Layered transition metal oxides are appealing cathodes for sodium‐ion batteries due to their overall advantages in energy density and cost. But their stabilities are usually compromised by the complicated phase transition and the oxygen redox, particularly when operating at high voltages, leading to poor structural stability and substantial capacity loss. Here an integrated strategy combing the high‐entropy design with the superlattice‐stabilization to extend the cycle life and enhance the rate capability of layered cathodes is reported. It is shown that the as‐prepared high‐entropy Na2/3Li1/6Fe1/6Co1/6Ni1/6Mn1/3O2cathode enables a superlattice structure with Li/transition metal ordering and delivers excellent electrochemical performance that is not affected by the presence of phase transition and oxygen redox. It achieves a high reversible capacity (171.2 mAh g−1at 0.1 C), a high energy density (531 Wh kg−1), extended cycling stability (89.3% capacity retention at 1 C for 90 cycles and 63.7% capacity retention at 5 C after 300 cycles), and excellent fast‐charging capability (78 mAh g−1at 10 C). This strategy would inspire more rational designs that can be leveraged to improve the reliability of layered cathodes for secondary‐ion batteries.
Rechargeable aqueous Zn−MnO2batteries are promising for stationary energy storage because of their high energy density, safety, environmental benignity, and low cost. Conventional gravel MnO2cathodes have low electrical conductivity, slow ion (de‐)insertion, and poor cycle stability, resulting in poor recharging performance and severe capacity fading. To improve the rechargeability of MnO2, strategies have been devised such as depositing micrometer‐thick MnO2on carbon cloth and blending nanostructured MnO2with additives and binders. The low electrical conductivity of binders and sluggish ion (de‐)insertion in micrometer‐thick MnO2, however, still limit the fast‐charging performance. Herein, we have prepared porous carbon fiber (PCF) supported MnO2cathodes (PCF@MnO2), comprised of nanometer‐thick MnO2uniformly deposited on electrospun block copolymer‐derived PCF that have abundant uniform mesopores. The high electrical conductivity of PCF, fast electrochemical reactions in nanometer‐thick MnO2,and fast ion transport through porous nonwoven fibers contribute to a high rate capability at high loadings. PCF@MnO2, at a MnO2loading of 59.1 wt %, achieves a MnO2‐based specific capacity of 326 and 184 mAh g−1at a current density of 0.1 and 1.0 A g−1, respectively. Our approach of block copolymer‐based PCF as a support for zinc‐ion cathode inspires future designs of fast‐charging electrodes with other active materials.
more » « less- Award ID(s):
- 1752611
- NSF-PAR ID:
- 10365184
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Batteries & Supercaps
- Volume:
- 5
- Issue:
- 4
- ISSN:
- 2566-6223
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Aqueous dual‐ion batteries (DIBs) are promising for large‐scale energy storage due to low cost and inherent safety. However, DIBs are limited by low capacity and poor cycling of cathode materials and the challenge of electrolyte decomposition. In this study, a new cathode material of nitrogen‐doped microcrystalline graphene‐like carbon is investigated in a water‐in‐salt electrolyte of 30 m ZnCl2, where this carbon cathode stores anions reversibly via both electrical double layer adsorption and ion insertion. The (de)insertion of anions in carbon lattice delivers a high‐potential plateau at 1.85 V versus Zn2+/Zn, contributing nearly 1/3 of the capacity of 134 mAh g−1and half of the stored energy. This study shows that both the unique carbon structure and concentrated ZnCl2electrolyte play critical roles in allowing anion storage in carbon cathode for this aqueous DIB.
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Manganese dioxide (MnO 2 ) with a conversion mechanism is regarded as a promising anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity (∼1223 mA h g −1 ) and environmental benignity as well as low cost. However, it suffers from insufficient rate capability and poor cyclic stability. To circumvent this obstacle, semiconducting polypyrrole coated-δ-MnO 2 nanosheet arrays on nickel foam (denoted as MnO 2 @PPy/NF) are prepared via hydrothermal growth of MnO 2 followed by the electrodeposition of PPy on the anode in LIBs. The electrode with ∼50 nm thick PPy coating exhibits an outstanding overall electrochemical performance. Specifically, a high rate capability is obtained with ∼430 mA h g −1 of discharge capacity at a high current density of 2.67 A g −1 and more than 95% capacity is retained after over 120 cycles at a current rate of 0.86 A g −1 . These high electrochemical performances are attributed to the special structure which shortens the ion diffusion pathway, accelerates charge transfer, and alleviates volume change in the charging/discharging process, suggesting a promising route for designing a conversion-type anode material for LIBs.more » « less
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Thick sintered porous tellurium pellets are fabricated and evaluated as cathodes in lithium–tellurium batteries. These electrodes lack inactive binders and conductive additives and have very high areal capacity, which are important attributes for increasing cell energy density. More commonly tellurium in lithium–tellurium batteries is processed via melt impregnation into a conductive host. In contrast, herein, porous sintered electrodes comprising only tellurium material dramatically increase the areal active material loading to 150 mg cm−2compared to the typically reported <5 mg cm−2. A processing route is used on the tellurium powder to reduce the particle size and increase the electroactive area by a factor of 13. With the increased surface area, gravimetric capacity increased for the same current density and retention of capacity at increasing rates has even greater improvement. Thick all active material–sintered tellurium electrodes provide a route toward high volumetric energy density batteries, where the relatively high electronic conductivity of tellurium is expected to be beneficial due to the lack of conductive additives in the electrode system.
