Difficulties, strategies, and recent research and development of layered sodium transition metal oxide cathode materials for high-energy sodium-ion batteries

Energy-storage systems and their production have attracted significant interest for practical applications.Batteries are the foundation of sustainable energy sources for electric vehicles(EVs),portable electronic devices(PEDs),etc.In recent decades,Lithium-ion batteries(LIBs) have been extensively utilized in largescale energy storage devices owing to their long cycle life and high energy density.However,the high cost and limited availability of Li are the two main obstacles for LIBs.In this regard,sodium-ion batteries(SIBs) are attractive alternatives to LIBs for large-scale energy storage systems because of the abundance and low cost of sodium materials.Cathode is one of the most important components in the battery,which limits cost and performance of a battery.Among the classified cathode structures,layered structure materials have attracted attention because of their high ionic conductivity,fast diffusion rate,and high specific capacity.Here,we present a comprehensive review of the classification of layered structures and the preparation of layered materials.Furthermore,the review article discusses extensively about the issues of the layered materials,namely(1) electrochemical degradation,(2) irreversible structural changes,and(3) structural instability,and also it provides strategies to overcome the issues such as elemental phase composition,a small amount of elemental doping,structural design,and surface alteration for emerging SIBs.In addition,the article discusses about the recent research development on layered unary,binary,ternary,quaternary,quinary,and senary-based O3-and P2-type cathode materials for high-energy SIBs.This review article provides useful information for the development of high-energy layered sodium transition metal oxide P2 and O3-cathode materials for practical SIBs.

Designing ultrastable P2/O3-type layered oxides for sodium ion batteries by regulating Na distribution and oxygen redox chemistry

P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.

Inhibiting Voltage Decay in Li-Rich Layered Oxide Cathode:From O3-Type to O2-Type Structural Design

Li-rich layered oxide(LRLO)cathodes have been regarded as promising candidates for next-generation Li-ion batteries due to their exceptionally high energy density,which combines cationic and anionic redox activities.However,continuous voltage decay during cycling remains the primary obstacle for practical applications,which has yet to be fundamentally addressed.It is widely acknowledged that voltage decay originates from the irreversible migration of transition metal ions,which usually further exacerbates structural evolution and aggravates the irreversible oxygen redox reactions.Recently,constructing O2-type structure has been considered one of the most promising approaches for inhibiting voltage decay.In this review,the relationship between voltage decay and structural evolution is systematically elucidated.Strategies to suppress voltage decay are systematically summarized.Additionally,the design of O2-type structure and the corresponding mechanism of suppressing voltage decay are comprehensively discussed.Unfortunately,the reported O2-type LRLO cathodes still exhibit partially disordered structure with extended cycles.Herein,the factors that may cause the irreversible transition metal migrations in O2-type LRLO materials are also explored,while the perspectives and challenges for designing high-performance O2-type LRLO cathodes without voltage decay are proposed.

Ca_(2)MnO_(4)-layered perovskite modified by NaNO_(3)for chemical-looping oxidative dehydrogenation of ethane to ethylene

Chemical-looping oxidative dehydrogenation(CL-ODH)is a process designed for the conversion of alkanes into olefins through cyclic redox reactions,eliminating the need for gaseous O_(2).In this work,we investigated the use of Ca_(2)MnO_(4)-layered perovskites modified with NaNO_(3) dopants,serving as redox catalysts(also known as oxygen carriers),for the CL-ODH of ethane within a temperature range of 700-780℃.Our findings revealed that the incorporation of NaNO_(3) as a modifier significantly-nhanced the selectivity for-thylene generation from Ca_(2)MnO_(4).At 750℃and a gas hourly space velocity of 1300 h^(-1),we achieved an-thane conversion up to 68.17%,accompanied by a corresponding-thylene yield of 57.39%.X-ray photoelectron spectroscopy analysis unveiled that the doping NaNO_(3) onto Ca_(2)MnO_(4) not only played a role in reducing the oxidation state of Mn ions but also increased the lattice oxygen content of the redox catalyst.Furthermore,formation of NaNO_(3) shell on the surface of Ca_(2)MnO_(4) led to a reduction in the concentration of manganese sites and modulated the oxygen-releasing behavior in a step-wise manner.This modulation contributed significantly to the enhanced selectivity for ethylene of the NaNO_(3)-doped Ca_(2)MnO_(4) catalyst.These findings provide compelling evidence for the potential of Ca_(2)MnO_(4)-layered perovskites as promising redox catalysts in the context of CL-ODH reactions.

