Patent GB-191207253-A (GB)
Title: Lead Storage-battery Electrodes, and Processes of Making them.
Inventor: MORRISON WILLIAM
IPC: H01M4/68
Filed: 1912-03-25
Granted: 1912-09-19
Abstract: 7253. Morrison, W. March 25. Electrodes for lead accumulators. Grids consist of an alloy of lead, selenium, or tellurium, and a hardening-metal such as antimony, made preferably by adding lead to an alloy of the other two components. Positive electrodes contain as a binding-agent one or more compounds of tantalum, niobium, or tungsten especially a compound of lead, as a base, with one of these metals, oxygen, and sulphur. The binding- compound may be produced in a pasted plate by electrolysis, and this method may be used subsequently and in addition to others described below. Plates pasted with a usual mixture of minium, litharge, and sulphuric acid, in which lead sulphate is produced as a temporary binder, preferably are first fully peroxidized by repeated reversal of current in acid of sp. gr. 1À2-1À25 followed by a passage of current in water, and a subsequent rinsing, to remove free acid. ' Forming ' may instead take place afterwards, but requires more current. The plates are next made anodes in a solution of potassium hexatantalate for instance, whereupon the lead sulphate is converted into the required leadtantalum compound. After being rinsed and placed in acid of sp. gr. 1À3 until free from soluble matter, the plates are discharged in acid of sp. gr. 1À28, and then recharged, preferably not quite to full capacity in order that some lead sulphate may remain for conversion into more of the tantalum compound if desired. In the above ' forming ' operations, empty grids are used as dummies, the presence of the tantalum compound rendering reversal of the polarity undesirable because of local action. In a modification, 6-10 per cent of the required compound, prepared separately, may be ground with the minium-litharge paste, the plates, which may be thick, being given a prolonged strong ' forming.' The compound may be made by precipitating a lead solution such as the nitrate or acetate by the addition of a solution of sodium paratungstate, or potassium hexatantalate or hexaniobate, washing the precipitate with dilute sulphuric acid, boiling in strong sulphuric acid, washing in water, and optionally heating. In another modification, sulphuric acid is added slowly to a solution of sodium paratungstate and hydrogen peroxide until gas ceases to be evolved, and then further in an equal amount, and the plates are dipped in this liquid and dried repeatedly, after which they receive a prolonged strong charging. The plates may first be ' formed,' or this may be done afterwards with more current. Sodium tantalate or niobiate may be used similarly. In another modification, the plates are dipped in sodium tungstate solution and dried, and may then either be made anodes in water which may contain a little caustic soda, a lead-tungsten-oxygen compound being produced; or be dipped in sulphuric acid containing, for instance, hydrogen peroxide to reduce the lead peroxide so that lead sulphate can be formed, or in hydrogen peroxide solution and then in sulphuric acid, to produce a lead - tungsten - sulphur - oxygen compound. These treatments may be repeated, and compounds of tantalum and niobium may be obtained similarly.