Enhanced Ion Conductivity in Conducting Polymer Binder for High‐Performance Silicon Anodes in Advanced Lithium‐Ion Batteries

Polymer binders with high ion and electron conductivities are prepared by assembling ionic polymers (polyethylene oxide and polyethylenimine) onto the electrically conducting polymer poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) chains. Crosslinking, chemical reductions, and electrostatics increase the modulus of the binders and maintain the integrity of the anode. The polymer binder shows lithium‐ion diffusivity and electron conductivity that are 14 and 90 times higher than those of the widely used carboxymethyl cellulose (with acetylene black) binder, respectively. The silicon anode with the polymer binder has a high reversible capacity of over 2000 mA h g^?1 after 500 cycles at a current density of 1.0 A g^?1 and maintains a superior capacity of 1500 mA h g^?1 at a high current density of 8.0 A g^?1.     

Hard Carbon Microtubes Made from Renewable Cotton as High‐Performance Anode Material for Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) have attracted more and more attention for scalable electrical energy storage due to the abundance and wide distribution of Na resources. However, the anode still remains a great challenge for the application of SIBs. Here the production of uniform hard carbon microtubes (HCTs) made from natural cotton through one simple carbonization process and their application as an anode are reported. The study shows that the electrochemical performance of the HCTs is seriously affected by the carbonization temperature due to the difference in their microstructure and heteroatomic content. The HCTs carbonized at 1300 °C deliver the highest reversible capacity of 315 mAh g^?1 and good rate capability due to their unique tubular structure. This contribution not only provides a new approach for the preparation of hard carbon materials with unique tubular microstructure using natural inspiration, but it also deepens the fundamental understanding of the sodium storage mechanism.     

Silicon Anode with High Initial Coulombic Efficiency by Modulated Trifunctional Binder for High‐Areal‐Capacity Lithium‐Ion Batteries

High‐capacity electrode materials play a vital role for high‐energy‐density lithium‐ion batteries. Silicon (Si) has been regarded as a promising anode material because of its outstanding theoretical capacity, but it suffers from an inherent volume expansion problem. Binders have demonstrated improvements in the electrochemical performance of Si anodes. Achieving ultrahigh‐areal‐capacity Si anodes with rational binder strategies remains a significant challenge. Herein, a binder‐lithiated strategy is proposed for ultrahigh‐areal‐capacity Si anodes. A hard/soft modulated trifunctional network binder (N‐P‐LiPN) is constructed by the partially lithiated hard polyacrylic acid as a framework and partially lithiated soft Nafion as a buffer via the hydrogen binding effect. N‐P‐LiPN has strong adhesion and mechanical properties to accommodate huge volume change of the Si anode. In addition, lithium‐ions are transferred via the lithiated groups of N‐P‐LiPN, which significantly enhances the ionic conductivity of the Si anode. Hence, the Si@N‐P‐LiPN electrodes achieve the highest initial Coulombic efficiency of 93.18% and a stable cycling performance for 500 cycles at 0.2 C. Specially, Si@N‐P‐LiPN electrodes demonstrate an ultrahigh‐areal‐capacity of 49.59 mAh cm^?2. This work offers a new approach for inspiring the battery community to explore novel binders for next‐generation high‐energy‐density storage devices.     

Lithium‐Pretreated Hard Carbon as High‐Performance Sodium‐Ion Battery Anodes

Hard carbon (HC) is the state‐of‐the‐art anode material for sodium‐ion batteries (SIBs). However, its performance has been plagued by the limited initial Coulombic efficiency (ICE) and mediocre rate performance. Here, experimental and theoretical studies are combined to demonstrate the application of lithium‐pretreated HC (LPHC) as high‐performance anode materials for SIBs by manipulating the solid electrolyte interphase in tetraglyme (TEGDME)‐based electrolyte. The LPHC in TEGDME can 1) deliver > 92% ICE and ≈220 mAh g^?1 specific capacity, twice of the capacity (≈100 mAh g^?1) in carbonate electrolyte; 2) achieve > 85% capacity retention over 1000 cycles at 1000 mA g^?1 current density (4 C rate, 1 C = 250 mA g^?1) with a specific capacity of ≈150 mAh g^?1, ≈15 times of the capacity (10 mAh g^?1) in carbonate. The full cell of Na₃V₂(PO₄)₃‐LPHC in TEGDME demonstrated close to theoretical specific capacity of ≈98 mAh g^?1 based on Na₃V₂(PO₄)₃ cathode, ≈2.5 times of the value (≈40 mAh g^?1) with nontreated HC. This work provides new perception on the anode development for SIBs.     

