Tungsten‐Based Materials for Lithium‐Ion Batteries

Lithium‐ion batteries are widely used as reliable electrochemical energy storage devices due to their high energy density and excellent cycling performance. The search for anode materials with excellent electrochemical performances remains critical to the further development of lithium‐ion batteries. Tungsten‐based materials are receiving considerable attention as promising anode materials for lithium‐ion batteries owing to their high intrinsic density and rich framework diversity. This review describes the advances of exploratory research on tungsten‐based materials (tungsten oxide, tungsten sulfide, tungsten diselenide, and their composites) in lithium‐ion batteries, including synthesis methods, microstructures, and electrochemical performance. Some personal prospects for the further development of this field are also proposed.     

Applications of Tin Sulfide‐Based Materials in Lithium‐Ion Batteries and Sodium‐Ion Batteries

SnS_x (x = 1, 2) compounds are composed of earth‐abundant elements and are nontoxic and low‐cost materials that have received increasing attention as energy materials over the past decades, owing to their huge potential in batteries. Generally, SnS_x materials have excellent chemical stability and high theoretical capacity and reversibility due to their unique 2D‐layered structure and semiconductor properties. As a promising matrix material for storing different alkali metal ions through alloying/dealloying reactions, SnS_x compounds have broad electrochemical prospects in batteries. Herein, the structural properties of SnS_x materials and their advantages as electrode materials are discussed. Furthermore, detailed accounts of various synthesis methods and applications of SnS_x materials in lithium‐ion batteries, sodium‐ion batteries, and other new rechargeable batteries are emphasized. Ultimately, the challenges and opportunities for future research on SnS_x compounds are discussed based on the available academic knowledge, including recent scientific advances.     

Bio‐Derived Polymers for Sustainable Lithium‐Ion Batteries

Biologically derived organic molecules are a cost‐effective and environmentally benign alternative to the widely used metal‐based electrodes employed in current energy storage technologies. Here, the first bio‐derived pendant polymer cathode for lithium‐ion batteries is reported. The redox moiety is flavin and is derived from riboflavin (vitamin B₂). A semi‐synthetic methodology is used to prepare the pendant polymer, which is composed of a poly(norbornene) backbone and pendant flavin units. This semi‐synthetic approach reduces the number of chemical transformations required to form this new functional material. Lithium‐ion batteries incorporating this polymer have a 125 mAh g^?1 capacity and an ≈2.5 V operating potential. It is found that charge transport is greatly improved by forming hierarchical structures of the polymer with carbon black, and new insight into electrode degradation mechanisms is provided which should be applicable to polymer electrodes in general. This work provides a foundation for the use of bio‐derived pendant polymers in sustainable, high‐performance lithium‐ion batteries.     

Layer‐Based Heterostructured Cathodes for Lithium‐Ion and Sodium‐Ion Batteries

A critical bottleneck that hinders major performance improvement in lithium‐ion and sodium‐ion batteries is the inferior electrochemical activity of their cathode materials. While significant research progresses have been made, conventional single‐phase cathodes are still limited by intrinsic deficiencies such as low reversible capacity, enormous initial capacity loss, rapid capacity decay, and poor rate capability. In the past decade, layer‐based heterostructured cathodes acquired by combining multiple crystalline phases have emerged as candidates with a huge potential to realize performance breakthrough. Herein, recent studies on the structural properties, electrochemical behaviors, and synthesis route optimizations of these heterostructured cathodes are summarized for in‐depth discussions. Particular attention is paid to the latest mechanism discoveries and performance achievements. This review thus aims to promote a deeper understanding of the correlation between the crystal structure of cathodes and their electrochemical behavior, and offers guidance to design advance cathode materials from the aspect of crystal structure engineering.     

Nanostructured Silicon Anodes for High‐Performance Lithium‐Ion Batteries

Despite the high theoretical capacity of Si anodes, the electrochemical performance of Si anodes is hampered by severe volume changes during lithiation and delithiation, leading to poor cyclability and eventual electrode failure. Nanostructured silicon and its nanocomposite electrodes could overcome this problem holding back the deployment of Si anodes in lithium‐ion batteries (LIBs) by providing facile strain relaxation, short lithium diffusion distances, enhanced mass transport, and effective electrical contact. Here, the recent progress in nanostructured Si‐based anode materials such as nanoparticles, nanotubes, nanowires, porous Si, and their respective composite materials and fabrication processes in the application of LIBs have been reviewed. The ability of nanostructured Si materials in addressing the above mentioned challenges have been highlighted. Future research directions in the field of nanostructured Si anode materials for LIBs are summarized.     

