Engineering Na+-layer spacings to stabilize Mn-based layered cathodes for sodium-ion batteries.
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ABSTRACT:
SUBMITTER: Zuo W
PROVIDER: S-EPMC8360981 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The corrosion of Li- and Mn-rich (LMR) electrode materials occurring at the solid-liquid interface will lead to extra electrolyte consumption and transition metal ions dissolution, causing rapid voltage decay, capacity fading, and detrimental structure transformation. Herein, a novel strategy is introduced to suppress this corrosion by designing an Na+-doped LMR (Li1.2Ni0.13Co0.13Mn0.54O2) with abundant stacking faults, using sodium dodecyl sulfate as surfactant to ensure the uniform distribution of Na+ in deep grain lattices-not just surface-gathering or partially coated. The defective structure and deep distribution of Na+ are verified by Raman spectrum and high-resolution transmission electron microscopy of the as-prepared electrodes before and after 200 cycles. As a result, the modified LMR material shows a high reversible discharge specific capacity of 221.5 mAh g-1 at 0.5C rate (1C = 200 mA g-1) after 200 cycles, and the capacity retention is as high as 93.1% which is better than that of pristine-LMR (64.8%). This design of Na+ is uniformly doped and the resultanting induced defective structure provides an effective strategy to enhance electrochemical performance which should be extended to prepare other advanced cathodes for high performance lithium-ion batteries.
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Project description:Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage. Layered oxides, especially manganese-based oxides, are the most popular cathodes due to their high reversible capacity and use of earth-abundant elements. However, less noticed is the fact that the interface of layered cathodes always suffers from atmospheric and electrochemical corrosion, leading to severely diminished electrochemical properties. Herein, we demonstrate an environmentally stable interface via the superficial concentration of titanium, which not only overcomes the above limitations, but also presents unique surface chemical/electrochemical properties. The results show that the atomic-scale interface is composed of spinel-like titanium (III) oxides, enhancing the structural/electrochemical stability and electronic/ionic conductivity. Consequently, the interface-engineered electrode shows excellent cycling performance among all layered manganese-based cathodes, as well as high-energy density. Our findings highlight the significance of a stable interface and, moreover, open opportunities for the design of well-tailored cathode materials for sodium storage.The interface of layered cathodes for sodium ion batteries is subject to atmospheric and electrochemical corrosions. Here, the authors demonstrate an environmentally stable interface via titanium enriched surface reconstruction in a layered manganese-based oxide.
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Project description:ConspectusLithium-ion batteries (LIBs) are ubiquitous in all modern portable electronic devices such as mobile phones and laptops as well as for powering hybrid electric vehicles and other large-scale devices. Sodium-ion batteries (NIBs), which possess a similar cell configuration and working mechanism, have already been proven as ideal alternatives for large-scale energy storage systems. The advantages of NIBs are as follows. First, sodium resources are abundantly distributed in the earth's crust. Second, high-performance NIB cathode materials can be fabricated by using solely inexpensive and noncritical transition metals such as manganese and iron, which further reduces the cost of the required raw materials. Recently, the unprecedented demand for lithium and other critical minerals has driven the cost of these primary raw materials (which are utilized in LIBs) to a historic high and thus triggered the commercialization of NIBs.Sodium layered transition metal oxides (NaxTMO2, TM = transition metal/s), such as Mn-based sodium layered oxides, represent an important family of cathode materials with the potential to reduce costs, increase energy density and cycling stability, and improve the safety of NIBs for large-scale energy storage. However, these layered oxides face several key challenges, including irreversible phase transformations during cycling, poor air stability, complex charge-compensation mechanisms, and relatively high cost of the full cell compared to LiFePO4-based LIBs. Our work has focused on the techno-economic analysis, the degradation mechanism of NaxTMO2 upon cycling and air exposure, and the development of effective strategies to improve their electrochemical performances and air stability. Correlating structure-performance relationships and establishing general design strategies of NaxTMO2 must be considered for the commercialization of NIBs.In this Account, we discuss the recent progress in the development of air-stable, electrochemically stable, and cost-effective NaxTMO2. The favorable redox-active cations for NaxTMO2 are emphasized in terms of abundance, cost, supply, and energy density. Different working mechanisms related to NaxTMO2 are summarized, including the electrochemical reversibility, the main structural transformations during the charge and discharge processes, and the charge-compensation mechanisms that accompany the (de)intercalation of Na+ ions, followed by discussions to improve the stability toward ambient air and upon cycling. Then the techno-economics are presented, with an emphasis on cathodes with different chemical compositions, cost breakdown of battery packs, and Na deficiency, factors that are critical to the large-scale implementation. Finally, this Account concludes with an overview of the remaining challenges and new opportunities concerning the practical applications of NaxTMO2, with an emphasis on the cost, large-scale fabrication capability, and electrochemical performance.
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Project description:Layered Na-based oxides with the general composition of NaxTMO2 (TM: transition metal) have attracted significant attention for their high compositional diversity that provides tunable electrochemical performance for electrodes in sodium-ion batteries. The various compositions bring forward complex structural chemistry that is decisive for the layered stacking structure, Na-ion conductivity, and the redox activity, potentially promising new avenues in functional material properties. In this work, we have explored the maximum Na content in P2-type layered oxides and discovered that the high-content Na in the host enhances the structural stability; moreover, it promotes the oxidation of low-valent cations to their high oxidation states (in this case Ni2+). This can be rationalized by the increased hybridization of the O(2p)-TM(3d-eg*) states, affecting both the local TM environment as well as the interactions between the NaO2 and TMO2 layers. These properties are highly beneficial for the Na storage capabilities as required for cathode materials in sodium-ion batteries. It leads to excellent Na-ion mobility, a large storage capacity (>100 mAh g-1 between 2.0-4.0 V), yet preventing the detrimental sliding of the TMO2 layers (P2-O2 structural transition), as reflected by the ultralong cycle life (3000 (dis)charge cycles demonstrated). These findings expand the horizons of high Na-content P2-type materials, providing new insights of the electronic and structural chemistry for advanced cathode materials.
