Charge and discharge cycles in lithium-ion batteries cause anode volumes to change, reducing battery capacity and cycle life. Now, researchers at GIST in South Korea have developed a new way to strengthen the anode and modify it, regardless of its material or how it is manufactured.
Over time, charging and discharging causes the nanoparticles in the anode to crack and cluster together at the electrode-electrolyte interface. This leads to an electrical disconnection, reducing the amount of charge the anode can store or transport. To address this issue, GIST researchers have developed a method to make the anode more resilient against volume changes by encapsulating the nanoparticles in an elastic web-like structure.
The researchers described in the Journal of Materials Chemistry A how they used a conventional anode containing silicon nanoparticles held together by a polymer (polyvinylidene fluoride) binder. To accommodate the web-like structure, they removed the binder by heating the anode using an annealing process.
The gap between the nanoparticles was then filled in with reduced graphene oxide (rGO) solution, which dried up to form a web that held the silicon nanoparticles together and prevented them from cracking. Additionally, the web provided a conductive pathway for the electrons, allowing the nanoparticles to bind with lithium.
The researchers used a technique called “spin coating” to coat the anode surface with rGO. The rGO coating served as a seed layer for the deposition of a protective layer consisting of zinc oxide with magnesium and gallium metal oxides added to it (MGZO). This MGZO layer provided structural stability to the anode.
“The structure retained a high storage capacity of 1566 mA h g-1 after 500 cycles and showed 91% coulombic efficiency, which relates to the battery life. This could pave the way for electric vehicles that enable us to drive long distances on one-time charging,” said Prof. Hyeong-Jin Kim, who joined GIST after serving as president of LG Chem Michigan.