Solvation Engineering via Fluorosurfactant Additive Toward Boosted Lithium-Ion Thermoelectrochemical Cells

Lithium-ion thermoelectrochemical cell(LTEC), featuring simultaneous energy conversion and storage, has emerged as promising candidate for low-grade heat harvesting. However, relatively poor thermosensitivity and heat-to-current behavior limit the application of LTECs using LiPF_6 electrolyte. Introducing additives into bulk electrolyte is a reasonable strategy to solve such problem by modifying the solvation structure of electrolyte ions. In this work, we develop a dual-salt electrolyte with fluorosurfactant(FS) additive to achieve high thermopower and durability of LTECs during the conversion of low-grade heat into electricity. The addition of FS induces a unique Li~+ solvation with the aggregated double anions through a crowded electrolyte environment,resulting in an enhanced mobility kinetics of Li~+ as well as boosted thermoelectrochemical performances. By coupling optimized electrolyte with graphite electrode, a high thermopower of 13.8 mV K^(-1) and a normalized output power density of 3.99 mW m^(–2) K^(–2) as well as an outstanding output energy density of 607.96 J m^(-2) can be obtained.These results demonstrate that the optimization of electrolyte by regulating solvation structure will inject new vitality into the construction of thermoelectrochemical devices with attractive properties.

Regulating the Solvation Structure of Li^(+) Enables Chemical Prelithiation of Silicon-Based Anodes Toward High-Energy Lithium-Ion Batteries

The solvation structure of Li^(+) in chemical prelithiation reagent plays a key role in improving the low initial Coulombic efficiency(ICE) and poor cycle performance of silicon-based materials. Never theless, the chemical prelithiation agent is difficult to dope active Li^(+) in silicon-based anodes because of their low working voltage and sluggish Li^(+) diffusion rate. By selecting the lithium–arene complex reagent with 4-methylbiphenyl as an anion ligand and 2-methyltetrahydrofuran as a solvent, the as-prepared micro-sized Si O/C anode can achieve an ICE of nearly 100%. Interestingly, the best prelithium efficiency does not correspond to the lowest redox half-potential(E_(1/2)), and the prelithiation efficiency is determined by the specific influencing factors(E_(1/2), Li^(+) concentration, desolvation energy, and ion diffusion path). In addition, molecular dynamics simulations demonstrate that the ideal prelithiation efficiency can be achieved by choosing appropriate anion ligand and solvent to regulate the solvation structure of Li^(+). Furthermore, the positive effect of prelithiation on cycle performance has been verified by using an in-situ electrochemical dilatometry and solid electrolyte interphase film characterizations.

Targeted Deposition in a Lithiophilic Silver-Modified 3D Cu Host for Lithium-Metal Anodes

Lithium-metal batteries are regarded as the"Holy Grail"of next-generation batteries.However,lithium dendrite and anode volume expansion in cycles seriously hinders lithium-metal battery applications.Herein,we propose a precise and efficient strategy for stabilizing lithium-metal batteries via a lithiophilic Ag-modified Cu current host(Li@CuM/Ag).By applying the magnetron sputtering method,the lithiophilic silver layer can be anchored homogeneously on the Cu mesh.The lithiophilic silver layer effectively guides uniform Li deposition in the 3D host and realizes spatial control over Li nucleation.In addition,a dendrite-free lithium anode is successfully realized,which has been proven by in situ optical dynamic tests and Li deposition simulations.The symmetrical cell can maintain a low overpotential(230 mV)and long cycle life(90 h)at a large current of 10 mA cm^(-2)for a plating amount of 3 mAh cm^(-2).Furthermore,Li@CuM/Ag||LiCoO2 cells exhibited a high-capacity retention rate(86.39%)after 150 cycles at 2 C.Lithiophilic hosts based on magnetron sputtering provide a feasible strategy for applications of lithium-metal batteries.

Thermally Chargeable Proton Capacitor Based on Redox-Active Effect for Energy Storage and Low-Grade Heat Conversion

Thermal energy is abundantly available in our daily life and industrial production,and especially,low-grade heat is often regarded as a byproduct.Collecting and utilizing this ignored energy by low-cost and simple technologies may become a smart countermeasure to relieve the energy crisis.Here,a unique device has been demonstrated to achieve high value-added conversion of low-grade heat by introducing redox-active organic alizarin(AZ)onto N-doped hollow carbon nanofibers(N–HCNF)surface.As-prepared N–HCNF/AZ can deliver a high specific capacitance of 514.3 F g^(-1)(at 1 A g^(-1))and an outstanding rate capability of 60.3%even at 50 A g^(-1).Meanwhile,the assembled symmetric proton capacitor can deliver a high energy density of 28.0 Wh kg^(-1) at 350.0 W kg^(-1) and a maximum power density of 35.0 kW kg^(-1) at 17.0 Wh kg^(-1).Significantly,the thermally chargeable proton capacitors can attain a surprisingly high Seebeck coefficient of 15.3 mV K^(-1) and a power factor of 6.02µW g^(-1).Taking advantage of such high performance,a satisfying open-circuit voltage of 481.0 mV with a temperature difference of 54 K is achieved.This research provides new insights into construction of high value-added energy systems requiring high electrochemical performances.

