Diminishing Self-Discharge of High-Loading Li-S Batteries with Oxygen-rich Biomass Carbon Interlayers.

Lithium-sulfur batteries (Li-S) have possessed gratifying development in the past decade due to their high theoretical energy density. However, the severe polysulfide shuttling provokes undesirable self-discharge effect, leading to low energy efficiency in Li-S batteries. Herein, an interlayer composed of oxygen-rich carbon nanosheets (OCN) derived from bagasse is elaborated to suppress the shuttle effect and reduce the resultant self-discharge effect. The OCN interlayer is able to physically block the shuttling behavior of polysulfides and its oxygen-rich functional groups can strongly interact with polysulfides via O-S bonds to chemically immobilize mobile polysulfides. The self-discharge test for seven days further shows that the self-discahrge rate is diminished by impressive 93%. As a result, Li-S batteries with the OCN interlayer achieve an ultrahigh discharge specific capacity of 710 mAh g-1 at a high mass loading of 7.18 mg. The work provides a facile method for designing functional interlayers and opens a new avenue for realizing Li-S batteries with high energy efficiency.

In Situ Polymerization Facilitating Practical High-Safety Quasi-Solid-State Batteries.

Quasi-solid-state batteries (QSSBs) are gaining widespread attention as a promising solution to improve battery safety performance. However, the safety improvement and the underlying mechanisms of QSSBs remain elusive. Herein, a novel strategy combining high-safety ethylene carbonate-free liquid electrolyte and in situ polymerization technique is proposed to prepare practical QSSBs. The Ah-level QSSBs with LiNi0.83Co0.11Mn0.06O2 cathode and graphite-silicon anode demonstrate significantly improved safety features without sacrificing electrochemical performance. As evidenced by accelerating rate calorimetry tests, the QSSBs exhibit increased self-heating temperature and onset temperature (T2), and decreased temperature rise rate during thermal runaway (TR). The T2 has a maximum increase of 48.4 °C compared to the conventional liquid batteries. Moreover, the QSSBs do not undergo TR until 180 °C (even 200 °C) during the hot-box tests, presenting significant improvement compared to the liquid batteries that run into TR at 130 °C. Systematic investigations show that the in situ formed polymer skeleton effectively mitigates the exothermic reactions between lithium salts and lithiated anode, retards the oxygen release from cathode, and inhibits crosstalk reactions between cathode and anode at elevated temperatures. The findings offer an innovative solution for practical high-safety QSSBs and open up a new sight for building safer high-energy-density batteries.

Enabling Electrochemical-Mechanical Robustness of Ultra-High Ni Cathode via Self-Supported Primary-Grain-Alignment Strategy.

The electrochemical-mechanical degradation of ultrahigh Ni cathode for lithium-ion batteries is a crucial aspect that limits the cycle life and safety of devices. Herein, the study reports a facile strategy involving rational design of primary grain crystallographic orientation within polycrystalline cathode, which well enhanced its electro-mechanical strength and Li+ transfer kinetics. Ex situ and in situ experiments/simulations including cross-sectional particle electron backscatter diffraction (EBSD), single-particle micro-compression, thermogravimetric analysis combined with mass spectrometry (TGA-MS), and finite element modeling reveal that, the primary-grain-alignment strategy effectively mitigates the particle pulverization, lattice oxygen release thereby enhances battery cycle life and safety. Besides the preexisting doping and coating methodologies to improve the stability of Ni-rich cathode, the primary-grain-alignment strategy, with no foreign elements or heterophase layers, is unprecedently proposed here. The results shed new light on the study of electrochemical-mechanical strain alleviation for electrode materials.

A review on energy chemistry of fast-charging anodes.

With the impetus to accelerate worldwide market adoption of electrical vehicles and afford consumer electronics with better user experience, advancing fast-charging technology is an inevitable trend. However, current high-energy lithium-ion batteries are unable to support ultrafast power input without any adverse consequences, with the capacity fade and safety concerns of the mainstream graphite-based anodes being the key technological barrier. The aim of this review is to summarise the fundamentals, challenges, and solutions to enable graphite anodes that are capable of high-rate charging. First, we explore the complicated yet intriguing graphite-electrolyte interface during intercalation based on existing theories. Second, we analyse the key dilemmas facing fast-charging graphite anodes. Finally, some promising strategies proposed during the past few years are highlighted so as to outline current trends and future perspectives in this field.

Fast Charging Lithium Batteries: Recent Progress and Future Prospects.

Fast charging enables electronic devices to be charged in a very short time, which is essential for next-generation energy storage systems. However, the increase of safety risks and low coulombic efficiency resulting from fast charging severely hamper the practical applications of this technology. This Review summarizes the challenges and recent progress of lithium batteries for fast charging. First, it describes the definition of fast charging and proposes a critical value of ionic and electrical conductivity of electrodes for fast charging in a working battery. Then based on this definition, the requirements and optimization strategies of the electrode, electrolyte, and electrode/electrolyte interface for fast charging are proposed. Finally, a general conclusion and perspectives on the better understanding of lithium batteries with fast charging capability are presented.

A Single-Step Hydrothermal Route to 3D Hierarchical Cu2 O/CuO/rGO Nanosheets as High-Performance Anode of Lithium-Ion Batteries.

