Doctor of Philosophy, Stanford University, CHEM-PHD (2014)
Bachelor of Science, Fudan University, Chemistry (2009)
Yi Cui, Postdoctoral Faculty Sponsor
- Nanomaterials for electrochemical energy storage FRONTIERS OF PHYSICS 2014; 9 (3): 323-350
A pomegranate-inspired nanoscale design for large-volume-change lithium battery anodes
2014; 9 (3): 187-192
Silicon is an attractive material for anodes in energy storage devices, because it has ten times the theoretical capacity of its state-of-the-art carbonaceous counterpart. Silicon anodes can be used both in traditional lithium-ion batteries and in more recent Li-O2 and Li-S batteries as a replacement for the dendrite-forming lithium metal anodes. The main challenges associated with silicon anodes are structural degradation and instability of the solid-electrolyte interphase caused by the large volume change (∼300%) during cycling, the occurrence of side reactions with the electrolyte, and the low volumetric capacity when the material size is reduced to a nanometre scale. Here, we propose a hierarchical structured silicon anode that tackles all three of these problems. Our design is inspired by the structure of a pomegranate, where single silicon nanoparticles are encapsulated by a conductive carbon layer that leaves enough room for expansion and contraction following lithiation and delithiation. An ensemble of these hybrid nanoparticles is then encapsulated by a thicker carbon layer in micrometre-size pouches to act as an electrolyte barrier. As a result of this hierarchical arrangement, the solid-electrolyte interphase remains stable and spatially confined, resulting in superior cyclability (97% capacity retention after 1,000 cycles). In addition, the microstructures lower the electrode-electrolyte contact area, resulting in high Coulombic efficiency (99.87%) and volumetric capacity (1,270 mAh cm(-3)), and the cycling remains stable even when the areal capacity is increased to the level of commercial lithium-ion batteries (3.7 mAh cm(-2)).
View details for DOI 10.1038/NNANO.2014.6
View details for Web of Science ID 000332637200011
View details for PubMedID 24531496
- High-capacity Li2S-graphene oxide composite cathodes with stable cycling performance CHEMICAL SCIENCE 2014; 5 (4): 1396-1400
- Elastic moduli of polycrystalline Li15Si4 produced in lithium ion batteries JOURNAL OF POWER SOURCES 2013; 242: 732-735
- MoSe2 and WSe2 Nanofilms with Vertically Aligned Molecular Layers on Curved and Rough Surfaces NANO LETTERS 2013; 13 (7): 3426-3433
Nanoporous silicon networks as anodes for lithium ion batteries
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2013; 15 (2): 440-443
Nanoporous silicon (Si) networks with controllable porosity and thickness are fabricated by a simple and scalable electrochemical process, and then released from Si wafers and transferred to flexible and conductive substrates. These nanoporous Si networks serve as high performance Li-ion battery electrodes, with an initial discharge capacity of 2570 mA h g(-1), above 1000 mA h g(-1) after 200 cycles without any electrolyte additives.
View details for DOI 10.1039/c2cp44046f
View details for Web of Science ID 000311963600004
View details for PubMedID 23183772
A Yolk-Shell Design for Stabilized and Scalable Li-Ion Battery Alloy Anodes
2012; 12 (6): 3315-3321
Silicon is regarded as one of the most promising anode materials for next generation lithium-ion batteries. For use in practical applications, a Si electrode must have high capacity, long cycle life, high efficiency, and the fabrication must be industrially scalable. Here, we design and fabricate a yolk-shell structure to meet all these needs. The fabrication is carried out without special equipment and mostly at room temperature. Commercially available Si nanoparticles are completely sealed inside conformal, thin, self-supporting carbon shells, with rationally designed void space in between the particles and the shell. The well-defined void space allows the Si particles to expand freely without breaking the outer carbon shell, therefore stabilizing the solid-electrolyte interphase on the shell surface. High capacity (?2800 mAh/g at C/10), long cycle life (1000 cycles with 74% capacity retention), and high Coulombic efficiency (99.84%) have been realized in this yolk-shell structured Si electrode.
View details for DOI 10.1021/nl3014814
View details for Web of Science ID 000305106400110
View details for PubMedID 22551164
Engineering Empty Space between Si Nanoparticles for Lithium-Ion Battery Anodes
2012; 12 (2): 904-909
Silicon is a promising high-capacity anode material for lithium-ion batteries yet attaining long cycle life remains a significant challenge due to pulverization of the silicon and unstable solid-electrolyte interphase (SEI) formation during the electrochemical cycles. Despite significant advances in nanostructured Si electrodes, challenges including short cycle life and scalability hinder its widespread implementation. To address these challenges, we engineered an empty space between Si nanoparticles by encapsulating them in hollow carbon tubes. The synthesis process used low-cost Si nanoparticles and electrospinning methods, both of which can be easily scaled. The empty space around the Si nanoparticles allowed the electrode to successfully overcome these problems Our anode demonstrated a high gravimetric capacity (~1000 mAh/g based on the total mass) and long cycle life (200 cycles with 90% capacity retention).
View details for DOI 10.1021/nl203967r
View details for Web of Science ID 000299967800063
View details for PubMedID 22224827
Enhancing the Supercapacitor Performance of Graphene/MnO2 Nanostructured Electrodes by Conductive Wrapping
2011; 11 (10): 4438-4442
MnO2 is considered one of the most promising pseudocapactive materials for high-performance supercapacitors given its high theoretical specific capacitance, low-cost, environmental benignity, and natural abundance. However, MnO2 electrodes often suffer from poor electronic and ionic conductivities, resulting in their limited performance in power density and cycling. Here we developed a "conductive wrapping" method to greatly improve the supercapacitor performance of graphene/MnO2-based nanostructured electrodes. By three-dimensional (3D) conductive wrapping of graphene/MnO2 nanostructures with carbon nanotubes or conducting polymer, specific capacitance of the electrodes (considering total mass of active materials) has substantially increased by ?20% and ?45%, respectively, with values as high as ?380 F/g achieved. Moreover, these ternary composite electrodes have also exhibited excellent cycling performance with >95% capacitance retention over 3000 cycles. This 3D conductive wrapping approach represents an exciting direction for enhancing the device performance of metal oxide-based electrochemical supercapacitors and can be generalized for designing next-generation high-performance energy storage devices.
View details for DOI 10.1021/nl2026635
View details for Web of Science ID 000295667000073
View details for PubMedID 21942427
Interconnected Silicon Hollow Nanospheres for Lithium-Ion Battery Anodes with Long Cycle Life
2011; 11 (7): 2949-2954
Silicon is a promising candidate for the anode material in lithium-ion batteries due to its high theoretical specific capacity. However, volume changes during cycling cause pulverization and capacity fade, and improving cycle life is a major research challenge. Here, we report a novel interconnected Si hollow nanosphere electrode that is capable of accommodating large volume changes without pulverization during cycling. We achieved the high initial discharge capacity of 2725 mAh g(-1) with less than 8% capacity degradation every hundred cycles for 700 total cycles. Si hollow sphere electrodes also show a Coulombic efficiency of 99.5% in later cycles. Superior rate capability is demonstrated and attributed to fast lithium diffusion in the interconnected Si hollow structure.
View details for DOI 10.1021/nl201470j
View details for Web of Science ID 000292849400066
View details for PubMedID 21668030