Soft Carbon as Anode for High‐Performance Sodium‐Based Dual Ion Full Battery

Sodium‐based dual ion full batteries (NDIBs) are reported with soft carbon as anode and graphite as cathode for the first time. The NDIBs operate at high discharge voltage plateau of 3.58 V, with superior discharge capacity of 103 mA h g^?1, excellent rate performance, and long‐term cycling stability over 800 cycles with capacity retention of 81.8%. The mechanism of Na⁺ and PF₆^? insertion/desertion during the charging/discharging processes is proposed and discussed in detail, with the support of various spectroscopies.     

Silica Restricting the Sulfur Volatilization of Nickel Sulfide for High‐Performance Lithium‐Ion Batteries

Nickel sulfides are regarded as promising anode materials for advanced rechargeable lithium‐ion batteries due to their high theoretical capacity. However, capacity fade arising from significant volume changes during operation greatly limits their practical applications. Herein, confined NiS_x@C yolk–shell microboxes are constructed to address volume changes and confine the active material in the internal void space. Having benefited from the yolk–shell structure design, the prepared NiS_x@C yolk–shell microboxes display excellent electrochemical performance in lithium‐ion batteries. Particularly, it delivers impressive cycle stability (460 mAh g^?1 after 2000 cycles at 1 A g^?1) and superior rate performance (225 mAh g^?1 at 20 A g^?1). Furthermore, the lithium storage mechanism is ascertained with in situ synchrotron high‐energy X‐ray diffractions and in situ electrochemical impedance spectra. This unique confined yolk–shell structure may open up new strategies to create other advanced electrode materials for high performance electrochemical storage systems.     

3D Hyperbranched Hollow Carbon Nanorod Architectures for High‐Performance Lithium‐Sulfur Batteries

Lithium‐sulfur batteries have been plagued for a long time by low Coulombic efficiency, fast capacity loss, and poor high rate performance. Here, the synthesis of 3D hyperbranched hollow carbon nanorod encapsulated sulfur nanocomposites as cathode materials for lithium‐sulfur batteries is reported. The sulfur nanocomposite cathodes deliver a high specific capacity of 1378 mAh g^‐1 at a 0.1C current rate and exhibit stable cycling performance. The as‐prepared sulfur nanocomposites also achieve excellent high rate capacities and cyclability, such as 990 mAh g^‐1 at 1C, 861 mAh g^‐1 at 5C, and 663 mAh g^‐1 at 10C, extending to more than 500 cycles. The superior electrochemical performance are ascribed to the unique 3D hyperbranched hollow carbon nanorod architectures and high length/radius aspect ratio of the carbon nanorods, which can effectively prevent the dissolution of polysulfides, decrease self‐discharge, and confine the volume expansion on cycling. High capacity, excellent high‐rate performance, and long cycle life render the as‐developed sulfur/carbon nanorod nanocomposites a promising cathode material for lithium‐sulfur batteries.     

