Inhibition of P2-O2 Phase Transition for P2-Na2/3Ni1/3Mn2/3O2 as Cathode of Sodium-ion Battery via Synergetic Substitution of Cu and Mg

doi:10.15541/jim20240325

Abstract

Abstract:

The research of sodium-ion batteries (SIBs) is of great significance for development of new energy and energy storage methods. As cathode material, P2-type layered oxide material Na_2/3Ni_1/3Mn_2/3O₂ has attracted wide attention due to its excellent capacity and high working voltage. However, it suffers from undesired P2-O2 phase transition, which leads to a drastic change in volume and rapid capacity decay. Here, a P2-Na_0.67Ni_0.18Cu_0.10Mg_0.05Mn_0.67O₂(NCMM-10-05) cathode was synthesized through solid-state method with synergetic substitution of Cu and Mg. The results indicated that the incorporation of Cu and Mg suppressed irreversible P2-O2 phase transition when charging to high voltage and initialized OP4 phase formation, which improved reversible stability of structure. Thus the as-obtained material exhibited excellent electrochemical performance, which delivered an initial discharge capacity of 113 mAh·g^-1 in the voltage range of 2.00-4.35 V (vs. Na⁺/Na), a reversible capacity of 64.1 mAh·g^-1 at 8C (1C=100 mA·g^-1), and a capacity retention of 88.9% after 200 cycles at 1C. The effect of Cu and Mg synergetic substitution on the structure and electrochemical properties of P2-type layered oxides was explored, and the specific roles played by Cu and Mg in the structural evolution were further investigated by in situ X-ray diffraction (XRD) analysis and density functional theory (DFT) calculations. This work provides a new insight into the rational design of highly stable cathode materials with rapid Na⁺ transport capability for SIBs.

Key words: sodium-ion battery, cathode material, P2-type layered oxide, synergetic substitution

CLC Number:

O646

ZHU Zhijie, SHEN Mingyuan, WU Tao, LI Wencui. Inhibition of P2-O2 Phase Transition for P2-Na_2/3Ni_1/3Mn_2/3O₂ as Cathode of Sodium-ion Battery via Synergetic Substitution of Cu and Mg[J]. Journal of Inorganic Materials, 2025, 40(2): 184-195.

Figures/Tables 20

Fig. 1 XRD patterns and electrochemical performances of NCMM (a) XRD patterns; (b) Rate performances; (c) Cycling performances for 200 cycles at 1C

Fig. 2 Crystal structure information of NCMM-00-00 and NCMM-10-05 (a, b) Rietveld refinement results and (c, d) crystal structure diagrams of (a, c) NCMM-00-00 and (b, d) NCMM-10-05. Colorful figures are available on website

Fig. 3 Morphologies of NCMM-00-00 and NCMM-10-05 (a) SEM image of NCMM-00-00; (b) SEM, (c) HRTEM images and (d) EDS elemental mappings of NCMM-10-05

Fig. 4 Electrochemical performance of NCMM-00-00 and NCMM-10-05 (a, c) GCD curves of (a) NCMM-00-00 and (c) NCMM-10-05 at 0.2C; (b, d) CV curves for initial 3 cycles at 0.1 mV·s−1 of (b) NCMM-00-00 and (d) NCMM-10-05; (e) Cycling performance for 500 cycles at 5C of NCMM-00-00 and NCMM-10-05. Colorful figures are available on website

Fig. 5 Electrochemical performance of NCMM-00-00 and NCMM-10-05 (a, b) First-lap GITT curves of (a) NCMM-00-00 and (b) NCMM-10-05; (c) Variation of DNa+ as a function of potential determined by GITT; (d) Nyquist plots

Fig. 6 Structure evolution of NCMM-10-05 (a) In situ XRD patterns during the first and second charging/discharging cycles at 2.00-4.35 V (0.2C=20 mA·g-1); (b) Contour plots of (002) diffraction peaks; (c) P2-Z phase transition during the first cycling; (d) Evolution of lattice parameters. Colorful figures are available on website

Fig. 7 Results of DFT calculations (a) Model structures of discharging and charging states for NCMM-10-05; (b, c) Electronic localization function maps and (e, f) PDOS of (b, e) NCMM-00-00 and (c, f) NCMM-10-05; (d) Na+ migration energy barriers in NCMM-00-00 and NCMM-10-05; (g) Schematic of the orbital energy levels of Cu3d and O2p in NCMM-10-05 (EF: Fermi level); (h) Two possible local structures around Mg atom at 4.2 V. Colorful figures are available on website

