Solid-state lithium (Li) metal batteries are prominent among next-generation energy storage technologies due to their significantly high energy density and reduced safety risks. Previously, solid electrolytes have been intensively studied and several materials with high ionic conductivity have been identified. However, there are still at least three obstacles before making the Li metal foil-based solid-state systems viable, namely, high interfacial resistance at the Li/electrolyte interface, low areal capacity, and poor power output. The problems are addressed by incorporating a flowable interfacial layer and three-dimensional Li into the system. The flowable interfacial layer can accommodate the interfacial fluctuation and guarantee excellent adhesion at all time, whereas the three-dimensional Li significantly reduces the interfacial fluctuation from the whole electrode level (tens of micrometers) to local scale (submicrometer) and also decreases the effective current density for high-capacity and high-power operations. As a consequence, both symmetric and full-cell configurations can achieve greatly improved electrochemical performances in comparison to the conventional Li foil, which are among the best reported values in the literature. Noticeably, solid-state full cells paired with high-mass loading LiFePO4 exhibited, at 80°C, a satisfactory specific capacity even at a rate of 5 C (110 mA·hour g-1) and a capacity retention of 93.6% after 300 cycles at a current density of 3 mA cm-2 using a composite solid electrolyte middle layer. In addition, when a ceramic electrolyte middle layer was adopted, stable cycling with greatly improved capacity could even be realized at room temperature.

Metasurfaces consisting of nanoscale structures are underpinning new physical principles for the creation and shaping of quantum states of light. Multiphoton states that are entangled in spatial or angular domains are an essential resource for many quantum applications; however, their production traditionally relies on bulky nonlinear crystals. We predict and demonstrate experimentally the generation of spatially entangled photon pairs through spontaneous parametric down-conversion from a metasurface incorporating a nonlinear thin film of lithium niobate covered by a silica meta-grating. We measure the correlations of photon pairs and identify their spatial antibunching through violation of the classical Cauchy-Schwarz inequality, witnessing the presence of multimode entanglement. Simultaneously, the photon-pair rate is strongly enhanced by 450 times as compared to unpatterned films because of high-quality-factor resonances. These results pave the way to miniaturization of various quantum devices by incorporating ultrathin metasurfaces functioning as room temperature sources of quantum-entangled photons.

Aqueous lithium energy storage systems address environmental sustainability and safety issues. However, significant capacity fading after repeated cycles of charge-discharge and during float charge limit their practical application compared to their nonaqueous counterparts. We introduce an artificial solid electrolyte interphase (SEI) to the aqueous systems and report the use of graphene films as an artificial SEI (G-SEI) that substantially enhance the overall performance of an aqueous lithium battery and a supercapacitor. The thickness (1 to 50 nm) and the surface area (1 cm2 to 1 m2) of the G-SEI are precisely controlled on the LiMn2O4-based cathode using the Langmuir trough-based techniques. The aqueous battery with a 10-nm-thick G-SEI exhibits a discharge capacity as high as 104 mA·hour g-1 after 600 cycles and a float charge current density as low as 1.03 mA g-1 after 1 day, 26% higher (74 mA·hour g-1) and 54% lower (1.88 mA g-1) than the battery without the G-SEI, respectively. We propose that the G-SEI on the cathode surface simultaneously suppress the structural distortion of the LiMn2O4 (the Jahn-Teller distortion) and the oxidation of conductive carbon through controlled diffusion of Li+ and restricted permeation of gases (O2 and CO x ), respectively. The G-SEI on both small (~1 cm2 in 1.15 mA·hour cell) and large (~9 cm2 in 7 mA·hour cell) cathodes exhibit similar property enhancement, demonstrating excellent potential for scale-up and manufacturing.

Recycling lithium from spent batteries is challenging because of problems with poor purity and contamination. Here, we propose a green and sustainable lithium recovery strategy for spent batteries containing LiFePO4, LiCoO2, and LiNi0.5Co0.2Mn0.3O2 electrodes. Our proposed configuration of "lithium-rich electrode || LLZTO@LiTFSI+P3HT || LiOH" system achieves double-side and roll-to-roll recycling of lithium-containing electrode without destroying its integrity. The LiTFSI+P3HT-modified LLZTO membrane also solves the H+/Li+ exchange problem and realizes a waterproof protection of bare LLZTO in the aqueous working environment. On the basis of these advantages, our system shows high Li selectivity (97%) and excellent Faradaic efficiency (≥97%), achieving high-purity (99%) LiOH along with the production of H2. The Li extraction processes for spent LiFePO4, LiNi0.5Co0.2Mn0.3O2, and LiCoO2 batteries is shown to be economically feasible. Therefore, this study provides a previously unexplored technology with low energy consumption as well as high economic and environmental benefits to realize sustainable lithium recycling from spent batteries.

