All Solid State Battery with Soft Carbon–TiSi2 Multilayer Structure for Optimized LiSi Anodes
Sulfide-based all-solid-state batteries, with their excellent safety and high theoretical energy density, are considered a key development direction for next-generation high-energy-density energy storage technology. However, their practical application is limited by the performance shortcomings of anode materials: traditional graphite anodes are difficult to match the ever-increasing energy density requirements, while lithium metal anodes are plagued by dendrite growth and interfacial side reactions. Against this backdrop, silicon-based anodes, with their significant advantages of ultra-high theoretical capacity (3579 mAh g⁻¹) and low operating potential (0.4 V vs. Li⁺/Li), have become a highly promising alternative. In recent years, research on lithium-silicon alloy anodes in sulfide-based all-solid-state battery systems has achieved many breakthroughs—for example, by introducing hard carbon to build a three-dimensional conductive network, or by using pre-lithiation strategies to significantly improve the first-cycle coulombic efficiency and cycle stability. These achievements have all confirmed the feasibility of this technical route. Despite this, the application of lithium-silicon anodes still faces three major challenges: first, the problem of volume expansion, where silicon and lithium-silicon alloys undergo drastic volume expansion and contraction during cycling, leading to contact failure at the electrode-electrolyte interface; second, the issue of chemical compatibility, where silicon undergoes severe interfacial side reactions with sulfide solid electrolytes during cycling, resulting in increased interfacial impedance; and third, the risk of lithium dendrite growth, where abundant lithium sources in lithium-silicon anodes may induce lithium dendrites to penetrate the electrolyte layer, causing a short circuit in the battery. These core bottlenecks severely hinder the development of high-performance sulfide all-solid-state batteries. Therefore, developing innovative anode structures that can simultaneously address the problems of volume expansion, interfacial side reactions, and lithium dendrite formation has become an urgent need and a core research focus in the field.
Core Content Interpretation
Figure 1 | a) XRD pattern of ST0/5/10/20-BM; b) Enlarged view of the selected area in (a); c) XRD pattern of ST0/5/10/20-BM-St; d) Enlarged view of the selected area in (c).
Figure 2 | SEM images and corresponding EDS element distribution maps of ST0-BM-St, b) ST5-BM-St, c) ST10-BM-St, d) ST20-BM-St.
Figure 3 | a) Comparison of electronic conductivity of ST0/5/10/20; b) Rate performance of ST/LPSCI/LiIn half-cell; c) Rate performance of LCO/LPSCI/ST-SC-Li full cell; d) Voltage-specific capacity curve of ST0/5/10/20 half-cell at 0.1C; e) dQ/dV curve of ST0/5/10/20 half-cell at 0.1C during the second cycle; f) Voltage-specific capacity curve of ST5-SC-Li full cell at different rates.
Figure 4 | XPS spectra of ST5-SC-Li anode after cycling: a) Li 1s, b) C 1s, c) F 1s, d) S 2p. e–h): SEM images of the cross-section of ST0/5/10/20 SC-Li anode after cycling.
Figure 5 | a) Cyclic performance of LCO/LPSCI/ST-SC-Li full cells; b) Magnified view during cycle testing; c) dQ/dV curves of ST5-SC-Li cells at different cycle numbers; d–g) Voltage-specific capacity curves of ST0/5/10/20-SC-Li cells at different cycle numbers.
Figure 6 | LCO | ST5-SC-Li full cell, a) Cycling performance at 5C (6.4 mA cm⁻²). b) Voltage-specific capacity curves at different cycle numbers at 5C. c) Cycling performance at 2C (5.2 mA cm⁻²). d) Voltage-specific capacity curves at different cycle numbers at 2C. e) Cycling performance at 1C (6.4 mA cm⁻²). f) Voltage-specific capacity curves at different cycle numbers at 1C.
Figure 7 | SEM images of ST5-Li anode after lithium deposition: a) surface and b) cross section; c) SEM and EDS of ST5 sheet before cycling; d) SEM and EDS of ST5-SC-Li surface after cycling.
Figure 8 | LCO|ST5-SC-Li high areal capacity full cell, 10.3 mAh cm⁻²: a) Rate performance; b) Cycling at 0.1 C at different temperatures; c) 20.1 mAh cm⁻²: Voltage-areal capacity curve at 0.1 C; 10.3 mAh cm⁻²: d) Cycling performance; e) Voltage-specific capacity curves at 0.05 C and 0.1 C; LCO|ST5-Li (10.3 mAh cm⁻²): f) Voltage-specific capacity curves at 0.05 C and 0.1 C.
Conclusions and Outlook
This study utilizes ball milling and sintering processes to create a highly electronically conductive TiSi₂ network, constructing a three-dimensional rigid support structure encapsulating silicon particles. This structure effectively suppresses silicon volume expansion and provides interfacial pinning. The study combines a sulfide electrolyte (LPSCl) to establish an “ion-electron dual pathway,” introducing a soft carbon interlayer to buffer stress and suppress lithium dendrite growth, while a lithium metal layer achieves dynamic capacity compensation. This multi-layered synergistic design achieves coordinated optimization of the three core issues in silicon-based anodes: volume expansion, lithium dendrite growth, and interfacial instability. An LCO/LPSCl/ST5-SC-Li battery assembled with ST5 material containing 5% Ti exhibits no capacity decay after 64,000 cycles at 10C rate with a 0.64 mAh cm⁻² areal capacity, and a total charge-discharge time exceeding 10,000 hours. Even under high load conditions, this structure remains highly efficient, achieving stable cycling for 30 cycles (capacity retention > 90%) at a 10.3 mAh cm⁻² areal capacity, and achieving an ultra-high reversible areal capacity of 19.6 mAh cm⁻², while also possessing a wide operating temperature range. This research provides an innovative multilayer structure strategy for overcoming the bottlenecks in silicon-based anode applications, contributing to the development of high-energy-density sulfide-based all-solid-state batteries.
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