Materials for lithium ion batteries
|Ludwika Lipińska , Monika Michalska , Ryszard Diduszko , Monika Mirkowska|
Institute of Electronic Materials Technology (ITME), Warszawa 01919, Poland
In recent years most of the researches on novel electrode materials for Li-ion rechargeable batteries have been concentrated on phosphoolivines and oxides of the spinel structure. There is a significant interest in structural properties of these materials because electrode capacity and battery performance depend mostly on the rate of lithium diffusion and electron transport. Phosphates – olivines have excellent structural stability (strong bonds: P-O), good cycle life, thermal and chemical stability and are safe . Lithium iron phosphates LiFePO4 have good lithium intercalation properties, high specific stored energy, and excellent charge/discharge reversibility. LiMnPO4 has a redox potential of 4,1 V versus Li+/Li which is considered to be the maximum limit accessible to the most liquid electrolytes.
Also, lithium manganese oxide (LiMn2O4) spinel has been extensively studied as a cathode material for Li-ion batteries. Application of LiMn2O4 has several advantages like: low cost, easy preparation, non-toxicity, high potential (4V vs. lithium metal), a satisfactory capacity, high-energy density, low self-discharge and high thermal stability. In spite of these advantages, LiMn2O4 suffers from a serious capacity fading during charge-discharge cycles, which is unacceptable in commercial applications. This problem can be caused by several factors: manganese dissolution, electrolyte decomposition at high potentials, the Jahn-Teller distortion at the state of a deep discharge and lattice instability. There are various strategies to improve structural stability of LiMn2O4. One of them is a partial substitution of manganese ions by other divalent or trivalent metal elements e.g. Fe, Co, Ni, Al. Another way is to use nonstoichiometric lithium manganese spinel like – Li1+xMn2-xO4. Recently, a new class of anode materials – lithium titanium oxide (Li4Ti5O12) of the spinel structure is investigated. This compound is very suitable for LiMn2O4 used as cathode.
We succeeded in obtaining nanocrystalline compounds of olivine and spinel structures by modified sol-gel method. Examples are: olivins – LiFePO4, LiMnPO4  and spinels: LiMn2O4 (stoichiometric, nonstoichiometric and substituted) [3,4] and Li4Ti5O12.The details of sol-gel synthesis will be presented at the Symposium. All mentioned above compounds are safe (resistant to uncontrolled oxidation) and environment friendly.
As-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and simultaneous thermal analysis (differential scanning calorimetry DSC and thermogravimetry TGA). All obtained materials were single phase and with nano size of crystallites. Application of nanocrystalline electrode materials has many additional advantages: high surface area, new active reactions, decrease the path length for Li ion transport, reduce the specific surface current rate, improved stability, enhanced specific capacity. The modified sol-gel synthesis turned out to be a very effective way for production of the electrode materials for lithium ion batteries.
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 K. P. Korona, J. Papierska, M. Kamińska, A. Witkowski, M. Michalska, L. Lipińska: Raman measurements of temperature dependencies of phonons in LiMnPO4, Materials Chemistry and Physics 127 (2011) 391-396.
 M. Michalska, L. Lipińska, M. Mirkowska, M. Aksienionek, R. Diduszko, M. Wasiucionek: Nanocrystalline lithium-manganese oxide spinels for Li- ion batteries – sol-gel synthesis and characterization of their structure and selected physical properties, Solid State Ionics, 188 (2011) 160-164.
 Monika Michalska, Ludwika Lipińska, Ryszard Diduszko, Marta Mazurkiewicz, Artur Małolepszy, Leszek Stobinski, Krzysztof J. Kurzydłowski: Chemical syntheses of nanocrystalline lithium manganese oxide spinel, Physica Status Solidi C 8, No. 7-8, 2538-2541 (2011) /DOI 10.1002/pssc.201001195.
Presentation: Invited oral at Warsaw and Karlsruhe Nanotechnology Day, by Ludwika Lipińska
See On-line Journal of Warsaw and Karlsruhe Nanotechnology Day
Submitted: 2011-08-29 15:33 Revised: 2011-08-31 14:00