MnO2 Cathode Material Research Articles

Layered Co doped MnO2 with abundant oxygen defects to boost aqueous zinc-ion storage

Zinc Manganese oxide (Zn/MnO2)-based aqueous battery is favored due to their high specific capacity, security and cost performance. Nevertheless, they usually problems of unstable cyclic structure and slow diffusion kinetics, restricting their practical application. Here, we have successfully synthesized a Co doped MnO2 cathode material with abundant defects on a carbon cloth substrate. Through a simple hydrothermal method, the Co element can be lightly intercalated in the two-dimensional (2D) layered α-MnO2 nanowires, inhibiting the structural transformation during the cycle and improve the stability of the material. Meanwhile, plasma technology facilitates the formation of oxygen vacancies in the electrode material, which not only accelerate electron diffusion but also improve the conductivity. Therefore, Zn/Co-MnO2 battery can reach a specific capacity of 511 mAh g−1 at 0.5A g−1 and the retention rate accomplish 98% at high current density. This research puts forward a strategy of element doping and physical preparation of oxygen vacancies, which provides the possibility to develop reversible Zn/MnO2-based aqueous battery cathode materials with high-performance.

In-situ Co-precipitated α-MnO2@2-methylimidazole cathode material for high performance zinc ion batteries

Zinc ion batteries (ZIBs) are newly emerging and widely attracted energy storage devices owing to its advantages of intrinsic safety and low-cost effectiveness. Herein, we reported a nanorod-like MnO2 cathode material composited with carbon and pyrrolic nitrogen by in-situ co-precipitation method at room temperature, which was used as ZIB cathode to deliver a high specific capacity of 339 mAh g−1 at 100 mA g−1 and a long cycle stability over 2000 cycles at 1000 mA g−1, resulting in the ultrahigh coulombic efficiencies approximate to 100%. The improved performance was attributed to the enhancement of structural stability and more zinc ion insertion sites after introducing the 2-methylimidazole (2-MI) coating layer. The phase transition of α-MnO2 @2-methylimidazole (α-MnO2 @2-MI) and the formation of more porous architecture could be the origin of the continuous capacity increasing in the initial several cycles, which was proved by the results of the ex-situ x-ray diffraction (XRD) and the scanning electronic microscope (SEM). This method can be a more realistic choice for the further commercial applications of low-cost and easily-accessed ZIBs with excellent electrochemical performance.

Understanding the Chemical Composition with Doping Aliovalent Ions, Followed by the Electrochemical Behavior for Surface-Modified Ni-Rich NMC Cathode Materials.

A comparative study of doping aliovalent ions, Zr- or Al-, into Ni-rich Li(Ni,Co,Mn)O2 cathode materials is conducted in terms of the electrochemical properties and chemical analysis, especially on the surface region. The solubility and chemical composition for the given sol-gel treatment matches well with the computational results with which the infinitesimal Zr-coating is identified as exhibiting increased charge capacity with prolonged cycle life. Specifically, the whole process can be understood by the suppressed lithium-ion charge transfer resistance (RCT) during the cycles, which can be facilitated by the decreased NiO formation during the cyclic reactions.

Fast and highly reversible Na+ intercalation/extraction in Zn/Mg dual-doped P2-Na0.67MnO2 cathode material for high-performance Na-ion batteries

Fast and highly reversible Na+ intercalation/extraction in Zn/Mg dual-doped P2-Na0.67MnO2 cathode material for high-performance Na-ion batteries

MnO2 cathode materials with the improved stability via nitrogen doping for aqueous zinc-ion batteries

