Tuning Li/Ni mixing by reactive coating to boost the stability of cobalt-free Ni-rich cathode

Cobalt-free cathode materials are attractive for their high capacity and low cost,yet they still encounter issues with structural and surface instability.AlPO_(4),in particular,has garnered attention as an effective stabilizer for bulk and surface.However,the impact of interfacial reactions and elemental interdiffusion between AlPO_(4) and LiNi_(0.95)Mn_(0.05)O_(2) upon sintering on the bulk and surface remains elusive.In this study,we demonstrate that during the heat treatment process,AlPO_(4) decomposes,resulting in Al doping into the bulk of the cathode through elemental interdiffusion.Simultaneously,PO_(4)^(3-)reacts with the surface Li of material to form a Li_3PO_(4) coating,inducing lithium deficiency,thereby increasing Li/Ni mixing.The suitable Li/Ni mixing,previously overlooked in AlPO_(4) modification,plays a pivotal role in stabilizing the bulk and surface,exceeding the synergy of Al doping and Li_3PO_(4) coating.The presence of Ni^(2+)ions in the lithium layers contributes to the stabilization of the delithiated structure via a structural pillar effect.Moreover,suitable Li/Ni mixing can stabilize the lattice oxygen and electrode-electrolyte interface by increasing oxygen removal energy and reducing the overlap between the Ni^(3+/4+)e_g and O^(2-)2p orbitals.These findings offer new perspectives for the design of stable cobalt-free cathode materials.

Accurate estimation of Li/Ni mixing degree of lithium nickel oxide cathode materials

Li/Ni mixing negatively influences the discharge capacity of lithium nickel oxide and high-nickel ternary cathode materials.However,accurately measuring the Li/Ni mixing degree is difficult due to the preferred orientation of labbased XRD measurements using Bragg–Brentano geometry.Here,we find that employing spherical harmonics in Rietveld refinement to eliminate the preferred orientation can significantly decrease the measurement error of the Li/Ni mixing ratio.The Li/Ni mixing ratio obtained from Rietveld refinement with spherical harmonics shows a strong correlation with discharge capacity,which means the electrochemical capacity of lithium nickel oxide and high-nickel ternary cathode can be estimated by the Li/Ni mixing degree.Our findings provide a simple and accurate method to estimate the Li/Ni mixing degree,which is valuable to the structural analysis and screening of the synthesis conditions of lithium nickel oxide and high-nickel ternary cathode materials.

A universal multifunctional dual cation doping strategy towards stabilized ultra-high nickel cobalt-free lithium layered oxide cathode

Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries(LIBs)because of their relatively high capacity and low cost.Nevertheless,the high nickel content would induce bulk structure degradation and interfacial environment deterioration,and the absence of Co element reduces the lithium diffusion kinetics,severely limiting the performance liberation of this kind of cathodes.Herein,a multifunctional Ti/Zr dual cation co-doping strategy has been employed to improve the lithium storage performance of LiNi_(0.9)Mn_(0.1)O_(2)(NM91)cathode.On the one hand,the Ti/Zr co-doping weakens the Li^(+)/Ni^(2+)mixing through magnetic interactions due to the inexistence of unpaired electrons for Ti^(4+)and Zr^(4+),increasing the lithium diffusion rate and suppressing the harmful coexistence of H1 and H2 phases.On the other hand,they enhance the lattice oxygen stability because of the strong Ti-O and Zr-O bonds,inhibiting the undesired H3 phase transition and lattice oxygen loss,improving the bulk structure and cathode-electrolyte interface stability.As a result,the Ti/Zr co-doped NM91(NMTZ)exhibits a 91.2%capacity retention rate after 100 cycles,while that of NM91 is only82.9%.Also,the NMTZ displays better rate performance than NM91 with output capacities of 115 and93 mA h g^(-1)at a high current density of 5 C,respectively.Moreover,the designed NMTZ could enable the full battery to deliver an energy density up to 263 W h kg^(-1),making the ultra-high nickel cobaltfree lithium layered oxide cathode closer to practical applications.

