Electrochemical Performance of Amorphous GeO_xPowder Synthesized by Oxidation of NaGe Serving as an Anode for Lithium Ion Batteries

Abstract

A highly amorphous GeO x powder has been synthesized by a soft chemical method. The method involves sodium germanium NaGe of Zintl phase was simply oxidized by isopropyl alcohol at room temperature and placed into distilled water. Amorphous GeO x powder serving as an anode for a Li-ion battery exhibited a high reversible capacity of 1268 mAh g −1 , high rate ability of 1035 mAh g −1 (current rate of 6A g −1 ) and good cycle performance of 930 mAh g −1 after 30 cycles. Thereby, our amorphous GeO x is to be potential anode material for Li-ion batteries.

Etching Asymmetric Germanium Membranes with Hydrogen Peroxide for High‐Capacity Lithium‐Ion Battery Anodes

“…However, CA Ge Mem and PAN Ge Mem did suffer from 73.6% and 75.5% capacity losses in 50 cycles at 160 mA g −1 because Ge concentrations are very high (63.0 and 75.2 wt%, respectively), entailing a large electrode volume change that can cause serious electrode delamination and pulverization (Table and Figure a). It is noteworthy that such cyclability is still much better than that of micrometer powder Ge control, whose capacity was eroded to less than 270 mAh g −1 after two formation cycles and further reduced to less than 160 mAh g −1 in as few as ten cycles at 160 mA g −1 (Figure S4, Supporting Information), whose results are consistent with literature reports …”

“…Recall that Ge powders have a wide size distribution ranging from submicrometer to 10 μm, which can affect the delithiation overpotentials and thus broaden the oxidation peak. The small and broad anodic peak centered at 1.1 V corresponds to the oxidation of Ge, as reported in the literature . In the following three CVs, the 0.82 V cathodic peak corresponding to the reduction of GeO 2 disappeared, which confirms that the electrochemical reaction shown in Equation is highly irreversible.…”

“…It is noteworthy that such cyclability is still much better than that of micrometer powder Ge control, whose capacity was eroded to less than 270 mAh g À1 after two formation cycles and further reduced to less than 160 mAh g À1 in as few as ten cycles at 160 mA g À1 (Figure S4, Supporting Information), whose results are consistent with literature reports. [11,24] To enhance the cycling stability of asymmetric Ge membranes as the LIB anode, we initially managed to etch CA Ge Mem using concentrated hydrogen peroxide solutions to generate an oxide layer and extra void space to better accommodate the large volume change. But the membrane was relatively fragile and thus broken into pieces during H 2 O 2 etching.…”

“…Although these nanostructures do enable a much improved electrochemical performance, the high fabrication cost and low scalability may seriously hinder their practical applications . In this regard, it is more cost effective to utilize readily available micrometer‐size Ge powders, given that the serious volume expansion issue can be appropriately resolved . Herein, we present a simple, low‐cost, scalable, and effective method to synthesize various asymmetric Ge membranes utilizing micrometer‐size Ge powders as raw materials.…”

“…[5] In this regard, it is more cost effective to utilize readily available micrometer-size Ge powders, given that the serious volume expansion issue can be appropriately resolved. [11] Herein, we present a simple, low-cost, scalable, and effective method to synthesize various asymmetric Ge membranes utilizing micrometer-size Ge powders as raw materials. The asymmetric membranes were fabricated using a straightforward phaseinversion method, followed by hydrogen peroxide etching and surface coating, resulting in an outstanding capacity retention of 95% at %850 mAh g À1 in 50 cycles, applying a current density of 160 mA g À1 , whereas %100% capacity at %700 mAh g À1 can be maintained in 170 cycles, applying a current density of 400 mA g À1 .…”