空气条件下高温固相合成层状LiMnO_2及其离子交换的影响规律

在空气中高温固相反应合成了层状单斜结构前驱体 Na Mn O2 ,在不同条件下进行离子交换反应 ,得到Li Mn O2 .用 X射线衍射法表征了前驱体及交换产物的晶体结构 ,用电感耦合等离子体光谱进行元素含量分析 ,用扫描电镜测定晶体的形貌 .结果表明 ,离子交换反应条件对反应速率和产物的晶体结构与组成有重要影响 .

非层状二维γ-In_(2)Se_(3)的各向异性生长及其光学特性

非层状二维(2D)γ-In_(2)Se_(3)具有优异的光学和电学性能,在超薄柔性器件和光电探测领域具有广泛的应用前景.然而,相较于层状的类石墨烯材料,非层状材料固有的各向同性化学键,使得其二维各向异性生长面临较大的挑战.本研究构建了一种新的化学气相沉积(CVD)生长策略,成功制备了高质量的2Dγ-In_(2)Se_(3).首次选用低熔点的铟粉为前驱体,有效降低了生长温度.此外,生长过程去除了CVD法合成二维硒化物时不可避免的危险气体H_(2),这不仅能有效抑制InSe副产物的形成,还降低了实验危险性.通过探究原料用量、生长温度及时间等参数对样品形貌和厚度的影响,获得了最佳生长窗口.详细表征了2Dγ-In_(2)Se_(3)的微观形貌、化学组分、晶体结构和光学特性等.结果表明,样品具有强烈的光致发光(PL)效应,与γ-In_(2)Se_(3)的直接带隙属性相吻合.随着厚度的减小,PL峰会发生蓝移,说明光学带隙随之增大.Raman光谱显示,不同厚度的样品其特征峰也会发生移动,说明厚度会影响2Dγ-In_(2)Se_(3)的分子振动行为.由此可见,通过生长参数调控2Dγ-In_(2)Se_(3)的厚度,可实现对其光学带隙和分子振动行为的调控,这将为相关的理论研究和光电器件应用提供基本的材料平台.

Current Status in Layered Ternary Carbide Ti_3SiC_2,a Review

This article provides a review of current research activities that concentrate on Ti3SiC2. We begin with an overview of the crystal and electronic structures, which are the basis to understand this material. Followings are the synthetic strategies that have been exploited to achieve, and the formation mechanism of Ti3SiC2. Then we devote much attentions to the mechanical properties and oxidation/hot corrosion behaviors of Ti3SiC2 as well as some advances achieved recently. At the end of this paper, we elaborate on some new discoveries in the Ti3SiC2 system, and also give a brief discussion focused on the ＂microstructure -property＂ relationship.

Single-phase P2-type layered oxide with Cu-substitution for sodium ion batteries

The development of high-performance layered oxide cathodes for sodium ion batteries (SIBs) continues to facing be hindered by severe challenges to date.Herein,a single-phase P2-Na0.67Mn0.6Ni0.2Co0.1Cu0.1O2(NMNCC) comprising multiple-layer-oriented stacked nanoflakes is designed and synthesized via a simple sol-gel method.The large lattice parameters ensure a large three-dimensional frame,which enables the diffusion of sodium ions.Owing to its optimal morphology structure modulation transition metal substitution strategy,the MNCC electrode delivers a reversible capacity of 131.3 mAh g^-1 at 0.1 C with retention of 86.7%after 200 cycles.In addition,it provides an initial capacity of 86.7 mAh g^-1,and a retention of 80.0%after 500 cycles even at a current density of up to 1 A g^-1.The stable single-phase structure and slight volume shrinkage observed after Na+extraction further delay structural degradation.High Na+mobility and low Na+diffusion resistance are also guarantee the excellent rate performance of the NMNCC electrode.Thus,we determine that the NMNCC cathode is significant in the advancement of promising novel layered oxide cathodes.