Nanohollow Carbon for Rechargeable Batteries:Ongoing Progresses and Challenges

Among the various morphologies of carbon-based materials,hollow carbon nanostructures are of particular interest for energy storage.They have been widely investigated as electrode materials in different types of rechargeable batteries,owing to their high surface areas in association with the high surface-to-volume ratios,controllable pores and pore size distribution,high electrical conductivity,and excellent chemical and mechanical stability,which are beneficial for providing active sites,accelerating electrons/ions transfer,interacting with electrolytes,and giving rise to high specific capacity,rate capability,cycling ability,and overall electrochemical performance.In this overview,we look into the ongoing progresses that are being made with the nanohollow carbon materials,including nanospheres,nanopolyhedrons,and nanofibers,in relation to their applications in the main types of rechargeable batteries.The design and synthesis strategies for them and their electrochemical performance in rechargeable batteries,including lithium-ion batteries,sodium-ion batteries,potassium-ion batteries,and lithium–sulfur batteries are comprehensively reviewed and discussed,together with the challenges being faced and perspectives for them.

Two new compounds from Zingiber officinale

A new cyclic diarylheptanoid, 1,5-epoxy-3-hydroxy-1-（3-methoxy-4,5-dihydroxyphenyl）-7-（4-hydroxyphenyl）-heptane （1）, as well as a new monoterpene, 10-O-β-n-glucopyranosyl-hydroxy cineole （2） were isolated from the rhizomes of Zingiber officinale. The structures of compounds 1 and 2 were established based on their spectral data. In addition, the antioxidant activities of these compounds were also measured.

Three new diarylheptanoids and their antioxidant property

Three new diarylheptanoids, i.e., sodium（5S,2E）- 1,7-bis（4-hydroxyphenyl）- 1-hydroxy-2-hepten-5 -sulfonate （1）, sodium（5R,2E）-1,7-bis（4-hydroxyphenyl）-1-hydroxy-2-hepten-5-sulfonate （2） and 3,5-diacetoxy-1-（3-methoxy-4,5-dihydroxyphenyl）-7-（4-hydroxy-3-methoxyphenyl）heptane （3） were isolated from the rhizomes of Zingiber officinale. The structures of the new compounds were elucidated on the basis of spectroscopic methods. The antioxidant activities of 3 were assayed by in vitro models involving DPPH free radicals and superoxide anion radicals.

Dual-filler reinforced PVDF-HFP based polymer electrolyte enabling high-safety design of lithium metal batteries

Despite the high energy density of lithium metal batteries(LMBs),their application in rechargeable batteries is still hampered due to insufficient safety.Here,we present a novel flame-retardant solid-state electrolyte based on polyvinylidene fluoride-hexafluoropropylene(PVDF-HFP)with nano SiO_(2)aerogel as an inert filler but Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)as an auxiliary component to enhance the ion conductivity.The introduction of SiO_(2)aerogels imparts the polymer electrolyte with exceptional thermal stability and flame retardancy.Simultaneously,the interaction between hydroxyl groups of SiO_(2)particles and PVDF-HFP creates a strong cross-linking structure,enhancing the mechanical strength and stability of the electrolyte.Furthermore,the presence of SiO_(2)aerogel and LLZTO facilitates the dissociation of lithium salts through Lewis acid-base interactions,resulting in a high ionic conductivity of 1.01×10^(−3)S·cm^(−1)and a wide electrochemical window of~5.0 V at room temperature for the prepared electrolytes.Remarkably,the assembled Li|Li cell demonstrates the excellent resistance to lithium dendrite and runs stablly for over 1500 h at a current density of 0.25 mA·cm^(−2).Thus,we prepare a pouch cell with high safety,which can work normally after short-circuiting under the external folding and cutting.

Absorption mechanism of carbon-nanotube paper- titanium dioxide as a multifunctional barrier material for lithium-sulfur batteries

Lithium-sulfur batteries attract much interest as energy storage devices for their low cost, high specific capacity, and energy density. However, the insulating properties of sulfur and high solubility of lithium polysulfides decrease the utilization of active materials by the battery resulting in poor cycling performance. Herein, we design a multifunctional carbon-nanotube paper/titanium-dioxide barrier which effectively reduces active material loss and suppresses the diffusion of lithium polysulfides to the anode, thereby improving the cycling stability of lithium-sulfur batteries. Using this barrier, an activated carbon/sulfur cathode with 70% sulfur content delivers stable cycling performance and high Coulombic efficiency （-99%） over 250 cycles at a current rate of 0.5 C. The improved electrochemical performance is attributed to the synergistic effects of the carbon nanotube paper and titanium dioxide, involving the physical barrier, chemical adsorption from the binding formation of Ti-S and S-O, and other interactions unique to the titanium dioxide and sulfur species.

