Engineering heterogeneous composite electrodes consisting of multiple active components for meeting various electrochemical and structural demands have proven indispensable for significantly boosting ...the performance of lithium‐ion batteries (LIBs). Here, a novel design of ZnS/Sn heterostructures with rich phase boundaries concurrently encapsulated into hierarchical interconnected porous nitrogen‐doped carbon frameworks (ZnS/Sn@NPC) working as superior anode for LIBs, is showcased. These ZnS/Sn@NPC heterostructures with abundant heterointerfaces, a unique interconnected porous architecture, as well as a highly conductive N‐doped C matrix can provide plentiful Li+‐storage active sites, facilitate charge transfer, and reinforce the structural stability. Accordingly, the as‐fabricated ZnS/Sn@NPC anode for LIBs has achieved a high reversible capacity (769 mAh g−1, 150 cycles at 0.1 A g−1), high‐rate capability and long cycling stability (600 cycles, 645.3 mAh g−1 at 1 A g−1, 92.3% capacity retention). By integrating in situ/ex situ microscopic and spectroscopic characterizations with theoretical simulations, a multiscale and in‐depth fundamental understanding of underlying reaction mechanisms and origins of enhanced performance of ZnS/Sn@NPC is explicitly elucidated. Furthermore, a full cell assembled with prelithiated ZnS/Sn@NPC anode and LiFePO4 cathode displays superior rate and cycling performance. This work highlights the significance of chemical heterointerface engineering in rationally designing high‐performance electrodes for LIBs.
A viable anode material composing of new‐type ZnS/Sn heterostructures with rich phase boundaries concurrently encapsulated into hierarchical interconnected porous nitrogen‐doped carbon frameworks (ZnS/Sn@NPC) is developed for high‐performance lithium ion batteries. Its Li+‐storage mechanism and origins of the superior performance are explicitly elucidated by combining in situ TEM/XRD/Raman studies, a suite of ex situ microscopic and spectroscopic characterizations with theoretical simulations.
Antimony trisulfide‐based materials have drawn growing attention as promising anode candidates for potassium‐ion batteries (PIBs) because of their high capacity and good working potential. Despite ...the extensive investigations on their electrochemical properties, the fundamental reaction mechanisms of Sb2S3 anodes, especially the reaction kinetics, structural changes, and phase evolutions, remain controversial or even largely unknown. Here, using in situ transmission electron microscopy, the entire potassiation–depotassiation cycles of carbon‐coated Sb2S3 single‐crystal nanowires are tracked in real time at the atomic scale. The potassiation of Sb2S3 involves multistep reactions including intercalation, conversion, and two‐step alloying, and the final products are identified as cubic K2S and hexagonal K3Sb. These findings are confirmed by density functional theory calculations. Interestingly, a rocket‐launching‐like nanoparticle growth behavior is observed during alloying reactions, which is driven by the K+ concentration gradient and release of stress. More impressively, the potassiated products (i.e., K3Sb and K2S) can transform into the original Sb2S3 phase during depotassiation, indicating a reversible phase transformation process, as distinct from other metal chalcogenide based electrodes. This work reveals the detailed potassiation/depotassiation mechanisms of Sb2S3‐based anodes and can facilitate the analysis of the mechanisms of other metal chalcogenide anodes in PIBs.
The atomic‐scale potassiation/depotassiation mechanisms of Sb2S3@carbon nanowires are investigated using an in situ transmission electron microscopy and density functional theory calculations. The potassiation involves multistep reactions including intercalation, conversion, and two‐step alloying featured by the growth of K‐Sb alloying nanoparticles that resembles the launching of a rocket. Impressively, the phase transformations are reversible during depotassiation, distinct from other metal chalcogenide‐based electrodes.
Metallic bismuth has drawn attention as a promising alloying anode for advanced potassium ion batteries (PIBs). However, serious volume expansion/electrode pulverization and sluggish kinetics always ...lead to its inferior cycling and rate properties for practical applications. Therefore, advanced Bi‐based anodes via structural/compositional optimization and sur‐/interface design are needed. Herein, we develop a bottom‐up avenue to fabricate nanoscale Bi encapsulated in a 3D N‐doped carbon nanocages (Bi@N‐CNCs) framework with a void space by using a novel Bi‐based metal‐organic framework as the precursor. With elaborate regulation in annealing temperatures, the optimized Bi@N‐CNCs electrode exhibits large reversible capacities and long‐duration cyclic stability at high rates when evaluated as competitive anodes for PIBs. Insights into the intrinsic K+‐storage processes of the Bi@N‐CNCs anode are put forward from comprehensive in situ characterizations.
