We have synthesized novel mesoporous titanate nanosheets by reacting titanium isopropoxide (TTIP) with formic acid. The porous nanosheets were characterized as a new titanate structure with intercalation of formate groups and protons, in the form of HCOOH-intercalated titanate. Most interestingly, TiO2-B, a well-known but unusual titanium dioxide phase with great potential in applications in Li-ion batteries, was obtained after the nanosheets were heated above 250 °C. Mesoporous nanosheets of HCOOH- intercalated titanate, titanium dioxide with mostly TiO2-B and titanium dioxide with traces of TiO2-B were obtained by heating the as prepared mesoporous titanate nanosheets at 200, 300, and 550 °C, respectively. The method reported here is the first to utilize the sol-gel process to synthesize TiO2-B. In addition, different anodes were made from HCOOH-intercalated titanate and titanium dioxide with different ratios of TiO2-B to examine the performance of the charging/discharging capacity in Li ion intercalation. The discharging capacity of titanium dioxide with major TiO2-B can reach 357 mA h/g at the first charging cycle and is highest among TiO2-B reports so far.