The research and exploration of manganese-based aqueous zinc-ion batteries have been controversial of cycle stability and mechanism investigation, thus improving the stability and exploring storage mechanism are still the most main issue. Defect engineering has become an effective method to improve cycle stability. Herein, a nitrogen-doped ε-MnO2 (MnO2@N) has been prepared using electrochemical deposition and heat treatment under nitrogen atmosphere. As the cathode for zinc-ion batteries, the capacity retention rate of MnO2@N cathode is close to 100% after 500 cycles at 0.5 A g−1, while the capacity retention rate for the initial MnO2 cathode is 62%. At 5 A g−1, the capacity retention rate of MnO2@N cathode is 83% after 1000 cycles, which is much higher than the 27% capacity retention rate for the original MnO2 cathode. And it can be found that the oxygen vacancies increase after nitrogen doping, which can improve the conductivity of the MnO2@N cathode. Also, there is Mn-N bond in MnO2@N, which can enhance the electrochemical stability of MnO2@N cathode. In addition, the electrochemical mechanism of MnO2@N cathode has been explored by the CV, GCD and GITT tests. It is found that nitrogen doping promotes the intercalation of H+ and the corresponding capacity contribution. Compared with the original MnO2 cathode, the diffusion coefficient of H+ and Zn2+in MnO2@N cathode increases. Also, the reactions during the charging and discharging process are explored through the ex-situ XRD test. And this work may provide some new ideas for improving the stability of manganese-based zinc-ion batteries.

Comprehensive Electrochemical, Calorimetric Heat Generation and Safety Analysis of Na0.53MnO2 Cathode Material in Coin Cells

The sodium ion cells were assembled by using Na0.53MnO2 as cathode material, pure sodium metal as anode in case of half coin cells and coconut shell-derived hard carbon in case of full coin cells. Cyclic voltammetry, galvanostatic charge-discharge, and self-discharge analysis were conducted. A good rate capability, capacity retention, coulombic efficiency (99.5%), reproducibility and reversible Na-ion intercalation revealed a satisfactory performance of this cathode material. The safety related parameters including the heat generation during charging-discharging and thermal abuse tests have been executed by the means of sophisticated calorimetry instruments. It was observed that during the charging process less heat was generated than during discharging process. The exothermic reactions during thermal runaway were identified by using an accelerating rate calorimeter and pressure measurements during this thermal abuse test were performed as well. The thermal runaway of full coin cells occurred beyond 190 °C with a temperature rate (dT/dt) of 2.5 °C min−1. Such detailed analysis of heat generation and thermal abuse helps finding new and quantitative correlations between different critical thermal and safety related issues in future post Li batteries that are a prerequisite for the design of safer batteries, the safe upscaling and for the adaptation of the thermal management system.

Thermophysical Characterization of a Layered P2 Type Structure Na0.53MnO2 Cathode Material for Sodium Ion Batteries

Over the last decade, the demand for safer batteries with excellent performance and lower costs has been intensively increasing. The abundantly available precursors and environmental friendliness are generating more and more interest in sodium ion batteries (SIBs), especially because of the lower material costs compared to Li-ion batteries. Therefore, significant efforts are being dedicated to investigating new cathode materials for SIBs. Since the thermal characterization of cathode materials is one of the key factors for designing safe batteries, the thermophysical properties of a commercial layered P2 type structure Na0.53MnO2 cathode material in powder form were measured in the temperature range between −20 and 1200 °C by differential scanning calorimetry (DSC), laser flash analysis (LFA), and thermogravimetry (TG). The thermogravimetry (TG) was combined with mass spectrometry (MS) to study the thermal decomposition of the cathode material with respect to the evolved gas analysis (EGA) and was performed from room temperature up to 1200 °C. The specific heat (Cp) and the thermal diffusivity (α) were measured up to 400 °C because beyond this temperature, the cathode material starts to decompose. The thermal conductivity (λ) as a function of temperature was calculated from the thermal diffusivity, the specific heat capacity, and the density. Such thermophysical data are highly relevant and important for thermal simulation studies, thermal management, and the mitigation of thermal runaway.

Preintercalation Strategy in Manganese Oxides for Electrochemical Energy Storage: Review and Prospects.

