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.

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.

Single-crystalline Mn-based oxide as a high-rate and long-life cathode material for potassium-ion battery

Mn-based oxides are promising cathode materials for potassium-ion batteries due to their high theoretical ca-pacity and abundant raw materials.However,the anisotropic properties of their conventional polycrystalline structures lead to insufficient rate capability and cycle life.Here,a single-crystal Mn-based layered oxide,P3′-type K_(0.35)Mn_(0.8)Fe_(0.1)Cu_(0.1)O_(2)(KMFCO),is designed and synthesized through a bimetallic co-induction effect and used as a cathode for potassium-ion battery.Benefiting from a unique single-crystal structure that is devoid of grain boundaries,it achieves a higher Kþtransport rate and a reduced volume change during the Kþintercalation/deintercalation process.Accordingly,the single-crystal P3′-type KMFCO delivers superior rate capability(52.9 mAh g^(-1) at 1000 mA g^(-1))and excellent cycling stability(91.1%capacity retention after 500 cycles at 500 mA g^(-1)).A full cell assembled with the P3′-type KMFCO cathode and a graphite anode also exhibits a high reversible capacity(81.2 mAh g^(-1) at 100 mA g^(-1))and excellent cycling performance(97%capacity retention after 300 cycles).The strategy of developing single-crystal materials may offer a new pathway for maintaining structural stability and improving the rate capability of layered manganese oxide cathodes and beyond.

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.

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.

High-energy Mn-based layered cathodes for sodium-ion batteries

Sodium-ion batteries (SIBs) have great potential in large-scale energy storage applications due to the low cost and abundance of sodium resources (1,2)However, some critical issues, such as low energy density and inferior cycling performance, definitely hinder the practical application of SIBs, in part because of the bigger and heavier Na ion in contrast with the Li ion as an energy carrier (3)Recently, a surge of attention has been paid to the Mnbased materials due to the earth abundant and environmentally friendly manganese element [4,5].

In-situ oriented oxygen-defect-rich Mn-N-O via nitridation and electrochemical oxidation based on industrial-scale Mn_(2)O_(3) to achieve high-performance aqueous zinc ion battery

As a general problem in the field of batteries,materials produced on a large industrial scale usually possess unsatisfactory electrochemical performances.Among them,manganese-based aqueous rechargeable zinc-ion batteries(ARZBs)have been emerging as promising large-scale energy storage systems owing to their high energy densities,low manufacturing cost and intrinsic high safety.However,the direct application of industrial-scale Mn2O3(MO)cathode exhibits poor electrochemical performance especially at high current rates.Herein,a highly reversible Mn-based cathode is developed from the industrial-scale MO by nitridation and following electrochemical oxidation,which triples the ion diffusion rate and greatly promotes the charge transfer.Notably,the cathode delivers a capacity of 161 m Ah g^(-1) at a high current density of 10 A g^(-1),nearly-three times the capacity of pristine MO(60 m Ah g^(-1)).Impressive specific capacity(243.4 m Ah g^(-1))is obtained without Mn^(2+) additive added in the electrolyte,much superior to the pristine MO(124.5 m Ah g^(-1)),suggesting its enhanced reaction kinetics and structural stability.In addition,it possesses an outstanding energy output of 368.4 Wh kg^(-1) at 387.8 W kg^(-1),which exceeds many of reported cathodes in ARZBs,providing new opportunities for the large-scale application of highperformance and low-cost ARZBs.

Tuning Li-excess to optimize Ni/Li exchange and improve stability of structure in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode material for lithium-ion batteries

Ni/Li exchange is a detrimental effect on electrochemical performances for high-Ni cathode materials(LiNi_(x)Co_(y)Mn_(z)O_(2),x≥0.6).Adjusting Li-excess degree has been proved to be an effective way to optimize Ni/Li exchange in the materials.However,until now,how the Ni/Li exchange and thus the structural properties is affected by the Li-excess has not been understood and clearly elucidated in the literature.Herein,a feasible strategy is utilized to optimize Ni/Li exchange and the amount of anti-Li^(+)in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) by mixing Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)_(2) precursor with different amounts of lithium sources during lithiation.It was found that morphology and phase stability of the material can be tuned with moderate excessive lithium.With 10%Li-excess,LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) exhibits an initial discharge capacity of 211.5 mAh·g^(–1) at 0.1 C and maintains 93.3%of its initial capacity after 100 cycles at 1 C.Different technologies were used to characterize the materials and it shows that the formation of broader Li slab space,decreased anti-Ni^(2+)in Li layer,and gradient distribution of Ni3+in the surface is contributed to moderate Li-excess in the materials.Broader Li slab space facilitates diffusion of Li^(+),decreased antisite-Ni^(2+)and gradient distribution of Ni3+in materials surfaces optimizes the Ni/Li exchange.Based on these results,we thus believe that it is the moderate Li-excess in material that optimized the electrochemical performance of high-Ni cathode materials.

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.

Atomic engineering promoted electrooxidation kinetics of manganese-based cathode for stable aqueous zinc-ion batteries

Rechargeable zinc-based batteries with near-neutral media are standing in the middle of the energy storage field by virtue of their high safety and low cost.However,it is still imperative for Mn-based cathode to improve rate capacity by facilitating ions/electron transfer and long-cycle stability by suppressing Mn dissolution.Herein,promoting electrooxidation kinetics is proposed and employed to construct advanced Mn-Zn battery.The formation of carbon-protected birnessite-MnO_(2)is promoted via inducing the electron-donating capability of the heterointerface between the N-C coating and the defective MnO.Moreover,density functional theory calculations also demonstrate that N-C protected birnessite-MnO_(2)is more hydrophobic than pure birnessite-MnO_(2),which is beneficial to prohibiting Mn dissolution and other side reactions.As a result,the elaborate design realizes effective transformation from low valence to high valence Mn for high capacity(291 mAh·g^(−1))and protective bambooslike structure for rate capacity(126 mAh·g^(−1)at 5 A·g^(−1))and cycling stability(89%capacity retention after 2,000 cycles).The assembled flexible quasi-solid-state Mn-Zn pouch batteries display application prospects for wearable and implantable electronic devices.The atomic engineering promoting electrooxidation kinetics strategy will be instructive in activating other cathode materials and maximizing their capacity.

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.