Highly efficient visible-light photocatalytic H2 evolution over 2D–2D Cd S/Cu7S4 layered heterojunctions

Converting solar energy into clean and sustainable chemical fuels is a promising strategy for exploiting renewable energy.The application of photocatalytic water splitting technology in hydrogen production is important for sustainable energy development and environmental protection.In this study,for the first time,2D Cu7S4 co-catalysts were coupled on the surface of a CdS nanosheet photocatalyst by a one-step ultrasonic-assisted electrostatic self-assembly method at room temperature.The as-fabricated 2D^-2D CdS/Cu7S4 layered heterojunctions were demonstrated to be advanced composite photocatalysts that enhance the water splitting efficiency toward hydrogen production.The highest hydrogen evolution rate of the 2D^-2D CdS/2%Cu7S4 binary heterojunction photocatalyst was up to 27.8 mmol g^-1 h^-1 under visible light irradiation,with an apparent quantum efficiency of 14.7%at 420 nm,which was almost 10.69 times and 2.65 times higher than those of pure CdS nanosheets(2.6 mmol g^-1 h^-1)and CdS-2%CuS(10.5 mmol g^-1 h^-1),respectively.The establishment of the CdS/Cu7S4 binary-layered heterojunction could not only enhance the separation of photogenerated electron-hole(e--h+)pairs,improve the transfer of photo-excited electrons,and prolong the life-span of photo-generated electrons,but also enhance the light absorption and hydrogen-evolution kinetics.All these factors are important for the enhancement of the photocatalytic activity.Expectedly,the 2D^-2D interface coupling strategy based on CdS NSs can be extensively exploited to improve the hydrogen-evolution activity over various kinds of conventional semiconductor NSs.

Tuning the selectivity of photoreduction of CO2 to syngas over Pd/layered double hydroxide nanosheets under visible light up to 600 nm

Photocatalytic reduction of CO2 with H2 O to syngas is an effective way for producing high value-added chemical feedstocks such as methanol and light olefins in industry.Nevertheless,the precise control of CO/H2 ratio from photocatalytic CO2 reduction reaction still poses a great challenge for the further application.Herein,we prepared a series of highly efficient heterostructure based on highly dispersed palladium supported on ultrathin Co Al-layered double hydroxide(LDH).In conjunction with a Ru-complex sensitizer,the molar ratios of CO/H2 can be tuned from 1:0.74 to 1:3 under visible-light irradiation(λ>400 nm).More interestingly,the syngas can be obtained under light irradiation atλ>600 nm.Structure characterization and density functional theory calculations revealed that the remarkable catalytic activity can be due to the supported palladium,which improved the charge transfer efficiency.Meanwhile,more H atoms were used to generate H2 on the supported palladium for further tunable CO/H2 ratio.This work demonstrates a new strategy for harnessing abundant solar-energy to produce syngas from a CO2 feedstock.

Integration of 2D layered CdS/WO_(3) S-scheme heterojunctions and metallic Ti_(3)C_(2) MXene-based Ohmic junctions for effective photocatalytic H_(2) generation

