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.

Boosting oxygen reduction activity and CO_(2) resistance on bismuth ferrite-based perovskite cathode for low-temperature solid oxide fuel cells below 600℃

Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)FeO_(3-δ) perovskites as highly-active catalysts for LT-SOFCs.Sm doping can significantly enhance the electrocata lytic activity and chemical stability of cathode.At 600℃,Bi_(0.675)Sm_(0.025)Sr_(0.3)FeO_(3-δ)(BSSF25) cathode has been found to be the optimum composition with a polarization resistance of 0.098 Ω cm^2,which is only around 22.8% of Bi_(0.7)Sr_(0.3)FeO_(3-δ)(BSF).A full cell utilizing BSSF25 displays an exceptional output density of 790 mW cm^(-2),which can operate continuously over100 h without obvious degradation.The remarkable electrochemical performance observed can be attributed to the improved O_(2) transport kinetics,superior surface oxygen adsorption capacity,as well as O_(2)p band centers in close proximity to the Fermi level.Moreover,larger average bonding energy(ABE) and the presence of highly acidic Bi,Sm,and Fe ions restrict the adsorption of CO_(2) on the cathode surface,resulting in excellent CO_(2) resistivity.This work provides valuable guidance for systematic design of efficient and durable catalysts for LT-SOFCs.

Mg/Fe site-specific dual-doping to boost the performance of cobalt-free nickle-rich layered oxide cathode for high-energy lithium-ion batteries

Layer-type LiNi0.9Mn0.1O2is promising to be the primary cathode material for lithium-ion batteries(LIBs)due to its excellent electrochemical performance.Unfortunately,the cathode with high nickel content suffers from severely detrimental structural transformation that causes rapid capacity attenuation.Herein,site-specific dual-doping with Fe and Mg ions is proposed to enhance the structural stability of LiNi0.9Mn0.1O2.The Fe3+dopants are inserted into transition metal sites(3b)and can favorably provide additional redox potential to compensate for charge and enhance the reversibility of anionic redox.The Mg ions are doped into the Li sites(3a)and serve as O_(2)^(-)-Mg^(2+)-O_(2)^(-)pillar to reinforce the electrostatic cohesion between the two adjacent transition-metal layers,which further suppress the cracking and the generation of harmful phase transitions,ultimately improving the cyclability.The theoretical calculations,including Bader charge and crystal orbital Hamilton populations(COHP)analyses,confirm that the doped Fe and Mg can form stable bonds with oxygen and the electrostatic repulsion of O_(2)^(-)-O_(2)^(-)can be effectively suppressed,which effectively mitigates oxygen anion loss at the high delithiation state.This dual-site doping strategy offers new avenues for understanding and regulating the crystalline oxygen redox and demonstrates significant potential for designing high-performance cobalt-free nickel-rich cathodes.

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.

Stabilized cobalt-free lithium-rich cathode materials with an artificial lithium fluoride coating

Iron-substituted cobalt-free lithium-rich manganese-based materials,with advantages of high specific capacity,high safety,and low cost,have been considered as the potential cathodes for lithium ion batteries.However,challenges,such as poor cycle stability and fast voltage fade during cycling under high potential,hinder these materials from commercialization.Here,we developed a method to directly coat LiF on the particle surface of Li_(1.2)Ni_(0.15)Fe_(0.1)Mn_(0.55O2).A uniform and flat film was successfully formed with a thickness about 3 nm,which can effect-ively protect the cathode material from irreversible phase transition during the deintercalation of Li^(+).After surface coating with 0.5wt%LiF,the cycling stability of Li_(1.2)Ni_(0.15)Fe_(0.1)Mn_(0.55O2) cycled at high potential was significantly improved and the voltage fade was largely suppressed.