Manganese oxides (MnO2 ) are promising cathode materials for various kinds of battery applications, including Li-ion, Na-ion, Mg-ion, and Zn-ion batteries, etc., due to their low-cost and high-capacity. However, the practical application of MnO2 cathodes has been restricted by some critical issues including low electronic conductivity, low utilization of discharge depth, sluggish diffusion kinetics, and structural instability upon cycling. Preintercalation of ions/molecules into the crystal structure with/without structural reconstruction provides essential optimizations to alleviate these issues. Here, the intrinsic advantages and mechanisms of the preintercalation strategy in enhancing electronic conductivity, activating more active sites, promoting diffusion kinetics, and stabilizing the structural integrity of MnO2 cathode materials are summarized. The current challenges related to the preintercalation strategy, along with prospects for the future research and development regarding its implementation in the design of high-performance MnO2 cathodes for the next-generation batteries are also discussed.

Lithium-ion (de)intercalation mechanism in core-shell layered Li(Ni,Co,Mn)O2 cathode materials

Abstract LiNixCoyMn1-x-yO2 (NCM) intercalation compounds with core-shell architecture have been found to be promising cathode candidates for next-generation lithium-ion battery applications. The NCM cathodes' functional properties are dependent on the transition metal relative ratios, making it a challenge to control the real structure of core-shell NCM cathode materials and to understand the synergistic effect of core and shell during the electrochemical cycling. Herein, a universal and facile synthetic strategy is developed to synthesize the NCM material composed of an inner Ni-rich core and a Mn-rich shell on a secondary particle level. Both the Ni-rich particle core and the Mn-rich outer surface possess a layered α–NaFeO2–type structure with the same space group (R 3 ‾ m). The in situ synchrotron-based X-ray diffraction and absorption spectroscopy results demonstrate that the two layered phases do not participate in the electrochemical reaction simultaneously during the first cycle between 2.7 and 4.3 V, while they exhibit a similar reversible (de)lithiation mechanism in the following cycles. These findings provide a new perspective for rational design of layered Ni-based cathode materials with high energy and long cycling life with particular two phase electrochemical characteristics.

Trace Nb-doped Na0.7Ni0.3Co0.1Mn0.6O2 with suppressed voltage decay and enhanced low temperature performance

The P2-type manganese-based Na0.7MnO2 cathode materials attract great interest due to their high theoretical capacity. However, these materials suffer from rapid capacity fading, poor rate performance and severe voltage decay resulting from phase transition and sluggish reaction kinetics. In this work we report a novel Nb-doped Na0.7[Ni0.3Co0.1Mn0.6]1-xNbxO2 with significantly suppressed voltage decay and enhanced cycling stability. The strong Nb-O bond can efficiently stabilize the TMO framework, and the as prepared material demonstrates much lower discharge midpoint voltage decay (0.132 V) than that of pristine one (0.319 V) after 200 cycles. Consequently, a remarkably improved cycling performance with a capacity retention of 87.9% after 200 cycle at 0.5 C is achieved, showing a 2.4 fold improvement as compared to the control sample Na0.7Ni0.3Co0.1Mn0.6O2 (∼37% rotation). Even at 2 C, a capacity retention of 68.4% is retained after 500 cycles. Remarkably, the as prepared material can be applied at low temperature of −20 °C, showing a capacity retention of 81% as compared to that at room temperature.

Physicochemical and electrochemical properties of sulfolane – Carbonate electrolytes for sodium-ion conduction

