Various forms of germanium and germanium-containing compounds and materials are actively investigated as energy-intensive alternatives to graphite as the anode of lithium-ion batteries. The most accessible form—germanium dioxide—has the structure of a 3D polymer, which accounts for its rapid destruction during cycling, and requires the development of further approaches to the production of nanomaterials and various composites based on it. For the first time, we propose here the strategy of using 2-carboxyethylgermanium sesquioxide ([O1.5GeCH2CH2CO2H]n, 2-CEGS), in lieu of GeO2, as a promising, energy-intensive, and stable new source system for building lithium-ion anodes. Due to the presence of the organic substituent, the formed polymer has a 1D or a 2D space organization, which facilitates the reversible penetration of lithium into its structure. 2-CEGS is common and commercially available, completely safe and non-toxic, insoluble in organic solvents (which is important for battery use) but soluble in water (which is convenient for manufacturing diverse materials from it). This paper reports the preparation of micro- (flower-shaped agglomerates of ≈1 μm thick plates) and nanoformed (needle-shaped nanoparticles of ≈500×(50–80) nm) 2-CEGS using methods commonly available in laboratories and industry such as vacuum and freeze-drying of aqueous solutions of 2-CEGS. Lithium half-cell anodes based on 2-CEGS show a capacity of ≈400 mAh g−1 for microforms and up to ≈700 mAh g−1 for nanoforms, which is almost two times higher than the maximal theoretical capacity of graphite. These anodes are stable during the cycling at various rates. The results of DFT simulations suggest that Li atoms form the stable Li2O with the oxygen atoms of 2-CEGS, and actual charge–discharge cycles involve deoxygenated GeC3H5 molecules. Thus, C3 chains loosen the anode structure compared to pure Ge, improving its ability to accommodate Li ions.
Bibliographical noteFunding Information:
Material preparation and characterization were supported at Zelinsky Institute of Organic Chemistry by Russian Science Foundation Grant 17‐73‐20281. Evaluation of electrochemical properties of the materials in batteries was supported by Skolkovo Foundation at Skoltech. R.R.K. and P.A.T. also acknowledge general support from Russian Ministry of Science and Education received at IPCP RAS (project No. 0089‐2019‐0010 / AAAA‐A19‐119071190044‐3). Electron microscopy and NMR spectra characterization were performed in the Department of Structural Studies of Zelinsky Institute of Organic Chemistry, Moscow. Powder and single‐crystal X‐ray diffraction data were collected at the Centre for Collective Use of Kurnakov Institute of General and Inorganic Chemistry.
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