Electrochemical properties of graphite electrode in propylene carbonate-based electrolytes containing lithium and calcium ions

Solvated Ion Intercalation in Graphite: Sodium and Beyond

Reversible intercalation of guest ions in graphite is the key feature utilized in modern battery technology. In particular, the capability of Li-ion insertion into graphite enabled the successful launch of commercial Li-ion batteries 30 years ago. On the road to explore graphite as a universal anode for post Li-ion batteries, the conventional intercalation chemistry is being revisited, and recent findings indicate that an alternative intercalation chemistry involving the insertion of solvated ions, designated as co-intercalation, could overcome some of the obstacles presented by the conventional intercalation of graphite. As an example, the intercalation of Na ions into graphite for Na-ion batteries has been perceived as being thermodynamically impossible; however, recent work has revealed that a large amount of Na ions can be reversibly inserted in graphite through solvated-Na-ion co-intercalation reactions. More recently, it has been extensively demonstrated that with appropriate electrolyte selection, not only Na ions but also other ions such as Li, K, Mg, and Ca ions can be co-intercalated into a graphite electrode, resulting in high capacities and power capabilities. The co-intercalation reaction shares a lot in common with the conventional intercalation chemistry but also differs in many respects, which has attracted tremendous research efforts in terms of both fundamentals and practical applications. Herein, we aim to review the progress made in understanding the solvated-ion intercalation mechanisms in graphite and to comprehensively summarize the state-of-the-art achievements by surveying the correlations among the guest ions, co-intercalation conditions, and electrochemical performance of batteries. In addition, the advantages and challenges related to the practical application of graphite undergoing co-intercalation reactions are presented.

A quasi-solid composite electrolyte with dual salts for dendrite-free lithium metal batteries

The cycle stability of the Li|HSE|Li battery can be greatly improved by adding magnesium salt to the electrolyte membrane.

In situ Raman investigation of electrolyte solutions in the vicinity of graphite negative electrodes

An unusual electrolyte solution structure change when in the vicinity of a graphite composite electrode was detected using in situ Raman spectroscopy.

N-Methylacetamide as an electrolyte component for suppressing co-intercalation of propylene carbonate in lithium ion batteries

N-Methylacetamide as an electrolyte component can suppress co-intercalation of propylene carbonate through competitive solvation and film-formation in Li-ion batteries.

Characterisation of the solid electrolyte interface during lithiation/delithiation of germanium in an ionic liquid

The characterisation of the SEI layer revealed that LiTFSI–[Py_1,4] is a relatively good ionic liquid based electrolyte for lithium batteries. However modifications in the electrolyte or a different anion might be necessary to improve the stability and composition of the SEI layer.

The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes

Despite the potential advantages it brings, such as wider liquid range and lower cost, propylene carbonate (PC) is seldom used in lithium-ion batteries because of its sustained cointercalation into the graphene structure and the eventual graphite exfoliation. Here, we report that cesium cation (Cs(+)) directs the formation of solid electrolyte interphase on graphite anode in PC-rich electrolytes through its preferential solvation by ethylene carbonate (EC) and the subsequent higher reduction potential of the complex cation. Effective suppression of PC-decomposition and graphite-exfoliation is achieved by adjusting the EC/PC ratio in electrolytes to allow a reductive decomposition of Cs(+)-(EC)m (1 ≤ m ≤ 2) complex preceding that of Li(+)-(PC)n (3 ≤ n ≤ 5). Such Cs(+)-directed interphase is stable, ultrathin, and compact, leading to significant improvement in battery performances. In a broader context, the accurate tailoring of interphasial chemistry by introducing a new solvation center represents a fundamental breakthrough in manipulating interfacial reactions that once were elusive to control.