Scientists have been hoping to expand the power storage capacity of lithium-ion batteries by converting graphite anode to lithium or silicon, where users will no longer have to worry about the battery of smartphones, nor the distance between charging stations when driving electric vehicles. Now, American scientists have discovered another alternative material that possesses reasonably well efficiency: phosphorus.
The cathode (positive electrode) of lithium batteries is formed by lithium and transition metals such as cobalt, nickel, and manganese, where the anode (negative electrode) materials are formed with graphite and copper, and lithium-ion will travel between the two electrodes and electrolytes, with the anode materials affecting the battery capacity the most. Although graphite contains high stability and durability in power storage, where the battery performance remains the same after 1,000 cycles of charging and discharging, its low capacity of theoretical power storage is becoming more difficult in satisfying the needs of modern people.
Numerous scientists have placed their hopes on lithium and silicon for elevating battery capacity, as they believe that these materials are able to increase the power storage capacity, with apparent improvement in the density of energy. The result of their experiments has indicated a relatively strong performance, but the main question still remains: are there any other options available? Argonne National Laboratory recently discovered that the application of phosphorus has a very high potential in terms of its power storage capacity that is even higher than that of graphite, which is the same as silicon, where the theoretical power storage capacity is 10 times that of graphite.
However, phosphorus is the same as silicon and lithium materials, which expands during the charging process of the battery that will damage the durability and lifespan of the materials, though the research team believes that it remains to be a study worth challenging for. Gui-Liang Xu, chemist of the Argonne National Laboratory, commented that phosphorus has a high absorption of energy, and the test has revealed that the initial coulombic efficiency of phosphorus anode exceeded 90%, which means that not much side reactions were derived from the anode and electrolytes.
The research team milled black phosphorus and conductive carbon into micron particles and produced a pristine composite anode, where the final result of the experiment also conformed to the anticipation of the team. As pointed out by the study, the initial coulombic efficiency of the new anode is as high as 91%, with a specific density (energy density) of roughly 2,500 mAhm, and the scientists also installed the pristine anode on a NMC battery subsequently.
Black phosphorus is transformed from white phosphorous under high temperature and pressure, and is the allotropy of phosphorous that possesses the largest density, the most stability in thermodynamics, and the least active substance. Black phosphorous consists of the same lamellar structure and conductivity as graphite, and is also a highly anticipated two-dimensional semiconductor material that can be applied on transistors and optoelectronic equipment.
The stable performance and the extensive application range of black phosphorus has prompted the research team to test red phosphorous that is cheaper yet possesses lower conductivity, after taking into account the budget and the cost of commercialization, though the Argonne National Laboratory has yet to announce the test result of red phosphorous anode, and only commented on its advantage of stability and the high initial coulombic efficiency.
The research team is looking at mass producing red phosphorus anode as the next target, and hopes to implement industry-academia-research collaboration in order to expand on the production scale of materials, as well as facilitate the progress of the final commercialization.
(Cover photo source: shutterstock)