High-Rate Solid Polymer Electrolyte Based Flexible All-Solid-State Lithium Metal Batteries

A flexible poly­(vinylidene fluoride)-polyetherimide@poly­(ethylene glycol) (PVDF-PEI@PEG) solid composite polymer electrolyte is prepared by an in situ thermal curing approach. The homogeneous PVDF-PEI composite porous membrane with an optimized PVDF and PEI weight ratio increases the amorphous phase, while the fast lithium ion transport channels are formed through the filled PEG electrolytes. The optimized polymer electrolyte exhibits high ionic conductivity of 2.36 × 10–4 S cm–1 at 60 °C and lithium ion transference number of 0.578 as well as excellent electrochemical stability window of 5.5 V. Moreover, the superior stability toward lithium metal anode enables over 3600 h cycling of the Li//Li symmetric cell at 0.1 mA cm–2. In particular, the LiFePO4//Li battery delivers high specific capacities of 132.4 and 111.5 mAh g–1 with a retention of 86.6% and 85.9% after 200 cycles at 2 C and 100 cycles at 3 C rate under 60 °C, respectively, demonstrating the feasibility as an energy storage device with high rate capability

[RhCp*Cl₂]₂‑Catalyzed Directed <i>N</i>‑Boc Amidation of Arenes “on Water”

Rhodium­(III) catalysis “on water” is effective for directed C–H amidation of arenes. The catalytic process is promoted by OH groups present on the hydrophobic water surface and is inefficient in all (most) common organic solvents investigated so far. In the presence of easily prepared <i>tert</i>-butyl 2,4-dinitrophenoxycarbamate, a new and stable nitrene source, the “on water” reaction can efficiently provide the desired <i>N</i>-Boc-aminated products with good functional group tolerance

[RhCp*Cl₂]₂‑Catalyzed Directed <i>N</i>‑Boc Amidation of Arenes “on Water”

Rhodium­(III) catalysis “on water” is effective for directed C–H amidation of arenes. The catalytic process is promoted by OH groups present on the hydrophobic water surface and is inefficient in all (most) common organic solvents investigated so far. In the presence of easily prepared <i>tert</i>-butyl 2,4-dinitrophenoxycarbamate, a new and stable nitrene source, the “on water” reaction can efficiently provide the desired <i>N</i>-Boc-aminated products with good functional group tolerance

Rhodium-Catalyzed Selective Mono- and Diamination of Arenes with Single Directing Site “On Water”

A Rh­(III)-catalyzed selective C–H amination of 2-phenylpyridine derivatives is reported. With pyridine as a directing group, the reaction has high mono- or diamination selectivity, and a wide range of effective substrates, including electron-deficient and -rich aryl azides. Water helps to promote C–H activation, and the concept of a water promoted rollover mechanism is postulated for the diamination step. The reactions were conducted using a Schlenk flask and proceeded smoothly “on water” under atmospheric conditions with nitrogen gas as the only byproduct

Bimetallic Hexagonal Layered Ni–Co Sulfides with High Electrochemical Performance for All-Solid-State Lithium Batteries

All-solid-state lithium (Li) batteries have been emerging as attractive technologies for energy storage systems due to their benefits in safety. However, the electrochemical performance of all-solid-state Li batteries is limited by the interfacial problems resulting from the solid–solid contact between electrolytes and electrodes. Here, a binary transition-metal sulfide NixCo3–xS4 with a special hexagonal layered structure is synthesized and introduced into all-solid-state Li batteries based on sulfide electrolytes. By freely adjusting the Ni/Co ratio, components with optimal performance can be easily obtained. In addition, the well-designed interfacial structure is favorable for ion transport and interfacial stability because the sulfide electrolyte particles can rivet on the hexagonal platelets which can maximally reduce the contact resistance between the solid electrolytes and cathodes. As a result, the all-solid-state Li battery employing the Ni0.3Co2.7S4@Li7P3S11 composite cathode exhibits enhanced rate capability and cycling stability. At a current density of 0.1 A g–1, it delivers a specific capacity as high as 1216 mA h g–1. Even under a large current of 1 A g–1, a large capacity of 510 mA h g–1 can be retained after 100 cycles

Scalable Synthesis of TiO₂/Graphene Nanostructured Composite with High-Rate Performance for Lithium Ion Batteries

A simple and scalable method is developed to synthesize TiO₂/graphene nanostructured composites as high-performance anode materials for Li-ion batteries using hydroxyl titanium oxalate (HTO) as the intermediate for TiO₂. With assistance of a surfactant, amorphous HTO can condense as a flower-like nanostructure on graphene oxide (GO) sheets. By calcination, the HTO/GO nanocomposite can be converted to TiO₂/graphene nanocomposite with well preserved flower-like nanostructure. In the composite, TiO₂ nanoparticles with an ultrasmall size of several nanometers construct the porous flower-like nanostructure which strongly attached onto conductive graphene nanosheets. The TiO₂/graphene nanocomposite is able to deliver a capacity of 230 mA h g^–1 at 0.1 C (corresponding to a current density of 17 mA g^–1), and demonstrates superior high-rate charge–discharge capability and cycling stability at charge/discharge rates up to 50 C in a half cell configuration. Full cell measurement using the TiO₂/graphene as the anode material and spinel LiMnO₂ as the cathode material exhibit good high-rate performance and cycling stability, indicating that the TiO₂/graphene nanocomposite has a practical application potential in advanced Li-ion batteries

