Quantum Spin Exchange Interactions to Accelerate the Redox Kinetics in Li–S Batteries

Spin-engineering with electrocatalysts have been exploited to suppress the“shuttle effect”in Li–S batteries.Spin selec-tion,spin-dependent electron mobility and spin potentials in activation barriers can be optimized as quantum spin exchange interactions lead-ing to a significant reduction of the electronic repulsions in the orbitals of catalysts.Herein,we anchor the MgPc molecules on fluorinated carbon nanotubes(MgPc@FCNT),which exhibits the single active Mg sites with axial displacement.According to the density functional theory calculations,the electronic spin polarization in MgPc@FCNT not only increases the adsorption energy toward LiPSs intermediates but also facilitates the tunneling process of electron in Li–S batter-ies.As a result,the MgPc@FCNT provides an initial capacity of 6.1 mAh cm^(-2) even when the high sulfur loading is 4.5 mg cm^(-2),and still maintains 5.1 mAh cm^(-2) after 100 cycles.This work provides a new perspective to extend the main group single-atom catalysts enabling high-performance Li–S batteries.

Rational design of Fe/Co-based diatomic catalysts for Li–S batteries by first-principles calculations

Fe/Co-based diatomic catalysts decorated on an N-doped graphene substrate are investigated by first-principles calculations to improve the electrochemical properties of Li–S batteries.Our results demonstrate that Fe CoN8@Gra not only possesses moderate adsorption energies towards Li2Snspecies,but also exhibits superior catalytic activity for both reduction and oxidation reactions of the sulfur cathode.Moreover,the metallic property of the diatomic catalysts can be well maintained after Li2Snadsorption,which could help the sulfur cathode to maintain high conductivity during the whole charge–discharge process.Given these exceptional properties,it is expected that Fe CoN8@Gra could be a promising diatomic catalyst for Li–S batteries and afford insights for further development of advanced Li–S batteries.

Ion shielding functional separator using halloysite containing a negative functional moiety for stability improvement of Li–S batteries

Lithium–sulfur batteries are one of the attractive next-generation energy storage systems owing to theienvironmental friendliness,low cost,and high specific energy densities.However,the low electrical conductivity of sulfur,shuttling of soluble intermediate polysulfides between electrodes,and low capacitretention have hampered their commercial use.To address these issues,we use a halloysitemodulated(H-M)separator in a lithium–sulfur battery to mitigate the shuttling problem.The H-M separator acts as a mutual Coulombic repulsion in lithium-sulfur batteries,thereby selectively permitting Lions and efficiently suppressing the transfer of undesired lithium polysulfides to the Li anode sideMoreover,the use of halloysite switches the surface of the separator from hydrophobic to hydrophilicconsequently improving the electrolyte wettability and adhesion between the separator and cathodeWhen sulfur-multi-walled carbon nanotube(S-MWCNT)composites are used as cathode active materialsa lithium–sulfur battery with an H-M separator exhibits first discharge and charge capacities of 1587 an1527 m Ah g-1,respectively.Moreover,there is a consistent capacity retention up to 100 cyclesAccordingly,our approach demonstrates an economical and easily accessible strategy for commercialization of lithium–sulfur batteries.

Recent advances in chemical adsorption and catalytic conversion materials for Li–S batteries

Owing to their low cost,high energy densities,and superior performance compared with that of Li-ion batteries,Li–S batteries have been recognized as very promising next-generation batteries.However,the commercialization of Li–S batteries has been hindered by the insulation of sulfur,significant volume expansion,shuttling of dissolved lithium polysulfides(Li PSs),and more importantly,sluggish conversion of polysulfide intermediates.To overcome these problems,a state-of-the-art strategy is to use sulfur host materials that feature chemical adsorption and electrocatalytic capabilities for Li PS species.In this review,we comprehensively illustrate the latest progress on the rational design and controllable fabrication of materials with chemical adsorbing and binding capabilities for Li PSs and electrocatalytic activities that allow them to accelerate the conversion of Li PSs for Li–S batteries.Moreover,the current essential challenges encountered when designing these materials are summarized,and possible solutions are proposed.We hope that this review could provide some strategies and theoretical guidance for developing novel chemical anchoring and electrocatalytic materials for high-performance Li–S batteries.