The life span of lithium batteries as energy storage devices is plagued by irreversible interfacial reactions between reactive anodes and electrolytes. Occurring on polycrystal surface, the reaction process is inevitably affected by the surface microstructure of anodes, of which the understanding is imperative but rarely touched. Here, the effect of grain boundary of lithium metal anodes on the reactions was investigated. The reactions preferentially occur at the grain boundary, resulting in intercrystalline reactions. An aluminum (Al)-based heteroatom-concentrated grain boundary (Al-HCGB), where Al atoms concentrate at grain boundary, was designed to inhibit the intercrystalline reactions. In particular, the scalable preparation of Al-HCGB was demonstrated, with which the cycling performance of a pouch cell (355 Wh kg-1) was significantly improved. This work opens a new avenue to explore the effect of the surface microstructure of anodes on the interfacial reaction process and provides an effective strategy to inhibit reactions between anodes and electrolytes for long-life-span practical lithium batteries.

Lithium hydride has been widely identified as the major component of the solid-electrolyte interphase of Li metal batteries (LMBs), but is often regarded as being detrimental to the stabilization of LMBs. Here, we identify the positive and important role of LiH in promoting fast diffusion of Li ions by building a unique three-dimensional (3D) Li metal anode composed of LiMg alloys uniformly confined into graphene-supported LiH nanoparticles. The built-in electric field at the interface between LiH with high Li ion conductivity and LiMg alloys effectively boosts Li diffusion kinetics toward favorable Li plating into lithiophilic LiMg alloys through the surface of LiH. Therefore, the diffusion coefficient of Li ions of the thus-formed 3D structured Li metal anode is 10 times higher than the identical anode without the presence of LiH, and it exhibits a long cycle life of over 1200 hours at 3 mA cm-2 under 5 mA hour cm-2.

High-energy lithium metal batteries (LMBs) are expected to play important roles in the next-generation energy storage systems. However, the uncontrolled Li dendrite growth in liquid electrolytes still impedes LMBs from authentic commercialization. Upgrading the traditional electrolyte system from liquid to solid and quasi-solid has therefore become a key issue for prospective LMBs. From this premise, it is particularly urgent to exploit facile strategies to accomplish this goal. We report that commercialized liquid electrolyte can be easily converted into a novel quasi-solid gel polymer electrolyte (GPE) via a simple and efficient in situ gelation strategy, which, in essence, is to use LiPF6 to induce the cationic polymerization of the ether-based 1,3-dioxolane and 1,2-dimethoxyethane liquid electrolyte under ambient temperature. The newly developed GPE exhibits elevated protective effects on Li anodes and has universality for diversified cathodes including but not restricted to sulfur, olivine-type LiFePO4, and layered LiNi0.6Co0.2Mn0.2O2, revealing tremendous potential in promoting the large-scale application of future LMBs.

Rechargeable electrochemical cells with metallic anodes are of increasing scientific and technological interest. The complex composition, poorly defined morphology, heterogeneous chemistry, and unpredictable mechanics of interphases formed spontaneously on the anodes are often examined but rarely controlled. Here, we couple computational studies with experimental analysis of well-defined LiAl electrodes in realistic electrochemical environments to design anodes and interphases of known composition. We compare phase behavior, Li binding energies, and activation energy barriers for adatom transport and study their effects on the electrochemical reversibility of battery cells. As an illustration of potential practical benefits of our findings, we create cells in which LiAl anodes protected by Langmuir-Blodgett MoS2 interphases are paired with 4.1 mAh cm-2 LiNi0.8Co0.1Mn0.1O2 cathodes. These studies reveal that small- and larger-format (196 mAh, 294 Wh kg-1, and 513 Wh liter-1) cells based on protected LiAl anodes exhibit high reversibility and support stable Li migration during recharge of the cells.

As a special class of cathode materials for lithium-sulfur batteries, pyrolyzed polyacrylonitrile/sulfur (pPAN/S) can completely solve the polysulfide dissolution problem and deliver reliable performance. However, the applicable S contents of pPAN/S are usually lower than 50 weight % (wt %), and their capacity utilizations are not sufficient, both of which greatly limit their energy densities for commercial applications. We report a pyrolyzed polyacrylonitrile/selenium disulfide (pPAN/SeS2) composite with dramatically enhanced active material content (63 wt %) and superior performances for both lithium and sodium storage. As a result, pPAN/SeS2 delivers high capacity of >1100 mAh g-1 at 0.2 A g-1 for Li storage with extremely stable cycle life over 2000 cycles at 4.0 A g-1. Moreover, when applied in a room temperature Na-SeS2 battery, pPAN/SeS2 achieves superior capacity of >900 mAh g-1 at 0.1 A g-1 and delivers prolonged cycle life over 400 cycles at 1.0 A g-1.

