Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries

Abstract

This study demonstrates the full infiltration of gel polymer electrolyte into silicon-coated vertically aligned carbon nanofibers (Si-VACNFs), a high-capacity 3D nanostructured anode, and the electrochemical characterization of its properties as an effective electrolyte/separator for future all-solid-state lithium-ion batteries. Two fabrication methods have been employed to form a stable interface between the gel polymer electrolyte and the Si-VACNF anode. In the first method, the drop-casted gel polymer electrolyte is able to fully infiltrate into the open space between the vertically aligned core-shell nanofibers and encapsulate/stabilize each individual nanofiber in the polymer matrix. The 3D nanostructured Si-VACNF anode shows a very high capacity of 3450 mAh g(-1) at C/10.5 (or 0.36 A g(-1)) rate and 1732 mAh g(-1) at 1C (or 3.8 A g(-1)) rate. In the second method, a preformed gel electrolyte film is sandwiched between an Si-VACNF electrode and a Li foil to form a half-cell. Most of the vertical core-shell nanofibers of the Si-VACNF anode are able to penetrate into the gel polymer film while retaining their structural integrity. The slightly lower capacity of 2800 mAh g(-1) at C/11 rate and ∼1070 mAh g(-1) at C/1.5 (or 2.6 A g(-1)) rate have been obtained, with almost no capacity fade for up to 100 cycles. Electrochemical impedance spectroscopy does not show noticeable changes after 110 cycles, further revealing the stable interface between the gel polymer electrolyte and the Si-VACNFs anode. These results show that the infiltrated flexible gel polymer electrolyte can effectively accommodate the stress/strain of the Si shell due to the large volume expansion/contraction during the charge-discharge processes, which is particularly useful for developing future flexible solid-state lithium-ion batteries incorporating Si-anodes.

Composite Nanofibers as Advanced Materials for Li-ion, Li-O2 and Li-S Batteries

“…Ge, SnO2, MnOx, iron oxides, and TiO2 [22,164,165] have been developed to improve the electrochemical performances of LiSi electrode. In the Si/metal binary alloys composites [26,27,[165][166][167][168][169][170], the metal/metal oxides act as the unlithiated part of the composite alloy thereby forming a framework that prevents the pulverization of the Si particles [6], improve stability and [3,167,[171][172][173][174][175][176][177][178][179][180][181] (Fig.4). The carbon nanofiber in the matrix acts as a buffer for the volume change and improves the electronic conductivity of the electrode.…”

A Micromolding Method for Transparent and Flexible Thin‐Film Supercapacitors and Hybrid Supercapacitors

“…The poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP)/tetraethylammonium tetrafluoroborate (Et 4 NBF 4 ) gel electrolyte was prepared according to a previous report. [ 25 ] The electrolyte solution was prepared by dissolving 0.5 mol Et 4 NBF 4 (99%, Aldrich) in 500 mL acetonitrile (99.9%, extra dry over a molecular sieve, Acros). 5 g of the host polymer (PVDF‐HFP) ( M W ≈ 400 000, Aldrich) was separately dissolved in 30 g tetrahydrofuran by magnetic stirring at ≈60 °C.…”

Advanced Matrixes for Binder‐Free Nanostructured Electrodes in Lithium‐Ion Batteries

“…The relationship between loading mass of active materials and prices of corresponding supporting matrixes for binder‐free electrodes in LIBs. [ 48–109,141–240 ] ...…”