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both chemical and physical adsorbents have been adopted to control the "shuttle effect," including carbon matrices design at nanoscale, metal oxides/chalcogenides/ nitride used as interlayer or host, and so on. [8][9][10][11][12] Beside the material and electrode designs, it has been generally recognized that, the usage of electrolyte greatly affects the overall gravimetric energy density of Li-S batteries.In order to explore the potential of high energy density of Li-S batteries, a low electrolyte/sulfur (E/S) ratio is urgently required. However, the normal sulfur cathode usually undergoes a lithiation process via a solid-liquid-solid phase conversion. [13] To fully release the discharging capacity, it usually needs plenty of electrolyte to sufficiently dissolve the intermedia long-chain polysulfides. Thus, the normal Li-S battery system is very difficult to achieve both low E/S ratio and good electrochemical property at the same time. [14] On the contrary, the solid-solid biphasic conversion mechanism can eliminate the generation of long-chain intermediate LiPSs, greatly reducing the cell's dependency on the electrolyte usage. [15] Hence, a low E/S ratio is more probably realized by the sulfur cathodes working through the solid-solid conversion reactions. Nevertheless, although the previously reported microporous carbon/S 2-4 cathodes work through solid-solid reaction, their energy densities are still very low due to the low sulfur content (≈40 wt%). [16] Therefore, to well balance the overall energy density and electrochemical performance, both low E/S ratio and high sulfur content are even necessary. It is noteworthy that, some recent works reported that when a cathode electrolyte interface (CEI) formed on the surface of sulfur cathode, it can serve as a protective layer and avoid the entry of solvent molecules, and then the composite cathode with ≥50 wt% sulfur could work under the solid-solid conversion mechanism. [17,18] The CEI strategy can be realized by regulating electrolytes, such as adopting high-concentration carbonate-based electrolytes, and dilute carbonate/ether cosolvent electrolytes. [15,19,20] However, although the CEI plays a vital role in determining whether the Li-S batteries could work through the solid phase conversion reaction, it is still lacking of systematical research on the evolution and failure mechanism of the CEI for Li-S batteries.

The conventional lithium−sulfur battery (LSB) undergoes a "solid−liquid−solid" cathode process during which the intermediate polysulfides dissolve into the electrolyte, leading to a serious "shuttle" reaction and significantly shortened lifespan. Here, we realize a novel "solid → solid" cathode mode for LSBs via a transplantable solid electrolyte interface (SEI). The SEI is in situ formed in a carbonate-based electrolyte with high-concentration dualsalt during the initial discharge process. The solid → solid cathode process does not involve any dissolution of the intermediates; hence, the "shuttle effect" can be totally eliminated. Furthermore, the SEI shows a high electrolyte compatibility and can be transplanted to the conventional carbonate-based/ether-based electrolytes. The sulfur/carbon composite with 65% sulfur delivers a reversible specific capacity of 1009 mA h g −1 and negligible self-discharge. The SEI strategy can successfully break the limitation from the traditional "catholyte" electrode mechanism. Meanwhile, it provides large flexibility for designing high-loading carbon hosts and selecting an electrolyte for high-performance LSBs.

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