Fracture Toughness Characterization of Lithiated Germanium as an Anode Material for Lithium-Ion Batteries

Abstract

Germanium (Ge) is a promising candidate anode material for next-generation, high-performance lithium-ion batteries. Despite its apparent promise, the mechanical properties of lithiated Ge including its fracture characteristic are largely unknown. In this paper, we report the first experimental measurement of the fracture toughness of lithiated Ge using an in-house developed nanoindentation system. The fracture toughness of lithiated Ge is found to increase monotonically with increasing lithium content, indicating a brittle-to-ductile transition of lithiated Ge as lithiation proceeds. We also compare the fracture energy of lithiated Ge with that of lithiated Si and show that, despite a slightly lower fracture energy of Ge than that of Si in the unlithiated state, Ge possesses much higher fracture resistance than Si in the lithiated state. These findings suggest that Ge anodes are intrinsically more resistant to fracture than their Si counterparts, thereby offering substantial potential for the development of durable, high-capacity, and high-rate lithium-ion batteries. The quantitative results from this work provide fundamental insights for developing new electrode materials and help to enable predictive modeling of high-performance lithium-ion batteries. Rechargeable lithium-ion batteries (LIBs) are the current dominant energy storage solution for portable electronics and electric vehicles. The growing demand in these applications, however, requires next-generation LIBs with an unprecedented combination of low cost, high capacity, and high reliability. To significantly enhance the LIB performance, much of the research effort to date has been devoted to developing new electrode materials that can store more Li ions than the current available technology. In today's commercial LIBs, graphite of 372 mAhg −1 capacity is being widely used as the anode material.

High‐Voltage‐Driven Surface Structuring and Electrochemical Stabilization of Ni‐Rich Layered Cathode Materials for Li Rechargeable Batteries

“…The reduction of the oxidation state of Ni from Ni 3+ to Ni 2+ is attributed to the phase transformation from layered LiNi 0.895 Co 0.085 Mn 0.02 O 2 to spinel and rock‐salt phases. [ 51,52 ] Negligible changes in the spectra were observed until ten cycles, as shown in Figure 4b; however, a significant change occurred after 50 cycles. As cycling proceeded, a large amount of Ni 2+ compounds such as spinel or rock‐salt phases were gradually formed on the particle surface due to the transition metal migration and subsequent segregation.…”

Enhanced Electrochemical Performance of Ni‐Rich Layered Cathode Materials by using LiPF6 as a Cathode Additive

“…Figure a and Figure b compare voltage profiles of the initial two cycles of Li/NCM811 cells with the pristine and LiPF 6 ‐added NCM811, respectively. In the initial two cycles, the cell was charged to 4.5 V in order to form a NiO cubic protective layer on the surface of NCM particles . It is observed from Figure a and Figure b that there are no much differences in the specific capacity and coulombic efficiency except for the charging voltage, showing that the cells with LiPF 6 ‐added NCM811 have slightly larger polarization (see inset in Figure a and Figure b).…”

Improved Cycling Stability of LiNi0.8Co0.1Mn0.1O2 Cathode Material via Variable Temperature Atomic Surface Reduction with Diethyl Zinc

“…It reflects less structural integrity, more deformation of crystal structure, and probable cracks in the NCM cathode at the final discharged state. [ 41 ] The visual intergranular micro‐cracks are observed in NCM cathodes; however, it is significantly suppressed in NCM 200 (Figure 8c–f).…”