Gas treatment protection of metallic lithium anode

The effects of different coating layers on lithium metal anode formed by reacting with different controlled atmospheres（argon,CO_2–O_2（2：1）,N_2,and CO_2–O_2–N_2（2：1：3））have been investigated.The obtained XRD,second ion mass spectroscopy（SIMS）,and scanning probe microscope（SPM）results demonstrate the formation of coating layers composed of Li_2CO_3,Li_3N,and the mixture of them on lithium tablets,respectively.The Li/Li symmetrical cell and Li/S cell are assembled to prove the advantages of the protected lithium tablet on electrochemical performance.The comparison of SEM and SIMS characterizations before/after cycles clarifies that an SEI-like composition formed on the lithium tablets could modulate the interfacial stabilization between the lithium foil and the ether electrolyte.

A Mixed Ether Electrolyte for Lithium Metal Anode Protection in Working Lithium-Sulfur Batteries

Lithium-sulfur(Li-S) battery is considered as a promising energy storage system to realize high energy density.Nevertheless,unstable lithium metal anode emerges as the bottleneck toward practical applications,especially with limited anode excess required in a working full cell.In this contribution,a mixed diisopropyl ether-based(mixed-DIPE) electrolyte was proposed to effectively protect lithium metal anode in Li-S batteries with sulfurized polyacrylonitrile(SPAN) cathodes.The mixed-DIPE electrolyte improves the compatibility to lithium metal and suppresses the dissolution of lithium polysulfides,rendering significantly improved cycling stability.Concretely,Li | Cu half-cells with the mixed-DIPE electrolyte cycled stably for 120 cycles,which is nearly five times longer than that with routine carbonate-based electrolyte.Moreover,the mixedDIPE electrolyte contributed to a doubled life span of 156 cycles at 0.5 C in Li | SPAN full cells with ultrathin 50 μm Li metal anodes compared with the routine electrolyte.This contribution affords an effective electrolyte formula for Li metal anode protection and is expected to propel the practical applications of high-energy-density Li-S batteries.

Towards full demonstration of high areal loading sulfur cathode in lithium–sulfur batteries

Lithium–sulfur(Li–S)batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability.The cathode with high sulfur areal loading is vital for the practical applications of Li–S batteries with very high energy density.However,the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases.Herein,we used diameters of 5.0(D5)and 13.0(D13)mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading(4.5 mg cm^-2).The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large(D13)cathode.Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions,which results in inferior battery performance of the Li–S cell with large diameter cathode.This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading,carbon modified separators,organic electrolyte,and Li metal anode in a pouch cell,wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li–S battery.

Thin buffer layer assist carbon-modifying separator for long-life lithium metal anodes

The guided Li dendrite growth by carbon-modifying separator is believed to be an effective strategy for enhancing life of lithium metal batteries(LMBs).However,the weak adhesions,as well as the large interface impedance between the smooth separator and the carbon functional layer(CFL) lead to an easily peeling of the CFL after repetitive cycles.Herein,we propose a promising solution by an inserting thin buffer layer(TBL) to strengthen the adhesion between CFL and separator as a double modifying layer(C-TBL) of the LMBs separator,which greatly improves the stability of the CFL and provides an effective Li metal anode protection.Owing to the sufficient ionic conductivity,chemical stability and strong adhesion to the separator of the TBL,it can avoid the failure of the CFL functionality with small interface impedance.Moreover,the CFL effectively reduces localized flux of Li+ through its abundant pores.The Li/Li cell with C-TBL separator displays the Li dendrite-free and stable cycling performance for at least 1500 h.When LiFePO_(4)(LFP) is employed as the cathode electrode,the assembled full cell with C-TBL separator shows the excellent rate performance and outstanding cycling capability.Our study builds a stable Li+conducting "bridge" between the functional layer and the separator in stabilizing Li metal anode,and provides a fresh idea of the artificial separator of LMBs.

