For many years, mass production of lithium-ion batteries relied on graphite and copper as their anode. Over the years, researchers have been looking for alternatives that can overcome the limitations of these materials, including costly production and limited storage capacity (for example, silicon can store 10 times the energy, though it poses another set of problems).
Creating today's anodes is a laborious, multi-step process in which graphite is coated on copper foil. However, as Karl Kreder, a materials scientist at the University of Texas at Austin and new lead author, explains, doing so leads to inefficiencies in terms of manufacturing processes and the battery itself.
Kreder said: "So the active material (graphite) is coated on the top of the inert current collector (copper), which increases the volume of the system and the quality of the inactive material, by combining the current collector with the active material, a higher capacity Active materials, using fewer inactive current collection materials. "
Kreder and his team did this with a simplified manufacturing method that eliminated the tedious coating process. When tin is cast into blocks, tin can be added directly to the aluminum to form an alloy, which can then be rolled mechanically (relatively inexpensive and conventional metallurgical alloying processes) into nanostructured metal foils. The last step is to reduce the particles in the material, which is crucial.
Kreder explains: "Tin can form an alloy with lithium.Unfortunately, if tin is used or even micrometer-sized tin particles, tin breaks when cycled by volume expansion when it is alloyed with lithium, which means that if large Of the tin particles make the battery, which can only maintain dozens of charge and discharge cycles, but if the nano-sized tin particles are made, the particles will not split during the alloying. "
The researchers called the resulting material a cross-eutectic alloy (IdEA) anode, which they consider to be only one-quarter the thickness of traditional anode materials and weigh only half as much as traditional materials. They tested the anode material in a small lithium-ion battery, which was then charged and discharged to measure performance. They found that this anode had twice the power storage capacity of a traditional copper-graphite anode. Crede said: "The reason for doing so is very good, one of the elements is active, tin, the other is inert, aluminum." Aluminum to create a conductive matrix in which the tin is retained, aluminum provides Structure and electrical conductivity, while tin is alloying and de-alloying with lithium when the battery is cycled.
Arumugam Manthiram, director of the Texas Institute of Materials, one of the team's leaders, said: "It is exciting to be able to develop an inexpensive and scalable electrode nanomaterial manufacturing process, and our results show , A success of this material in terms of the performance required for the commercialization of lithium-ion batteries. "
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