Localized Investigations of the Electrochemical Properties of Lithium Battery Materials Using Micro-Pipets

Lithium ion batteries are a commercially successful method for portable electrical energy, demonstrated by their use in portable electronics and the recent application as an alternative automotive power source to the internal combustion engine.¹ However, for lithium ion batteries to be a competitive alternative to fossil fuels in the automotive industry, electrode materials with improved capacity and charge/discharge rates are required. As new anode and cathode materials are developed² they are typically screened for advantageous properties by assembly into a working battery. This involves the fabrication of a film from a mixture of conductive material (e.g. carbon), a binder (e.g. polyvinylidene fluoride), and the active material of interest. A film is cast onto a conductive material to form the active electrode, before assembly within a coin cell. How the film is cast, the ratio of the individual components of the film, the drying procedure for the film and the final assembly of the coin cell can significantly alter the performance of the battery.^3,4 In order to avoid misleading information about the effectiveness of a novel active material many coin cells are required to validate findings.

Here we present micro-pipet measurements⁵ which demonstrate the suitability of the technique for probing lithium ion battery materials. Specifically, we probed dispersions of active materials to determine the oxidation and reduction potentials, and the charge capacity of the material. Data obtained on candidate materials by the micro-pipet method was compared to coin cell measurements, to critically assess this technique for characterisation of active battery materials.

1) Wagner, F. T.; Lakshmanan, B.; Mathias, M. F.; J. Phys. Chem. Lett., 2010, 1 (14), 2204–2219

2) Whittingham, M.S.; Chem. Rev., 2004, 104 (10), 4271–4302

3) Bruce, P. G.; Scrosati, B.; Tarascon, J.-M.; Angew. Chem.-Int. Ed. 2008, 47 (16), 2930-2946

4) Ban, C.; Wu, Z.; Gillaspie, D. T.; Chen, L.; Yan, Y.; Blackburn, J. L.; Dillon A. C.; Adv. Mater. 2010, 22, E145–E149

5) Williams, C. G.; Edwards, M. A; Colley, A. L.; Macpherson, J. V; Unwin, P. R.