The key bottlenecks hindering the practical implementations of lithium‐metal anodes in high‐energy‐density rechargeable batteries are the uncontrolled dendrite growth and infinite volume changes ...during charging and discharging, which lead to short lifespan and catastrophic safety hazards. In principle, these problems can be mitigated or even solved by loading lithium into a high‐surface‐area, conductive, and lithiophilic porous scaffold. However, a suitable material that can synchronously host a large loading amount of lithium and endure a large current density has not been achieved. Here, a lithiophilic 3D nanoporous nitrogen‐doped graphene as the sought‐after scaffold material for lithium anodes is reported. The high surface area, large porosity, and high conductivity of the nanoporous graphene concede not only dendrite‐free stripping/plating but also abundant open space accommodating volume fluctuations of lithium. This ingenious scaffold endows the lithium composite anode with a long‐term cycling stability and ultrahigh rate capability, significantly improving the charge storage performance of high‐energy‐density rechargeable lithium batteries.
A lithium composite anode is developed by rational combination of 3D nanoporous N‐doped graphene and Li melt. The issues of uncontrolled dendrite growth and infinite volume changes of Li‐metal anodes are simultaneously addressed by the integrated nanoporous Li anode, realizing high cycling stability and ultrafast rate performance at high area capacities.
State-of-the-art carbonaceous anodes are approaching their achievable performance limit in Li-ion batteries (LIBs). Silicon has been recognized as one of the most promising anodes for next-generation ...LIBs because of its advantageous specific capacity and secure working potential. However, the practical implementation of silicon anodes needs to overcome the challenges of substantial volume changes, intrinsic low conductivity, and unstable solid electrolyte interphase (SEI) films. Here, we report an inventive design of a sandwich N-doped graphene@Si@hybrid silicate anode with bicontinuous porous nanoarchitecture, which is expected to simultaneously conquer all these critical issues. In the ingeniously designed hybrid Si anode, the nanoporous N-doped graphene acts as a flexible and conductive support and the amorphous hybrid silicate coating enhances the robustness and suppleness of the electrode and facilitates the formation of stable SEI films. This binder-free and stackable hybrid electrode achieves excellent rate capability and cycling performance (817 mAh/g at 5 C for 10 000 cycles). Paired with LiFePO4 cathodes, more than 100 stable cycles can be readily realized in full batteries.
The real capacity of graphene and the lithium-storage process in graphite are two currently perplexing problems in the field of lithium ion batteries. Here we demonstrate a three-dimensional bilayer ...graphene foam with few defects and a predominant Bernal stacking configuration, and systematically investigate its lithium-storage capacity, process, kinetics, and resistances. We clarify that lithium atoms can be stored only in the graphene interlayer and propose the first ever planar lithium-intercalation model for graphenic carbons. Corroborated by theoretical calculations, various physiochemical characterizations of the staged lithium bilayer graphene products further reveal the regular lithium-intercalation phenomena and thus fully illustrate this elementary lithium storage pattern of two-dimension. These findings not only make the commercial graphite the first electrode with clear lithium-storage process, but also guide the development of graphene materials in lithium ion batteries.
Nitrogen‐doped graphene exhibits high electrocatalytic activity toward the oxygen reduction reaction (ORR), which is essential for many renewable energy technologies. To maximize the catalytic ...efficiency, it is desirable to have both a high concentration of robust nitrogen dopants and a large accessible surface of the graphene electrodes for rapid access of oxygen to the active sites. Here, 3D bicontinuous nitrogen‐doped mesoporous graphene synthesized by a low‐temperature carbide‐mediated graphene‐growth method is reported. The mesoporous graphene has a mesoscale pore size of ≈25 nm and large specific surface area of 1015 m2 g−1, which can effectively host and stabilize a high concentration of nitrogen dopants. Accordingly, it shows an excellent electrocatalytic activity toward the ORR with an efficient four‐electron‐dominated pathway and high durability in alkaline media. The synthesis route developed herein provides a new economic approach to synthesize bicontinuous porous graphene materials with tunable characteristic length, porosity, and chemical doping as high efficiency electrocatalysts for a wide range of electrochemical reactions.
3D bicontinuous nitrogen‐doped mesoporous graphene is synthesized by an economic low‐temperature carbide‐mediated method. The small pore size of ≈25 nm and large specific surface area of over 1000 m2 g−1 can effectively host and stabilize a high concentration of nitrogen dopants for excellent electrocatalytic activity toward the oxygen reduction reaction.
