A new perspective on the composition-structure-property relationships on Nb/Mo/Cr-doped O3-type layered oxide as cathode materials for sodium-ion batteries

A High-Rate, Durable Cathode for Sodium-Ion Batteries: Sb-Doped O3-Type Ni/Mn-Based Layered Oxides

“…The morphologies of the NaNM and NaNMS samples are further characterized by field emission scanning electron microscopy (FE-SEM). As shown in Figure g, the pristine NaNM possesses large flake morphology with a particle size of 3–4 μm and a thickness of ∼500 nm, which is similar to the morphology reported in the literature . However, interestingly, after introducing Sb into the structure, the particle size of NaNMS decreased significantly to about 200 nm, even if the synthesis conditions and procedures (calcination temperature and holding time) are exactly the same as those of NaNM (Figure h and Figure S1).…”

“…As shown in Figure 1g, the pristine NaNM possesses large flake morphology with a particle size of 3−4 μm and a thickness of ∼500 nm, which is similar to the morphology reported in the literature. 45 However, interestingly, after introducing Sb into the structure, the particle size of NaNMS decreased significantly to about 200 nm, even if the synthesis conditions and procedures (calcination temperature and holding time) are exactly the same as those of NaNM (Figure 1h and Figure S1). The reduced particle size of NaNMS samples is further supported by the increased specific surface area (Figure S2), higher pore volume (Figure S3), and smaller average particle size (Figure S4).…”

“…Electrochemical performances of pristine NaNM and Sb-doped NaNMS electrodes: (a) initial three charge/discharge curves at 0.2 C rate in the potential region of 2–4.2 V; (b) d Q /d V profiles from the second reversible charge and discharge curves; (c) rate-cycle capabilities and (d) comparison of the rate capabilities of the NaNMS-1 cathode with previously reported layer cathodes for SIBs performed at the same voltage range as that used in this work ((1) O3-NaNi 0.60 Fe 0.25 Mn 0.15 O 2 , (2) O3-NaNi 0.45 Mn 0.3 Ti 0.2 Cr 0.05 O 2 , (3) O3-NaNi 0.4 Fe 0.2 Mn 0.2 Ti 0.2 O 2 , (4) O3-NaNi 0.5 Mn 0.5 Sn 0.03 O 2 , (5) O3-Na 0.98 Zr 0.02 Ni 0.5 Mn 0.5 O 2 @5%Na-Mn-O, (6) O3-NaNi 0.47 Zn 0.03 Mn 0.5 O 2 , (7) O3-Na 0.85 Li 0.1 Ni 0.18 Mn 0.54 Fe 0.18 O 1.98 , (8) P2-Na 2/3 Co 2/3 Ti 1/3 O 2 , (9) P2-Na 0.66 Co 0.9 Ti 0.1 O 2 , (10) P2-Na 2/3 Co 1/2 Ti 1/2 O 2 ); (e) cycling performances at 1 C in the potential region of 2–4.2 V; and (f) low-temperature cycling performances of NaNM and NaNMS-1 at 0.1 C in the potential region of 2–4 V.…”

“…This is similar to the Nb 5+ -and Mo 6+ -doped NaNM system. 45 Doping Nb 5+ and Mo 6+ into the NaNM system reduces the valence state of Nb 4+ and Mo 5+ in the doped materials. 45 Although there is no denying that the octahedral configurations of Ni 3+ and Mn 3+ are prone to deformation (Jahn−Teller distortion), 62 the introduction of Sb ions with larger ion radius is expected to play a positive role in stabilizing the structure.…”

“…45 Doping Nb 5+ and Mo 6+ into the NaNM system reduces the valence state of Nb 4+ and Mo 5+ in the doped materials. 45 Although there is no denying that the octahedral configurations of Ni 3+ and Mn 3+ are prone to deformation (Jahn−Teller distortion), 62 the introduction of Sb ions with larger ion radius is expected to play a positive role in stabilizing the structure. 44,63 The extended X-ray fine structure (EXAFS) spectra were converted into radial distribution functions (RDFs) by the Fourier-transformed (FT) method shown in Figure 2d−f; two main peaks are observed in the range 1−3 Å in all cases, which correspond to a single scattering path of metal and adjacent oxygen atoms (TM−O 6 ) at first coordination and interaction between metal ions (TM−TM 6 ) on the ab plane at second coordination.…”