Zhiyuan Wang

Three-dimensional porous bowl-shaped carbon cages interspersed with carbon coated Ni–Sn alloy nanoparticles as anode materials for high-performance lithium-ion batteries

The structural damage induced by huge volume change during lithiation/delithiation results in poor cycle stability of tin-based anode materials, which becomes the major obstacle to their practical application. In this work, we fabricated three-dimensional (3D) porous bowl-shaped carbon cages interspersed with carbon coated Ni–Sn alloy nanoparticles (Ni3Sn2 and Ni3Sn4; 10–30 nm) by a freeze-drying method with self-assembled NaCl as a template followed by annealing. Both Ni3Sn2/C and Ni3Sn4/C exhibit excellent electrochemical performance as anode materials for lithium-ion batteries. In particular, the Ni3Sn4/C nanocomposites exhibit superior rate capability (735, 661, 622, 577, 496, and 377 mA h g−1 at 0.1, 0.2, 0.5, 1, 2, and 5 A g−1, respectively) and excellent cycling stability (568 mA h g−1 at 0.5 A g−1 for the second cycle and gradually increased to 732 mA h g−1 after 200 cycles). The superior electrochemical performance is attributed to the synergetic effect of Ni–Sn alloy nanoparticles and 3D porous bowl-shaped carbon networks. The uniformly embedded Ni–Sn alloy nanoparticles can effectively alleviate the absolute stress/strain and shorten the Li+ diffusion path, and Ni in the Ni–Sn alloy acts as a buffer to suppress the volume expansion. Moreover, the 3D bowl-shaped carbon networks with high conductivity can provide abundant space for volume expansion, suppress the agglomeration of Ni–Sn nanoparticles, ensure the structural integrity, and facilitate lithium-ion diffusion as well as electron transportation.

Three-dimensional porous carbon nanosheet networks anchored with Cu6Sn5@carbon as a high-performance anode material for lithium ion batteries

The poor cycling stability resulting from large volume change is the major obstacle to the application of tin-based anode materials. In this paper, three-dimensional porous carbon nanosheet networks anchored with Cu6Sn5@carbon nanoparticles (10–35 nm) as a high-performance anode for lithium ion batteries are synthesized via a self-assembly NaCl template-assisted in situ chemical vapor deposition strategy. The composite exhibits superior rate capability (523, 443, 395, 327, 281, and 203 mA h g−1 at 0.2, 0.5, 1, 2, 5, and 10 A g−1, respectively) and excellent cycling stability (396.8 mA h g−1 at 1 A g−1 for the first cycle and maintains 92.3% after 200 cycles). The superior performance is attributed to the unique architecture: inactive metal copper serves as a “buffer matrix” and relaxes the large volume change of the tin; a uniform distribution of nano-sized Cu6Sn5 makes the inevitable stress/strain small, meanwhile it provides a short path for lithium ion diffusion; onion-like carbon shells not only prevent the Cu6Sn5 nanoparticles from agglomerating and growing but also offer mechanical support to accommodate the stress associated with the volume change of tin upon cycling, thus alleviating pulverization; 3D porous carbon nanosheet networks ensure the mechanical integrity and facilitate lithium ion diffusion as well as electron transportation.

Template-assisted in situ confinement synthesis of nitrogen and oxygen co-doped 3D porous carbon network for high-performance sodium-ion battery anode

Non-graphitic carbons have shown great advantages as anodes for sodium ion batteries. However, they deliver an unsatisfactory capacity, especially at high rate, owing to the sluggish sodiation kinetics. In this work, we synthesized well-distributed nitrogen and oxygen co-doped three-dimensional ultrathin amorphous porous carbon network via a simple NaCl template-assisted in situ confinement pyrolysis strategy. The porous carbon network with oxygen-containing groups provides abundant room (surface area of 282.78 m2 g−1) for the storage of Na+ and good wettability for the sufficient contact of the active material and the electrolyte, the affluent pores and the large interlayer space offer smooth passage for the insertion of Na+ and the transportation of electrons, and high-content nitrogen (N: 12.44 at%) doping affords more defects and active sites for the redox capacitance reaction of Na+. When used as an anode for sodium-ion batteries, the as-prepared sample presents high reversible capacity (416 mA h g−1 at 0.1 A g−1 after 100 cycles), superior rate capability (213.8 mA h g−1 at 5 A g−1), and excellent cycling performance at a super-high rate (142 mA h g−1 at 10 A g−1 after 1000 cycles with capacity retention of 94%). This work provides a new strategy to effectively construct continuous porous carbon nanostructures with uniform dual heteroatom doping for high-performance sodium-ion battery anodes.

Morphological evolution of hollow NiCo2O4 microsphere and its high pseudocapacitance contribution for Li/Na-ion batteries Anode

Hollow urchin-like NiCo2O4 microspheres (∼3 μm) with a large specific surface area (158.57 m2 g−1) have been synthesized by a facile template-free hydrothermal method and a morphology evolution mechanism of “bundles-solid spheres-hollow urchin-like microspheres” was proposed. The hollow urchin-like structure appears when the hydrothermal time is increased to 8 h, which can be accelerated by the addition of excess urea. Benefiting from the unique three-dimensional (3D) hollow structure and the desired composition, the NiCo2O4 microspheres exhibit an excellent reversible specific capacity for lithium ion batteries (991 mA h g−1 after 50 cycles) and sodium ion batteries (322.3 mA h g−1 after 50 cycles). The unique 3D hollow structure offers enough space to alleviate volume expansion caused by the Li+/Na+ insertion/extraction, and the perfect electrical conductivity of spinel binary metal oxides facilitates the transport of ions and electrons. A high capacitance contribution of 90% was achieved for LIBs at 0.3 mV s−1, while the capacitance contributions for SIBs were only 36% at 0.3 mV s−1 and 73% even at 5 mV s−1, which indicates that a capacitive-controlled charge storage mechanism plays a dominant role in the Li+ storage of NiCo2O4 microspheres. This work has guiding significance in the preparation of electrode materials with high electrochemical performance.