Wenlong Cai

The performance of Li-ion batteries (LIBs) is highly dependent on their interfacial chemistry, which is regulated by electrolytes. Conventional electrolyte typically contains polar solvents to dissociate Li salts. Herein we report a weakly solvating electrolyte (WSE) that consists of a pure non-polar solvent, which leads to a peculiar solvation structure where ion pairs and aggregates prevail under a low salt concentration of 1.0 M. Importantly, WSE forms unique anion-derived interphases on graphite electrodes that exhibit fast-charging and long-term cycling characteristics. First-principles calculations unravel a general principle that the competitive coordination between anions and solvents to Li ions is the origin of different interfacial chemistries. By bridging the gap between solution thermodynamics and interfacial chemistry in batteries, this work opens a brand-new way towards precise electrolyte engineering for energy storage devices with desired properties.

With the impetus to accelerate worldwide market adoption of electrical vehicles and afford consumer electronics with better user experience, advancing fast-charging technology is an inevitable trend. However, current high-energy lithium-ion batteries are unable to support ultrafast power input without any adverse consequences, with the capacity fade and safety concerns of the mainstream graphite-based anodes being the key technological barrier. The aim of this review is to summarise the fundamentals, challenges, and solutions to enable graphite anodes that are capable of high-rate charging. First, we explore the complicated yet intriguing graphite-electrolyte interface during intercalation based on existing theories. Second, we analyse the key dilemmas facing fast-charging graphite anodes. Finally, some promising strategies proposed during the past few years are highlighted so as to outline current trends and future perspectives in this field.

Abstract Lithium‐ion batteries with routine carbonate electrolytes cannot exhibit satisfactory fast‐charging performance and lithium plating is widely observed at low temperatures. Herein we demonstrate that a localized high‐concentration electrolyte consisting of 1.5 M lithium bis(fluorosulfonyl)imide in dimethoxyethane with bis(2,2,2‐trifluoroethyl) ether as the diluent, enables fast‐charging of working batteries. A uniform and robust solid electrolyte interphase (SEI) can be achieved on graphite surface through the preferential decomposition of anions. The established SEI can significantly inhibit ether solvent co‐intercalation into graphite and achieve highly reversible Li + intercalation/de‐intercalation. The graphite | Li cells exhibit fast‐charging potential (340 mAh g −1 at 0.2 C and 220 mAh g −1 at 4 C), excellent cycling stability (ca. 85.5 % initial capacity retention for 200 cycles at 4 C), and impressive low‐temperature performance.

Abstract The lithium–sulfur (Li–S) battery is regarded as a next‐generation energy storage system due to its conspicuous merits in high theoretical capacity (1672 mAh g −1 ), overwhelming energy density (2600 Wh kg −1 ), and the cost‐effectiveness of sulfur. However, the practical application of Li–S batteries is still handicapped by a multitude of key challenges, mainly pertaining to fatal lithium polysulfide (LiPS) shuttling and sluggish sulfur redox kinetics. In this respect, rationalizing electrocatalytic processes in Li–S chemistry to synergize the entrapment and conversion of LiPSs is of paramount significance. This review summarizes recent progress and well‐developed strategies of the mediator design toward promoted Li–S chemistry. The current advances, existing challenges, and future directions are accordingly highlighted, aiming at providing in‐depth understanding of the sulfur reaction mechanism and guiding the rational mediator design to realize high‐energy and long‐life Li–S batteries.