Skypower Solutions Corp.

Cathode Materials

Cathode materials are the most costly part of lithium ion cell composition. Cathode materials are found in different crystalline structures like layered structure, Spinel structure, Olivine structure, and recently introduced a series of Sky Power Solutions ‘ synthesized cathode structures based on the hexagonal layout foundation. Sky Power Solutions has diligently researched the cathode material in our compound due to the typically poor diffusion of Lithium ion through the layered structure, poor conductivity and stability of the crystal structure. By increasing the thermal stability, we have enhanced the overall performance of the Lithium Polymer battery cell as a whole.

Layered Structure

In 1990, Sony (Japan) introduced the lithium ion battery. Sony used
LiCoO2 as cathode material. This material is expensive, unsafe and its
use for some military applications has been discontinued . A considerable investment has been made in this battery technology that utilizes LiCoO2 with an operating voltage range of 4.2 to 2.75V. However, during operation at high temperature, LiCoO2 shows an exothermic reaction which eventually generates loose oxygen and can cause fire hazards.

Another promising material is LiNiO2. However, phase pure oxide is
difficult to produce resulting in poor or low discharge capacity around 140-150 mAh/g. It has capacity degradation also due to the formation of NiO2 during intercalation and deintercalation of lithium ion. Toxicity and high cost are other issues for the cobalt and nickel based layered oxides.

New LiMn1/3Co1/3Ni1/3O2 layered structure is being used in lithium ion
batteries because of its safety and non-toxic nature. The disadvantage
is that the structure of cathode material is destroyed once discharged
below 2.5V. The cost of the material is also higher than LiCoO2 due to the difficulties of process control.

Olivine Structure

Lithium iron phosphate, LiFePO4, is widely used and under testing as
it has lower cost is safer . The oxygen is strongly bonded in phosphate
form and thus avoids formation of loose oxygen. The disadvantage of this
material is that it has a low operating voltage do to thermodynamic issues, which results in a compound restricted within an operating range of 3.4V to 2.9V and nominal voltage is of only 3.2V.

Spinel Structure

Recently, manganese based oxides such as LiMn2O4 spinel and LiMnO2
layered oxides have been studied extensively. The reason being manganese is abundant in nature, less expensive and non-toxic. The
problem encountered using manganese was significant capacity fading
due to dissolution of manganese in the form of Mn+2.

Sky Power Solutions Structure

These crystal structure models were examined as [√3X√3] R30°, by Sky
Power Solutions. In Figure 3, it is observed that all transition metals
occupy the same layer in hexagonal structures, and in layered structure
they occupy alternative layers. In Sky Power Solutions structure some
transition metals are replaced by lithium which in turn enhances the
power density significantly. However, Sky Power Solutions’ mixed
oxide synthesis become difficult when starting materials are not mixed
homogeneously. An innovative synthesis process is required for large
scale production of Sky Power Solutions’ cathode material, which is
currently time consuming and expensive, requiring more development to
reduce the price and increase efficiency.

Figure 3: a) Sky Power Solutions Structure, b) Alternating Layers

Table 1: Comparative Electrochemical Properties