Li-ion batteries became essential for our daily life
Jul 06, 2021
Since 1990, Li-ion batteries became essential for our daily life, and the scope of their applications is currently expanding from mobile electronic devices to electric vehicles, power tools and stationary power grid storage. The ever-enlarging market of portable electronic products and the new demands of the transportation market and stationary storage require cells with enhanced energy density, power density, cyclability and safety. In short, to get better performance. These new needs have boosted research and optimization of new materials for Li-ion batteries.
Fig. 1. Number of scientific publications about LiFePO4 material in the last 40 years. Source: Scifinder Scholar™ 2007.
The aim of this work is to show the evolution of chemical preparative methods used to synthesize new electroactive materials or to ameliorate electrochemical performance of the existing ones, and to compare the improvement of performance achieved by the new
materials processing. This way, the synthesis methods of several electrodic materials for Liion batteries will be analyzed. Mainly cathode materials, such as layered oxides derived from LiCoO2 or LiMn2O4 spinel derivatives will be described. Olivine LiFePO4 phase, a material that, besides having the right voltage to present safety attributes is made of low cost and abundant elements, will be specially remarked because of its extraordinary importance in the last years (figure 1).
In recent years, nanoscience has irrupted strongly in the battery materials field. Not only the performance of previously known materials was improved significantly by nanodispersion and nanostructuring, but also new materials and electrochemical reactions have emerged. Thus, the fabrication of nanostructured electrodes has become one of the main goals in battery materials.
First, the small size and large surface area of nanomaterials provide greater contact area between the electrode material and the electrolyte. Second, the distance the Li ions have to diffuse across the electrode is shortened. Therefore, faster charge/discharge ability, that is, a higher rate capability, can be expected for nanostructured electrodes. For very small particles, the chemical potentials for lithium ions and electrons may be modified, resulting in a change of electrode potential. Moreover, the range of composition over which solid solutions exist is often more extensive for nanoparticles, and the strain associated with intercalation is often better accommodated. Furthermore, even new electrochemical reactions, such as conversion reactions for anodes have appeared in nanostructured electrodes. Thus, morphology and size of electrode materials have become a key factor for their performance and the synthesis processes have been evolved toward nanoarchitectured materials.
This chapter will provide an overview on most used synthesis methods from the beginning of Li-ion batteries major research up to the newest ones. Materials performance evolution due to new processing systems will be discussed.
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