As anodes of Li-ion batteries, copper oxides (CuO) have a high theoretical specific capacity (674 mA h g-1 ) but own poor cyclic stability owing to the large volume expansion and low conductivity in charges/discharges. Incorporating reduced graphene oxide (rGO) into CuO anodes with conventional methods fails to build robust interaction between rGO and CuO to efficiently improve the overall anode performance. Here, Cu2 O/CuO/reduced graphene oxides (Cu2 O/CuO/rGO) with a 3D hierarchical nanostructure are synthesized with a facile, single-step hydrothermal method. The Cu2 O/CuO/rGO anode exhibits remarkable cyclic and high-rate performances, and particularly the anode with 25 wt% rGO owns the best performance among all samples, delivering a record capacity of 550 mA h g-1 at 0.5 C after 100 cycles. The pronounced performances are attributed to the highly efficient charge transfer in CuO nanosheets encapsulated in rGO network and the mitigated volume expansion of the anode owing to its robust 3D hierarchical nanostructure.

Enhanced photocurrent production by the synergy of hematite nanowire-arrayed photoanode and bioengineered Shewanella oneidensis MR-1.

Coupling the light-harvesting capabilities of semiconductors with the catalytic power of bacteria is a promising way to increase the efficiency of bioelectrochemical systems. Here, we reported the enhanced photocurrents produced by the synergy of hematite nanowire-arrayed photoanode and the bio-engineered Shewanella oneidensis MR-1 in a solar-assisted microbial photoelectrochemical system (solar MPS) under the visible light. To increase the supply of bioelectrons, the D-lactate transporter, SO1522, was overexpressed in the recombinant S. oneidensis (T-SO1522) that could digest D-lactate 61% faster than the wild-type S. oneidenesis. Without light illumination, the addition of either the wild-type or the recombinant S. oneidensis to the system did not induce any obvious increase in the current output. However, under one-sun illumination, the photocurrent of the abiotic control was 16±2 µA cm-2 at 0.8V vs. Ag/AgCl, and the addition of the wild-type S. oneidensis and the recombinant S. oneidensis increased the photocurrent to 70±6 and 95±8 µA cm-2, respectively, at 0.8V vs. Ag/AgCl. Moreover, the solar MPS with T-SO1522 presented quick and repeatable responses to the on/off illumination cycles, and had relatively stable photocurrent generation in the 273-h operation. Scanning electron microscope (SEM) images showed that the cell density on the hematite photoelectrode was similar between the recombinant and the wild-type S. oneidensis. These findings revealed the pronounced influence of metabolic rates on the light-to-electricity conversion in the complex photocatalyst-electricigen hybrid system, which is important to promote the development of the solar MPS for electricity production and wastewater treatment.

A novel moisture adjusted vegetation index (MAVI) to reduce background reflectance and topographical effects on LAI retrieval.

A new moisture adjusted vegetation index (MAVI) is proposed using the red, near infrared, and shortwave infrared (SWIR) reflectance in band-ratio form in this paper. The effectiveness of MAVI in retrieving leaf area index (LAI) is investigated using Landsat-5 data and field LAI measurements in two forest and two grassland areas. The ability of MAVI to retrieve forest LAI under different background conditions is further evaluated using canopy reflectance of Jack Pine and Black Spruce forests simulated by the 4-Scale model. Compared with several commonly used two-band vegetation index, such as normalized difference vegetation index, soil adjusted vegetation index, modified soil adjusted vegetation index, optimized soil adjusted vegetation index, MAVI is a better predictor of LAI, on average, which can explain 70% of variations of LAI in the four study areas. Similar to other SWIR-related three-band vegetation index, such as modified normalized difference vegetation index (MNDVI) and reduced simple ratio (RSR), MAVI is able to reduce the background reflectance effects on forest canopy LAI retrieval. MAVI is more suitable for retrieving LAI than RSR and MNDVI, because it avoids the difficulty in properly determining the maximum and minimum SWIR values required in RSR and MNDVI, which improves the robustness of MAVI in retrieving LAI of different land cover types. Moreover, MAVI is expressed as ratios between different spectral bands, greatly reducing the noise caused by topographical variations, which makes it more suitable for applications in mountainous area.

[Forest canopy leaf area index in Maoershan Mountain: ground measurement and remote sensing retrieval].

Leaf area index (LAI) is one of the most important structural parameters of terrestrial ecosystem, while the remote sensing retrieval and the ground optical instrument measurement and based on canopy gap model are the effective approaches to rapidly obtain LAI. However, these two approaches can only acquire effective LAI (LAI(e)), due to the clumping of vegetation canopy. Taking the experimental forest farm of Northeast Forestry University at Maoershan Mountain in Heilongjiang Province of Northeast China as study site, this paper measured the forest canopy LAI(e) by LAI2000, and estimated the LAI by the combination of TRAC (tracing radiation and architecture of canopies) measurement of foliage clumping index. A LAI remote sensing retrieval model was constructed through the analysis of the relationships between different vegetation indices calculated from Landsat5-TM and measured LAI(e). The results showed that at the study site, the LAI of broad leaved forests was close to the LAI(e), but the LAI of needle leaved forests was 27% larger than the LAI(e). Reduced simple ratio index (RSR) had the highest relationship with measured LAI(e) (R2 = 0.763, n = 23), which could be used as the best predictor of LAI. The LAI at study site increased rapidly with increasing elevation when the elevation was below 400 m, but had a slow increase when the elevation was from 400 m to 750 m. When the elevation was above 750 m, the LAI decreased. There was a significant correlation between the forest canopy LAI and aboveground biomass.