Achieving exceptional activity and durability toward oxygen reduction based on a cobalt-free perovskite for solid oxide fuel cells

In response to the shortcomings of cobalt-rich cathodes, iron-based perovskite oxides appear as promising alternatives for solid oxide fuel cells (SOFCs). However, their inferior electrochemical performance at reduced temperatures (<700 ℃) becomes a major bottleneck for future progress. Here, a novel cobalt-free perovskite Ba_(0.75)Sr_(0.25)Fe_(0.875)Ga_(0.125)O_(3−δ) (BSFG) is developed as an efficient oxygen reduction electrode for SOFCs, featuring cubic-symmetry structure, large oxygen vacancy concentration and fast oxygen transport. Benefiting from these merits, cells incorporated with BSFG achieve exceptionally high electrochemical performance, as evidenced by a low polarization area-specific resistance of 0.074 Ω cm^(2) and a high peak power density of 1145 mW cm^(−2) at 600 ℃. Meanwhile, a robust short-term performance stability of BSFG cathode can be ascribed to the stable crystalline structure and favorable thermal expansion behavior. First-principles computations are also conducted to understanding the superior activity and durability toward oxygen reduction reaction. These pave the way for rationally developing highly active and robust cobalt-free perovskite-type cathode materials for reduced-temperature SOFCs.

In-situ fabrication of dual porous titanium dioxide films as anode for carbon cathode based perovskite solar cell

We develop a dual porous （DP） TiO2 film for the electron transporting layer （ETL） in carbon cathode based perovskite solar cells （C-PSCs）. The DP TiO2 film was synthesized via a facile PS-templated method with the thickness being controlled by the spin-coating speed. It was found that there is an optimum DP TiO2 film thickness for achieving an effective ETL, a suitable perovskite]TiO2 interface, an efficient light harvester and thus a high performance C-PSC. In particular, such a DP TiO2 film can act as a scaffold for complete-filling of the pores with perovskite and for forming high-quality perovskite crystals that are seamlessly interfaced with Ti02 to enhance interracial charge injection. Leveraging the unique advantages of DP TiO2 ETL, together with a dense-packed and pinhole-free TiO2 compact layer, PCE of the C-PSCs has reached 9.81% with good stability.

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.

Cobalt-Free BaFe_(0.6)Zr_(0.1)Y_(0.3)O_(3−δ)Oxygen Electrode for Reversible Protonic Ceramic Electrochemical Cells

Reversible protonic ceramic electrochemical cells(R-PCECs)are ideal,high-effi ciency devices that are environmentally friendly and have a modular design.This paper studies BaFe_(0.6)Zr_(0.1)Y_(0.3)O_(3−δ)(BFZY3)as a cobalt-free perovskite oxygen electrode for high-performance R-PCECs where Y ions doping can increase the concentration of oxygen vacancies with a remarkable increase in catalytic performance.The cell with confi guration of Ni-BZCYYb/BZCYYb/BFZY3 demonstrated promising performance in dual modes of fuel cells(FCs)and electrolysis cells(ECs)at 650℃with low polarization resistance of 0.13Ωcm^(2),peak power density of 546.59 mW/cm^(2)in FC mode,and current density of−1.03 A/cm^(2)at 1.3 V in EC mode.The alternative operation between FC and EC modes for up to eight cycles with a total of 80 h suggests that the cell with BFZY3 is exceptionally stable and reversible over the long term.The results indicated that BFZY3 has considerable potential as an air electrode material for R-PCECs,permitting effi cient oxygen reduction and water splitting.