We present a novel concept to achieve high performance and high safety simultaneously by passivating a Li-ion cell and then self-heating before use. By adding a small amount of triallyl phosphate in conventional electrolytes, we show that resistances of the passivated cells can increase by ~5×, thereby ensuring high safety and thermal stability. High power before battery operation is delivered by self-heating to an elevated temperature such as 60°C within tens of seconds. The present approach of building a resistive cell with highly stable materials and then delivering high power on demand through rapid thermal stimulation leads to a revolutionary route to high safety when batteries are not in use and high battery performance upon operation.

Lithium (Li) metal anode have shown exceptional potential for high-energy batteries. However, practical cell-level energy density of Li metal batteries is usually limited by the low areal capacity (<3 mAh cm-2) because of the accelerated degradation of high-areal capacity Li metal anodes upon cycling. Here, we report the design of hyperbranched vertical arrays of defective graphene for enduring deep Li cycling at practical levels of areal capacity (>6 mAh cm-2). Such atomic-to-macroscopic trans-scale design is rationalized by quantifying the degradation dynamics of Li metal anodes. High-energy Li metal cells are prototyped under realistic conditions with high cathode capacity (>4 mAh cm-2), low negative-to-positive electrode capacity ratio (1:1), and low electrolyte-to-capacity ratio (5 g Ah-1), which shed light on a promising move toward practical Li metal batteries.

All-solid-state batteries are a potential game changer in the energy storage market; however, their practical employment has been hampered by premature short circuits caused by the lithium dendritic growth through the solid electrolyte. Here, we demonstrate that a rational layer-by-layer strategy using a lithiophilic and electron-blocking multilayer can substantially enhance the performance/stability of the system by effectively blocking the electron leakage and maintaining low electronic conductivity even at high temperature (60°C) or under high electric field (3 V) while sustaining low interfacial resistance (13.4 ohm cm2). It subsequently results in a homogeneous lithium plating/stripping, thereby aiding in achieving one of the highest critical current densities (~3.1 mA cm-2) at 60°C in a symmetric cell. A full cell paired with a commercial-level cathode exhibits exceptionally long durability (>3000 cycles) and coulombic efficiency (99.96%) at a high current density (2 C; ~1.0 mA cm-2), which records the highest performance among all-solid-state lithium metal batteries reported to date.

Lithium metal has been considered as an ideal anode candidate for future high energy density lithium batteries. Herein, we develop a three-dimensional (3D) hybrid host consisting of Ag nanoparticle-embedded nitrogen-doped carbon macroporous fibers (denoted as Ag@CMFs) with selective nucleation and targeted deposition of Li. The 3D macroporous framework can inhibit the formation of dendritic Li by capturing metallic Li in the matrix as well as reducing local current density, the lithiophilic nitrogen-doped carbons act as homogeneous nucleation sites owing to the small nucleation barrier, and the Ag nanoparticles improve the Li nucleation and growth behavior with the reversible solid solution-based alloying reaction. As a result, the Ag@CMF composite enables a dendrite-free Li plating/stripping behavior with high Coulombic efficiency for more than 500 cycles. When this anode is coupled with a commercial LiFePO4 cathode, the assembled full cell manifests high rate capability and stable cycling life.

Solid-state halide electrolytes have gained revived research interests owing to their high ionic conductivity and high-voltage stability. However, synthesizing halide electrolytes from a liquid phase is extremely challenging because of the vulnerability of metal halides to hydrolysis. In this work, ammonium-assisted wet chemistry is reported to synthesize various solid-state halide electrolytes with an exceptional ionic conductivity (>1 microsiemens per centimeter). Microstrain-induced localized microstructure change is found to be beneficial to lithium ion transport in halide electrolytes. Furthermore, the interfacial incompatibility between halide electrolytes and lithium metal is alleviated by transforming the mixed electronic/ionic conductive interface into a lithium ion–conductive interface. Such all-solid-state lithium-metal batteries (ASSLMBs) demonstrate a high initial coulombic efficiency of 98.1% based on lithium cobalt oxide and a high discharge capacity of 166.9 microampere hours per gram based on single-crystal LiNi0.6Mn0.2Co0.2O2. This work provides universal approaches in both material synthesis and interface design for developing halide-based ASSLMBs.

