Secondary batteries based on metal anodes (e.g., Li, Na, Mg, Zn, and Al) are among the most sought‐after candidates for next‐generation mobile and stationary storage systems because they are able to store a larger amount of energy per unit mass or volume. However, unstable electrodeposition and uncontrolled interfacial reactions occuring in liquid electrolytes cause unsatisfying cell performance and potential safety concerns for the commercial application of these metal anodes. Solid‐state electrolytes (SSEs) having a higher modulus are considered capable of inhibiting difficulties associated with the anodes and may enable building of safe all‐solid‐state metal batteries, yet several challenges, such as insufficient room‐temperature ionic conductivity and poor interfacial stability between the electrode and the electrolyte, hinder the large‐scale development of such batteries. Here, research and development of SSEs including inorganic ceramics, organic solid polymers, and organic–inorganic hybrid/composite materials for metal‐based batteries are reviewed. The comparison of different types of electrolytes is discussed in detail, in the context of electrochemical energy storage applications. Then, the focus of this study is on recent advances in a range of attractive and innovative battery chemistries and technologies that are enabled by SSEs. Finally, the challenges and future perspectives are outlined to foresee the development of SSEs.

Sulfur/polyacrylonitrile composites provide a promising route toward cathode materials that overcome multiple, stubborn technical barriers to high-energy, rechargeable lithium-sulfur (Li-S) cells. Using a facile thermal synthesis procedure in which sulfur and polyacrylonitrile (PAN) are the only reactants, we create a family of sulfur/PAN (SPAN) nanocomposites in which sulfur is maintained as S3/S2 during all stages of the redox process. By entrapping these smaller molecular sulfur species in the cathode through covalent bonding to and physical confinement in a conductive host, these materials are shown to completely eliminate polysulfide dissolution and shuttling between lithium anode and sulfur cathode. We also show that, in the absence of any of the usual salt additives required to stabilize the anode in traditional Li-S cells, Li-SPAN cells cycle trouble free and at high Coulombic efficiencies in simple carbonate electrolytes. Electrochemical and spectroscopic analysis of the SPAN cathodes at various stages of charge and discharge further show a full and reversible reduction and oxidation between elemental sulfur and Li-ions in the electrolyte to produce Li2S as the only discharge product over hundreds of cycles of charge and discharge at fixed current densities.

High-energy rechargeable batteries based on earth-abundant materials are important for mobile and stationary storage technologies. Rechargeable sodium–sulfur batteries able to operate stably at room temperature are among the most sought-after platforms because such cells take advantage of a two-electron-redox process to achieve high storage capacity from inexpensive electrode materials. Here we report a room-temperature sodium–sulfur battery that uses a microporous carbon–sulfur composite cathode, and a liquid carbonate electrolyte containing the ionic liquid 1-methyl-3-propylimidazolium-chlorate tethered to SiO2 nanoparticles. We show that these cells can cycle stably at a rate of 0.5 C (1 C=1675, mAh g−1) with 600 mAh g−1 reversible capacity and nearly 100% Coulombic efficiency. By means of spectroscopic and electrochemical analysis, we find that the particles form a sodium-ion conductive film on the anode, which stabilizes deposition of sodium. We also find that sulfur remains interred in the carbon pores and undergo solid-state electrochemical reactions with sodium ions.

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Secondary batteries based on earth-abundant sodium metal anodes are desirable for both stationary and portable electrical energy storage. Room-temperature sodium metal batteries are impractical today because morphological instability during recharge drives rough, dendritic electrodeposition. Chemical instability of liquid electrolytes also leads to premature cell failure as a result of parasitic reactions with the anode. Here we use joint density-functional theoretical analysis to show that the surface diffusion barrier for sodium ion transport is a sensitive function of the chemistry of solid–electrolyte interphase. In particular, we find that a sodium bromide interphase presents an exceptionally low energy barrier to ion transport, comparable to that of metallic magnesium. We evaluate this prediction by means of electrochemical measurements and direct visualization studies. These experiments reveal an approximately three-fold reduction in activation energy for ion transport at a sodium bromide interphase. Direct visualization of sodium electrodeposition confirms large improvements in stability of sodium deposition at sodium bromide-rich interphases.

Reliable and cost-effective technologies for electrical energy storage are in great demand in sectors of the global economy ranging from portable devices, transportation, and sustainable production of electricity from intermittent sources. Among the various electrochemical energy storage options under consideration, rechargeable lithium-sulfur (Li-S) batteries remain the most promising platform for reversibly storing large amounts of electrical energy at moderate cost set by the inherent cell chemistry. The success of Li-S storage technology in living up to this promise calls for solutions to fundamental problems associated with the inherently low electrical conductivity of sulfur and sulfides, and the complex solution chemistry of lithiated sulfur compounds in commonly used electrolytes. These problems appear well posed for innovative solutions using nanomaterials and for fundamental answers guided by the tools of nanotechnology. Beginning with a review of the current understanding of Li-S battery chemistry and operation, this review discusses how advances in nano-characterization and theoretical studies of the Li-S system are helping advance the understanding of the Li-S battery. Factors that prevent Li-S cells from realizing the theoretical capacity set by their chemistry are discussed both in terms of the impressive advances in cell design enabled by nanomaterials and recent progress aimed at nanoengineering the cathode and other cell components. Perspectives and directions for future development of the Li-S storage platform are discussed based on accumulated knowledge from previous efforts in the field as well as from the accumulated experience of the writers of this review.

Microporous carbon polyhedrons (MPCPs) are derived from unique MOF polyhedrons, and used as a model microporous carbon host for sulfur in Li–S batteries. Systematic investigations have been carried out to reveal the effects of several important parameters, such as the sulfur loading temperature, sulfur content, and the electrolyte. The MPCP/sulfur composite with sulfur exclusively embedded in micropores exhibit stable cycling performance with high Coulombic efficiency in both DOL/DME and EC/DEC electrolytes.

A sodium metal anode protected by an ion-rich polymeric membrane exhibits enhanced stability and high-Columbic efficiency cycling. Formed in situ via electropolymerization of functional imidazolium-type ionic liquid monomers, the polymer membrane protects the metal against parasitic reactions with electrolyte and, for fundamental reasons, inhibits dendrite formation and growth. The effectiveness of the membrane is demonstrated using direct visualization of sodium electrodeposition.