Synthesis and Electrical Properties of La_(0.6)M_(0.4)FeO_(3-δ)(M=Ca, Sr, Ba) as Cathodes for SOFCs

A series samples of La0.6M0.4FeO3-δ （M = Ca, Sr, process （GNP）. FTIR, TG-DSC, XRD and TEM techniques Ba） perovskite-type oxides were prepared by glycine nitrate were used to characterize the chemical constitution, thermal stability and phase structure. The electrical conductivity of the samples was investigated by four-probe technique. With the increase of substituted-ionic radius, the temperature of phase formation increases, and the solid solubility decreases gradually, respectively. The La0.6Ca0.4FeO3-δ（LCF）powder is pure cubic perovskite-type crystalline after fired at 850℃ for 2 h. The XRD patterns of La0.6Sr0.4FeO3-δ（LSF） powder shows a small quantity of SrO peaks sintered at 1050℃ for 2 h. The electrical conductivity of LCF and LSF at 500 - 800℃ is over 100 S·cm^ - 1, and the value of LCF is 1170 S·cm^ - 1 at 800℃, which indicate that LCF and LSF may be used as a profitable cathode for IT-SOFCs. The characteristic of La0.6 Ba0.4FeO3-δ（LBF） is poor, and the electrical conductivity at intermediate temperatures is 1/20 less than that of LSF.

Layered perovskite oxide Y_(0.8)Ca_(0.2)BaCoFeO_(5+δ) as a novel cathode material for intermediate-temperature solid oxide fuel cells

A layered perovskite oxide Y0.8Ca0.2BaCoFeO5＋δ（YCBCF） was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells （IT-SOFCs） by citric acid-nitrates self-propagating combustion method. The phase and micro-structure of YCBCF were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The aver-age thermal expansion coefficient （TEC） of YCBCF was 14.6×10–6 K–1, which was close to other materials of SOFC at the range of RT–1000 oC. An open-circuit potential of 0.75 V and a maximum output power density of 426 mW/cm2 were obtained at 650 oC in a Sm0.2Ce0.8O1.9 （SDC）-based anode-supported SOFC by using humidified （~3%H2O） hydrogen as fuel and static air as oxidant. The results indicated that the YCBCF was a promising cathode candidate for IT-SOFCs.

Perovskite Cathode Materials for Low‑Temperature Solid Oxide Fuel Cells:Fundamentals to Optimization

Acceleration of the oxygen reduction reaction at the cathode is paramount in the development of low-temperature solid oxide fuel cells.At low operating temperatures between 450 and 600℃,the interactions between the surface and the bulk of the cathode materials greatly impact the electrode kinetics and consequently determine the overall efficacy and long-term stability of the fuel cells.This review will provide an overview of the recent progress in the understanding of surface-bulk interactions in perovskite oxides as well as their impact on cathode reactivity and stability.This review will also summarize current strategies in the development of cathode materials through bulk doping and surface functionalization.In addition,this review will highlight the roles of surface segregation in the mediation of surface and bulk interactions,which have profound impacts on the properties of cathode surfaces and the bulk and therefore overall cathode performance.Although trade-offs between reactivity and stability commonly exist in terms of catalyst design,opportunities also exist in attaining optimal cathode performance through the modulation of both cathode surfaces and bulk using combined strategies.This review will conclude with future research directions involving investigations into the role of oxygen vacancy and mobility in catalysis,the rational modulation of surface-bulk interactions and the use of advanced fabrication techniques,all of which can lead to optimized cathode performance.

Enhanced rate capability and mitigated capacity decay of ultrahigh-nickel cobalt-free LiNi_(0.9)Mn_(0.1)O_(2) cathode at high-voltage by selective tungsten substitution

Owing to the further requirement for electric vehicle market, it is appropriate to lower the cost and improve the energy density of lithium-ion batteries by adopting the Co-free and Ni-rich layered cathodes.However, their practical application is severely limited by structural instability and slow kinetics. Herein,ultrahigh-nickel cobalt-free LiNi_(0.9)Mn_(0.1)O_(2) cathode is elaborate designed via in-situ trace substitution of tungsten by a wet co-precipitation method following by high-temperature sintering. It is revealed that the in-situ doping strategy of high valence W^(6+) can effectively improve the structure stability by reducing irreversible phase transition and suppressing the formation of microcracks. Moreover, the transformed fine particles determined by W-doping can facilitate the kinetic characteristics by shortening Li^(+) diffusion paths. As expected, 0.3 mol% W-doped LiNi_(0.9)Mn_(0.1)O_(2) cathode exhibits a high specific capacity of 143.5 mAh/g after 200 cycles at high rate of 5 C in the wide potential range of 2.8-4.5 V, representing a potential next-generation cathode with low-cost, high energy-density and fast-charging capabilities.

