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The modern lithium-ion battery (LIB) configuration was enabled by the “magic chemistry” between ethylene carbonate (EC) and graphitic carbon anode. Despite the constant changes of cathode chemistries with improved energy densities, EC-graphite combination remained static during the last three decades. While the interphase generated by EC protects the fragile graphitic structure, the intrinsic disadvantages of EC (high viscosity, high melting point, excessive interphase growth) lead to mediocre power density and poor performances of LIB at sub-zero temperatures, where lithium depositions form upon charging. Such performance compromises arise from the fundamental dilemma between requiring effective interphase protection and high impedance from excessive growth of interphase. In this work, we designed and synthesized a “double EC” molecule as electrolyte additive to resolve the above dilemma. Erythritol bis(carbonate) (EBC) possesses lower LUMO energy level than EC and hence tends to decompose prior to EC reduction, but its weak solvation toward Li+ restricts the extent of its reduction, thus minimizing the interphase thickness and the corresponding impedances. Electrolytes containing EBC enables both the charging and discharging of ampere-size LIB pouch cells at sub-zero temperatures from 0 to -20℃, demonstrating that the key approach to improve low temperature performances lies in how to tailor interphasial chemistry rather than the bulk electrolyte composition.

The Zn3V3O8 was synthesized by solvothermal method combined with heat treatment using Zn(NO3)3 · 6H2O and NH4VO3 as raw materials. The Zn3V3O8 was doped by Co2+ to form Zn2.88Co0.12V3O8. The samples were characterized by X-ray diffraction and scanning electron microscopy techniques. Electrochemical tests showed that the initial discharge specific capacity for Zn2.88Co0.12V3O8 was 640.4 mAh·g−1 when the current density was 100 mA·g−1, which was higher than that of pure Zn3V3O8 (563.5 mAh · g−1). After 80 cycles, the discharge specific capacity of Zn2.88Co0.12V3O8 could maintain at 652.2 mAh · g−1, which was higher than that of pure Zn3V3O8 (566.8 mAh·g−1) under same condition. The Zn2.88Co0.12V3O8 owned better rate performances than those of pure Zn3V3O8 also. The related modification mechanisms were discussed in this paper

With the increasing awareness of global energy saving, the new energy storage devices represented by lithium-ion batteries (LIBs) have attracted more and more attention. The development of new materials of LIBs is crucial to the pursuit of energy efficiency and sustainable development. Polydopamine (PDA) is a synthetic analogue of natural melanin, which is synthesized by the oxidative polymerization of dopamine. Recently, polydopamine-based materials have received widespread research interest for electrochemical energy storage owing to their unique chemical structural versatility, electrochemical property, excellent adhesive property, etc. This review focuses on the representative examples of PDA-based materials applications in Li-ion battery materials (separator, current collector, active material, electrode, binder, solid electrolyte, and additive). The advantages and landmark achievements of PDA-based materials in the field of LIBs were summarized. The effect and mechanism of PDA-based materials on the electrochemical performance of the batteries are discussed in detail. Also, the outlook and future directions in this research field are also given. It is hoped to provide some useful information and reference for the research of PDA-based functional materials.

Anionic redox is an effective way to boost the energy density of layer-structured metal-oxide cathodes for rechargeable batteries. However, inherent rigid nature of the TMO6 (TM: transition metals) subunits in the layered materials makes it hardly tolerate the inner strains induced by lattice glide, especially at high voltage. Herein, P2-Na0.8 Mg0.13 [Mn0.6 Co0.2 Mg0.07 □0.13 ]O2 (□: TM vacancy) is designed that contains vacancies in TM sites, and Mg ions in both TM and sodium sites. Vacancies make the rigid TMO6 octahedron become more asymmetric and flexible. Low valence Co2+ /Co3+ redox couple stabilizes the electronic structure, especially at the charged state. Mg2+ in sodium sites can tune the interlayer spacing against O-O electrostatic repulsion. Time-resolved in situ X-ray diffraction confirms that irreversible structure evolution is effectively suppressed during deep desodiation benefiting from the specific configuration. X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations demonstrate that, deriving from the intrinsic vacancies, multiple local configurations of "□-O-□", "Na-O-□", "Mg-O-□" are superior in facilitating the oxygen redox for charge compensation than previously reported "Na-O-Mg". The resulted material delivers promising cycle stability and rate capability, with a long voltage plateau at 4.2 V contributed by oxygen, and can be well maintained even at high rates. The strategy will inspire new ideas in designing highly stable cathode materials with reversible anionic redox for sodium-ion batteries.

