Maider Zarrabeitia

2.3. Soft and Hard Carbons Soft and hard carbons differ primarily in their structure and ability to completely reconvert into graphite (Figure 7a) at temperatures above 2500 °C. Soft carbon (SC) is graphitizable, with long-range order (Figure 7b), high conductivity, and adjustable interplanar distance and crystallinity [19,108], whereas hard carbons (HC) are non-graphitizable materials with disordered structures (although short-range ordered) and large interlayer spacing (Figure 7c) [108,109].

Abstract Sodium-ion batteries are well positioned to become, in the near future, the energy storage system for stationary applications and light electromobility. However, two main drawbacks feed their underperformance, namely the irreversible sodium consumption during solid electrolyte interphase formation and the low sodiation degree of one of the most promising cathode materials: the P2-type layered oxides.