Heterostructured Nanoporous Silicon Anode for High Energy Density Lithium Ion Battery

Abstract

Silicon has been identified as the best candidate element for next generation lithium-ion batteries (LIB) anode material. It is widely available and capacity is more than ten times of conventional graphite. However, using silicon anode in LIB, still remains an unfinished agenda despite very sincere global research efforts1-3. The reasons for this are ~300% expansion in volume upon lithiation, causing fracture or pulverization of the anode structure and sluggish diffusion of lithium in bulk silicon. These challenges can be addressed by using porous silicon. The porosity in silicon can accommodate the majority of the volume expansion during repeated charge-discharge cycling of battery. Most of the under-development processes for porous silicon necessitate sourcing the material from electronic grade Si-wafers. Though this is overkill for many applications, the reason for using electronic grade silicon is due to lack of a cost effective processing route for porous silicon. Here we report a novel and industrially scalable route for production of heterostructured nanoporous silicon particles with a high specific area from low grade Si raw material. We demonstrate capacity retention of more than 1000mAh/gm and columbic efficiency in excess of 98% even after 300+ cycles of operation, using this porous silicon as anode material in a coin cell. This process can also be easily integrated with existing battery fabrication methods, without requiring major changes. Our proposed method is likely to ensure a promising, high throughput process for production porous silicon and its use in lithium ion batteries.