Constructing anion-derived solid electrolyte interphase (SEI) by recruiting anions into the solvation sheath of Li⁺ is extremely conducive to restrain the dendrite growth of Li metal anode. However, the presence of anions in the solvation sheath of Li⁺ is severely hindered by the solvents with strong coordinating ability in conventional electrolyte. Herein, we boost the content of anions in the primary solvation sheath of Li⁺ by employing a solvent with low donor number, 2-methyltetrahydrofuran, inducing an anion-derived SEI. As a result, the Li||Cu cells show a high average Coulombic efficiency (> 99%) over 500 cycles and the Li||LiFePO₄ cells under a low negative/positive capacity ratio of 2:1 exhibit an impressive capacity retention of 90% after 100 cycles. This work provides insights on constructing stable anion-derived SEI and offers guidance in designing electrolytes for stable Li metal batteries.

Layered lithium transition metal oxide (LTMO) cathode materials have attracted much attention for lithium-ion batteries and are shining in the current market. Establishing a clear structure–performance relationship is necessary for the performance improvement of LTMO cathode materials. The combination of synchrotron X-ray diffraction (XRD) with high intensity and XRD Rietveld refinement is powerful for revealing the structural characteristics of LTMO cathode materials. This review summarizes the application of high energy XRD and Rietveld refinement in LTMO cathode materials, including the brief introduction of synchrotron XRD and Rietveld refinement and their applications in understanding the structural evolution related to the synthetic, thermal runaway, cycling, and high-rate charge/discharge process of LTMO cathode materials. Synchrotron XRD can provide insights into the intermediates and reaction paths in the synthesis process, the origin of thermal runaway, the mechanism of structural decay during cycles, and the structural evolution during high-rate charging/discharging. Future works should focus on the development of higher intensity X-rays to gain more in-depth insights into the intrinsic relationship between their structural characteristics and properties.

During operation of a lithium metal battery, uneven lithium deposition often results in the growth of lithium dendrites and causes a rapid decay in battery performance and even leads to safety issues. This is still the main hurdle hindering the practical application of lithium metal anodes. We report a new type of Janus separator fabricated by introducing a molecular sieve coating on the surface of the polypropylene separator that serves as a redistribution layer for lithium ions. Our results show that using this layer, the growth of lithium dendrites can be largely inhibited and the battery performance greatly improved. In a typical Li||Cu half-cell with the Janus separator, the Coulombic efficiency of the lithium metal anode can be maintained at > 98.5% for over 500 cycles. The cycling life span is also extended by a factor of 8 in the Li||Li symmetric cell. Furthermore, the high-strength coating improves the mechanical properties of the separator, thus enhancing safety. The effectiveness of our strategy is demonstrated by both the inhibited growth of lithium dendrites and the improved battery performance. Our methodology could eventually be generalized for electrode protection in other battery systems.

Nanostructured organic tetralithium salts of 2, 5-dihydroxyterephthalic acid (Li₄C₈H₂O₆) supported on graphene were prepared via a facile recrystallization method. The optimized composite with 75 wt.% Li₄C₈H₂O₆ was evaluated as an anode with redox couples of Li₄C₈H₂O₆/Li₆C₈H₂O₆ and as a cathode with redox couples of Li₄C₈H₂O₆/Li₂C₈H₂O₆ for Li-ion batteries, exhibiting a high-rate capability (10 C) and long cycling life (1, 000 cycles). Moreover, in an all-organic symmetric Li-ion battery, this dual-function electrode retained capacities of 191 and 121 mA·h·g^–1 after 100 and 500 cycles, respectively. Density functional theory calculations indicated the presence of covalent bonds between Li₄C₈H₂O₆ and graphene, which affected both the morphology and electronic structure of the composite. The special nanostructures, high electronic conductivity of graphene, and covalent-bond interaction between Li₄C₈H₂O₆ and graphene contributed to the superior electrochemical properties. Our results indicate that the combination of organic salt molecules with graphene is useful for obtaining high-performance organic batteries.

We report the synthesis and electrochemical sodium storage of cobalt disulfide (CoS₂) with various micro/nano-structures. CoS₂ with microscale sizes are either assembled by nanoparticles (P-CoS₂) via a facile solvothermal route or nanooctahedrons constructed solid (O-CoS₂) and hollow microstructures (H-CoS₂) fabricated by hydrothermal methods. Among three morphologies, H-CoS₂ exhibits the largest discharge capacities and best rate performance as anode of sodium-ion batteries (SIBs). Furthermore, H-CoS₂ delivers a capacity of 690 mA·h·g^-1 at 1 A·g^-1 after 100 cycles in a potential range of 0.1–3.0 V, and ~240 mA·h·g^-1 over 800 cycles in the potential window of 1.0–3.0 V. This cycling difference mainly lies in the two discharge plateaus observed in 0.1–3.0 V and one discharge plateau in 1.0–3.0 V. To interpret the reactions, X-ray diffraction (XRD) and transmission electron microscopy (TEM) are applied. The results show that at the first plateau around 1.4 V, the insertion reaction (CoS₂ + xNa⁺ + xe^- → Na_xCoS₂) occurs; while at the second plateau around 0.6 V, the conversion reaction (Na_xCoS₂ + (4 - x) Na⁺ + (4 - x)e^- → Co + 2Na₂S) takes place. This provides insights for electrochemical sodium storage of CoS₂ as the anode of SIBs.

