On The Optimization Of Prescription Of The Negative Electrode For Ni/MH Battery

Ni/MH battery is regarded as the third generation of practical secondary battery with high price rate compared with the batteries of the other series. MH electrode, as the negative electrode, has the great important influence on Ni/MH battery. Optimization of prescription especially additives, conductors and binders of the negative is an efficient and economical approach to improve the performances of Ni/MH battery during the high rate discharge phase, but till now the related studies are not enough. Therefore, on the basis of detailed review of research on prescription of MH electrode at home and abroad, faced to the application of D type power battery, effects of prescription of MH electrode on the performance of the negative electrode for Ni/MH battery are investigated by the open cell method.The electrochemical properties of MH electrode with the addition of rare earth oxides and mixture of CoO and CoO2 are studied. The rare earth oxides, as additives to the negative electrode, have not been reported in open literature. The results show: La2O3, CeO2, Nd2O3 is applicable for the additives of MH electrode because of the good comprehensive performance of the negative especially during the high rate discharge phase; Y2O3 is not fit as an additive for MH electrode; the CeO2 content in negative has great effects on the performance during the high ratedischarge phase and 2%(mass percentage) is the best one, furthermore, the improvement of purity of CeO2 is beneficial to the comprehensive performance; the mixture of CoO and CeO2 as a additive is more suitable for MH electrode during the high rate discharge phase whose properties are better than that of addition of CoO and CeO2 respectively.The effect of the nickel powder with various particle size and content on the electrochemical properties as a negative conduct electricity material for Ni/MH battery was researched. The results show that: nano-nickel powder is not useful for MH electrode during the high rate discharge phase as a conductor or additive; superfine nickel powder is applicable for the conductor of the negative because of the good performance especially the cyclic stability at 1C rate by using 5% (mass percentage) nickel powder; the utilization of alloy, specific mass and volume capacity are increased with the decreased particle size of nickel powder in negative, however, the capacity fading rate at 1C discharge rate is also increased, so the capacity and the cyclic stability should be taken into account to make a choice of the particle size.The combination of hydrophilic and hydrophobic materials for MH electrode as a binder is investigated. The results show: the MH electrode bonded with the blend of PVA, CMC and NL in a proper proportion possesses the best comprehensive performance and 0.3% (mass percentage) is the proper quantity of NL for the prescription. The two prescriptions that HPMC or HEC respectively blended with NL demonstrate the different comprehensive performance and the former is better than the latter, but they are not good as NL with PVA blended; CMC and HEC blended with PTFE have worse performances than that blended with NL; compared with the binders of NJL and NL, NJL is beneficial to the electrochemical properties and disadvantagous to the electrode's formation, but NL is the very contrary.