregnation process comprises suspending the powder in deionized water and subjecting the suspension to suction filtration through the moving band. C(i) the band is dried by passage through air and dilute H 2 SO 4  is applied to convert some of the PbO into PbSO 4 . C(ii) the band is air dried at 50‹ C. D the band is cut to form the individual electrode plates. Transverse cuts are made at intervals of 110 mm. to form plates 135 Î 110 mm. provided with a contact lug 30 Î 15 mm. at one corner, this lug being in the zone formed in A(iii). E the electrode plates are stored in a conditioning tank for 24 hours in air at 50‹ C. and 50% relative humidity to oxidize the metallic lead and tribasic lead sulphate is formed in the spaces between the felt fibres. F the plates are subjected to a normal formation process in a bath of H 2 SO 4  in which the PbO and PbSO 4 , 3PbO are converted to lead dioxide constituting the positive active material. Example 2. In this method for producing negative electrodes the band is 0À8 mm. thick and is dried before the corresponding step A(ii) of Example 1 in which the fibres are metallized by the projection of molten lead. In step A(iii) lead powder is applied to the median zone by dry suction followed by local heating to melt the lead in this zone. The powder mixture of PbO and Pb of steps B(i), B(ii) is applied by dry suction and the band is subsequently moistened with de-ionized water to retain the powder. Steps C(i), C(ii), D, E and F follow as in Example 1 but in step F the PbO and PbSO 4 , 3PbO are converted into spongey lead to form the negative active material. In Examples 3, 5 the glass fibre band is 900 mm. wide and is formed with three longitudinal zones for the electrode contact lugs whereby six electrode plates are produced by each lateral cut. In Example 3 for producing positive electrodes, the powder mixture of steps B(i), B(ii) comprises lead and lead-antimony alloy. Example 5 is intended for producing negative electrodes as in Example 2, but these electrodes may be subjected to a second formation process in H 2 SO 4  of lower density and with reverse current so that some of the metallic lead is converted into lead sulphate and then into lead dioxide serving as positive active material. In Example 4, for producing negative electrodes, the glass fibre felt is initially in the form of strips 300 mm. wide and 1100 mm. long, these strips being arranged side-by-side and movable together during the process steps.