a Japanese research team has improved design silicon anodes that replace graphite in Lithium ion batteries To improve its useful life. with the anode incorporation silicon from U.S polymer binder It consists of a specific polymer Significantly improves its structural stability. This ensures that batteries made with anodes of this material last longer, and are therefore viable to meet the energy needs of the Electric cars and other appliances.
Lithium-ion batteries are currently the most widely used in both portable devices and high energy density applications, such as electric vehicles. Its characteristics are those that best incorporate the minimum standards necessary to be technically and economically viable. They meet the requirements of safety, width Max power density Which is limited to the final weight and battery size and volume life cycle High. Finally, they present High rates of reuse and recyclingall of this at the lowest possible cost.
however, Its limits are clearEspecially with its use in electric vehicles that require greater durability, energy density and longevity. This is why many research teams are looking for alternative materials to use in these batteries. One of them is silicon, which will replace the graphite that forms the anode structure. The silicon It is a very abundant material and therefore much cheaper and has a higher theoretical discharge capacity than graphite.
Silicon has the ability to Significantly increases the energy density of batteries. Its capacitance is an order of magnitude greater than that of graphite, which is currently used to create the anode structure. at the cell level, Energy density can almost doubleproviding clear benefits in the autonomy of electric vehicles.
However, silicon anodes also have some drawbacks. The problem that arises when using silicon as the anode material is high degradation, resulting in poor battery life. Specifically, repeated charging and discharging cause the silicon molecules to expand and disintegrate, forming a thick solid interface (SEI) between the electrolyte and the anode. This SEI limits the movement of lithium ions between the electrodes, which in turn limits the battery’s performance and ability to charge and discharge over time.
The volume changes to which the anode undergoes during charge and discharge cycles depletes the electrolyte and lithium and causes mechanical stresses that ultimately lead to a loss of electrical and ionic conductivity. Incorporating porosity, electrolytic additions, conductive networks, and binders are just some of the solutions being developed.
The Researchers at the Japan Advanced Institute of Science and Technology (JAIST)) that adding a specific polymer compound bond to the silicon anode of a lithium-ion battery can significantly improve its structural stability. This makes the devices made of the anode of this material last longer Thus, it is able to meet the energy needs of electric vehicles.
To improve the performance of silicon anodes, the JAIST team led by Professor Noriyoshi Matsumi developed a technology Improve the stability of silicon particles on the anode using composite polymer binder. The result is the creation of a thin layer of SEI, which prevents the anode and electrolyte from spontaneously interacting with each other, but does not block the flow of lithium ions.
Technically, the researchers used a poly(bisiminoacenaphthenequinone) (P-BIAN) and a carboxylate-containing poly(acrylic acid) (PAA) polymer in the compound binder, linked together by hydrogen bonds. In the press release, Matsumi said the design, which consists of n-type conductive polymers and proton-donor polymers with hydrogen-bonded networks, represents “a promising future in high-capacity electrode materials.”
In fact, the structure of the polymer composite Silicon molecules held together It prevents it from disintegrating, while hydrogen bonds allow the structure to repair itself. This means that the polymers can rejoin if they break or degrade. The binder also improved the conductivity of the anode or by reducing the breakdown of the electrolyte.
To test the binder, the team made an anodic half-cell consisting of silicon nanoparticles with graphite (Si/C), a binder (P-BIAN/PAA), and a conductive acetylene black (AB) additive. Then they subjected the anode to several repeated cycles of charging and discharging.
During this process, the binder fixed the silicon anode and maintained a specific discharge capacity of 2,100 mA/g over 600 cycles. This is what researchers have shown in Article published in the magazine ACS Applied Energy Materials. For comparison, the capacity of the bare carbon and silicon anode, without a bond, dropped to 600 mA/g in just 90 cycles.
After testing the anode, the team proceeded with it disassemble and check it to check its condition. To do this, they used a spectrophotometer and a microscope, looking for cracks that could be caused by rupture of silicon, an effect very common in this type of anode. After 400 charge and discharge cycles, The anode structure has remained practically intact, only a few microcracks are shown. This indicates that the binder succeeded in improving the structural integrity of the electrode.
Overall, these results can be defined as promising and present a possible scenario for the future use of silicon anodes in lithium-ion batteries. With them, the use of lithium batteries in electric cars and even in other types of devices that need high-performance batteries will be improved.
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