def graphite_volume_change_Ai2020(sto):
    """
    Graphite particle volume change as a function of stochiometry [1, 2].

    References
    ----------
     .. [1] > Ai, W., Kraft, L., Sturm, J., Jossen, A., & Wu, B. (2020).
     Electrochemical Thermal-Mechanical Modelling of Stress Inhomogeneity in
     Lithium-Ion Pouch Cells. Journal of The Electrochemical Society, 167(1), 013512
      DOI: 10.1149/2.0122001JES.
     .. [2] > Rieger, B., Erhard, S. V., Rumpf, K., & Jossen, A. (2016).
     A new method to model the thickness change of a commercial pouch cell
     during discharge. Journal of The Electrochemical Society, 163(8), A1566-A1575.

    Parameters
    ----------
    sto: :class:`pybamm.Symbol`
        Electrode stochiometry, dimensionless
        should be R-averaged particle concentration
    Returns
    -------
    t_change:class:`pybamm.Symbol`
        volume change, dimensionless, normalised by particle volume
    """
    p1 = 145.907
    p2 = -681.229
    p3 = 1334.442
    p4 = -1415.710
    p5 = 873.906
    p6 = -312.528
    p7 = 60.641
    p8 = -5.706
    p9 = 0.386
    p10 = -4.966e-05
    t_change = (
        p1 * sto ** 9
        + p2 * sto ** 8
        + p3 * sto ** 7
        + p4 * sto ** 6
        + p5 * sto ** 5
        + p6 * sto ** 4
        + p7 * sto ** 3
        + p8 * sto ** 2
        + p9 * sto
        + p10
    )
    return t_change