锂金属负极的可逆性与沉积形貌的关联

高能量密度二次电池的商业化将会推动便携式电子设备和电动车的飞速发展。锂金属电池因具有较高的理论能量密度而受到研究者的广泛关注。然而,锂金属负极较低的库仑效率(CE)和枝晶生长等问题,严重制约了锂金属电池的发展。库仑效率是衡量电池体系可逆性的关键参数之一,锂金属负极的库仑效率在不同电解液中存在较大的差异,本文以四种常见的电解液为例,包括1 mol·L^(-1)六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯电解液,1 mol·L^(-1)六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯+5%(w)氟代碳酸乙烯酯电解液,1 mol·L^(-1)双(三氟甲烷磺酰)亚胺锂-乙二醇二甲醚/1,3二氧戊环+2%(w)硝酸锂电解液,以及4 mol·L^(-1)双氟磺酰亚胺锂-乙二醇二甲醚电解液,利用原子力显微镜研究了不同电解液体系中锂金属的生长行为,探讨了锂金属沉积形貌与其库仑效率之间的联系,为发展高效的锂金属负极提供了参考依据。

Carbon materials for stable Li metal anodes: Challenges, solutions, and outlook

Lithium(Li)metal is regarded as the ultimate anode for next-generation Li-ion batteries due to its highest specific capacity and lowest electrochemical potential.However,the Li metal anode has limitations,including virtually infinite volume change,nonuniform Li deposition,and an unstable electrode-electrolyte interface,which lead to rapid capacity degradation and poor cycling stability,significantly hindering its practical application.To address these issues,intensive efforts have been devoted toward accommodating and guiding Li deposition as well as stabilizing the interface using various carbon materials,which have demonstrated excellent effectiveness,benefiting from their vast variety and excellent tunability of the structure-property relationship.This review is intended as a guide through the fundamental challenges of Li metal anodes to the corresponding solutions utilizing carbon materials.The specific functionalities and mechanisms of carbon materials for stabilizing Li metal anodes in these solutions are discussed in detail.Apart from the stabilization of the Li metal anode in liquid electrolytes,attention has also been paid to the review of anode-free Li metal batteries and solid-state batteries enabled by strategies based on carbon materials.Furthermore,we have reviewed the unresolved challenges and presented our outlook on the implementation of carbon materials for stabilizing Li metal anodes in practical applications.

Deciphering pitting behavior of lithium metal anodes in lithium sulfur batteries

Unambiguous understanding in lithium anode failure mechanism calls for a comprehensive methodology to investigate the coupled morphological,electrochemical and mechanical behaviors during the stripping process.In this work,a mechanistic investigation of the pitting behavior of lithium metal in an electrolyte containing lithium polysulfides in lithium sulfur batteries was developed.It is found that lithium polysulfides could aggravate the nonuniform stripping of lithium electrodes.

氟代溶剂在锂金属电池中的应用

近年来,锂金属电池由于具有较高的能量密度而成为储能领域的研究热点。电解液作为锂金属电池的“血液”发挥着至关重要的作用。在传统锂离子电池电解液中,锂金属负极与电解液之间的界面副反应严重并伴随着锂枝晶生长,从而导致安全隐患以及循环寿命缩短等问题。在解决锂金属负极问题上,电解液调控策略具有易操作性和有效性,因而在推动锂金属电池发展方面具有举足轻重的地位。氟代电解液是目前重要的研究方向,氟代电解液在循环过程中能够在电极表面形成富含LiF的固体电解质界面膜(SEI);该界面膜不仅可以有效抑制负极锂枝晶的形成,并且在正极方面能够大幅提高电解液的氧化稳定性,从而提升高电压正极的适配性和锂金属电池的循环稳定性。氟代电解液中氟代溶剂/氟代锂盐的分子结构对电解液的溶剂化结构有重要影响。当氟代溶剂分子中氟原子的位置与数量不同时,氟代溶剂的物理化学性质也会随之发生变化,进而改变了电解液与电极的界面反应性。因此,氟代溶剂能够起到调制SEI膜成分和结构的作用,是决定电池性能的关键因素。本文总结了应用于锂金属电池的主要氟代溶剂,尤其是近几年来发展的新型氟代溶剂;着重介绍了高度氟代的溶剂分子作为局域超浓电解液的稀释剂,以及对溶剂进行精准分子设计得到的部分氟代溶剂等。此外,本文还分析探讨了氟代溶剂分子与电池性能之间的构效关系,展望了构建新型氟代溶剂分子的策略,希望能对电解液溶剂分子的结构设计以及构效关系的评估有一定的启发意义。