Aqueous Zn batteries promise high energy density but suffer from Zn dendritic growth and poor low-temperature performance. Here, we overcome both challenges by using an eutectic 7.6 m ZnCl2 aqueous electrolyte with 0.05 m SnCl2 additive, which in situ forms a zincophilic/zincophobic Sn/Zn5 (OH)8 Cl2 ⋅H2 O bilayer interphase and enables low temperature operation. Zincophilic Sn decreases Zn plating/stripping overpotential and promotes uniform Zn plating, while zincophobic Zn5 (OH)8 Cl2 ⋅H2 O top-layer suppresses Zn dendrite growth. The eutectic electrolyte has a high ionic conductivity of ≈0.8 mS cm-1 even at -70 °C due to the distortion of hydrogen bond network by solvated Zn2+ and Cl- . The eutectic electrolyte enables Zn∥Ti half-cell a high Coulombic efficiency (CE) of >99.7 % for 200 cycles and Zn∥Zn cell steady charge/discharge for 500 h with a low overpotential of 8 mV at 3 mA cm-2 . Practically, Zn∥VOPO4 batteries maintain >95 % capacity with a CE of >99.9 % for 200 cycles at -50 °C, and retain ≈30 % capacity at -70 °C of that at 20 °C.

Sulfurized polyacrylonitrile (SPAN) is a promising high-capacity cathode material. In this work, we use spatially resolved X-ray absorption spectroscopy combined with X-ray fluorescence (XRF) microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy to examine the structural transformation of SPAN and the critical role of a robust cathode-electrolyte interface (CEI) on the electrode. LiSx species forms during the cycling of SPAN. However, in carbonate-based electrolytes and ether-based electrolytes with LiNO3 additives, these species are well protected by the CEI and do not dissolve into the electrolytes. In contrast, in an ether-based electrolyte without the LiNO3 additive, LiSx species dissolve into the electrolyte, resulting in the shuttle effect and capacity loss. Examination of the Li anode by XRF and SEM reveals dense spherical Li morphology in ether-based electrolytes, but sulfur is present in the absence of the LiNO3 additive. In contrast, porous dendritic Li is found in the carbonate electrolyte. These analyses established that an ether-based electrolyte with LiNO3 is a superior choice that enables stable cycling of both electrodes. Based on these insights, we successfully demonstrate the stable cycling of high areal loading SPAN cathode (>6.5 mA h cm-2) with lean electrolyte amounts, showing promising Li∥SPAN cell performance under practical conditions.

Nowadays, commercial polypropylene (PP) and polyethylene separators in lithium-ion batteries (LIBs) still remain significant challenges of irreversible deformation, thermal shrinkage or even melting phenomena under external forces and high operating temperature, resulting in short circuit and thermal runaway of the LIBs. Herein, a kind of biphenyl polyimide (PI) nanofiber separator coated with SiO2 nanoparticles (SiO2–PI) is prepared via a simple and effective in situ dispersion method coupled with electrospinning technology and used as the separator of LIBs. The combination effect of the three-dimensional network and the extremely high porosity of 92% originating from the electrospinning technology as well as the well-dispersed SiO2 nanoparticles provides an ultrahigh mechanical flexibility, thermal stability, electrolyte wettability and ionic conductivity of the obtained SiO2–PI separator compared to the classical PP separator. These superior properties of the SiO2–PI separator endow the obtained LIBs with much enhanced electrochemical performances. For example, the initial specific discharge capacity of the SiO2–PI-based LIB is up to 158.4 mAh g−1 at 0.1 C and 125.7 mAh g−1 at 1 C, which can be retained at 90% after 100 cycles. These values, are much better than those of the PP-based LIB, i.e., 156.1 mAh g−1, 100.8 mAh g−1 and 76%, respectively.

