Effects of Partial Acid Delithiation on the Electrochemical Lithium Insertion Properties of Nickel-Stabilized LiMn2O4 Spinel Oxides
✍ Scribed by P. Lavela; L. Sánchez; J.L. Tirado; S. Bach; J.P. Pereira-Ramos
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 202 KB
- Volume
- 150
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Use of nickel-containing LiMn 2 O 4 up to 20 at.% as an insertion electrode in lithium cells combined with preliminary acid treatment results in improved cycling performance. An increase in the average oxidation state of manganese, a decrease in the Li/Mn ratio, partial H ؉ /Li ; exchange, and a decrease in the unit cell parameters of the solid products take place during treatment with aqueous HNO 3 . X-Ray di4raction line broadening analysis shows that for a sample with a Ni/Mn ratio of 0.25 and a temperature of preparation of 8003C, crystallinity increases slightly with acid treatment, as a result of the dissolution of the external layers of the solid in which defects concentrate. For samples prepared below 8003C an increase in line broadening associated with a larger extension of the cation-exchange process is observed. The use of acid-treated solids in lithium cells results in higher capacities and better capacity retention as compared with pristine spinels. Larger capacities are always observed for samples prepared at 5503C and a Ni/Mn ratio of 0.11. The role of nickel is of particular interest in stabilizing the spinel structure and allowing high average oxidation states of manganese in the solid.