Multi-factor principle for electrolyte additive molecule design for facilitating the development of electrolyte chemistry

When I read the paper“Electrolytes enriched by potassium perfluorinated sulfonates for lithium metal batteries”from Prof.Jianmin Ma’s group,which was published in Science Bulletin(doi.org/10.1016/j.scib.2020.09.018),I felt excited as presented a multi-factor principle for applying potassium perfluorinated sulfonates to suppress the dendrite growth and protect the cathode from the viewpoint of electrolyte additives.The effects of these additives are revealed through experimental results,molecular dynamics simulations and first-principle calculations.Specifically,it involves the influence of additives on Li^(+)solvation structure,solid electrolyte interphase(SEI),Li growth and nucleation.Following the guidance of the multi-factor principle,every part of the additive molecule should be utilized to regulate electrolytes.This multifactor principle for electrolyte additive molecule design(EAMD)offers a unique insight on understanding the electrochemical behavior of iontype electrolyte additives on both the Li metal anode and high-voltage cathode.In these regards,I would be delighted to write a highlight for this innovative work and,hopefully,it may raise more interest in the areas of electrolyte additives.

Oxygenated carbon nitride-based high-energy-density lithium-metal batteries

Lithium(Li)-metal batteries with polymer electrolytes are promising for high-energy-density and safe energy storage applications.However,current polymer electrolytes suffer either low ionic conductivity or inadequate ability to suppress Li dendrite growth at high current densities.This study addresses both issues by incorporating two-dimensional oxygenated carbon nitride(2D OCN)into a polyvinylidene fluoride(PVDF)-based composite polymer electrolyte and modifying the Li anode with OCN.The OCN nanosheets incorporated PVDF electrolyte exhibits a high ionic conductivity(1.6×10^(-4)S cm^(-1)at 25℃)and Li+transference number(0.62),wide electrochemical window(5.3),and excellent fire resistance.Furthermore,the OCN-modified Li anode in situ generates a protective layer of Li_(3)N during cycling,preventing undesirable reactions with PVDF electrolyte and effectively suppressing Li dendrite growth.Symmetric cells using the upgraded PVDF polymer electrolyte and modified Li anode demonstrate long cycling stability over 2500 h at 0.1 mA cm^(-2).Full cells with a high-voltage LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)cathode exhibit high energy density and long-term cycling stability,even at a high loading of 8.2 mg cm^(-2).Incorporating 2D OCN nanosheets into the PVDF-based electrolyte and Li-metal anode provides an effective strategy for achieving safe and high-energy-density Li-metal batteries.

Electrolytes enriched by potassium perfluorinated sulfonates for lithium metal batteries

Lithium(Li) metal is widely considered as a promising anode for next-generation lithium metal batteries(LMBs) due to its high theoretical capacity and lowest electrochemical potential. However, the uncontrollable formation of Li dendrites has prevented its practical application. Herein, we propose a kind of multifunctional electrolyte additives(potassium perfluorinated sulfonates) from the multi-factor principle for electrolyte additive molecular design(EDMD) view to suppress the Li dendrite growth. The effects of these additives are revealed through experimental results, molecular dynamics simulations and firstprinciples calculations. Firstly, K^(+)can form an electrostatic shield on the surface of Li anode to prevent the growth of Li dendrites. Secondly, potassium perfluorinated sulfonates can improve the activity of electrolytes as co-conductive salts, and lower the electro-potential of Li nucleation. Thirdly, perfluorinated sulfonate anions not only can change the Li^(+)solvation sheath structure to decrease the desolvation energy barrier and increase the ion migration rate, but also can be partly decomposed to form the superior solid electrolyte interphase(SEI). Benefited from the synergistic effects, an outstanding cycle life over250 h at 1 m A cm^(-2) is achieved in symmetric Li||Li cells. In particular, potassium perfluorinated sulfonate additives(e.g., potassium perfluorohexyl sulfonate, denoted as K+PFHS) can also contribute to the formation of high-quality cathode electrolyte interphase(CEI). As a result, Li||LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2) full cells exhibit significantly enhanced cycling stability. This multi-factor principle for EDMD offers a unique insight on understanding the electrochemical behavior of ion-type electrolyte additives on both the Li metal anode and high-voltage cathode.