Tackling application limitations of high-safetyγ-butyrolactone electrolytes:Exploring mechanisms and proposing solutions

Developing wide-temperature and high-safety lithium-ion batteries(LIBs)presents significant challenges attributed to the absence of suitable solvents possessing broad liquid range and non-flammability properties.γ-Butyrolactone(GBL)has emerged as a promising solvent;however,its incompatibility with graphite anode has hindered its application.This limitation necessitates a comprehensive investigation into the underlying mechanisms and potential solutions.In this study,we achieve a molecular-level understanding of the perplexing interphase formation process by employing in-situ spectroelectrochemical techniques and density function calculations.Our findings reveal that,even at high salt concentrations,GBL consistently occupies the primary Li^(+)solvation sheath,leading to extensive GBL decomposition and the formation of a high-impedance and inorganic-poor solid-electrolyte interphase(SEI)layer.Contrary to manipulating solvation structures,our research demonstrates that the utilization of filmforming additives with higher reduction potential facilitates the pre-establishment of a robust SEI film on the graphite anode.This approach effectively inhibits GBL decomposition and significantly enhances the battery's lifespan.This study provides the first reported intrinsic understanding of the unique GBLgraphite incompatibility and offers valuable insights for the development of wide-temperature and high-safety LIBs.

单离子聚合物快离子导体

具有高锂离子迁移数和良好可加工性能的锂快离子导体对于全固态电池的发展非常重要。然而,现有的锂快离子导体主要限制于硬质陶瓷,目前尚无柔性聚合物类型的锂快离子导体被报道。在这个工作中,我们报告了一种通过三种不同有机单体的自由基聚合反应形成的三元无规共聚单离子快离子导体(SISC)。该SISC中包含丰富的锂离子传输位点和具有阴离子锚定功能的阴离子受体。此外,三种不同单体的共聚反应带来低结晶度和低玻璃化转变温度(T_(g)),有利于链段运动,从而获得小的锂离子传输的活化能(E_(a))。电化学测试结果表明,该SISC的室温离子电导率和锂离子迁移数分别达到1.29·mS·cm^(-1)和0.94。将SISC与锂金属负极和多种正极(包括LiFePO_(4)、LiCoO_(2)和硫化聚丙烯腈(SPAN))原位聚合,组装得到的全固态电池具有良好的电化学稳定性。其中,Li||LiFePO_(4)全固态电池表现出高达8C的倍率性能和良好的循环寿命(在0.5C倍率下稳定循环>700圈)。这项工作提供了一种新颖的聚合物基快离子导体设计理念,对于发展高性能全固态电池具有重要意义。

Achieving high-capacity and long-life K^(+)storage enabled by constructing yolk-shell Sb_(2)S_(3)@N,S-doped carbon nanorod anodes

As promising anode candidates for potassium-ion batteries(PIBs),antimony sulfide(Sb_(2)S_(3))possesses high specific capacity but suffers from massive volume expansion and sluggish kinetics due to the large K^(+)insertion,resulting in inferior cycling and rate performance.To address these challenges,a yolk-shell structured Sb_(2)S_(3)confined in N,S co-doped hollow carbon nanorod(YS-Sb_(2)S_(3)@NSC)working as a viable anode for PIBs is proposed.As directly verified by in situ transmission electron microscopy(TEM),the buffer space between the Sb_(2)S_(3)core and thin carbon shell can effectively accommodate the large expansion stress of Sb_(2)S_(3)without cracking the shell and the carbon shell can accelerate electron transport and K^(+)diffusion,which plays a significant role in reinforcing the structural stability and facilitating charge transfer.As a result,the YS-Sb_(2)S_(3)@NSC electrode delivers a high reversible K^(+)storage capacity of 594.58 m A h g^(-1)at 0.1 A g^(-1)and a long cycle life with a slight capacity degradation(0.01%per cycle)for 2000 cycles at 1 A g^(-1)while maintaining outstanding rate capability.Importantly,utilizing in in situ/ex situ microscopic and spectroscopic characterizations,the origins of performance enhancement and K^(+)storage mechanism of Sb_(2)S_(3)were clearly elucidated.This work provides valuable insights into the rational design of high-performance and durable transition metal sulfides-based anodes for PIBs.