The rapid recombination of photo-generated electron-hole pairs,insufficient active sites,and strong photocorrosion have considerably restricted the practical application of Cd S in photocatalytic fields.Herein,we designed and constructed a 2D/2D/2D layered heterojunction photocatalyst with cascaded 2D coupling interfaces.Experiments using electron spin resonance spectroscopy,ultraviolet photoelectron spectroscopy,and in-situ irradiation X-ray photoelectron spectroscopy were conducted to confirm the 2D layered CdS/WO_(3) step-scheme(S-scheme)heterojunctions and CdS/MX ohmic junctions.Impressively,it was found that the strong interfacial electric fields in the S-scheme heterojunction photocatalysts could effectively promote spatially directional charge separation and transport between CdS and WO_(3) nanosheets.In addition,2D Ti_(3)C_(2) MXene nanosheets with a smaller work function and excellent metal conductivity when used as a co-catalyst could build ohmic junctions with Cd S nanosheets,thus providing a greater number of electron transfer pathways and hydrogen evolution sites.Results showed that the highest visible-light hydrogen evolution rate of the optimized MX-Cd S/WO_(3) layered multi-heterostructures could reach as high as 27.5 mmol/g/h,which was 11.0 times higher than that of pure CdS nanosheets.Notably,the apparent quantum efficiency reached 12.0% at 450 nm.It is hoped that this study offers a reliable approach for developing multifunctional photocatalysts by integrating S-scheme and ohmic-junction built-in electric fields and rationally designing a 2D/2D interface for efficient light-to-hydrogen fuel production.

2D materials modulating layered double hydroxides for electrocatalytic water splitting

Exploring highly efficient electrochemical water splitting catalysts has recently attracted extensive research interest from both fundamental researches and practical applications.Transition metal‐based layered double hydroxides(LDHs)have been proved to be one of the most efficient materials for oxygen evolution reaction(OER),however,still suffered from low conductivity and sluggish kinetics for hydrogen evolution reaction(HER),which largely inhibited the overall water splitting efficiency.To address this dilemma,enormous approaches including doping regulation,intercalation tuning and defect engineering are therefore rationally designed and developed.Herein,we focus on the recent exciting progress of LDHs hybridization with other two‐dimensional(2D)materials for water splitting reactions,not barely for enhancing OER efficiency but also for boosting HER activity.Particularly,the structural features,morphologies,charge transfer and synergistic effects for the heterostructure/heterointerface that influence the electrocatalytic performance are discussed in details.The hybrid 2D building blocks not only serve as additional conductivity and structural supported but also promote electron transfer at the interfaces and further enhance the electrocatalytic performance.The construction and application of the nanohybrid materials will guide a new direction in developing multifunctional materials based on LDHs,which will contribute to energy conversion and storage.

Layered double hydroxide photocatalysts for solar fuel production

Splitting water or reducing CO_(2) via semiconductor photocatalysis to produce H2 or hydrocarbon fuels through the direct utilization of solar energy is a promising approach to mitigating the current fossil fuel energy crisis and environmental challenges.It enables not only the realization of clean,renewable,and high-heating-value solar fuels,but also the reduction of CO_(2) emissions.Layered double hydroxides(LDHs)are a type of two-dimensional anionic clay with a brucite-like structure,and are characterized by a unique,delaminable,multidimensional,layered structure;tunable intralayer metal cations;and exchangeable interlayer guest anions.Therefore,it has been widely investigated in the fields of CO_(2) reduction,photoelectrocatalytic water oxidation,and water photolysis to produce H2.However,the low carrier mobility and poor quantum efficiency of pure LDH limit its application.An increasing number of scholars are exploring methods to obtain LDH-based photocatalysts with high energy conversion efficiency,such as assembling photoactive components into LDH laminates,designing multidimensional structures,or coupling different types of semiconductors to construct heterojunctions.This review first summarizes the main characteristics of LDH,i.e.,metal-cation tunability,intercalated guest-anion substitutability,thermal decomposability,memory effect,multidimensionality,and delaminability.Second,LDHs,LDH-based composites(metal sulfide-LDH composites,metal oxide-LDH composites,graphite phase carbon nitride-LDH composites),ternary LDH-based composites,and mixed-metal oxides for splitting water to produce H_(2) are reviewed.Third,graphite phase carbon nitride-LDH composites,MgAl-LDH composites,CuZn-LDH composites,and other semiconductor-LDH composites for CO_(2) reduction are introduced.Although the field of LDH-based photocatalysts has advanced considerably,the photocatalytic mechanism of LDHs has not been thoroughly elucidated;moreover,the photocatalytic active sites,the synergy between different components,and the interfacial reaction mechanism of LDH-based photocatalysts require further investigation.Therefore,LDH composite materials for photocatalysis could be developed through structural regulation and function-oriented design to investigate the effects of different components and interface reactions,the influence of photogenerated carriers,and the impact of material composition on the physical and chemical properties of the LDH-based photocatalyst.

