Sulfide-based all-solid-state lithium-ion batteries (ASSLIBs) are promising candidates in the next generation of energy storage technology; the voltage mismatch and the resulting side reactions at the interface between the cathode and the solid electrolyte, however, dramatically deteriorate their cycling performance. Herein, for the first time, we report that the chemical interaction between LiCoO₂ (LCO) and TiO₂ can be regulated by two additives, carbon and Li₂CO₃, which in situ form a continuous ultrathin pure-phase Li₂CoTi₃O₈ (LCTO) layer with a stable 3D network of spinel structures, relatively low electronic conductivity (2.5 × 10⁻⁸ S cm⁻¹) and high lithium diffusion coefficient (D_Li⁺ = 8.22 × 10⁻⁷ cm² s⁻¹) on the surface of LCO. When assembled in ASSLIBs, such an LCTO layer functions as an interlayer between the LCO and the Li₁₀GeP₂S₁₂ solid electrolyte (LGPS). As a consequence, the original interface LCO/LGPS is substituted by two new interfaces LCO/LCTO and LCTO/LGPS. DFT calculations indicate that, compared with the LCO/LGPS, the new interfaces are not only thermodynamically and electrochemically more compatible, but also have higher interfacial affinity. Therefore, the relevant ASSLIB exhibits evidently reduced interfacial impedance, and it also displays a high initial capacity of 140 mA h g⁻¹ and a reversible discharge specific capacity of 116 mA h g⁻¹ after 200 cycles at room temperature (0.1C). In comparison, the ASSLIB assembled without the LCTO interlayer delivers an initial capacity of 98 mA h g⁻¹ and only retains 22.4% capacity after 100 cycles (0.1C). Even at a high cutoff voltage (4.5 V vs. Li/Li⁺), the ASSLIB with the LCTO interlayer could also exhibit a high initial capacity of 180 mA h g⁻¹ and a remarkable retention of 132 mA h g⁻¹ after 100 cycles.

Carbon nanotubes (CNTs) have many excellent properties that make them ideally suited for use in lithium‐ion batteries (LIBs). In this review, the recent research on applications of CNTs in LIBs, including their usage as freestanding anodes, conductive additives, and current collectors, are discussed. Challenges, strategies, and progress are analyzed by selecting typical examples. Particularly, when CNTs are used with relatively large mass fractions, the relevant interfacial electrochemistry in such a CNT‐based electrode, which dictates the quality of the resulting solid–electrolyte interface, becomes a concern. Hence, in this review the different lithium‐ion adsorption and insertion mechanisms inside and outside of CNTs are compared; the influence of not only CNT structural features (including their length, defect density, diameter, and wall thickness) but also the electrolyte composition on the solid–electrolyte interfacial reactions is analyzed in detail. Strategies to optimize the solid–solid interface between CNTs and the other solid components in various composite electrodes are also covered. By emphasizing the importance of such a structure–performance relationship, the merits and weaknesses of various applications of CNTs in various advanced LIBs are clarified.