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Transition metal oxide (TMO) anodes show promising applications in energy storage due to the unique physical and chemical properties and high theoretical capacity to storage ions. Their practical usages are restricted by low intrinsic electronic conductivity, sluggish ionic diffusion, and large volume change during continuous cycling. In this work, we propose a strategy of selective solution-phase reduction on specific crystalline planes to generate the defect chemistry and thus improve the intrinsic electronic conductivity. Taking Co 3 O 4 electrode as a typical example, we prepared the structures with different exposed planes, which were then subjected to solution-phase reduction at room temperature. When used as the electrodes for lithium ion batteries, the optimized material possesses a high reversible capacity of 873.5 mAh g−1 at a current of 0.1 A g−1, even at a large current density of 5 A g−1, a remarkable discharge capacity of 569.1 mA h g−1 can still be achieved. The improved performance is attributed to the synergistic effects of the optimized amount of Co2+ species and oxygen vacancies. The current strategy can be extended to other TMO electrodes, paving an alternative way to optimize the electrochemical performance for different applications. Selective solution-phase reduction on specific exposed crystalline planes generates defect structures and thus improves the lithium storage properties in a given material. Image 1 • Exposed crystalline planes are selective reduced in solution. • Defect structures can be generated. • The optimized sample exhibits enhanced lithium storage properties. [ABSTRACT FROM AUTHOR]