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.

All-solid-state lithium-ion batteries (ASSLIBs) are considered the most promising option for next-generation high-energy and safe batteries. Herein, a practical all-solid-state battery, with a Li- and Mn-rich layered oxide (LMRO) as the cathode and Li6PS5Cl as the electrolyte, is demonstrated for the first time. The battery delivers the most exceptional performance by far in terms of ultrahigh capacity of 244.5 mA h g–1 and unprecedented cycling stability with an 83% capacity retention after 1000 cycles. We discover that the Li6PS5Cl can be reversibly oxidized and reduced within the voltage range 2.0–4.8 V, which is beneficial to the ionic conduction during long-term cycling of ASSLIBs. Moreover, the electronic and ionic conductivities of LMROs are increased by 4 orders of magnitude via precisely tailoring the composition and structure. In addition, the typical dissolution of transition metal, oxygen release, and phase transformation of LMROs in liquid batteries are substantially eliminated in ASSLIBs.

A Li[Li0.2Ni0.13Co0.13Mn0.54]O2–xLiNiO2 composite cathode with a Ni-rich bulk phase and in situ precipitated Ni-rich spinel-like surface phase has been built to enhance the initial voltage and suppress voltage fading during cycling.