Lithium-cobalt oxide

Other sohd cathode systems that have been widely investigated include those containing lithium cobalt oxide [12190-79-3] LiCo02 (51), vanadium pentoxide [1314-62-17, 20, and higher vanadium oxides, eg, 0 3 (52,53). 

Kim KH, Kim KB (2008) Ultrasound assisted synthesis of nanosized lithium cobalt oxide. Ultrason Sonochem 15 1019-1025... 

Julien, C., Camacho-Lopez, M. A., Mohan, T., Chitra, S., Kalyani, P., Gopukumar, S., Combustion synthesis and characterization of substituted lithium cobalt oxides in lithium batteries, Solid State Ionics 135, 241-248 (2000). 

The energy density of commercial cells has almost doubled since their introduction in 1991 since 1999 the volumetric energy density has increased from 250 to over 400 Wh/1. Details of the original commercial cells have been reviewed by Nishi, where key aspects are discussed concerning the need for large particle size, 15—20 /increase safety and the intentional incorporation of lithium carbonate into the cathode to provide a safety valve. The lithium carbonate decomposes, releasing carbon dioxide when the charging exceeds 4.8 V, which breaks electrical flow in the cell. These lithium cobalt oxides also contain excess lithium and can be best represented by the formula... 

Finally, Al (/= 5/2) and Co NMR spectroscopy have been used to probe AP+ in Al-doped lithium cobalt oxides and lithium nickel oxides. A Al chemical shift of 62.5 ppm was observed for the environment Al(OCo)e for an AP+ ion in the transition-metal layers, surrounded by six Co + ions. Somewhat surprisingly, this is in the typical chemical shift range expected for tetrahedral environments (ca. 60—80 ppm), but no evidence for occupancy of the tetrahedral site was obtained from X-ray diffraction and IR studies on the same materials. Substitution of the Co + by AF+ in the first cation coordination shell leads to an additive chemical shift decrease of ca. 7 ppm, and the shift of the environment A1(0A1)6 (20 ppm) seen in spectra of materials with higher A1 content is closer to that expected for octahedral Al. The spectra are consistent with a continuous solid solution involving octahedral sites randomly occupied by Al and Co. It is possible that the unusual Al shifts seen for this compound are related to the Van-Vleck susceptibility of this compound. 

Gummow R.J., Liles D.C., Thackeray M.M. and David W.I.F. A reinvestigation of the stmctures of lithium-cobalt-oxides with neutron-diffraction data. Mat. Res. Bull. 1993 28 1177-84. 

The first investigation of Li Co02 was carried out by Mizushima et al. in 1980," where the material was suggested as a possible positive electrode for lithium-ion rechargeable batteries. In 1991 Sony Corporation commercialized the first lithium-ion battery in which lithium cobalt oxide was used as the positive electrode and graphite (carbon) as the negative electrode. Since then, LiCo02 has been the most widely used cathode material in commercial hthium-ion batteries and retains its industrial importance as a cathode material. 

Various materials are used for production of the three main components of a lithium ion battery. Research and development of these materials is where the automotive chemist is severely needed. The main components of the battery are the electrolyte, cathode, and anode. For the cost imperative, graphite is used most often in the anode. The cathode is typically a layered lithium cobalt oxide, lithium iron phosphate, or lithium manganese oxide. Other materials, such as TiS2, have been used [18]. Of course, properties vary depending on the choice of anode, cathode, electrolyte, etc. 

A fully charged battery spontaneously produces an electric current and, therefore, power when its positive and negative electrodes are connected in an electrical circuit. The positive electrode is called the anode, and the negative electrode is called the cathode. The materials used for the electrodes in lithium ion batteries are under intense development. Currently the anode material is graphite, a form of carbon, and the cathode is most frequently LiCo02, lithium cobalt oxide ( FIGURE 7.8). Between anode and cathode is a separator, a solid material that allows lithium ions, but not electrons, to pass through. 

At the cathode, lithium ions then insert in the oxide materiaL Again, the small size of lithium ions is an advantage. For every lithium ion that inserts into the lithium cobalt oxide cathode, a ion is reduced to a Co by an electron that has traveled through the external circuit. 

As mentioned above, LMO is expected to be cost-effective. However, there are some problems in that LMO has less capacity than lithium-cobalt oxide (LCO), and manganese dissolves from LMO into organic electrolytes, resulting in degradation of performance at high temperatures. We have been attempting to resolve these problems by stabilization of the crystal structure and reduction of the specific surface area. 

Y. Iriyama, H. Kurita, I. Yamada, T. Abe, Z. Ogumi, Effects of surface modification by MgO on interfacial reactions of lithium cobalt oxide thin film electrode, J. Power Sources 2004, 137, 111-116. 

Fig. 10.8 Typical charge/discharge characteristics of lithium cobalt oxide (LiCo02> positive electrode material. Charging corresponds to lithium deintercalation, and discharging refers to lithium intercalation...

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