Synergistic interphase modification with dual electrolyte additives to boost cycle stability of high nickel cathode for all-climate battery

B-containing electrolyte additives are widely used to enhance the cycle performance at low temperature and the rate capability of lithium-ion batteries by constructing an efficient cathode electrolyte interphase(CEI)to facilitate the rapid Li+migration.Nevertheless,its wide-temperature application has been limited by the instability of B-derived CEI layer at high temperature.Herein,dual electrolyte additives,consisting of lithium tetraborate(Li_(2)TB)and 2,4-difluorobiphenyl(FBP),are proposed to boost the widetemperature performances of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM)cathode.Theoretical calculation and electrochemical performances analyses indicate that Li_(2)TB and FBP undergo successive decomposition to form a unique dual-layer CEI.FBP acts as a synergistic filming additive to Li_(2)TB,enhancing the hightemperature performance of NCM cathode while preserving the excellent low-temperature cycle stability and the superior rate capability conferred by Li_(2)TB additive.Therefore,the capacity retention of NCM‖Li cells using optimal FBP-Li_(2)TB dual electrolyte additives increases to 100%after 200 cycles at-10℃,99%after 200 cycles at 25℃,and 83%after 100 cycles at 55℃,respectively,much superior to that of base electrolyte(63%/69%/45%).More surprisingly,galvanostatic c ha rge/discharge experiments at different temperatures reveal that NCM‖Li cells using FBP-Li_(2)TB additives can operate at temperatures ranging from-40℃to 60℃.This synergistic interphase modification utilizing dual electrolyte additives to construct a unique dual-layer CEI adaptive to a wide temperature range,provides valuable insights to the practical applications of NCM cathodes for all-climate batteries.

原位聚合表面修饰的金属锂负极

金属锂负极由于比容量高(3860 mAh·g^(-1))及氧化还原电位极低(-3.04 V vs.标准氢气电极(SHE)),被认为是实现高能量密度锂电池的理想负极。然而,金属锂电极与电解液反应剧烈,且锂离子在电极表面沉积不均匀容易产生枝晶,导致其循环稳定性和安全性都较差,限制了其应用推广。我们前期通过构建金属锂-碳纳米管(Li-CNT)复合结构,极大的提高了金属锂的比表面积,降低了电极电流密度,从而有效地抑制了锂枝晶的生长,提高了金属锂电极的循环稳定性和安全性能。本工作在前期工作基础上,采用简单的液相反应,利用4-氟苯乙烯(FPS)对Li-CNT进行表面修饰并进行原位聚合,得到了表面富含氟化锂(Li F)保护层的Li-CNT(FPS-Li-CNT)。该表面修饰层能够有效抑制电解液和空气对Li-CNT的侵蚀,显著的提高了LiCNT电极的界面稳定性。FPS-Li-CNT与磷酸铁锂正极(LFP)组成的LFP||FPS-Li-CNT全电池,在正负极容量配比为1:6条件下,能够稳定循环280圈,库伦效率达到97.7%。

原位修饰策略实现高倍率室温固态锂电池

固态锂电池由于其安全特性与良好的电化学性能而备受关注。但电极内锂离子传导通道不顺畅及电极-电解质界面接触阻抗大以及界面发生副反应等问题仍然阻碍着固态电池的实际应用。本工作在电极内部及电极与Li_(1.5)Al_(0.5)Ge_(1.5)(PO_(4))_(3)(LAGP)电解质之间原位聚合碳酸亚乙烯酯固态聚合物电解质(PVC-SPE),构建了正极内部的离子传导网络,改善了电解质-电极界面的接触,而且还有效阻止了锂负极与LAGP电解质之间的副反应。Li|LAGP|LiFePO_(4)固态电池具有良好的循环性能和倍率充放电性能,0.2C循环200次仍有98%的容量保持率,3C倍率放电容量是0.2C容量的72.4%。这种原位聚合制备高性能固态电池有希望成为解决界面问题与构建电极内离子传导网络的方法。

Directional construction of Cu2S branch arrays for advanced oxygen evolution reaction

Metal sulphide electrocatalyst is considered as one of the most promising low-cost candidates for oxygen evolution reaction(OER).In this work,we report a novel free-standing Cu2S branch array via a facile TiO2-induced electrodeposition-sulfurization method.Interestingly,cross-linked Cu2S nanoflake branch is strongly anchored on the TiO2 backbone forming high-quality Cu2S/TiO2/Cu2S core-branch arrays.The branch formation mechanism is also proposed.As compared to the pure Cu2S nanowire arrays,the asprepared Cu2S/TiO2/Cu2S core-branch arrays show much better alkaline OER performance with lower overpotential(284 mV at 10 mA cm^-2)and smaller Tafel slope(72 dec-1)as well as enhanced longterm durability mainly due to larger exposed area and more active electrocatalytic sites.Our work provides a new way for construction of advanced metal sulphide electrocatalysts for electrochemical energy conversion.

