1. Field
The present teachings relate to an anode active material, an anode including the anode active material, a method of manufacturing the anode, and a lithium battery including the anode.
2. Description of the Related Art
Lithium batteries are widely used as a power source for portable electronic devices. Lithium batteries use an organic electrolyte and have twice the discharge voltage of a conventional alkali battery. Accordingly, lithium batteries also have a higher energy density.
As anode active materials for lithium batteries, lithium-transition metal oxides, such as LiCoO2, LiMn2O4, LiNi1-xCOxO2 (0≦x≦1), which have a structure that allows for the reversible intercalation of lithium ions, are mainly used. Carbonaceous materials in various forms, such as artificial graphite, natural graphite, and hard carbon, which allow for the reversible intercalation of lithium ions, have also been used as anode active materials. However, due to poor stability and capacity reductions, which occur with the use of these carbonaceous materials, non-carbonaceous materials, such as silicon (Si), are being studied for use as anode active materials.
Such non-carbonaceous materials exhibit a capacity that is at least ten times that of graphite. However, the cycle lifetime characteristics thereof deteriorate, due to volumetric changes that occur during charging and discharging. In addition, non-carbonaceous active materials, such as Si, have a low electrical conductivity and obstruct the flow of electrons, thereby lowering cell performance.
In order to address the problem of poor cycle lifetime characteristics, which occur as the non-carbonaceous materials are fractured due to the volumetric changes, and/or other problems, research is currently being conducted into a binder that can enhance the integrity of a anode active material. The use of carboxymethyl cellulose (CMC)-based binders, instead of a conventional polyvinylidene fluoride binder, has been reported (Electrochem. Commun. 9, 2801 (2007), Electrochem. Solid-state Lett. 10, A17 (2007), Electrochem. Solid-state Lett. 11, A76 (2008), Electrochem. Solid-state Lett. 11, A101 (2008), J. Electrochem. Soc. 155, A158 (2008)).
CMC-based binders are known to improve the cycle lifetime characteristics of non-carbonaceous anode active materials. However, along with an increasing demand for improved cycle lifetime characteristics, research is continuing into a binder that can further improve the cycle lifetime characteristics of anode active materials.