On the Description of Electrode Materials in Lithium Ion Batteries Based on the Quantification of Work Functions

Abstract During charging of a lithium ion battery, electrons are transferred from the cathode material to the outer circuit and lithium ions are transferred into the electrolyte. Here, the energy required to take electrons and lithium ions out of two prototypical cathode materials, Li x FePO 4 and Li x Mn 2 O 4 is investigated as a function of the state of lithiation, x. Both electronic and ionic work functions vary significantly with x for Li x FePO 4 but rather little for Li x Mn 2 O 4 . The relevance of these work functions for the thermodynamic description of lithium ion batteries is discussed.