Microstructural analyses of all-solid-state Li–S batteries using LiBH4-based solid electrolyte for prolonged cycle performance

Complex hydride materials have been widely investigated as potential solid electrolytes because they have good compatibility with the lithium metal anodes used in all-solid-state batteries. However, the development of all-solid-state batteries utilizing complex hydrides has been difficult as these cells tend to have short cycle lives. This study investigated the capacity fading mechanism of all-solid-state lithium–sulfur(Li–S) batteries using Li4(BH4)3I solid electrolytes by analyzing the cathode microstructure. Crosssectional scanning electron microscopy observations after 100 discharge–charge cycles revealed crack formation in the Li4(BH4)3I electrolyte and an increased cathode thickness. Raman spectroscopy indicated that decomposition of the Li4(BH4)3I solid electrolyte occurred at a constant rate during the cycling tests.To combat these effects, the cycle life of Li–S batteries was improved by increasing the amount of solid electrolyte in the cathode.

Facile synthesis of Li2S@C composites as cathode for Li–S batteries

Lithium sulfide (Li2S) provides a promising route for lithium storage due to high theoretical specific capacity (1166 mAh g-1). The electrochemical performance of Li2S can be significantly enhanced by forming Li2S-carbon composites with the introduction of carbon. However, the complex synthesis method of Li2S-carbon composites restrains the large-scale productivity. Herein, we propose a facile route to prepare carbon coated Li2S-carbon nanotube composites (Li2S@C-CNT) via spray drying and heat treatment, which is a low-cost and large-scale method for facile synthesis of Li2S-carbon composites. For the Li2S@C-CNT composites, Li2S nanoparticles are contacted with surrounding particles due to the 3D CNTs framework. The novel construction not only suppresses the diffusion of polysulfides during cycling, but also remarkably accelerates the transport of electron and ion, resulting in a high specific capacity (1100 mAh g^-1) and good cycling performance. The rational designed architecture and good electrochemical performance of Li2S@C-CNT will pave the avenue for realizing high energy density of Li2S-based batteries.

Electrophoretically deposited binder-free 3-D carbon/sulfur nanocomposite cathode for high-performance Li–S batteries

In the present study,the electrophoretic deposition method was successfully applied as a binder-free and scalable approach to deposit carbonaceous nanomaterials on carbon fiber paper(CFP)for cathode applications in Li-S batteries.The microstructural studies of the EPD-CNT film using scanning electron microscopy(SEM)revealed the formation of a crack-free and porous layer of CNTs being uniformly distributed on the CFP surface.The EPD:CFP/CNT/S cathode delivered a capacity around 2.2 times higher than that obtained in the absence of the EPD-CNT film(CFP/S cell)after 50 cycles and a capacity of935 mAh g^-1 after 100 cycles at 0.1 C.The EPD method was then employed to fabricate layer-by-layer structures where the EPD-CNT film was decorated with carbon black particles.The initial capacity as well as the reversible capacity after 100 cycles was further increased by the EPD:CFP/CNT/KB/S layer-by-layer structure to 1473 and 1033 mAh g^-1,respectively,indicating effective suppression of the shuttle effect.In addition,the rate performance of CFP/S was improved by depositing the EPD-CNT and EPD-CNT/carbon black architectures on CFP surface,and even further enhanced through the co-deposition of CNT and Pt nanoparticles by EPD,delivering a specific capacity of around 730 mAh g^-1 at 1 C.Finally,the cathodes fabricated by EPD were observed to outperform those made by the conventional casting method in terms of cycling performance,internal resistance,and polarization.This difference was ascribed to the non-uniform microstructure of the Cast-CNT film,which resulted in poor interfacial connection between the CNT agglomerates,hindering uniform sulfide/sulfur deposition during cycling.The obtained results suggested that the binder-free C/S nanocomposite cathode made by EPD is key to further enhance the specific capacity and energy density of Li-S batteries.

