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To boost the energy density as well as address the safety issues, an effective strategy is to replace the liquid electrolytes with solid-state electrolytes (SSEs). However, the current SSEs usually...

The practical application of lithium–sulfur (Li–S) batteries is hindered by poor cycling stability mainly derived from the shuttling of lithium polysulfides (LiPSs). Catalysis, which can promote th...

Designing composite structures of active materials is critical for high-performance lithium-ion batteries, as it determines the reversibility of lithium-ion insertion and extraction of the electrod...

Solid electrolytes are considered as strong alternatives for conventional liquid electrolytes to overcome the safety issues of next-generation high-energy-density lithium metal batteries (LMBs). Although Li1.5Al0.5Ge1.5(PO4)3 (LAGP) has satisfied ionic conductivity at room temperature (∼10-4 S cm-1), high stability in air, and can be easily sintered, it still suffers from instability of the lithium metal. Moreover, the large interfacial resistance between solid electrolytes and solid electrodes and the stress generated by the volumetric change of lithium metal anodes during cycling would deteriorate the performance of LMBs. Here, we report an effective solution to overcome the abovementioned problems by introducing a three-dimensional gel polymer electrolyte at the interface between LAGP pellets and lithium metal anodes, achieving stable cycling of LiFePO4//Li cells at room temperature for 300 cycles. Besides, the degeneration mechanisms of the interfaces of LAGP pellets under different conditions are compared, and peculiar properties different from their counterparts were found.

A nitrogen (N)-doped porous carbon sheet is prepared by in situ polymerization of pyrrole on both sides of graphene oxide, following which the polypyrrole layers are then transformed to the N-doped porous carbon layers during the following carbonization, and a sandwich structure is formed. Such a sheet-like structure possesses a high specific surface area and, more importantly, guarantees the sufficient utilization of the N-doping active porous sites. The internal graphene layer acts as an excellent electron pathway, and meanwhile, the external thin and porous carbon layer helps to decrease the ion diffusion resistance during electrochemical reactions. As a result, this sandwich structure exhibits prominent catalytic activity toward the oxygen reduction reaction in alkaline media, as evidenced by a more positive onset potential, a larger diffusion-limited current, better durability and poison-tolerance than commercial Pt/C. This study shows a novel method of using graphene to template the traditional poro...

Vanadium pentoxide (V2O5) is considered a promising cathode material for advanced lithium-ion batteries owing to its high specific capacity and low cost. However, the application of V2O5-based electrodes has been hindered because of their inferior conductivity, cycling stability, and power performance. Herein, hierarchical sisal-like V2O5 microstructures consisting of primary one-dimensional (1D) nanobelts with [001] facets orientation growth and rich oxygen vacancies are synthesized through a facile hydrothermal process using polyoxyethylene-20-cetyl-ether as the surface control agent, followed by calcination. The primary 1D nanobelt shortens the transfer path of electrons and ions, and the stable {001} facets could reduce the side reaction at the interface of electrode/electrolyte, simultaneously. Moreover, the formation of low valence state vanadium would generate the oxygen vacancies to facilitate lithium-ion diffusion. As a result, the sisal-like V2O5 manifests excellent electrochemical performances, including high specific capacity (297 mA h g-1 at a current of 0.1 C) and robust cycling performance (capacity fading 0.06% per cycle). This work develops a controllable method to craft the hierarchical sisal-like V2O5 microstructures with excellent high rate and long-term cyclic stability.

Among various two-dimensional compounds, transition metal dichalcogenides (TMDs or MX2) are a group of materials attracting growing research interest for potential applications as battery electrodes. Here we systematically investigate the electrochemical performance of a series of MX2 (M = Mo, W, Nb, Ta; X = S, Se) upon Li/Na intercalation through first-principles calculations. MoX2 and WX2 were found to have lower voltages while those of NbX2 and TaX2 were higher than 1.5 V. By applying the rigid-band model, we found that the energy gained for electrons to transfer from Li/Na to MX2 could serve as a descriptor for characterizing voltages of MX2.The linear relation between the descriptor and voltages is useful for screening candidates for electrodes with desired voltage. Migration barriers for Li/Na ions were approximately 0.3 eV in MoX2/WX2 and 0.5 eV in NbX2/TaX2. The low barriers suggest a reasonable rate performance when these TMDs are used as electrodes. By stacking different MX2 with distinct proper...