Stable Lithium-Carbon Composite Enabled by Dual-Salt Additives

Lithium metal is regarded as the ultimate negative electrode material for secondary batteries due to its high energy density.However,it suffers from poor cycling stability because of its high reactivity with liquid electrolytes.Therefore,continuous efforts have been put into improving the cycling Coulombic efficiency(CE)to extend the lifespan of the lithium metal negative electrode.Herein,we report that using dual-salt additives of LiPF_(6) and LiNO_(3) in an ether solvent-based electrolyte can significantly improve the cycling stability and rate capability of a Li-carbon(Li-CNT)composite.As a result,an average cycling CE as high as 99.30% was obtained for the Li-CNT at a current density of 2.5 mA cm^(-2) and an negative electrode to positive electrode capacity(N/P)ratio of 2.The cycling stability and rate capability enhancement of the Li-CNT negative electrode could be attributed to the formation of a better solid electrolyte interphase layer that contains both inorganic components and organic polyether.The former component mainly originates from the decomposition of the LiNO_(3) additive,while the latter comes from the LiPF_(6)-induced ring-opening polymerization of the ether solvent.This novel surface chemistry significantly improves the CE of Li negative electrode,revealing its importance for the practical application of lithium metal batteries.

Revisiting the capacity-fading mechanism of P2-type sodium layered oxide cathode materials during high-voltage cycling

P2-type sodium layered oxide cathode (Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)P2-NNMO) has attracted great attention as a promising cathode material for sodium ion batteries because of its high specific capacity. However, this material suffers from a rapid capacity fade during high-voltage cycling. Several mechanisms have been proposed to explain the capacity fade, including intragranular fracture caused by the P2-O2 phase transion, surface structural change, and irreversible lattice oxygen release. Here we systematically investigated the morphological, structural, and chemical changes of P2-NNMO during high-voltage cycling using a variety of characterization techniques. It was found that the lattice distortion and crystal-plane buckling induced by the P2-O2 phase transition slowed down the Na-ion transport in the bulk and hindered the extraction of the Na ions. The sluggish kinetics was the main reason in reducing the accessible capacity while other interfacial degradation mechanisms played minor roles. Our results not only enabled a more complete understanding of the capacity-fading mechanism of P2-NNMO but also revealed the underlying correlations between lattice doping and the moderately improved cycle performance.

Corrigendum to“Directional construction of Cu2S branch arrays for advanced oxygen evolution reaction”39(2019)61-67

The authors regret that the Fig.S3 in supporting information of this published article needs to be revised.And the BET values are correct and unaffected.All the conclusions in the manuscript are unaffected by this unintentional error.

Probing the Air Storage Failure Mechanism of Ni-Rich Layered Cathode Materials

Ni-rich layered oxide cathode materials,such as LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)(NCM811),exhibit high specific capacity and low cost,and become cathode material preference of high-energy-density Li-ion batteries.However,these cathode materials are not stable and will form Li-poor reconstructed layers and alkaline compounds(Li_(2)CO_(3),LiOH)on the surface during the storage and processing in humid air,resulting in serious deterioration of electrochemical properties.During the past two decades,the consensus on the surface instability mechanism during humid air storage has not been reached.The main controversy focuses on the unstable octahedron mechanism and the Li/H exchange mechanism.Herein,we investigate the instability mechanism in the humid air by conducting scanning electronic microscopy,scanning transmission electron microscopy,and x-ray photoelectron spectroscopy analysis on NCM811 samples stored in designed atmospheres,etc.,and realize that the surface instability of the NCM811 during storage should be mainly originated from Li/H exchange when it contacts with moisture.

