
248 Electrochemically Enabled Sustainability
tunnel along the b-axis (connecting Na1 sites) shows an exceptionally low acti-
vation barrier (<300 meV). These activation barriers are comparable to those
of lithium ions in conventional cathode materials (Table 6.6). These low acti-
vation barriers imply that sodium can easily diffuse through all directions.
In light of the promising prediction from rst-principles study [56],
Na
4
Fe
3
(PO
4
)
2
(P
2
O
7
) was experimentally synthesised and shown that revers-
ible Na intercalation was possible at predicted voltages.
In this section, it was shown that rst-principles studies could provide the
basic electrochemica ...