Addressing cation mixing in layered structured cathodes for lithium-ion batteries:A critical review

High-performance lithium-ion batteries(LIB)are important in powering emerging technologies.Cathodes are regarded as the bottleneck of increasing battery energy density,among which layered oxides are the most promising candidates for LIB.However,a limitation with layered oxides cathodes is the transition metal and Li site mixing,which significantly impacts battery capacity and cycling stability.Despite recent research on Li/Ni mixing,there is a lack of comprehensive understanding of the origin of cation mixing between the transition metal and Li;therefore,practical means to address it.Here,a critical review of cation mixing in layered cathodes has been provided,emphasising the understanding of cation mixing mechanisms and their impact on cathode material design.We list and compare advanced characterisation techniques to detect cation mixing in the material structure;examine methods to regulate the degree of cation mixing in layered oxides to boost battery capacity and cycling performance,and critically assess how these can be applied practically.An appraisal of future research directions,including superexchange interaction to stabilise structures and boost capacity retention has also been concluded.Findings will be of immediate benefit in the design of layered cathodes for high-performance rechargeable LIB and,therefore,of interest to researchers and manufacturers.

Optical and electrical properties of BaSnO_(3) and In_2O_(3) mixed transparent conductive films deposited by filtered cathodic vacuum arc technique at room temperature

For the crystalline temperature of BaSnO_(3)(BTO)was above 650℃,the transparent conductive BTO-based films were always deposited above this temperature on epitaxy substrates by pulsed laser deposition or molecular beam epitaxy till now which limited there application in low temperature device process.In the article,the microstructure,optical and electrical of BTO and In_(2)O_(3) mixed transparent conductive BaInSnO_(x)(BITO)film deposited by filtered cathodic vacuum arc technique(FCVA)on glass substrate at room temperature were firstly reported.The BITO film with thickness of 300 nm had mainly In_(2)O_(3) polycrystalline phase,and minor polycrystalline BTO phase with(001),(011),(111),(002),(222)crystal faces which were first deposited at room temperature on amorphous glass.The transmittance was 70%–80%in the visible light region with linear refractive index of 1.94 and extinction coefficient of 0.004 at 550-nm wavelength.The basic optical properties included the real and imaginary parts,high frequency dielectric constants,the absorption coefficient,the Urbach energy,the indirect and direct band gaps,the oscillator and dispersion energies,the static refractive index and dielectric constant,the average oscillator wavelength,oscillator length strength,the linear and the third-order nonlinear optical susceptibilities,and the nonlinear refractive index were all calculated.The film was the n-type conductor with sheet resistance of 704.7Ω/□,resistivity of 0.02Ω⋅cm,mobility of 18.9 cm2/V⋅s,and carrier electron concentration of 1.6×10^(19) cm^(−3) at room temperature.The results suggested that the BITO film deposited by FCVA had potential application in transparent conductive films-based low temperature device process.

Mixed polyanion cathode materials:Toward stable and high-energy sodium-ion batteries

Sodium-ion batteries(SIBs)are considered as one of the most fascinating alternatives to lithium-ion batteries for grid-scale energy storage applications because of the low cost and wide abundance of sodium resources.Among various cathode materials,mixed polyanion compounds come into the spotlight as promising electrode materials due to their superior electrochemical properties,such as high working voltage,long cycling stability,and facile reaction kinetics.In this review,we summarize the recent development in the exploration of different mixed polyanion cathode materials for SIBs.We provide a comprehensive understanding of the structure-composition-performance relationship of mixed polyanion cathode materials together with the discussion of their sodium storage mechanisms.It is anticipated that further innovative works on the material design of advanced cathode materials for batteries can be inspired.

CoSnO_(3)/C nanocubes with oxygen vacancy as high-capacity cathode materials for rechargeable aluminum batteries

Rechargeable aluminum batteries(RABs)are attractive cadidates for next-generation energy storage and conversion,due to the low cost and high safety of Al resources,and high capacity of metal Al based on the three-electrons reaction mechanism.However,the development of RABs is greatly limited,because of the lack of advanced cathode materials,and their complicated and unclear reaction mechanisms.Exploring the novel nanostructured transition metal and carbon composites is an effective route for obtaining ideal cathode materials.In this work,we synthesize porous CoSnO_(3)/C nanocubes with oxygen vacancies for utilizing as cathodes in RABs for the first time.The intrinsic structure stability of the mixed metal cations and carbon coating can improve the cycling performance of cathodes by regulating the internal strains of the electrodes during volume expansion.The nanocubes with porous structures contribute to fast mass transportation which improves the rate capability.In addition to this,abundant oxygen vacancies promote the adsorption affinity of cathodes,which improves storage capacity.As a result,the CoSnO_(3)/C cathodes display an excellent reversible capacity of 292.1 mAh g^(-1) at 0.1 A g^(-1),a good rate performance with 109 mAh g^(-1) that is maintained even at 1 A g^(-1) and the provided stable cycling behavior for 500 cycles.Besides,a mechanism of intercalation of Al^(3+)within CoSnO_(3)/C cathode is proposed for the electrochemical process.Overall,this work provides a step toward the development of advanced cathode materials for RABs by engineering novel nanostructured mixed transition-metal oxides with carbon composite and proposes novel insights into chemistry for RABs.

