An Organic Cathode for Potassium Dual-Ion Full Battery

Potassium-based dual-ion full batteries (PDIBs) were developed with graphite anode, polytriphenylamine (PTPAn) cathode, and KPF₆-based electrolyte. The PDIBs delivered a reversible capacity of 60 mA h g^–1 at a median discharge voltage of 3.23 V at 50 mA g^–1, with superior rate performance and long-term cycling stability over 500 cycles (capacity retention of 75.5%). Unlike the traditional dual-ion batteries, the operation mechanism of the PDIBs with PTPAn cathode is that the PF₆^– ions interacted with the nitrogen atom reversibly in the PTPAn cathode and the K⁺ ions were intercalated/deintercalated into/from the graphite anode during the charge/discharge process

Atomic-Scale Control of Silicon Expansion Space as Ultrastable Battery Anodes

Development of electrode materials with high capability and long cycle life are central issues for lithium-ion batteries (LIBs). Here, we report an architecture of three-dimensional (3D) flexible silicon and graphene/carbon nanofibers (FSiGCNFs) with atomic-scale control of the expansion space as the binder-free anode for flexible LIBs. The FSiGCNFs with Si nanoparticles surrounded by accurate and controllable void spaces ensure excellent mechanical strength and afford sufficient space to overcome the damage caused by the volume expansion of Si nanoparticles during charge and discharge processes. This 3D porous structure possessing built-in void space between the Si and graphene/carbon matrix not only limits most solid-electrolyte interphase formation to the outer surface, instead of on the surface of individual NPs, and increases its stability but also achieves highly efficient channels for the fast transport of both electrons and lithium ions during cycling, thus offering outstanding electrochemical performance (2002 mAh g^–1 at a current density of 700 mA g^–1 over 1050 cycles corresponding to 3840 mAh g^–1 for silicon alone and 582 mAh g^–1 at the highest current density of 28 000 mA g^–1)

Carbon Nanoscrolls for Aluminum Battery

This design provides a scalable route for <i>in situ</i> synthesizing of special carbon nanoscrolls as the cathode for an aluminum battery. The frizzy architectures are generated by a few graphene layers convoluting into the hollow carbon scroll, possessing rapid electronic transportation channels, superior anion storage capability, and outstanding ability of accommodating a large volume expansion during the cycling process. The electrochemical performance of the carbon nanoscroll cathode is fully tapped, displaying an excellent reversible discharge capacity of 104 mAh g^–1 at 1000 mA g^–1. After 55 000 cycles, this cathode retains a superior reversible specific capacity of 101.24 mAh g^–1 at an ultrafast rate of 50 000 mA g^–1, around 100% of the initial capacity, which demonstrates a superior electrochemical performance. In addition, anionic storage capability and structural stability are discussed in detail. The battery capacity under a wide temperature range from −80 to 120 °C is examined. At a low temperature of −25 °C, the battery delivers a discharge capacity of 62.83 mAh g^–1 after 10 000 cycles, obtaining a capacity retention near 100%. In addition, it achieves a capacity of 99.5 mAh g^–1 after 4000 cycles at a high temperature of 80 °C, with a capacity retention close to 100%. The carbon nanoscrolls possess an outstanding ultrafast charging/variable discharging rate performance surpassing all the batteries previously reported, which are highly promising for being applied in energy storage fields

Encapsulating Gold Nanoparticles or Nanorods in Graphene Oxide Shells as a Novel Gene Vector

Surface modification of inorganic nanoparticles (NPs) is extremely necessary for biomedical applications. However, the processes of conjugating ligands to NPs surface are complicated with low yield. In this study, a hydrophilic shell with excellent biocompatibility was successfully constructed on individual gold NPs or gold nanorods (NRs) by encapsulating NPs or NRs in graphene oxide (GO) nanosheets through electrostatic self-assembly. This versatile and facile approach remarkably decreased the cytotoxicity of gold NPs or NRs capping with surfactant cetyltrimethylammonium bromide (CTAB) and provided abundant functional groups on NPs surface for further linkage of polyethylenimine (PEI). The PEI-functionalized GO-encapsulating gold NPs (GOPEI-AuNPs) were applied to delivery DNA into HeLa cells as a novel gene vector. It exhibited high transfection efficiency of 65% while retaining 90% viability of HeLa cells. The efficiency was comparable to commercialized PEI 25 kDa with the cytotoxicity much less than PEI. Moreover, the results on transfection efficiency was higher than PEI-functionalized GO, which can be attributed to the small size of NPs/DNA complex (150 nm at the optimal w/w ratio) and the spherical structure facilitating the cellular uptake. Our work paves the way for future studies focusing on GO-encapsulating, NP-based nanovectors