A novel electrolyte system with an excellent low-temperature performance for lithium-ion batteries (LIBs) has been developed and studied. It was discovered for the first time, in this work, that when isoxazole (IZ) was used as the main solvent, the ionic conductivity of the electrolyte for LIBs is more than doubled in a temperature range between -20 and 20 °C compared to the baseline electrolyte using ethylene carbonate-ethyl methyl carbonate as solvents. To solve the problem of solvent co-intercalation into the graphite anode and/or electrolyte decomposition, the lithium difluoro(oxalato)borate (LiDFOB) salt and fluoroethylene carbonate (FEC) additive were used to form a stable solid electrolyte interphase on the surface of the graphite anode. Benefitting from the high ionic conductivity at low temperature, cells using a new electrolyte with 1 M LiDFOB in FEC/IZ (1:10, vol %) solvents demonstrated a very high reversible capacity of 187.5 mAh g-1 at -20 °C, while the baseline electrolyte only delivered a reversible capacity of 23.1 mAh g-1.

Metallic zinc is an ideal anode due to its high theoretical capacity (820 mAh g−1), low redox potential (−0.762 V versus the standard hydrogen electrode), high abundance and low toxicity. When used in aqueous electrolyte, it also brings intrinsic safety, but suffers from severe irreversibility. This is best exemplified by low coulombic efficiency, dendrite growth and water consumption. This is thought to be due to severe hydrogen evolution during zinc plating and stripping, hitherto making the in-situ formation of a solid–electrolyte interphase (SEI) impossible. Here, we report an aqueous zinc battery in which a dilute and acidic aqueous electrolyte with an alkylammonium salt additive assists the formation of a robust, Zn2+-conducting and waterproof SEI. The presence of this SEI enables excellent performance: dendrite-free zinc plating/stripping at 99.9% coulombic efficiency in a Ti||Zn asymmetric cell for 1,000 cycles; steady charge–discharge in a Zn||Zn symmetric cell for 6,000 cycles (6,000 h); and high energy densities (136 Wh kg−1 in a Zn||VOPO4 full battery with 88.7% retention for >6,000 cycles, 325 Wh kg−1 in a Zn||O2 full battery for >300 cycles and 218 Wh kg−1 in a Zn||MnO2 full battery with 88.5% retention for 1,000 cycles) using limited zinc. The SEI-forming electrolyte also allows the reversible operation of an anode-free pouch cell of Ti||ZnxVOPO4 at 100% depth of discharge for 100 cycles, thus establishing aqueous zinc batteries as viable cell systems for practical applications. A solid–electrolyte interphase that is permeable to Zn(ii) ions but waterproof is formed using an aqueous electrolyte composition. Cycling performances in an anode-free aqueous pouch cell show promise for intrinsically safe energy storage applications.

The development of phase change material (PCM) for battery thermal management poses key limitations on its reliability caused by leakage and shape deformation under high temperature. In this work, ...

Summary van der Waals layered metal chalcogenide Bi2Te3 has shown exceptional capacity and rate capability in alkali-ion batteries but the underlying reaction mechanism with Li+, Na+, and K+ remains undiscovered. It is unexpected that Na+ electrochemistry outperforms Li+ and K+ at high current densities. Here, in situ transmission electron microscopy is used to uncover nanoscale transformations during lithiation, sodiation, and potassiation, which follows two-step conversion and alloying reactions with Li+ and Na+, and three-step intercalation-conversion-alloying reactions with K+. Counterintuitively, sodiation exhibits the highest reaction kinetics, and its origin can be elucidated by first-principles and finite-element simulations in two aspects. The lower interfacial strain accommodation energy between Bi2Te3 and its Na-conversion products allows more facile sodiation phase transformation than Li- and K-ion reactions. The higher electrochemo-mechanical stress concentration at the concave-shaped sodiation reaction front facilitates continued Na-ion diffusion and reaction propagation. These fundamental insights are essential for fast-charging alkali-ion batteries.