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. We show that inelastic scattering spectroscopy using high-energy x-ray photons (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials.

An all-solid-state lithium battery using inorganic solid electrolytes requires safety assurance and improved energy density, both of which are issues in large-scale applications of lithium-ion batteries. Utilization of high-capacity lithium-excess electrode materials is effective for the further increase in energy density. However, they have never been applied to all-solid-state batteries. Operational difficulty of all-solid-state batteries using them generally lies in the construction of the electrode-electrolyte interface. By the amorphization of Li2RuO3 as a lithium-excess model material with Li2SO4, here, we have first demonstrated a reversible oxygen redox reaction in all-solid-state batteries. Amorphous nature of the Li2RuO3-Li2SO4 matrix enables inclusion of active material with high conductivity and ductility for achieving favorable interfaces with charge transfer capabilities, leading to the stable operation of all-solid-state batteries.

The development of a cathode for solid-state lithium-oxygen batteries has been hindered in practice by a low capacity and limited cycle life despite their potential for high energy density. Here, a previously unexplored strategy is proposed wherein the cathode delivers a specific capacity of 200 milliampere hour per gram over 665 discharge/charge cycles, while existing cathodes achieve only ~50 milliampere hour per gram and ~100 cycles. A highly conductive ruthenium-based composite is designed as a carbon-free cathode by first-principles calculations to avoid the degradation associated with carbonaceous materials, implying an improvement in stability during the electrochemical cycling. In addition, water vapor is added into the main oxygen gas as an additive to change the discharge product from growth-restricted lithium peroxide to easily grown lithium hydroxide, resulting in a notable increase in capacity. Thus, the proposed strategy is effective for developing reversible solid-state lithium-oxygen batteries with high energy density.

Ionic thermoelectrics show great potential in thermal sensing owing to their ultrahigh thermopower, low cost, and ease in production. However, the lack of effective n-type ionic thermoelectric materials seriously hinders their applications. Here, we report giant and bidirectionally tunable thermopowers within an ultrawide range from −15 to +17 mV K−1 in solid ionic liquid–based ionogels. Particularly, a record high negative thermopower of −15 mV K−1 is achieved in the ternary ionogel, rendering it among the best n-type ionic thermoelectric materials under the same condition. A thermopower regulation strategy through ion doping to selectively induce ion aggregates to enhance ion-ion interactions is proposed. These selective ion interactions are found to be decisive in modulating the sign and magnitude of the thermopower in the ionogels. A prototype wearable device integrated with 12 p-n pairs is demonstrated with a total thermopower of 0.358 V K−1, showing promise for ultrasensitive thermal detection.

Bioinspired control of ion transport at the subnanoscale has become a major focus in the fields of nanofluidics and membrane separation. It is fundamentally important to achieve rectifying ion-specific transport in artificial ion channels, but it remains a challenge. Here, we report a previously unidentified metal-organic framework nanochannel (MOF NC) nanofluidic system to achieve unidirectional ultrafast counter-directional transport of alkaline metal ions and proton. This highly effective ion-specific rectifying transport behavior is attributed to two distinct mechanisms for metal ions and proton, elucidated by theoretical simulations. Notably, the MOF NC exhibits ultrafast proton conduction stemming from ultrahigh proton mobility, i.e., 11.3 × 10-7 m2 /V·s, and low energy barrier of 0.075 eV in MIL-53-COOH subnanochannels. Furthermore, the MOF NC shows excellent osmotic power-harvesting performance in reverse electrodialysis. This work expects to inspire further research into multifunctional biomimetic ion channels for advanced nanofluidics, biomimetics, and separation applications.

Oxide ceramics are considered to be nonconductive brittle materials, which limits their applications in emerging fields such as conductive textiles. Here, we show a facile domino-cascade reduction method that enables rapid transformation of ceramic nanofiber textiles from insulation to conduction at room temperature. After putting dimethylacetamide-wetted textiles, including TiO2, SnO2, BaTiO3, and Li0.33La0.56TiO3, on lithium plates, the self-driven chemical reactions induce defects in oxides. These defects initiate an interfacial insulation-to-conductive phase transition, which triggers the domino-cascade reduction from the interface to the whole textile. Correspondingly, the conductivity of the textile sharply increased from 0 to 40 S/m over a period of 1 min. The modified oxide textiles exhibit enhanced electrochemical performance when substituting the metallic current collectors of lithium batteries. This room temperature reduction method can protect the nanostructures while inducing defects in oxide ceramic textiles, appealing for numerous applications.