This mini-review discusses the recent trends in electrode materials for Li-ion batteries. Elemental doping and coatings have modified many of the commonly used electrode materials, which are used either as anode or cathode materials. This has led to the high diffusivity of Li ions, ionic mobility and conductivity apart from specific capacity.
Lithium metal was used as a negative electrode in LiClO 4, LiBF 4, LiBr, LiI, or LiAlCl 4 dissolved in organic solvents. Positive-electrode materials were found by trial-and-error investigations of organic and inorganic materials in the 1960s.
The lithium-ion battery generates a voltage of more than 3.5 V by a combination of a cathode material and carbonaceous anode material, in which the lithium ion reversibly inserts and extracts. Such electrochemical reaction proceeds at a potential of 4 V vs. Li/Li + electrode for cathode and ca. 0 V for anode.
The anode and cathode electrodes play a crucial role in temporarily binding and releasing lithium ions, and their chemical characteristics and compositions significantly impact the properties of a lithium-ion cell, including energy density and capacity, among others.
Lithium-ion batteries consist of two lithium insertion materials, one for the negative electrode and a different one for the positive electrode in an electrochemical cell. Fig. 1 depicts the concept of cell operation in a simple manner . This combination of two lithium insertion materials gives the basic function of lithium-ion batteries.
It is an ideal insertion material for long-life lithium-ion batteries, with about 175 mAh g −1 of rechargeable capacity and extremely flat operating voltage of 1.55 V versus lithium. LiFePO 4 in Fig. 3 (d) is thermally quite stable even when all of lithium ions are extracted from it .