Lithium-ion batteries continue to be utilized as the energy source for mobile applications, but increases in their performance and long-term stability are areas which need continued research. Very thin ALD Al2O3 films (2-8 cycles) have been recently shown to drastically improve the capacity retention of cathode material, such as lithium cobalt oxide, LiCoO2 from 45% to 89% after repeated cycling.1 XRD studies show that Al2O encapsulates LiCoO2 preferentially over binder material such as poly(vinylidene)fluoride or conductive carbon.2 The ability of ALD layers to prevent the electrodes from corrosion with just a few cycles is an area of active research. Indeed, ALD films can used to improve performance by optimizing the interfaces between different components in batteries.
Creating a Li-ion 3-D solid state battery with ALD is an attractive option for increasing the energy density and decreasing losses from ion diffusion lengths. This has been enabled by the discovery of a suitable LiO ALD precursor/process.3 Lithium lanthanium titanate is an attractive material for replacing the lithium phosphorous oxynitride solid electrolyte.4 Other potential electrolyte materials include LiLaMOx where M= Zr, Ta, Nb, LiVO3, or LibNbO3. Anode materials such as TiO2, ZnAl2O4, ZnCo2O4, Co3O4 or ZnMgO4 can also be fabricated and tuned by ALD processes. ALD processes for metallic Pt and Pd can allow for the formation of current collectors. Similarly, diffusion of Li out of the electrolyte/cathode stack can be prevented by using a TaN or TiN to prevent damage to the substrate.
(1) Jung, Y. S.; Cavanagh, A. S.; Dillon, A. C.; Groner, M. D.; George, S. M.; Lee, S. H. J Electrochem Soc 2010, 157, A75.
(2) Lee, J. T.; Wang, F. M.; Cheng, C. S.; Li, C. C.; Lin, C. H. Electrochimica Acta 2010, 55, 4002.
(3) Putkonen, M.; Aaltonen, T.; Alnes, M.; Sajavaara, T.; Nilsen, O.; Fjellvag, H. J Mater Chem 2009, 19, 8767.
(4) Aaltonen, T.; Alnes, M.; Nilsen, O.; Costelle, L.; Fjellvag, H. J Mater Chem 2010, 20, 2877.