All-solid-state lithium–sulfur batteries with three-dimensional mesoporous electrode structures

Abstract

Although the characteristics of lithium-sulfur batteries are advantageous for various applications, batteries with liquid electrolytes show capacity fading due to the dissolution of polysulfides. All-solid-state lithium-sulfur batteries with highly reversible characteristics are developed using a three-dimensional carbon matrix framework structure for the sulfur cathode. Sulfur is introduced into a carbon replica framework with a pore size of 8-100 nm. The composite electrode structure provides high electronic conduction and allows high cathode utilization during the battery reaction. The capacity of cells using a LiAl alloy as the negative electrode and the thio-LISICON (lithium superionic conductor) electrolyte increases when the pore size of the carbon replica is decreased from 100 nm to less than 15 nm. The highest capacity is obtained for the carbon replica with a pore size of 8.6 nm and a wall thickness of 4.7 nm. An examination of the relationship between the charge-discharge capacity and the structure of carbon replicas with different pore sizes and wall thicknesses indicates that three-dimensional highly ordered mesoporous carbon with a small pore size is a promising electrode structure for lithium-sulfur all-solid-state batteries.

Composite Sulfur Electrode for All-solid-state Lithium–sulfur Battery with Li₂S–GeS₂–P₂S₅-based Thio-LISICON Solid Electrolyte

“…Flat voltage regions were observed around 1.7 and 2.3 V (vs. Li-Al) during discharging and charging, respectively, indicative of the reversible reaction of sulfur with lithium in the composites. 4,20 Additional reactions were confirmed at around 1.2 V for milling times of 300 and 600 min, indicative of a reaction of carbon and/or the solid electrolyte material with lithium. 4,18,23 The composite milled for 10 min exhibited a low 1st discharge capacity of approximately 550 mAh g ¹1 , which is less than half of the theoretical capacity of sulfur.…”

“…3,4,20 The Li 3.25 Ge 0.25 P 0.75 S 4 powder (70 mg) was pressed into a pellet at 280 MPa, which served as the separator layer in the battery. Pressing was performed using a test cell consisting of a polyethylene terephthalate (PET) cylinder body with an inner diameter of approximately 10 mm.…”

“…4,17,18 However, there are few reports of the Li 2 S-GeS 2 -P 2 S 5 system contributing to the battery reaction in all-solid-state lithium-sulfur batteries. Since the ionic conductivity, stability, and electrochemical properties of SEs depend on their composition, 8 the Li 2 S-GeS 2 -P 2 S 5 system must be investigated; a reaction mechanism, that differs from Li 2 S-P 2 S 5 -based materials, is expected to be found in the battery.…”

“…4,20 The structure and electrochemical properties of the prepared composite electrodes were investigated. Structural analysis clarified the dependence of the electrochemical characteristics on the milling time and the associated modification of the SE.…”

“…[2][3][4][5] However, sulfur-based active materials (e.g., S and Li 2 S) show poor electronic and ionic conductivity, 6,7 resulting in a low utilization ratio of active material and poor battery performance. Therefore, the active materials are mixed with electronic conductors (e.g., carbon and metal) and solid electrolytes to form composite electrodes.…”