High Performance Positive Electrode

Conventional lead-acid batteries contain a positive electrode (Pb02 plate) and a negative electrode (Pb plate) immersed in a sulfuric acid electrolyte and having a separator interposed between each plate. Such electrodes are typically made by applying a paste containing lead oxides and lead sulfates to the surface of a battery plate and electrochemically forming the paste into an active material. 

Conventional pastes for use in making automotive batteries contain lead oxide in the range of 15-30%, sulfuric acid, water and additives such as fiber and expanders. Such pastes are usually made by adding the sulfuric acid and water to a mixture of lead and lead oxides. As a result of the chemical reaction during mixing, a portion of the lead and PbO is initially converted to lead sulfate (PbS04) and the resultant positive paste becomes a heterogeneous mixture of lead, lead oxide, lead sulfate and basic lead sulfates. 

The use of pre-sulfated paste materials containing basic lead sulfate, e.g., tribasic and tetrabasic lead sulfates (3PbO x PbS04 x H2O and 4PbO x PbS04) made in dry form prior to forming the paste has also been proposed to improve the efficiency of the paste (13). 

monobasic lead sulfate has been used as a pre-sulfated paste material (14). However, positive plates prepared from such pre-sulfated paste mixes are difficult to form and must usually be cured for at least 24 hours before being formed (15). It is also known that reacting lead oxide with ozone forms improved lead oxides useful as active materials in batteries (16). 

It has been shown that the surface area increase is directly related to the presence of a hydrogen bonding solvent, typically water, for ozone, and that an increase in surface area is obtained with higher ozone concentration (17,18). Several attempts have also been made to improve the conductivity of the paste through use of persulfate treatments (19). 

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Z.S. Wronski, G.J.C. Carpenter, P. Kalal, An integrated characterization approach for ranking nickel hydroxides designed for high-performance positive electrodes in batteries for electric vehicles, Electrochem. Soc. Proc. 96-14 (1996) 177-188 (Exploratory R D of Batteries for Electric and Hybrid Vehicles, A.R. Langrebe and B. Serosati, eds.)... 

W.-H. Kao, N.K. Bullock, and R.A. Petersen, High performance positive electrode for a lead-acid battery, US Patent 5 302 476, assigned to Globe-Union Inc. (Milwaukee, WI), April 12,1994. 

Among the transition metal oxides, mention should also be made of the vanadium oxides, the most studied as positive electrode materials being V2O5, V Oii, and LiV30g, which insert lithium in the potential domain of 3 V vs. Li/Li+. For the vanadium oxides, too, doping and suitable structure have been shown to improve their electrochemical performance, and recently a sol-gel process has yielded high-capacity (500-600 Ah kg ) materials delivering 500 Wh kg at 4 mA cm" [137]. 

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