Negative electrodes testing

During the first trials with synthetic separators around 1940 it had already been observed that some of the desired battery characteristics were affected detrimentally. The cold crank performance decreased and there was a tendency towards increased sulfation and thus shorter battery life. In extended test series, these effects could be traced back to the complete lack of wooden lignin, which had leached from the wooden veneer and interacted with the crystallization process at the negative electrode. By a dedicated addition of lignin sulfonates — so called organic expanders -— to the negative mass, not only were these disadvantages removed, but an improvement in performance was even achieved. 

The above comparative evaluation of starter battery separators refers to moderate ambient temperatures the standard battery tests arc performed at 40 or 50 °C. What happens, however, on going to significantly higher temperatures, such as 60 or 75 °C This question cannot be answered without considering the alloys used batteries with antimonial alloys show a water consumption that rises steeply with increasing temperature [40], leaving as the only possibilities for such applications either the hybrid construction, i.c., positive electrode with low-antimony alloy, negative electrode lead-calcium, or even both... 

In our tests, we used pasted mixtures of carbon-carbon electrode components with KOH solution having a density of 1,26 g em"3. Positive and negative electrodes were pasted onto the conductive polymer film, separated by ionoconductive separator, made out of special paper, pressed between external collectors of nickel-plated copper with pressure of 8 kgf-ern 2. 

Mix Penetration Strength. The force required to create a short through a separator due to mix (electrode material) penetration defines mix penetration strength. In this test force (with a /z in. diameter ball) is applied on the positive electrode/ separator/negative electrode sandwich, and the force at which the mix penetrates through the separator and creates an electronic short is called mix penetration force. Mix penetration strength is used to indicate the tendency of separators to allow short-... 

To test the fit, place the nipple on the bottom flange with a Teflon flange gasket and the negative electrode in place. Place a Teflon gasket on top of the screw flange and slip the felt into the coupler. 

An ionic EAP based actuator (3.16 g), with an embedded spiral stainless steel wire as the positive electrode and an external platinum negative electrode, was mechanically tested isometrically with a 587.7 mg counterweight. The experimental design used a Mettlar analytical balance and a pulley system (Fig. 4.24). The isometric mechanical testing of an activation-relaxation cycle is shown in Fig. 4.25. This was a fairly large actuator. We have observed that the smaller the actuator, the faster and more pronounced the contraction. 

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