Trend of Developing Aqueous Liquid and Gel Electrolytes for Sustainable,Safe,and High‑Performance Li‑Ion Batteries

Current lithium-ion batteries(LIBs)rely on organic liquid electrolytes that pose significant risks due to their flammability and toxicity.The potential for environmental pollution and explosions resulting from battery damage or fracture is a critical concern.Water-based(aqueous)electrolytes have been receiving attention as an alternative to organic electrolytes.However,a narrow electrochemicalstability window,water decomposition,and the consequent low battery operating voltage and energy density hinder the practical use of aqueous electrolytes.Therefore,developing novel aqueous electrolytes for sustainable,safe,high-performance LIBs remains challenging.This Review first commences by summarizing the roles and requirements of electrolytes–separators and then delineates the progression of aqueous electrolytes for LIBs,encompassing aqueous liquid and gel electrolyte development trends along with detailed principles of the electrolytes.These aqueous electrolytes are progressed based on strategies using superconcentrated salts,concentrated diluents,polymer additives,polymer networks,and artificial passivation layers,which are used for suppressing water decomposition and widening the electrochemical stability window of water of the electrolytes.In addition,this Review discusses potential strategies for the implementation of aqueous Li-metal batteries with improved electrolyte–electrode interfaces.A comprehensive understanding of each strategy in the aqueous system will assist in the design of an aqueous electrolyte and the development of sustainable and safe high-performance batteries.

Cage-confinement synthesis of MoC nanoclusers as efficient sulfiphilic and lithiophilic regulator for superior Li–S batteries

High-energy-density Li-S batteries are subjected to serious sulfur deactivation and short cycle lifetime caused by undesirable polysulfide shuttle effect and frantic lithium dendrite formation.In this work,a controllable cage-confinement strategy to fabricate molybdenum carbide(MoC)nanoclusters as a high-efficient sulfiphilic and lithiophilic regulator to mitigate the formidable issues of Li-S batteries is demonstrated.The sub-2 nm MoC nanoclusters not only guarantee robust chemisorption and fast electrocatalytic conversion of polysulfides to enhance the sulfur electrochemistry,but also homogenize Li^(+) flux to suppress the lithium dendrite growth.As a consequence,the MoC-modified separator endows the batteries with boosted reaction kinetics,promoted sulfur utilization,and improved cycling stability.A reversible capacity of 701 mAh·g^(−1) at a high rate of 5.0C and a small decay rate of 0.076%per cycle at 1.0C over 600 cycles are achieved.This study offers a rational route for design and synthesis of bifunctional nanoclusers with both sulfiphilicity and lithiophilicity for high-performance Li-S batteries.

Electrolyte Design for Low‑Temperature Li‑Metal Batteries:Challenges and Prospects

Electrolyte design holds the greatest opportunity for the development of batteries that are capable of sub-zero temperature operation.To get the most energy storage out of the battery at low temperatures,improvements in electrolyte chemistry need to be coupled with optimized electrode materials and tailored electrolyte/electrode interphases.Herein,this review critically outlines electrolytes’limiting factors,including reduced ionic conductivity,large de-solvation energy,sluggish charge transfer,and slow Li-ion transportation across the electrolyte/electrode interphases,which affect the low-temperature performance of Li-metal batteries.Detailed theoretical derivations that explain the explicit influence of temperature on battery performance are presented to deepen understanding.Emerging improvement strategies from the aspects of electrolyte design and electrolyte/electrode interphase engineering are summarized and rigorously compared.Perspectives on future research are proposed to guide the ongoing exploration for better low-temperature Li-metal batteries.

Dual Additives for Stabilizing Li Deposition and SEI Formation in Anode-Free Li-Metal Batteries