Tuning electrochemical transformation process of zeolitic imidazolate framework for efficient water oxidation activity

Metal-organic frameworks(MOFs)have been widely studied as efficient electrocatalysts for water oxidation due to their tunable structure and easy preparation.However,the rational design of MOFs-based electrocatalysts and fundamental understanding of their structural evolution during oxygen evolution reaction(OER)remain critical challenges.Here,we report a facile approach to tune the structural transformation process of the Co-based zeolitic imidazolate framework(ZIF)during the OER process by using water molecules as a vacancy promoter.The modified ZIF catalyst accelerates the structural transformation from MOF precursor to electrochemical active species and simultaneously enhances the vacancy density during the electrochemical activation process.The optimized electrocatalyst exhibits an extremely low overpotential 175 mV to deliver 10 mA cm^(-2) and superior durability(100 h)at 100 mA cm^(-2).The comprehensive characterization results reveal the structural transformation from the initial tetrahedral Co sites to cobalt oxyhydroxide(CoOOH)and the formation process of oxygen vacancies(CoOOH-Vo)at a high anodic potential.These findings represent a promising way to achieve highly active MOF-based electrocatalysts for water oxidation.

Conductive metal-organic frameworks promoting polysulfides transformation in lithium-sulfur batteries

Metal organic frameworks(MOFs) have been extensively investigated in Li-S batteries owing to high surface area, adjustable structures and abundant catalytic sites. Nevertheless, the insulating nature of traditional MOFs render retarded kinetics of polysulfides conversion, leading to insufficient utilization of sulfur. In comparison, conductive MOFs(c-MOFs) show great potential for promoting polysulfides transformation due to superb electronic conductivity. In this work, a nickel-catecholates based c-MOF, NiHHTP(HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), is designed to regulate surface chemistry of self-supported carbon paper for advanced Li-S batteries. Taking advantage of the porous structure and high conductivity, the as-prepared Ni-HHTP is conducive to synergising strengthening the chemisorption of polysulfides and accelerating the reaction kinetics in Li-S batteries, significantly mitigating the polysulfides diffusion from the non-encapsulated sulfur cathode, therefore promoting polysulfides transformation in Li-S batteries. This work points out a promising modification strategy for developing advanced sulfur cathode in Li-S batteries.

Regulating Pd‐catalysis for electrocatalytic CO_(2) reduction to formate via intermetallic PdBi nanosheets

Electrocatalytic CO_(2) reduction plays an important role in the reduction of the CO_(2) concentration in atmosphere and consequently the mitigation of greenhouse effects.Pd has been extensively inves‐tigated as an electrocatalyst for the CO_(2) reduction to formate,which is an important raw material in the production of organic chemicals.However,the low selectivity and competitive reaction(hydro‐gen evolution reaction(HER))have hindered the performance of monometallic Pd catalysts.In this paper,intermetallic PdBi nanosheets(NSs)are prepared for efficient CO_(2) reduction to formate.The highest Faradaic efficiency(FE)of formate on fully ordered PdBi NSs reaches 91.9%at−1.0 V vs.RHE,which outperforms that of the disordered PdBi and pure Pd catalysts.Density functional theo‐ry calculations suggest that compared to disordered PdBi NSs,the ordered structure can decrease the free energy barrier of*OCHO(a key intermediate of formate formation)and inhibit H_(2) evolution as well,thereby enhancing the activity and selectivity for formate production.

