Mn-based cathode materials for rechargeable batteries

The rapid expansion of renewable energies asks for great progress of energy-storage technologies for sustainable energy supplies,which raises the compelling demand of high-performance rechargeable batteries.To satisfy the huge demand from the coming energy-storage market,the resource and cost-effectiveness of rechargeable batteries become more and more important.Manganese(Mn)as a key transition element with advantages including high abundance,low cost,and low toxicity derives various kinds(spinels,layered oxides,polyanions,Prussian blue analogs,etc.)of high-performance Mn-based electrode materials,especially cathodes,for rechargeable batteries ranging from Li-ion batteries,Na-ion batteries,aqueous batteries,to multivalent metal-ion batteries.It is anticipated that Mn-based materials with Mn as the major transition-metal element will constitute a flourishing family of Mn-based rechargeable batteries(Mn RBs)for large-scale and differentiated energy-storage applications.On the other hand,several critical issues including Jahn-Teller effect,Mn dissolution,and O release greatly hinder the pace of Mn RBs,which require extensive material optimizations and battery/system improvements.This review aims to provide an investigation about Mn-based materials and batteries for the coming energy-storage demands,with compelling issues and challenges that must be overcome.

Nanostructured Mn-based oxides as high-performance cathodes for next generation Li-ion batteries

Mn-based oxides have been regarded as a promising family of cathode materials for high-performance lithium-ion batteries,but the practical applications have been limited because of severe capacity deterioration(such as Li Mn O_(2)and Li Mn_(2)O_(4))as well as further complications from successive structure changes during cycling,low initial coulombic efficiency(such as Li-rich cathode)and oxidization of organic carbonate solvents at high charge potential(such as Li Ni0.5 Mn1.5 O4).Large amounts of efforts have been concentrated on resolving these issues towards practical applications,and many vital progresses have been carried out.Hence,the primary target of this review is focused on different proposed strategies and breakthroughs to enhance the rate performance and cycling stability of nanostructured Mn-based oxide cathode materials for Li-ion batteries,including morphology control,ion doping,surface coatings,composite construction.The combination of delicate architectures with conductive species represents the perspective ways to enhance the conductivity of the cathode materials and further buffer the structure transformation and strain during cycling.At last,based on the elaborated progress,several perspectives of Mn-based oxide cathodes are summarized,and some possible attractive strategies and future development directions of Mn-based oxide cathodes with enhanced electrochemical properties are proposed.The review will offer a detailed introduction of various strategies enhancing electrochemical performance and give a novel viewpoint to shed light on the future innovation in Mn-based oxide cathode materials,which benefits the design and construction of high-performance Mn-based oxide cathode materials in the future.

Distinctive electrochemical performance of novel Fe-based Li-rich cathode material prepared by molten salt method for lithium-ion batteries

For constructing next-generation lithium-ion batteries with advanced performances,pursuit of highcapacity Li-rich cathodes has caused considerable attention.So far,the low discharge specific capacity and serious capacity fading are strangling the development of Fe-based Li-rich materials.To activate the extra-capacity of Fe-based Li-rich cathode materials,a facile molten salt method is exploited using an alkaline mixture of LiOH–LiNO3–Li2O2 in this work.The prepared Li1.09(Fe0.2Ni0.3Mn0.5)0.91O2 material yields high discharge specific capacity and good cycling stability.The discharge specific capacity shows an upward tendency at 0.1 C.After 60 cycles,a high reversible specific capacity of ~250 m Ah g-1is delivered.The redox of Fe3+/Fe4+and Mn3+/Mn4+are gradually activated during cycling.Notably,the redox reaction of Fe2+/Fe3+can be observed reversibly below 2 V,which is quite different from the material prepared by a traditional co-precipitation method.The stable morphology of fine nanoparticles(100–300 nm)is considered benefiting for the distinctive electrochemical performances of Li1.09(Fe0.2Ni0.3Mn0.5)0.91O2.This study demonstrates that molten salt method is an inexpensive and effective approach to activate the extra capacity of Fe-based Li-rich cathode material for high-performance lithium-ion batteries.

