Safety, nontoxicity, and durability directly determine the applicability of the essential characteristics of the lithium (Li)‐ion battery. Particularly, for the lithium–sulfur battery, due to the low ignition temperature of sulfur, metal lithium as the anode material, and the use of flammable organic electrolytes, addressing security problems is of increased difficulty. In the past few years, two basic electrolyte systems are studied extensively to solve the notorious safety issues. One system is the conventional organic liquid electrolyte, and the other is the inorganic solid‐state or quasi‐solid‐state composite electrolyte. Here, the recent development of engineered liquid electrolytes and design considerations for solid electrolytes in tackling these safety issues are reviewed to ensure the safety of electrolyte systems between sulfur cathode materials and the lithium‐metal anode. Specifically, strategies for designing and modifying liquid electrolytes including introducing gas evolution, flame, aqueous, and dendrite‐free electrolytes are proposed. Moreover, the considerations involving a high‐performance Li+ conductor, air‐stable Li+ conductors, and stable interface performance between the sulfur cathode and the lithium anode for developing all‐solid‐state electrolytes are discussed. In the end, an outlook for future directions to offer reliable electrolyte systems is presented for the development of commercially viable lithium–sulfur batteries.

are highly promising thanks to several advantages: (1) zinc metal possesses high specific capacities (820 mAh g −1 and 5855 mAh cm −3 ); [6] (2) zinc metal has high compatibility in water and a reasonably low electrochemical potential (−0.76 V vs SHE), which enables its application of aqueous battery system with extremely high safety; [7] (3) zinc has higher abundance than lithium in the earth crust, and the mature production technology makes the price of zinc extremely costeffective. [8] However, zinc metal's performance in aqueous ZIBs suffers from several problems, particularly dendrite formation. [9] Many factors can contribute to zinc-dendrite formation, especially the uneven distribution of surface charge density at the anode and the inhomogeneous ion flux in the electrolyte, causing zinc to deposit unevenly and form zinc tips on the surface of the anode. Such as-formed zinc-metal tips tend to exhibit locally concentrated surface charge density and promote the growth of zinc over other areas, which is often referred to as the notorious "tip effect". [10] These zinc tips eventually grow into prominent zinc dendrites during cycling and finally cause an internal battery short circuit (Figure 1, top panel). Thus, a stable zinc-metal anode with dendrite-free deposition behavior is a key requirement for the broad application of aqueous ZIBs.In recent years, suppressing the zinc-dendrite growth in aqueous zinc-ion batteries has attracted widespread research interest. Various approaches have been adopted to fulfill this goal, including optimizing electrolyte components, [11] applying 3D current collectors, [12] and constructing artificial interphases. [13] Constructing artificial interphases before battery assembly is an easy and highly efficient strategy to enable a highly stable zinc anode in operating batteries. [14] These artificial protective layers are generally proposed to introduce physiochemical interactions with zinc, and thus realize its stable deposition. However, most reported artificial protective layers were prepared with a relatively high thickness, [14,15] which would inevitably harm the gravimetric and volumetric specific capacities of the ZIBs. Therefore, designing thin artificial protective layers, which can still achieve a dendrite-free zinc-deposition behavior while minimizing the impact on battery energy density, becomes critical for zinc-metal anodes. Considering the high Young's modulus of zinc, [16] constructing a protective layer to suppress zinc-dendrite growth is a very challenging task.Aqueous zinc-ion batteries are regarded as ideal candidates for stationary energy-storage systems due to their low cost and high safety. However, zinc can readily grow into dendrites, leading to limited cycling performance and quick failure of the batteries. Herein, a novel strategy is proposed to mitigate this dendrite problem, in which a selectively polarized ferroelectric polymer material (poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))) is employed as a surface protective layer on zinc ...

Giant spin-orbit torque (SOT) from topological insulators (TIs) provides an energy efficient writing method for magnetic memory, which, however, is still premature for practical applications due to the challenge of the integration with magnetic tunnel junctions (MTJs). Here, we demonstrate a functional TI-MTJ device that could become the core element of the future energy-efficient spintronic devices, such as SOT-based magnetic random-access memory (SOT-MRAM). The state-of-the-art tunneling magnetoresistance (TMR) ratio of 102% and the ultralow switching current density of 1.2 × 105 A cm−2 have been simultaneously achieved in the TI-MTJ device at room temperature, laying down the foundation for TI-driven SOT-MRAM. The charge-spin conversion efficiency θSH in TIs is quantified by both the SOT-induced shift of the magnetic switching field (θSH = 1.59) and the SOT-induced ferromagnetic resonance (ST-FMR) (θSH = 1.02), which is one order of magnitude larger than that in conventional heavy metals. These results inspire a revolution of SOT-MRAM from classical to quantum materials, with great potential to further reduce the energy consumption.

Ferroelectric memristors have found extensive applications as a type of nonvolatile resistance switching memories in information storage, neuromorphic computing, and image recognition. Their resistance switching mechanisms are phenomenally postulated as the modulation of carrier transport by polarization control over Schottky barriers. However, for over a decade, obtaining direct, comprehensive experimental evidence has remained scarce. Here, we report an approach to experimentally demonstrate the origin of ferroelectric resistance switching using planar van der Waals ferroelectric α-In2Se3 memristors. Through rational interfacial engineering, their initial Schottky barrier heights and polarization screening charges at both terminals can be delicately manipulated. This enables us to find that ferroelectric resistance switching is determined by three independent variables: ferroelectric polarization, Schottky barrier variation, and initial barrier height, as opposed to the generally reported explanation. Inspired by these findings, we demonstrate volatile and nonvolatile ferroelectric memristors with large on/off ratios above 104. Our work can be extended to other planar long-channel and vertical ultrashort-channel ferroelectric memristors to reveal their ferroelectric resistance switching regimes and improve their performances.

Skyrmion helicity, which defines the spin swirling direction, is a fundamental parameter that may be utilized to encode data bits in future memory devices. Generally, in centrosymmetric ferromagnets, dipole skyrmions with helicity of −π/2 and π/2 are degenerate in energy, leading to equal populations of both helicities. On the other hand, in chiral materials where the Dzyaloshinskii–Moriya interaction (DMI) prevails and the dipolar interaction is negligible, only a preferred helicity is selected by the type of DMI. However, whether there is a rigid boundary between these two regimes remains an open question. Herein, the observation of dipole skyrmions with unconventional helicity polarization in a van der Waals ferromagnet, Fe5−δGeTe2, is reported. Combining magnetometry, Lorentz transmission electron microscopy, electrical transport measurements, and micromagnetic simulations, the short‐range superstructures in Fe5−δGeTe2 resulting in a localized DMI contribution, which breaks the degeneracy of the opposite helicities and leads to the helicity polarization, is demonstrated. Therefore, the helicity feature in Fe5−δGeTe2 is controlled by both the dipolar interaction and DMI that the former leads to Bloch‐type skyrmions with helicity of ±π/2 whereas the latter breaks the helicity degeneracy. This work provides new insights into the skyrmion topology in van der Waals materials.