Pre-Lithiation Strategy on Graphite-Silicon Diffusion-Dependent Electrode for High-Performance All-Solid-State Batteries
Authors: Lee Jongjun , Jin Dahee , Lee Hyobin , Kim Ju Young , Lee Yong Min 
Published: September 2023

All-solid-state batteries (ASSBs) have emerged as promising next-generation energy storage devices due to their low fire risk and high potential for high energy density. Solid electrolytes with low flammability can reduce safety concerns about fire/explosion incidents under abnormal conditions. More importantly, high energy density can be achieved using active materials with high specific capacities, such as Li metal, Si, or Ni-rich cathode material. In order to maximize the energy density of ASSBs, the electrode thickness should be reduced while increasing the areal capacity of the electrode. In this regard, graphite-silicon (Gr-Si) diffusion-dependent electrodes (DDEs) have tremendous advantages. The intra- and inter-diffusion-based Li+ transfer in DDE does not require additional SEs to form Li+ conduction pathways within the electrode. The absence of SEs in the electrode has a significant advantage in terms of volumetric and gravimetric energy density. Moreover, the addition of silicon, which has remarkable volumetric capacities, effectively reduces the thickness of the DDE while maintaining the areal capacity high. Reducing the thickness of the DDE not only dramatically increases the volumetric energy density, but also shortens the diffusion length within the electrode, enabling rapid charge/discharge. Due to their outstanding advantages, the Gr-Si DDE has attracted much attention as a promising electrode for ASSBs with high energy density. Regardless of aforementioned advantages, the Gr-Si DDEs suffer from irreversible capacity loss at the first charge/discharge cycle due to the low first coulombic efficiency (C.E.) (< 80 %) of Si. Furthermore, Si undergoes extreme volume changes of over 400% during charge/discharge cycling. This huge volume change during cycling causes the cracking and pulverization of Si particles, leading to increased internal resistance, the isolation of the active materials, and the significant structural collapse of the electrode.

Thus, in this work, we propose a new pre-lithiation strategy on Gr-Si DDE for high-performance ASSBs. Pre-lithiation is an effective method to alleviate the problems of Si. The Li+ in the Gr-Si electrode lithiated by pre-lithiation can compensate for the irreversible capacity loss at the first charge/discharge cycle and improve the low first C.E. of the Gr-Si electrode. Furthermore, it can mitigate the volume expansion concerns such as Si pulverization and electrode structure degradation, since the pre-volume expansion can alleviate the extreme volume expansion of Si during cycling. By applying this powerful technique to Gr-Si DDE, we could realize ASSBs with high efficiency, high stability, and high performance. When the pre-lithiated Gr-Si DDE was applied to ASSBs, it showed higher first C.E. than the cell with Gr-Si DDE without pre-lithiation. Moreover, the cell with pre-lithiated Gr-Si DDE has high resistance to electrochemo-mechanical degradation, which comes from continuous and extreme volume changes at the electrode during charge/discharge cycling. The cell with pre-lithiated Gr-Si DDE exhibited excellent capacity retention of 85 % after 0.5 C charge/0.5 C discharge 200 cycles, while the cell with Gr-Si DDE only showed capacity retention of 65 %. Our pre-lithiation strategy effectively enhanced the efficiency and stability of high-performance Gr-Si DDE, and we believe that our approach can contribute to the commercialization of ASSBs with high energy density.

J. Y. Kim, J. Park, M. J. Lee, S. H. Kang, D. O. Shin, J. Oh, J. Kim, K. M. Kim, Y.-G. Lee, Y. M. Lee, ACS Energy Letters
2020, 5, 2995.

J. Y. Kim, S. Jung, S. H. Kang, J. Park, M. J. Lee, D. Jin, D. O. Shin, Y.-G. Lee, Y. M. Lee, Advanced Energy Materials
2022, 12, 2103108.

J. Y. Kim, S. Jung, S. H. Kang, M. J. Lee, D. Jin, D. O. Shin, Y.-G. Lee, Y. M. Lee, Journal of Power Sources
2022, 518, 230736.