High-performance, stable and low-cost mesoscopic perovskite （CH3NH3PbI3） solar cells based on poly（3-hexylthiophene）- modified carbon nanotube cathodes

This work explores the use of poly（3- hexylthiophene） （P3HT） modified carbon nanotubes （CNTs@P3HT） for the cathodes of hole transporter free, mesoscopic perovskite （CH3NH3PbI3） solar cells （PSCs）, simultaneously achieving high-performance, high stability and low-cost PSCs. Here the thin P3HT modifier acts as an electron blocker to inhibit electron transfer into CNTs and a hydrophobic polymer binder to tightly cross-link the CNTs together to compact the carbon electrode film and greatly stabilize the solar cell. On the other hand, the presence of CNTs greatly improve the conductivity of P3HT. By optimizing the concentration of the P3HT modifier （2 mg/mL）, we have improved the power conversion efficiencies （PCEs） of CNTs@P3HT based PSCs up to 13.43% with an average efficiency of 12.54%, which is much higher than the pure CNTs based PSCs （best PCE 10.59%） and the sandwich-type P3HT/CNTs based PSCs （best PCE 9.50%）. In addition, the hysteresis of the CNTs@P3HT based PSCs is remarkably reduced due to the intimate interface between the perovskite and CNTs@P3HT electrodes. Degradation of the CNTs@ P3HT based PSCs is also strongly retarded as compared to cells employing the pure CNTs electrode when exposed to the ambient condition of 20%- 40% humidity.

Interface Engineering of Inverted Perovskite Solar Cells Using a Self-doped Perylene Diimide Ionene Terpolymer as a Thickness-Independent Cathode Interlayer

Inverted perovskite solar cells(PerSCs)are a highly promising candidate in the photovoltaic field due to their low-temperature fabrication process,negligible hysteresis,and easy integration with Si-based solar cells.A cathode interlayer(CIL)is necessary in the development of inverted devices to reduce the trap density and energy barrier between the electron transport layer(ETL)and the electrode.However,most CILs are highly thickness-sensitive due to low conductivity and poor film-forming.In this study,we report on a self-doping perylene imide-based ionene polymer(PNPDIN)used as CIL material to modify electrode in inverted PerSCs.PNPDIN exhibits high conductivity and a good solubility in polar solvent,which results in an improved power conversion efficiency(PCE)from 10.05%(device without a CIL)to 16.97%.When the blend of PNPDIN and Bphen was used as a mixed CIL,the PCE of PerSCs can be further increased to 21.28%owing to the excellent morphology and matched energy level.More importantly,the PCE of the device is highly tolerant to the thickness of the mixed CIL,which benefited from the high conductivity of PNPDIN.This development is expected to provide an excellent mixed CIL material for roll-to-roll processing efficient and stable inverted PerSCs.

Enhancement of the efficiency and stability of planar p-i-n perovskite solar cells via incorporation of an amine-modified fullerene derivative as a cathode buffer layer

A methanol-soluble diamine-modified fullerene derivative(denoted as PCBDANI)was applied as an efficient cathode buffer layer(CBL)in planar p-i-n perovskite solar cells(pero-SCs)based on the CH_3NH_3PbI_(3-x)Cl_x absorber.The device with PCBDANI single CBL exhibited significantly improved performance with a power conversion efficiency(PCE)of 15.45%,which is approximately17%higher than that of the control device without the CBL.The dramatic improvement in PCE can be attributed to the formation of an interfacial dipole at the PCBM/Al interface originating from the amine functional group and the suppression of interfacial recombinationby the PCBDANI interlayer.To further improve the PCE of pero-SCs,PCBDANI/LiF double CBLs were introduced between PCBM and the top Al electrode.An impressive PCE of 15.71%was achieved,which is somewhat higher than that of the devices with LiF or PCBDANI single CBL.Besides the PCE,the long-term stability of the device with PCBDANI/LiF double CBLs is also superior to that of the device with LiF single CBL.