Offset Initial Sodium Loss To Improve Coulombic Efficiency and Stability of Sodium Dual-Ion Batteries

Sodium dual-ion batteries (NDIBs) are attracting extensive attention recently because of their low cost and abundant sodium resources. However, the low capacity of the carbonaceous anode would reduce the energy density, and the formation of the solid-electrolyte interphase (SEI) in the anode during the initial cycles will lead to large amount consumption of Na⁺ in the electrolyte, which results in low Coulombic efficiency and inferior stability of the NDIBs. To address these issues, a phosphorus-doped soft carbon (P-SC) anode combined with a presodiation process is developed to enhance the performance of the NDIBs. The phosphorus atom doping could enhance the electric conductivity and further improve the sodium storage property. On the other hand, an SEI could preform in the anode during the presodiation process; thus the anode has no need to consume large amounts of Na⁺ to form the SEI during the cycling of the NDIBs. Consequently, the NDIBs with P-SC anode after the presodiation process exhibit high Coulombic efficiency (over 90%) and long cycle stability (81 mA h g^–1 at 1000 mA g^–1 after 900 cycles with capacity retention of 81.8%), far more superior to the unsodiated NDIBs. This work may provide guidance for developing high performance NDIBs in the future

Constructing Three-Dimensional Flexible Lithiophilic Scaffolds with Bi₂O₃ Nanosheets toward Stable Li Metal Anodes

The practical application of lithium metal batteries (LMBs) is obstructed by the uncontrollable dendrite growth and large volume change. Herein, we construct a flexible carbon cloth modified with Bi2O3 nanosheets (Bi2O3/CC) as a three-dimensional (3D) lithiophilic skeleton to regulate uniform Li nucleation and deposition. Benefiting from the initial lithiation, dense lithiophilic Li3Bi layers with lithium conductor Li2O (Li3Bi/Li2O) are in-situ-formed through conversion and alloying reactions, which can promote adsorption ability of lithium and improve the speed of Li+ transport according to DFT calculations, thus boosting homogeneous Li plating/stripping behavior. Meanwhile, the conductive 3D structure effectively suppresses Li dendrite formation by reducing the local current density and eliminates volume change. Consequently, the Bi2O3/CC facilitates a high Coulombic efficiency and dendrite-free morphology, near-zero volume change, and superior cyclic stability over 2400 h at 1 mA cm–2 with an ultralow overpotential of 11 mV. Notably, there is no obvious dendritic morphology in Bi2O3/CC even under an ultrahigh areal capacity of 20 mAh cm–2. Moreover, the Li@Bi2O3/CC-LiFePO4 full cell also achieves outstanding cycling performance and rate capability, shedding light on the facile design of the 3D lithiophilic host for advanced lithium-metal anodes

Bacteria Absorption-Based Mn₂P₂O₇–Carbon@Reduced Graphene Oxides for High-Performance Lithium-Ion Battery Anodes

The development of freestanding flexible electrodes with high capacity and long cycle-life is a central issue for lithium-ion batteries (LIBs). Here, we use bacteria absorption of metallic Mn²⁺ ions to <i>in situ</i> synthesize natural micro-yolk–shell-structure Mn₂P₂O₇–carbon, followed by the use of vacuum filtration to obtain Mn₂P₂O₇–carbon@reduced graphene oxides (RGO) papers for LIBs anodes. The Mn₂P₂O₇ particles are completely encapsulated within the carbon film, which was obtained by carbonizing the bacterial wall. The resulting carbon microstructure reduces the electrode–electrolyte contact area, yielding high Coulombic efficiency. In addition, the yolk–shell structure with its internal void spaces is ideal for sustaining volume expansion of Mn₂P₂O₇ during charge/discharge processes, and the carbon shells act as an ideal barrier, limiting most solid–electrolyte interphase formation on the surface of the carbon films (instead of forming on individual particles). Notably, the RGO films have high conductivity and robust mechanical flexibility. As a result of our combined strategies delineated in this article, our binder-free flexible anodes exhibit high capacities, long cycle-life, and excellent rate performance