Anode-free Li-metal batteries are of significant interest to energy storage industries due to their intrinsically high energy.However,the accumulative Li dendrites and dead Li continuously consume active Li during cycling.That results in a short lifetime and low Coulombic efficiency of anode-free Li-metal batteries.Introducing effective electrolyte additives can improve the Li deposition homogeneity and solid electrolyte interphase(SEI)stability for anode-free Li-metal batteries.Herein,we reveal that introducing dual additives,composed of LiAsF6 and fluoroethylene carbonate,into a low-cost commercial carbonate electrolyte will boost the cycle life and average Coulombic efficiency of NMC‖Cu anode-free Li-metal batteries.The NMC‖Cu anode-free Li-metal batteries with the dual additives exhibit a capacity retention of about 75%after 50 cycles,much higher than those with bare electrolytes(35%).The average Coulombic efficiency of the NMC‖Cu anode-free Li-metal batteries with additives can maintain 98.3%over 100 cycles.In contrast,the average Coulombic efficiency without additives rapidly decline to 97%after only 50 cycles.In situ Raman measurements reveal that the prepared dual additives facilitate denser and smoother Li morphology during Li deposition.The dual additives significantly suppress the Li dendrite growth,enabling stable SEI formation on anode and cathode surfaces.Our results provide a broad view of developing low-cost and high-effective functional electrolytes for high-energy and long-life anode-free Li-metal batteries.

From Liquid to Solid‑State Lithium Metal Batteries:Fundamental Issues and Recent Developments

The widespread adoption of lithium-ion batteries has been driven by the proliferation of portable electronic devices and electric vehicles,which have increasingly stringent energy density requirements.Lithium metal batteries(LMBs),with their ultralow reduction potential and high theoretical capacity,are widely regarded as the most promising technical pathway for achieving high energy density batteries.In this review,we provide a comprehensive overview of fundamental issues related to high reactivity and migrated interfaces in LMBs.Furthermore,we propose improved strategies involving interface engineering,3D current collector design,electrolyte optimization,separator modification,application of alloyed anodes,and external field regulation to address these challenges.The utilization of solid-state electrolytes can significantly enhance the safety of LMBs and represents the only viable approach for advancing them.This review also encompasses the variation in fundamental issues and design strategies for the transition from liquid to solid electrolytes.Particularly noteworthy is that the introduction of SSEs will exacerbate differences in electrochemical and mechanical properties at the interface,leading to increased interface inhomogeneity—a critical factor contributing to failure in all-solidstate lithium metal batteries.Based on recent research works,this perspective highlights the current status of research on developing high-performance LMBs.

Boosting the cycling stability of all-solid-state lithium metal batteries through MOF-based polymeric protective layers

Solid-state electrolytes(SSEs)play a pivotal role in advancing next-generation lithium metal battery technology.However,they commonly encounter substantial interfacial resistance and poor stability when interfacing with lithium metal,hindering practical applications.Herein,we introduce a flexible metal-organic framework(MOF:NUS-6)-incorporated polymeric layer,denoted as NP,designed to protect the sodium superionic conductor(NASICON)-type Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP)electrolyte from Li metal anodes.The NP matrix establishes a soft interface with the LATP surface,effectively reducing voids and gaps that may arise between the LATP electrolyte and Li metal.Moreover,the MOF component in NP enhances ionic conductivity,offers abundant Li^(+)transport sites,and provides hierarchical ion channels,ensuring a homogeneous Li^(+)flow and thus effectively inhibiting Li dendrite formation.Utilizing NP,we fabricate Li symmetrical cells cycled for over 1600 h at 0.2 mA cm^(-2)and all-solid-state LiINP-LATPI LiFePO_(4)batteries,achieving a remarkable 99.3%capacity retention after 200 cycles at 0.2 C.This work outlines a general strategy for designing long-lasting and stable solid-state Li metal batteries.

SEI/dead Li-turning capacity loss for high-performance anode-free solid-state lithium batteries

Anode-free solid-state lithium metal batteries(AF-SSLBs)have the potential to deliver higher energy density and improved safety beyond lithium-metal batteries.However,the unclear mechanism for the fast capacity decay in AF-SSLBs,either determined by dead Li or solid electrolyte interface(SEI),limits the proposal of effective strategies to prolong cycling life.To clarify the underlying mechanism,herein,the evolution of SEI and dead Li is quantitatively analyzed by a solid-state nuclear magnetic resonance(ss-NMR)technology in a typical LiPF6-based polymer electrolyte.The results show that the initial capacity loss is attributed to the formation of SEI,while the dead Li dominates the following capacity loss and the growth rate is 0.141 mA h cm^(−2)cycle−1.To reduce the active Li loss,the combination of inorganic-rich SEI and self-healing electrostatic shield effect is proposed to improve the reversibility of Li deposition/dissolution behavior,which reduces the capacity loss rate for the initial SEI and following dead Li generation by 2.3 and 20.1 folds,respectively.As a result,the initial Coulombic efficiency(ICE)and stable CE increase by 15.1%and 15.3%in Li-Cu cells,which guides the rational design of high-performance AF-SSLBs.

