Abstract:Na-birnessite has been synthesized using a simple precipitation reaction at room temperature and exhibits a high capacity of 39 mA h g−1 and long cycle life at 10C in Na-Bir/NaTi2(PO4)3 full cells.
“…Table 1 compares our results with some manganese oxides reported recently for aqueous electrolyte batteries. It can be seem that the reversible capacity of M2 synthesized in the present work is greatly higher than the reported Na 0.58 MnO 2 ·0.48H 2 O 29 , Na 4 Mn 9 O 18
30 , NaMnO 2
31 , K 0.27 MnO 2
38 , Na 0.95 MnO 2
39 and Na 0.44 MnO 2
40 .Figure 3( a ) Charge-discharge profiles of the as-prepared manganese oxides at 1.5 C, ( b ) Rate performance of M2 electrode, ( c ) Cycling performance of M0 and M2 electrodes at 1.5 C, and ( d ) Long cycling stability of M2 electrode at 50 C.
…”
Materials with a layered structure have attracted tremendous attention because of their unique properties. The ultrathin nanosheet structure can result in extremely rapid intercalation/de-intercalation of Na ions in the charge–discharge progress. Herein, we report a manganese oxide with pre-intercalated K and Na ions and having flower-like ultrathin layered structure, which was synthesized by a facile but efficient hydrothermal method under mild condition. The pre-intercalation of Na and K ions facilitates the access of electrolyte ions and shortens the ion diffusion pathways. The layered manganese oxide shows ultrahigh specific capacity when it is used as cathode material for sodium-ion batteries. It also exhibits excellent stability and reversibility. It was found that the amount of intercalated Na ions is approximately 71% of the total charge. The prominent electrochemical performance of the manganese oxide demonstrates the importance of design and synthesis of pre-intercalated ultrathin layered materials.
“…Table 1 compares our results with some manganese oxides reported recently for aqueous electrolyte batteries. It can be seem that the reversible capacity of M2 synthesized in the present work is greatly higher than the reported Na 0.58 MnO 2 ·0.48H 2 O 29 , Na 4 Mn 9 O 18
30 , NaMnO 2
31 , K 0.27 MnO 2
38 , Na 0.95 MnO 2
39 and Na 0.44 MnO 2
40 .Figure 3( a ) Charge-discharge profiles of the as-prepared manganese oxides at 1.5 C, ( b ) Rate performance of M2 electrode, ( c ) Cycling performance of M0 and M2 electrodes at 1.5 C, and ( d ) Long cycling stability of M2 electrode at 50 C.
…”
Materials with a layered structure have attracted tremendous attention because of their unique properties. The ultrathin nanosheet structure can result in extremely rapid intercalation/de-intercalation of Na ions in the charge–discharge progress. Herein, we report a manganese oxide with pre-intercalated K and Na ions and having flower-like ultrathin layered structure, which was synthesized by a facile but efficient hydrothermal method under mild condition. The pre-intercalation of Na and K ions facilitates the access of electrolyte ions and shortens the ion diffusion pathways. The layered manganese oxide shows ultrahigh specific capacity when it is used as cathode material for sodium-ion batteries. It also exhibits excellent stability and reversibility. It was found that the amount of intercalated Na ions is approximately 71% of the total charge. The prominent electrochemical performance of the manganese oxide demonstrates the importance of design and synthesis of pre-intercalated ultrathin layered materials.
“…On the contrary, when super P was added into the system as carbon source, a greatly increased atomic ratio of K/Mn was obtained (K/Mn ≈ 0.93; Figure S2d, Supporting Information) after the hydrothermal reaction of potassiation, demonstrating the efficient reduction of Mn 4+ by the carbonaceous materials. The crystal water contents were estimated to be 10.35, 4.31, 3.46, and 3.09 wt% in S0, S1, S2, and S3, respectively, by using thermogravimetric analysis (TGA; Figure S3, Supporting Information) . According to the inductively coupled plasma (ICP) measurements, the overall K/Mn atomic ratios for S0–S3 samples were calculated to be 0.18, 0.55, 0.75, and 0.68, respectively.…”
Potassium‐ion batteries (PIBs) are one of the emerging energy‐storage technologies due to the low cost of potassium and theoretically high energy density. However, the development of PIBs is hindered by the poor K+ transport kinetics and the structural instability of the cathode materials during K+ intercalation/deintercalation. In this work, birnessite nanosheet arrays with high K content (K0.77MnO2⋅0.23H2O) are prepared by “hydrothermal potassiation” as a potential cathode for PIBs, demonstrating ultrahigh reversible specific capacity of about 134 mAh g−1 at a current density of 100 mA g−1, as well as great rate capability (77 mAh g−1 at 1000 mA g−1) and superior cycling stability (80.5% capacity retention after 1000 cycles at 1000 mA g−1). With the introduction of adequate K+ ions in the interlayer, the K‐birnessite exhibits highly stabilized layered structure with highly reversible structure variation upon K+ intercalation/deintercalation. The practical feasibility of the K‐birnessite cathode in PIBs is further demonstrated by constructing full cells with a hard–soft composite carbon anode. This study highlights effective K+‐intercalation for birnessite to achieve superior K‐storage performance for PIBs, making it a general strategy for developing high‐performance cathodes in rechargeable batteries beyond lithium‐ion batteries.
“…In addition, these results suggest that a carbon coating process could be used to improve the energy capacity of such class of compounds which could allow this material to supply enough energy density to face some sodium metal oxides that might operate with capacities as high as 80 mA h g -1 under more elevated current densities. 43 Moreover, this approach can be particularly adequate for materials with small particle size, as observed for the 5 min processed Mn-based compound.…”
Although largely used in mobiles and electric vehicles applications, insertion batteries based on Li-ion technology are high-cost devices. These applications require high-performance energy storage systems with high-energy and high-power densities, which are better attained by Li-ion technology. However, stationary applications such as power plants and uninterruptible power supplies (UPS) mainly require low-cost energy storage devices. In this scenario Na-ion insertion batteries feature as a cheaper option for such applications. Among the several compounds for use as cathode in Na-batteries, a largely studied class of compounds are the sodium-carbonate-phosphates, Na 3 MCO 3 PO 4 (M = Mn, Fe, Co or Ni), with structure analogue to the mineral sidorenkite. In this work, it was developed a new microwave-assisted hydrothermal method as an ultra-fast way to prepare sodium-carbonate-phosphate compounds. This methodology results in high-quality materials with general formula Na 3 MCO 3 PO 4 (M = Mn, Fe, Co or Ni) upon only 5 min processing time. Characterization techniques indicate highly ordered materials with sidorenkite-like phase and different morphologies or crystal habits, including plates, rods, and a 'starfruit' shape. As a proof-of-application the Mn-based material was evaluated from electrochemical tests for Na + insertion reactions. The obtained results evidence initial discharge capacity of 107 mA h g-1 with good reversible capacity (65 mA h g-1) after several charge/discharge cycles.
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