High-capacity Li-rich Mn-based Cathodes for Lithium-ion Batteries

Layered Li-rich Mn-based oxides are promising cathode materials for Li-ion batteries due to their high capacity and high operation voltage.However,their commercial applications are hindered by irreversible capacity loss in the first charge-discharge process,voltage decay during cycling,inefficient cyclability and rate capability.Many attempts have been performed to solve such issues,including the mechanism study and strategies to improve the electrochemical performance.This article provides a brief review and future perspective on the main challenges of the high-capacity Li-rich Mn-based cathodes for Li-ion batteries.

Realizing high initial Coulombic efficiency in manganese-based layered oxide cathodes for sodium-ion batteries via P2/O'3 biphasic structure optimization

Mn-based layered oxides are among the most promising cathode materials for sodium-ion batteries owing to the advantages of abundance,environmenta friendliness,low cost and high specific capacity.P2 and O'3 are two representative structures of Mn-based layered oxides.However,the P2 structure containing insufficien Na generally exhibits low initial charge capacity,while O'3structure with sufficient Na delivers high initial charge capacity but poor cycle stability.This study prepared a multitude of Na_(x)MnO_(2)(x=0.7,0.8,0.9)cathode materials with varying P2/O'3 ratios and further investigated their electrochemical performances.The optimized Na_(0.8)MnO_(2) comprising 69.9 wt%O'3 and 30.1 wt%P2 phase,exhibited relatively balanced specific capacity,Coulombic efficiency and cycle stability.Specifically,it achieved a high specific capacity of 128.9 mAh·g^(-1) with an initia Coulombic efficiency of 98.2%in half-cell configuration The Na_(0.8)MnO_(2)//hard carbon full cell also achieved a high specific capacity of 126.7 mAh·g^(-1) with an initia Coulombic efficiency of 98.9%.Moreover,the capacity fading mechanism was revealed by combining in-situ and ex-situ X-ray diffraction.The findings of this study provide theoretical guidance for further modification design of Mnbased layered cathodes.

Simultaneous surface modification method for 0.4Li2MnO3-0.6LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries： Acid treatment and LiCoPO4 coating

Li-rich layered cathode materials have been considered the most promising candidates for large-scale Li-ion batteries due to their low cost and high reversible capacity. However, these materials have many drawbacks that hinder commercialization, such as low initial efficiency and cyclability at elevated temperatures. To overcome these barriers, we propose an efficient and effective surface modification method, in which chemical activation （acid treatment） and LiCoPO4 coating were carried out simultaneously. During the synthesis, the lithium ions were extracted from the lattice, leading to improved Columbic efficiency, and these ions were used for the formation of LiCoPO4. The Ni and Co doped spinel phase was formed at the surface of the host material, which gives rise to the facile pathway for lithium ions. The LiCoPO4 and highly doped spinel on the surface acted as double protection layers that effectively prevented side reactions on the surface at 60℃. Moreover, the transition metal migration of the modified cathode was weakened, due to the presence of the spinel structure at the surface. Consequently, the newly developed Li-rich cathode material exhibited a high 1st efficiency of 94%, improved capacity retention of 82% during 100 cycles at 60℃, and superior rate capability of 62% at 12C （1C = 200 mA/g） rate at 24℃. In addition, the thermal stability of the modified cathode was significantly improved as compared to that of a bare counterpart at 4.6 V, showing a 60% decrease in the total heat generation.

