The development of sodium-ion batteries for large-scale applications requires the synthesis of electrode materials with high capacity, high initial Coulombic efficiency (ICE), high rate performance, long cycle life, and low cost. A rational design of freestanding anode materials is reported for sodium-ion batteries, consisting of molybdenum disulfide (MoS2) nanosheets aligned vertically on carbon paper derived from paper towel. The hierarchical structure enables sufficient electrode/electrolyte interaction and fast electron transportation. Meanwhile, the unique architecture can minimize the excessive interface between carbon and electrolyte, enabling high ICE. The as-prepared MoS2@carbon paper composites as freestanding electrodes for sodium-ion batteries can liberate the traditional electrode manufacturing procedure, thereby reducing the cost of sodium-ion batteries. The freestanding MoS2@carbon paper electrode exhibits a high reversible capacity, high ICE, good cycling performance, and excellent rate capability. By exploiting in situ Raman spectroscopy, the reversibility of the phase transition from 2H-MoS2 to 1T-MoS2 is observed during the sodium-ion intercalation/deintercalation process. This work is expected to inspire the development of advanced electrode materials for high-performance sodium-ion batteries.

MoS2 Nanosheets Vertically Aligned on Carbon Paper: A Freestanding Electrode for Highly Reversible Sodium Ion Batteries

Surface/Interface Structure Degradation of Ni-Rich Layered Oxide Cathodes toward Lithium-Ion Batteries: Fundamental Mechanisms and Remedying Strategies

Challenges and Strategies to Advance High-Energy Nickel-Rich Layered Lithium Transition Metal Oxide Cathodes for Harsh Operation

Tungsten doping for stabilization of Li[Ni0.90Co0.05Mn0.05]O2 cathode for Li-ion battery at high voltage

Improvement of electrochemical reversibility of the Ni-Rich cathode material by gallium doping

The vital challenge in relation to layered Ni-rich cathodes is their pronounced structural degradation originating from cation mixing at high voltage, which causes serious electrode polarization and electrochemical deterioration. Herein, an overall structural modification strategy, which integrates a Li2GeO3 coating with gradient Ge-doping, was developed to improve the structural stability and create ordered diffusion channels in a layered Ni-rich cathode via interfacial fusion at high temperature. This effective strategy significantly enhances the reversible capacity retention, voltage stability and rate capability of the layered Ni-rich cathode at high voltage. We find that the Li2GeO3 coating inhibits interfacial side reactions to enhance the surface structural stability of the cathode materials. More importantly, the gradient Ge-doping plays a critical role in suppressing cation mixing to improve the ordered channels available for Li+ ion transport. The experimental observations, corroborated by first principle calculations, further reveal that Ge-doping not only alleviates structural degradation by increasing the phase transition energy barrier for layers to form spinel-like or rock-salt phases, but also facilitates fast Li+ diffusion kinetics via reducing the diffusion barrier. Our work provides a design idea for stabilizing the surface/bulk structure of advanced cathodes for high-performance Li-ion batteries.

Overall structural modification of a layered Ni-rich cathode for enhanced cycling stability and rate capability at high voltage

Tulip-like MoS2 with a tapered structure was assembled using a single-sheet anchored on N-doped graphene substrates (tulip-MoS2/NG) through an in situ technique with N-methyl-2-pyrrolidinone (NMP) as the “sacrificial agent” to promote C–O–Mo bond formation. As an anode for the Na+ battery, tulip-MoS2/NG electrodes exhibited excellent capacity retention (above 99% after 100 cycles at 0.1 A g−1) and long cycling stability (179 mA h g−1 at 1 A g−1 and 151 mA h g−1 at 5 A g−1 after 1000 cycles with a degradation below 110 μAh g−1 cycle−1). The excellent electrochemical performance could be attributed to the single-sheet tapered structure that functions as a self-support and promotes the stability of the tulip-MoS2/NG architecture. Moreover, the C–O–Mo bonds derived from the NMP molecular bridge fixed tulip-like MoS2 on the NG.

Xing Wang

Papers

Overall structural modification of a layered Ni-rich cathode for enhanced cycling stability and rate capability at high voltage

Tulip-like MoS2 with a single sheet tapered structure anchored on N-doped graphene substrates via C–O–Mo bonds for superior sodium storage