MgO‐Template Synthesis of Extremely High Capacity Hard Carbon for Na‐Ion Battery

Abstract

Extremely high capacity hard carbon for Na-ion battery, delivering 478 mAh g À1 , is successfully synthesized by heating a freeze-dried mixture of magnesium gluconate and glucose by a MgO-template technique. Influences of synthetic conditions and nano-structures on electrochemical Na storage properties in the hard carbon are systematically studied to maximize the reversible capacity. Nano-sized MgO particles are formed in a carbon matrix prepared by pre-treatment of the mixture at 600 8C. Through acid leaching of MgO and carbonization at 1500 8C, resultant hard carbon demonstrates an extraordinarily large reversible capacity of 478 mAh g À1 with a high Coulombic efficiency of 88 % at the first cycle.

Understanding of the sodium storage mechanism in hard carbon anodes

“…The obtained hard carbon materials exhibited a low specific surface area of 1.44 m 2 g −1 but a low true density of about 1.4 g cm −1 and delivered a high sodium storage capacity of 410 mAh g −1 with a plateau capacity of 284 mAh g −1 . Kamiyama et al 108 also successfully prepared hard carbon with an extremely high sodium storage capacity (478 mAh g −1 ) by a MgO‐template method (Figure 10D). They freeze‐dried the mixture of magnesium gluconate and glucose and then the obtained mixture was pyrolyzed in two steps.…”

“…(D) Schematic illustration for the two mixing procedures for preparation of the mixtures of Mg Glu and Glc. Reproduced with permission: Copyright 2021, Wiley‐VCH 108 . (E) Schematic illustration for the tailored strategy to synthesize the pitch‐coated hard carbon.…”

Replacing “Alkyl” with “Aryl” for inducing accessible channels to closed pores as plateau‐dominated sodium‐ion battery anode

“…The stacked glucose molecules may lead to hard carbons with large numbers of closed pores. Thus, the pore filling process for sodium storage is more obvious in this kind of carbons 22,36 . On the other hand, the chain molecules of cellulose are arranged in order.…”

“…Thus, the pore filling process for sodium storage is more obvious in this kind of carbons. 22,36 On the other hand, the chain molecules of cellulose are arranged in order. Although molecules will bond to each other to form a crosslinked intermediate state during pyrolysis, the internal pores are less.…”

Eco‐Friendly Synthesis of 3D Disordered Carbon Materials for High‐Performance Dual Carbon Na‐Ion Capacitors

“…[1] In contrast, highly disordered carbons such as hard carbons have shown their potential in Na-ion batteries, with capacities already exceeding in some cases 300 mAh g À 1 . [2][3][4][5] However, their Na storage kinetics is too slow for their implementation in Na-ion capacitors on account of their predominantly diffusion-controlled sodium storage mechanism, that is intercalation/de-intercalation. Carbon materials targeted at NICs should promote the fast pseudocapacitive sodium storage mechanism in the sloping region at high potentials (> 0.1 V vs. Na/Na + ), as well as provide shortened diffusion distances to speed up sodium ions transport.…”