Na(+)/H(+) antiporter that extrudes sodium in exchange for external protons. Can also transport lithium. Optimum pH is 8.5-9.0 for sodium transport and 8.5 for lithium transport. Na(+)/H(+) antiporter activity is detected between pH 6.5 and 9.5, whereas Li(+)/H(+) antiporter activity is detected only above pH 7.5. Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family.