Cation mixing (Li_(0.5)Fe_(0.5))_2SO_4F cathode material for lithium-ion batteries

We study the crystal structure of a triplite-structured （Li0.5Fe0.5）SO4F with full Li＋/Fe2＋ mixing. This promising polyanion cathode material for lithium-ion batteries operates at 3.9 V versus Li＋/Li with a theoretical capacity of 151 mAh/g. Its unique cation mixing structure does not block the Li＋ diffusion and results in a small lattice volume change during the charge/discharge process. The calculations show that it has a three-dimensional network for Li-ion migration with an activation energy ranging from 0.53 eV to 0.68 eV, which is comparable with that in LiFePO4 with only one-dimensional channels. This work suggests that further exploring cathode materials with full cation mixing for Li-ion batteries will be valuable.

Coupling effect of the conductivities of Li ions and electrons by introducing LLTO@C fibers in the LiNi0.8Co0.15Al0.05O2 cathode

To probe the coupling effect of the electron and Li ion conductivities in Ni-rich layered materials(LiNi0.8Co0.15Al0.05O2,NCA),lithium lanthanum titanate(LLTO)nanofiber and carbon-coated LLTO fiber(LLTO@C)materials were introduced to polyvinylidene difluoride in a cathode.The enhancement of the conductivity was indicated by the suppressed impedance and polarization.At 1 and 5 C,the cathodes with coupling conductive paths had a more stable cycling performance.The coupling mechanism was analyzed based on the chemical state and structure evolution of NCA after cycling for 200 cycles at 5 C.In the pristine cathode,the propagation of lattice damaged regions,which consist of high-density edge-dislocation walls,destroyed the bulk integrity of NCA.In addition,the formation of a rock-salt phase on the surface of NCA caused a capacity loss.In contrast,in the LLTO@C modified cathode,although the formation of dislocation-driven atomic lattice broken regions and cation mixing occurred,they were limited to a scale of several atoms,which retarded the generation of the rock-salt phase and resulted in a pre-eminent capacity retention.Only NiO phase“pitting”occurred.A mechanism based on the synergistic transport of Li ions and electrons was proposed.

Pervoskite-type Bao.sSro.sAl0.1Fe0.9O3-δ as Intermediate-Temperature Solid Oxide Fuel Cell Cathode

A cobalt-free perovskite-type Ba0.5Sr0.5A10.1Fe0.9O3-δ （BSAF） chemically studied as solid oxide fuel cell （SOFC） cathode. The ductivity, and electrode polarizations in symmetrical cell based is developed and electro- structures, electrical con- on mixed ion conducting electrolyte were investigated, respectively. The temperature dependence of conductivity of BSAF in air shows a typical semiconductor behavior with positive temperature coefficient up to 450℃ where the conductivity reaches 14.0 S/cm while above this temperature the negative temperature coefficient dominates the total conductivity. Electrochemical charac- terizations show desirable polarization resistance of BSAF cathode in a symmetric cell based on mixed ion conducting electrolyte at 650-700℃, A single SOFC with BSAF cathode shows OCV of 1.0 V and maximum output of 420 mW/cm2 at 700 ℃ with humidified hydrogen fuel and static air oxidant.

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.

