Background: During charge and discharge of conventional Li-ion cells, lithium ions are shuttled back-and-forth between the two insertion-based electrode materials. These processes are well understood and characterized.
In hybrid-ion cells, a non-lithium containing cathode material is coupled with a suitable lithium-based anode material such as graphite, hard carbon or lithium titanate, Li4/3Ti5/3O4. This simple but novel approach greatly increases the number of commercially useful cathode materials. By comparison with lithium, only a limited number of sodium insertion materials have been properly characterized for use in energy storage devices.
The electrochemical system is completed by the use of a conventional lithium-based non-aqueous electrolyte. During the initial charge process, Na ions are extracted from the cathode while concurrent lithium ion insertion occurs at the negative electrode. During subsequent cell discharge, lithium ions are extracted from the negative electrode while a mixed sodium/lithium insertion reaction occurs at the positive electrode. These reactions are fully reversible and in prototype cells very long lifetimes have been demonstrated. All the electroactive lithium ions in the electrochemical system originate from the electrolyte phase.
More details on this novel energy storage concept may be found below.
J. Barker et al., ESL 9, A190, (2006)
J.Barker et al., JES 154, A882, (2007)
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