Synthesis and Performance of LiMnO_2 as Cathodes for Li-ion Batteries

Two structure types of LiMnO 2 were synthesized by sol gel method and ion exchange method respectively.The results indicate that orthorhombic phase LiMnO 2 is more stable than layered LiMnO 2,o LiMnO 2 can be synthesized directly by sol gel methods followed by heat treated in argon,but layered LiMnO 2 was obtained only by indirect methods such as ion exchange method.In this paper,we first synthesized layered NaMnO 2 by the sol gel method,and then obtained layered LiMnO 2 by the ion exchange method.The phase constitution,chemical composition,and images of the products were tested by XRD,AAS (atomic absorption spectroscopy) and SEM.The electrochemical performances of the two structural types of LiMnO 2 are obviously different during the initial few cycles,but later they both have a good capacity retaining ability.The capacity of layered structure LiMnO 2 is higher than that of o LiMnO 2.

Advances in efficient electrocatalysts based on layered double hydroxides and their derivatives

The explore and development of electrocatalysts have gained significant attention due to their indispensable status in energy storage and conversion systems, such as fuel cells, metal–air batteries and solar water splitting cells. Layered double hydroxides（LDHs） and their derivatives（e.g., transition metal alloys, oxides, sulfides, nitrides and phosphides） have been adopted as catalysts for various electrochemical reactions, such as oxygen reduction, oxygen evolution, hydrogen evolution, and COreduction, which show excellent activity and remarkable durability in electrocatalytic process. In this review, the synthesis strategies, structural characters and electrochemical performances for the LDHs and their derivatives are described. In addition, we also discussed the effect of electronic and geometry structures to their electrocatalytic activity. The further development of high-performance electrocatalysts based on LDHs and their derivatives is covered by both a short summary and future outlook from the viewpoint of the material design and practical application.

Layered Foam/Film Polymer Nanocomposites with Highly Efficient EMI Shielding Properties and Ultralow Reflection

Lightweight,high-efficiency and low reflection electromagnetic interference(EMI)shielding polymer composites are greatly desired for addressing the challenge of ever-increasing electromagnetic pollution.Lightweight layered foam/film PVDF nanocomposites with efficient EMI shielding effectiveness and ultralow reflection power were fabricated by physical foaming.The unique layered foam/film structure was composed of PVDF/SiCnw/MXene(Ti_(3)C_(2)Tx)composite foam as absorption layer and highly conductive PVDF/MWCNT/GnPs composite film as a reflection layer.The foam layer with numerous heterogeneous interfaces developed between the SiC nanowires(SiCnw)and 2D MXene nanosheets imparted superior EM wave attenuation capability.Furthermore,the microcellular structure effectively tuned the impedance matching and prolonged the wave propagating path by internal scattering and multiple reflections.Meanwhile,the highly conductive PVDF/MWCNT/GnPs composite(~220 S m^(−1))exhibited superior reflectivity(R)of 0.95.The tailored structure in the layered foam/film PVDF nanocomposite exhibited an EMI SE of 32.6 dB and a low reflection bandwidth of 4 GHz(R<0.1)over the Kuband(12.4-18.0 GHz)at a thickness of 1.95 mm.A peak SER of 3.1×10^(-4) dB was obtained which corresponds to only 0.0022% reflection efficiency.In consequence,this study introduces a feasible approach to develop lightweight,high-efficiency EMI shielding materials with ultralow reflection for emerging applications.