A hierarchical nano Bi@N‐doped carbon nanocage framework with an interior void space was smartly fabricated as competitive anode for K‐ion batteries. Its intrinsic potassium storage behaviors are unveiled via comprehensive in situ characterizations.
The properties of high theoretical capacity, low cost, and large potential of metallic sodium (Na) has strongly promoted the development of rechargeable sodium‐based batteries. However, the issues of ...infinite volume variation, unstable solid electrolyte interphase (SEI), and dendritic sodium causes a rapid decline in performance and notorious safety hazards. Herein, a highly reversible encapsulation‐based sodium storage by designing a functional hollow carbon nanotube with Zn single atom sites embedded in the carbon shell (ZnSA‐HCNT) is achieved. The appropriate tube space can encapsulate bulk sodium inside; the inner enriched ZnSA sites provide abundant sodiophilic sites, which can evidently reduce the nucleation barrier of Na deposition. Moreover, the carbon shell derived from ZIF‐8 provides geometric constraints and excellent ion/electron transport channels for the rapid transfer of Na+ due to its pore‐rich shell, which can be revealed by in situ transmission electron microscopy (TEM). As expected, Na@ZnSA‐HCNT anodes present steady long‐term performance in symmetrical battery (>900 h at 10 mA cm−2). Moreover, superior electrochemical performance of Na@ZnSA‐HCNT||PB full cells can be delivered. This work develops a new strategy based on carbon nanotube encapsulation of metallic sodium, which improves the safety and cycling performance of sodium metal anode.
Designing a functional encapsulation‐based sodium storage void with abundant pore structure and enriched Zn single atom sites in the inner wall is presented here. Zn single atoms provide abundant selective sodiophilic nucleation sites. Due to the rich pore structure, ZIF‐derived carbon shells can provide geometric constraints and excellent ion/electron transport channels to maintain fast electron/ion contact, benefiting for encapsulating large amounts of metallic sodium.
Potassium‐ion batteries (PIBs) are promising alternatives to lithium‐ion batteries because of the advantage of abundant, low‐cost potassium resources. However, PIBs are facing a pivotal challenge to ...develop suitable electrode materials for efficient insertion/extraction of large‐radius potassium ions (K+). Here, a viable anode material composed of uniform, hollow porous bowl‐like hard carbon dual doped with nitrogen (N) and phosphorus (P) (denoted as N/P‐HPCB) is developed for high‐performance PIBs. With prominent merits in structure, the as‐fabricated N/P‐HPCB electrode manifests extraordinary potassium storage performance in terms of high reversible capacity (458.3 mAh g−1 after 100 cycles at 0.1 A g−1), superior rate performance (213.6 mAh g−1 at 4 A g−1), and long‐term cyclability (205.2 mAh g−1 after 1000 cycles at 2 A g−1). Density‐functional theory calculations reveal the merits of N/P dual doping in favor of facilitating the adsorption/diffusion of K+ and enhancing the electronic conductivity, guaranteeing improved capacity, and rate capability. Moreover, in situ transmission electron microscopy in conjunction with ex situ microscopy and Raman spectroscopy confirms the exceptional cycling stability originating from the excellent phase reversibility and robust structure integrity of N/P‐HPCB electrode during cycling. Overall, the findings shed light on the development of high‐performance, durable carbon anodes for advanced PIBs.
A viable anode material composed of nitrogen/phosphorus co‐doped hollow porous bowl‐like hard carbon is developed for potassium ion batteries. The resulting anode manifests prominent merits in structure, endowing it with extraordinary K+ storage capability. The K+ storage mechanisms are revealed through in‐depth studies by combining in situ TEM studies, ex situ microscopic, and Raman spectroscopy in conjunction with DFT calculations.