Branch-Chain-Rich Diisopropyl Ether with Steric Hindrance Facilitates Stable Cycling of Lithium Batteries at-20℃

Li metal batteries(LMBs)offer signifi-cant potential as high energy density alternatives;nev-ertheless,their performance is hindered by the slow desolvation process of electrolytes,particularly at low temperatures(LT),leading to low coulombic efficiency and limited cycle stability.Thus,it is essential to opti-mize the solvation structure thereby achieving a rapid desolvation process in LMBs at LT.Herein,we introduce branch chain-rich diisopropyl ether(DIPE)into a 2.5 M Li bis(fluorosulfonyl)imide dipropyl ether(DPE)elec-trolyte as a co-solvent for high-performance LMBs at-20℃.The incorporation of DIPE not only enhances the disorder within the electrolyte,but also induces a steric hindrance effect form DIPE’s branch chain,excluding other solvent molecules from Li+solvation sheath.Both of these factors contribute to the weak interactions between Li^(+)and solvent molecules,effectively reducing the desolvation energy of the electrolyte.Consequently,Li(50μm)||LFP(mass loading~10 mg cm^(-2))cells in DPE/DIPE based electrolyte demonstrate stable performance over 650 cycles at-20℃,delivering 87.2 mAh g^(-1),and over 255 cycles at 25℃ with 124.8 mAh g^(-1).DIPE broadens the electrolyte design from molecular structure considera-tions,offering a promising avenue for highly stable LMBs at LT.

Atomistic understanding of capacity loss in LiNiO_(2)for high-nickel Li-ion batteries:First-principles study

Combining the first-principles calculations and structural enumeration with recognition,the delithiation process of LiNiO_(2)is investigated,where various supercell shapes are considered in order to obtain the formation energy of Li_(x)NiO_(2).Meanwhile,the voltage profile is simulated and the ordered phases of lithium vacancies corresponding to concentrations of 1/4,2/5,3/7,1/2,2/3,3/4,5/6,and 6/7 are predicted.To understand the capacity decay in the experiment during the charge/discharge cycles,deoxygenation and Li/Ni antisite defects are calculated,revealing that the chains of oxygen vacancies will be energetically preferrable.It can be inferred that in the absence of oxygen atom in high delithiate state,the diffusion of Ni atoms is facilitated and the formation of Li/Ni antisite is induced.

Ion-dipole regulation based on bidentate solvent for stabilizing high-voltage lithium metal batteries

The poor compatibility of ester electrolytes with lithium metal anode severely limits its use in high voltage lithium metal batteries(LMBs).In this work,a bidentate solvent 1,2-diethoxyethane(DEE) is introduced into ester electrolyte to regulate the ion-dipole interactions to enhance the solubility of LiNO_(3),which enables compatibility with Li anode and maintains the high voltage cathode stability.In the designed electrolyte,the steric effect of DEE facilitates the participation of NO_(3)^(-)and PF_6^(-)anions in the Li^(+) solvation structure,thus promoting the generation of inorganic-rich solid electrolyte interphase(SEI).And the low viscosity of DEE also ensures that the ester electrolyte poses good interracial wettability.As a result,our designed electrolyte enables the high-loading Li‖NCM622 and Li‖NCM811(^(3) mA h cm^(-2)) full cells to achieve stable cycling over 200 cycles,8 times longer than that of a conventional ester electrolyte.This work suggests that regulation of intermolecular interactions in conventional ester electrolytes is a scalable and effective approach to achieve excellent electrochemical performance of LMBs.

