All-solid-state lithium metal batteries (ASSLMBs) that incorporate solid electrolyte (SE) and lithium metal anode suggest considerable potential in addressing the security concerns and energy density limitation of conventional lithium-ion batteries (LIBs). However, the practical application of ASSLMBs is always restricted by the interfacial instability of lithium metal anode/electrolyte and inevitable lithium dendrites propagation in SE. Herein, a solvate ionic liquid is adopted to modify the interface stability of lithium metal anode/electrolyte and inhibit the growth of lithium dendrites via an in-situ formation of a robust solid electrolyte interphase (SEI) on the surface of lithium metal anode. Consequently, the ASSLMBs assembled with Li₆PS₅Cl (LPSCl) electrolyte, lithium metal anode that protected by robust SEI layer, and LiNbO₃@NCM622 cathode exhibit high initial capacity of 126.5 mAh·g⁻¹ and improved cycling stability with a capacity retention of 80.3% over 60 cycles at 0.1 C. This work helps to provide a facile route for the design of robust SEI in the application of ASSLMBs.

The massive application of single crystal (SC) ternary cathode material LiNi_1-x-yMn_xCoO₂ is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li⁺ diffusion and structural instability. Herein, Pr³⁺, a large radius ion is introduced to single-crystal LiNi_0.5Mn_0.3Co_0.2O₂ to enhance Li ⁺ conductivity and structural stability. With 0.4% Pr doping, the Li(Ni_0.5Mn_0.3Co_0.2)_0.996Pr_0.004O₂ cathode displays a capacity retention of 79.72% at 10 C, and a 98.17% capacity retention after 50 cycles at 25 ℃ and 96.3% capacity retention after 50 cycles at 55 ℃ within a 3.0–4.5 V voltage window. Electrochemical impedance spectroscopy confirms that the Pr doping can effectively lower the charge-transfer resistance and facilitate the transportation of Li⁺ on the surface of LiNi_0.5Mn_0.3Co_0.2O₂. The Direct current internal resistance result implies that the structure of the Pr-doped cathode particles is more stable during cycling. In addition, differential scanning calorimetry measurements measurement combined with in situ X-ray diffraction confirms the thermo-stabilization effect of the Pr dopant.

Due to the high reactivity between the lithium metal and traditional organic liquid electrolyte, the reaction of lithium metal electrode is usually uneven and there are also unexpected side reactions. Therefore, construction of a stable solid electrolyte interface (SEI) is highly essential to improve the performance of lithium metal anode. Herein, a sandwich-like gel polymer electrolyte (GPE) is accurately prepared by in-situ polymerization of Polyacrylonitrile (PAN) nanofiber membrane with trihydroxymethylpropyl trimethylacrylate (TMPTMA) and 1, 6-hexanediol diacrylate (HDDA). The resulting GPE with a tightly cross-linked gel skeleton exhibits high ionic conductivity and electrochemical window of 5.6 V versus Li/Li⁺. In particular, the pretreatment of Li metal anode can improve the interfacial wettability, and the synergy of the chemically pretreated Li metal anode surface and the GPE can electrochemically in situ generate SEI with compositionally stable and fluorine-rich inorganic components. Owing to these unique advantages, the interfacial compatibility between the GPE and lithium metal is greatly improved. Meanwhile, the formed SEI can inhibit the formation of lithium dendrites, and decomposition of GPE would be alleviated. The assembled Li-FEC|GPE|LiFePO₄ full cell shows a high initial discharge capacity of 157.1 mA h g⁻¹, and maintains a capacity retention of 92.3% after 100 cycles at 0.2C.

In practical pouch cell, LiNi_0.5Mn_0.3Co_0.2O₂/artificial graphite lithium ion battery using single-crystal LiNi_0.5Mn_0.3Co_0.2O₂ (S-NMC532) as cathode can have excellent cycle performance. However, single-crystal LiNi_0.5Mn_0.3Co_0.2O₂ inevitably suffers poor rate capability compared to the polycrystalline materials. Here, we systematically studied the relationship between microstructural characteristics and the practical rate performance, as well as explored the impedance change during the cycling process in the pouch cell. This work shows that the (001) plane microtexture of the electrode surface structure is a critical barrier for rate capability. Electron backscatter diffraction (EBSD), electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) are conducted on the cathodes. These analyses allow to conclude on the influence of the (001) plane microtexture on the electrode surface, which illustrates a diffusion resistance of lithium ions, and then, leading a high interfacial resistance. Thus, this work confirms the main cause of the inferior rate capability of S-NMC532 and offers guidance for developing a battery with high rate and ultralong cycling life.

The development of dual-function anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) is exceedingly essential. Herein, with rationally designed hierarchical metal-organic framework (MOF)@MXene as a precursor, a novel sandwich-like CoP-NC@Ti₃C₂T_x composite has been successfully fabricated by the following phosphorization reaction. As anode material for LIBs, the CoP-NC@Ti₃C₂T_x composite exhibits remarkable electrochemical performance with high-rate capability (147.8 mAh g⁻¹ at 2000 mA g⁻¹; 245.6 mAh g⁻¹ at 100 mA g⁻¹) and ultralong cycling life (2000 cycles with a capacity retention over 100%). For SIBs, it delivers a discharge capacity of 101.6 mAh g⁻¹ at a current density of 500 mA g⁻¹ after 500 cycles. The well-designed sandwich-like composite effectively supports the easy access to electrolyte, facilitate the Li/Na ion transportation, and protect the active material from pulverization upon long cycling. In addition, the electrochemical reaction kinetics and Li-migration kinetics of the CoP-NC@Ti₃C₂T_x composite have been pioneeringly illuminated by pseudocapacitive behavior calculation and density functional theory (DFT) computations, respectively. This work sheds light on the rational design and development of MOF/MXene-derived dual-function anode materials for Li/Na-storage.

Ultrasmall γ-Fe₂O₃ nanodots (~ 3.4 nm) were homogeneously encapsulated in interlinked porous N-doped carbon nanofibers (labeled as Fe₂O₃@C) at a considerable loading (~ 51 wt.%) via an electrospinning technique. Moreover, the size and content of Fe₂O₃ could be controlled by adjusting the synthesis conditions. The obtained Fe₂O₃@C that functioned as a self-standing membrane was used directly as a binder- and current collector-free anode for sodium-ion batteries, displaying fascinating electrochemical performance in terms of the exceptional rate capability (529 mA·h·g^-1 at 100 mA·g^-1 compared with 215 mA·h·g^-1 at 10, 000 mA·g^-1) and unprecedented cyclic stability (98.3% capacity retention over 1, 000 cycles). Furthermore, the Na-ion full cell constructed with the Fe₂O₃@C anode and a P2-Na_2/3Ni_1/3Mn_2/3O₂ cathode also exhibited notable durability with 97.2% capacity retention after 300 cycles. This outstanding performance is attributed to the distinctive three-dimensional network structure of the very-fine Fe₂O₃ nanoparticles uniformly embedded in the interconnected porous N-doped carbon nanofibers that effectively facilitated electronic/ionic transport and prevented active materials pulverization/aggregation caused by volume change upon prolonged cycling. The simple and scalable preparation route, as well as the excellent electrochemical performance, endows the Fe₂O₃@C nanofibers with great prospects as high-rate and long-life Na-storage anode materials.