The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li–O2 batteries L. Johnson, C. Li, Z. Liu, Y. Chen, S.A. Freunberger, P.C. Ashok, B.B. Praveen, K. Dholakia, JM. Tarascon, P.G. Bruce Nature Chemistry, 2014