Manganese-rich layered oxide materials hold great potential as low-cost and high-capacity cathodes for Na-ion batteries. However, they usually form a P2 phase and suffer from fast capacity fade. In this work, an O3 phase sodium cathode has been developed out of a Li and Mn-rich layered material by leveraging the creation of transition metal (TM) and oxygen vacancies and the electrochemical exchange of Na and Li. The Mn-rich layered cathode material remains primarily O3 phase during sodiation/desodiation and can have a full sodiation capacity of ca. 220 mAh g-1 . It delivers ca. 160 mAh g-1 specific capacity between 2-3.8 V with >86 % retention over 250 cycles. The TM and oxygen vacancies pre-formed in the sodiated material enables a reversible migration of TMs from the TM layer to the tetrahedral sites in the Na layer upon de-sodiation and sodiation. The migration creates metastable states, leading to increased kinetic barrier that prohibits a complete O3-P3 phase transition.

Summary Oxygen activity in highly delithiated LiCoO2 is critical to fully utilizing the energy density of this high-tap-density cathode but still lacks a clear understanding. In this work, we combined the results of several experimental techniques, especially resonant inelastic X-ray scattering (RIXS) and neutron pair distribution function (NPDF) analysis, together with theoretical calculations to study this topic. Our results conclude that oxygen redox takes place globally in the lattice, rather than forming localized dimerization as previously thought. RIXS results directly reveal the reversible oxygen redox, and NPDF results show that the O–O pair distance is considerably shortened in the highly delithiated LiCoO2. Theoretical calculations indicate that no O–O bonding is formed in LiCoO2, in sharp contrast to the lithium-rich system in which O–O bonding does form. These results provide the rationale for achieving a reversible deep delithiation and high energy density for LiCoO2-based electrodes.

A comprehensive understanding of the solid–electrolyte interphase (SEI) composition is crucial to developing high-energy batteries based on lithium metal anodes. A particularly contentious issue concerns the presence of LiH in the SEI. Here we report on the use of synchrotron-based X-ray diffraction and pair distribution function analysis to identify and differentiate two elusive components, LiH and LiF, in the SEI of lithium metal anodes. LiH is identified as a component of the SEI in high abundance, and the possibility of its misidentification as LiF in the literature is discussed. LiF in the SEI is found to have different structural features from LiF in the bulk phase, including a larger lattice parameter and a smaller grain size (

Owing to the abundance of raw material reserves and low cost, Na-ion batteries (NIBs) have successfully gained widespread attention from academic and industrial communities in the past few decades. However, the insufficient cathode energy density is still one of the critical bottlenecks restricting the development of NIBs. Following a strategy of inducing Li+ into the transition-metal (TM) layer to enhance the oxygen redox reaction, a novel layered cathode material P2-Na0.6Li0.11Fe0.27Mn0.62O2 (NLFMO) was designed and successfully synthesized. This NLFMO cathode not only delivers a large initial reversible capacity of 207.3 mAh g-1, but also showing a good cyclic performance (104.2 mAh g−1 after 80 cycles) and rate capability (126.2 mAh g−1 at 1C). The ultrahigh capacity is contributed by both cationic (Fe3+/Fe4+, Mn3+/Mn4+) and partially reversible anionic redox (O2-/On-) reactions, revealed by in situ X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) techniques. Moreover, no detrimental P2-O2 phase transition was observed through ex situ X-ray diffraction (XRD) patterns, confirming the high structural stability during Na+ deintercalation/intercalation processes. These results provide valuable information about the high-energy density layered cathode materials based on anionic redox reaction for NIBs.

Organic electrode materials have been considered as promising candidates for the next generation rechargeable battery systems due to their high theoretical capacity, versatility, and environmentally friendly nature. Among them, organosulfur compounds have been receiving more attention in conjunction with the development of lithium-sulfur batteries. Usually, organosulfide electrodes can deliver a relatively high theoretical capacity based on reversible breakage and formation of disulfide (S-S) bonds. In this review, we provide an overview of organosulfur materials for rechargeable lithium batteries, including their molecular structural design, structure related electrochemical performance study and electrochemical performance optimization. In addition, recent progress of advanced characterization techniques for investigation of the structure and lithium storage mechanism of organosulfur electrodes are elaborated. To further understand the perspective application, the additive effect of organosulfur compounds for lithium metal anodes, sulfur cathodes and high voltage inorganic cathode materials are reviewed with typical examples. Finally, some remaining challenges and perspectives of the organosulfur compounds as lithium battery components are also discussed. This review is intended to serve as general guidance for researchers to facilitate the development of organosulfur compounds.

