More Reliable Lithium‐Sulfur Batteries: Status, Solutions and Prospects

Abstract

Lithium-sulfur (Li-S) batteries have attracted tremendous interest because of their high theoretical energy density and cost effectiveness. The target of Li-S battery research is to produce batteries with a high useful energy density that at least outperforms state-of-the-art lithium-ion batteries. However, due to an intrinsic gap between fundamental research and practical applications, the outstanding electrochemical results obtained in most Li-S battery studies indeed correspond to low useful energy densities and are not really suitable for practical requirements. The Li-S battery is a complex device and its useful energy density is determined by a number of design parameters, most of which are often ignored, leading to the failure to meet commercial requirements. The purpose of this review is to discuss how to pave the way for reliable Li-S batteries. First, the current research status of Li-S batteries is briefly reviewed based on statistical information obtained from literature. This includes an analysis of how the various parameters influence the useful energy density and a summary of existing problems in the current Li-S battery research. Possible solutions and some concerns regarding the construction of reliable Li-S batteries are comprehensively discussed. Finally, insights are offered on the future directions and prospects in Li-S battery field.

Review—Li Metal Anode in Working Lithium-Sulfur Batteries

“…z E-mail: zhang-qiang@mails.tsinghua.edu.cn at extraordinary high rates (>10 C, 1.0 C = 1672 mA g −1 ), and long lifespan (>1000 cycles) have been achieved with the remarkable progress in material science and electrochemistry. 5,6 However, most of the publications are conducted in coin cells with at least 1500% lithium and 200% electrolyte excess. 31 Few pouch cells have been declared in scientific publications.…”

“…3 Lithium−sulfur (Li−S) battery, a 'beyond Li-ion' technology, has drawn extensive attentions due to its high specific capacity (1675 mAh g −1 ) and energy density (2600 Wh kg −1 ). [4][5][6] The greater energy storage ability of Li−S batteries is realized through the phase-transformation electrochemistry based on elemental sulfur cathode and metallic lithium anode [S 8 + 16Li ↔ 8Li 2 S], 7,8 which is fundamentally different from current transition metal-based cathodes and graphite-based anodes in Li-ion batteries.…”

Multifunctionality of Carbon-based Frameworks in Lithium Sulfur Batteries

“…Figure 1 displays the charge/discharge voltage profile of a conventional Li-S battery using an ether-based electrolyte [51], with two discharge voltage plateaus being presented in the voltage profile. Here, the ring opening reaction of the cyclic S 8 molecule occurs in the initial steps, forming S 8 2− which is gradually reduced to S 6 2− and S 4 2− with an average voltage of 2.3 V versus Li + / Li [6]. During these steps, long-chain polysulfide intermediates are generated such as Li 2 S 8 , Li 2 S 6 and Li 2 S 4 that exhibit high solubility in ether electrolytes [15].…”

“…And as the active material in the cathodes of Li-S batteries, sulfur exists as multiple types of allotropes with octa-sulfur (S 8 ) being the most stable [6,51]. Here, the most common sulfur composite cathodes are fabricated through mixing S 8 and conductive carbon materials together by using a binder [52].…”

“…And aside from widespread applications in portable electronics, batteries are also expected to be applied in smart grid electricity storage and release applications because their electrochemical and energy characteristics are suitable for the storage and release of excess energy as required [1,4]. However, with growing application requirements, there is an urgent need for advanced battery systems with higher energy densities, longer cycling lives and improved cost-effectiveness [5,6]. Therefore, to meet these requirements, the focus must turn to the exploration of advanced battery systems with higher energy densities and longer life spans beyond current conventional battery packs.…”