Advanced silicon-based electrodes for high-energy lithium-ion batteries

In commercial lithium-ion batteries (LIBs), the negative electrode (conventionally called the anode) is generally fabricated from graphite. For enhanced performance and critical safety considerations, LIBs must be constructed such that the capacity of the negative electrode is higher than that of the positive electrode. This condition imposed by safety concerns implies that substituting for graphite with a material that has a higher specific capacity is desirable to increase the energy density of LIBs. In this chapter, we report on two types of silicon (Si) that can be employed as negative electrodes for lithium-(Li)-ion batteries (LIBs). The first type is based on metallurgical-grade silicon produced by a low-cost mechanical grinding process from ingots to nanostructured particles. The second one, more expansive, involves an induced plasma process that produces homogeneous spherical Si nanoparticles. Moreover, we describe the challenges and solutions of the use of carbon-coated silicone and a graphite-silicone composite in advanced electrodes for high-energy LIBs. To characterize the volume expansion of the silicone particles, we employed in situ transmission electron microscopy for the observation of a typical 200-nm pristine spherical silicon particle synthesized using an induced plasma. When a bias potential of - 2 to -5 V was used to initiate lithiation of the silicon particle, a rapid reaction from the interior of the particle was observed, forming a core-shell structure. The crystalline core was gradually transformed into an amorphous LixSi alloy. An advanced composite Li-ion anode made from this nanometer-size powder was found to have a high reversible capacity of 2400 mAh g-1 and an improved cycling stability compared to micrometer-sized powder. It is proposed that improved battery cycling performance is ascribed to the nanoscale silicon particles which suppresses the volume expansion owing to it is super plasticity.