Boron carbide suffers from a loss of strength and toughness when subjected to high shear stresses due to amorphization. Here, we report that a small amount of Si doping (~1 atomic %) leads to a substantial decrease in stress-induced amorphization due to a noticeable change of the deformation mechanisms in boron carbide. In the undoped boron carbide, the Berkovich indentation–induced quasi-plasticity is dominated by amorphization and microcracking along the amorphous shear bands. This mechanism resulted in long, distinct, and single-variant shear faults. In contrast, substantial fragmentation with limited amorphization was activated in the Si-doped boron carbide, manifested by the short, diffuse, and multivariant shear faults. Microcracking via fragmentation competed with and subsequently mitigated amorphization. This work highlights the important roles that solute atoms play on the structural stability of boron carbide and opens up new avenues to tune deformation mechanisms of ceramics via doping.

In-operando study coupled with voltage/current profiles are presented in order to unveil lithium insertion processes into 3D porous carbon nanotube (CNT) structures whose surfaces were altered to have lithiophobic, lithiophilic, and hybridized lithiophobic/philic characteristics using graphitic surfaces with/without carboxyl/hydroxyl groups. We found the lithiophobic graphitic surfaces hindered lithium insertion into the scaffold despite the high conductivity of CNT. The lithiophilic surface caused another problem of lithium deposition on the outer surface of the electrode, clogging pores and engendering dendrites. Conversely, in the hybridized CNT, lithiophilic trenches partially created on the pristine CNT allowed for uniform lithium deposition into the pores by simultaneously improved lithium attraction and charge transfer, reaching a high areal capacity of 16 mAh cm–2 even with a current density of 8 mA cm–2 without noticeable dendrite formation and volume expansion. Our hybridization approach provides valuable insight to realize a high-energy-density anode by uniformly impregnating lithium into porous media.

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Graphitic carbon materials are commonly used for storing Li ions owing to outstanding electrochemical stability and electrical conductivity, and their 3D porous structures are promising in achieving high capacity anodes...