对妊娠母猪应用的理想蛋白质模式及其对氨基酸的需要量

由于蛋白质摄入量受限而用于胎儿组织（McPherson等,2004）和乳腺实质组织（Kim等,1999;Ji等,2006）生长以及猪乳合成（Revell等,1998;Jones和Stahly,1999）所需的营养增加,导致妊娠后期和哺乳阶段的母猪处于营养分解状态。母体处于分解状态对胎儿和新生仔猪的生长不利,也增加了它们的患病率和死亡率（Wu等,2006）。在蛋白质摄入量受限的情况下,尤其是在妊娠期和哺乳期,向母猪提供获得最大利用效率的理想平衡氨基酸是重要的。

Non-uniform thermal behavior of single-layer spherical reticulated shell structures considering time-variant environmental factors: analysis and design

Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.

Review—Lithium Carbon Composite Material for Practical Lithium Metal Batteries

Comprehensive Summary Lithium(Li)metal is considered ideal for high-energy-density batteries due to its extremely high specific capacity and low electrochemical potential.However,uncontrolled Li dendrite growth and interfacial instability during repeated Li plating/stripping have limited the practical applicability of Li metal batteries(LMBs).Over the past decades,substantial efforts have been devoted to solving the challenges associated with Li metal anodes.Our research team has developed several Li-carbon(Li-C)microsphere composites in recent years to suppress the formation of Li dendrites and achieve a decent cycle life.In this account,we summarize our advances in the design and application of Li-C composites,which include the developments in the structure and chemical composition of high-specific-capacity Li-C composites,strategies for surface passivation of the micro-spherical Li-C composites,and applications of the Li-C composite in next-generation high-energy-density Li-ion,Li-air,and solid-state LMBs.Finally,we discuss future perspectives for developing high-performance Li metal anodes and endeavors to realize the practical applications of LMBs.

High ceramic content composite solid-state electrolyte films prepared via a scalable solvent-free process

The development of high-performance solid-state electrolyte(SSE)films is critical to the practical application of all-solid-state Li metal batteries(ASSLMBs).However,developing high-performance free-standing electrolyte films remains a challenging task.In this work,we demonstrate a novel scalable solvent-free process for fabricating high ceramic content composite solid-state electrolyte(HCCSE)films.Specifically speaking,a mixture of ceramic and polymer is dry mixed,fibered,and calendered into a free-standing porous ceramic film,on which polymer precursor is coated and polymerized to bridge the inorganic ceramic particles,resulting in a flexible HCCSE film with a ceramic content of up to 80 wt.%.High ceramic content not only leads to high ionic conductivity but also brings good mechanical properties;while the organic phase enables electrode|electrolyte interfacial stability.When Li_(10)GeP_(2)S_(12)(LGPS)and polymeric ionic liquid-based solid polymer electrolytes(PIL-SPEs)were used as the inorganic and organic phases,respectively,the room temperature ionic conductivity of the resulted HCCSE reaches 0.91 mS·cm−1.Based on this HCCSE,Li||Li symmetric battery cycled stably for more than 2,400 h with ultra-low overpotential,and ASSLMBs with different cathodes(LiFePO4 and sulfurized polyacrylonitrile(PAN-S))present small polarization and decent cyclability at room temperature.This work provides a novel scalable solvent-free strategy for preparing high-performance freestanding composite solid-state electrolyte(CSE)film for room temperature ASSLMBs.

高能量密度动力电池材料电化学

汽车产业是国民经济的重要支柱产业.我国的汽车市场销量在过去十几年中高速增长,年销量连续8年世界第一,仅2018年我国汽车销售就高达2808.06万辆(不含重型车辆),占全球(9560万辆)年销量的29.37%.但是,我国汽车保有量水平离发达国家还有较大距离(2016年我国汽车千人保有量140辆,美国797辆,日本591辆,韩国376辆),因此我国汽车消费市场未来还有很大的增长空间(中国汽车流通协会,2018年汽车消费报告,http://www.199it.com/archives/818590.html).然而,随着汽车保有量的增加,由此而引起的能源与环境问题显得日益严重.因此,交通电动化成为未来发展的必然方向.

