Suppress oxygen evolution of lithium-rich manganese-based cathode materials via an integrated strategy

Improving the reversibility of anionic redox and inhibiting irreversible oxygen evolution are the main challenges in the application of high reversible capacity Li-rich Mn-based cathode materials.A facile synchronous lithiation strategy combining the advantages of yttrium doping and LiYO_(2) surface coating is proposed.Yttrium doping effectively suppresses the oxygen evolution during the delithiation process by increasing the energy barrier of oxygen evolution reaction through strong Y–O bond energy.LiYO_(2) nanocoating has the function of structural constraint and protection,that protecting the lattice oxygen exposed to the surface,thus avoiding irreversible oxidation.As an Li^(+) conductor,LiYO_(2) nano-coating can provide a fast Li^(+) transfer channel,which enables the sample to have excellent rate performance.The synergistic effect of Y doping and nano-LiYO_(2) coating integration suppresses the oxygen release from the surface,accelerates the diffusion of Li^(+)from electrolyte to electrode and decreases the interfacial side reactions,enabling the lithium ion batteries to obtain good electrochemical performance.The lithium-ion full cell employing the Y-1 sample(cathode)and commercial graphite(anode)exhibit an excellent specific energy density of 442.9 Wh kg^(-1) at a current density of 0.1C,with very stable safety performance,which can be used in a wide temperature range(60 to-15℃)stable operation.This result illustrates a new integration strategy for advanced cathode materials to achieve high specific energy density.

Recent advances and perspectives on vanadium-and manganese-based cathode materials for aqueous zinc ion batteries

The growing demand for energy storage has inspired researchers’exploration of advanced batteries.Aqueous zinc ion batteries(ZIBs)are promising secondary chemical battery system that can be selected and pursued.Rechargeable ZIBs possess merits of high security,low cost,environmental friendliness,and competitive performance,and they are received a lot of attention.However,the development of suitable zinc ion intercalation-type cathode materials is still a big challenge,resulting in failing to meet the commercial needs of ZIBs.Both vanadium-based and manganese-based compounds are representative of the most advanced and most widely used rechargeable ZIBs electrodes.The valence state of vanadium is+2~+5,which can realize multi-electron transfer in the redox reaction and has a high specific capacity.Most of the manganese-based compounds have tunnel structure or three-dimensional space frame,with enough space to accommodate zinc ions.In order to understand the energy storage mechanism and electrochemical performance of these two materials,a specialized review focusing on state-of-the-art developments is needed.This review offers access for researchers to keep abreast of the research progress of cathode materials for ZIBs.The latest advanced researches in vanadium-based and manganese-based cathode materials applied in aqueous ZIBs are highlighted.This article will provide useful guidance for future studies on cathode materials and aqueous ZIBs.

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.

Synthesis and characterization of Na0.44MnO2 nanorods/graphene composite as cathode materials for sodium-ion batteries

Na0.44MnO2 nanorods have been prepared by a hydrothermal method.The experimental parameters have been systematically investigated and optimized.The results show that Na0.44MnO2 nanorods obtained via the hydrothermal treatment at 200℃for 16 h show the best electrochemical properties,which deliver the high initial discharge capacity of 110.7 mA·h/g at 50 mA/g in potential window 2.0-4.0 V.To further improve their electrochemical properties,a ball milling process with graphene has been carried out to obtain Na0.44MnO2/graphene composite.The initial discharge capacity of Na0.44MnO2/graphene composite is 106.9 mA·h/g at a current density of 50 mA/g.After 100 cycles,the residual discharge capacity is 91.8 mA·h/g and the capacity retention rate is 85.9%,which is much higher than that of pristine Na0.44MnO2 nanorods(74.7%)at the same condition.What is more,when the current density reaches 500 and 1000 mA/g,the corresponding discharge capacities of Na0.44MnO2/graphene composite are about 89 and 78 mA·h/g,respectively,indicating outstanding rate capability.

