Hierarchical void structured Si/PANi/C hybrid anode material for high-performance lithium-ion batteries

Material Choice and Structure Design of Flexible Battery Electrode

With the development of flexible electronics, the demand for flexibility is gradually put forward for its energy supply device, i.e., battery, to fit complex curved surfaces with good fatigue resistance and safety. As an important component of flexible batteries, flexible electrodes play a key role in the energy density, power density, and mechanical flexibility of batteries. Their large-scale commercial applications depend on the fulfillment of the commercial requirements and the fabrication methods of electrode materials. In this paper, the deformable electrode materials and structural design for flexible batteries are summarized, with the purpose of flexibility. The advantages and disadvantages of the application of various flexible materials (carbon nanotubes, graphene, MXene, carbon fiber/carbon fiber cloth, and conducting polymers) and flexible structures (buckling structure, helical structure, and kirigami structure) in flexible battery electrodes are discussed. In addition, the application scenarios of flexible batteries and the main challenges and future development of flexible electrode fabrication are also discussed, providing general guidance for the research of high-performance flexible electrodes.

Yolk-shell-structured Si@TiN nanoparticles for high-performance lithium-ion batteries

The huge volume expansion of over 300%, dreadful electrical conductivity and labile solid electrolyte interphase (SEI) are the principal reasons of the sluggish development of Si anodes for lithium-ion batteries (LIBs). Therefore, we propose, for the first time, that titanium nitride (TiN) be utilized as a coating layer to fabricate yolk–shell-structured Si@TiN nanoparticles. The design of the yolk–shell structure can reserve excrescent space for the volume expansion of Si electrodes, which helps to mitigate volumetric changes. Moreover, the TiN protecting layer is beneficial to the formation of a stable and flimsy SEI film, avoiding the excessive consumption of electrolytes. Finally, the ultrahigh conductivity (4 × 10⁴ S cm⁻¹) as well as the high mechanical modulus of TiN can significantly promote charge transfer and avoid the crushing of the SEI film caused by excessive local stress during reduplicative Li deposition/stripping. Accordingly, the Si@TiN composites show excellent electrochemical properties and suppressed volume expansion compared with pure silicon nanoparticles (Si NPs). Here, these yolk–shell-structured Si@TiN nanoparticles exhibit improved rate performance and excellent long cycling stability with 2047 mA h g⁻¹ at 1000 mA g⁻¹ after 180 cycles. This paradigm may provide a feasible engineering protocol to push the properties of Si anodes for next-generation LIBs.

Si@TiN composites show excellent electrochemical properties and suppressed volume expansion compared with pure silicon nanoparticles (Si NPs).

Flexible Porous Silicon/Carbon Fiber Anode for High-Performance Lithium-Ion Batteries

We demonstrate a cross−linked, 3D conductive network structure, porous silicon@carbon nanofiber (P−Si@CNF) anode by magnesium thermal reduction (MR) and the electrospinning methods. The P−Si thermally reduced from silica (SiO₂) preserved the monodisperse spheric morphology which can effectively achieve good dispersion in the carbon matrix. The mesoporous structure of P–Si and internal nanopores can effectively relieve the volume expansion to ensure the structure integrity, and its high specific surface area enhances the multi−position electrical contact with the carbon material to improve the conductivity. Additionally, the electrospun CNFs exhibited 3D conductive frameworks that provide pathways for rapid electron/ion diffusion. Through the structural design, key basic scientific problems such as electron/ion transport and the process of lithiation/delithiation can be solved to enhance the cyclic stability. As expected, the P−Si@CNFs showed a high capacity of 907.3 mAh g⁻¹ after 100 cycles at a current density of 100 mA g⁻¹ and excellent cycling performance, with 625.6 mAh g⁻¹ maintained even after 300 cycles. This work develops an alternative approach to solve the key problem of Si nanoparticles’ uneven dispersion in a carbon matrix.

Microsphere-Like SiO2 /MXene Hybrid Material Enabling High Performance Anode for Lithium Ion Batteries

To address the non-negligible volume expansion and the inherent poor electronic conductivity of silica (SiO₂ ) material, microsphere-like SiO₂ /MXene hybrid material is designed and successfully synthesized through the combination of the Stöber method and spray drying. The SiO₂ nanoparticles are firmly anchored on the laminated MXene by the bonding effect, which boosts the structural stability during the long-term cycling process. The MXene matrix not only possesses high elasticity to buffer the volume variation of SiO₂ nanoparticles, but also promotes the transfer of electrons and lithium ions. Moreover, the microsphere wrapped with ductile MXene film reduces the specific surface area, relieves the side reactions, and enhances the coulombic efficiency. Therefore, superior electrochemical performance including high reversible capacity, outstanding cycle stability, high coulombic efficiency, especially in the first cycle, excellent rate capability as well as high areal capacity are acquired for SiO₂ /MXene microspheres anode.