posted on 2022-01-28, 21:03authored byMoo Dong Lee, Geun Jun Lee, Inho Nam, Muhammad A. Abbas, Jin Ho Bang
TiO2 offers several advantages over graphite as an anode
material for Li-ion batteries (LIBs) but suffers from low electrical
conductivity and Li-diffusion issues. Control over defect chemistry
has proven to be an effective strategy to overcome these issues. However,
defect engineering has primarily been focused on oxygen vacancies
(VO). The role of another intrinsic TiO2 vacancy
[i.e., titanium vacancies (VTi)] with regard to the Li+ storage behavior of TiO2 has largely evaded attention.
Hence, a comparison of VO- and VTi-defective
TiO2 can provide valuable insight into how these two types
of defects affect Li+ storage behavior. To eliminate other
factors that may also affect the Li+ storage behavior of
TiO2, we carefully devised synthesis protocols to prepare
TiO2 with either VO (n-TiO2) or VTi (p-TiO2). Both TiO2 materials were
verified to have a very similar morphology, surface area, and crystal
structure. Although VO provided additional sites that improved
the capacity at low C-rates, the benefit obtained from over-lithiation
turned out to be detrimental to cycling stability. Unlike VO, VTi could not serve as an additional lithium reservoir
but could significantly improve the rate performance of TiO2. More importantly, the presence of VTi prevented over-lithiation,
significantly improving the cycling stability of TiO2.
We believe that these new insights could help guide the development
of high-performance TiO2 for LIB applications.