more stable interface against Li metal among SSEs. [3][4][5][6] The latter opens the door for safe use of Li metal anodes that have a high theoretical capacity (3860 mAh g −1 ) and a lowest electrochemical potential (−3.04 V vs standard hydrogen electrode), which is expected to maximize the energy-density advantage of SSLBs. [7] However, the large interfacial resistance between the rigid garnet solids and Li metal anodes is a huge challenge for fabricating high-performance SSLBs. [5,8] Although high-pressure treatment or vacuum evaporation have been used to deposit Li metal onto garnet solid to minimize the interfacial resistance, their complicated operations and procedures greatly limit the technological applications. Currently, melting Li metal integrated with garnet electrolytes, with the assistance of an intermediate layer between the garnet and Li metal, has been widely reported to overcome the lithiophobicity of garnet and consequently facilitated the interfacial resistance. [5] The intermediate layers mainly include Al 2 O 3 , Si, Au, Sn, ZnO, and polymers. [9][10][11][12][13][14] Although the interfacial resistance has been significantly decreased, numerous SSLBs reported to date are still unable to operate at high current densities (generally less than 0.5 mA cm −2 , see Table S1, Supporting Information), which would specifically inhibit the practical applications in power backups, portable power tools, or electric vehicles require much higher power densities. The poor power density of SSLBs is still neglected by battery community to date, at least, the current state-of-the-art interfacial modification strategies is a key bottleneck for the high-power SSLBs. The intermediate layers without sufficient ionic conductivity, such as Al 2 O 3 , ZnO, and polymers, may result in a unfavorable polarization resistance during operation under high current density, [9,15,16] while the other intermediate layers like Au and Sn are electronically conducting, [10,11,17] thus tending to result in Li penetration across the layer. And even worse, volume changes are inevitable when lithiating these inorganic layers with molten Li metal through the alloying-conversion reactions. [10] An ideal intermediate layer should, in principle, not only change the garnet from lithiophobic to lithiophilic, and also could be a fast and stable Li + conducting interphase when operating under high rate conditions.

Ultrathin, ultrastrong, and highly conductive solidstate polymer-based composite electrolytes have long been exploited for the next-generation lithium-based batteries. In particular, the lightweight membranes that are less than tens of microns are strongly desired, aiming to maximize the energy densities of solidstate batteries. However, building such ideal membranes are challenging when using traditional materials and fabrication technologies. Here we reported a 7.1 μm thick heterolayered Kevlar/covalent organic framework (COF) composite membrane fabricated via a bottom-up spin layer-by-layer assembly technology that allows for precise control over the structure and thickness of the obtained membrane. Much stronger chemical/mechanical interactions between cross-linked Kevlar and conductive 2D-COF building blocks were designed, resulting in a highly strong and Li + conductive (1.62 × 10 −4 S cm −1 at 30 °C and 4.6 × 10 −4 S cm −1 at 70 °C) electrolyte membrane that can prevent solid-state batteries from short-circuiting after over 500 h of cycling. All-solidstate lithium batteries using this membrane enable a significantly improved energy density.

We report the rational design and implementation of a new class of gel guest-assisted, ionic covalent organic framework (COF) membranes that exhibit superior H+ conduction. The as-synthesized COFs are postmodified via a lithiation (or sodiation) treatment. The hydrophilic Li or Na ions in the COFs form a dense and extensive hydrogen-bonding network of H2O molecules with mobile H+ at the periphery, thereby transforming COFs into H+ conductors. Then, the ionic COFs are assembled into a flexible H+ conductor membrane via a gelation process, where the organic gel provides both mechanical strength and additional H+ carriers for fast H+ conduction. The final COF-based membrane exhibits an excellent H+ conductivity of 1.3 × 10–1 S cm–1 at 313 K and 98% relative humidity, which are the highest values of the COF-based H+ conductors reported until now and are even comparable with those of the typical commercial Nafion membrane. We anticipate that the two-in-one strategy would open up a porous COF-driven new molecular framework and membrane architectural design/opportunity for development of next-generation ionic conductors.

the halide anion-based AIBs. [3] As alternatives of anion sources in AIBs, the polyatomic anions (e.g., ClO 4 − , TFSI − , SO 4 2− , etc.) with larger volumes are more gentle compared to the aggressive halideanions. [6][7][8] Besides, they possess a lower charge density than the highly polarizing metal-cations (Scheme 1a) and, thus, may afford a greater mobility in electrolytes. [9][10][11][12] Although these characteristics make polyatomic anions to be attractive carrier candidates to fabricate stable and high-rate AIBs, two major challenges remain. One is a lack of suitable electrode to steadily host the polyatomic anions that are several times larger than typical cations, Scheme 1a; [1] the other one is the low anionic capacities (generally <100 mAh g −1 ) of corresponding electrodes, owing to the sharply increased mass of polyatomic anion itself (see Table S1, Supporting Information). [4] The latter one has led to low energy density of the electrodes, even though the anion intercalation occurred at relatively high potential. As a result, the AIBs have been basically excluded from the increasing demand of highenergy applications.Such intrinsic low-energy density of the polyatomic anionbased electrodes cannot be raised by kinetics-induced capacity improvement through well-recognized nanostructured strategies. [13] As a solution, in this work, anion-storable frameworks are combined with Li + or Na + -storing units to assemble a porous covalent organic polymer (COP), aiming to provideThe low capacity of current anion-hosting electrodes makes it challenging to meet future energy requirements. Maintaining the high capacity of ions per unit volume and/or weight is always the ultimate goal for an optimal electrode design. Here, an organic framework is reported that can efficiently co-store anions and cations in a single discharge/charge process, accompanied with a special cation-assisted electrode activation process. The inserted cations not only facilitate anion diffusion kinetics, but also make a considerable contribution to the total capacity of the electrodes. This anion-cation costorage cathode thus can deliver a high capacity of 530 mAh g −1 at 3.4-1.0 V and a high energy density of 901 Wh kg −1 after 800 cycles (at 0.15 A g −1 ). The understanding of the self-activation process is expected to inspire electrode design that utilizes anionic-cationic hybrid electrode chemistries beyond current Li-ion batteries.