Negative active materials

Tin, tin-based alloys, lithium-ion batteries, negative active material... 

Fig. 38. Symmetrical combinations of positive and negative active materials, PA and NA, in (1) conventional accumulators, (2) swing accumulators and (3) electrochemical double layer capacitors. The relative electrolyte (E) volume is shown schematically. The thick, vertical lines represent the current collector (schematically).

One of the main reasons for the high power capability of the lead-acid battery is the high conductivity of the active materials. Lead dioxide is a semiconductor with a conductivity of up to 10 (Q cm) at room temperature, while 35% sulfuric acid has a conductivity of 0.8 (Q cm) Lead, which is a metallic conductor, is used for both the current-collector and the negative active-material. Because of the high conductivities of these materials, a fully charged lead-acid battery has a resistance of only a few mQ. 

Fig. 5.1. Utilization of negative active-material at various plate thicknesses.

Fig. 5.5. Gassing on negative active-material made from primary and secondary lead.

The utilization of negative active-material at three discharge rates was determined, and Table 5.3 shows the range of mean values for plates made with 0.22 wt.% carbon black, 0.8 wt.% barium sulfate, and three levels of the experimental materials. The data have been normalized to eliminate small variations in paste weight. At... 

Table 5.4. Additives with highest utilization of negative active-material at 5.7 mAcm...

Firefly Energy (USA) used carbon foam instead of a lead grid to hold the negative active material and to maintain a stable 3D structure of NAM with widely open pores [82]... 

Sulfuric acid is consumed dining battery discharge and is then restored during charge. These processes are reversible as far as H2SO4 is concerned because it does not change its structure as do the positive and negative active materials. 

The influence of poly(N-vinylpyrrolidone) polymers (PVP) as electrolyte additives on the performance of lead—acid batteries has been studied, but controversial results are reported by different research groups depending on the molecular weight and concentration of the polymer used. The application of PVP as additive to the positive or negative active materials is probably more effective than if added to the electrolyte. 

A well-balanced expander formulation, containing the above three components, guarantees good performance of the negative active material, especially at low temperatures. A typical expander formulation used in the battery industry is 0.2—0.3% lignosulfonate, 0.8—1.0% BaS04, 0.1—0.3% carbon black, all calculated in weight percent vs. the leady oxide used for paste preparation. 

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