image: A rambutan-inspired tri-layer composite design unlocks the high capacity of Si, achieving an optimized equilibrium among strain accommodation, transport kinetics, and interfacial stability.
Credit: ©Science China Press
Lithium-ion batteries (LIBs) dominate portable electronics but fall short for electric vehicles’ energy density needs. Silicon (Si) is a promising anode candidate due to its high theoretical capacity, ideal discharge potential, eco-friendliness, and abundant reserves. However, its low electronic conductivity and large volume expansion (∼400%) during lithiation hinder commercialization, causing particle fragmentation, solid electrolyte interface (SEI) degradation, and loss of electrical contact. The stable cycling of Si-based electrodes remains challenging, primarily due to inadequate structural support and inefficient transport pathways. Assembling Si nanoparticles into secondary micron-sized particles is a common approach, while repeated cycling-induced internal strain still causes structural damage. Core-shell structures ensure electrical contact but have non-uniform strain distribution. Hollow structures offer buffer space but reduce volumetric energy density. Thus, an ideal secondary micron-sized structure combining mechanical strength and interconnectivity is urgently needed.
Researchers led by Prof. Liang Zhou from Wuhan University of Technology have reported a tri-layer rambutan-structured composite (TRC) anode material. The innovative design synergistically tackles the challenges of transport kinetics and interfacial stability. By leveraging the high capacity of silicon and effectively managing the strain from its volume changes, the TRC anode achieves remarkable performance, including high capacity (1089 mAh g−1 at 0.1 A g−1), ultrastable cyclability (580 mAh g−1 after 700 cycles at 0.5 A g−1), and low electrode swelling.
The innovative three-layer architecture includes: (1) inner layer (Sn/Cr2O3/C nanocomposite): rapid lithiation kinetics and moderate volume expansion, with self-adaptive Cr2O3/C continuum and fast Li⁺ transfer phases; (2) intermediate layer (Si nanoparticles in carbon shell): inherent strain relaxation and shortened Li⁺ diffusion path, with a conductive carbon matrix; (3) outermost layer (core-sheath Sn@carbon nanotubes): mechanical strength, dual Li⁺/e⁻ transport, and stress dispersion by mechanical constraint.
“Inspired by the hierarchical structure of rambutan fruits, we have proposed a tri-layer composite architecture that synergistically optimizes strain relaxation and Li+ transport,” explains corresponding author Prof. Liang Zhou. “This work offers a cost-efficient, scalable approach for constructing intricate Si-based nanostructures.”
The study was carried out by a collaborative research teams from State Key Laboratory of Advanced Technology for Materials Synthesis and Processing in Wuhan University of Technology and Laboratory of Advanced Materials in Fudan University. These institutions possess cutting-edge expertise in advanced materials and energy storage technologies, and are deeply committed to pioneering sustainable energy solutions.