Surface terminations of two‐dimensional MXene (Ti3C2Tx) considerably impact its physicochemical properties. Commonly used etching methods usually introduce ‐F surface terminations or metallic impurities in MXene. We present a new molten‐salt‐assisted electrochemical etching method to synthesize fluorine‐free Ti3C2Cl2. Using electrons as reaction agents, cathode reduction and anode etching can be spatially isolated; thus, no metallics are present in the Ti3C2Cl2 product. The surface terminations can be in situ modified from −Cl to −O and/or −S, which considerably shortens the modification steps and enriches the variety of surface terminations. The obtained −O‐terminated Ti3C2Tx are excellent electrode materials for supercapacitors, exhibiting capacitances of 225 F g−1 at 1.0 Ag−1, good rate performance (91.1 % at 10 Ag−1), and excellent capacitance retention (100 % after 10000 charge/discharge cycles at 10 Ag−1), which is superior to multi‐layered Ti3C2Tx prepared by other etching methods. This is the first study to use a molten‐salt‐assisted electrochemical etching (MS‐E‐etching) method to synthesize Ti3C2Cl2 without metallic impurities. The Tx surface terminations could be in situ modified from −Cl to −O and/or −S in this one‐pot process. The obtained −O‐terminated Ti3C2Tx electrode exhibited a significant increase in capacity.