  Ionic thermoelectricity in nanochannels has received increasing attention
because of its advantages such as high Seebeck coefficient and low cost.
However, most studies have focused on dilute simple electrolytes that neglect
the effects of finite ion sizes and short-range electrostatic correlation.
Here, we reveal a new thermoelectric mechanism arising from the coupling of ion
steric effect due to finite ion sizes and ion thermodiffusion in electric
double layers, using both theoretical and numerical methods. We show that this
mechanism can significantly enhance the thermoelectric response in nanoconfined
electrolytes, depending on the properties of electrolytes and nanochannels.
Compared to the previously known mechanisms, the new mechanism can increase the
Seebeck coefficient by 100\% or even one order of magnitude enhancement under
optimal conditions. Moreover, we demonstrate that the short-range electrostatic
correlation can help preserve the Seebeck coefficient enhancement in weaker
confinement or in more concentrated electrolytes.