Abstract Solutions of 1 M NaClO4 in mixtures of carbonates, including EC:PC 1:1 vol. (EP11), EC:DMC 1:1 vol. (ED11), EC:PC:DMC 1:1:3 vol. (EPD113) and EC:PC:DMC 3:1:1 vol. (EPD311), and 10–50% vol. sulfolane (SL) as co-solvent were investigated as flame- and oxidation-resistant electrolytes for sodium-ion battery. The dependence of important features, including thermal and fiery behavior, ionic conductivity and oxidative stability, on SL content as well as the compatibility with Na0.44MnO2 cathode materials are essentially reported. It was revealed that the presence of a moderate SL amount effectively promotes the electrolyte safety profile while maintaining acceptable conductivity. Amongst concerned samples, EPD311-based electrolytes with SL content within the optimized range (10–30% vol.) were found to exhibit the best balanced inherent properties. They also perform well when coupled with Na0.44MnO2 cathode in coin-type half-cells. Discharge capacity values of around 85–95 mAh·g−1 (C/10 rate), with almost 100% capacity retention after 20 cycles and good rate capability were demonstrated. Remarkably, EPD311 + 10% SL electrolyte was able to deliver the full theoretical capacity of Na0.44MnO2 material (120 mAh·g−1) at the C/20 rate.

Introducing Oxygen Defects into Phosphate Ions Intercalated Manganese Dioxide/Vertical Multilayer Graphene Arrays to Boost Flexible Zinc Ion Storage

AbstractDesigned and fabricated flexible high‐performance MnO2 cathode materials are highly desirable for developing advanced rechargeable Zn–MnO2 batteries. In this work, a facile phosphorization process is reported for introducing oxygen defects into phosphate ions intercalated manganese dioxide/vertical multilayer graphene (VMG) arrays, forming an integrated P‐MnO2‐x@VMG cathode. The oxygen defects and phosphate ions intercalation are achieved simultaneously via phosphorization. The former can increase the electrical conductivity of MnO2, while the latter is able to expand its interlayer spacing accelerating ion transfer. Furthermore, flexible VMG conductive networks provide excellent peripheral charge transfer and endow the cathode with favorable mechanical strength. Benefiting from these virtues, the obtained P‐MnO2‐x@VMG cathode demonstrates high capacity (302.8 mAh g−1 at 0.5 A g−1) and long‐term cycling stability (>90% capacity retention after 1000 cycles at 2.0 A g−1) in aqueous electrolytes. More impressively, the P‐MnO2‐x@VMG cathode exhibits a high energy density of 369.5 Wh kg−1 in quasi‐solid‐state flexible devices (P‐MnO2‐x@VMG//Zn@VMG), and thereby shows great prospects for applications in wearable electronics. This work demonstrates a new synergistic way to construct high‐performance electrodes for energy storage toward divalent metal ions.

An enhanced electrochemical properties of novel tin based layered Li(Ni–Sn–Mn)O2 cathode material for rechargeable Li-ion batteries

In this work, the synthesis of newly prepared cathode material, Li(NixSnyMnz)O2, which is used as a positive electrode material and is suitable for energy storage and conversion in lithium-ion rechargeable batteries, are taken into account. Indeed the main goal is to replace the conventional cathodes such as lithium cobalt oxide, lithium manganese oxide and lithium iron phosphate in view of achieving higher capacity, long cycle life, and better environmental compatible compounds. The stoichiometric ratio of the Li(Ni0.4Sn0.3Mn0.3)O2 material exhibits better performance, after evaluating with various other ratios and it is prepared via a hydrothermal process using Teflon lined autoclave reactor vessel and followed by calcination technique. Furthermore, the prepared material is subjected to XRD, FE-SEM with EDAX, TEM analysis, and also the electrochemical test has been assessed. It includes electrochemical impedance spectroscopy and electrochemical charge-discharge studies using Li/Li(Ni0.4Sn0.3Mn0.3)O2 coin type half-cell (2032 size) at the 0.1 C rate and the voltage range between 4.3–2.5 V. From the electrochemical studies, it has been found that the first charge-discharge capacity obtained of 192 mAh g−1 and 176 mAh g−1, respectively. Thus, the battery efficiency acquired is 97% and it has been maintained after the 1st cycle with a good cyclability also without huge fading. It may be a suitable positive electrode in the half cell Li-ion rechargeable batteries.