A polyimide cathode with superior stability and rate capability for lithium-ion batteries

Organic-based electrode materials for lithium-ion batteries (LIBs) are promising due to their high theoretical capacity,structure versatility and environmental benignity.However,the poor intrinsic electric conductivity of most polymers results in slow reaction kinetics and hinders their application as electrode materials for LIBs.A binder-free self-supporting organic electrode with excellent redox kinetics is herein demonstrated via in situ polymerization of a uniform thin polyimide (PI) layer on a porous and highly conductive carbonized nanofiber (CNF) framework.The PI active material in the porous PI@CNF film has large physical contact area with both the CNF and the electrolyte thus obtains superior electronic and ionic conduction.As a result,the PI@CNF cathode exhibits a discharge capacity of 170 mAh·g^-1 at 1 C (175 mA·g^-1),remarkable rate-performance (70.5% of 0.5 C capacity can be obtained at a 100 C discharge rate),and superior cycling stability with 81.3% capacity retention after 1,000 cycles at 1 C.Last but not least,a four-electron transfer redox process of the PI polymer was realized for the first time thanks to the excellent redox kinetics of the PI@CNF electrode,showing a discharge capacity exceeding 300 mAh·g^-1 at a current of 175 mA·g^-1.

TiC/C core/shell nanowires arrays as advanced anode of sodium ion batteries

High-perfo rmance anodes of sodium ion batteries(SIBs)largely depends on rational architecture design and binder-free smart hybridization.Herein,we report TiC/C core/shell nanowires arrays prepared by a one-step chemical vapor deposition(CVD)method and apply it as the anode of SIBs for the first time.The conductive TiC core is intimately decorated with carbon shell.The as-obtained TiC/C nanowires are homogeneously grown on the substrate and show core/shell heterostructure and porous architecture with high electronic conductivity and reinforced stability.Owing to these merits,the TiC/C electrode displays good rate performance and outstanding cycling performance with a capacity of 135.3 mAh/g at 0.1 A/g and superior capacity retention of 90.14%after 1000 cycles at 2 A/g.The reported strategy would provide a promising way to construct binder-free arrays electrodes for sodium ion storage.

Highly stable lithium anode enabled by self-assembled monolayer of dihexadecanoalkyl phosphate

Li has been considered as the ultimate anode material for high energy density secondary Li batteries.However,its practical application has been limited due to its low Coulombic efficiency(CE)and the formation of lithium dendrites.Recently,we have developed a microspherical Li-carbon nanotube(Li-CNT)composite material passivated with octadecylphosphonic acid(OPA)self-assembled monolayer(SAM)exhibiting suppressed lithium dendrite formation and improved environmental/electrochemical stability.In this work,we demonstrated the significantly enhanced passivation effects of a SAM using dihexadecanoalkyl phosphate(DHP),a molecule that is comprised of double hydrophobic alkyl chains and forms a denser SAM on surfaces with large curvature.As a result,the DHP SAM delivers superior environmental and electrochemical stability to the OPA passivated Li-CNT material.In specific,the DHP passivated Li-CNT composite(DHP-Li-CNT)delivers a high CE of 99.25%under a 33.3%depth of discharge(DOD)at 1 C,when it is paired with a LiFePO4 cathode.The evolution of the SAM during cycling and the effects of DOD and current density on the CE of the DHP-Li-CNT anode have also been investigated.The improved SAM passivation constitutes an important step in achieving the goal of practically applicable Li anodes.

Trimethoxyboroxine as an electrolyte additive to enhance the 4.5​V cycling performance of a Ni-rich layered oxide cathode

Ni-rich layered oxides are attractive cathode materials for advanced lithium-ion batteries(LIBs)due to their high energy density.However,their large-scale application is seriously hindered by their interfacial instability,especially at a high cut-off potential.Here,we demonstrate that trimethoxyboroxine(TMOBX)is an effective film-forming additive to address the interfacial instability of LiNi0.8Co0.1Mn0.1O_(2)(NCM811)material at a high cut-off voltage of 4.5​V.We find that TMOBX decomposes before carbonate solvent and forms a thin cathode electrolyte interphase(CEI)layer on the surface of the NCM811 material.This TMOBX-formed CEI significantly suppresses electrolyte decomposition at a high potential and inhibits the dissolution of transition metals from NCM811 during cycling.In addition,electron-deficient borate compounds coordinate with anions(PF6^(−),F^(-) etc.)and H2O in the battery,further improving the battery's stability.As a result,adding 1.0​wt%of TMOBX boosts the capacity retention of a Li||NCM811​cell from 68.72%to 86.60%after 200 cycles at 0.5C in the range of 2.8–4.5​V.