Carbon coating to suppress the reduction decomposition of electrolyte on the Li4Ti5O12 electrode

The lithium ion batteries using Li4Ti5O12 as the anode material are easily being inflated during charge and discharge, which, however, does not occur in the batteries using graphite as the anode material. The high reduction reactivity of electrolyte on the Li4Ti5O12 material may be the main reason. In this work, the reduction reactivities of electrolyte on the uncoated and carbon-coated Li4Ti5O12 electrodes are compared for the first time. The results show that the reduction decomposition of electrolyte does occur on the uncoated Li4Ti5O12 electrode at around 0.7 V, while it only takes place at the first cycle on the carbon-coated Li4Ti5O12 electrode. The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles from the electrolyte. A successive solid electrolyte interface (SEI) film is formed on the carbon layer during the formation process, which can prevent the further reduction decomposition of electrolyte at around 0.7 V. The impurity phases of rutile and anatase TiO2 do not influence the reduction reactivity of electrolyte. This work is not only important to understand the reduction decomposition mechanism of electrolyte on the Li4Ti5O12 electrode, but also provides an effective solution to suppress the reduction decomposition of electrolyte in the batteries.

► We analyze the reduction reactivity of electrolyte on uncoated and carbon-coated Li4Ti5O12 electrodes. ► The electrolyte shows much high reduction reactivity on the uncoated Li4Ti5O12 than carbon-coated Li4Ti5O12 composite electrodes. ► The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles and electrolyte. ► The carbon coating on the surface of Li4Ti5O12 particles is an effective solution to suppress the reduction decomposition of electrolyte on the Li4Ti5O12 electrode.