Structured NiFe catalysts derived from in-situ grown layered double hydroxides on ceramic monolith for CO_(2) methanation

Monolithic catalysts for CO_(2) methanation have become an active research area for the industrial development of Power-to-Gas technology.In this study,we developed a facile and reproducible synthesis strategy for the preparation of structured NiFe catalysts on washcoated cordierite monoliths for CO_(2) methanation.The NiFe catalysts were derived from in-situ grown layered double hydroxides(LDHs)via urea hydrolysis.The influence of different washcoat materials,i.e.,alumina and silica colloidal suspensions on the formation of LDHs layer was investigated,together with the impact of total metal concentration.NiFe LDHs were precipitated on the exterior surface of cordierite washcoated with alumina,while it was found to deposit further inside the channel wall of monolith washcoated with silica due to different intrinsic properties of the colloidal solutions.On the other hand,the thickness of in-situ grown LDHs layers and the catalyst loading could be increased by high metal concentration.The best monolithic catalyst(COR-AluCC-0.5M)was robust,having a thin and well-adhered catalytic layer on the cordierite substrate.As a result,high methane yield was obtained from CO_(2) methanation at high flow rate on this structured NiFe catalysts.The monolithic catalysts appeared as promising structured catalysts for the development of industrial methanation reactor.

Chemical Modifications of Layered Double Hydroxides in the Supercapacitor

Layered double hydroxides are one class or kind of 2 D layered materials that are considered promising for use in the supercapacitor.Although there have been many studies on the structure,composition,properties,and electrode fabrication of layered double hydroxides,none summarize the effects of various modification methods on the structure and performance of layered double hydroxides in the supercapacitor.In a bid to fill this gap,in this review,we summarize the progress of modification methods such as exfoliation,intercalation,vacancy,doping,phase transformation,and composition regulation of layered double hydroxides in the field of the supercapacitor and put forward some opinions regarding the progress of research on the methods used in modifying the layered double hydroxides.

Room temperature synthesis of two-dimensional multi layer magnets based on α-Co^(Ⅱ) layered hydroxides

Research on two-dimensional(2D) materials is one of the most active fields in materials science and nanotechnology. Among the members of the 2D family, layered hydroxides(LHs) represent an exceptional case of study due to their unparalleled chemical versatility which allows the modulation of their physicochemical properties at will. Nowadays, LHs based on earth-abundant metals are key materials in the areas of energy storage and conversion, hybrid materials or magnetism. α-Co hydroxides(Simonkolleite-like structures) are promising phases with tuneable electronic and magnetic properties by ligand modification. However, even in the simple case of α-Co^(Ⅱ) hydroxychlorides, the preparation of well-defined large 2D crystals is not straightforward, hindering the development of fundamental studies. Herein, we present the synthesis of 2D hexagonal crystals with outstanding sizethickness relationship(diameter > 5 μm and thickness of 20 ± 7 nm) by a simple homogeneous synthesis taking place at room temperature. In structural terms, no differences are observed between our layered materials and those obtained hydrothermally. However, dynamic susceptibility measurements alert about different arrangements of the magnetic sublattices, which have been rationalized with structural DFT calculations. This work provides an extremely easy bottom-up method to obtain high-quality 2D crystals based on α-CoIIhydroxides,paving the way for the development of fundamental studies and applications.

In sight of K-deficient layered K_(x)MnO_(2) cathode for potassium-ions batteries

Potassium-ions batteries(PIBs)are attracting increasing attention as up-and-coming youngster in largescale grid-level energy storage benefiting from its low-cost and high energy density.Nevertheless,enough researches regarding indispensable cathode materials for PIBs are badly absent.Herein,we synthesize K-deficient layered manganese-based oxides(P2-K_(0.21)MnO_(2) and P3-K_(0.23)MnO_(2))and investigate them as cathode of PIBs for the first time.As the newcomer of potassium-containing layered manganese-based oxides(K_(x)MnO_(2))group,P2-K_(0.21)MnO_(2) delivers high discharge capacity of 99.3 mAh g^(-1) and P3-K_(0.23)MnO_(2) exhibits remarkable capacity retention rate of 75.5%.Besides,in-situ XRD and ex-situ XRD measurements reveal the reversible phase transition of P2-K_(0.21)MnO_(2) and P3-K_(0.23)MnO_(2) with the potassium-ions extraction and reinsertion,respectively.This work contributes to a better understanding for the potassium storage in K-deficient layered K_(x)MnO_(2)(x≤0.23),possessing an important basic scientific significance for the exploitation and application of layered K_(x)MnO_(2) in PIBs.