It is highly desirable to realize high-energy-density lithium-ion batteries consisting of nickel-rich layered oxide cathodes (Ni-rich NMC) and Si-based anodes. A critical challenge for Ni-rich NMC ...

Recently, intrinsically conductive metal-organic frameworks (MOFs) have demonstrated promising performance in fast-charging energy storage applications and may outperform some current electrode materials (e.g., porous carbons) for supercapacitors in terms of both gravimetric and volumetric capacitance. In this report, we examine the mechanism of high capacitance in a nickel hexaaminobenzene-based MOF (NiHAB). Using a combination of in situ Raman and X-ray absorption spectroscopies, as well as detailed electrochemical studies in a series of aqueous electrolytes, we demonstrate that the charge storage mechanism is, in fact, a pH-dependent surface pseudocapacitance, and unlike typical inorganic systems, where transition metals change oxidation state during charge/discharge cycles, NiHAB redox activity is ligand-centered.

P2-type layered oxides suffer from an ordered Na+ /vacancy arrangement and P2→O2/OP4 phase transitions, leading them to exhibit multiple voltage plateaus upon Na+ extraction/insertion. The deficient sodium in the P2-type cathode easily induces the bad structural stability at deep desodiation states and limited reversible capacity during Na+ de/insertion. These drawbacks cause poor rate capability and fast capacity decay in most P2-type layered oxides. To address these challenges, a novel high sodium content (0.85) and plateau-free P2-type cathode-Na0.85 Li0.12 Ni0.22 Mn0.66 O2 (P2-NLNMO) was developed. The complete solid-solution reaction over a wide voltage range ensures both fast Na+ mobility (10-11 to 10-10 cm2 s-1 ) and small volume variation (1.7 %). The high sodium content P2-NLNMO exhibits a higher reversible capacity of 123.4 mA h g-1 , superior rate capability of 79.3 mA h g-1 at 20 C, and 85.4 % capacity retention after 500 cycles at 5 C. The sufficient Na and complete solid-solution reaction are critical to realizing high-performance P2-type cathodes for sodium-ion batteries.

Higher energy densities in rechargeable batteries can be achieved using thicker cathode films, though this is a challenging endeavor since the electrochemical performance of thick electrodes is sub...

Lithium sulfur batteries (LSBs) are promising next-generation rechargeable batteries due to the high gravimetric energy, low cost, abundance, nontoxicity, and high sustainability of sulfur. However, the dissolution of high-order polysulfide in electrolytes and low Coulombic efficiency of Li anode require excess electrolytes and Li metal, which significantly reduce the energy density of LSBs. Quasi-solid-state LSBs, where sulfur is encapsulated in the micropores of carbon matrix and sealed by solid electrolyte interphase, can operate under lean electrolyte conditions, but a low sulfur loading in carbon matrix (

Single-atom catalysts (SACs) show great promise for electrochemical CO2 reduction reaction (CRR), but the low density of active sites and the poor electrical conduction and mass transport of the single-atom electrode greatly limit their performance. Herein, we prepared a nickel single-atom electrode consisting of isolated, high-density and low-valent nickel(I) sites anchored on a self-standing N-doped carbon nanotube array with nickel-copper alloy encapsulation on a carbon-fiber paper. The combination of single-atom nickel(I) sites and self-standing array structure gives rise to an excellent electrocatalytic CO2 reduction performance. The introduction of copper tunes the d-band electron configuration and enhances the adsorption of hydrogen, which impedes the hydrogen evolution reaction. The single-nickel-atom electrode exhibits a specific current density of -32.87 mA cm-2 and turnover frequency of 1962 h-1 at a mild overpotential of 620 mV for CO formation with 97 % Faradic efficiency.

