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.

Cationic ordering transition in oxygen-redox layered oxide cathodes

Understanding the structural origin of the competition between oxygen 2p and transition-metal 3d orbitals in oxygen-redox(OR)layered oxides is eminently desirable for exploring reversible and high-energy-density Li/Na-ion cathodes.Here,we reveal the correlation between cationic ordering transition and OR degradation in ribbon-ordered P3-Na_(0.6)Li_(0.2)Mn_(0.8)O_(2) via in situ structural analysis.Comparing two different voltage windows,the OR capacity can be improved approximately twofold when suppressing the in-plane cationic ordering transition.We find that the intralayer cationic migration is promoted by electrochemical reduction from Mn^(4+)to Jahn–Teller Mn^(3+)and the concomitant NaO_(6) stacking transformation from triangular prisms to octahedra,resulting in the loss of ribbon ordering and electrochemical decay.First-principles calculations reveal that Mn^(4+)/Mn^(3+)charge ordering and alignment of the degenerate eg orbital induce lattice-level collective Jahn–Teller distortion,which favors intralayer Mn-ion migration and thereby accelerates OR degradation.These findings unravel the relationship between in-plane cationic ordering and OR reversibility and highlight the importance of superstructure protection for the rational design of reversible OR-active layered oxide cathodes.

A 700 W·h·kg^(-1) Rechargeable Pouch Type Lithium Battery

High-energy-density rechargeable lithium batteries are being pursued by researchers because of their revolutionary potential nature.Current advanced practical lithium-ion batteries have an energy density of around300 W·h·kg^(-1).Continuing to increase the energy density of batteries to a higher level could lead to a major explosion development in some fields,such as electric aviation.Here,we have manufactured practical pouch-type rechargeable lithium batteries with both a gravimetric energy density of 711.3 W·h·kg^(-1)and a volumetric energy density of 1653.65 W·h·L^(-1).This is achieved through the use of high-performance battery materials including high-capacity lithium-rich manganese-based cathode and thin lithium metal anode with high specific energy,combined with extremely advanced process technologies such as high-loading electrode preparation and lean electrolyte injection.In this battery material system,the structural stability of cathode material in a widened charge/discharge voltage range and the deposition/dissolution behavior of interfacial modified thin lithium electrode are studied.

Achieving high initial Coulombic efficiency for competent Na storage by microstructure tailoring from chiral nematic nanocrystalline cellulose

Although it has been proven that porous,heteroatomic,and defective structures improve Na storage performance,they also severely affect the initial Coulombic efficiency(ICE)due to the huge irreversible capacity in the first cycle,which always limits the practical application of carbon anodes in commercial Na-ion batteries(NIBs).Here,we show the successful synthesis of nanocrystalline cellulose and the derivative hard carbons.A series of treatments including acid hydrolysis,hydrothermal carbonization,and hightemperature pyrolysis help tune the pores,heteroatoms,and defects to achieve an optimized balance between superior ICE and reversible capacity of up to 90.4%and 314 mAh g^(−1).This study highlights that tailoring the electrode microstructure could be an important strategy in the future design of carbonaceous anode materials for high-performance Na-ion batteries.

Understanding the battery safety improvement enabled by a quasi-solid-state battery design

The rapid development of lithium-ion batteries(LIBs)is faced with challenge of its safety bottleneck,calling for design and chemistry innovations.Among the proposed strategies,the development of solid-state batteries(SSBs)seems the most promising solution,but to date no practical SSB has been in large-scale application.Practical safety performance of SSBs is also challenged.In this article,a brief review on LIB safety issue is made and the safety short boards of LIBs are emphasized.A systematic safety design in quasi-SSB chemistry is proposed to conquer the intrinsic safety weak points of LIBs and the effects are accessed based on existing studies.It is believed that a systematic and targeted solution in SSB chemistry design can effectively improve the battery safety,promoting larger-scale application of LIBs.

Anomalous Josephson Effect in Topological Insulator-Based Josephson Trijunction

We studied anomalous Josephson effect(AJE) in Josephson trijunctions fabricated on Bi_(2)Se_(3), and found that the AJE in T-shaped trijunctions significantly alters the Majorana phase diagram of the trijunctions, when an in-plane magnetic field is applied parallel to two of the three single junctions. Such a phenomenon in topological insulator-based Josephson trijunction provides unambiguous evidence for the existence of AJE in the system, and may provide an additional knob for controlling the Majorana bound states in the Fu–Kane scheme of topological quantum computation.

Brightening thiocyanate-anion layered perovskite through internal stress modulated nano phase segregation

Thiocyanate-anion(SCN−)two-dimensional(2D)layered perovskite with internal stress-controlled nano phase segregation has been firstly demonstrated as a promising material system for luminescence applications.An interesting energy band structure is found as well as charge transfer process caused by nano phase segregation,which provide an alternative route to overcome the indirect-bandgap luminescence limit of SCN layered perovskites.It is revealed that,within the SCN layered framework,the segregated nano phases exist in a quantum well form,possessing much higher carrier localization and second-order radiative recombination abilities.With the help of internal stress modulation,these advantages can be significantly enhanced and finally contribute to high luminescence performances in visible-red regions.This work provides more potential opportunities for 2D layered perovskite materials in the future optoelectronic applications.