An aqueous rechargeable sodium−magnesium mixed ion battery based on NaTi2(PO4)3–MnO2 system

In order to develop an aqueous battery with high specific capacity, we synthesized NaTi2(PO4)3 anode material and MnO2 cathode material, and studied the electrochemical properties of the two materials in Na2SO4, MgSO4 and Na2SO4−MgSO4 mixed aqueous electrolytes, respectively. The results show that MnO2 has excellent electrochemical properties in electrolyte containing Mg2+ and its specific capacity can reach about 100 mAh g−1. Na+ and Mg2+ can be intercalated/deintercalated reversibly from the MnO2 cathode material at the same time, while the NaTi2(PO4)3 anode material can only intercalate/deintercalate Na+. Based on this, we constructed an aqueous sodium-magnesium hybrid ion battery system. The anode is carbon-coated NaTi2(PO4)3 material, and the cathode is MnO2/CNTs composite material. The electrolyte is Na2SO4 and MgSO4 mixed aqueous solution. The working voltage of the battery is about 1.4 V and its capacity can reach 97 mAh g−1.

P2/O3 phase-integrated Na0.7MnO2 cathode materials for sodium-ion rechargeable batteries

We describe a phase-integrated P2-Na0.7MnO2/O3-NaMnO2 sodium manganese oxide (Na0.7MnO2) cathode material for sodium-ion rechargeable batteries. By changing the crystallization cooling rate after the calcination of P2/O3-Na0.7MnO2, the ratio between the two different (P2-Na0.7MnO2 and O3-NaMnO2) phases (and the Mn4+/Mn3+ ratio) in the Na0.7MnO2 material could be controlled. The P2/O3-Na0.7MnO2 sample prepared by fast cooling contains the optimum content of the two principal phases and showed excellent electrochemical performance because of the synergy between the fast kinetics of the P2-Na0.7MnO2 phase and high capacity of the O3-NaMnO2 phase. The stability of the layered crystal structure of Na0.7MnO2 was also improved by increasing the portion of the P2-Na0.7MnO2 phase, which has a higher average oxidation state of Mn compared to that in O3-NaMnO2; this suppressed the Jahn–Teller distortion during cycling.

An X-ray Tomographic Study of Rechargeable Zn/MnO₂ Batteries.

We present non-destructive and non-invasive in operando X-ray tomographic investigations of the charge and discharge behavior of rechargeable alkaline-manganese (RAM) batteries (Zn-MnO2 batteries). Changes in the three-dimensional structure of the zinc anode and the MnO2 cathode material after several charge/discharge cycles were analyzed. Battery discharge leads to a decrease in the zinc particle sizes, revealing a layer-by-layer dissolving behavior. During charging, the particles grow again to almost their initial size and shape. After several cycles, the particles sizes slowly decrease until most of the particles become smaller than the spatial resolution of the tomography. Furthermore, the number of cracks in the MnO2 bulk continuously increases and the separator changes its shape. The results are compared to the behavior of a conventional primary cell that was also charged and discharged several times.

Controlled synthesis of Na0.44MnO2 cathode material for sodium ion batteries with superior performance through urea-based solution combustion synthesis

As a promising cathode material in sodium-ion batteries (SIBs) for large-scale energy storage applications, tunnel-structured Na0.44MnO2 is prepared by a facile and controllable urea-based solution combustion synthesis (SCS) method with subsequent calcination. The phase purity, morphology, homogeneity and particle size of the samples are quite dependent on the SCS fuel condition. The optimal sample f0.75 displays pure phase composition, high crystallinity and hierarchical-structured particles with uniform size of several microns, which are the agglomerates of well-calcined nano-rods and nano-slabs. The sample exhibits the highest reversible capacity of around 117 mAh/g at 0.1 C, good rate capability and excellent cycling stability, which even presents a high capacity of 100 mAh/g at 4 C after 300 cycles. The facile and controllable production and the superior electrochemical performance of the Na0.44MnO2 makes it a promising cathode material for the development of practical SIBs.