Summary The high reductivity of aluminum (Al) implies the utmost difficulty in achieving oxygen-resistant, ultrathin Al nanostructures. Herein, we demonstrate that sub-2-nm-thick Al nanosheets with ambient stability can be synthesized through a facile wet-chemical approach. Selective oxygen adsorption on the (111) facets of the face-centered cubic (fcc) Al has been revealed as the reason of controlling the morphology and stability of Al nanosheets, tailoring the thickness from 18 nm to 1.5 nm. Within the (111) surface passivation, Al nanosheets have achieved satisfactory stability, ensuring the possibility to study thickness-dependent localized surface plasmon resonance from visible to near-infrared (near-IR) region, and significantly enhanced two-photon luminescence. This work demonstrates, for the first time, the feasibility in obtaining stable ultrathin nanostructures of Al metal, which paves the way toward optical applications of Al as a sustainable plasmonic material, and shows great potential in the synthesis of other active metal-based nanomaterials.

Metal-organic framework cathodes usually exhibit low capacity and poor electrochemical performance for Li-ion storage owing to intrinsic low conductivity and inferior redox activity. Now a redox-active 2D copper-benzoquinoid (Cu-THQ) MOF has been synthesized by a simple solvothermal method. The abundant porosity and intrinsic redox character endow the 2D Cu-THQ MOF with promising electrochemical activity. Superior performance is achieved as a Li-ion battery cathode with a high reversible capacity (387 mA h g-1 ), large specific energy density (775 Wh kg-1 ), and good cycling stability. The reaction mechanism is unveiled by comprehensive spectroscopic techniques: a three-electron redox reaction per coordination unit and one-electron redox reaction per copper ion mechanism is demonstrated. This elucidatory understanding sheds new light on future rational design of high-performance MOF-based cathode materials for efficient energy storage and conversion.

Studies of transition metal dichalcogenides (TMDs) can be traced back to the 1970s but they have been abandoned for a while due to the fire hazard of lithium metal batteries. Herein, a new layered material, CrSSe, is reported, whose intercalative capacity can achieve 190 mA h g−1 with charges all compensated by anionic S and Se. Fascinating performances of half-cells are also presented, with a capacity retention rate of 81.5% upon 1000 cycles at 20C and a high output of 101.7 mA h g−1 even at 200C. In addition, an ideal way to build a type of full battery without lithium anodes for CrSSe is also displayed; a Li3N film was synthesized on the electrode surface as a lithium source. Overall, the discovery of CrSSe enriches the chemistry of TMDs and the application in full batteries opens up opportunities for enabling lithium-free cathodes to be widely utilized in practical applications.

The lithium–sulfur (Li–S) battery is a promising next-generation energy storage technology because of its high theoretical energy and low cost. Extensive research efforts have been made on new materials and advanced characterization techniques for mechanistic studies. However, it is uncertain how discoveries made on the material level apply to realistic batteries due to limited analysis and characterization of real high-energy cells, such as pouch cells. Evaluation of pouch cells (>1 A h) (instead of coin cells) that are scalable to practical cells provides a critical understanding of current limitations which enables the proposal of strategies and solutions for further performance improvement. Herein, we design and fabricate pouch cells over 300 W h kg−1, compare the cell parameters required for high-energy pouch cells, and investigate the reaction processes and their correlation to cell cycling behavior and failure mechanisms. Spatially resolved characterization techniques and fluid-flow simulation reveal the impacts of the liquid electrolyte diffusion within the pouch cells. We found that catastrophic failure of high-energy Li–S pouch cells results from uneven sulfur/polysulfide reactions and electrolyte depletion for the first tens of cycles, rather than sulfur dissolution as commonly reported in the literature. The uneven reaction stems from limited electrolyte diffusion through the porous channels into the central part of thick cathodes during cycling, which is amplified both across the sulfur electrodes and within the same electrode plane. A combination of strategies is suggested to increase sulfur utilization, improve nanoarchitectures for electrolyte diffusion and reduce consumption of the electrolytes and additives.

