High-Sulfur-Content Graphene-Based Composite through Ethanol Evaporation for High-Energy Lithium-Sulfur Battery

Sustainable Synthesis of Sulfur-Single Walled Carbon Nanohorns Composite for Long Cycle Life Lithium-Sulfur Battery

Lithium-sulfur batteries are considered one of the most appealing technologies for next-generation energy-storage devices. However, the main issues impeding market breakthrough are the insulating property of sulfur and the lithium-polysulfide shuttle effect, which cause premature cell failure. To face this challenge, we employed an easy and sustainable evaporation method enabling the encapsulation of elemental sulfur within carbon nanohorns as hosting material. This synthesis process resulted in a morphology capable of ameliorating the shuttle effect and improving the electrode conductivity. The electrochemical characterization of the sulfur-carbon nanohorns active material revealed a remarkable cycle life of 800 cycles with a stable capacity of 520 mA h/g for the first 400 cycles at C/4, while reaching a value around 300 mAh/g at the 750th cycle. These results suggest sulfur-carbon nanohorn active material as a potential candidate for next-generation battery technology.

A Lithium-Sulfur Battery Using Binder-Free Graphene-Coated Aluminum Current Collector

Lithium-sulfur battery of practical interest requires thin-layer support to achieve acceptable volumetric energy density. However, the typical aluminum current collector of Li-ion battery cannot be efficiently used in the Li/S system due to the insulating nature of sulfur and a reaction mechanism involving electrodeposition of dissolved polysulfides. We study the electrochemical behavior of a Li/S battery using a carbon-coated Al current collector in which the low thickness, the high electronic conductivity, and, at the same time, the host ability for the reaction products are allowed by a binder-free few-layer graphene (FLG) substrate. The FLG enables a sulfur electrode having a thickness below 100 μm, fast kinetics, low impedance, and an initial capacity of 1000 mAh g_S ^-1 with over 70% retention after 300 cycles. The Li/S cell using FLG shows volumetric and gravimetric energy densities of 300 Wh L^-1 and 500 Wh kg^-1, respectively, which are values well competing with commercially available Li-ion batteries.

Few-Layers Graphene-Based Cement Mortars: Production Process and Mechanical Properties

Cement is the most-used construction material worldwide. Research for sustainable cement production has focused on including nanomaterials as additives to enhance cement performance (strength and durability) in recent decades. In this concern, graphene is considered one of the most promising additives for cement composites. Here, we propose a novel technique for producing few-layer graphene (FLG) that can fulfil the material demand for the construction industry. We produced specimens with different FLG loadings (from 0.05% to 1% by weight of cement) and curing processes (water and saturated air). The addition of FLG at 0.10% by weight of cement improved the flexural strength by 24% compared to the reference (bare) sample. Similarly, a 0.15% FLG loading by weight of cement led to an improvement in compressive strength of 29% compared to the reference specimen. The FLG flakes produced by our proposed methodology can open the door to their full exploitation in several cement mortar applications, such as cementitious composites with high durability, mechanical performance and high electrical conductivity for electrothermal applications.

Solution-processed two-dimensional materials for next-generation photovoltaics

In the ever-increasing energy demand scenario, the development of novel photovoltaic (PV) technologies is considered to be one of the key solutions to fulfil the energy request. In this context, graphene and related two-dimensional (2D) materials (GRMs), including nonlayered 2D materials and 2D perovskites, as well as their hybrid systems, are emerging as promising candidates to drive innovation in PV technologies. The mechanical, thermal, and optoelectronic properties of GRMs can be exploited in different active components of solar cells to design next-generation devices. These components include front (transparent) and back conductive electrodes, charge transporting layers, and interconnecting/recombination layers, as well as photoactive layers. The production and processing of GRMs in the liquid phase, coupled with the ability to "on-demand" tune their optoelectronic properties exploiting wet-chemical functionalization, enable their effective integration in advanced PV devices through scalable, reliable, and inexpensive printing/coating processes. Herein, we review the progresses in the use of solution-processed 2D materials in organic solar cells, dye-sensitized solar cells, perovskite solar cells, quantum dot solar cells, and organic-inorganic hybrid solar cells, as well as in tandem systems. We first provide a brief introduction on the properties of 2D materials and their production methods by solution-processing routes. Then, we discuss the functionality of 2D materials for electrodes, photoactive layer components/additives, charge transporting layers, and interconnecting layers through figures of merit, which allow the performance of solar cells to be determined and compared with the state-of-the-art values. We finally outline the roadmap for the further exploitation of solution-processed 2D materials to boost the performance of PV devices.

Engineering Functional Interface with Built-in Catalytic and Self-Oxidation Sites for Highly Stable Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have attracted great attention due to their high theoretical energy density. The rapid redox conversion of lithium polysulfides (LiPS) is effective for solving the serious shuttle effect and improving the utilization of active materials. The functional design of the separator interface with fast charge transfer and active catalytic sites is desirable for accelerating the conversion of intermediates. Herein, a graphene-wrapped MnCO₃ nanowire (G@MC) was prepared and utilized to engineer the separator interface. G@MC with active Mn²⁺ sites can effectively anchor the LiPS by forming the Mn-S chemical bond according to our theoretical calculation results. In addition, the catalytic Mn²⁺ sites and conductive graphene layer of G@MC could accelerate the reversible conversion of LiPS via the spontaneous "self-redox" reaction and the rapid electron transfer in electrochemical process. As a result, the G@MC-based battery exhibits only 0.038 % capacity decay (per cycle) after 1000 cycles at 2.0 C. This work affords new insights for designing the integrated functional interface for stable Li-S batteries.

Simple and Sustainable Preparation of Nonactivated Porous Carbon from Brewing Waste for High-Performance Lithium-Sulfur Batteries

The development of renewable energy sources requires the parallel development of sustainable energy storage systems because of its noncontinuous production. Even the most-used battery on the planet, the lithium-ion battery, is reaching its technological limit. In light of this, lithium-sulfur batteries have emerged as one of the most promising technologies to address this problem. The use of biomass to produce cathodes for these batteries addresses not only the aforementioned problem, but it also reduces the carbon footprint and gives added value to something normally considered waste. Here, the production, by simple and nonactivating pyrolysis, of a carbon material using the abundant "after-boiling waste" derived from beer brewing is reported. After adding a high sulfur loading (70 %) to this biowaste-derived carbon by the "melt diffusion" method, the sulfur-carbon composite is used as an effective cathode in Li-S batteries. The cathode shows excellent performance, reaching high capacity values with long-term cyclability at high current-847 mAh g^-1 at 1 C, 586 mAh g^-1 at 2 C, and even 498 mAh g^-1 at 5 C after 400 cycles-drastically reducing capacity loss to values approaching 0.01 % per cycle. This work demonstrates the possibility of obtaining low-cost, highly sustainable cathodic materials for the design of advanced energy storage systems.