Halide solid electrolytes have been considered as the most promising candidates for practical high-voltage all-solidstate lithium-ion batteries (ASSLIBs) due to their moderate ionic conductivity and good interfacial compatibility with oxide cathode materials. Aliovalent ion doping is an effective strategy to increase the ionic conductivity of halide electrolytes. However, the effects of ion doping on the electrochemical stability window of halide electrolytes and carbon additive on electrochemical performance are still unclear by far. Herein, a series of Zr-doped Li 3−x Er 1−x Zr x Cl 6 halide solid electrolytes (SEs) are synthesized through a mechanochemical method and the effects of Zr substitution on the ionic conductivity and electrochemical stability window are systematically investigated. Zr doping can increase the ionic conductivity, whereas it narrows the electrochemical stability window of the Li 3 ErCl 6 electrolyte simultaneously. The optimized Li 2.6 Er 0.6 Zr 0.4 Cl 6 electrolyte exhibits both a high ionic conductivity of 1.13 mS cm −1 and a high oxidation voltage of 4.21 V. Furthermore, carbon additives are demonstrated to be beneficial for achieving high discharge capacity and better cycling stability and rate performance for halide-based ASSLIBs, which are completely different from the case of sulfide electrolytes. ASSLIBs with uncoated LiCoO 2 cathode and carbon additives exhibit a high discharge capacity of 147.5 mAh g −1 and superior cycling stability with a capacity retention of 77% after 500 cycles. This work provides an in-depth understanding of the influence of ion doping and carbon additives on halide solid electrolytes and feasible strategies to realize highenergy-density ASSLIBs.

Scheme 1. Illustration of the synthesis process of the TiNb 2 O 7 nanoflakes and the TiNb 2 O 7 -incorporated MgH 2 system.

Li‐rich Mn‐based layered oxides (LMLOs) are promising cathode material candidate for the next‐generation Li‐ion batteries (LIBs) of high energy density. However, the fast capacity fading and voltage decay as well as low Coulombic efficiency caused by irreversible oxygen release and phase transition during the electrochemical process hinder their practical application. To solve these problems, in the present study, a multifunctional surface construction involving a coating layer, spinel‐layered heterostructure, and rich‐in oxygen vacancies is successfully conducted by a facile thermal reduction of the LMLO particles with potassium borohydride (KBH4) as the reducing agent. The multifunctional surface structure plays synergistic effects on suppressing the interface side reaction, reducing the dissolution of transition metal, increasing electron conductivity and lithium diffusion rate. As a result, electrochemical performances of the LMLO cathode are effectively enhanced. With optimization of the addition of KBH4, the electrode delivers a reversible capacity of 280 mAh g−1 at 0.1 C, which maintains after 100 cycles. The capacity retention with respect to the initial capacity is as high as 98% at 1 C after 400 cycles. The present work provides insights into designing a highly effective functional surface structure of LMLO cathode materials for high‐performance LIBs.

Lithium-ion batteries (LIBs) have gained unprecedented importance in the fields of portable electronic devices, electric vehi-

Intermetallic Pd3Pb ultrathin nanoplate-constructed flowers were synthesized and exhibited substantially enhanced properties for the oxygen reduction reaction relative to commercial Pt/C.