Magnesium Anodes with Extended Cycling Stability for Lithium‐Ion Batteries

Magnesium as a promising alloy‐type anode material for lithium‐ion batteries features both high theoretical specific capacity (2150 mAh g^?1) and stack energy density (1032 Wh L^?1). However, the poor cycling performance of Mg‐based anodes severely limits their application, mainly because high‐impedance films can grow easily on the surface of Mg and cause diminished electrochemical activity. As a result, the capacities of reported Mg anodes fade quickly in less than 100 cycles. To improve the stability of Mg anodes, 3D Cu@Mg@C structures are prepared by depositing Mg/C composite on 3D Cu current collectors. The resulting 3D Cu@Mg@C anodes can deliver an initial capacity of 1392 mAh g^?1. With a second‐cycle capacity of 1255 mAh g^?1, 91% can be retained after 1000 cycles at 0.5 C. When cycled at 2 C, the initial capacity can be maintained for 4000 cycles. This remarkably improved cycling performance can be attributed to both the 3D structure and the embedded carbon layers of the 3D Cu@Mg@C electrodes that facilitate electrical contact and prevent the growth of high‐impedance films during cycling. With 3D Cu@Mg@C anodes and LiFePO₄ cathodes, full cells are assembled and charging by a rotating triboelectric nanogenerator that can harvest mechanical energy is demonstrated.     

Graphene‐Based Mesoporous SnO2 with Enhanced Electrochemical Performance for Lithium‐Ion Batteries

Graphene‐based metal oxides generally show outstanding electrochemical performance due to the superior properties of graphene. However, the aggregation of active metal oxide nanoparticles on the graphene surface may result in a capacity fading and poor cycle performance. Here, a mesostructured graphene‐based SnO₂ composite is prepared through in situ growth of SnO₂ particles on the graphene surface using cetyltrimethylammonium bromide as the structure‐directing agent. This novel mesoporous composite inherits the advantages of graphene nanosheets and mesoporous materials and exhibits higher reversible capacity, better cycle performance, and better rate capability compared to pure mesoporous SnO₂ and graphene‐based nonporous SnO₂. It is concluded that the synergetic effect between graphene and mesostructure benefits the improvement of the electrochemical properties of the hybrid composites. This facile method may offer an attractive alternative approach for preparation of the graphene‐based mesoporous composites as high‐ performance electrodes for lithium‐ion batteries.     

Quaternary Diamond‐Like Chalcogenidometalate Networks as Efficient Anode Material in Lithium‐Ion Batteries

An improvement of lithium‐ion batteries with regard to their reversible capacity, cycling stability, rate performance, and safety under repetitive charge and discharge still requires considerable research activity. However, graphite has remained the unexcelled material for the anode so far. Here, it is shown that two novel quaternary lithium‐chalcogenidometalate phases, Li₄MnGe₂S₇ ( 1 ) and Li₄MnSn₂Se₇ ( 2 ), represent very promising new anode materials for lithium‐ion cells in that they achieve specific lithium storage capacities higher than that of the commercially used graphite, and display an excellent stability during cycling. These properties are based on the structural peculiarities of the phases, which adopt Wurtzite‐related topologies and provide high structural flexibility of the metal sulfide or selenide bonds as advantageous pre‐requisitions for a large ion accessible volume.     

Co3O4 Nanomaterials in Lithium‐Ion Batteries and Gas Sensors

Co₃O₄ nanotubes, nanorods, and nanoparticles are used as the anode materials of lithium‐ion batteries. The results show that the Co₃O₄ nanotubes prepared by a porous‐alumina‐template method display high discharge capacity and superior cycling reversibility. Furthermore, Co₃O₄ nanotubes exhibit excellent sensitivity to hydrogen and alcohol, owing to their hollow, nanostructured character.     

Vanadium Doping Enhanced Electrochemical Performance of Molybdenum Oxide in Lithium‐Ion Batteries

Molybdenum trioxide (MoO₃) suffers from poor conductivity, a low rate capability, and unsatisfactory cycling stability in lithium‐ion batteries. The aliovalent ion doping may present an effective way to improve the electrochemical performances of MoO₃. Here, it is shown, by first‐principle calculations, that doping MoO₃ with V by 12.5% can modulate significantly electronic structure and provide a small diffusion barrier for enhancing the electrochemical performance of MoO₃. The ultralong Mo_0.88V_0.12O_2.94 nanostructures, which retain the h‐MoO₃ structure and present an exceptionally high conductivity and fast ionic diffusion due to the substitution of V, facilitating lithiation/delithiation behavior, and induce a fine nanosized structure with a reduced volume change are prepared. As a result, the stress and strain are alleviated during the Li‐ion intercalation/deintercalation processes, improving the cycling stability and rate capability. Such a large improvement in the electrochemical properties can be ascribed to the stabilizing effect of V, the small migration energy barrier, and short diffusion path, which arise from the introduction of V into MoO₃. The unique engineering strategy and facile synthesis route open up a new avenue in modifying and developing other species of electrode materials.     