Controlled chemical prelithiation of high capacity phosphorous/carbon (P/C) composite anode has been applied to develop advanced lithium-ion batteries (LIBs). The initial coulombic efficiency (CE) of P/C is significantly improved (up to 93% for fully-prelithiated P/C) owing to the formation of an artificial solid electrolyte interface (SEI) layer, which is characterized by SEM, Raman and XPS analyses. It ensures the application of P/C anode in real battery assembly. A partly-prelithiated P/C anode prepared by 20 s prelithiation treatment is paired with a LiCoO2 (LCO) cathode. The full cell delivers a highly reversible capacity of ~104 mAh g−1LCO at 1C rate and retains a CE close to 100% over 2000 cycles. Moreover, a fully-prelithiated P/C anode prepared by 10 min prelithiation treatment is paired with a high-capacity Li-free sulfur/carbon (S/C) cathode. This newly configured full cell delivers a good rate and cycling performance and a high energy density of 358 Wh kg−1.

Despite being an advanced battery thermal management (BTM) strategy, the phase change material (PCM) cooling technology still suffers from the low thermal stability of the PCMs in practical applications, which leads to the leakage of the phase change ingredient, shape change or even collapse concerns under high temperature. Here we propose a creative idea for constructing a cross-linked polymeric structure with aliphatic side chains, namely, polymer PCM (PoPCM), through a facile one-step free-radical polymerization of octadecyl acrylate and crosslinkers. The aliphatic chains “tied up” on the cross-linked polymeric skeleton via “chemical bonding” and provided a high latent heat of 98.8 J g−1 without leakage, and therefore, delivered a stable solid–solid phase change behavior during long-term operation. The thermosetting 3-dimensional cross-linked structure simultaneously endowed the PoPCM with the anti-volume-expansion capability and excellent heat tolerance up to 250 °C without any deformation or leakage. When applied for BTM, the solid–solid PoPCM module demonstrated excellent and stable heat dissipation performance. The maximum temperature was 45.3 °C, and the temperature difference of the battery module could be controlled below 3.1 °C during the cyclic charge–discharge tests. Combining with the industrially available reagents and the simple preparation procedure at the kilogram level, we believe that this new strategy can present PCMs with superior feasibility for practical application in BTM.

Room-temperature sodium-ion batteries (SIBs) have attracted extensive interest in large-scale energy storage applications for renewable energy and smart grid, owing to abundant sodium resources and low cost. O3-layered sodium transition metal oxides (i.e., NaMO2, M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, etc.) are considered as a promising class of cathode materials for SIBs due to their high capacity and ease of synthesis. In this work, a quaternary layered material O3–NaCr1/4Fe1/4Ni1/4Ti1/4O2 (O3-NCFNT) is successfully synthesized and investigated as a new cathode material for SIBs. Within the voltage range of 1.5–4.1 V, O3-NCFNT delivers an ultrahigh charge capacity of 213 mA h g−1 but a limited discharge capacity of 107 mA h g−1 in the initial cycle. Ex situ X-ray diffraction and X-ray absorption spectroscopy results reveal that an irreversible phase transformation as well as the irreversible redox of Cr3+/Cr6+ within the voltage range of 1.5–4.1 V should be responsible for the capacity decay in the initial cycle. While, O3-NCFNT exhibits the initial charge/discharge capacities of 135.4 and 129.2 mA h g−1 with a high coulombic efficiency of 95.4% as well as good cyclic performance within the voltage range of 1.5–3.4 V at current rate of 0.1C. Especially, O3-NCFNT shows a capacity retention of 77.1% after 300 cycles at a high rate of 1C, indicating that the structural origins of capacity decay caused by excessive sodium extraction are confirmed by XRD and XAS measurements to unlock the potential of this material for sodium-ion battery application.

