The rhombohedral sodium manganese hexacyanoferrate (MnHCF) only containing cheap Fe and Mn metals was regarded as a scalable, low‐cost, and high‐energy cathode material for Na‐ion batteries. However, ...the unexpected Jahn‐teller effect and significant phase transformation would cause Mn dissolution and anisotropic volume change, thus leading to capacity loss and structural instability. Here we report a simple room‐temperature route to construct a magical CoxB skin on the surface of MnHCF. Benefited from the complete coverage and the buffer effect of CoxB layer, the modified MnHCF cathode exhibits suppressed Mn dissolution and reduced intergranular cracks inside particles, thereby demonstrating thousands‐cycle level cycling lifespan. By comparing two key parameters in the real energy world, i.e., cost per kilowatt‐hours and cost per cycle‐life, our developed CoxB coated MnHCF cathode demonstrates more competitive application potential than the benchmarking LiFePO4 for Li‐ion batteries.
The sodium manganese hexacyanoferrate full‐cell configurations show comparable energy density to that of the well‐known LiFePO4 full cells.
The high weight fraction of the electrolyte in lithium–sulfur (Li–S) full cell is the primary reason its specific energy is much below expectations. Thus far, it is still a challenge to reduce the ...electrolyte volume of Li–S batteries owing to their high cathode porosity and electrolyte depletion from the Li metal anode. Herein, we propose an ultralight electrolyte (0.83 g mL−1) by introducing a weakly‐coordinating and Li‐compatible monoether, which greatly reduces the weight fraction of electrolyte within the whole cell and also enables Li–S pouch cell functionality under lean‐electrolyte conditions. Compared to Li–S batteries using conventional counterparts (≈1.2 g mL−1), the Li–S pouch cells equipped with our ultralight electrolyte could achieve an ultralow electrolyte weight/capacity ratio (E/C) of 2.2 g Ah−1 and realize a 19.2 % improvement in specific energy (from 329.9 to 393.4 Wh kg−1) under E/S=3.0 μL mg−1. Moreover, more than 20 % improvement in specific energy could be achieved using our ultralight electrolyte at various E/S ratios.
Ultralight electrolytes with a density of 0.83 g mL−1 were proposed by introducing a weakly‐coordinating and Li‐compatible monoether. A weight reduction of more than 30 % per volume was realized relative to the conventional electrolyte, also enabling Li–S pouch cell functionality under lean‐electrolyte conditions. When applied in pouch cells, ≈20 % improvement in specific energy could be achieved at various E/S ratios.
Liquid electrolyte plays a key role in commercial lithium-ion batteries to allow conduction of lithium-ion between cathode and anode. Traditionally, taking into account the ionic conductivity, ...viscosity and dissolubility of lithium salt, the salt concentration in liquid electrolytes is typically less than 1.2 mol l(-1). Here we show a new class of 'Solvent-in-Salt' electrolyte with ultrahigh salt concentration and high lithium-ion transference number (0.73), in which salt holds a dominant position in the lithium-ion transport system. It remarkably enhances cyclic and safety performance of next-generation high-energy rechargeable lithium batteries via an effective suppression of lithium dendrite growth and shape change in the metallic lithium anode. Moreover, when used in lithium-sulphur battery, the advantage of this electrolyte is further demonstrated that lithium polysulphide dissolution is inhibited, thus overcoming one of today's most challenging technological hurdles, the 'polysulphide shuttle phenomenon'. Consequently, a coulombic efficiency nearing 100% and long cycling stability are achieved.
Na-ion batteries have been considered promising candidates for stationary energy storage. However, their wide application is hindered by issues such as high cost and insufficient electrochemical ...performance, particularly for cathode materials. Here, we report a solvent-free mechanochemical protocol for the in-situ fabrication of sodium vanadium fluorophosphates. Benefiting from the nano-crystallization features and extra Na-storage sites achieved in the synthesis process, the as-prepared carbon-coated Na
(VOPO
)
F nanocomposite exhibits capacity of 142 mAh g
at 0.1C, higher than its theoretical capacity (130 mAh g
). Moreover, a scaled synthesis with 2 kg of product was conducted and 26650-prototype cells were demonstrated to proof the electrochemical performance. We expect our findings to mark an important step in the industrial application of sodium vanadium fluorophosphates for Na-ion batteries.
Most P2-type layered oxides exhibit Na(+)/vacancy-ordered superstructures because of strong Na(+)-Na(+) interaction in the alkali metal layer and charge ordering in the transition metal layer. These ...superstructures evidenced by voltage plateaus in the electrochemical curves limit the Na(+) ion transport kinetics and cycle performance in rechargeable batteries. Here we show that such Na(+)/vacancy ordering can be avoided by choosing the transition metal ions with similar ionic radii and different redox potentials, for example, Cr(3+) and Ti(4+). The designed P2-Na(0.6)Cr(0.6)Ti(0.4)O2 is completely Na(+)/vacancy-disordered at any sodium content and displays excellent rate capability and long cycle life. A symmetric sodium-ion battery using the same P2-Na(0.6)Cr(0.6)Ti(0.4)O2 electrode delivers 75% of the initial capacity at 12C rate. Our contribution demonstrates that the approach of preventing Na(+)/vacancy ordering by breaking charge ordering in the transition metal layer opens a simple way to design disordered electrode materials with high power density and long cycle life.
A uniform nitrogen‐doped carbon coating layer is formed on Li4Ti5O12 particles by mixing porous Li4Ti5O12 powder with an ionic liquid and then treating the mixture at moderate temperature. Uniformly ...coated Li4Ti5O12 is shown to have significantly improved rate capability and cycling performance for Li‐ion batteries. This relatively simple approach is versatile and can be extended to modify other electrode materials for electrochemical devices.
