Consistent with this were the EIS results, whereby the impedance of both cell types was in fact lower after 100 cycles compared with pristine (Figure ). Rather, the decay in discharge voltages was attributed to a growing heterogeneity within the LMFP electrode. When energy density retention is thus considered (Figure ), the initial advantage of the LMFP materials (~ 10 %) begins to decay immediately, and surprisingly after 100 cycles the energy density of LFP has matched that of LMFP80. While the benefit of Mn inclusion is clear, it is necessary to improve both electrode kinetics and cycling stability of these materials to provide a compelling alternative. This result also highlights the importance of calculating and presenting energy density data, as a key degradation mechanism (the voltage decay) is obscured when specific capacity alone is considered. A cathode blend material, consisting of 70% w/w LMFP60 and 30 % NMC811 was similarly examined for its potential. Also included in testing were cathodes consisting of single active materials, LMFP60 and NMC811, for reference. Figure shows voltage profiles when full cells (utilising graphite as anode) were discharged at C/20. The pure LMFP60 cell exhibited a dual plateau as above, while the pure NMC cell exhibited a more gradual slope from ~ 4.4