Mitigated lattice distortion and oxygen loss of Li-rich layered cathode materials through anion/cation regulation by Ti^(4+)-substitution

Lithium-rich layered cathode material(LLM)can meet the requirement of power lithium-ion energy storage devices due to the great energy density.However,the de/intercalation of Li+will cause the irreversible loss of lattice oxygen and trigger transition metal(TM)ions migrate to Li+vacancies,resulting in capacity decay.Here we brought Ti4+in substitution of TM ions in Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2),which could stabilize structure and expand the layer spacing of LLM.Moreover,optimized Ti-substitution can regulate the anions and cations of LLM,enhance the interaction with lattice oxygen,increase Ni^(3+) and Co^(3+),and improve Mn^(4+) coordination,improving reversibility of oxygen redox activation,maintaining the stable framework and facilitating the Li^(+) diffusion.Furthermore,we found 5%Ti-substitution sample delivered a high discharge capacity of 244.2 mAh/g at 50 mA/g,an improved cycling stability to 87.3%after 100 cycles and enhanced rate performance.Thereby Ti-substitution gives a new pathway to achieve high reversible cycle retention for LLMs.

Restraining migration and dissolution of transition-metal-ions via functionalized separator for Li-rich Mn-based cathode with high-energy-density

Lithium-rich manganese-based materials(LRMs) are promising cathode for high-energy-density lithiumion batteries due to their high capacity,low toxicity,and low cost.However,LRMs suffer from serious voltage decay and capacity fade due to continual migration and dissolution of transition metal ions(TMs) during cycling process.Herein,a novel strategy is proposed to inhibit the TMs migration of LRMs through a modified separator by means of functionalized carbon coating layer,which depends on the chemical constraint of the abundant functional groups in the modified super P.In addition,it has been found that the dissolution of TMs can be restrained based on the Le Chatelier's principle.Moreover,the modified separator owns good wettability toward the electrolyte.As a result,the LRMs cathode with the modified separator delivers a high discharge capacity of 329.93 mA h g-1 at 0.1 C,and achieves good cyclic performance,the enhanced reaction kinetics and low voltage decay.Therefore,this work provides a new idea to promote the comprehensive electrochemical performances of Li-ion batteries with LRMs cathode through a strategy of separator modification.

Dual-modification of manganese oxide by heterostructure and cation pre-intercalation for high-rate and stable zinc-ion storage

Zinc-ion batteries(ZIBs)possess great advantages in terms of high safety and low cost,and are regarded as promising alternatives to lithium-ion batteries(LIBs).However,limited by the electrochemical kinetics and structural stability of the typical cathode materials,it is still difficult to simultaneously achieve high rates and high cycling stability for ZIBs.Herein,we present a manganese oxide(Sn_(x)Mn O_(2)/Sn O_(2))material that is dual-modified by Sn O_(2)/Mn O_(2)heterostructures and pre-intercalated Sn;cations as the cathode material for ZIBs.Such modification provides sufficient hetero-interfaces and expanded interlayer spacing in the material,which greatly facilitates the insertion/extraction of Zn^(2+).Meanwhile,the“structural pillars”of Sn^(4+) cations and the“pinning effect”of SnO_(2)also structurally stabilizes the Mn O_(2)species during the repeated Zn^(2+) insertion/extraction,leading to ultra-high cycling stability.Due to these merits,the Sn_(x)MnO_(2)/SnO_(2)cathode exhibits a high reversible capacity of 316.1 m Ah g^(-1) at 0.3 A g^(-1),superior rate capability of 179.4 m Ah g^(-1) at 2 A g^(-1),and 92.4%capacity retention after 2000 cycles.Consequently,this work would provide a promising yet efficient strategy by combining heterostructures and cations preintercalation to obtain high-performance cathodes for ZIBs.

Improving the structural materials via reservation Li-ion batteries stability of Li-rich cathode of cations in the Li-slab for

High-capacity Li-rich cathode materials can significantly improve the energy density of lithium-ion batteries, which is the key limitation to miniaturization of electronic devices and further improvement of electrical-vehicle mileage. However, severe voltage decay hinders the further commercialization of these materials. Insights into the relationship between the inherent structural stability and external appearance of the voltage decay in high-energy Li-rich cathode materials are critical to solve this problem. Here, we demonstrate that structural evolution can be significantly inhibited by the intentional introduction of certain adventive cations （such as Ni2~） or by premeditated reservation of some of the original Li~ ions in the Li slab in the delithiated state. The voltage decay of Li-rich cathode materials over 100 cycles decreased from 500 to 90 or 40 mV upon introducing Ni2~ or retaining some Li~ ions in the Li slab, respectively. The cations in the Li slab can serve as stabilizers to reduce the repulsion between the two neighboring oxygen layers, leading to improved thermodynamic stability. Meanwhile, the cations also suppress transition metal ion migration into the Li slab, thereby inhibiting structural evolution and mitigating voltage decay. These findings provide insights into the origin of voltage decay in Li-rich cathode materials and set new guidelines for designing these materials for high-energy-density Li-ion batteries.

