Investigation of electrochemical reduction of GeO2 to Ge in molten CaCl2-NaCl

Rong, Liangbin; He, Rui; Wang, Zhiyong; Peng, Junjun; Jin, Xianbo

doi:10.1016/j.electacta.2014.09.107

Cited by 27 publications

(21 citation statements)

References 43 publications

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“…For the GeO 2 , four obvious redox peak pairs (A1/C1, A2/C2, A3/C3, and A4/C4) can be observed, which suggests the multiple steps of the GeO 2 reduction. GeO 2 can be reduced from C0 to C1 (from −0.5 to −1.1 V vs Ag/Ag + ), and the Ca (or Na)–Ge intermetallic compound can be generated from C2 to C4. , As shown in Figure S1b, the absolute decomposition voltage of the CaCl 2 –NaCl molten salt in the two-electrode cell is measured to be about 3.1 V at 600 °C, which corresponds to the voltage of −2.5 V vs Ag/Ag + in the three-electrode cell. Therefore, the voltage of the electrolysis should be between 1.1 and 1.7 V by considering the voltage gap between the decomposition of the CaCl 2 –NaCl molten salt and the reduction of GeO 2 in the two-electrode and three-electrode cells.…”

Section: Resultsmentioning

confidence: 99%

“…Molten-salt electrolysis is an effective and rapid method to synthesize metals, alloys, and semiconductors. − Recently, alloy-type anode materials (particularly Si and Ge) with different morphologies and structures have been synthesized by this method. − By controlling the electrolytic voltage, crystalline Si/Ge alloy nanotubes could be directly fabricated by the electrolysis of the SiO 2 /GeO 2 mixture in a CaCl 2 –NaCl binary molten salt . Although Ge nanostructures can be prepared by molten-salt electrolysis, − the precise and large-scale fabrication with satisfying structure control is still challenging. Moreover, the electrochemical performance of Ge nanowires by molten-salt electrolysis has only been rarely studied, which is still far from satisfying .…”

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confidence: 99%

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Germanium Nanowires via Molten-Salt Electrolysis for Lithium Battery Anode

Liu

Zhang

et al. 2022

ACS Nano

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Germanium (Ge)-based materials can serve as promising anode candidates for high-energy lithium-ion batteries (LIBs). However, the rapid capacity decay caused by huge volume expansion severely retards their application. Herein, we report a facile and controllable synthesis of Ge nanowire anode materials through molten-salt electrolysis. The optimal Ge nanowires can deliver a capacity of 1058.9 mAh g–1 at 300 mA g–1 and a capacity above 602.5 mAh g–1 at 3000 mA g–1 for 900 cycles. By in situ transmission electron microscopy and in situ X-ray diffraction, the multiple-step phase transformation and good structural reversibility of the Ge nanowires during charge/discharge are elucidated. When coupled with a lithium-rich Li1.2Mn0.567Ni0.167Co0.067O2 cathode in a full battery, the Ge nanowire anode leads to a relatively stable capacity with a retention of 84.5% over 100 cycles. This research highlights the significance of molten-salt electrolysis for the synthesis of alloy-type anode materials toward high-energy LIBs.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Germanium Nanowires via Molten-Salt Electrolysis for Lithium Battery Anode

Liu

Zhang

et al. 2022

ACS Nano

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“…From the blank experiment, the reduction and oxidation peak of the leftmost DD 1 can be observed. This may be the peak corresponding to Ca 2+ and Ca or the corresponding peak of Na + and Na [ 21 ], because the thermodynamic calculation software HSC Chemistry 6.0 is adopted by Formula (1). It is calculated that the theoretical decomposition voltages of NaCl and CaCl 2 at 1023 K are −3.238 and −3.325 V, respectively, and there is not much difference between the two, which makes it difficult to distinguish the positions of peaks.…”

Section: Resultsmentioning

confidence: 99%

Study on the Behavior of Electrochemical Extraction of Cobalt from Spent Lithium Cobalt Oxide Cathode Materials

et al. 2021

Materials

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The molten salt electrochemical method was used to reduce the Co in spent LiCoO2. The reduction mechanism of Co (III) in LiCoO2 was analyzed by cyclic voltammetry, square wave voltammetry, and open circuit potential. The reduction process of Co (III) on Fe electrode was studied in NaCl-CaCl2-LiCoO2 molten salt system at 750 °C. The results show that the reduction process of Co (III) is a two-step reduction: Co (III) → Co (II) → Co (0) and they are all quasi-reversible processes controlled by diffusion. Phase analysis (XRD) shows that Li+ and Cl2− in the molten salt form LiCl electrolysis experiments with different voltages were carried out, which proved the stepwise reduction of Co in LiCoO2.

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“…According to thermodynamic calculations, the E θ of the Fe 2 O 3 reduction to produce Fe is negative, which indicates that this reaction proceeds spontaneously at a temperature of 1173 K. When a potential is applied, Fe 2 O 3 (E = −0.8486 V) can be electrochemically reduced to Fe in a short time; therefore, no reduction peak was detected. Peak C 3 could be attributed to the cathodic formation of Ca in molten CaCl 2 [24,25]. As the electrolysis progressed, titanium oxides in the sample surface were reduced to Ti or low-valence oxides with a higher decomposition voltage; these oxides were easily oxidized, which caused a decrease in the oxidation peak potential.…”

Section: Effect Of the Duration Of The Electrolysis Process On The Phmentioning

confidence: 99%

Production of Fe–Ti Alloys from Mixed Slag Containing Titanium and Fe2O3 via Direct Electrochemical Reduction in Molten Calcium Chloride

Wang

Chen

et al. 2020

Metals

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High-purity intermetallic β-Ti (FeTi4) and FeTi alloys were prepared via molten salt electrolysis from a titanium-containing waste slag and Fe2O3 mixture using molten CaCl2 salt as the electrolyte. The mixed slag powders were pressed into a pellet that served as a cathode, while a graphite rod served as an anode. The electrochemical process was conducted at 900 °C with a cell voltage of 3.1 V under an inert atmosphere. The formation process of the alloys and the influence of the Ti:Fe atomic ratio on the product were investigated. With an increased proportion of Ti, the phase of the product changed from FeTi/Fe2Ti to FeTi/FeTi4, and different structures were observed. At a Ti:Fe ratio of 1.2:1 in the raw slag, an alloy with a sponge-like morphology and a small amount of FeTi4 were obtained. During the initial stages of electrolysis, a large amount of intermediate product (CaTiO3) was formed, accompanied by an abrupt decrease in current and increase in particle size. The current then increased and Fe2Ti alloy was gradually formed. Finally, as the reaction process extended inside the pellet, the current remained stable and the product mainly contained FeTi and FeTi4 phases. The observed stages, i.e., CaTiO3(TiO2) → Fe2Ti(Ti) → FeTi(FeTi4), were consistent with the thermodynamic analysis.

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Investigation of electrochemical reduction of GeO2 to Ge in molten CaCl2-NaCl

Cited by 27 publications

References 43 publications

Germanium Nanowires via Molten-Salt Electrolysis for Lithium Battery Anode

Germanium Nanowires via Molten-Salt Electrolysis for Lithium Battery Anode

Study on the Behavior of Electrochemical Extraction of Cobalt from Spent Lithium Cobalt Oxide Cathode Materials

Production of Fe–Ti Alloys from Mixed Slag Containing Titanium and Fe2O3 via Direct Electrochemical Reduction in Molten Calcium Chloride

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