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Due to higher energy density, high-voltage all-solid-state lithium batteries (ASSLBs) have attracted increasing attention. However, they require solid-state electrolytes (SSEs) with wide electrochemical stability windows (ESW, typically >4.2 V) and high-stability against the Li anode. Nevertheless, poly(ethylene oxide) (PEO), the most widely used solid polymer electrolyte (SPE), can’t tolerate a high-voltage over 4 V. Whether the main chain (–C–O–C–) or the terminal hydroxide group (–OH) is the limiting factor for the narrow ESW remains unknown. Herein, poly(ethylene glycol) (PEG) and poly(ethylene glycol)dimethyl ether (PEGDME) with different terminal groups are selected to answer this question. The results show that the reactive terminal –OH group is the limiting factor towards applicability against high voltage and the Li anode. Replacing –OH with more stable –OCH3 can significantly extend the ESW from 4.05 to 4.3 V, while improving the Li-anode compatibility as well (Li–Li symmetric cells stably run for 2500 h at 0.2 mA cm−2). Its practical application is further proved by developing PEGDME-based ASSLB pouch cells. The 0.53 mA cm−2 Li–LiFePO4 and 0.47 mA h cm−2 Li–LiNi0.5Mn0.3Co0.2O2 cells demonstrated high capacity retention of 97% and 90% after 210 cycles and 110 cycles, respectively. This work offers a new strategy for PEO-based high-voltage ASSLB development by changing the unstable terminal groups.

Most inorganic solid-state electrolytes (SSEs) suffer from incompatibility with oxide cathode materials and instability in ambient air, presenting major barriers for their application in high performance all-solid-state batteries (ASSLBs). Herein, we report a rationally designed halide-based Li3InCl6 SSE with a high ionic conductivity of 1.49 × 10−3 S cm−1 (25 °C). The Li3InCl6 SSE is stable towards oxide cathode materials (e.g., LiCoO2) without any interfacial treatment. By applying the Li3InCl6 SSEs, significantly enhanced electrochemical performances are achieved in terms of capacity and durability. Experimental investigations reveal that the Li3InCl6 can avoid side reactions between the SSEs and the oxide cathode materials and thus effectively improve the Li+ migration across the interface. Moreover, Li3InCl6 is highly stable in ambient air and possesses good ionic conductivity retention after a reheating process, further making it an attractive electrolyte for next-generation ASSLBs.

All-solid-state lithium–sulfur batteries (ASSLSBs) are promising candidates as the power source for future electric vehicles due to their high energy density and superior safety properties. However, one of the major challenges of state-of-the-art ASSLSBs is related to the high interfacial resistance resulting from the instability between the solid-state electrolyte (SSE) and electrodes and/or the side reactions between polysulfides and SSE. Herein, we propose and demonstrate the significant enhancement of the cycling stability of an ASSLSB through atomic layer deposition interfacial engineering on the polymer/oxide ceramic/polymer sandwich-structured SSE. The results show that as few as 10 cycles of ALD Al2O3 on the LATP can endow ASSLSBs with a discharge capacity of 823 mA h g−1 after 100 charge/discharge cycles, which is almost two times higher than that of the ASSLSB without an ALD coating and that of a Li–S battery with a liquid-based electrolyte. Such improvement is attributed not only to the blocking of the polysulfide shuttling effect via the use of a sandwich SSE but also the significant reduction of the side reaction between the polysulfide and oxide ceramic SSE, which introduces high interfacial resistance and degrades the electrochemical performance. The protection role and mechanism of the ALD layer is also confirmed and revealed by XRD, SEM and XPS measurements.

Silicon (Si) possesses the highest theoretical capacity as an anode material for lithium-ion batteries, and many efforts have been made to address the poor cycling stability issue that is associated with its huge volume changes during Li-Si alloying/de-alloying processes, mostly through the design of nanostructured materials. Herein, we report a simple cell configuration approach to improve the lithium storage performance of commercial nano-Si through the insertion of carbon nanofiber films (CNFs) as interlayers between the Si electrodes and separators. For this advanced cell configuration, commercial Si nanoparticle (Si NP) electrodes demonstrate a significantly improved reversible capacity (2700 mA h g-1 after 40 cycles at 50 mA g-1) and an ultralong cycle life (1250 mA h g-1 after 430 cycles at 1500 mA g-1). Even when cycled at 4 A g-1, the material still demonstrates a very high capacity of 870 mA h g-1. The excellent electrochemical performance of the Si NPs is attributed to the novel cell configuration. Macropores between the carbon nanofibers provide good access of the electrolyte to the Si NP electrodes. The 3D interconnected networks of the CNF interlayer not only decrease the internal charge transfer resistance and enhance the electron transport rate but also offer electron pathways along the CNF interlayer for cracked and disconnected Si NPs after cycling.

