A SYSTEMATIC STUDY OF INTERCALATION COMPOUNDS AS CATHODE MATERIALS FOR LITHIUM BATTERIES.
Three types of intercalation Compounds, LiMn{sub 2}O{sub 4} with spinel structure, LiNiO{sub 2} and LiCoO{sub 2} with layered structure are widely studied as cathode materials for lithium-ion batteries. Among them, LiCoO{sub 2} is the most widely used cathode material in commercial lithium battery cells. LiNiO{sub 2} has same theoretical capacity as LiCoO{sub 2}, but is less expensive. However its application in lithium batteries has not been realized due to serious safety concerns. Substituting a portion of Ni in LiNiO{sub 2} with other cations has been pursued as a way to improve its safety characteristics. It was reported that Co doped LiNi{sub 0.8}Co{sub 0.2}O{sub 2} showed better thermal stability than pure LiNiO{sub 2}. Many new materials have been developed aimed in increasing the capacity and improving the thermal stability and cyclability. Most of these new materials are based on these three types of materials and modified their compositions and structures by doping. However, most of the efforts on developing new cathode materials have been done on the empirical base without guidelines from the systematic studies on the relationship between the performance and the structural changes of the cathode materials. Exploring this relationship is very important not only in guiding the development of new materials, but also in improving the performance and safety aspect for the existing cathode materials for lithium ion batteries. Using conventional x-ray source and a specially designed battery cell with beryllium windows, Dahn and co-workers have published several papers on the structural changes of LiNiO{sub 2} cathodes 1 and LiCoO{sub 2} cathodes 2 during charge. Unfortunately, the charging voltage was limited to below 4.3 V due to the problem of beryllium window corrosion at higher voltage. However, the voltage range between 4.3 V and 5.2 V is the most important region for studying the relationship between the thermal stability and structural changes during charge, because the thermal instability occurs at the overcharged state of the cathodes. Taking advantage of the strong x-ray beam from a synchrotron light source, we have constructed lithium battery cells for in situ XRD study with Mylar windows replacing the beryllium windows. Using the state of art synchrotron based in situ XRD technique, new phases and new phase transitions during charge have been observed in all of these three systems. These new phases and phase transitions have not been reported or correctly identified in the literature. The relationship between the performance (capacity, thermal stability and cyclability) and the structural changes during cycling has been thoroughly studied. The results of these studies will be summarized in this presentation.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 781372
- Report Number(s):
- BNL-68294; KC0203010; R&D Project: EST114NEEA; KC0203010; TRN: AH200123%%407
- Resource Relation:
- Conference: PROCEEDINGS OF THE CHINA INTERNATIONAL BATTERY FAIR 2001, BEIJING (CN), 06/08/2001--06/12/2001; Other Information: PBD: 8 Jun 2001
- Country of Publication:
- United States
- Language:
- English
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