Iron‐Oxide‐Based Advanced Anode Materials for Lithium‐Ion Batteries

Iron oxides, such as Fe₂O₃ and Fe₃O₄, have recently received increased attention as very promising anode materials for rechargeable lithium‐ion batteries (LIBs) because of their high theoretical capacity, non‐toxicity, low cost, and improved safety. Nanostructure engineering has been demonstrated as an effective approach to improve the electrochemical performance of electrode materials. Here, recent research progress in the rational design and synthesis of diverse iron oxide‐based nanomaterials and their lithium storage performance for LIBs, including 1D nanowires/rods, 2D nanosheets/flakes, 3D porous/hierarchical architectures, various hollow structures, and hybrid nanostructures of iron oxides and carbon (including amorphous carbon, carbon nanotubes, and graphene). By focusing on synthesis strategies for various iron‐oxide‐based nanostructures and the impacts of nanostructuring on their electrochemical performance, novel approaches to the construction of iron‐oxide‐based nanostructures are highlighted and the importance of proper structural and compositional engineering that leads to improved physical/chemical properties of iron oxides for efficient electrochemical energy storage is stressed. Iron‐oxide‐based nanomaterials stand a good chance as negative electrodes for next generation LIBs.     

Electrochemical Performance of Porous Carbon/Tin Composite Anodes for Sodium‐Ion and Lithium‐Ion Batteries

The electrochemical performance of mesoporous carbon (C)/tin (Sn) anodes in Na‐ion and Li‐ion batteries is systematically investigated. The mesoporous C/Sn anodes in a Na‐ion battery shows similar cycling stability but lower capacity and poorer rate capability than that in a Li‐ion battery. The desodiation potentials of Sn anodes are approximately 0.21 V lower than delithiation potentials. The low capacity and poor rate capability of C/Sn anode in Na‐ion batteries is mainly due to the large Na‐ion size, resulting in slow Na‐ion diffusion and large volume change of porous C/Sn composite anode during alloy/dealloy reactions. Understanding of the reaction mechanism between Sn and Na ions will provide insight towards exploring and designing new alloy‐based anode materials for Na‐ion batteries.     

Exploiting Lithium–Ether Co‐Intercalation in Graphite for High‐Power Lithium‐Ion Batteries

The intercalation of lithium ions into graphite electrode is the key underlying mechanism of modern lithium‐ion batteries. However, co‐intercalation of lithium‐ions and solvent into graphite is considered undesirable because it can trigger the exfoliation of graphene layers and destroy the graphite crystal, resulting in poor cycle life. Here, it is demonstrated that the [lithium–solvent]⁺ intercalation does not necessarily cause exfoliation of the graphite electrode and can be remarkably reversible with appropriate solvent selection. First‐principles calculations suggest that the chemical compatibility of the graphite host and [lithium–solvent]⁺ complex ion strongly affects the reversibility of the co‐intercalation, and comparative experiments confirm this phenomenon. Moreover, it is revealed that [lithium–ether]⁺ co‐intercalation of natural graphite electrode enables much higher power capability than normal lithium intercalation, without the risk of lithium metal plating, with retention of ≈87% of the theoretical capacity at current density of 1 A g^?1. This unusual high rate capability of the co‐intercalation is attributed to the (i) absence of the desolvation step, (ii) negligible formation of the solid–electrolyte interphase on graphite surface, and (iii) fast charge‐transfer kinetics. This work constitutes the first step toward the utilization of fast and reversible [lithium–solvent]⁺ complex ion intercalation chemistry in graphite for rechargeable battery technology.     

High‐Efficiency Large‐Area Carbon Nanotube‐Silicon Solar Cells

Currently studied carbon nanotube‐silicon (CNT‐Si) solar cells are based on relatively small active areas (typically <0.15 cm²); increasing the active area generally leads to reduced power conversion efficiencies. This study reports CNT‐Si solar cells with active areas of more than 2 cm² for single cells, yet still achieving cell efficiencies of about 10%, which is the first time for CNT‐Si solar cells with an active area more than 1 cm² to reach the level for real applications. In this work, a controlled number of flattened highly conductive CNT strips is added, in simple arrangement, to form a CNT‐Si solar cell with CNT strips in which the middle film makes heterojunctions with Si while the top strips act as self‐similar top electrodes, like conventional metal grids. The CNT strips, directly condensed from as‐grown CNT films, not only improve the CNT‐Si junctions, but also enhance the conductivity of top electrodes without introducing contact barrier when the CNT strips are added onto the film. This property may facilitate the development of large‐area high‐performance CNT or graphene‐Si solar cells.     

