In Situ Synthesis and Characterization of Ge Embedded Electrospun Carbon Nanostructures as High Performance Anode Material for Lithium-Ion Batteries

Abstract

While active materials based on germanium (Ge) are considered as a promising alternative anodic electrode due to their relatively high reversible capacity and excellent lithium-ion diffusivity, the quite unstable structural/electrochemical stability and severe volume expansion or pulverization problems of Ge electrodes remain a considerable challenge in lithium ion batteries (LIBs). Here, we present the development of Ge embedded in one-dimensional carbon nanostructures (Ge/CNs) synthesized by the modified in situ electrospinning technique using a mixed electrospun solution consisting of a Ge precursor as an active material source and polyacrylonitrile (PAN) as a carbon source. The as-prepared Ge/CNs exhibit superior lithium ion behavior properties, i.e., highly reversible specific capacity, rate performance, Li ion diffusion coefficient, and superior cyclic stability (capacity retention: 85% at 200 mA g(-1)) during Li alloying/dealloying processes. These properties are due to the high electrical conductivity and unique structures containing well-embedded Ge nanoparticles (NPs) and a one-dimensional carbon nanostructure as a buffer medium, which is related to the volume expansion of Ge NPs. Thus, it is expected that the Ge/CNs can be utilized as a promising alternative anodic material in LIBs.

Structural Strategies for Germanium‐Based Anode Materials to Enhance Lithium Storage

“…Li et al prepared Ge@CNF by electrospinning using Ge NPs DMF‐PAN solution as precursor solution. Then using CVD deposited carbon onto Ge@CNF to gain Ge@CNF@C. Lee et al reported Ge/CNFs synthesized by electrospinning using a mixed electrospun solution consisting of GeCl 4 precursor as an active material source and PAN as a carbon source. Wang et al proposed a simple and cheap method through electrospinning followed by atomic layer deposition (ALD) to fabricate Ge@graphene@TiO 2 core–shell NFs (Ge@G@TiO 2 NFs).…”

“…Besides, some special structure Ge–C compounds show an excellent electrochemistry performance, Ge–C 1D or 2D materials also show remarkable performance. Ge embedded in 1D carbon nanostructures (Ge/CNs) exhibited capacity retention of 85% at 200 mA g −1 . Carbon‐sheathed single crystalline Ge NWs produced by an SLS method showed a high reversible charge capacity of 963 mAh g −1 at a rate of 0.5 C after 100 cycles .…”

Nanostructured electrode materials for lithium-ion and sodium-ion batteries via electrospinning

“…With the reduced mass diffusion length along Sn QDs and enhanced electronic conductivity of N-doped CNFs, the Sn QDs@CNFs dis- played long cyclability of 887 mA h g −1 after 200 cycles at a cycling rate of 0.1 A g −1 . Germanium (Ge) is another promising anode material with a high theoretical capacity (1624 mA h g −1 for GeLi 4.4 ), higher Li-ion diffusion coefficient and electrical conductivity than Si [120]. Ge is applied to prepare electrospun anode materials for LIBs to overcome strain from volume change after lithiation.…”

Are Electrospun Fibrous Membranes Relevant Electrode Materials for Li‐Ion Batteries? The Case of the C/Ge/GeO2 Composite Fibers

“…The gravimetric capacity (372 mAh g −1 ) of the commonly used graphite anodes is inadequate to meet the current requirements for energy storage systems. In the search for alternative anodes materials, the focus is mainly on transition metal oxides MO x , which store Li + ions through the conversion reaction MO x + 2 x Li + + 2 x e − ↔ M 0 + x Li 2 O, and IV group elements M 0 that are able to store larger amount of Li + ions through the alloying reaction M 0 + y Li + + y e − ↔ Li y M . Among the latter, germanium is the one endowed with by far superior properties (higher Li diffusivity and electronic conductivity, and smaller volume changes suffered during lithiation/delithiation process), which make it the most promising electrode material in spite of its smaller gravimetric capacity with respect to silicon (1624 against 4200 mAh g −1 ).…”

“…In the latest years, several studies have been conducted on electrode materials based on germanium and the cheaper germanium dioxide (GeO 2 ) . In GeO 2 , Li storage occurs via a conversion reaction leading to the irreversible formation of Li 2 O, which lowers down to 1126 mAh g −1 the gravimetric capacity attainable in the subsequent alloying reaction.…”