Overlooked impact of precursor mixing:Implications in the electrochemical performance of battery electrode materials

Solid-state reactions are an essential part of the synthesis of various cathode materials for lithium-ion batteries(LIBs).Despite the simplicity and effectiveness for mass production,a subtle variation in synthesis conditions can often give rise to unexpectedly different physical properties,significantly affecting the electrochemical performance of electrode materials.However,this aspect has long been overlooked in the LIB community,which should focus on advancement in understanding the influence of synthesis conditions.As solid-state reactions occur only at the interface of precursor materials,maximizing the interfacial contact area between mixed precursor powders is crucial.Mechanical milling and/or mixing are common practices that have been performed in both academia and industry for this purpose.Unlike the common belief that this pre-treatment before calcination would be of great benefit for the preparation of high-performance LIB materials,we revealed in this work that this practice is not always successful for this goal.In our case study of the preparation of LiCoO_(2),we demonstrated that mechanical mixing-a routinely implemented process for homogeneous mixing of precursors-can be harmful if it is performed without assuring optimal working conditions for mixing.The underlying reasons for this surprising result are elucidated in this work,and we hope that this new insight can help avoid the potential pitfall of routine implementations performed for LIB materials.

Mixed ion-electron conducting Li_(3)P for efficient cathode prelithiation of all-solid-state Li-ion batteries

All-solid-state batteries(ASSBs)using sulfide electrolytes hold promise for next-generation battery technology.Although using a pure Li metal anode is believed to maximize battery energy density,numerous recent studies have implicated that Li-ion anodes(e.g.,graphite and Si)are more realistic candidates due to their interfacial compatibility with sulfide electrolytes.However,those Li-ion ASSBs suffer from an issue similar to liquid Li-ion batteries,which is a loss of active Li inventory owing to interfacial side reactions between electrode components,resulting in reduced available capacities and shortened cycle life.Herein,for the first time,we explore the potential of Li_(3)P for cathode prelithiation of Li-ion ASSBs.We identify that the crystallized Li_(3)P(c-Li_(3)P)has room-temperature ionic and electronic conductivities of both over 1o-4 s/cm.Such a mixed ion-electron conduct-ing feature ensures that the neat c-LisP affords a high Li+-releasing capacity of 983 mAh/g in ASSBs during the first charging.Moreover,the electro-chemical delithiation of c-LisP takes place below 2 V versus Li+/Li,while its lithiation dominates below 1 V versus Lit/Li.Once used as a cathode prelithiation regent for ASSBs,c-Li_(3)P only functions as a Li+donor without lithiation activity and can adequately compensate for the Li loss with minimal dosage added.Besides mitigating first-cycle Li loss,c-LisP prelithiation can also improve the battery cyclability by sustained release of low-dosage Li+ions in subsequent cycles,which have been embodied in several full ASSBs by coupling a LiCoO2 cathode with various types of anodes(including graphite,in foil,Sb,and Si anode).Our work provides a universal cathode prelithiation strategy for high-efficiency Li-ion AsSBs.

Ternary-phase layered cathodes toward ultra-stable and highrate sodium ion storage

With the shortage of lithium resources,sodiumion batteries(SIBs)are considered one of the most promising candidates for lithium-ion batteries.P2-type and O3-type layered oxides are one of the few cathodes that can access high energy density.However,they usually exhibit structural change,capacity decay,and slow Na ion kinetic.Herein,we present layered ternary-phase cathodes with P2,P3 and O3 phases by a lattice doping strategy,which is demonstrated by X-ray diffraction(XRD)refinement.Combining the characteristics of P2,P3 and O3 phases,the layered composites show performance improvement during long-term battery cycling.In particular,Na_(0.7)Li_(0.1)Co_(0.3-)Fe_(0.3)Mn_(0.3)O_(2)(NLCFM)delivers a reversible capacity of120.1 mAh·g^(-1)at 0.1C(1.0C=175 mA·g^(-1))with a superior capacity retention of 72.5%after 1000 cycles at10.0C.This work offers insights into the development of advanced cathode materials for SIBs.

A simple physical mixing method for MnO2/MnO nanocomposites with superior Zn^2+storage performance

MnO2/MnO cathode material with superior Zn^2+storage performance is prepared through a simple physical mixing method.The MnO2/MnO nanocomposite with a mixed mass ratio of 12:1 exhibits the highest specific capacity(364.2 mA·h/g at 0.2C),good cycle performance(170.4 mA·h/g after 100 cycles)and excellent rate performance(205.7 mA·h/g at 2C).Analysis of cyclic voltammetry(CV)data at various scan rates shows that both diffusioncontrolled insertion behavior and surface capacitive behavior contribute to the Zn2+storage performance of MnO2/MnO cathodes.And the capacitive behavior contributes more at high discharge rates,due to the short paths of ion diffusion and the rapid transfer of electrons.