Biphase-to-monophase structure evolution of Na_(0.766+x)Li_(x)Ni_(0.33-x)Mn_(0.5)Fe_(0.1)Ti_(0.07)O_(2) toward ultradurable Na-ion batteries

Layered composite oxide materials with O3/P2 biphasic crystallographic structure typically demonstrate a combination of high capacities of the O3 phase and high operation voltages of the P2 phase.However,their practical applications are seriously obstructed by difficulties in thermodynamic phase regulation,complicated electrochemical phase transition,and unsatisfactory cycling life.Herein,we propose an efficient structural evolution strategy from biphase to monophase of Na_(0.766+x)Li_(x)Ni_(0.33-x)Mn_(0.5)Fe_(0.1)Ti_(0.07)O_(2) through Li+substitution.The role of Li+substitution not only simplifies the unfavorable phase transition by altering the local coordination of transition metal(TM)cations but also stabilizes the cathode–electrolyte interphase to prevent the degradation of TM cations during battery cycling.As a result,the thermodynamically robust O_(3)-Na_(0.826)Li_(0.06)Ni_(0.27)Mn_(0.5)Fe_(0.1)Ti_(0.07)O_(2) cathode delivers a high capacity of 139.4 mAh g^(-1) at 0.1 C and shows prolonged cycling life at high rates,with capacity retention of 81.6%at 5 C over 500 cycles.This work establishes a solid relationship between the thermodynamic structure evolution and electrochemistry of layered cathode materials,contributing to the development of long-life sodium-ion batteries.

NbN quantum dots anchored hollow carbon nanorods as efficient polysulfide immobilizer and lithium stabilizer for Li-S full batteries

The shuttle effect of lithium polysulfides(LiPSs)and uncontrollable lithium dendrite growth seriously hinder the practical application of lithium-sulfur(Li-S)batteries.To simultaneously address such issues,monodispersed Nb N quantum dots anchored on nitrogen-doped hollow carbon nanorods(NbN@NHCR)are elaborately developed as efficient Li PSs immobilizer and Li stabilizer for high-performance Li-S full batteries.Density functional theory(DFT)calculations and experimental characterizations demonstrate that the sulfiphilic and lithiophilic NbN@NHCR hybrid can not only efficiently immobilize the soluble Li PSs and facilitate diffusion-conversion kinetics for alleviating the shuttling effect,but also homogenize the distribution of Li+ions and regulate uniform Li deposition for suppressing Li-dendrite growth.As a result,the assembled Li-S full batteries(NbN@NHCR-S||Nb N@NHCR-Li)deliver excellent long-term cycling stability with a low decay rate of 0.031%per cycle over 1000 cycles at high rate of 2 C.Even at a high S loading of 5.8 mg cm^(-2)and a low electrolyte/sulfur ratio of 5.2μL mg^(-1),a large areal capacity of 6.2 mA h cm^(-2)can be achieved in Li-S pouch cell at 0.1 C.This study provides a new perspective via designing a dual-functional sulfiphilic and lithiophilic hybrid to address serious issues of the shuttle effect of S cathode and dendrite growth of Li anode.

Porous Organic Cage‑Based Quasi‑Solid‑State Electrolyte with Cavity‑Induced Anion‑Trapping Effect for Long‑Life Lithium Metal Batteries

Porous organic cages(POCs)with permanent porosity and excellent host–guest property hold great potentials in regulating ion transport behavior,yet their feasibility as solid-state electrolytes has never been testified in a practical battery.Herein,we design and fabricate a quasi-solid-state electrolyte(QSSE)based on a POC to enable the stable operation of Li-metal batteries(LMBs).Benefiting from the ordered channels and cavity-induced anion-trapping effect of POC,the resulting POC-based QSSE exhibits a high Li+transference number of 0.67 and a high ionic conductivity of 1.25×10^(−4) S cm^(−1) with a low activation energy of 0.17 eV.These allow for homogeneous Li deposition and highly reversible Li plating/stripping for over 2000 h.As a proof of concept,the LMB assembled with POC-based QSSE demonstrates extremely stable cycling performance with 85%capacity retention after 1000 cycles.Therefore,our work demonstrates the practical applicability of POC as SSEs for LMBs and could be extended to other energy-storage systems,such as Na and K batteries.