## 1 Introduction  
Lithium titanate (Li\({}_{4}\)Ti\({}_{5}\)O\({}_{12}\)), which is usually referred to as LTO, has become a promising candidate for anode material that could substitute for carbon. LTO operates on a stable voltage of \(\approx\)1.5 V vs. Li+/Li, which avoid electrolyte decomposition and the safety issues presented by the use of carbon [1, 2, 3] that tends to form lithium dendrite and causes the occurrence of a surface passivation film. The surface passivation film could cause an initial loss in capacity, safety issues, loss of critical electrode performance, and cell failure [4, 5]. In the midst of many promising candidates for anodes such as Si, SiO\({}_{x}\), SiO\({}_{2}\), SnO\({}_{2}\), Fe\({}_{2}\)O\({}_{3}\), Co\({}_{3}\)O\({}_{4}\), etc. [6, 7, 8, 9, 10, 11, 12, 13], LTO has superior structural stability with no structural or volume changes during the lithiation/de-lithiation process. Hence, LTO is classified as a zero-strain material that has 175 mAh/g of theoretical capacity [14, 15, 16].  
As a lithium-intercalation material, the high crystallinity of LTO is a key for great capacity and cyclability [17]. [PERSON] et al. 2013 studied the effect of crystallinity on the electrochemical performance of LTO nanoparticles (NPs) in half-cells [18]. The results showed that the high crystallinity of LTO NPs gives them the highest rating for rate ability and long-term cyclability [18].  
The many different techniques studied for the synthesis of LTO have included solid-state reactions [19; 20; 21], sol-gel methods [22; 23; 24; 25], microwave-assisted synthesis [26; 27], spray pyrolysis [28; 29], and hydrothermal methods [30; 31]. The sol-gel methods are used to obtain particles of LTO under low temperatures [32]. In order to achieve highly crystalline LTO, [PERSON] et al. (2015) and [PERSON] et al. (2008) used a molten salt method [33; 34]. However, the finished product required washing to eliminate the salt, and hence, a large amount of lithium salt wastewater had to be discarded into the environment, which makes this process unattractive for adaptation to large-scale production. Other methods used in attempts to synthesize highly crystalline LTO have included a novel pulse flow supercritical reactor that was studied by [PERSON] et al. (2013) [17]. [PERSON] et al. (2013) used a hydrothermal method [18]. A novel continuous-flow hydrothermal method under supercritical conditions was proposed by [PERSON] et al. (2012) [35]. Nevertheless, these methods require high levels of temperature and pressure, which expends a large amount of energy.  
An alternative way to improve the crystallinity of a material is by adding a small amount of salt during synthesis, which is referred to as a salt-assisted process. The addition of salt (NaCl, KCl) has succeeded in assisting in the crystal formation of materials such as ZnO, ZnFe\({}_{2}\)O\({}_{4}\), and strontium ferrite [36; 37; 38]. Our previous investigation focused on the effect of NaCl addition on the synthesis of fluorine-doped tin oxide for use in solar cells [39]. However, salt-assisted synthesis has never been demonstrated in the production of LTO material. In the present experiment, we proposed a systematic synthesis of highly crystalline LTO using a salt-assisted, solid-state reaction (various additions of NaCl) to increase the crystallinity and improve the specific discharge capacities of LiFePO\({}_{4}\)(LFP)/LTO battery electrochemical performance. An LFP/LTO battery was selected as the cell design because it is known for its fast charging feature, superior rate ability, and cyclability at high rates. Since it has zero cobalt, it is thermally stable with phenomenal safety features that are crucial and applicable for electric vehicle applications [40; 41; 42].