ABSTRACT
The modulation of the characteristics of an MoS2 anode via substitutional doping, particularly N, P and Se, is vital for promoting the potassium-ion storage performances. However, these traditional chalcogen doping can only take the place of a sulfur element and not essentially change the inherent electrical nature of MoS2. Herein, novel Te-MoS2 materials have been synthesized via a simple hydrothermal process under Te doping. A half-metallic Te occupies the position of an Mo atom to form Te-S bonds, which is different from the same group Se element. After theoretical modeling and electrochemical measurements, it was observed that the formation of Te-S bonds can increase the electrical conductivity (about 530 times increment) and mitigate the mechanical stress to ensure the whole structural stability during the repeated insertion/extraction of K-ions. Moreover, the insertion of Te into the lattice of MoS2 generated the fractional phase transformation from 2H to the 1T phase of MoS2 and 1T&2H in-plane hetero-junction. Benefiting from these advantages, the 1T&2H Te-MoS2 anode delivered high capacities of 718 and 342 mA h g-1 at 50 and 5000 mA g-1, respectively, and an ultra-stable cycling performance (88.1% capacity retention after 1000 cycles at 2 A g-1). Moreover, the potassium-ion full cell assembled with K2Fe[Fe(CN)6] as the cathode demonstrates its practical application.
ABSTRACT
The space charge layer (SCL) is generally considered one of the origins of the sluggish interfacial lithium-ion transport in all-solid-state lithium-ion batteries (ASSLIBs). However, in-situ visualization of the SCL effect on the interfacial lithium-ion transport in sulfide-based ASSLIBs is still a great challenge. Here, we directly observe the electrode/electrolyte interface lithium-ion accumulation resulting from the SCL by investigating the net-charge-density distribution across the high-voltage LiCoO2/argyrodite Li6PS5Cl interface using the in-situ differential phase contrast scanning transmission electron microscopy (DPC-STEM) technique. Moreover, we further demonstrate a built-in electric field and chemical potential coupling strategy to reduce the SCL formation and boost lithium-ion transport across the electrode/electrolyte interface by the in-situ DPC-STEM technique and finite element method simulations. Our findings will strikingly advance the fundamental scientific understanding of the SCL mechanism in ASSLIBs and shed light on rational electrode/electrolyte interface design for high-rate performance ASSLIBs.
ABSTRACT
Herein, the definite structure-dependent evolution process upon lithiation/delithiation and clear atomic images of pure 1T-phase SnS2 were obtained for the first time, illustrating the different insertion-conversion-desertion processes of discharge/charge plateaus. Also, 1T SnS2 exhibited advantages over commercial SnS2 (mixed with 1T and 1H phases) in cell resistance and lithium-storage performance.
