Binder‐Induced Ultrathin SEI for Defect‐Passivated Hard Carbon Enables Highly Reversible Sodium‐Ion Storage

Abstract

Hard carbon is one of the most promosing anodes for resource‐rich sodium‐ion batteries. However, an unsatisfactory solid–electrolyte‐interphase formed by irreversible electrolyte consumption caused by defects or oxygen‐containing functional groups of hard carbon impedes its further application. Herein, a novel composite binder that is composed of polar polymer chondroitin sulfate A (sodium salt) and polyethylene oxide by hydrogen bonding demonstrates defect passivation capability. This composite binder can reduce the exposure of defects by forming hydrogen bonds with oxygen functional groups on the hard carbon surface and inhibit the decomposition of electrolyte confirmed by in situ differential electrochemical mass spectrometry. In situ Raman and theoretical calculations reveal that multiple polar functional groups in chondroitin sulfate A (sodium salt) can accelerate the transport of Na+ by adsorbing and facilitate the decomposition of PF6− to form NaF. Additionally, polyethylene oxide in the composite binder can increase viscosity and accelerate the transport of Na+. As a result, an ultra‐thin (9 nm, cyro‐TEM) and NaF‐rich solid–electrolyte interphase is obtained, thereby the hard carbon anode achieves improved initial Coulombic efficiency (84%) and high‐capacity retention of 94% after 150 cycles in a NaPF6/ethylene carbonate/dimethyl carbonate electrolyte.

Research prospects of graphene-based catalyst for seawater electrolysis

“…Usually, this structure is composed of two or more catalyst materials, which is connected together by physical or chemical bonds [97], Most graphene composites are generally connected by Van der Waals forces [98,99], including core-shell structure, although material stacking can lead to a significant increase in HER activity, and the use of electronic coupling when 2D materials are stacked with metal surfaces greatly reduces the contact resistance, thereby improving the electron transfer from metal surfaces to Van der Waals catalysis planar [99], but totally it is generally poor in terms of tunability, stability and corrosion resistance. More recently, heterostructures linked by covalent bonds whose vertical covalent linkages allow control of interlayer distances and their chemical properties will facilitate communication between 2D materials, while longer, sufficiently rigid and insulating molecules will have to help decouple materials; on the other hand, the additional leverage brought by the molecular interface will improve the intrinsic properties of the material [100][101][102], therefore, we believe that the heterostructure composed of graphene materials will have great application potential in catalyzing seawater.…”

Toward Highly Selective Heteroatom Dopants in Hard Carbon with Superior Lithium Storage Performance

“…Besides, a considerable amount of capacity at a low potential plateau ≤0.2 V vs Li + /Li makes them deliver high power density and fast charging performance . Nevertheless, the low Coulombic efficiency (CE) and the unstable solid–electrolyte interphase (SEI) on the HC anodes and voltage hysteresis hinder their practical applications . Enormous research studies have been devoted to enhance the performance of HC anodes.…”

“…8 the HC anodes and voltage hysteresis hinder their practical applications. 9 Enormous research studies have been devoted to enhance the performance of HC anodes. Heteroatoms are introduced into HCs through various methods, which have been accepted as feasible ways to enhance the Li storage performance.…”

Ultra-high initial coulombic efficiency of the TiO2 anode induced by the synergistic role of the electrolyte and binder for sodium-ion batteries

“…Furthermore, compared with the de/intercalation platform of TiO 2 in Li-ion batteries (1.2 V vs. Li/Li + ), the lower charge–discharge plateau (0.01 V vs. Na/Na + ) in sodium-ion batteries is easy to cause electrolyte decomposition and generate unstable electrolyte interfaces, which is extremely unfavorable for further improving the sodium storage performance of the TiO 2 anode, especially the initial coulombic efficiency (ICE) and cycle life. 7–12…”