Li3N as a Cathode Additive for High‐Energy‐Density Lithium‐Ion Batteries

The formation of a solid‐electrolyte interphase on the anode surface of an Li‐ion battery using an organic liquid electrolyte robs Li⁺ irreversibly form the cathode on the initial charge if the cells are fabricated in the discharged state. In order to increase the cathode capacity, the use of Li₃N as a sacrificial source of Li⁺ on the initial charge has been evaluated chemically and electrochemically as an additive to an LiCoO₂ cathode. Li₃N is shown to be chemically stable in a dry atmosphere as small particles with fresh surfaces and can increase the reversible capacities of a full cell without compromising the rate capability of the cells.     

Ultrahigh‐Energy‐Density Lithium‐Ion Batteries Based on a High‐Capacity Anode and a High‐Voltage Cathode with an Electroconductive Nanoparticle Shell

The combination of high‐capacity anodes and high‐voltage cathodes has garnered a great deal of attention in the pursuit of high‐energy‐density lithium‐ion batteries. As a facile and scalable electrode‐architecture strategy to achieve this goal, a direct one‐pot decoration of high‐capacity silicon (Si) anode materials and of high‐voltage LiCoO₂ (LCO) cathode materials is demonstrated with colloidal nanoparticles composed of electroconductive antimony‐doped tin oxide (ATO). The unusual ATO nanoparticle shells enhance electronic conduction in the LCO and Si electrode materials and mitigate unwanted interfacial side reactions between the electrode materials and liquid electrolytes. The ATO‐coated LCO materials (ATO‐LCO) enable the construction of a high‐mass‐loading cathode and suppress the dissolution of cobalt and the generation of by‐products during high‐voltage cycling. In addition, the ATO‐coated Si (ATO‐Si) anodes exhibit highly stable capacity retention upon cycling. Integration of the high‐voltage ATO‐LCO cathode and high‐capacity ATO‐Si anode into a full cell configuration brings unprecedented improvements in the volumetric energy density and in the cycling performance compared to a commercialized cell system composed of LCO/graphite.     

An Antiaging Electrolyte Additive for High‐Energy‐Density Lithium‐Ion Batteries

High‐capacity Li‐rich layered oxide cathodes along with Si‐incorporated graphite anodes have high reversible capacity, outperforming the electrode materials used in existing commercial products. Hence, they are potential candidates for the development of high‐energy‐density lithium‐ion batteries (LIBs). However, structural degradation induced by loss of interfacial stability is a roadblock to their practical use. Here, the use of malonic acid‐decorated fullerene (MA‐C₆₀) with superoxide dismutase activity and water scavenging capability as an electrolyte additive to overcome the structural instability of high‐capacity electrodes that hampers the battery quality is reported. Deactivation of PF₅ by water scavenging leads to the long‐term stability of the interfacial structures of electrodes. Moreover, an MA‐C₆₀‐added electrolyte deactivates the reactive oxygen species and constructs an electrochemically robust cathode‐electrolyte interface for Li‐rich cathodes. This work paves the way for new possibilities in the design of electrolyte additives by eliminating undesirable reactive substances and tuning the interfacial structures of high‐capacity electrodes in LIBs.     

Structural Engineering of Multishelled Hollow Carbon Nanostructures for High‐Performance Na‐Ion Battery Anode

Hard carbon has long been considered the leading candidate for anode materials of Na‐ion batteries. Intensive research efforts have been carried out in the search of suitable carbon structure for an improved storage capability. Herein, an anode based on multishelled hollow carbon nanospheres, which are able to deliver an outstanding electrochemical performance with an extraordinary reversible capacity of 360 mAh g^?1 at 30 mA g^?1, is designed. An interesting dependence of the electrochemical properties on the multishelled structural features is identified: with an increase in the shell number of the model carbon materials, the sloping capacity in the charge/discharge curve remains almost unchanged while the plateau capacity continuously increases, suggesting an adsorption‐filling Na‐storage mechanism for the multishelled hollow hard carbon materials. The findings not only provide new perspective in the structural design of high‐performance anode materials, but also shed light on the complicated mechanism behind Na‐storage by hard carbon.