Tunable lithium storage properties of metal lithium titanates by stoichiometric modulation

• Electrochemical behaviors in MLi2Ti6O14 (MLTO) are able to be finely modulated.
• MLTOs can be energetically stable even various M species coexist in single crystal.
• Na for M species decreases working potential, while Sr increases capacity.
• Na, Sr atoms affect electron density of Ti atom, and change working potential.
• Any of precise working potential can be obtained by simply adjusting Na/Sr ratio.

A simple stoichiometric modulation of Na2 − 2xSrxLi2Ti6O14 was developed to achieve tunable electrochemical properties of the material. The concept was confirmed experimentally and theoretically using density functional theory (DFT) calculations. Both the operating potential and the amount of reversibly intercalated lithium ions were manipulated by simply changing the Na/Sr ratio. These unique characteristics originated from a gradual change in the electron density on the Ti atoms and the extra lithium insertion sites at SrLi2Ti6O14. As a promising anode material for lithium-ion batteries, Na2 − 2xSrxLi2Ti6O14 and its tunable electrochemical properties have significant importance in terms of the development of tailored electrodes with desirable electrochemical performance.