Fig. 8 Crystal structure and electrochemical performance of NCMM-10-05 treated in water and air (a) XRD patterns; (b) GCD curves at 0.2C and (c) cycling performance at 1C of NCMM-10-05 after soaking in water for 24 h. Colorful figures are available on website

Fig. S1 First GCD curves of NCMM

Fig. S2 Cycling performance of NCMM-10-05 at 1C for 300 cycles

Fig. S3 (a, b) HRTEM images and (c) EDS elemental mappings of NCMM-00-00

Fig. S4 (a) P2-Z phase transition and (b) evolution of lattice parameters during the second cycling at 2.00-4.35 V(0.2C=20 mA·g-1)

Fig. S5 Model structures of discharging and charging states for NCMM-00-00

Fig. S6 Migration paths of Na+ (a) NCMM-00-00; (b) NCMM-10-05

Table S1 Compositions and electrochemical performance of NCMM samples

Sample	Composition	Q_R*(0.2C)/(mAh·g^-1)	Q_R*(8C)/(mAh·g^-1)	Capacity retention (1C, 200 cycles)/%
NCMM-00-00	Na_0.67Ni_0.33Mn_0.67O₂	150	21	69.8
NCMM-05-05	Na_0.67Ni_0.23Cu_0.05Mg_0.05Mn_0.67O₂	120	31	67.0
NCMM-05-10	Na_0.67Ni_0.18Cu_0.05Mg_0.10Mn_0.67O₂	104	49	88.5
NCMM-10-05	Na_0.67Ni_0.18Cu_0.10Mg_0.05Mn_0.67O₂	113	64	88.9
NCMM-15-05	Na_0.67Ni_0.13Cu_0.15Mg_0.05Mn_0.67O₂	99	49	74.6

Table S2 Crystal structure information of NCMM-00-00 obtained by XRD refinement

Atom	Wyckoff position	x	y	z	U_iso	Occupancy
Na1	2b	0	0	1/4	0.004	0.171
Na2	2d	1/3	2/3	1/4	0.188	0.490
Mn1	2a	0	0	0	0.013	0.668
Ni1	2a	0	0	0	0.013	0.332
O1	4f	2/3	1/3	0.42320	0.004	1

Table S3 Crystal structure information of NCMM-10-05 obtained by XRD refinement

Atom	Wyckoff position	x	y	z	U_iso	Occupancy
Na1	2b	0	0	1/4	0.051	0.245
Na2	2d	1/3	2/3	1/4	0.090	0.425
Mn1	2a	0	0	0	0.007	0.670
Ni1	2a	0	0	0	0.007	0.181
Cu1	2a	0	0	0	0.007	0.100
Mg1	2a	0	0	0	0.007	0.050
O1	4f	2/3	1/3	0.42063	0.007	1

Table S4 Impedance of NCMM-00-00 and NCMM-10-05

Sample	Resistance/Ω
NCMM-00-00	R_sf	1088
NCMM-00-00	R_ct	2638
NCMM-10-05	R_sf	596.2
NCMM-10-05	R_ct	688.5

Table S5 Bader charge analysis of NCMM-00-00

State	Type	Charge	Zval*	Valence state
Discharge	O	7.04	6	-1.04
	Ni	8.84	10	1.16
	Mn	5.27	7	1.73
Charge	O	6.84	6	-0.84
	Ni	8.71	10	1.29
	Mn	5.25	7	1.75

Table S6 Bader charge analysis of NCMM-10-05

State	Type	Charge	Zval*	Valence state
Discharge	O	7.05	6	-1.05
	Ni	8.85	10	1.15
	Cu	9.79	11	1.21
	Mg	0.35	2	1.65
	Mn	5.28	7	1.72
Charge	O	6.89	6	-0.89
	Ni	8.75	10	1.25
	Cu	9.76	11	1.24
	Mg	0.35	2	1.65
	Mn	5.25	7	1.75

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Inhibition of P2-O2 Phase Transition for P2-Na_2/3Ni_1/3Mn_2/3O₂ as Cathode of Sodium-ion Battery via Synergetic Substitution of Cu and Mg

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