While the compressive strength-density scaling relationship of ultralight cellular graphene materials has been extensively investigated, high tensile strength and ductility have not been realized in ...the theoretically strongest carbon materials because of high flaw sensitivity under tension and weak van der Waals interplanar bonding between graphene sheets. In this study, we report that large-scale ultralight nanoporous graphene with three-dimensional bicontinuous nanoarchitecture shows orders of magnitude higher strength and elastic modulus than all reported ultralight carbon materials under both compression and tension. The high-strength nanoporous graphene also exhibits excellent tensile ductility and work hardening, which are comparable to well-designed metamaterials but until now had not been realized in ultralight cellular materials. The excellent mechanical properties of the nanoporous graphene benefit from seamless graphene sheets in the bicontinuous nanoporosity that effectively preserves the intrinsic strength of atomically thick graphene in the three-dimensional cellular nanoarchitecture.
Interface segregation is a powerful approach to tailor properties of bulk materials by interface engineering. Nevertheless, little is known about the chemical inhomogeneity at interfaces of ...polymorphic two-dimensional transition metal dichalcogenides (TMDs) and its influence on the properties of the 2D materials. Here we report one-dimensional monatomic segregation at coherent semiconductor-metal 1H/1T interfaces of Mo-doped WS2 monolayers. The monatomic interface segregation takes place at an intact transition metal plane and is associated with the topological defects caused by reflection symmetry breaking at the 1T/1H interfaces and the weak difference in bonding strength between Mo–S and W–S. This finding enriches our understanding of the interaction between topological defects and impurities in 2D crystals and enlightens a potential approach to manipulate the properties of 2D TMDs by local chemical modification and interface engineering for applications in 2D TMD electronic devices.
Dealloyed nanoporous metals are emerging as a new class of structural and functional materials for a wide range of applications. Nevertheless, the dealloying process usually leads to significant ...volume shrinkage, large internal stresses, surface oxidation, stress-corrosion cracking and thereby extensive fabrication flaws. This is particularly serious for nanoporous non-noble metals because of their high affinity with oxygen and resulting serious oxidation. Therefore, dealloyed nanoporous metals usually have poor mechanical performances, particularly, under tension which is highly sensitive to flaws. Consequently, high tensile strength has not been achieved from technically-important and economic nanoporous transition metals, such as Ni and Cu. In this study we report flaw-free nanoporous Ni fabricated by utilizing an ultrafine grained precursor alloy, high-temperature dealloying and post-dealloying annealing. The resulting nanoporous Ni shows an excellent tensile strength, which is one order of magnitude higher than all reported tensile strengths of dealloyed nanoporous metals. The strong and ductile nanoporous Ni developed in this study can be scaled up for large-scale structural and functional applications where tensile properties are required.
Display omitted
Nanoporous metals similar to paper in form are developed using Japanese washi paper as a template to create hierarchical porous electrodes. This method is used to create a trimodal nanoporous Au ...electrode, as a well as a hierarchical NiMn electrode that achieves high electrochemical capacitance and a rapid rate of oxygen evolution.
Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are prospective materials for quantum devices owing to their inherent 2D confinements. They also provide a platform to realize even ...lower-dimensional in-plane electron confinement, for example, 0D quantum dots, for exotic physical properties. However, fabrication of such laterally confined monolayer (1L) nanostructure in 1L crystals remains challenging. Here we report the realization of 1L ReS2 quantum dots epitaxially inlaid in 1L MoS2 by a two-step chemical vapor deposition method combining with plasma treatment. The lateral lattice mismatch between ReS2 and MoS2 leads to size-dependent crystal structure evolution and in-plane straining of the 1L ReS2 quantum dots. Optical spectroscopies reveal the abnormal charge transfer between the 1L ReS2 quantum dots and the MoS2 matrix, resulting from electron trapping in the 1L ReS2 quantum dots. This study may shed light on the development of in-plane quantum-confined devices in 2D materials for potential applications in quantum information.
Conductive polymers, particularly polypyrrole (PPy), are emerging as promising electrode materials for flexible supercapacitors because of their high pseudocapacitance, low density, high mechanical ...flexibility and low material costs. However, the practical implementations of PPy based supercapacitors have been prevented by the poor charge/discharge rate capability and low cycle stability. In this study we report a novel three dimensional interconnected nanotubular graphene–PPy (nt-GPPy) hybrid by incorporating PPy into highly conductive and stable nanoporous graphene. The bicontinuous nanotubular hybrid material with a large specific surface area and high conductivity demonstrates significant enhancement in supercapacitance performance of PPy in terms of high specific capacitance, excellent cycling stability and high rate capability.
Display omitted
•3D bicontinuous nanoporous graphene–polypyrrole composites were successfully developed.•Bicontinuous nanoporous graphene network significantly enhances the psudocapacitance of polypyrrole.•The hybrid composites demonstrate high stability and large specific capacitance.•The flexible supercapacitor delivers ultra-high power density and energy density.
PDF