A general gelatin-assisted strategy to hierarchical porous transition metal oxides with excellent lithium-ion storage

Transition metal oxides are widely researched as anode materials for lithium-ion batteries due to their high theoretical capacity. However, the application of this material is always restricted by the low electroconductivity and huge volume change. In this work, we develop a general strategy, the gelatin-assisted hydrothermal-calcination process, to prepare hierarchical porous transition metal oxides and their composites, including Fe2O3, Mn2O3, Co3O4, ZnCo2O4, MnCo2O4 and (Co,Mn)3O4. Depending on the unique molecular structure of gelatin, metal ions in the solution can be located in amino and carboxyl existing in natural polymer, which lead to the formation of hierarchical precursor. Typically, step-like hierarchical porous Fe2O3 and ZnCo2O4 exhibit the outstanding performance of 1301.7 mAh g−1 after 600 cycles and 1005.8 mAh g−1 after 180 cycles at 500 mA g−1 for lithium-ion storage. In addition, Na0.7MnO2 cathode material prepared from MnCO3 also delivers the 140.9 mAh g−1 over 50 cycles at 40 mA g−1 for sodium-ion storage. The stable structure, abundant materials, low toxicity and excellent performance promote the development of anode materials. Moreover, this easily-extended method also provides a strategy to obtain hierarchical materials, which expands the application of transition metal oxides in other fields.

Effect of Graphene Oxide on Electrochemical Behavior of MnO2/GO Supercapacitor

Supercapacitors have received a lot of attention due to their high-power performance, long cycle life low maintenance, and for applications in hybrid electric vehicles, portable electronic devices, and power back-up devices [1-3]. Various researchers studied MnO2 cathode materials for application in electrochemical capacitors, because of its low cost and natural abundance [2, 3]. However, MnO2 has limited electrochemical performance because of its poor conductivity and low surface area. To improve the electrochemical performances of MnO2, we have synthesized MnO2/graphene oxide (GO) nanocomposite with varying concentration of GO (0.4 mg/ml and 0.8 mg/ml). GO/MnO2 nanocomposite was synthesized by adding KMnO4 in a solution of water and ethanol (3:1), containing desired amount of GO. The brown precipitates were obtained after a continuous stirring for 1 hr. The precipitate was washed and dried to obtain the GO/MnO2 nanocomposites. The electrodes were prepared by spreading a slurry of GO/MnO2 powder, carbon black, PTFE binder (80:15:5 weight ratio) onto Ni mesh. The electrochemical characterizations were carried out in an aqueous solution of 1M Na2SO4. The charge discharge studies were carried out between 100 mA/g to 5A/g current range. The discharge capacities were found to be 230 F/g and 105 F/g at a current of 100 mA/g and 5A/g, respectively for 20mg GO. The detailed results will be presented at the 233rd Electrochemical Society Meeting.

Fast and scalable synthesis of durable Na0.44MnO2 cathode material via an oxalate precursor method for Na-ion batteries

Na0.44MnO2 has aroused global interest as a promising cathode material for sodium ion batteries due to its unique tunnel structure. Rod-like Na0.44MnO2 is synthesized here via a simple, fast and environment-friendly oxalate precursor-based process, and the electrochemical performances, as well as the structural evolution within the electrode redox process and the chemical mechanism for material synthesis, are systematically investigated. The Na0.44MnO2 material prepared at 900 °C for 3 h (denoted as NMO-9003) possesses the highest reversible capacity of 120 mAh g−1 at 0.2 C and an optimal rate capacity of 106 mAh g−1 at 1 C, while its long-term capacity retention is 86% after 500 cycles at 20 C, indicating superior structural reversibility. In addition, the NMO-9003 sample shows the fastest cationic diffusion rate at approximately 1.2 × 10−13 cm2 s−1. The density functional theory (DFT)-based calculation is adopted to explore the lattice variation of Na0.44MnO2 upon the electrode process, which confirms that the host structure bears a minor volume change approximately 7% from 2.0 to 3.8 V, well demonstrating the origin of excellent reversibility.