Metalloid Phosphorus Doping-regulated Intrinsic Defect Engineering in High-entropy Oxides: Synergistically Enhanced Structural Stability and Reaction Kinetics

doi:10.6023/A26050161

Abstract

High-entropy oxides (HEOs) have attracted considerable attention as promising anode materials for lithium-ion batteries (LIBs) owing to their high-entropy effect, multicomponent synergistic effect, and highly tunable compositions. However, spinel-structured HEOs still suffer from sluggish electron/ion transport kinetics during lithiation and delithiation, which limits their further electrochemical performance enhancement. In this work, a metalloid phosphorus (P) doping strategy was employed to synthesize spinel-structured [P_x(Co_0.2Fe_0.2Mn_0.2Ni_0.2Zn_0.2)_1－_x]₃O₄ (x=0, 0.05, 0.10, 0.15, 0.2, denoted as Px-HEO) via a solution combustion synthesis (SCS) method, and the effects of P doping on the crystal structure, defect characteristics, and lithium-storage properties were systematically investigated. The results demonstrate that the formation of covalent P—O and P—O—M bonds promotes the generation of oxygen vacancies and induces the partial conversion of Mn^3＋ to Mn^4＋ through charge compensation, thereby effectively suppressing the Jahn-Teller effect and enhancing the structural stability of the spinel framework. Among all samples, P0.1-HEO exhibits a relatively high specific surface area (60.85 m²• g^－1) and abundant surface oxygen vacancies (50.1%), which significantly accelerate electron/ion transport kinetics. As a result, the P0.1-HEO electrode delivers a high reversible capacity of 1711 mAh•g^－1 after 250 cycles at 200 mA•g^－1 and retains a reversible capacity of 385 mAh•g^－1 even at a high current density of 3000 mA•g^－1. This study provides an experimental basis for synergistically optimizing the structural stability and lithium-storage performance of high-entropy oxide anodes through metalloid P doping.

Key words: high-entropy oxide, phosphorus doping, oxygen vacancy, structural stability, reaction kinetics

Cite this article

Shibiao Xu, Meiyi Pan, Zhengbing Wei, Feilong Yin, Mengfan Bao, Qianqian Hu, Junhao Sun, Na Lin, Aiqin Mao. Metalloid Phosphorus Doping-regulated Intrinsic Defect Engineering in High-entropy Oxides: Synergistically Enhanced Structural Stability and Reaction Kinetics[J]. Acta Chimica Sinica, 2026, 84(10): 1579-1590.

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Fig. & Tab. 11

Figure 1. (a) XRD patterns of the samples, (b) average crystallite size and lattice constants of synthesized samples, and (c~f) rietveld-refined XRD patterns

Sample	Average crystallite size/nm	Crystal lattice parameter
Sample	Average crystallite size/nm	a/nm	α/(°)	V_m/nm³	R_p	R_wp	χ²
P0-HEO	28.6	0.8365	90	0.58533	2.60	3.29	1.18
P0.05-HEO	13.6	0.8345	90	0.58114	1.67	1.23	1.52
P0.1-HEO	12.4	0.8321	90	0.57614	2.07	1.58	2.50
P0.15-HEO	10.1	0.8364	90	0.58512	1.71	1.32	1.74

Table 1. Average crystallite size and the rietveld refinement parameters

Figure 2. SEM images of the samples of (a~c) P0-HEO and (d~f) P0.1-HEO at different magnifications, (g) corresponding EDS elemental mapping of P0.1-HEO, and (h) TEM image, (i) HRTEM image and (j) SAED pattern of P0.1-HEO

Figure 3. N2 adsorption-desorption isotherms and pore diameter distribution of as-synthesized samples: (a) P0-HEO, (b) P0.05-HEO, (c) P0.1-HEO, (d) P0.15-HEO samples

Samples	S_BET/(m²•g^－1)	V_BJH/(cm³•g^－1)	D_aver./nm	D_most/nm
P0-HEO	11.31	0.06	19.74	2.59
P0.05-HEO	89.18	0.24	10.82	2.56
P0.1-HEO	60.85	0.14	9.48	2.57
P0.15-HEO	31.27	0.11	13.52	2.60

Table 2. Specific surface areas (SBET), BJH adsorption cumulative pore volumes (VBJH), average pore diameters (Daver.) and the most probable pore diameter (Dmost)

Figure 4. (a~g) High-resolution XPS spectra of synthesized samples and (h) EPR spectra of synthesized samples

Samples	Co^2＋/Co^3＋	Fe^2＋/Fe^3＋	Mn^3＋/Mn^4＋	Ni^2＋/Ni^3＋	O_V/(O_V＋O_L)
P0-HEO	32.9/67.1	47.5/52.5	54.3/45.7	54.9/45.1	25.8%
P0.1-HEO	44.1/55.9	54.9/45.1	40.8/59.2	55.3/44.7	50.1%

Table 3. Metal cation states and OV concentrations derived from XPS

Figure 5. CV curves, charge/discharge profiles and dQ/dV plots for the first three cycles of (a~c) P0-HEO and (d~f) P0.1-HEO, (g) the cycling stability and coulombic efficiency at 200 mA•g－1, (h) rate capability, and (i) prolonged cycling behavior at 1000 mA•g－1 of synthesized electrodes

Figure 6. (a) Four-probe conductivity, (b) initial impedance plots, (c) straight-line plots of ω-1/2 versus Z′ for four electrodes, (d) CV curves of P0.1-HEO at different scan rates, (e) lg ip versus lg v, (f) percentage contribution of pseudocapacitance at 1.0 mV•s－1, (g) contribution ratios of all electrodes at different scan rates, (h) charge/discharge capacity curves during the GITT measurements, and (i) lithium-ion diffusion coefficients during the charge/discharge process of as-prepared electrodes

Figure 7. (a) Ex situ XRD patterns of the P0.1-HEO electrode at different potentials, (b) differential capacity (dQ/dV) curves of the P0.1-HEO electrode at various cycle numbers, and (c, d) two-dimensional distribution maps of dQ/dV during cycling [the color scale ranges from blue (low intensity) to red (high intensity)]

Figure 8. Surface and cross-sectional SEM images of the P0.1-HEO electrode (a~c) before cycling and (d~f) after 250 cycles at 200 mA•g－1, (g) the elemental mapping of the P0.1-HEO electrode after 250 cycles, and (h, i) in situ EIS of the P0.1-HEO electrode after 250 cycles

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