Polyanionic High-Voltage Cathodes

The third family of 5-V cathode materials is based on poly-anionic firameworks with the olivine and ohvine-related structures. Recently, a short review on these materials as cathodes for advanced lithium-ion batteries has been published [162]. Since the discovery of the electrochemical activity of LiMP04 

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The intercalation cathode Li MyXz (X = anion) should have a low lithium chemical potential, and the intercalation anode should have a high lithium chemical potential to maximize the cell voltage. This implies that the transition metal ion should have a high oxidation slate in the cathode and a low oxidation state in the anode. The chemical potential or redox energies of the cathode and anode could also be tuned by counter cations as illustrated by an increase in voltage on going from an oxide to a polyanion cathode with the same oxidation state for the transition metal ions. 

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