具有优异热稳定性和溶剂稳定性的快锂离子导体—锆基氧氯化物固态电解质

成本低廉的锂离子导体氯化物固态电解质Li_(2)ZrCl_(6),属于三方晶系,可在4.2 V下保持稳定,与高压正极材料具有良好的兼容性.然而,相对较低的室温离子电导率、较差的化学稳定性和热稳定性等缺点阻碍了它在全固态电池中的进一步发展.基于此,我们利用Li_(2)O,ZrCl_(4)和LiCl合成了新型氧氯化物固态电解质,并通过O^(2−)对Cl^(−)的取代来优化固态电解质的性能.结果表明增加Li_(2)O的含量会降低三方相Li_(2)ZrCl_(6)的结晶度,且诱导单斜结构的产生.新合成的Li_(2.22)Zr_(1.11)Cl_(5.33)O_(0.67)室温电导率可到10^(−3)S cm^(−1).此外,Li_(2)O的加入能够提高固态电解质的热稳定性和溶剂稳定性.固态电解质Li_(2.22)Zr_(1.11)Cl_(5.33)O_(0.67)良好的离子电导率及稳定性使得Li–In/LiCoO_(2)全固态电池具有稳定的循环性能.

Intrinsic effects of precursor functional groups on the Na storage performance in carbon anodes

The oxygen-containing functional groups in disordered carbon anodes have been widely reported to influence the Na storage performance.However,the effect of original oxygen-containing groups in the precursors on the final structures and electrochemical performance is rarely studied.Herein,we used the anthraquinone derivatives with different oxygen-containing functional groups as precursors to make the disordered carbon anodes for Na-ion batteries(NIBs).Through comprehensive structural and electrochemical analyses,we found that the different types of functional groups in carbon precursors directly affect the cross-linking process during carbonization.The original precursors containing enough inter-chain oxygen or oxygen-containing functional groups with unsaturated bonds unattached to the ring are beneficial for the oxygen atoms to remain or cross-link in structure to result in more C–O–C group,forming nanovoids and disordered structure,which then determine the high performance of the carbon anodes in NIBs.This work highlights the importance of the type/content of functional groups in precursor and provides guidance for the future design of carbon anodes in NIBs from the perspective of precursor selection.

The stability of inorganic perovskite solar cells:from materials to devices

Inorganic halide perovskite solar cells(IHPSCs)have become one of the most promising research hotspots due to to the excellent light and thermal stabilities of inorganic halide perovskites(IHPs).Despite rapid progress in cell performance in very recent years,the phase instability of IHPs easily occurs,which will remarkably influence the cell efficiency and stability.Much effort has been devoted to solving this issue.In this review,we focus on representative progress in the stability from IHPs to IHPSCs,including(i)a brief introduction of inorganic perovskite materials and devices,(ii)some new additives and fabrication methods,(iii)thermal and light stabilities,(iv)tailoring phase stability,(v)optimization of the stability of inorganic perovskite solar cells and(vi)interfacial engineering for stability enhancement.Finally,perspectives will be given regarding future work on highly efficient and stable IHPSCs.This review aims to provide a thorough understanding of the key influential factors on the stability of materials to highly efficient and stable IHPSCs.

Unlocking the multi-electron transfer reaction in NASICON-type cathode materials

The growing concern about scarcity and large-scale applications of lithium resources has attracted efforts to realize cost-effective phosphate-based cathode materials for next-generation Na-ion batteries(NIBs).In previous work,a series of materials(such as Na_(4)Fe_(3)(PO_(4))_(2)(P_(2)O_(7)),Na_(3)VCr(PO_(4))_(3),Na_(4)VMn(PO_(4))3,Na_(3)MnTi(PO_(4))_(3),Na_(3)MnZr(PO_(4))3,etc)with∼120 mAh g^(-1) specific capacity and high operating potential has been proposed.However,the mass ratio of the total transition metal in the above compounds is only∼22 wt%,which means that one-electron transfer for each transition metal shows a limited capacity(the mass ratio of Fe is 35.4 wt%in LiFePO_(4)).Therefore,a multi-electron transfer reaction is necessary to catch up to or go beyond the electrochemical performance of LiFePO_(4).This review summarizes the reported NASICON-type and other phosphate-based cathode materials.On the basis of the aforementioned experimental results,we pinpoint the multi-electron behavior of transition metals and shed light on designing rules for developing high-capacity cathodes in NIBs.

Boosting reversible anionic redox reaction with Li/Cu dual honeycomb centers

The anionic redox reaction(ARR)is a promising charge contributor to improve the reversible capacity of layeredoxide cathodes for Na-ion batteries;however,some practical bottlenecks still need to be eliminated,including a low capacity retention,large voltage hysteresis,and low rate capability.Herein,we proposed a high-Na content honeycomb-ordered cathode,P2–Na_(5/6)[Li_(1/6)Cu_(1/6)Mn_(2/3)]O_(2)(P2-NLCMO),with combined cationic/anionic redox.Neutron powder diffraction and X-ray diffraction of P2-NLCMO suggested P2-type stacking with rarely found P6322 symmetry.In addition,advanced spectroscopy techniques and density functional theory calculations confirmed the synergistic stabilizing relationship between the Li/Cu dual honeycomb centers,achieving fully active Cu^(3+)/Cu^(2+) redox and stabilized ARR with interactively suppressed local distortion.With a meticulously regulated charge/discharge protocol,both the cycling and rate capability of P2-NLCMO were significantly.