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请看美国专利EXAMPLE 2
Preparation of Black Phosphorus-Carbon Composite
Commercially available Red Phosphorus powder (High Purity Chemicals, >99%, average size: 75 μm) and Carbon (Super P) were mixed. The composition of Red Phosphorus to Carbon was made to be 70 wt % to 30 wt %. Then, the mixture and stainless steel ball (diameter: ⅜″) were put into a hardened steel cylindrical vial (diameter: 5.5 cm, height: 9 cm) with a ball-to-powder ratio of 20:1, and the HEMM process was conducted with a rotation velocity of 600 times per minute under an Ar atmosphere in a glove box for 12 hours, thereby transforming the amorphous red phosphorus-carbon composite to crystalline orthorhombic black phosphorus-carbon composite.
FIG. 1 is X-ray diffraction patterns. FIG. 1 a is X-ray diffraction pattern of the amorphous red phosphorus which is a comparative example. FIG. 1 b is X-ray diffraction pattern showing that black phosphorus has been synthesized. FIG. 1 c is X-ray diffraction pattern showing that black phosphorus-carbon composite has been synthesized.
FIG. 2 is a graph showing the charge and discharge behavior at the first cycle of the lithium rechargeable battery using the black phosphorus-carbon composite of the example 2 and red phosphorus of the comparative example respectively as an anode active material.
As FIG. 2 shows, with the amorphous red phosphorus, it is possible to store lithium during the charge but it is impossible to eliminate lithium during the discharge. Further, the charge and discharge efficiency of the first cycle was below 5%. To the contrast, with the black phosphorus-carbon composite, repetitive charge and discharge of lithium at the first cycle is possible. Further, its charge and discharge efficiency at the first cycle was about 90%, which means that the black phosphorus is more suitable than any other conventional materials for anode material of the lithium rechargeable battery.
FIG. 3 is a differential capacity plot wherein the voltage is differentiated with the capacity for specific investigation of the charge and discharge behavior of the black phosphorus-carbon composite of the example 2 and red phosphorus of the comparative example at the first cycle of the battery.
FIG. 3 shows that LiP phase was formed at 0.78 V As the voltage potential becomes lower, Li 3 P was finally formed. Further, P phase was formed at 2 V. The specific reaction potential wherein the respective phases are formed can be different according to how to assemble the battery and what to use as an electrolyte.
FIG. 4 is a graph showing the charge and discharge cycle characteristic data of the two potential regions. One is the potential region (0.78˜2 V) which is from the potential wherein LiP phase is formed to the potential wherein P phase is formed and the other is the potential region (0˜2 V) which is from the potential wherein Li 3 P phase is formed to the potential wherein P phase is formed.
As FIG. 4 shows, in case of the potential range which is from 0.78 V wherein the LiP phase is formed to 2 V wherein the P phase is formed, very stable cycles of 100 cycles or more was obtained while maintaining such a large capacity of 600 mAh/g or more.
According to the invention, compared to the conventional method which is not easy and efficient to perform due to its high temperature and high pressure, the black phosphorus or black phosphorus-carbon composite can be easily and efficiently obtained from the red phosphorus or red phosphorus-carbon composite even at an ambient temperature and pressure.
Furthermore, the black phosphorus or black phosphorus-carbon composite have a good crystallinity, stability, electric conductivity and to this end are very suitable for an anode material of lithium rechargeable battery,
As well, the black phosphorus or black phosphorus-carbon composite is very helpful to obtain the mechanical stability of the lithium rechargeable battery and to improve the capacity and cycles since they make it possible to limit the potential and to this end to minimize the break of the anode materials which is due to the volume change of the anode materials occurring during the charge and discharge of the lithium rechargeable battery. Moreover, excellent cyclic performance can be obtained, by carefully controlling a voltage range, which also prohibits the formation of metallic lithium.
Due to said characteristics of the black phosphorus or black phosphorus-carbon composite, the black phosphorus or black phosphorus-carbon composite also can be applied to other kinds of rechargeable batteries such as Magnesium rechargeable batteries etc. as well as the lithium rechargeable battery and makes it possible to obtain improved capacities and long-term cycles also in such other kinds of rechargeable batteries.
