Across Interfacial Li+ Conduction Accelerated by a Single-Ion Conducting Polymer in Ceramic-Rich Composite Electrolytes for Solid-State Batteries.

Composite electrolytes have been accepted as the most promising species for solid-state batteries, exhibiting the synergistic advantages of solid polymer electrolytes (SPEs) and solid ceramic electrolytes (SCEs). Unfortunately, the interrupted Li+ conduction across the SPE and SCE interface hinders the ionic conductivity improvement of composite electrolytes. In our study on a ceramic-rich composite electrolyte (CRCE) membrane composed of borate polyanion-based lithiated poly(vinyl formal) (LiPVFM) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) particles, it is found that the strong interaction between the polyanions in LiPVFM and LATP particles results in a uniform distribution of ceramic particles at a high proportion of 50 wt % and good robustness of the electrolyte membrane with a Young's modulus of 9.20 GPa. More importantly, ab initio molecular dynamics simulation and experimental results demonstrate that Li+ conduction across the SPE and SCE interface is induced by the polyanion-based polymer due to its high lithium-ion transference number and similar Li+ diffusion coefficient with the SCE. Therefore, the unblocked Li+ conduction among ceramic particles dominates in the CRCE membrane with a high ionic conductivity of 6.60 × 10-4 S cm-1 at 25 °C, a lithium-ion transference number of 0.84, and a wide electrochemical stable window of 5.0 V (vs Li/Li+). Consequently, the high nickel ternary cathode LiNi0.8Mn0.1Co0.1O2-based batteries with CRCE deliver a high-rate capability of 135.08 mAh g-1 at 1.0 C and a prolonged cycle life of 100 cycles at 0.2 C between 3.0 and 4.3 V. The polyanion-induced Li+ conduction across the interface sheds new light on solving composite electrolyte problems for solid-state batteries.

Sulfide with Oxygen-Rich Carbon Network for Good Lithium-Storage Kinetics.

Transition metal sulfides are of great interest as electrode material for alkali metal-ion batteries due to their high theoretical capacity. However, sluggish ion migration and electron transfer kinetics lead to poor cycling stability and rate performance, which hinders their practical applications. Herein, we develop a two-step localized carbonization and sulfurization method to construct a CoS2 composite material (CoS2@CNTs@C) from an in situ integrated zeolitic imidazolate framework (ZIF-67) and multiwalled carbon nanotube precursor (ZIF-67@CNTs). The as-prepared CoS2@CNTs@C composites with a nanoscale carbon skeleton inherit a large specific surface area and suitable nanopore size distribution from ZIF-67 and incredibly abundant oxygenated functional groups from CNTs. The theoretical calculation and material characterization demonstrate that the oxygenated functional groups on the porous carbon networks accelerate lithium-ion diffusion and electron transfer and especially electrocatalyze the progressive conversion of Li2S6 to the final product Li2S. Meanwhile, the three-dimensional conductive network guarantees the conductive and structural stability of CoS2@CNTs@C during the repeated lithium-storage process. Therefore, the CoS2@CNTs@C electrode material can deliver an initial discharge capacity of 1282.3 mA h g-1 at 200 mA g-1 with a high Coulombic efficiency of 93.5% and a reversible capacity of 558.8 mA h g-1 at 2000 mA g-1 in 600 cycles with a high capacity retention of 96.1%.