Planar optical elements that can manipulate the multidimensional physical parameters of light efficiently and compactly are highly sought after in modern optics and nanophotonics. In recent years, ...the geometric phase, induced by the photonic spin–orbit interaction, has attracted extensive attention for planar optics due to its powerful beam shaping capability. The geometric phase can usually be generated via inhomogeneous anisotropic materials, among which liquid crystals (LCs) have been a focus. Their pronounced optical properties and controllable and stimuli‐responsive self‐assembly behavior introduce new possibilities for LCs beyond traditional panel displays. Recent advances in LC‐mediated geometric phase planar optics are briefly reviewed. First, several recently developed photopatterning techniques are presented, enabling the accurate fabrication of complicated LC microstructures. Subsequently, nematic LC‐based transmissive planar optical elements and chiral LC‐based broadband reflective elements are reviewed systematically. Versatile functionalities are revealed, from conventional beam steering and focusing, to advanced structuring. Combining the geometric phase with structured LC materials offers a satisfactory platform for planar optics with desired functionalities and drastically extends exceptional applications of ordered soft matter. Some prospects on this rapidly advancing field are also provided.
Recent advances in the liquid‐crystal (LC)‐mediated geometric phase are briefly summarized, from nematic‐LC‐mediated transmissive to chiral‐LC‐mediated broadband reflective planar optics. Numerous spin‐controlled functionalities are presented, including not only conventional beam steering and focusing, but also advanced light structuring. A comprehensive understanding of LC‐based geometric phase planar optics and their numerous applications is provided.
Li metal has been widely regarded as a promising anode for next‐generation batteries due to its high theoretical capacity and low electrochemical potential. The unstable solid‐electrolyte interphase ...(SEI) and uncontrollable dendrite growth, however, incur severe safety hazards and hamper the practical application of Li metal anodes. Herein, an advanced artificial SEI layer constructed by LiNBHn chains, which are crosslinked and self‐reinforced by their intermolecular LiN ionic bonds, is designed to comprehensively stabilize Li metal anodes on a molecular level. Benefiting from its polymer‐like structure, the LiNBHn layer is flexible and effectively tolerates the volume change of Li metal anodes. In addition, this layer with high polarity in its structure, helps to regulate the homogeneous distribution of the Li+ flux on Li electrodes via the further formation of LiN bonds. The designed LiNBHn layer is electrically nonconductive but highly ionically conductive, thus facilitating Li+ diffusion and confining Li deposition beneath the layer. Therefore, under the protection of the LiNBHn layer, the Li metal anodes exhibit stable cycling at a 3 mA cm−2 for more than 700 h, and the full cells with high lithium iron phosphate and sulfur cathodes mass loading also present excellent cycling stability.
An advanced LiNBHn layer is designed from a new bottom‐up perspective to molecularly serve as an artificial solid‐state interphase for Li metal anodes. This layer features both organic and inorganic characteristics with high ionic conductivity, high flexibility, comparable mechanical strength, and high polarity, thus comprehensively suppressing Li dendrite growth.
Multi‐heteroatoms co‐doped carbon coating can significantly enhance the electronic conductivity and mass transfer rate of the electrode materials due to the synergistic effect. In this study N, S ...co‐doped carbon coating is introduced on the surface of niobium oxides (GNO@NSC) by using a convenient thiourea evaporation method. Theory calculations and experimental results confirm the synergistic effect of N, S co‐doping in GNO@NSC composite. N, S co‐doping not only enlarges the layer distance of the carbon materials but also leads to more activation sites for lithium storage; meanwhile, the introduction of the co‐doping carbon layer on GNO significantly enhances the bonding interaction with GNO, leading to excellent structural stability and conductivity of the composite. As a result, the GNO@NSC composite possesses excellent structural reversibility, a large specific capacity, and high‐rate performance. GNO@NSC nanowires deliver a highly reversible capacity of 288 mAh g–1 and display excellent cycling stability, and its capacity retention is 78.9% after 6000 cycles at a high current density of 1 A g–1. This study reveals the functional mechanism of N, S co‐doped carbon coating and the origin of performance improvement of niobium oxides, which can be used for reference to design and develop relevant materials.
A nitrogen and sulfur co‐doped carbon coating can arouse synergistic effects to boost the electrochemical properties of a composite. Due to the strong bonding interaction, activation sites for lithium storage, large interlayer spacing, and stable structure in the nitrogen and sulfur co‐doped carbon layer, GNO@NSC displays superior rate performance, long cycling performance, and larger lithium‐ion diffusion coefficient.
The quality of the solid electrolyte interphase (SEI) layer is the decisive factor for the electrochemical performance of Li‐metal‐based batteries. Due to the absence of effective bonding, a natural ...SEI layer may exfoliate from the Li anode during interfacial fluctuations. Here, a silane coupling agent is introduced to serve as an adhesion promoter to bridge these two dissimilar materials via both chemical bonding and physical intertwining effects. Its inorganic reactive groups can combine with the Li substrate by forming LiOSi bonds, while organic functional groups can take part in the formation of the SEI layer and thereby bond with SEI components. Li metal electrodes with silane coupling agent modification exhibit excellent electrochemical performance, even under extreme testing conditions. This modification layer with dense structure could also protect the Li metal from corrosion by air, evidenced by the comparable electrochemical activity of the modified Li metal electrodes even after being exposed in air for 2 h. This design provides a promising pathway for the development of Li metal electrodes that will be stable both in electrolyte and in air.