微波烧结制备钨锇混合基扩散阴极及其发射性能

采用固–液混合法制备出不同锇(Os)含量(原子数分数)的亚微米级钨锇混合粉体,通过微波烧结获得了孔道结构均匀的钨锇混合基扩散型阴极。电子发射测试结果表明,元素Os的加入使浸渍型钨基阴极的发射性能有明显提高。对比不同锇含量的混合基阴极,发现W-25Os阴极(Os原子数分数为25%)具有相对较低的逸出功和较高的发射电流密度,其在1100℃时脉冲发射电流密度为42.86 A·cm^(-2),斜率为1.40,发射电流密度是同等工作条件下传统钡钨阴极的1.7倍,达到了覆膜M型阴极的电子发射水平。W-25Os混合基阴极的有效逸出功最低为1.93 eV,有利于活性自由钡(Ba)的生成,表层元素摩尔比Ba:(W+Os)为0.83:1.00,比传统钡钨阴极中Ba:W(约为0.50:1.00)摩尔比有了明显提高。

镁掺杂协同氧化铝包覆优化锂离子电池高镍正极材料

锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研究针对高镍三元材料阳离子无序排列严重和循环稳定性差的问题,通过共沉淀法在前驱体合成过程中将Mg掺杂进入晶体,得到Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)(Mg1.0)活性材料,进一步利用液相法在材料表面包覆Al_(2)O_(3),成功制备Al_(2)O_(3)涂覆的Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)复合材料(Mg1.0@Al)。X射线衍射(XRD)结果表明,Mg掺杂能够有效扩大材料层间距,抑制阳离子混排;扫描电子显微镜(SEM)结合透射电子显微镜(TEM)结果表明,改性未对NCM811材料整体形貌造成影响,同时能够明显地观察到通过液相法在材料表面包覆的Al_(2)O_(3)涂层。电化学测试结果表明,镁铝协同改性可以稳定NCM811材料结构,减少阴极的界面极化,遏制材料与电解液发生副反应,使得材料表现出优越的电化学性能。Mg1.0@Al在1 C循环100次后表现出稳定的放电电压(ΔV=5.2 m V)、较低的电荷转移阻抗(R_(ct)=51.66Ω)和卓越的锂离子扩散系数(D_(Li)=4.05×10^(-14)cm^(2)/s)。同时,Mg1.0@Al材料在2.8~4.3V电压范围下,展现出卓越的循环性能和倍率性能:1 C下循环100次和400次后仍有188.58 m Ah/g和147.47 m Ah/g的放电比容量,容量保持率分别为95.18%和74.54%;5 C大倍率电流下,放电比容量高达146.3 m Ah/g。

锂离子电池高镍正极材料中镍锂混排研究进展

锂离子电池高镍正极材料因具有高能量密度已经被广泛研究,并且广泛应用于新能源汽车及储能器件。镍锂混排是高镍正极材料中常见的物理现象,能对高镍锂离子电池的放电比容量、倍率性能、循环性能、结构稳定性能及安全性能产生重要影响。从镍锂混排的定义、形成机理、检测方法及对高镍锂电池正极材料的影响进行了分析与讨论。

660 MW机组凝结水精处理再生系统问题分析及处理

某660 MW机组冷凝水精处理再生系统在长期运行中出现阴阳树脂分离效果差,存在阴树脂混入阳树脂的情况,使冷凝水精处理再生过程中阳树脂发生二次感染,危害再生运行效果,造成混床循环系统制水量低,树脂交叉感染也导致混床出水氯离子含量超标。本文通过对再生系统存在的问题进行对比分析,进行了设备技术改进和程序优化工作,改造后的凝结水精处理再生系统运行较佳,明显增加左右混床周期内制水量,混床出水水质更好。

水罐内表面强制电流阴极保护阳极的布置

以某3400 m^(3)碳钢注水罐内表面强制电流阴极保护辅助阳极用量计算及布置为例,对比了三种辅助阳极布置方案,讨论了阳极串数量,单串中阳极的数量,阳极与罐壁、罐底和液面的距离等对注水罐内表面强制电流阴极保护系统中辅助阳极布置有效性的影响。结果表明:采用方案三的防护效果最佳。辅助阳极布置过程中,需要进行阳极串最上方阳极顶部与储罐内液面的距离、2.5Sab(阳极串的底部与罐底间的距离)等参数的计算和核算,确定罐壁各部位均处于保护,从而确保采取的阳极设置方案合理有效。