Characterization of Li-rich layered oxides by using transmission electron microscope

Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs further understanding of the structural complexity and dynamic evolution of monoclinic and rhombohedral phases, in order to overcome the issues including voltage decay, poor rate capability, initial irreversible capacity loss and etc. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, have fueled rapid progress in the understanding of the mechanism of such issues. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, migration of transition metal, and the activation of oxygen of LrLOs are then explored in detail, with a particular focus on the mechanism of voltage decay.

Hydrated ammonium manganese phosphates by electrochemically induced manganese-defect as cathode material for aqueous zinc ion batteries

Aqueous zinc ion batteries(AZIBs) with the merits of low cost, low toxicity, high safety, environmental benignity as well as multi-valence properties as the large-scale energy storage devices demonstrate tremendous application prospect. However, the explorations for the most competitive manganese-based cathode materials of AZIBs have been mainly limited to some known manganese oxides. Herein, we report a new type of cathode material NH_(4)MnPO_(4)·H_(2)O(abbreviated as AMPH) for rechargeable AZIBs synthesized through a simple hydrothermal method. An in-situ electrochemical strategy inducing Mn-defect has been used to unlock the electrochemical activity of AMPH through the initial charge process, which can convert poor electrochemical characteristic of AMPH towards Zn^(2+)and NH_(4)+into great electrochemically active cathode for AZIBs. It still delivers a reversible discharge capacity up to 90.0 m Ah/g at 0.5 A/g even after 1000thcycles, which indicates a considerable capacity and an impressive cycle stability. Furthermore, this cathode reveals an(de)insertion mechanism of Zn^(2+)and NH_(4)+without structural collapse during the charge/discharge process. The work not only supplements a new member for the family of manganese-based compound for AZIBs, but also provides a potential direction for developing novel cathode material for AZIBs by introducing defect chemistry.

Controllable construction of La_(2)Li_(0.5)Co_(0.5)O_(4)multifunctional“armor”to stabilize Li-rich layered oxide cathode for highperformance lithium-ion batteries

Lithium-rich manganese-based cathodes(LR)are valuable cathode materials for the next generation of lithium-ion batteries(LIBs)with high-energy density.However,the fast voltage/capacity decay on cycling is the major obstacle for the practical application induced by the less-than-ideal anionic redox reactions and structure distortion.Herein,in order to tackle these challenges,a perovskite-like La_(2)Li_(0.5)Co_(0.5)O_(4)(LLCO)material is selected as protective surface to stabilize the Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2)(LR)substrate through wet chemical coating method.Versatile structure/phase characterizations and electrochemical tests exhibit that the LLCO can not only minish the oxygen evolution and enhance the structure stability,but also restrain the electrolyte corrosion and increase the mechanical strength of cathode materials.Moreover,the coated LLCO with high electronic/ionic conductivity dramatically accelerates the energy storage kinetic,thereby displaying the improved rate performance.Specifically,the optimized LR@LLCO sample(1LLCO)exhibits a high capacity of 250.6 mAh·g^(-1)after 100 cycles at 0.1 C and excellent capacity retention of 82.6%after 200 cycles at 2 C.This work provides a new idea for the modification of LR cathodes toward commercial high-performance LIBs.

High capacity lithium-manganese-nickel-oxide composite cathodes with low irreversible capacity loss and good cycle life for lithium ion batteries

We report a method to eliminate the irreversible capacity of 0.4Li_2MnO_3·0.6LiNi_(0.5)Mn_(0.5)O_2(Li_(1.17)Ni_(0.25)Mn_(0.583)O_2) by decreasing lithium content to yield integrated layered-spinel structures.XRD patterns,High-resolution TEM image and electrochemical cycling of the materials in lithium cells revealed features consistent with the presence of spinel phase within the materials.When discharged to about 2.8 V,the spinel phase of LiM_2O_4(M=Ni,Mn) can transform to rock-salt phase of Li_2M_2O_4(M=Ni,Mn) during which the tetravalent manganese ions are reduced to an oxidation state of 3.0.So the spinel phase can act as a host to insert back the extracted lithium ions(from the layered matrix) that could not embed back into the layered lattice to eliminate the irreversible capacity loss and increase the discharge capacity.Their electrochemical properties at room temperature showed a high capacity(about 275 mAh g^(-1) at 0.1 C) and exhibited good cycling performance.