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Project description:Layered intercalation compounds are the dominant cathode materials for rechargeable Li-ion batteries. In this article we summarize in a pedagogical way our work in understanding how the structure's topology, electronic structure, and chemistry interact to determine its electrochemical performance. We discuss how alkali-alkali interactions within the Li layer influence the voltage profile, the role of the transition metal electronic structure in dictating O3-structural stability, and the mechanism for alkali diffusion. We then briefly delve into emerging, next-generation Li-ion cathodes that move beyond layered intercalation hosts by discussing disordered rocksalt Li-excess structures, a class of materials which may be essential in circumventing impending resource limitations in our era of clean energy technology.
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Project description:Na-ion cathode materials operating at high voltage with a stable cycling behavior are needed to develop future high-energy Na-ion cells. However, the irreversible oxygen redox reaction at the high-voltage region in sodium layered cathode materials generates structural instability and poor capacity retention upon cycling. Here, we report a doping strategy by incorporating light-weight boron into the cathode active material lattice to decrease the irreversible oxygen oxidation at high voltages (i.e., >4.0 V vs. Na+/Na). The presence of covalent B-O bonds and the negative charges of the oxygen atoms ensures a robust ligand framework for the NaLi1/9Ni2/9Fe2/9Mn4/9O2 cathode material while mitigating the excessive oxidation of oxygen for charge compensation and avoiding irreversible structural changes during cell operation. The B-doped cathode material promotes reversible transition metal redox reaction enabling a room-temperature capacity of 160.5 mAh g-1 at 25 mA g-1 and capacity retention of 82.8% after 200 cycles at 250 mA g-1. A 71.28 mAh single-coated lab-scale Na-ion pouch cell comprising a pre-sodiated hard carbon-based anode and B-doped cathode material is also reported as proof of concept.
| S-EPMC8421359 | biostudies-literature
Project description:Developing sodium-ion batteries for large-scale energy storage applications is facing big challenges of the lack of high-performance cathode materials. Here, a series of new cathode materials Na0.66Co x Mn0.66-x Ti0.34O2 for sodium-ion batteries are designed and synthesized aiming to reduce transition metal-ion ordering, charge ordering, as well as Na+ and vacancy ordering. An interesting structure change of Na0.66Co x Mn0.66-x Ti0.34O2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na0.66Co0.22Mn0.44Ti0.34O2 with a P2-type layered structure delivers a reversible capacity of 120 mAh g-1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g-1 can still be obtained, indicating a promising rate capability. The low valence Co2+ substitution results in the formation of average Mn3.7+ valence state in Na0.66Co0.22Mn0.44Ti0.34O2, effectively suppressing the Mn3+-induced Jahn-Teller distortion, and in turn stabilizing the layered structure. X-ray absorption spectroscopy results suggest that the charge compensation of Na0.66Co0.22Mn0.44Ti0.34O2 during charge/discharge is contributed by Co2.2+/Co3+ and Mn3.3+/Mn4+ redox couples. This is the first time that the highly reversible Co2+/Co3+ redox couple is observed in P2-layered cathodes for sodium-ion batteries. This finding may open new approaches to design advanced intercalation-type cathode materials.
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Project description:Nanoparticles produced by bacteria, fungi, or plants generally have physicochemical properties such as size, shape, crystalline structure, magnetic properties, and stability which are difficult to obtain by chemical synthesis. For instance, Mn(II)-oxidizing organisms promote the biomineralization of manganese oxides with specific textures under ambient conditions. Controlling their crystallinity and texture may offer environmentally relevant routes of Mn oxide synthesis with potential technological applications, e.g., for energy storage. However, whereas the electrochemical activity of synthetic (abiotic) Mn oxides has been extensively studied, the electroactivity of Mn biominerals has been seldom investigated yet. Here we evaluated the electroactivity of biologically induced biominerals produced by the Mn(II)-oxidizer bacteria Pseudomonas putida strain MnB1. For this purpose, we explored the mechanisms of Mn biomineralization, including the kinetics of Mn(II) oxidation, under different conditions. Manganese speciation, biomineral structure, and texture as well as organic matter content were determined by a combination of X-ray diffraction, electron and X-ray microscopies, and thermogravimetric analyses coupled to mass spectrometry. Our results evidence the formation of an organic-inorganic composite material and a competition between the enzymatic (biotic) oxidation of Mn(II) to Mn(IV) yielding MnO2 birnessite and the abiotic formation of Mn(III), of which the ratio depends on oxygenation levels and activity of the bacteria. We reveal that a subtle control over the conditions of the microbial environment orients the birnessite to Mn(III)-phases ratio and the porosity of the assembly, which both strongly impact the bulk electroactivity of the composite biomineral. The electrochemical properties were tested in lithium battery configuration and exhibit very appealing performances (voltage, capacity, reversibility, and power capability), thanks to the specific texture resulting from the microbially driven synthesis route. Given that such electroactive Mn biominerals are widespread in the environment, our study opens an alternative route for the synthesis of performing electrode materials under environment-friendly conditions.
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