Low-Concentrated Lithium Hexafluorophosphate Ternary-based Electrolyte for a Reliable and Safe NMC/Graphite Lithium-Ion Battery

An Ultralow-concentration and Moisture-resistant Electrolyte of Lithium Difluoro(oxalato)borate in Carbonate Solvents for Stable Cycling in Practical Lithium-ion Batteries

The electrolyte concentration not only impacts the battery performance but also affects the battery cost and manufacturing. Currently, most studies focus on high-concentration (>3 M) or localized high-concentration electrolytes (~1 M); however, the expensive lithium salt imposes a major concern. Most recently, ultralow concentration electrolytes (<0.3 M) have emerged as intriguing alternatives for battery applications, which feature low cost, low viscosity, and extreme-temperature operation. However, at such an early development stage, many works are urgently needed to further understand the electrolyte properties. Herein, we introduce an ultralow concentration electrolyte of 2 wt % (0.16 M) lithium difluoro(oxalato)borate (LiDFOB) in standard carbonate solvents. This electrolyte exhibits a record-low salt/solvent mass ratio reported to date, thus pointing to a superior low cost. Furthermore, this electrolyte is highly compatible with commercial Li-ion materials, forming stable and inorganic-rich interphases on the lithium cobalt oxide (LiCoO2) cathode and graphite anode. Consequently, the LiCoO2-graphite full cell demonstrates excellent cycling performance. Besides, this electrolyte is moisture-resistant and effectively suppresses the generation of hydrogen fluoride, which will markedly facilitate the battery assembly and recycling process under ambient conditions.

Non-Flammable Sodium Asymmetric Imide Salt-Based Deep Eutectic Solvent for Supercapacitor Applications

This study reports two deep eutectic solvents (DESs) based on alkaline imide salts with asymmetric anions as functional electrolytes for supercapacitor (SC) application. The eutectic mixture of sodium (fluorosulfonyl) (trifluoromethanesulfonyl) imide (NaFTFSI) or sodium cyano-trifluoromethanesulfonyl imide (NaTFSICN) with ethylene carbonate (EC) delivers a non-flammable and stable liquid. The eutectic diagrams of the electrolytes directed to an optimal composition ( w salt = 0.25), hinging to that of conventional carbonate-based electrolytes, i.e., 1 mol L -1 . The volumetric properties of the DESs revealed a "stacking" effect, reflecting a strong coordination bond between the imide and EC anions without solvating the Na + cations. The DES transport properties (i.e., viscosity, conductivity, and ionicity) and temperature variations designate a high organization, similar to ionic liquids. The DESs, when coupled with activated carbon electrodes in a two-electrode symmetric configuration, yield specific capacities of 150 F g -1 at a normalized current density of 0.5 A g -1 (and 120 F g -1 at 2 A g -1 ). The SC maintained 80% of its initial capacity beyond 100 h of floating at an operating voltage of 2.4 V and showed a 150 mV per hour potential loss under self-discharge. The devised eutectic mixtures offer a promising new pathway for simple, safe, and effective electrolytes for SC applications.

In Situ Recombination of Elements in Spent Lithium-Ion Batteries to Recover High-Value γ-LiAlO2 and LiAl5O8

Recovering valuable materials from spent lithium-ion batteries is an important task because of the asymmetry in resource distribution, supply, and demand around the world. A lithium-ion battery is a combination system of various elements and their oxides. Current recovering technologies focus on the separation of valuable metal elements. They can inescapably bring secondary contamination and cost to the environment due to the addition of leachants and precipitants. To recover valuable materials, in situ recombination of elements in spent lithium-ion batteries can be a more economical and environment-friendly solution. Herein, we developed a technology based on in situ aluminothermic reduction and interstitial solid solution transformation to recover high-value γ-LiAlO₂ and LiAl₅O₈ under vacuum and high-temperature (1723 K) conditions. It was found that the process of Li₂O filling into the lattice of O-Al-O structure is an energy-reducing process, while LiAl₅O₈ was an existing high-energy transition-state matter. Since there was no wastewater generated, the process brought a new environment-friendly method for recovering valuable metals from spent lithium-ion batteries. This study also provides new comprehension regarding the design for high-value products' recovery from multi-element mixed wastes on an atomic scale.