The
poor ionic conductivity of transition metal oxides (TMOs) is
a huge obstacle to their practical application as anodes for lithium-ion
batteries (LIBs). Although good performance can be harvested by constructing
nanostructures, some other foundmental issues including low tap density
and serious electrolyte consumption come along. Herein, inspired by
frogspawn, we propose a universal strategy of using lithium salts
to assemble TMO nanoparticles into large aggregates to improve their
Li+ conductivity. In such a frogspawn-like structure, lithium
salt networks can not only realize the rapid transmission of Li+ but also alleviate the volume change during the charging/discharging
process. When Li3PO4 is applied to assemble
iron oxides nanoparticles, aggregates with size over 1 μm and
tap density up to 1.33 g cm–3 can be obtained, which
even hasve an ionic conductivity up to 9.61 × 10–5 S cm–1. Fe3O4 was also introduced
through reduction to boost electron transfer. Consequently, this carbon-free
composite delivered a capacity up to 896 mA h g–1 even after 1000 cycles at 5 A g–1, which can also
be maintained under high mass loading. When using lithium salts such
as Li2SO4, Li2CO3, LiBO2, and LiCl, the corresponding composites also showed similar
performance. This strategy is also effective for TMOs such as NiO,
Co3O4, and ZnO, demonstrating the universality
of this frogspawn-inspired design.