Triboelectric nanogenerators (TENGs) are promising innovative energy conversion devices that convert mechanical energy into electricity based on triboelectric friction. In this paper, we report the development of a single-electrode TENG (S-TENG) based on sponge-like porous polytetrafluoroethylene (PTFE) thin films. The porous PTFE thin films were fabricated via a facile approach by using deionized (DI) water as the soft template. The porosity effect on the output performance of the porous PTFE S-TENG was investigated under mechanical oscillations. The optimal porosity for achieving the maximum VOC output was found to be 5.1 V when the DI water volume fraction was 50%. The output voltage of the porous PTFE S-TENG is 1.8 times higher than that of the solid PTFE thin film based S-TENG under the same oscillation. The porous PTFE S-TENG can also generate considerable electricity by harvesting mechanical energy from human motions. An output voltage of 1.1 V was obtained when the S-TENG was pressed by a bare human hand. When pressed by a human hand within a latex glove, the output voltage reached 6.9 V, and the generated electric energy could instantaneously power 5 commercial green light emitting diodes (LEDs) without any energy storage process. This development of the porous PTFE S-TENG could open a new avenue towards developing self-powered personal electronics, owing to its flexibility, simple one-electrode structure, and ability to harvest mechanical energy from human motions.

Carbon nanofibers (CNFs) belong to a class of one-dimensional (1D) carbonaceous materials with excellent electronic conductivity, leading to their use as conductive additives in electrode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs). Additionally, CNFs show excellent lithium- and sodium-storage performance when used directly as anode materials via template and activation strategies to produce numerous intercalation sites. In the case of the non-carbon electrodes for LIBs & NIBs, CNFs are capable of functioning as electron conducting and porous substrates to enhance the overall electronic & ionic conductivity and stabilizing the structures of electrodes during cycling, facilitating the improvement of the electrochemical performance of non-carbon anode and cathode materials. In this review, we present a comprehensive summary of the recent progress of CNF application in LIBs and NIBs, focusing on the structural evolution and the resulting improvements in electrochemical performance and demonstrating the importance of advancements in CNF-based electrode materials.

Much attention is being paid to sodium ion batteries (SIBs) in view of the abundance of sodium sources and the cost issues. Layered transition metal dichalcogenides (such as MoS2 and WS2) have great potential to be used as anode materials for sodium storage owing to their high capacity. However, they still suffer from low rate capability and poor cycling stability. Compared to MoS2, WS2 has been scarcely studied in view of sodium storage. Here, we report, for the first time, a 3D porous interconnected WS2/C nanocomposite prepared by an electrostatic spray deposition (ESD) technique, which is composed of nano-0D WS2, nano-1D CNTs and nano-2D reduced graphene oxide. Such a nanocomposite shows excellent rate performance and long cycling stability, demonstrating great potential for its use as a sodium anode. Moreover, this strategy can be applied to other electrode materials for both lithium and sodium batteries.

Germanium is a promising anode material for lithium ion batteries (LIBs) due to its high specific capacity, but it still suffers from poor cyclability. A simple method was developed to synthesize Ge–reduced graphene oxide nanocomposites using organic germanium as a precursor. The nanocomposites exhibit improved electrochemical performance with a reversible specific capacity of 814 mA h g−1 after 50 cycles at a current density of 0.1 A g−1. When cycled at a high current density of 2 A g−1, they still deliver a reversible specific capacity of 690 mA h g−1 after 150 cycles. The improved electrochemical performance is attributed to the unique nanostructure (0D electroactive particles in 2D mixed conducting matrix), which conferred a variety of advantages: high flexibility of the graphene sheets for accommodating the volume change, good electrochemical coupling and short transport length for ions and electrons, enabling low contact resistances.

N-doped hollow porous carbon nanofibers (P-HCNFs) were prepared through pyrolyzation of hollow polypyrrole (PPy) nanofibers fabricated using electrospun polycaprolactone (PCL) nanofibers as a sacrificial template. When used as anode material for NIBs, P-HCNFs exhibit a reversible capacity of 160 mA h g−1 after 100 cycles at a current density of 0.05 A g−1. An improved rate capability is also obtained at even higher charge–discharge rates. When cycled at a current density of 2 A g−1, the electrode can still show a reversible capacity of 80 mA h g−1. The N-doped sites, one-dimensional nanotube structure, and functionalized surface of P-HCNFs are capable of rapidly and reversibly accommodating sodium ions through surface adsorption and redox reactions. Therefore, P-HCNF is a promising anode material for next-generation NIBs.

A porous Ge@C composite was synthesized by magnesiothermic reduction reaction of GeO2, Mg powder and glucose followed by an etching process with HCl solution. Compared to a porous Ge electrode, the porous Ge@C composite electrode delivers better cycling stability (∼100% capacity retention after 100 cycles at the 0.2 C rate) and higher rate capability (440 mA h g−1 at 1800 mA g−1). The improved electrochemical performance results from the synergistic effect of the 3D interconnected porous structure and the carbon shells. The local pores could buffer the volume change and the conductive carbon shell could prevent the aggregation of Ge as well as enhance the electronic conductivity of the whole electrode.

Flexible and free-standing sulphur/(PCNFs-CNT) composite (S@PCNFs-CNT) electrode was successfully prepared by infiltrating sulfur into microporous carbon nanofibers-carbon nanotube (PCNFs-CNT) composite. When used as a cathode material for Li-S batteries, the S@PCNFs-CNT exhibits much better cycle performance and rate performance compared to CNT-free S@PCNFs. It delivers a reversible capacity of 637 mA h g(-1) after 100 cycles at 50 mA g(-1) and a rate capability of 437 mA h g(-1) at 1 A g(-1). The improved electrochemical performance is attributed to synergistic effect of the 3D interconnected structure, the additive of CNT, and the uniform distribution of micropores (2 nm) in the PCNFs-CNT matrix. Our results indicate the potential suitability of PCNFs-CNT for efficient, free-standing, and high-performance batteries.