Manganese dioxide (MnO 2 ) with different crystal structures has been widely investigated as the cathode material for Zn-ion batteries, among which spinel λ -MnO 2 is yet rarely reported because Zn-ion intercalation in spinel lattice is speculated to be limited by the narrow three-dimensional tunnels. In this work, we demonstrate that Zn-ion insertion in spinel lattice can be enhanced by reducing particle size and elucidate an intriguing electrochemical reaction mechanism dependent on particle size. Specifically, λ -MnO 2 nanoparticles (NPs, ~80 nm) deliver a high capacity of 250 mAh/g at 20 mA/g due to large surface area and solid-solution type phase transition pathway. Meanwhile, severe water-induced Mn dissolution leads to the poor cycling stability of NPs. In contrast, micron-sized λ -MnO 2 particles (MPs, ~0.9 μ m) unexpectedly undergo an activation process with the capacity continuously increasing over the first 50 cycles, which can be attributed to the formation of amorphous MnO x nanosheets in the open interstitial space of the MP electrode. By adding MnSO 4 to the electrolyte, Mn dissolution can be suppressed, leading to significant improvement in the cycling performance of NPs, with a capacity of 115 mAh/g retained at 1 A/g for over 500 cycles. This work pinpoints the distinctive impacts of the particle size on the reaction mechanism and cathode performance in aqueous Zn-ion batteries.
more »
« less
The critical effect of water content in the electrolyte on the reversible electrochemical performance of Zn–VPO 4 F cells
The electrochemistry of the Zn–VPO 4 F system has been studied for the first time in both wet non-aqueous and aqueous zinc-ion electrolytes. It is shown that H + ions present in the electrolyte insert into the cathode host in preference to sluggish Zn 2+ ion insertion. Furthermore, it is demonstrated that while H 2 O as a source of H + is essential for proper cell operation, an aqueous electrolyte is detrimental to cathode stability due to extensive dissolution.
more »
« less
- Award ID(s):
- 1709081
- PAR ID:
- 10200292
- Date Published:
- Journal Name:
- Journal of Materials Chemistry A
- Volume:
- 8
- Issue:
- 17
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 8262 to 8267
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract It remains a challenge to design aqueous electrolytes to secure the complete reversibility of zinc metal anodes. The concentrated water‐in‐salt electrolytes, e.g., 30 m ZnCl2, are promising candidates to address the challenges of the Zn metal anode. However, the pure 30 m ZnCl2electrolyte fails to deliver a smooth surface morphology and a practically relevant Coulombic efficiency. Herein, it is reported that a small concentration of vanillin, 5 mg mLwater−1, added to 30 m ZnCl2transforms the reversibility of Zn metal anode by eliminating dendrites, lowering the Hammett acidity, and forming an effective solid electrolyte interphase. The presence of vanillin in the electrolyte enables the Zn metal anode to exhibit a high Coulombic efficiency of 99.34% at a low current density of 0.2 mA cm−2, at which the impacts of the hydrogen evolution reaction are allowed to play out. Using this new electrolyte, a full cell Zn metal battery with an anode/cathode capacity (N/P) ratio of 2:1 demonstrates no capacity fading over 800 cycles.more » « less
-
Aqueous zinc ion batteries (ZIBs) are emerging as a highly promising alternative technology for grid-scale applications where high safety, environmental-friendliness, and high specific capacities are needed. It remains a significant challenge, however, to develop a cathode with a high rate capability and long-term cycling stability. Here, we demonstrate diffusion-controlled behavior in the intercalation of zinc ions into highly porous, Mn 4+ -rich, and low-band-gap Ni x Mn 3−x O 4 nano-particles with a carbon matrix formed in situ (with the composite denoted as Ni x Mn 3−x O 4 @C, x = 1), which exhibits superior rate capability (139.7 and 98.5 mA h g −1 at 50 and 1200 mA g −1 , respectively) and outstanding cycling stability (128.8 mA h g −1 remaining at 400 mA g −1 after 850 cycles). Based on the obtained experimental results and density functional theory (DFT) calculations, cation-site Ni substitution combined with a sufficient doping concentration can decrease the band gap and effectively improve the electronic conductivity in the crystal. Furthermore, the amorphous carbon shell and highly porous Mn 4+ -rich structure lead to fast electron transport and short Zn 2+ diffusion paths in a mild aqueous electrolyte. This study provides an example of a technique to optimize cathode materials for high-performance rechargeable ZIBs and design advanced intercalation-type materials for other energy storage devices.more » « less
-
Abstract Rechargeable aqueous batteries with Zn2+as a working‐ion are promising candidates for grid‐scale energy storage because of their intrinsic safety, low‐cost, and high energy‐intensity. However, suitable cathode materials with excellent Zn2+‐storage cyclability must be found in order for Zinc‐ion batteries (ZIBs) to find practical applications. Herein, NaCa0.6V6O16·3H2O (NaCaVO) barnesite nanobelts are reported as an ultra‐stable ZIB cathode material. The original capacity reaches 347 mAh g−1at 0.1 A g−1, and the capacity retention rate is 94% after 2000 cycles at 2 A g−1and 83% after 10 000 cycles at 5 A g−1, respectively. Through a combined theoretical and experimental approach, it is discovered that the unique V3O8layered structure in NaCaVO is energetically favorable for Zn2+diffusion and the structural water situated between V3O8layers promotes a fast charge‐transfer and bulk migration of Zn2+by enlarging gallery spacing and providing more Zn‐ion storage sites. It is also found that Na+and Ca2+alternately suited in V3O8layers are the essential stabilizers for the layered structure, which play a crucial role in retaining long‐term cycling stability.more » « less
-
Abstract Ni‐rich LiNi0.8Co0.1Mn0.1O2(NCM811) has been considered as a promising cathode material for high energy density lithium‐ion batteries. However, it experiences undesirable interfacial side‐reactions with the electrolyte, which lead to a rapid capacity decay. In this work, a homogeneous precipitation method is proposed for forming a uniform silicon dioxide (SiO2) coating on the NCM811 surface. The strong Si−O network provided a stable protective layer between the NCM811 active material and electrolyte to improve the electrochemical stability. As a result, the NCM811@SiO2cathode showed superior cycling stability (84.9 % after 100 cycles at 0.2 C) and rate capability (142.7 mA h g−1at 5 C) compared to the pristine NCM811 cathode (56.6 % after 100 cycles, 127.9 mA h g−1at 5 C). Moreover, the SiO2coating effectively suppressed voltage decay and pulverization of the NCM811 particles during long term cycling. This uniform coating technique offers a viable approach for stabilizing Ni‐rich cathode materials for high‐energy density lithium‐ion batteries.more » « less
An official website of the United States government