Wet-Milling Synthesis of Superionic Lithium Argyrodite Electrolytes with Different Concentrations of Lithium Vacancy

The ionic conductivities of argyrodite electrolytes are significantly affected by the concentrations of lithium vacancy. Herein, a facile and rapid synthesis route is proposed to systematically investigate Li6–xPS5–xCl1+x (0 ≤ x ≤ 0.8) with different lithium vacancies by adjusting ratios of S/Cl. The highest ionic conductivity of the wet-milling synthesized Li5.4PS4.4Cl1.6 is 6.18 mS cm–1, which is attributed to higher lithium vacancy concentration and lower electrostatic interaction for ion migration. The Li/Li5.4PS4.4Cl1.6/Li symmetric cell cycles stably for 2000 h at 0.1 mA cm–2, showing excellent dendrite suppression capability. Moreover, the initial discharge capacity of LiCoO2/Li5.4PS4.4Cl1.6/Li all-solid-state battery is 126.0 mAh g–1 at 0.1C and the capacity retention is 83% after 50 cycles. The wet-milling method provides the possibility for rapid exploration and preparation of other argyrodite electrolytes in the future

Expansion-Tolerant Lithium Anode with Built-In LiF-Rich Interface for Stable 400 Wh kg^–1 Lithium Metal Pouch Cells

Lithium metal anodes hold great promise for enabling high-energy density devices compared with the commercialized graphite electrode. However, huge pressure changes during cycling will lead to the pulverization of the 2D lithium anode, thus deteriorating the battery life due to its poor mechanical strength. Herein we report a 3D lithium–boron (LiB) fibrous framework with great compressive strength through electrochemical delithiation. The LiB alloy fibers with a 3D stable structure play the role of an expansion-tolerant substrate, which could effectively hold the Li metal and reduce the internal pressure changes, showing only a 53.7% pressure change compared with the 2D Li/Cu-anode-based pouch cell. A quasi-ionic-liquid-based polymer electrolyte layer is introduced by a scalable tape-casting method, generating a LiF-rich layer inside the 3D Li anode through the reaction between the polymer electrolyte and the internal free Li, which can guide the uniform nucleation and growth of Li metal. As a result, the asymmetric Li–Li cell can sustain 5 mAh cm–2 Li plating/stripping for 1000 h. A 2.1 Ah pouch cell coupling to a LiF-rich interface-protected 3D Li/LiB anode and a Ni-rich cathode of 30 mg cm–2 exhibits an ultrahigh energy density of 403 Wh kg–1 and a stable cycle life of 100 cycles

Understanding LiI-LiBr Catalyst Activity for Solid State Li₂S/S Reactions in an All-Solid-State Lithium Battery

Li||MoS2 solid-state batteries have higher volumetric energy density and power density than Li||Li2S batteries. However, they suffer from energy and power decay due to the formation of lithium sulfide that has low ionic/electronic conductivity and a strong Li–S bond. Herein, we overcome these challenges by incorporating the catalytic LiI-LiBr compound and carbon black into MoS2. The comprehensive simulations, characterizations, and electrochemical evaluations demonstrated that LiI-LiBr significantly reduces Li+/S2– interaction and increases the ionic conductivity of Li2S, thus enhancing the reaction kinetics and Li2S/S redox reversibility. MoS2@LiI-LiBr@C||Li cells with an areal capacity of 0.87 mAh cm–2 provide a reversible capacity of 816.2 mAh g–1 at 200 mA g–1 and maintain 604.8 mAh g–1 (based on the mass of MoS2) for 100 cycles. At a high areal capacity of 2 mAh cm–2, the battery still delivers reversible capacity of 498 mAh g–1. LiI-LiBr-carbon additive can be broadly applied for all transition-metal sulfide cathodes to enhance the cyclic and rate performance

Amorphous Titanium Polysulfide Composites with Electronic/Ionic Conduction Networks for All-Solid-State Lithium Batteries

All-solid-state lithium/sulfide batteries are considered as next-generation high-energy-density batteries with unrivaled safety. However, sulfide cathodes generally suffer from insulating properties and huge volume expansion in all-solid-state lithium batteries. Based on amorphous TiS4 (a-TiS4), a certain proportion of Super P is introduced to suppress the volume expansion and increase the electronic conductivity. Meanwhile, a Li7P3S11 solid electrolyte is in situ coated on the surface of 20% Super P/a-TiS4, and the close interfacial contact between the active material and the solid electrolyte constructs a favorable ionic conduction path. As a result, a Li/75% Li2S-24% P2S5-1% P2O5/Li10GeP2S12/20% Super P/a-TiS4@Li7P3S11 battery shows a high reversible capacity of 507.4 mAh g–1 after 100 cycles at 0.1 A g–1. Even the current density increases to 1.0 A g–1, and it can also provide a reversible capacity of 349.8 mAh g–1 after 200 cycles. These results demonstrate a promising 20% Super P/a-TiS4@Li7P3S11 cathode material with electronic/ionic conduction networks for all-solid-state lithium batteries