锂金属负极固体电解质界面膜的理解与改性策略

锂金属负极因具有较高的比容量和较低的电极电势,被认为是最有发展前景的电池负极材料之一.然而,不稳定的锂金属负极固体电解质界面膜和严重的锂枝晶生长问题限制了锂金属负极的实际应用.认识和理解锂金属负极固体电解质界面膜的组成与结构,并将其与锂金属生长行为建立有效的关联,是解决锂金属负极不稳定问题的关键.本文综述了近年来有关锂金属负极固体电解质界面膜的表征技术和调控策略,并介绍了锂金属软包电池的界面研究现状.本文对锂金属负极的实际应用具有一定的指导意义.

Artificial intelligence for the understanding of electrolyte chemistry and electrode interface in lithium battery

Recognizing the critical role of electrolyte chemistry and electrode interfaces in the performance and safety of lithium batteries,along with the urgent need for more sophisticated methods of analysis,this comprehensive review underscores the promise of machine learning(ML)models in this research field.It explores the application of these innovative methods to studying battery interfaces,particularly focusing on lithium metal anodes.Amid the limitations of traditional experimental techniques,the review supports a hybrid approach that couples experimental and simulation methods,enabling granular insights into the formation process and characteristics of battery interfaces at the molecular level and harnessing AI to extract patterns from voluminous data sets.It showcases the utility of such techniques in electrolyte design and battery life prediction and introduces a novel perspective on battery interface mechanisms.The review concludes by asserting the potential of artificial intelligence(AI)or ML models as invaluable tools in the future of battery research and highlights the importance of fostering confidence in these technologies within the scientific community.

各向同性模量的分级多孔隔膜促进锌离子均匀扩散及水系锌离子电池循环稳定性

水系锌离子电池具有低成本、高安全的特点,有望应用于大规模储能.然而,锌负极的循环稳定性仍不理想,且水系电池缺少合适的亲水隔膜,这限制了水系锌离子电池的实际应用.在本文中,我们报道了一种可用于水系电池的分级多孔的聚偏二氟乙烯-双三氟甲磺酰亚胺锂(PVDF-LiTFSI)(PVDF-Li)隔膜.均匀混合的LiTFSI盐降低了PVDF的结晶性,使隔膜具有优异的机械强度,并形成分级的孔隙结构.这种LiTFSI诱导的分级多孔结构有助于实现Zn2+的快速传输和锌的均匀沉积,同时保证隔膜在水系电解液中具有优异的润湿性.这种先进的PVDF-Li隔膜能显著抑制锌枝晶的生长,提高水系锌离子电池的循环寿命.因此,使用PVDF-Li隔膜的Zn||V2O5电池的初始容量达324 mA h g-1,比传统玻璃纤维隔膜高27%,且容量保持率也得到大幅提升.该研究设计了一种功能隔膜来调控正负极反应的均匀性,这为高性能水系电池的开发提供了新的思路.

Stable cycling of practical high-voltage LiCoO_(2)pouch cell via electrolyte modification

Nitriles as efficient electrolyte additives are widely used in high-voltage lithium-ion batteries.However,their working mechanisms are still mysterious,especially in practical high-voltage LiCoO_(2)pouch lithium-ion batteries.Herein,we adopt a tridentate ligandcontaining 1,3,6-hexanetricarbonitrile(HTCN)as an effective electrolyte additive to shed light on the mechanism of stabilizing high-voltage LiCoO_(2)cathode(4.5 V)through nitriles.The LiCoO_(2)/graphite pouch cells with the HTCN additive electrolyte possess superior cycling performance,90%retention of the initial capacity after 800 cycles at 25℃,and 72%retention after 500 cycles at 45℃,which is feasible for practical application.Such an excellent cycling performance can be attributed to the stable interface:The HTCN molecules with strong electron-donating ability participate in the construction of cathode-electrolyte interphase(CEI)through coordinating with Co ions,which suppresses the decomposition of electrolyte and improves the structural stability of LiCoO_(2)during cycling.In summary,the work recognizes a coordinating-based interphase-forming mechanism as an effective strategy to optimize the performance of high voltage LiCoO_(2)cathode with appropriate electrolyte additives for practical pouch batteries.