A dense modification layer of a silane coupling agent enables Li metal to be stable in air and during cycling. This layer firmly adheres to the Li metal surface by forming LiOSi bonds, and it connects with the solid electrolyte interphase layer by chemical bonds and physical intertwining effects.
A 3D porous Cu current collector is fabricated through chemical dealloying from a commerial Cu–Zn alloy tape. The interlinked porous framework naturally integrated can accommodate Li deposition, ...suppressing dendrite growth and alleviating the huge volume change during cycling. The Li metal anode combined with such a porous Cu collector demonstrates excellent performance and commerial potentials in Li‐based secondary batteries.
All‐solid‐state lithium metal battery is the most promising next‐generation energy storage device. However, the low ionic conductivity of solid electrolytes and high interfacial impedance with ...electrode are the main factors to limit the development of all‐solid‐state batteries. In this work, a low resistance–integrated all‐solid‐state battery is designed with excellent electrochemical performance that applies the polyethylene oxide (PEO) with lithium bis(trifluoromethylsulphonyl)imide as both binder of cathode and matrix of composite electrolyte embedded with Li7La3Zr2O12 (LLZO) nanowires (PLLN). The PEO in cathode and PLLN are fused at high temperature to form an integrated all‐solid‐state battery structure, which effectively strengthens the interface compatibility and stability between cathode and PLLN to guarantee high efficient ion transportation during long cycling. The LLZO nanowires uniformly distributed in PLLN can increase the ionic conductivity and mechanical strength of composite electrolyte efficiently, which induces the uniform deposition of lithium metal, thereby suppressing the lithium dendrite growth. The Li symmetric cells using PLLN can stably cycle for 1000 h without short circuit at 60 °C. The integrated LiFePO4/PLLN/Li batteries show excellent cycling stability at both 60 and 45 °C. The study proposed a novel and robust battery structure with outstanding electrochemical properties.
A low resistance–integrated all‐solid‐state Li metal battery with excellent electrochemical performance is designed. The structure not only guarantees high ionic conductivity and good mechanical properties to suppress lithium dendrite growth by using polyethylene oxide (PEO)/lithium bis(trifluoromethylsulphonyl)imide embedded with Li7La3Zr2O12 nanowire composite electrolyte, but also decreases the interfacial impedance by applying PEO in both electrolyte and cathode that can fuse during operation.
Lithium (Li) metal is promising for high energy density batteries due to its low electrochemical potential (−3.04 V) and high specific capacity (3860 mAh g−1). However, the safety issues impede the ...commercialization of Li anode batteries. In this work, research of hierarchical structure designs for Li anodes to suppress Li dendrite growth and alleviate volume expansion from the interior (by the 3D current collector and host matrix) to the exterior (by the artificial solid electrolyte interphase (SEI), protective layer, separator, and solid state electrolyte) is concluded. The basic principles for achieving Li dendrite and volume expansion free Li anode are summarized. Following these principles, 3D porous current collector and host matrix are designed to suppress the Li dendrite growth from the interior. Second, artificial SEI, the protective layer, and separator as well as solid‐state electrolyte are constructed to regulate the distribution of current and control the Li nucleation and deposition homogeneously for suppressing the Li dendrite growth from exterior of Li anode. Ultimately, this work puts forward that it is significant to combine the Li dendrite suppression strategies from the interior to exterior by 3D hierarchical structure designs and Li metal modification to achieve excellent cycling and safety performance of Li metal batteries.
The strategy of suppressing Li dendrite growth and accommodating volume expansion is put forward from a new perspective of hierarchical structure designs of the Li anode from the interior (3D porous current collector and host matrix) to exterior (artificial solid electrolyte interphase (SEI), protective layer, separator, and solid‐state electrolyte). The Li dendrite growth mechanisms and suppression strategies are also concluded.
Graphite, commonly including artificial graphite and natural graphite (NG), possesses a relatively high theoretical capacity of 372 mA h g–1 and appropriate lithiation/de‐lithiation potential, and ...has been extensively used as the anode of lithium‐ion batteries (LIBs). With the requirements of reducing CO2 emission to achieve carbon neutral, the market share of NG anode will continue to grow due to its excellent processability and low production energy consumption. NG, which is abundant in China, can be divided into flake graphite (FG) and microcrystalline graphite (MG). In the past 30 years, many researchers have focused on developing modified NG and its derivatives with superior electrochemical performance, promoting their wide applications in LIBs. Here, a comprehensive overview of the origin, roles, and research progress of NG‐based materials in ongoing LIBs is provided, including their structure, properties, electrochemical performance, modification methods, derivatives, composites, and applications, especially the strategies to improve their high‐rate and low‐temperature charging performance. Prospects regarding the development orientation as well as future applications of NG‐based materials are also considered, which will provide significant guidance for the current and future research of high‐energy‐density LIBs.
A comprehensive overview of natural graphite‐based materials in ongoing lithium‐ion batteries is presented, covering fundamental mechanisms, detailed applications, and an outlook of natural graphite‐based materials, from not only the aspects of structure and properties, modifications, derivatives, and composites, but also perspectives in terms of natural graphite in hybrid lithium‐ion/lithium‐metal cells and all‐solid‐state lithium batteries.
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