| Nanometer LiMn2O4 powders were synthesized by sol-gel method using citric acid as chelating agent, which take nitrate and acetate as main raw materials respectively. LiMn1.95M0.05O4 powders were synthesized using Cr and Ni as dopant element separately. The themal behaviors of precursors were analyzed by DTA-TG. Physical properties of prepared powders were tesed by means of XRD, SEM, BET, ICP-AES, etc. Lithium polymer batteries were fabricated. Electrochemistry performances were tested and mechemisum of LiMn2O4 capacity fading was discussed. The results have shown that When the nitrate are used as raw materials, decompose of precursors mostly concentrates on from 270℃to 300℃, weight loss is relatively great, the response is more violent and more unsuitable to control.The ultimate sintering temperature should go on above 300℃. However, when raw materials are the acetate, there is a great exothermic peak made up of four parts between 300℃and 410℃. The weight loss rate drops slowly in this region, so it is easy to control steadily. The fianal sintering temperature should be above 410℃. With the increase of sintering temperature, the particle sizes and crystal lattice constants of LiMn2O4 increase and crystal lattice distortions and surface areas decrease. In addition, sintering temperature will also have bigger influence on the composition of products and it will produce impurities if the temperature control is improper. Pretreatment at the temperature of 300℃can suppress the produce of impurities and minish the size of particles. LiMn2O4 and its dopant compounds can be synthesized at the temperature of 450℃using the acetate as the main raw materials. This realizes the preparation of LiMn2O4 at low temperature and has the advantage that the dopant element can distribute evenly and metric rate can be controlled easily. The initial capacity of LiMn2O4 active material is relatively high, but structure stability is bad, during the course of charge and discharge. Transformation can produce easily, which makes intercalation and decalation of Li+ ion irreversibly and causes the capacity fading seriously. After doping a small amount of Cr3+ or Ni2+ ion in pure LiMn2O4, its spinel structure can be stabilized and Jahn-Teller effect can be suppressed, which improves cycling performance notably. However, after doping Cr3+ or Ni2+ ion, it will lose some initial capacity. The lower of the dopant amount and the dopant element chemical valence are, the greater losses of the initial capacity are.
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