Crossover effects of transition metal ions in high-voltage lithium metal batteries

Enhancing the cut-off voltage of high-nickel layered oxide cathodes is an efficient way to obtain higher energy density of lithiummetal batteries(LMBs).However,the phase transition of the cathode materials and the uncontrolled decomposition of the electrolytes at high voltage can lead to irreversible dissolution of transition metal ions,which might cause the crossover effects on the lithium metal anodes.Nonetheless,the mechanism and electrolyte dependence of the crossover effects for Li metal anodes are still unclear.Herein,we investigate the crossover effects between LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)and Li-metal anode in two electrolyte systems.For ether-based electrolyte,its poor oxidation stability results in massive dissolution of transition metal ions,leading to dendrite growth on anode and rapid cells failure.Conversely,ester-based electrolyte exhibits good electrochemical performances at 4.5 V with little crossover effect.This study provides an idea for electrolyte systems selection for high-voltage LMBs,and verifies that the crossover effect should not be neglected in LMBs.

Pomegranate-like C_(60)@cobalt/nitrogen-codoped porous carbon for high-performance oxygen reduction reaction and lithium-sulfur battery

Porous carbon materials play essential roles in electrocatalysis and electrochemical energy storage.It is of significant importance to rationally design and tune their porous structure and active sites for achieving high electrochemical activity and stability.Herein,we develop a novel approach to tune the morphology of porous carbon materials(PCM)by embedding fullerene C_(60),achieving improved performance of oxygen reduction reaction(ORR)and lithium-sulfur(Li-S)battery.Owing to the strong interaction between C_(60)and imidazole moieties,pomegranate-like hybrid of Ow-embedded zeolitic imidazolate framework(ZIF-67)precursor is synthesized,which is further pyrolyzed to form C_(60)-embedded cobalt/nitrogen-codoped porous carbon materials(abbreviated as C_(60)@Co-N-PCM).Remarkably,the unique structure of C_(60)@Co-N-PCM offers excellent ORR electrocatalytic activity and stability in alkaline solutions,outperforming the commercial Pt/C(20 wt.%)catalyst.Besides,C_(60)@Co-N-PCM as a novel cathode delivers a high specific capacity of-900 mAh·g^(-1) at 0.2 C rate in Li-S batteries,which is superior to the pristine ZIF-67-derived PCM without embedding C_(60).

Molybdenum-doped ordered L1_(0)-PdZn nanosheets for enhanced oxygen reduction electrocatalysis

Ultrathin Pd-based two-dimensional(2D)nanosheets(NSs)with tunable physicochemical properties have emerged as promising candidate for oxygen reduction reaction(ORR).Unfortunately,structurally ordered Pd-based NSs can be hardly prepared as high temperature annealing(>600℃)is necessary for disorder to order phase transition,making it a considerable challenge for morphology control.Herein,a new class of ultrathin structurally ordered Mo-doped L1_(0)-PdZn NSs with curved geometry and abundant defects/lattice distortions is reported as an efficient oxygen reduction electrocatalyst in alkaline solution.It is found that Mo(CO)_(6) serves as reducing agent and Mo source to generate the unique ordered 2D morphology,which leads to the significantly modified electronic structure.The developed L1_(0)-Mo-PdZn NSs exhibit excellent ORR mass activity of 2.6 A mg_(Pd)^(−1) at 0.9 V versus reversible hydrogen electrode,31.5 and 17.6 times higher than those of Pd/C and Pt/C,respectively,outperforming most of the reported Pdbased ORR electrocatalsyts.Impressively,L1_(0)-Mo-PdZn NSs is extremely stable for ORR,with only 2.3% activity loss after 10000 potential cycles.Density functional theory study suggests that ordered L1_(0) structure and Mo doping can raise the vacancy formation energy of Pd atom and thus promote the ORR stability.

Regulating surface chemistry of separator with LiF for advanced Li-S batteries

Lithium-sulfur(Li-S)batteries have attracted intensive attention owing to their ultrahigh theoretical energy density.Nevertheless,the practical application of Li-S batteries is prevented by uncontrollable shuttle effect and retarded reaction kinetics.To address the above issues,lithium fluoride(LiF)was employed to regulate the surface chemistry of routine separator.The functional separator demonstrates a great ability to suppress active S loss and protect lithium anode.This work provides a facile strategy for the development of advanced Li-S batteries.