Ruizhuo Zhang

All-solid-state lithium-sulfur batteries promise high specific energy and low cost. However, they are challenged by poor rate capability and cycling stability owing to the slow solid-solid sulfur redox reactions. Here, we present fast-charging and durable all-solid-state lithium-sulfur batteries enabled by a pre-embedded solid-solid redox mediator using an amorphous sulfur/iodine nano-eutectic positive electrode. The iodine, intimately homogenized with sulfur owing to carbon mesopore encapsulation, undergoes rapid I₂/I⁻ redox reaction, mediating solid-solid sulfur reactions by promoting electron transfer across the boundaries. The iodine within the carbon and on its surface reacts in situ with the sulfide catholyte to form a globally distributed I₂/I⁻ nano-network throughout the positive electrode, thereby enabling fast charging. The cell exhibits a specific capacity of 851.9 mA h g⁻¹_S/I when charged at 10 C, and 474.7 mA h g⁻¹_S/I at a charging rate of 24 C (1 C is defined as 945 mA g⁻¹_S/I). The high reversibility of the redox-mediated reaction enables durable cycling for 9,000 cycles over 9 months at 2 C and 2,800 cycles over 17 months at 0.5 C. This strategy represents a perspective for developing solid-state conversion electrodes that are plagued by sluggish reactions.

Solid-state batteries (SSBs) are primarily tested in two-electrode and/or symmetric cell configurations, which may lead to under- or overestimation of degradation and failure. For long-term cycling and under dynamic conditions, the contribution of the counter electrode (anode) to fading may be substantial but is rarely reported due to lack of suitable characterization techniques. Here, we employed an advanced three-electrode cell setup to elucidate the overpotential growth and interface-related kinetic response for commonly used counter electrodes in lab-scale testing, namely, Li₄Ti₅O₁₂ and In/InLi, as well as for LiNbO₃-coated LiNi_0.85Co_0.10Mn_0.05O₂ as the working electrode (cathode) in thiophosphate-based SSB cells. This was achieved through continuous monitoring of individual electrode potentials (>1500 h) and by performing electrochemical impedance spectroscopy measurements in situ in combination with distribution of relaxation times analysis. The results reveal distinct differences in polarization and interfacial kinetics between the Li₄Ti₅O₁₂ and In/InLi anodes in practical application scenarios and how these affect cyclability and the analysis of capacity fading.

With promises for high specific energy, high safety and low cost, the all-solid-state lithium–sulfur battery (ASSLSB) is ideal for next-generation energy storage^1,2,3,4,5. However, the poor rate performance and short cycle life caused by the sluggish solid–solid sulfur redox reaction (SSSRR) at the three-phase boundaries remain to be solved. Here we demonstrate a fast SSSRR enabled by lithium thioborophosphate iodide (LBPSI) glass-phase solid electrolytes (GSEs). On the basis of the reversible redox between I⁻ and I₂/I₃⁻, the solid electrolyte (SE)—as well as serving as a superionic conductor—functions as a surficial redox mediator that facilitates the sluggish reactions at the solid–solid two-phase boundaries, thereby substantially increasing the density of active sites. Through this mechanism, the ASSLSB exhibits ultrafast charging capability, showing a high specific capacity of 1,497 mAh g⁻¹_sulfur on charging at 2C (30 °C), while still maintaining 784 mAh g⁻¹_sulfur at 20C. Notably, a specific capacity of 432 mAh g⁻¹_sulfur is achieved on charging at an extreme rate of 150C at 60 °C. Furthermore, the cell demonstrates superior cycling stability over 25,000 cycles with 80.2% capacity retention at 5C (25 °C). We expect that our work on redox-mediated SSSRR will pave the way for developing advanced ASSLSBs that are high energy and safe.

Lithium nickel oxide (LNO) is a promising cathode candidate in various next‐generation battery technologies. To increase its stability, doping and surface coating have become key strategies. Among various elements, niobium stands out for its dual role as an effective dopant and the advantages of its oxide phases as coatings. In this study, we explore Nb‐based coating of LNO, utilizing methods that minimize or eliminate solvent use. Additionally, the coated samples were treated at two different temperatures to study their effect on properties and electrochemical performance. Our results demonstrate that the coating process strongly affects the cell cyclability and further highlight the potential of Nb‐based protective coatings in enhancing LNO as a cathode active material for application in high‐energy‐density Li‐ion batteries.

The interlaboratory comparability and reproducibility of all-solid-state battery cell cycling performance are poorly understood due to the lack of standardized set-ups and assembly parameters. This study quantifies the extent of this variability by providing commercially sourced battery materials—LiNi_0.6Mn_0.2Co_0.2O₂ for the positive electrode, Li₆PS₅Cl as the solid electrolyte and indium for the negative electrode—to 21 research groups. Each group was asked to use their own cell assembly protocol but follow a specific electrochemical protocol. The results show large variability in assembly and electrochemical performance, including differences in processing pressures, pressing durations and In-to-Li ratios. Despite this, an initial open circuit voltage of 2.5 and 2.7 V vs Li⁺/Li is a good predictor of successful cycling for cells using these electroactive materials. We suggest a set of parameters for reporting all-solid-state battery cycling results and advocate for reporting data in triplicate.

Thermal decomposition of overlithiated Li _{1+ x} Ni _{1− x} O ₂ yields high-quality LiNiO ₂ cathode materials that show potential for application in different kinds of batteries.

Ni‐rich LiNi_xCo_yMn_zO₂ cathode materials offer high practical capacities and good rate capability, but are notorious for being unstable at high state of charge. Here, a series of such layered oxides with nickel contents ranging from 88 to 100 mol% is fabricated by sodium‐to‐lithium ion exchange, yielding materials devoid of substitutional defects. Examining the initial charge/discharge cycle reveals effects that are specifically caused by transition‐metal substitution, which would otherwise be obscured by changes in lithium‐site defect concentration. Lowering the nickel content helps to stabilize the high‐voltage regime, while simultaneously negatively affecting lithium diffusion. Operando X‐ray diffraction indicates mitigation of volume variation during cycling and transition toward solid‐solution behavior with sufficiently high cobalt and manganese contents, thus providing an explanation for the increased stability. The interplay between transition‐metal substitution, kinetic hindrance, and solid‐solution behavior may be a result of local inhomogeneities due to lithium‐vacancy pinning, which is further elucidated through density functional theory calculations. Overall, this work sheds new light on the effects of manganese and cobalt incorporation into the transition‐metal layer and their conjunction with defects.