Applying what’s known as Murray’s law to battery material design could significantly improve battery life, researchers at Clare College Cambridge believe.
The researchers have designed a porous material that utilises a vascular structure, such as that found in the veins of a leaf, and could make energy transfers more efficient.
The material could improve the performance of rechargeable batteries, optimising the charge and discharge process and relieving stresses within the battery electrodes, which, at the moment, limit their life span.
Murray’s Law governs the way natural organisms survive and grow. According to this law, the entire network of pores existing on different scales in such biological systems are interconnected in a way to facilitate the transfer of liquids and minimize resistance throughout the network.
The plant stems of a tree, or leaf veins, for example, optimize the flow of nutrients for photosynthesis with both high efficiency and minimum energy consumption by regularly branching out to smaller scales.
The research team, led by Prof Bao-Lian Su, adapted Murray’s Law for the fabrication of the first ever synthetic ‘Murray material’ and applied it to lithium ion battery electrodes. They found that the multi-scale porous networks of their synthetic material significantly enhanced the performance of the processes.
Writing in Nature Communications this week, the team describes how it used zinc oxide (ZnO) nanoparticles as the primary building block of their Murray material. These nanoparticles, containing small pores within them, form the lowest level of the porous network. The team arranged the ZnO particles through a layer-by layer evaporation-driven self-assembly process.
This creates a second level of porous networks between the particles. During the evaporation process, the particles also form larger pores due to solvent evaporation, which represents the top level of pores, resulting in a three level Murray material.
The team successfully fabricated these porous structures with the precise diameter ratios required to obey Murray’s law, enabling the efficient transfer of materials across the multilevel pore network.
Co-author, Dr Tawfique Hasan, of the Cambridge Graphene Centre, part of the University’s Department of Engineering, adds: ‘This very first demonstration of a Murray material fabrication process is incredibly simple and is entirely driven by the nanoparticle self-assembly. Large scale manufacturability of this porous material is possible, making it an exciting, enabling technology, with potential impact across many applications.”
The team proved that its Murray material can significantly improve the long term stability and fast charge/discharge capability for lithium ion storage, with a capacity improvement of up to 25 times compared to state of the art graphite material currently used in lithium ion battery electrodes.
The hierarchical nature of the pores also reduces the stresses in these electrodes during the charge/discharge processes, improving their structural stability and resulting in a longer lifetime for energy storage devices.
