Spinodal Decomposition Method for Structuring Germanium–Carbon Li-Ion Battery Anodes

Abstract

To increase the energy density of lithium-ion batteries (LIBs), high-capacity anodes which alloy with Li ions at a low voltage against Li/Li+ have been actively pursued. So far, Si has been studied the most extensively because of its high specific capacity and cost efficiency; however, Ge is an interesting alternative. While the theoretical specific capacity of Ge (1600 mAh g–1) is only half that of Si, its density is more than twice as high (Ge, 5.3 g cm–3; Si, 2.33 g cm–3), and therefore the charge stored per volume is better than that of Si. In addition, Ge has a 400 times higher ionic diffusivity and 4 orders of magnitude higher electronic conductivity compared to Si. However, similarly to Si, Ge needs to be structured in order to manage stresses induced during lithiation and many reports have achieved sufficient areal loadings to be commercially viable. In this work, spinodal decomposition is used to make secondary particles of about 2 μm in diameter that consist of a mixture of ∼30 nm Ge nanoparticles embedded in a carbon matrix. The secondary structure of these germanium–carbon particles allows for specific capacities of over 1100 mAh g−1 and a capacity retention of 91.8% after 100 cycles. Finally, high packing densities of ∼1.67 g cm–3 are achieved in blended electrodes by creating a bimodal size distribution with natural graphite.

Binder-free germanium nanoparticle decorated multi-wall carbon nanotube anodes prepared via two-step electrophoretic deposition for high capacity Li-ion batteries

“…A plateau at 0.4 V can be clearly seen in the charge profile, which corresponds to the delithiation process for the formation of Ge. 4,31 The discharge–charge profile of the Ge/CNT-1 sample as shown in Fig. 4d displays similar behaviours to the Ge sample and matches well with the CV data of Ge/CNT-1.…”

“…Developing lithium-ion batteries (LIBs) with high energy and power densities for uses ranging from portable electronic devices to electric vehicles is a critical scientific challenge. 1–4 Materials that can give highly reversible capabilities at low voltages ( vs. Li/Li + ) are suitable to maximize the energy density of LIB anodes. Lithium (Li) alloying materials such as silicon (Si), tin (Sn) and germanium (Ge) have been recently receiving a lot of attention as their theoretical capacities are many times higher than those of commercially available anode materials such as graphite and lithium titanate.…”

“…Lithium (Li) alloying materials such as silicon (Si), tin (Sn) and germanium (Ge) have been recently receiving a lot of attention as their theoretical capacities are many times higher than those of commercially available anode materials such as graphite and lithium titanate. 4–7 Among those potential anode materials, Ge has attractive properties for LIBs because it possesses a higher theoretical capacity (1384 mA h g −1 ) than Sn (847 mA h g −1 ) and has better Li + diffusivity (400 times higher than Si) and higher electrical conductivity (104×) than Si, which has led to promising fast-charging ability and cycling stability of Ge anodes. 7–11 However, the limited charge transport and huge volume expansion (>300%) of Ge during the Li + insertion/extraction processes remain issues.…”

Exfoliation and restacking route to Keggin-Al13-treated layered ruthenium oxide for enhanced lithium ion storage performance

“…However, similar to other metal-oxide materials that undergo conversion reactions with lithium-ions, ruthenium oxide exhibits limitations due to poor cycling stability caused by volume expansion issues during lithiation. 26–30 To address these issues, ruthenium oxide with a lamellar structure was used as an anode material to improve electrochemical performance and stability. This was achieved by intercalating Keggin-Al 13 ions into ruthenium oxide nanosheets as a host material (Scheme 1).…”

First-Principles Dynamics Investigation of Germanium as an Anode Material in Multivalent-Ion Batteries

“…One material that was widely investigated as a highly promising material for the next generation of anodes in LIBs is germanium (Ge) [21,[24][25][26][27] because of its high specific capacity (1624 and 1384 mA•h•g −1 for Li 22 Ge 5 and Li 15 Ge 4 alloys, respectively [28]), superb rate performance, and good cycling reliability due to its fast kinetics for both Li + ion diffusion and electronic conduction [27,[29][30][31]. However, as with other alloy-based materials used in negative electrodes in LIBs, Ge undergoes large volume changes in the fully lithiated state of Li 22 Ge 5 .…”