Investigations of the structure, electrochemistry, and processing of the layered lithium cobalt dioxide lithium intercalation host material

While LiCoO{dollar}sb2{dollar} has been widely studied in the past 14 yrs. as a promising positive electrode material in lithium-ion batteries, surprisingly, many questions are still unanswered concerning the electrochemical and structural characteristics of the lithium intercalation material. One of these unanswered questions concerning LiCoO{dollar}sb2{dollar} concerns the existence of an endmember CoO{dollar}sb2{dollar} phase upon complete lithium deintercalation. The use of dry plastic lithium ion battery technology has allowed the construction of a new in-situ X-ray diffraction cell which facilitates structural characterization of LixCoO{dollar}sb2{dollar} at x values at and close to 0 for the first time. Instead of the expected destruction of the core structure of LiCoO{dollar}sb2{dollar}, the end member CoO{dollar}sb2{dollar} phase was isolated. This phase was a hexagonal single layered phase with lattice parameters of a = 2.822 A and c = 4.29 A. Cycling properties were maintained when cycled back to 4.2V.; As with all ceramic materials, significant savings in processing costs can be realized with a reduction in fabrication temperatures. Crystalline LiCoO{dollar}sb2{dollar} was fabricated at 100{dollar}spcirc{dollar}C, a reduction in fabrication temperature of almost 800{dollar}spcirc{dollar}C, through the use of an ion exchange reaction between CoOOH and an excess of LiOH{dollar}rmcdot Hsb2O.{dollar}; While LiCoO{dollar}sb2{dollar} has a large theoretical capacity of 274mAhr/g, only 50% of it may be used for commercial applications due to rapid fade in capacity with cycle number. Quantitative analysis revealed a strong and direct correlation between the percentage capacity loss and percentage cobalt loss. The quantity of cobalt dissolution was found to correlate well with structural changes above 4.2V. The cycling properties were optimized at higher capacities through an in depth study of the effect of processing conditions and lithium stoichiometry. Stabilization of {dollar}rm Lisb{lcub}x{rcub}CoOsb2{dollar} at high capacities was introduced by a brief thermal anneal at 1000{dollar}spcirc{dollar}C.