Cubic perovskite fluoride as open framework cathode for Na-ion batteries

Subject Code:E02With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.Li Chilin(李驰麟)from Shanghai Institute of Ceramics,Chinese Academy of Sciences reported that a cubic perovskite fluoride can serve as open framework cathode for high-rate

钙和铁共掺杂PrBaCo_(2)O_(5+δ)作为固体氧化物燃料电池阴极的研究

固体氧化物燃料电池(SOFC)作为一种高效的能量转化装置,具有广阔的应用前景。阴极的反应动力学和稳定性在SOFC中具有非常重要的意义。采用固相法合成了具有四方相的双钙钛矿结构的PrBa_(0.8)Ca_(0.2)Co_(1.5)Fe_(0.5)O_(5+δ)(PBCCF)。Ca离子和Fe离子的掺杂有效降低了PrBaCo_(2)O_(5+δ)的热膨胀系数。结构为PBCCF|GDC|SSZ|GDC|PBCCF的对称半电池在800℃时的极化阻抗为0.082Ω·cm^(2),表明PBCCF阴极在电化学反应过程中具有较高的催化活性。将PBCCF作为阴极丝网印刷在NiO-YSZ|YSZ|GDC结构的半电池(其中NiO-YSZ阳极支撑体和YSZ为电解质通过流延-叠层热压法制成,Gd_(0.2)Ce_(0.8)O_(1.9)(GDC)阻挡层通过丝网印刷法制成)上制备得到单电池,该电池在800℃时的功率密度可达1.0 W/cm^(2)。同时,单电池在60 h的短期稳定性测试中较为稳定。研究结果表明,PBCCF是一种非常有前景的SOFC阴极材料。

LaFeO_(3)基SOFC阴极改性的研究进展

作为固体氧化物燃料电池(SOFC)的重要组成部分,阴极性能的优劣影响电池的工作效率。钙钛矿型LaFeO_(3)基半导体材料具有特殊的电子-离子混合导电性质,是一种潜在的SOFC阴极材料。综述提高阴极材料性能的策略,按掺杂位置,介绍在LaFeO_(3)的A、B位单独掺杂和共掺杂时,采用的掺杂元素和掺杂量,并介绍纳米化、A位缺陷等修饰手段。分析改性对材料热膨胀系数、极化电阻、电化学效率和氧还原反应等性能的影响。

Mn离子掺杂Pr_(0.5)Ba_(0.5)Fe_(0.9)Mn_(0.1)O_(3-δ)钙钛矿SOEC阴极电解CO_(2)性能研究

固体氧化物电解池(SOEC)电解CO_(2)时其阴极是CO_(2)还原反应发生的场所,也是SOEC取得高性能的关键环节。研究了Mn离子掺杂的Pr_(0.5)Ba_(0.5)Fe_(0.9)Mn_(0.1)O_(3-δ)(PBFM)钙钛矿材料作为SOEC阴极电解纯CO_(2)的性能。结果表明在850℃、1.8 V的电解电压下基于PBFM阴极的SOEC电流密度可达1.7 A·cm^(-2),较使用未掺杂的Pr_(0.5)Ba_(0.5)FeO_(3-δ)(PBF)阴极提升了约30%;同时,电池的极化阻抗下降约60%,电化学性能增长主要来源于掺杂后氧空位浓度的增加。在800℃、1.3 V恒压的条件下70 h的长期测试中,PBFM电池没有表现出明显的衰减,且长期测试后的电极没有积碳现象。研究证明PBFM是一种有前景的电解CO_(2)SOEC阴极材料。