An aerosol spray pyrolysis technique is used to synthesize a spherical nano-Sb@C composite. Instrumental analyses reveal that the micro-nanostructured composite with an optimized Sb content of 68.8 wt% is composed of ultra-small Sb nanoparticles (10 nm) uniformly embedded within a spherical porous C matrix (denoted as 10-Sb@C). The content and size of Sb can be controlled by altering the concentration of the precursor. As an anode material of sodium-ion batteries, 10-Sb@C provides a discharge capacity of 435 mAh·g^–1 in the second cycle and 385 mAh·g^–1 (a capacity retention of 88.5%) after 500 cycles at 100 mAh·g^–1. In particular, the electrode exhibits an excellent rate capability (355, 324, and 270 mAh·g^–1 at 1, 000, 2, 000, and 4, 000 mA·g^–1, respectively). Such a high-rate performance for the Sb-C anode has rarely been reported. The remarkable electrochemical behavior of 10-Sb@C is attributed to the synergetic effects of ultra-small Sb nanoparticles with an uniform distribution and a porous C framework, which can effectively alleviate the stress associated with a large volume change and suppress the agglomeration of the pulverized nanoparticles during prolonged charge-discharge cycling.

We report on the ice-templated preparation and sodium storage of ultrasmall SnO₂ nanoparticles (3-4 nm) embedded in three-dimensional (3D) graphene (SnO₂@3DG). SnO₂@3DG was fabricated by hydrothermal assembly with ice-templated 3DG and a tin source. The structure and morphology analyses showed that 3DG has an interconnected porous architecture with a large pore volume of 0.578 cm³·g^-1 and a high surface area of 470.5 m²·g^-1. In comparison, SnO₂@3DG exhibited a pore volume of 0.321 cm³·g^-1 and a surface area of 237.7 m²·g^-1 with a homogeneous distribution of ultrasmall SnO₂ nanoparticles in a 3DG network. SnO₂@3DG showed a discharge capacity of 1, 155 mA·h·g^-1 in the initial cycle, a reversible capacity of 432 mA·h·g^-1 after 200 cycles at 100 mA·g^-1 (with capacity retention of 85.7% relative to that in the second cycle), and a discharge capacity of 210 mA·h·g^-1 at a high rate of 800 mA·g^-1. This is due to the high distribution of SnO₂ nanoparticles in the 3DG network and the enhanced facilitation of electron/ion transport in the electrode.

Through in situ redox deposition and growth of MnO₂ nanostructures on hierarchically porous carbon (HPC), a MnO₂/HPC hybrid has been synthesized and employed as cathode catalyst for non-aqueous Li-O₂ batteries. Owing to the mild synthetic conditions, MnO₂ was uniformly distributed on the surface of the carbon support, without destroying the hierarchical porous nanostructure. As a result, the as-prepared MnO₂/HPC nanocomposite exhibits excellent Li-O₂ battery performance, including low charge overpotential, good rate capacity and long cycle stability up to 300 cycles with controlling capacity of 1, 000 mAh·g^-1. A combination of the multi-scale porous network of the shell-connected carbon support and the highly dispersed MnO₂ nanostructure benefits the transportation of ions, oxygen and electrons and contributes to the excellent electrode performance.

We report the preparation of porous CuO nanowires that are composed of nanoparticles (~50 nm) via a simple decomposition of a Cu(OH)₂ precursor and their application as the anode materials of rechargeable Na-ion batteries. The as-prepared porous CuO nanowires exhibit a Brunauer–Emmett–Teller (BET) surface area of 13.05 m²·g⁻¹, which is six times larger than that of bulk CuO (2.16 m²·g^–1). The anode of porous CuO nanowires showed discharge capacities of 640 mA·h·g^–1 in the first cycle and 303 mA·h·g^–1 after 50 cycles at 50 mA·g^–1. The high capacity is attributed to porous nanostructure which facilitates fast Na-intercalation kinetics. The mechanism of electrochemical Na-storage based on conversion reactions has been studied through cyclic voltammetry, X-ray diffraction (XRD), Raman spectroscopy, and high resolution transmission electron microscopy (HRTEM). It is demonstrated that in the discharge process, Na⁺ ions first insert into CuO to form a ${\mathrm{C}\mathrm{u}}_{1-x}^{Ⅱ}{\mathrm{C}\mathrm{u}}_x^{Ⅰ}{\mathrm{O}}_{1-x/2}$ solid and a Na₂O matrix then ${\mathrm{C}\mathrm{u}}_{1-x}^{Ⅱ}{\mathrm{C}\mathrm{u}}_x^{Ⅰ}{\mathrm{O}}_{1-x/2}$ reacts with Na⁺ to produce Cu₂O, and finally Cu₂O decompose into Cu nanoparticles enclosed in a Na₂O matrix. During the charge process, Cu nanoparticles are first oxidized to generate Cu₂O and then converted back to CuO. This result contributes to the design and mechanistic analysis of high-performance anodes for rechargeable Na-ion batteries.