Part of LTO's open-circuit voltage.

There are two flavours of anode lithium-titanate-oxide: $\mathrm{Li_{1-2}Ti_{2}O_4}$ and $\mathrm{Li_{4/3-7/3}Ti_{5/3}O_4}$. Compared to the first flavour, in the second flavour one-sixth of Titanium atoms in the lattice are replaced with Lithium atoms. $\mathrm{LiTi_{2}O_4}$ and $\mathrm{Li_{4/3}Ti_{5/3}O_4}$ correspond to 0% stoichiometry, i. e. there is always some Lithium in LTO anode, unlike in graphite which could be fully delithiated.

Lithium ions can occupy two or three distinct types of sites in the lattice: 8a and 16c, and 16d (the latter only in $\mathrm{Li_{4/3-7/3}Ti_{5/3}O_4}$).

Figure from [1]

Figure from [1]

"8a", "16c", "16d", and "32e" are Wyckoff positions, but could be considered more as mnemonics here. The numeric part of the position label indicates the relative proportionality of the positions in the structure: in the case of LTO, it's important to note that there are two times as many 16c sites as 8a sites.

Geometrically, each 8a site shares a face with four 16c sites (and since 8a sites are tetrahedra that have four faces, this means that 8a sites don't share faces with any other types of sites in LTO apart from 16c), but each 16c site shares a face with only two 8a sites. 16c sites don't share faces among themselves. Every distance between the 8a and 16c sites are identical.

LTO almost doesn't expand or contract upon lithiation or delithiation, unlike graphite, so Van der Waals forces don't affect the chemical potential of Lithium intercalation and therefore the shape of LTO's open-circuit voltage function. (However, using Lattice Gas Model to find the OCV of graphite produces acceptable results, too, despite Lattice Gas Model also ignores expansion and contraction of anode particles.)

Related:

References

[1] Monte-Carlo simulation combined with density functional theory to investigate the equilibrium thermodynamics of electrode materials: lithium titanates as model compounds