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Conventional lithium-ion batteries are unable to meet the increasing demands for high-energy storage systems, because of their limited theoretical capacity. 1 In recent years, intensive attention has been paid to enhancing battery energy storage capability to satisfy the increasing energy demand in modern society and reduce the average energy capacity cost. Among the candidates for next generation high energy storage systems, the lithium sulfur battery is especially attractive because of its high theoretical specific energy (around 2600 W h kg-1) and potential cost reduction. In addition, sulfur is a cost effective and environmentally friendly material due to its abundance and low-toxicity. 2 Despite all of these advantages, the practical application of lithium sulfur batteries to date has been hindered by a series of obstacles, including low active material loading, poor cycle life, and sluggish sulfur conversion kinetics. 3 Achieving high mass loading cathode in the traditional 2D planar thick electrode has been challenged. The high distorsion of the traditional planar thick electrodes for ion/electron transfer leads to the limited utilization of active materials and high resistance, which eventually results in restricted energy density and accelerated electrode failure. 4 Furthermore, of the electrolyte to pores in the cathode and utilization ratio of active materials. Catalysts such as MnO 2 and Co dopants were employed to accelerate the sulfur conversion reaction during the charge and discharge process. 5 However, catalysts based on transition metals suffer from poor electronic conductivity. Other catalysts such as transition metal dopants are also limited due to the increased process complexities. . In addition, the severe shuttle effects in Li-S batteries may lead to fast failures of the battery. Constructing a protection layer on the separator for limiting the transmission of soluble polysulfides is considered an effective way to eliminate the shuttle phenomenon. However, the soluble sulfides still can largely dissolve around the cathode side causing the sluggish reaction condition for sulfur conversion. 5 To mitigate the issues above, herein we demonstrate a novel sulfur electrode design strategy enabled by additive manufacturing and oxidative vapor deposition (oCVD). Specifically, the electrode is strategically designed into a hierarchal hollow structure via stereolithography technique to increase sulfur usage. The active material concentration loaded to the battery cathode is controlled precisely during 3D printing by adjusting the number of printed layers. Owing to its freedom in geometry and structure, the suggested design is expected to improve the Li ions and electron transport rate considerably, and hence, the battery power density. The printed cathode is sintered at 700 °C at N 2 atmosphere to achieve carbonization of the cathode during which intrinsic carbon defects (e.g., pentagon carbon) as catalytic defect sites are in-situ generated on the cathode. The intrinsic carbon defects equipped with adequate electronic conductivity. The sintered 3D cathode is then transferred to the oCVD chamber for depositing a thin PEDOT layer as a protection layer to restrict dissolutions of sulfur compounds in the cathode. Density functional theory calculation reveals the electronic state variance between the structures with and without defects, the structure with defects demonstrates the higher kinetic condition for sulfur conversion. To further identify the favorable reaction dynamic process, the in-situ XRD is used to characterize the transformation between soluble and insoluble polysulfides, which is the main barrier in the charge and discharge process of Li-S batteries. The results show the oCVD coated 3D printed sulfur cathode exhibits a much higher kinetic process for sulfur conversion, which benefits from the highly tailored hierarchal hollow structure and the defects engineering on the cathode. Further, the oCVD coated 3D printed sulfur cathode also demonstrates higher stability during long cycling enabled by the oCVD PEDOT protection layer, which is verified by an absorption energy calculation of polysulfides at PEDOT. Such modeling and analysis help to elucidate the fundamental mechanisms that govern cathode performance and degradation in Li-S batteries. The current study also provides design strategies for the sulfur cathode as well as selection approaches to novel battery systems. References: Bhargav, A., (2020). Lithium-Sulfur Batteries: Attaining the Critical Metrics. Joule 4 , 285-291. Chung, S.-H., (2018). Progress on the Critical Parameters for Lithium–Sulfur Batteries to be Practically Viable. Advanced Functional Materials 28 , 1801188. Peng, H.-J.,(2017). Review on High-Loading and High-Energy Lithium–Sulfur Batteries. Advanced Energy Materials 7 , 1700260. Chu, T., (2021). 3D printing‐enabled advanced electrode architecture design. Carbon Energy 3 , 424-439. Shi, Z., (2021). Defect Engineering for Expediting Li–S Chemistry: Strategies, Mechanisms, and Perspectives. Advanced Energy Materials 11 . Figure 1more » « less
