posted on 2019-04-05, 00:00authored byQianqian Li, Pengshan Du, Yifei Yuan, Wentao Yao, Zhongtao Ma, Bingkun Guo, Yingchun Lyu, Peng Wang, Hongtao Wang, Anmin Nie, Reza Shahbazian-Yassar, Jun Lu
Battery
materials, which store energy by combining mechanisms of
intercalation, conversion, and alloying, provide promisingly high
energy density but usually suffer from fast capacity decay due to
the drastic volume change upon cycling. Particularly, the significant
volume shrinkage upon mass (Li+, Na+, etc.)
extraction inevitably leads to the formation of pores in materials
and their final pulverization after cycling. It is necessary to explore
the failure mechanism of such battery materials from the microscopic
level in order to understand the evolution of porous structures. Here,
prototyped Sb2Se3 nanowires are targeted to
understand the structural failures during repetitive (de)sodiation,
which exhibits mainly alloying and conversion mechanisms. The fast
growing nanosized pores embedded in the nanowire during desodiation
are identified to be the key factor that weakens the mechanical strength
of the material and thus cause a rapid capacity decrease. To suppress
the pore development, we further limit the cutoff charge voltage in
a half-cell against Na below a critical value where the conversion
reaction of such a material system is yet happening, the result of
which demonstrates significantly improved battery performance with
well-maintained structural integrity. These findings may shed some
light on electrode failure investigation and rational design of advanced
electrode materials with long cycling life.