Recently, the lithium–oxygen (Li–O2) battery has attracted much interest due to its ultrahigh theoretical energy density. However, its potential application is limited by an unstable electrolyte system, low round-trip efficiency, and poor cyclic performance. In this study, we present a new electrolyte based on N,N′-dimethylpropyleneurea (DMPU) applied for the Li–O2 battery. This electrolyte possesses high ionic conductivity and achieves a low discharge/charge voltage gap of 0.6 V, which is mainly due to the possible one-electron charge transfer mechanism. The introduction of the antioxidant butylatedhydroxytoluene (BHT) as an additive stabilizes the superoxide radical by chemical adsorption and improves the cyclic performance remarkably. Thus, this new electrolyte system may be one of the candidates for Li–O2 batteries.

An in-depth understanding of (de)lithiation induced phase transition in electrode materials is crucial to grasp their structure–property relationships and provide guidance to the design of more desirable electrodes. By operando synchrotron XRD (SXRD) measurement and Density Functional Theory (DFT) based calculations, we discover a reversible first-order phase transition for the first time during (de)lithiation of CeO2 nanoparticles. The LixCeO2 compound phase is identified to possess the same fluorite crystal structure with FM3M space group as that of the pristine CeO2 nanoparticles. The SXRD determined lattice constant of the LixCeO2 compound phase is 0.551 nm, larger than that of 0.541 nm of the pristine CeO2 phase. The DFT calculations further reveal that the Li induced redistribution of electrons causes the increase in the Ce–O covalent bonding, the shuffling of Ce and O atoms, and the jump expansion of lattice constant, thereby resulting in the first-order phase transition. Discovering the new phase ...

The effects of number of graphene layers (n) and size of multilayer graphene sheets on thermal conductivities (TCs) of their epoxy composites are investigated. Molecular dynamics simulations show that the in-plane TCs of graphene sheets and the TCs across the graphene/epoxy interface simultaneously increase with increasing n. However, such higher TCs of multilayer graphene sheets will not translate into higher TCs of bulk composites unless they have large lateral sizes to maintain their aspect ratios comparable to the monolayer counterparts. The benefits of using large, multilayer graphene sheets are confirmed by experiments, showing that the composites made from graphite nanoplatelets (n10) with over 30 μm in diameter deliver a TC of ∼1.5 W m(-1) K(-1) at only 2.8 vol %, consistently higher than those containing monolayer or few-layer graphene at the same graphene loading. Our findings offer a guideline to use cost-effective multilayer graphene as conductive fillers for various thermal management applications.

One of the key challenges toward high-power Li-ion batteries is to develop cheap, easy-to-prepare materials that combine high volumetric and gravimetric energy density with high power densities and a long cycle life. This requires electrode materials with large tap densities, which generally compromises the charge transport and hence the power density. Here densely packed Li4Ti5O12 (LTO) submicrospheres are prepared via a simple and easily up-scalable self-assembly process, resulting in very high tap densities (1.2 g·cm–3) and displaying exceptionally stable long-term high rate cyclic performance. The specific capacities at a (dis)charge rate of 10 and 20 C reach 148.6 and 130.1 mAh g–1, respectively. Moreover, the capacity retention ratio is 97.3% after 500 cycles at 10 C in a half cell, and no obvious capacity reduction is found even after 8000 cycles at 30 C in a full LiFePO4/LTO battery. The excellent performance is explained by the abundant presence of grain boundaries between the nanocrystallites in...

A preheated high-temperature environment is believed to be critical for a chemical-exfoliation-based production of graphenes starting from graphite oxide, a belief that is based on not only experimental but also theoretical viewpoints. A novel exfoliation approach is reported in this study, and the exfoliation process is realized at a very low temperature, which is far below the proposed critical exfoliation temperature, by introducing a high vacuum to the exfoliation process. Owing to unique surface chemistry, low-temperature exfoliated graphenes demonstrate an excellent energy storage performance, and the electrochemical capacitance is much higher than that of the high-temperature exfoliated ones. The low-temperature exfoliation approach presents us with a possibility for a mass production of graphenes at low cost and great potentials in energy storage applications of graphene-based materials.