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The recently explored FeNb11O29 is an advanced anode material for lithium‐ion batteries, owing to its high specific capacity and safety. However, it suffers from poor rate capability. To tackle this issue, a crystal structure modification is employed. Defective FeNb11O29 (FeNb11O27.9) is fabricated by using a one‐step solid‐state reaction method in N2. FeNb11O27.9 has the same orthorhombic shear ReO3 crystal structure (Amma space group) as FeNb11O29, but a larger unit‐cell volume and 3.8 % O2− vacancies (vs. all O2− ions), which improve the Li+‐ion diffusion coefficient by a factor of 88.3 %. The contained Nb4+ ions with free 4d electrons significantly increase the electronic conductivity by three orders of magnitude. Consequently, FeNb11O27.9 shows improved pseudocapacitive behavior and electrochemical properties. In comparison with FeNb11O29, FeNb11O27.9 exhibits a higher reversible capacity of 270 mAh g−1 with a higher first‐cycle coulombic efficiency of 90.6 % at 0.1 C. At 10 C, FeNb11O27.9 still retains a high capacity of 145 mAh g−1 with low capacity loss of 6.9 % after 200 cycles, in contrast to the values of 99 mAh g−1 and 11.1 % obtained for FeNb11O29.

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