Surface yttrium-doping induced by element segregation to suppress oxygen release in Li-rich layered oxide cathodes

Doping electrochemically inert elements in Li-rich layered oxide cathodes usually stabilizes the structure to improve electrochemical performance at the expense of available capacity.Here,we use an element segregation principle to realize a uniform surface doping without capacity sacrifice.On the basis of Hume-Rothery rule,element yttrium is chosen as a candidate dopant to spontaneously segregate at particle surface due to mismatched ionic size.Combined with X-ray photoelectron spectroscopy and electron energy loss spectroscopy mapping,yttrium is demonstrated uniformly distributed on particle surface.More importantly,a significant alleviation of oxygen release after surface doping is detected by operando differential electrochemical mass spectrometry.As a result,the modified sample exhibits improved reversibility of oxygen redox with 82.1%coulombic efficiency and excellent cycle performances with 84.15%capacity retention after 140 cycles.Postmortem analysis by transmission electron microscopy,Raman spectroscopy and X-ray diffraction reveal that the modified sample maintains the layered structure without a significant structure transformation after long cycles.This work provides an effective strategy with a series of elements to meet the industrial application.

Strategies for constructing manganese-based oxide electrode materials for aqueous rechargeable zinc-ion batteries

Commercial lithium-ion batteries (LIBs) have been widely used in various energy storage systems. However, many unfavorable factors of LIBs have prompted researchers to turn their attention to the development of emerging secondary batteries. Aqueous zinc ion batteries (AZIBs) present some prominent advantages with environmental friendliness, low cost and convenient operation feature. MnO_(2) electrode is the first to be discovered as promising cathode material. So far, manganese-based oxides have made significant progresses in improving the inherent capacity and energy density. Herein, we summarize comprehensively recent advances of Mn-based compounds as electrode materials for ZIBs. Especially, this review focuses on the design strategies of electrode structures, optimization of the electrochemical performance and the clarification of energy storage mechanisms. Finally, their future research directions and perspective are also proposed.

High-Performance Aqueous Zinc–Manganese Battery with Reversible Mn^(2+)/Mn^(4+) Double Redox Achieved by Carbon Coated MnO_x Nanoparticles

There is an urgent need for low-cost,high-energy-density,environmentally friendly energy storage devices to fulfill the rapidly increasing need for electrical energy storage.Multi-electron redox is considerably crucial for the development of high-energy-density cathodes.Here we present highperformance aqueous zinc-manganese batteries with reversible Mn2+/Mn4+ double redox.The active Mn4+is generated in situ from the Mn2+-containing MnOx nanoparticles and electrolyte.Benefitting from the low crystallinity of the birnessite-type MnO2 as well as the electrolyte with Mn2+additive,the MnOX cathode achieves an ultrahigh energy density with a peak of845.1 Wh kg-1 and an ultralong lifespan of 1500 cycles.The combination of electrochemical measurements and material characterization reveals the reversible Mn2+/Mn4+double redox(birnessite-type MnO2? monoclinic MnOOH and spinel ZnMn2O4 H?Mn2+ions).The reversible Mn2+/Mn4+double redox electrode reaction mechanism offers new opportunities for the design of low-cost,high-energy-density cathodes for advanced rechargeable aqueous batteries.

Surface modification with oxygen vacancy in Li-rich layered oxide Li1.2Mn0.54Ni0.13Co0.13O2 for lithium-ion batteries

A couple of layered Li-rich cathode materials Li1.2Mn0.54Ni0.13Co0.13O2 without any carbon modification are successfully synthesized by solvothermal and hydrothermal methods followed by a calcination process. The sample synthesized by the solvothermal method(S-NCM) possesses more homogenous microstructure, lower cation mixing degree and more oxygen vacancies on the surface, compared to the sample prepared by the hydrothermal method(H-NCM). The S-NCM sample exhibits much better cycling performance, higher discharge capacity and more excellent rate performance than H-NCM. At 0.2 C rate,the S-NCM sample delivers a much higher initial discharge capacity of 292.3 mAh g^-1 and the capacity maintains 235 m Ah g^-1 after 150 cycles(80.4% retention), whereas the corresponding capacity values are only 269.2 and 108.5 m Ah g^-1(40.3% retention) for the H-NCM sample. The S-NCM sample also shows the higher rate performance with discharge capacity of 118.3 mAh g^-1 even at a high rate of 10 C, superior to that(46.5 m Ah g^-1) of the H-NCM sample. The superior electrochemical performance of the S-NCM sample can be ascribed to its well-ordered structure, much larger specific surface area and much more oxygen vacancies located on the surface.