Narrow electrochemical stability window (1.23 V) of aqueous electrolytes is always considered the key obstacle preventing aqueous sodium‐ion chemistry of practical energy density and cycle life. The ...sodium‐ion water‐in‐salt electrolyte (NaWiSE) eliminates this barrier by offering a 2.5 V window through suppressing hydrogen evolution on anode with the formation of a Na+‐conducting solid‐electrolyte interphase (SEI) and reducing the overall electrochemical activity of water on cathode. A full aqueous Na‐ion battery constructed on Na0.66Mn0.66Ti0.34O2 as cathode and NaTi2(PO4)3 as anode exhibits superior performance at both low and high rates, as exemplified by extraordinarily high Coulombic efficiency (>99.2%) at a low rate (0.2 C) for >350 cycles, and excellent cycling stability with negligible capacity losses (0.006% per cycle) at a high rate (1 C) for >1200 cycles. Molecular modeling reveals some key differences between Li‐ion and Na‐ion WiSE, and identifies a more pronounced ion aggregation with frequent contacts between the sodium cation and fluorine of anion in the latter as one main factor responsible for the formation of a dense SEI at lower salt concentration than its Li cousin.
The sodium‐ion water‐in‐salt electrolyte with a wide electrochemical window is proposed through suppressing hydrogen evolution on anode with the formation of a Na+‐conducting solid‐electrolyte interphase and reducing the overall electrochemical activity of water on cathode. A full aqueous Na‐ion battery constructed on Na0.66Mn0.66Ti0.34O2 as cathode and NaTi2(PO4)3 as anode exhibits superior performance at both low (0.2 C) and high (1 C) rates.
Sodium (Na) metal, which possesses a high theoretical capacity and the lowest electrochemical potential, is regarded as a promising anode material for Na–metal batteries. However, both Na dendrite ...growth and large volume change in cycling have severely impeded its practical applications. This study demonstrates that a 3D flexible carbon (C) felt which is already commercialized in large‐scale can be employed as a host for prestoring Na via a melt infusion strategy, through which a Na/C composite anode is obtained. The resulting anode exhibits a stable voltage profile and a small hysteresis over 120 cycles in carbonate‐based electrolytes in symmetrical cells owing to the fact that the metallic Na is confined in a conductive carbon felt host, which increases the Na+ deposition sites to lower the effective current density and render a uniform Na nucleation, restricting the dimension change in electrochemical cycling. More importantly, effective inhibition of Na dendrite growth and large volume change is achieved. When coupled with a Na0.67Ni0.33Mn0.67O2 cathode, the Na/C composite demonstrates a good suitability in full cells. This work provides an alternative option for the fabrication of stable Na metal anodes, which is of great significance for the practical applications of Na metal anodes in high‐energy‐density batteries.
Encapsulating metallic Na in a 3D carbon felt host, which increases the Na+ deposition sites to lower the effective current density, guides a uniform Na nucleation, restricts the dimension change during repetitive plating/stripping, and can greatly enhance the stability of the Na metal anode.
Porous structure design is generally considered to be a reliable strategy to boost ion transport and provide active sites for disordered carbon anodes of Na‐ion batteries (NIBs). Herein, a type of ...waste cork‐derived hard carbon material (CC) is reported for efficient Na storage via tuning the pore species. Benefiting from the natural holey texture of this renewable precursor, CCs deliver a novel hierarchical porous structure. The effective skeletal density test combined with small angle X‐ray scattering analysis (SAXS) is used to obtain the closed pore information. Based on a detailed correlation analysis between pore information and the electrochemical performance of CCs, improving pyrolysis temperature to reduce open pores (related to initial capacity loss) and increase closed pores (related to plateau capacity) endows an optimal CC with a high specific capacity of ≈360 mAh g−1 in half‐cells and a high energy density of 230 Wh kg−1 in full‐cells with a capacity retention of 71% after 2000 cycles at 2C rate. The bioinspired high temperature pore‐closing strategy and the new insights about the pore structure–performance relationship provide a rational guide for designing porous carbon anode of NIBs with tailored pore species and high Na storage capacity.
A type of waste cork‐derived, hard carbon electrode, with hierarchical porous morphology delivers satisfactory electrochemical performance in Na‐ion batteries (both half‐cells and full‐cells) via tuning the pore species. Detailed pore analysis reveals a clear pore structure–performance relationship to guide the designing of advanced porous carbon anode and the related high temperature pore‐closing strategy can be extended to other pristine open‐pore‐rich carbon.
Potassium ion batteries (KIBs) have emerged as a promising energy storage system, but the stability and high rate capability of their electrode materials, particularly carbon as the most investigated ...anode ones, become a primary challenge. Here, it is identified that pitch‐derived soft carbon, a nongraphitic carbonaceous species which is paid less attention in the battery field, holds special advantage in KIB anodes. The structural flexibility of soft carbon makes it convenient to tune its crystallization degree, thereby modulating the storage behavior of large‐sized K+ in the turbostratic carbon lattices to satisfy the need in structural resilience, low‐voltage feature, and high transportation kinetics. It is confirmed that a simple thermal control can produce structurally optimized soft carbon that has much better battery performance than its widely reported carbon counterparts such as graphite and hard carbon. The findings highlight the potential of soft carbon as an interesting category suitable for high‐performance KIB electrode and provide insights for understanding the complicated K+ storage mechanisms in KIBs.
The cycling stability of anode materials in potassium‐ion batteries (KIBs) is challenged by the large size of K+ itself. The findings not only demonstrate the promising potential of soft carbon as a category suitable for high‐performance KIB electrodes, but also provide insights into the complicated K+ storage mechanisms in carbon anodes of KIBs.
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