Effect of Conductive Additives on Electrochemical Performance of All-Solid-State Li-S Batteries

Authors

Dong-Hao Wang, College of Energy, Xiamen University, Xiamen 361005, Fujian, China;
He-Feng Yan, College of Energy, Xiamen University, Xiamen 361005, Fujian, China;
Zheng-Liang Gong, College of Energy, Xiamen University, Xiamen 361005, Fujian, China;Follow

Corresponding Author

Zheng-Liang Gong(zlgong@xmu.edu.cn)

Abstract

All-solid-state lithium sulfur batteries (ASSLSBs) with inorganic solid electrolytes offer an opportunity to realize both high energy density (lithium metal ~ 3860 mAh·g^-1, sulfur ~ 1675 mAh·g^-1), safety and reliability, via eliminating the polysulfides shuttle effect and flammable liquid electrolyte. However, it still remains a huge challenge for ASSLSBs to achieve high areal active mass loading, high utilization efficiency of the active materials and good cycle stability simultaneously due to the insulating nature of sulfur and Li₂S (conductivities of sulfur and Li₂S are 5×10^-30 S·cm^-1 and 3.6×10^-7 S·cm^-1 at room temperature, respectively), and the large volume change during cycling due to the difference in mass density between sulfur (2.03 g·cm^-3) and Li₂S (1.67 g·cm^-3). Herein, Li₇P₃S₁₁ (LPS) glass-ceramic sulfide solid electrolyte with high ionic conductivity of 1.7×10^-3 S·cm^-1 at room temperature was synthesized through high energy ball-milling and a two-step heat treatment. And the effect of conductive additives on electrochemical performance of ASSLSBs employing sulfur as an active material and LPS as a solid electrolyte was systematically investigated. It shows that ASSLSBs employing acetylene black (AB) as a conductive additive exhibited much better electrochemical performance with high capacity of 1681 mAh·g^-1 and good rate performance at 60℃ than Super P and Ketjen Black. ASSLBs employing sulfur composite cathode with the optimized mass ratio of S:AB:solid electrolyte = 4:2:4 presented the best electrochemical performance at both room temperature and 60℃. ASSLBs employing S₄₀-AB₂₀-LPS₄₀ composite cathode delivered a high capacity of 1450 mAh·g^-1 with good cycling stability and high coulombic efficiency of ~100% at 60℃. And good electrochemical performance could also be obtained even at room temperature. A high initial discharge capacity of ~1270 mAh·g^-1 was obtained and a high capacity of 1140 mAh·g^-1 was retained after 30 cycles with high coulombic efficiency of ~100%.

Graphical Abstract

Keywords

all-solid-state lithium sulfur battery, composite sulfur cathode, electron/ion transport, high sulfur content

DOI Link

https://doi.org/10.13208/j.electrochem.200527

Publication Date

2021-08-28

Online Available Date

2020-07-17

Revised Date

2020-07-16

Received Date

2020-05-27

Recommended Citation

Dong-Hao Wang, He-Feng Yan, Zheng-Liang Gong. Effect of Conductive Additives on Electrochemical Performance of All-Solid-State Li-S Batteries[J]. Journal of Electrochemistry, 2021 , 27(4): 388-395.
DOI: All-solid-state lithium sulfur batteries (ASSLSBs) with inorganic solid electrolytes offer an opportunity to realize both high energy density (lithium metal ~ 3860 mAh·g^-1, sulfur ~ 1675 mAh·g^-1), safety and reliability, via eliminating the polysulfides shuttle effect and flammable liquid electrolyte. However, it still remains a huge challenge for ASSLSBs to achieve high areal active mass loading, high utilization efficiency of the active materials and good cycle stability simultaneously due to the insulating nature of sulfur and Li₂S (conductivities of sulfur and Li₂S are 5×10^-30 S·cm^-1 and 3.6×10^-7 S·cm^-1 at room temperature, respectively), and the large volume change during cycling due to the difference in mass density between sulfur (2.03 g·cm^-3) and Li₂S (1.67 g·cm^-3). Herein, Li₇P₃S₁₁ (LPS) glass-ceramic sulfide solid electrolyte with high ionic conductivity of 1.7×10^-3 S·cm^-1 at room temperature was synthesized through high energy ball-milling and a two-step heat treatment. And the effect of conductive additives on electrochemical performance of ASSLSBs employing sulfur as an active material and LPS as a solid electrolyte was systematically investigated. It shows that ASSLSBs employing acetylene black (AB) as a conductive additive exhibited much better electrochemical performance with high capacity of 1681 mAh·g^-1 and good rate performance at 60℃ than Super P and Ketjen Black. ASSLBs employing sulfur composite cathode with the optimized mass ratio of S:AB:solid electrolyte = 4:2:4 presented the best electrochemical performance at both room temperature and 60℃. ASSLBs employing S₄₀-AB₂₀-LPS₄₀ composite cathode delivered a high capacity of 1450 mAh·g^-1 with good cycling stability and high coulombic efficiency of ~100% at 60℃. And good electrochemical performance could also be obtained even at room temperature. A high initial discharge capacity of ~1270 mAh·g^-1 was obtained and a high capacity of 1140 mAh·g^-1 was retained after 30 cycles with high coulombic efficiency of ~100%.

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