Optimizing performance of lithium­ion battery by nano­silicon addition mixed in LI4TI5O12 anode made using mechanochemical­hydrothermal method

Abstract

Lithium Titanate (Li4Ti5O12 or LTO) is one of the best candidates to replace graphite as anode material in the lithium-ion battery (LIB), due to unwanted solid electrolyte interphase (SEI) layer formation that consumes Li+ ion and reduces LIB performance and may cause thermal run-away. The ability of LTO to avoid SEI formation and undergo zero-strain during intercalation makes LTO has excellent safety during application. However, the spinel lithium titanate has the low theoretical capacity and poor electronic conductivity. This less conductivity brings limitation to its application. The sol-gel method and combining the LTO with Si that possesses a high theoretical capacity are the key factor to overcome the LTO disadvantages. To attain its high power, safety factor and low-cost fabrication properties, hydrothermal-mechanochemical treatment were used in sol-gel synthesis method in order to outgrowth (Li4Ti5O12)nanostructure. Then, the 5 %, 10 %, and 15 % weight ratio percentage of silicon nano-particle were added into electrode composite in order to enhance the capacity of lithium titanate anode. All samples were characterized using XRD, SEM and TEM. The active anode material LTO/Si nano was coated and prepared into coin cell battery. The assembled coin half-cell used lithium metal foil as the counter electrode. The battery performance was tested using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and charge-discharge (CD).The XRD results showed that the obtained compounds of lithium titanate (Li4Ti5O12) crystalline spinel and the impurities of TiO2 rutile. The SEM micrograph results showed almost uniform morphological structures as agglomerates in most of the samples. While, the TEM image of Si nano had a crystalline phase with the particle size less than 100 mm. However, the presence of unwanted SiOx layer was not clearly observed. Addition of Si-nanoparticle could increase the specific capacity to above the LTO theoretical capacity, however, the formation of SiOx insulating layer is predicted to be the main hindrance that reduces the effectiveness of addition of Si nanoparticle to the present LTO compound. The hydrothermal treatment of the sample could enhance the performance of nano-composite LTO/Si anode. Based on CD results, the obtained LTO/Si compound possesses the discharge capability up to 12 C.The CV and CD results showed the optimum percentage of 10 % wt. Si and best capacity of the sample was obtained at 229.72 mAh/g