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Tin dioxide (SnO 2) is a promising anode material for lithium-ion and sodium-ion batteries. However, the huge volume expansion during cycling makes it far away from practical application. Herein, we report a template-free "heterogeneous carbonization" strategy for fabricating SnO 2 /carbon/void/carbon nanofibers (SCVC) compound membrane with finite spatial domain in carbon matrix as buffer layer for volume changes of SnO 2. Reduced graphene oxide (rGO) is also imported into the SCVC membrane, acting as conductive binders to construct a free-standing SCVC-rGO electrode with exceptionally conductive network. The resultant SCVC-rGO anodes in lithium/sodium-ion batteries could deliver excellent electrochemical performances of higher reversible capacity, longer lifespan and superior rate capability. As lithium-ion battery anode, the SCVC-rGO electrode shows specific capacities of 950 mA h g−1 after 400 cycles at a current of 0.5 A g−1, and 824 mA h g−1 after 650 cycles at 1 A g−1. In sodium-ion batteries, the SCVC-rGO electrode gives rise to the specific capacity of 407 mA h g−1 after 2000 cycles at the current of 1 A g−1 with exceptional capacity retention. SnO 2 /carbon/void/carbon nanofibers membrane combined with reduced graphene oxide (SCVC-rGO) is constructed by a template free, one-step heterogeneous carbonization strategy. The internal void formed in situ in SnO 2 /C can be used as confined space to accommodate its volume expansion, while the residual ultrathin carbon layer on SnO 2 nanocrystals can prevent their amalgamation and recrystallization. The SCVC-rGO anodes exhibit excellent cycling stability and rate capability in LIBs and SIBs. [Display omitted] • One-step strategy of heterogenous carbonization to in-situ form buffering voids. • Based on the different carbon yields from various precursors and without the help of templates and corrosives. • Internal voids and residual ultrathin carbon layer ensure the complete reversibility of electrochemical reactions. • Excellent cycling stability and rate capability in half cells of LIBs and SIBs have been achieved. [ABSTRACT FROM AUTHOR]

As a promising anode for potassium-ion batteries (PIBs), graphite has drawn great attention due to easy availability, low cost and formation of potassium-based intercalation compound. However, poor cyclic and rate performances due to severe structural degradation limit the practical application of graphite anode. Herein, a low cost mildly-expanded graphite (MEG) with adjustable interlayer lattice distance is synthesized through a wet chemical oxidation route. As anode for PIBs, the MEG exhibited stable intercalation/deintercalation plateaus, outstanding cyclic stability and rate performance. By optimizing the mass ratio between graphite and potassium permanganate oxidant, the MEG anode retaining long-range-ordered domains of graphite delivers a capacity of 88 mAh/g at 1500 mA/g and a capacity retention of 72.3% after 200 cycles at 100 mA/g. The potassium ion full cell assembled with MEGs anode exhibites high energy density and outstanding cyclic stability. Our results demonstrate a promising graphite-based anode for PIBs and provide guidance for the designing of novel carbonic electrodes for PIBs. Image 1 [ABSTRACT FROM AUTHOR]

Metallic Na possesses high specific capacity and lowest electrochemical potential of all possible candidates, and therefore being regarded as one of the most promising anode materials for Na batteries. Nevertheless, unstable solid electrolyte interface, infinite volume change and uncontrollable dendritic Na growth upon repeated Na plating/stripping processes lead to low Coulombic efficiency, poor cyclability and safety concerns of Na metal anode. Herein, a three-dimensional carbon felt host was employed to suppress Na dendrite growth, thus achieving highly reversible Na plating/stripping process. The interstitial space inside the carbon felt framework accommodates Na deposition, and the plentiful active sites guide homogenous Na nucleation and growth without dendrite formation. As a result, the carbon felt exhibits stable cycling lifetime for 1100 h and 350 h at 1 mA cm−2 and 2 mA cm−2 respectively, which are 5.6 and 3.9 times longer than that of Al foil. Moreover, the carbon felt possesses high average Coulombic efficiency of ∼99.3% for 500 cycles at 0.5 mA cm−2. When paired with Na 2/3 Ni 1/3 Mn 2/3 O 2 cathode, the full cell delivers a high capacity retention of 95.1% over 150 cycles. Image 1 [ABSTRACT FROM AUTHOR]

Silicon (Si) has been regarded as one of the most attractive anode materials for the next generation lithium-ion batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, the architecture of Si-based anode material still needs to be well designed to overcome the structure degradation and instability of the solid-electrolyte interphase caused by a large volume change during cycling. Here we report the electrochemical performances of a novel binder-free Si/carbon composite film consisting of alternatively stacked Si-porous carbon layers and graphene layers, which is synthesized by electrostatic spray deposition followed by heat treatment. For this composite film, Si nanoparticles are embedded in the porous carbon layer composed of nitrogen-doped carbon framework, carbon black and carbon nanotubes. And the combined Si-porous carbon layer is further sandwiched by flexible and conductive graphene sheets. The multilayered Si-porous carbon/graphene electrode shows a maximum reversible capacity of 1020 mAh g −1 with 75% capacity retention after 100 cycles and a good rate capability on the basis of the total electrode weight. The excellent electrochemical performances are attributed to the fact that the layer-by-layer porous carbon matrix can accommodate the volume change of Si particles and maintain the structural and electrical integrities. [ABSTRACT FROM AUTHOR]