Fig. 1

Ionic weight, cation radius and hydrated radius of typical metal-ion and non–metal ion charge carriers[4]"

Fig. 2

Overview of the content of this article[8-15]"

Fig. 3

Statistical chart of publication volume of Chinese and English papers on AZIBs (retrieved from Web of Science)"

Fig. 4

The cathode storage mechanism of aqueous zinc ion batteries (taking MnO2 as an example): (a) Zn2+ insertion/extraction[16]; (b) Zn2+/H+ co insertion[25]; (c) Chemical reaction conversion[26] and (d) Precipitation dissolution equilibrium[27]"

Fig. 5

Mechanism of Zn2+ insertion/extraction[16] (a) Cyclic voltammograms of Zn anode and α-MnO2 cathode; (b) XPS spectra of Zn 2p and (c) XRD spectra in the original sample, dissolution and embedding states of α-MnO2 cathode"

Fig. 6

Zn2+ and H+ co embedding mechanism in Zn// MnO2@CeO2 batteries[31]"

Fig. 7

The Zn2+and H+ co-embedding energy storage mechanism in Zn-VO x batteries[32] (a) Changes in Zn2+ energy spectrum during discharge process; Changes in the (b) Zn/V content ratio in the cathode material during the charging and discharging process; (c) Non in situ XRD pattern; (d) XPS spectra of O1s[13]"

Fig. 8

Chemical reaction conversion mechanism in MnO2-Zn battery[26]"

Fig. 9

(a) Zn2+ diffusion barriers and (b) Electrochemical performance in MnO2 before and after Al doping[47]"

Fig. 10

(a) XRD patterns and (b) SEM images of layered MnO2 with different cycles[51]"

Fig. 11

(a) SEM, (b) HRTEM images and (c) differential charge density of special "butterfly tie" shaped MnCO3@Mn3O4 heterostructures[55]; (e) HRTEM and (e)—(g) Zn2+diffusion energy barrier of VO-E heterostructure[32]"

Fig. 12

(a) SEM, (b) CV curves, (c) GITT tests and (d) GCD curves after various bending cycles of A-MnO2 cathodes[56]"

Fig. 13

(a) preparation process, (b) EPR spectrum, O 1s spectrum, and (d) variation of oxygen vacancy to lattice oxygen ratio of reversible manganese based cathode material rich in oxygen vacancies[58]; (e) Preparation process of NiCo2O4 cathode material rich in oxygen vacancies (Od-NiCo2O4), (f) oxygen vacancy content and (g) Co2+/Co3+ ratio at different electrochemical activation times, (h) effect of different oxygen vacancy contents on the average adsorption energy of OH-, (i) Logan curve, and (j) capacity retention rate of the entire battery after 8000 cycles[60]"

Fig. 14

(a) Preparation process, (b) Particle size, and (c) Average pore size of magnesium doped layered MnO2 cathode[51]; (d) preparation process, (e) formation energy and (f) hydrogen bonding interaction model between NH4+ and VO of V6O13 (VO-NH) cathode with ammonium intercalation[62]; (g) preparation of water molecule intercalated NH4V3O8 nano cathode[64]; (h) Double ion sequential intercalation for Li@MnVO cathode[70]"

Fig. 15

(a) Molecular structure, (b) π electron localization (ELF-π) and (c) π electron localization orbital locator (LOL-π) of TABQ-PQ molecules[52]; (d) Molecular structure, (e) LUMO/LUMO energy levels, (f) Rate performance, (g) Cycling performance and (h) Power density and energy density comparison of HATN-PNZ[30]"

Table 1

Summary of different cathode materials and performance improvement strategies for aqueous zinc ion batteries"

Fig. 16

Performance comparison of cathode materials"