Figure 7. Performances of C/P2-Na0.67[Fe0.5Mn0.5]O2 Na-ion cells.
The voltage-composition profiles are reported for the two first cycles for cells using (a) as-made P2-Na0.67[Fe0.5Mn0.5]O2 (cell D1), (b) P′2-Na1[Fe0.5Mn0.5]O2 made by Na ball milling (cell D2) and (c) for a P′2-Na1[Fe0.5Mn0.5]O2/Na3P composite (cell D3) as positive electrode. The negative electrode is C. The weight ratio of positive to negative electrode is 2.6, 1.6 and 1.4 for D1, D2 and D3 cell, respectively. The cells were cycled at 0.1 C rate. The capacity is based on the weight of positive materials, including Na3P for D3 cell. The capacity retention of D1, D2 and D3 cell is given (d), and e shows the first charge profile of a C/Na3P cell. For all cells a 1 M NaClO4 in EC/DMC (50/50 by volume) electrolyte was used.