In the article [Phys. Rev. B 77, 075119 (2008)], effective magnetic moments $p_{\mathrm{eff}}$ per Co site have been determined from magnetic susceptibility measurements for a series of ${\mathrm{Li}}_x{\mathrm{CoO}}_2$ samples. The nominal Li content $x$ (ranging theoretically from 1 to 0) determines the concentration of ${\mathrm{Co}}^{3+}$ ($x$) and ${\mathrm{Co}}^{4+}$ ($1-x$) that occupy the Co sites. Assuming that the ${\mathrm{Co}}^{3+}$ species is diamagnetic, the effective magnetic moment $p_{\mathrm{eff}}$ per ${\mathrm{Co}}^{4+}$ ion has been calculated from the experimentally determined effective magnetic moment $p_{\mathrm{eff}}$ per Co site and the nominal ${\mathrm{Co}}^{4+}$ concentration in the cited publication [Phys. Rev. B 77, 075119 (2008)] by assuming a purely linear relation between the effective magnetic moments and the concentrations. From the viewpoint of this comment's author, this linear approach is not valid and the linear effective magnetic moments $p_{\mathrm{eff}}$ utilized in the formulas in the cited article should be replaced by their squared values $p_{\mathrm{eff}}^2$. This comment provides the correct formulas for the calculations aimed to be performed in [Phys. Rev. B 77, 075119 (2008)] and recalculates the published values. Since for low ${\mathrm{Co}}^{4+}$ concentrations a high-spin species is discussed to exist in ${\mathrm{Li}}_x{\mathrm{CoO}}_2$ in numerous publications, correct handling of effective magnetic moments is of general interest in this discipline of research.

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