2020 roadmap on pore materials for energy and environmental applications

Porous materials have attracted great attention in energy and environment applications,such as metal organic frameworks(MOFs),metal aerogels,carbon aerogels,porous metal oxides.These materials could be also hybridized with other materials into functional composites with superior properties.The high specific area of porous materials offer them the advantage as hosts to conduct catalytic and electrochemical reactions.On one hand,catalytic reactions include photocatalytic,p ho toe lectrocatalytic and electrocatalytic reactions over some gases.On the other hand,they can be used as electrodes in various batteries,such as alkaline metal ion batteries and electrochemical capacitors.So far,both catalysis and batteries are extremely attractive topics.There are also many obstacles to overcome in the exploration of these porous materials.The research related to porous materials for energy and environment applications is at extremely active stage,and this has motivated us to contribute with a roadmap on ’porous materials for energy and environment applications’.

Recent advances and perspectives on prelithiation strategies for lithium-ion capacitors

Lithium-ion capacitors(LICs),consisting of a capacitor-type material and a battery-type material together with organic electrolytes,are the state-of-the-art electrochemical energy storage devices compared with supercapacitors and batteries.Owing to their unique characteristics,LICs received a lot of attentions,and great progresses have been achieved,especially in the exploration of cathode and anode materials.Prelithiation techniques are regarded as indispensable procedures for LICs systems,which can compensate for the initial irreversible capacity loss,increase the Li^(+)concentration in the electrolyte,raise the working voltage and resolve the safety and cycle stability issues;however,its research progress is slow,and there is not enough attention until now.In this overview,we look into the ongoing processes on the recent development of prelithiation technologies,especially in organic electrolyte consumption-type LICs.In particular,some prelithiation strategies for LICs are summarized and discussed in detail,including the ex situ electrochemical method,in situ electrochemical method,and cathode prelithiation additives method.Moreover,we propose some unresolved challenges and prospects for prelithiation technologies from the basic research ideas and future key research directions.This work aims to bring up new insights to reassess the significance of premetallation strategies for advanced hybrid-ion capacitors based on the currently proposed prelithiation strategies.

B-doped SiO_(x) composite with three dimensional conductive network for high performance lithium-ion battery anode

Currently,the practical application of SiO_(x) still has a huge hindrance in the area of lithium ion battery,because it is unable to achieve an effective contact with surrounding conducting materials,resulting in failure to form lithium ion migration tunnels.In this work,we presented a facile method to synthesize the B-doped SiOx composite by adhering SiO_(x) particles with MWCNT(multi-walled carbon nanotube)under the assistance of lithium metaborate(LiBO_(2)).LiBO_(2),as a sintering aid,not only can react with SiO_(x) to form a compacted framework,but also build a three-dimensional(3D)conductive network for ions transportation.Furthermore,B-SiO_(x)@CNT@LBO anode delivers a remarkable lithium storage performance in terms of long cycles and high rate capability.A full cell coupled with NCM622 cathode achieves a high energy density of 429.5 Wh kg^(-1) based on the total mass of cathode.

Boron and nitrogen dual-doped carbon as a novel cathode for high performance hybrid ion capacitors

Hybrid ion capacitors have been considered as a very attractive energy source with high energy density and power density since it combines both merits of lithium ion batteries and supercapacitors. However,their commercial application has been limited by the mismatch of charge-storage capacity and electrode kinetics between the capacitor-type cathode and battery-type anode. Herein, B and N dual-doped 3D superstructure carbon cathode is prepared through a facile template method. It delivers a high specific capacity, excellent rate capability and good cycling stability due to the B, N dual-doping, which has a profound effect in control the porosity, functional groups, and electronic conductivity for the carbon cathode. The hybrid ion capacitors using B, N dual-doping carbon cathode and prelithiated graphite anode show a high energy density of 115.5 Wh/kg at 250 W/kg and remain about 53.6 Wh/kg even at a high power density of 10 kW/kg. Additionally, the novel hybrid device achieves 76.3% capacity retention after 2000 cycles tested at 1250 W/kg power density. Significantly, the simultaneous manipulation of heteroatoms in carbon materials provides new opportunities to boost the energy and power density for hybrid ion capacitors.

An online electricity cost budgeting algorithm for maximizing green energy usage across data centers

With the sky-rocketing development of Internet services, the power usage in data centers has been signifi- cantly increasing. This ever increasing energy consumption leads to negative environmental impact such as global warming. To reduce their carbon footprints, large Internet service operators begin to utilize green energy. Since green energy is currently more expensive than the traditional brown one, it is important for the operators to maximize the green en- ergy usage subject to their desired long-term （e.g., a month） cost budget constraint. In this paper, we propose an online algorithm GreenBudget based on the Lyapunov optimization framework. We prove that our algorithm is able to achieve a delicate tradeoff between the green energy usage and the en- forcement of the cost budget constraint, and a control parameter V is the knob to arbitrarily tune such a tradeoff. We evaluate GreenBudget utilizing real-life traces of user requests, cooling efficiency, electricity price and green energy avail- ability. Experimental results demonstrate that under the same cost budget constraint, GreenBudget can increase the green energy usage by 11.55% compared with the state-of-the-art work, without incurring any performance violation of user requests.