Electrolyte Engineering Empowers Li||CFx Batteries to Achieve High Energy Density and Low Self-Discharge at Harsh Conditions.

Given its exceptional theoretical energy density (over 2000 Wh kg-1), lithium||carbon fluoride (Li||CFx) battery has garnered global attention. N-methylpyrrolidone (NMP)-based electrolyte is regarded as one promising candidate for tremendously enhancing the energy density of Li||CFx battery, provided self-discharge challenges can be resolved. This study successfully achieves a low self-discharge (LSD) and desirable electrochemical performance in Li||CFx batteries at high temperatures by utilizing NMP as the solvent and incorporating additional ingredients, including vinylene carbonate additive, as well as the dual-salt systems formed by LiBF4 with three different Li salts, namely lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and LiNO3. The experimental results unfold that the proposed methods not only minimize aluminum current collector corrosion, but also effectively passivate the Li metal anode. Among them, LiNO3 exhibits the most pronounced effect that achieves an energy density of ≈2400 Wh kg-1 at a current density of 10 mA g-1 at 30 °C, nearly 0% capacity-fade rate after 300 h of storage at 60 °C, and the capability to maintain a stable open-circuit voltage over 4000 h. This work provides a distinctive perspective on how to realize both high energy density and LSD rates at high temperature of Li||CFx battery.

Molten salt method synthesis of multivalent cobalt and oxygen vacancy modified Nitrogen-doped MXene as highly efficient hydrogen and oxygen Evolution reaction electrocatalysts.

Nitrogen-doped Ti3C2Ty MXene with multivalent cobalt and oxygen vacancy (Vo) modification was obtained by using molten salt method and greatly improved electrocatalytic performance. The structural properties of MXene and the valence state of cobalt were adjusted by controlling the molten salt temperature. When the molten salt treatment temperature was 377 °C, the obtained 377-CoOxN1-x-Ti3C2Ty maintained the chemical structure of MXene well, and also has high Co2+ content and Vo content. Electrochemical test results showed that 377-CoOxN1-x-Ti3C2Ty had the lowest Hydrogen Evolution Reaction (HER) overpotential of 87.73 mV and good electrocatalytic stability. X-ray Photoelectron Spectroscopy (XPS) results and Density Functional Theory (DFT) calculations showed that the introduction of polyvalent cobalt and Vo in the nitrogen-doped Ti3C2Ty structure effectively reduced the energy barrier of the electrocatalytic reaction of MXene.

Boosting the Energy Density of Li||CFx Primary Batteries Using a 1,3-Dimethyl-2-imidazolidinone-Based Electrolyte.

Elevating the discharge voltage plateau is regarded as the most effective strategy to improve the energy density of Li||CFx batteries in consideration of the finite capacity of CFx (x ∼ 1) cathodes. Here, an electrolyte, with LiBF4 in 1,3-dimethyl-2-imidazolidinone (DMI)/1,2-dimethoxyethane (DME), is developed for the first time to substantially promote the discharge voltage of CFx without compromising the available discharge capacity. DME possesses the property of low viscosity, while DMI functions to increase the voltage plateau during discharge owing to its moderate nucleophilicity and donor number, which decreases the energy barrier for breaking C-F bonds. The optimized electrolyte exhibits a significantly high average discharge voltage of 2.69 V at a current density of 10 mA g-1, which is 11.6% higher than the control electrolyte (2.41 V). In addition, a high energy density of 2099 Wh kg-1 is achieved in the optimized electrolyte (vs 1905 Wh kg-1 in the control electrolyte), showing great potential for practical applications.