35
ence a phase transformation into Zn-birnessite during electrochemical cycling in
ZIBs [47, 48].
Interestingly, all polymorphs of manganese oxide cathodes and spinel-type
ZnMn 2 O 4 cathodes were reported for ZIBs. Table 1 describes the electrochemical
performances of some prominent oxide materials in different electrolytes; it also
includes preparative techniques of the cathodes, concentration of the electrolytes,
additives and potential window employed for the respective ZIBs. For example, concentration dependent MnSO 4 used as an additive in zinc electrolyte can alter the
electrochemical reaction path in the Zn-MnO 2 system. In addition, the reversible
deposition/dissolution of MnO 2 on the surface of cathode through electrolytic manganese dioxide (EMD) is also accounted. This infers a complicated electrochemical
mechanism proven in Zn-MnO 2 battery system, thereby strongly questioning the role
of the additive to just the compensation of Mn
2+
dissolution from the cathode [59].
Considering that the present-day portable electronics industry is upgrading to
next-generation technologies including wearable batteries, the prospects for all
solid-state ZIBs based on aqueous electrolytes and manganese-based electrodes are
significant due to their cost-effective, nontoxic, extremely safe, high potential, high
capacity and greatly durable characteristics. Li et al. developed a hierarchical polymer electrolyte (HPE) based on a cross-linked gelatin-g-polyacrylamide (PAM) gel
filling the pores of an electrospun polyacrylonitrile (PAN) fiber membrane [60].
This HPE film demonstrating high Zn-ion conductivity, flexibility, and mechanical
strength was sandwiched between a flexible cathode containing tunnel-type α-MnO 2
nanorods grown in situ on acid-treated CNT papers and a flexible Zn anode film
electrodeposited on the surface of CNT paper to form the flexible ZIB, as illustrated
in Fig. 2a. This all solid-state ZIB clearly demonstrates reversible Zn-intercalation/
de-intercalation, (Figs. 2b and c). The cell with high area energy density (~
6.18 mW h cm
−2
) and power density (~ 148.2 mW cm
−2
) demonstrates specific
capacities of 306 mAh g
−1
with 97% capacity retention after 1000 cycles within the
1–1.8 V potential window. The report by Zeng et al. underlined the use of and a
modified poly(vinyl alcohol) (PVA) gel electrolyte (PVA/ZnCl 2 /MnSO 4 ) in combination with a MnO 2 @PEDOT (poly(3,4-ethylenedioxythiophene)) cathode and a
Zn nanosheet anode to form a quasi-solid-state ZIB that achieved an impressive
0.8
CNT paper
CNT paper
a
b
c
HPE
Zinc
MnO 2 paste
-4
0
4
8
1.0
E(V) vs.Zn
2+ /Zn
I (mA g
-1
)
1.2 1.4 1.6 1.8 2.0
1.0
1.2
1.4
1.6
1.8
0.8
0
5 0 100
Specific capacity (mAh g
-1 )
150 200 250 300
First
Voltage (V)
Second
Third
Fourth
1mV s -1
2mV s
-1
3mV s
-1
Fig. 2 (a) Schematic illustration of the structure of all solid-state ZIB. (b) CV curves of the all
solid-state ZIB under various scan rates. (c) Electrochemical profiles of the initial four cycles at
61.6 mA g
−1 current drain. (reprinted with permission from ref. [60])
Recent Developments of Zinc-Ion Batteries
ence a phase transformation into Zn-birnessite during electrochemical cycling in
ZIBs [47, 48].
Interestingly, all polymorphs of manganese oxide cathodes and spinel-type
ZnMn 2 O 4 cathodes were reported for ZIBs. Table 1 describes the electrochemical
performances of some prominent oxide materials in different electrolytes; it also
includes preparative techniques of the cathodes, concentration of the electrolytes,
additives and potential window employed for the respective ZIBs. For example, concentration dependent MnSO 4 used as an additive in zinc electrolyte can alter the
electrochemical reaction path in the Zn-MnO 2 system. In addition, the reversible
deposition/dissolution of MnO 2 on the surface of cathode through electrolytic manganese dioxide (EMD) is also accounted. This infers a complicated electrochemical
mechanism proven in Zn-MnO 2 battery system, thereby strongly questioning the role
of the additive to just the compensation of Mn
2+
dissolution from the cathode [59].
Considering that the present-day portable electronics industry is upgrading to
next-generation technologies including wearable batteries, the prospects for all
solid-state ZIBs based on aqueous electrolytes and manganese-based electrodes are
significant due to their cost-effective, nontoxic, extremely safe, high potential, high
capacity and greatly durable characteristics. Li et al. developed a hierarchical polymer electrolyte (HPE) based on a cross-linked gelatin-g-polyacrylamide (PAM) gel
filling the pores of an electrospun polyacrylonitrile (PAN) fiber membrane [60].
This HPE film demonstrating high Zn-ion conductivity, flexibility, and mechanical
strength was sandwiched between a flexible cathode containing tunnel-type α-MnO 2
nanorods grown in situ on acid-treated CNT papers and a flexible Zn anode film
electrodeposited on the surface of CNT paper to form the flexible ZIB, as illustrated
in Fig. 2a. This all solid-state ZIB clearly demonstrates reversible Zn-intercalation/
de-intercalation, (Figs. 2b and c). The cell with high area energy density (~
6.18 mW h cm
−2
) and power density (~ 148.2 mW cm
−2
) demonstrates specific
capacities of 306 mAh g
−1
with 97% capacity retention after 1000 cycles within the
1–1.8 V potential window. The report by Zeng et al. underlined the use of and a
modified poly(vinyl alcohol) (PVA) gel electrolyte (PVA/ZnCl 2 /MnSO 4 ) in combination with a MnO 2 @PEDOT (poly(3,4-ethylenedioxythiophene)) cathode and a
Zn nanosheet anode to form a quasi-solid-state ZIB that achieved an impressive
0.8
CNT paper
CNT paper
a
b
c
HPE
Zinc
MnO 2 paste
-4
0
4
8
1.0
E(V) vs.Zn
2+ /Zn
I (mA g
-1
)
1.2 1.4 1.6 1.8 2.0
1.0
1.2
1.4
1.6
1.8
0.8
0
5 0 100
Specific capacity (mAh g
-1 )
150 200 250 300
First
Voltage (V)
Second
Third
Fourth
1mV s -1
2mV s
-1
3mV s
-1
Fig. 2 (a) Schematic illustration of the structure of all solid-state ZIB. (b) CV curves of the all
solid-state ZIB under various scan rates. (c) Electrochemical profiles of the initial four cycles at
61.6 mA g
−1 current drain. (reprinted with permission from ref. [60])
Recent Developments of Zinc-Ion Batteries