Performance of porous zinc electrode in alkaline secondary battery systems suffers mainly from shape change and dendrite growth. Polyaniline coating in direct contact with porous zinc electrode was found to restrict zincate movement away from the test electrode, which otherwise may lead to a decrease in electrode surface area ͑shape change of the electrode͒ on repeated cycling. Constant current charge/discharge cycles of the blank and polyaniline-coated zinc electrodes have been carried out to assess the performance of the polymer film. It was found that a fibrous network of polyaniline coating allows OH − ions and restricts the diffusion of zincate ions.
The phase transition near room temperature in LiMnO was studied using thermal expansion measurements, and directly compared with the electrochemical performance of the material. Studies based on thermal expansion indicate the onset of a first-order phase transition at T ∼ 220 K for the nearly half-doped material, with [Mn]/[Mn] ≈ 1. The T shifts to a higher temperature, ∼290 K, and signatures for Verwey-type charge ordering at 290 K can be observed when the fraction of Jahn-Teller Mn in LiMnO is increased, i.e., [Mn]/[Mn] > 1. These studies show that the first-order phase transition near room temperature in LiMnO is associated with charge ordering, which ultimately is a consequence of the Jahn-Teller effect. In addition, the Jahn-Teller effect is proven to be an important cause of magnetoresistance and electrochemical capacity fading in LiMnO. Electrochemical measurements show that both materials, either with a T ∼ 220 K or T ∼ 290 K, exhibit capacity fading to almost the same extent. Electrochemical capacity retention is observed only in nanosized LiMnO, for which the phase transition anomalies are completely absent.
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