N‐Doped Graphene‐SnO2 Sandwich Paper for High‐Performance Lithium‐Ion Batteries

A new facile route to fabricate N‐doped graphene‐SnO₂ sandwich papers is developed. The 7,7,8,8‐tetracyanoquinodimethane anion (TCNQ^?) plays a key role for the formation of such structures as it acts as both the nitrogen source and complexing agent. If used in lithium‐ion batteries (LIBs), the material exhibits a large capacity, high rate capability, and excellent cycling stability. The superior electrochemical performance of this novel material is the result from its unique features: excellent electronic conductivity related to the sandwich structure, short transportation length for both lithium ions and electrons, and elastomeric space to accommodate volume changes upon Li insertion/extraction.     

Unveiling Nickel Chemistry in Stabilizing High‐Voltage Cobalt‐Rich Cathodes for Lithium‐Ion Batteries

A practical solution is presented to increase the stability of 4.45 V LiCoO₂ via high‐temperature Ni doping, without adding any extra synthesis step or cost. How a putative uniform bulk doping with highly soluble elements can profoundly modify the surface chemistry and structural stability is identified from systematic chemical and microstructural analyses. This modification has an electronic origin, where surface‐oxygen‐loss induced Co reduction that favors the tetrahedral site and causes damaging spinel phase formation is replaced by Ni reduction that favors octahedral site and creates a better cation‐mixed structure. The findings of this study point to previously unspecified surface effects on the electrochemical performance of battery electrode materials hidden behind an extensively practiced bulk doping strategy. The new understanding of complex surface chemistry is expected to help develop higher‐energy‐density cathode materials for rechargeable batteries.     

Highly Stretchable Conductive Glue for High‐Performance Silicon Anodes in Advanced Lithium‐Ion Batteries

Binder plays a key role in maintaining the mechanical integrity of electrodes in lithium‐ion batteries. However, the existing binders typically exhibit poor stretchability or low conductivity at large strains, which are not suitable for high‐capacity silicon (Si)‐based anodes undergoing severe volume changes during cycling. Herein, a novel stretchable conductive glue (CG) polymer that possesses inherent high conductivity, excellent stretchablity, and ductility is designed for high‐performance Si anodes. The CG can be stretched up to 400% in volume without conductivity loss and mechanical fracture and thus can accommodate the large volume change of Si nanoparticles to maintain the electrode integrity and stabilize solid electrolyte interface growth during cycling while retaining the high conductivity, even with a high Si mass loading of 90%. The Si‐CG anode has a large reversible capacity of 1500 mA h g^?1 for over 700 cycles at 840 mA g^?1 with a large initial Coulombic efficiency of 80% and high rate capability of 737 mA h g^?1 at 8400 mA g^?1. Moreover, the Si‐CG anode demonstrates the highest achieved areal capacity of 5.13 mA h cm^?2 at a high mass loading of 2 mg cm^?2. The highly stretchable CG provides a new perspective for designing next‐generation high‐capacity and high‐power batteries.     

Rational Molecular Design of Benzoquinone‐Derived Cathode Materials for High‐Performance Lithium‐Ion Batteries

p‐Benzoquinone (BQ) is a promising cathode material for lithium‐ion batteries (LIBs) due to its high theoretical specific capacity and voltage. However, it suffers from a serious dissolution problem in organic electrolytes, leading to poor electrochemical performance. Herein, two BQ‐derived molecules with a near‐plane structure and relative large skeleton: 1,4‐bis(p‐benzoquinonyl)benzene (BBQB) and 1,3,5‐tris(p‐benzoquinonyl)benzene (TBQB) are designed and synthesized. They show greatly decreased solubility as a result of strong intermolecular interactions. As cathode materials for LIBs, they exhibit high carbonyl utilizations of 100% with high initial capacities of 367 and 397 mAh g^?1, respectively. Especially, BBQB with better planarity presents remarkably improved cyclability, retaining a high capacity of 306 mAh g^?1 after 100 cycles. The cycling stability of BBQB surpasses all reported BQ‐derived small molecules and most polymers. This work provides a new molecular structure design strategy to suppress the dissolution of organic electrode materials for achieving high performance rechargeable batteries.