FEC Additive for Improved SEI Film and Electrochemical Performance of the Lithium Primary Battery

The solid electrolyte interphase (SEI) film plays a significant role in the capacity and storage performance of lithium primary batteries. The electrolyte additives are essential in controlling the morphology, composition and structure of the SEI film. Herein, fluoroethylene carbonate (FEC) is chosen as the additive, its effects on the lithium primary battery performance are investigated, and the relevant formation mechanism of SEI film is analyzed. By comparing the electrochemical performance of the Li/AlF3 primary batteries and the microstructure of the Li anode surface under different conditions, the evolution model of the SEI film is established. The FEC additive can decrease the electrolyte decomposition and protect the lithium metal anode effectively. When an optimal 5% FEC is added, the discharge specific capacity of the Li/AlF3 primary battery is 212.8 mAh g−1, and the discharge specific capacities are respectively 205.7 and 122.3 mAh g−1 after storage for 7 days at room temperature and 55 °C. Compared to primary electrolytes, the charge transfer resistance of the Li/AlF3 batteries with FEC additive decreases, indicating that FEC is a promising electrolyte additive to effectively improve the SEI film, increase discharge-specific capacities and promote charge transfer of the lithium primary batteries.

Effect of Different Binder Proportions on Properties of Silicon-based Anode Materials

With the development of lithium-ion battery technology, silicon anode is deemed as an ideal next-generation anode materials by virtue of its extremely high specific capacity. Nevertheless, higher requirements are raised for the properties of the binder owing to the high volume change rate of silicon anode during charging and discharging and the thickening of SEI film. In respect of the binders such as polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium alginate (Alginate), sodium carboxymethylcellulose (CMC) in possession of large-scale application value, this paper studies the effects of different binders and mixed binders with different ratios on the properties of silicon anode materials. As a result, it is suggested that the binders acquired when PAA:PVA=9:1 can render it possible for the electrode to be provided with better charge-discharge cyclic performance.

Effect of Different Binder Proportions on Properties of Silicon-based Anode Materials

With the development of lithium-ion battery technology, silicon anode is deemed as an ideal next-generation anode materials by virtue of its extremely high specific capacity. Nevertheless, higher requirements are raised for the properties of the binder owing to the high volume change rate of silicon anode during charging and discharging and the thickening of SEI film. In respect of the binders such as polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium alginate (Alginate), sodium carboxymethylcellulose (CMC) in possession of large-scale application value, this paper studies the effects of different binders and mixed binders with different ratios on the properties of silicon anode materials. As a result, it is suggested that the binders acquired when PAA:PVA=9:1 can render it possible for the electrode to be provided with better charge-discharge cyclic performance.

Revisit Electrolyte Chemistry of Hard Carbon in Ether for Na Storage

Hard carbons (HC) as an anode material in sodium ion batteries, present enhanced electrochemical performances in ether-based electrolytes, making them promising potential in practical applications. However, the underlying mechanism behind the excellent performances is still in question. Here, ex-situ nuclear magnetic resonance, gas chromatography-mass spectrometry and high-resolution transmission electron microscope were used to clarify the insightful chemistry of ether- and ester-based electrolytes in terms of solid-electrolyte-interphase (SEI) on hard carbons. The results confirm the marked electrolyte decomposition and the formation of a SEI film in EC/DEC, but no SEI film in the case of diglyme. In-situ electrochemical quartz crystal microbalance and molecule dynamics support that ether molecules have been co-intercalated into hard carbons likely. To our knowledge, these results are reported for the first time. It might be very useful for us to rational design advanced electrode materials based HC in future.

Influence of nitrogen configuration on the electrochemical properties of carbonized poly(acrylonitrile)-ionic liquid as anode materials in lithium ion batteries

A sequence of N-doped carbon materials has been synthesized using poly(acrylonitrile)-ionic liquid copolymers as carbon precursors. The nitrogen content and configuration in carbon materials has been changed regularly within a certain range by adjusting the proportion of ionic liquids. We found that the capacity and rate performance increased dramatically after the introduction of ionic liquids, which was attributed to incorporation of higher amount pyridinic-N, pyrrolic-N into the carbon materials. Besides, with the increase of the graphitic-N, the initial Coulombic efficiency decreased from 58.5 % to 53.47 % and the RSEI raised from 66.34 Ω to 140.96 Ω, which was attributed to the higher cohesive energy of Li dimmer than adsorption energy of graphitic-N with Li, since more lithium clusters during the formation of SEI film were formed. The electrochemical tests also revealed the negative role of graphitic-N in the capacity. Therefore, this work provides a feasible method to design the nitrogen content and configuration of the N-doped carbon materials.