Blending Lithium Nickel Manganese Cobalt Oxide with Lithium Iron Manganese Phosphate as Cathode Materials for Lithium-ion Batteries with Enhanced Electrochemical Performance

The effects of LiMn0.7Fe0.3PO4/C (LMFP) species on the electrochemical performance of the blended cathodes of LiNi0.5Mn0.3Co0.2O2 (NMC) and LMFP are examined. Two types of LMFPs are synthesized by the hydrothermal method (LMFP-1) and the solid-state reaction (LMFP-2) leading to different physical characteristics and uniformity of primary particles. The blended cathodes of NMC and LMFP-1 show higher discharge capacity, gravimetric energy density, and rate capability than those of NMC and LMFP-2 for the same blending ratio (10, 20, 30, 40, and 50 wt% LMFP to NMC) because of the differences in the electronic conductivity, specific surface area, mean particle size, and uniformity of primary particles between LMFP-1 and LMFP-2. The discharge capacity and gravimetric energy density of NMC : LMFP-1 = 9 : 1 and 8 : 2 at 0.2 C-rate are comparable to those of NMC. Further, the rate capability is the highest at the blending ratio of NMC : LMFP-1 = 7 : 3. An optimal range for the blending ratio of LMFP to NMC is revealed based on the discharge capacity, energy density, and rate capability of the blended cathode. Moreover, LMFP has a considerable impact on the electrochemical characteristics of the blended cathodes of NMC and LMFP.