Abstract
Air-stability is one of the most important considerations for the practical application of electrode materials in energy-harvesting/storage devices, ranging from solar cells to rechargeable ...batteries. The promising P2-layered sodium transition metal oxides (P2-Na
x
TmO
2
) often suffer from structural/chemical transformations when contacted with moist air. However, these elaborate transitions and the evaluation rules towards air-stable P2-Na
x
TmO
2
have not yet been clearly elucidated. Herein, taking P2-Na
0.67
MnO
2
and P2-Na
0.67
Ni
0.33
Mn
0.67
O
2
as key examples, we unveil the comprehensive structural/chemical degradation mechanisms of P2-Na
x
TmO
2
in different ambient atmospheres by using various microscopic/spectroscopic characterizations and first-principle calculations. The extent of bulk structural/chemical transformation of P2-Na
x
TmO
2
is determined by the amount of extracted Na
+
, which is mainly compensated by Na
+
/H
+
exchange. By expanding our study to a series of Mn-based oxides, we reveal that the air-stability of P2-Na
x
TmO
2
is highly related to their oxidation features in the first charge process and further propose a practical evaluating rule associated with redox couples for air-stable Na
x
TmO
2
cathodes.
Abstract
Layered transition metal oxides are the most important cathode materials for Li/Na/K ion batteries. Suppressing undesirable phase transformations during charge-discharge processes is a ...critical and fundamental challenge towards the rational design of high-performance layered oxide cathodes. Here we report a shale-like Na
x
MnO
2
(S-NMO) electrode that is derived from a simple but effective water-mediated strategy. This strategy expands the Na
+
layer spacings of P2-type Na
0.67
MnO
2
and transforms the particles into accordion-like morphology. Therefore, the S-NMO electrode exhibits improved Na
+
mobility and near-zero-strain property during charge-discharge processes, which leads to outstanding rate capability (100 mAh g
−1
at the operation time of 6 min) and cycling stability (>3000 cycles). In addition, the water-mediated strategy is feasible to other layered sodium oxides and the obtained S-NMO electrode has an excellent tolerance to humidity. This work demonstrates that engineering the spacings of alkali-metal layer is an effective strategy to stabilize the structure of layered transition metal oxides.
Broad absorption, long-lived photogenerated carriers, high conductance, and high stability are all required for a light absorber toward its real application on solar cells. Inorganic–organic hybrid ...lead-halide materials have shown tremendous potential for applications in solar cells. This work offers a new design strategy to improve the absorption range, conductance, photoconductance, and stability of these materials. We synthesized a new photochromic lead-chloride semiconductor by incorporating a photoactive viologen zwitterion into a lead-chloride system in the coordinating mode. This semiconductor has a novel inorganic–organic hybrid structure, where 1-D semiconducting inorganic lead-chloride nanoribbons covalently bond to 1-D semiconducting organic π-aggregates. It shows high stability against light, heat, and moisture. After photoinduced electron transfer (PIET), it yields a long-lived charge-separated state with a broad absorption band covering the 200–900 nm region while increasing its conductance and photoconductance. This work is the first to modify the photoconductance of semiconductors by PIET. The observed increasing times of conductivity reached 3 orders of magnitude, which represents a record for photoswitchable semiconductors. The increasing photocurrent comes mainly from the semiconducting organic π-aggregates, which indicates a chance to improve the photocurrent by modifying the organic component. These findings contribute to the exploration of light absorbers for solar cells.
Extending photoresponse ranges of semiconductors to the entire ultraviolet-visible (UV)-shortwave near-infrared (SWIR) region (ca. 200-3000 nm) is highly desirable to reduce complexity and cost of ...photodetectors or to promote power conversion efficiency of solar cells. The observed up limit of photoresponse for organic-based semiconductors is about 1800 nm, far from covering the UV-SWIR region. Here we develop a cyanide-bridged layer-directed intercalation approach and obtain a series of two viologen-based 2D semiconductors with multispectral photoresponse. In these compounds, infinitely π-stacked redox-active N-methyl bipyridinium cations with near-planar structures are sandwiched by cyanide-bridged Mn
-Fe
or Zn
-Fe
layers. Radical-π interactions among the infinitely π-stacked N-methyl bipyridinium components favor the extension of absorption range. Both semiconductors show light/thermo-induced color change with the formation of stable radicals. They have intrinsic photocurrent response in the range of at least 355-2400 nm, which exceeds all reported values for known single-component organic-based semiconductors.
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