LiCoO2 is a dominant cathode material for lithium-ion (Li-ion) batteries due to its high volumetric energy density, which could potentially be further improved by charging to high voltages. However, practical adoption of high-voltage charging is hindered by LiCoO2’s structural instability at the deeply delithiated state and the associated safety concerns. Here, we achieve stable cycling of LiCoO2 at 4.6 V (versus Li/Li+) through trace Ti–Mg–Al co-doping. Using state-of-the-art synchrotron X-ray imaging and spectroscopic techniques, we report the incorporation of Mg and Al into the LiCoO2 lattice, which inhibits the undesired phase transition at voltages above 4.5 V. We also show that, even in trace amounts, Ti segregates significantly at grain boundaries and on the surface, modifying the microstructure of the particles while stabilizing the surface oxygen at high voltages. These dopants contribute through different mechanisms and synergistically promote the cycle stability of LiCoO2 at 4.6 V. LiCoO2 is a widely used cathode material in Li-ion batteries for applications such as portable electronics. Here, the authors report multiple-element doping to enable stable cycling of LiCoO2 at high voltages that are not yet accessible with commercial Li-ion batteries.

LiNi0.8Co0.15Al0.05O2 (NCA) has been proven to be a good cathode material for lithium-ion batteries (LIBs), especially in electric vehicle applications. However, further elevating energy density of...

Li metal anode has received extensive attention due to its high specific capacity and low potential vs. Li/Li+ for lithium batteries. However, dendrite growth, volume change and "dead" Li formation during cycling hinder its practical application. Here we report an innovated cuprite-coated carbon felt as current collector, with ultralight 3D framework and significantly improved Li-metal loading through thermal infusion. The Li-metal anode has a high Li content of 90 wt.%. The cuprite coating improves the lithiophilicity of carbon felt remarkably, due to the surface affinity reaction between cuprite and Li. The porous carbon felt provides good electronic connection and buffer space to accommodate volume change during Li stripping/plating. It leads to uniformly distributed local current density and preference of Li stripping/plating in the highly dispersed concave areas, with suppressed formation of dendrites and “dead” Li. The Li composite electrode shows excellent cycle stability with low polarization in both symmetric and full cells. This work opens a new approach for the development of high loading Li composite anodes for advanced Li metal batteries.

Sustainable water-splitting hydrogen production has long been considered one of the most promising energy conversion technologies, but enormous challenges remain: for instance, water electrolysis suffers from high overpotential and over energy consumption under neutral pH conditions. Here, taking advantage of the memory effect of layered double hydroxide (LDH), we report an energy-efficient neutral water electrolyzer material based on LDH with multiple vacancy defects. Benefiting from the improved electrical conductivity, larger electrochemical surface area (ECSA), and faster charge transfer, the NiFe LDH with O, Ni, and Fe vacancies exhibits a low overpotential of 87 mV at 10 mA/cm2 for hydrogen evolution reaction (HER) in a pH 7 buffer electrolyte. Impressively, the as-fabricated vacancy-containing NiFe LDH (v-NiFe LDH) splits water with a current density of 10 mA/cm2 at ∼1.60 V in a two-electrode device, outperforming most other water-splitting catalysts in neutral media. Such an electrolyzer setup cou...

Scanning electrochemical microscopy (SECM) was applied for in situ visualization of solid electrolyte interface (SEI) evolution on the TiO2 anode in a concentrated aqueous electrolyte during cyclin...

The large-voltage hysteresis remains one of the biggest barriers to optimizing Li/Na-ion cathodes using lattice anionic redox reaction, despite their very high energy density and relative low cost....

Summary The energy density of current Li-ion batteries is limited by the low capacity of intercalation cathode, which leaves relatively little room to further improve because the specific capacities of these cathodes approach the theoretical levels. Increasing the cell output voltage is a possible direction to largely increase the energy density of the batteries. Extensive research has been devoted to exploring >5.0 V cells, but only limited advances have been achieved because of the narrow electrochemical stability window of the electrolytes (

State-of-the-art lithium (Li)-ion batteries are approaching their specific energy limits yet are challenged by the ever-increasing demand of today’s energy storage and power applications, especially for electric vehicles. Li metal is considered an ultimate anode material for future high-energy rechargeable batteries when combined with existing or emerging high-capacity cathode materials. However, much current research focuses on the battery materials level, and there have been very few accounts of cell design principles. Here we discuss crucial conditions needed to achieve a specific energy higher than 350 Wh kg−1, up to 500 Wh kg−1, for rechargeable Li metal batteries using high-nickel-content lithium nickel manganese cobalt oxides as cathode materials. We also provide an analysis of key factors such as cathode loading, electrolyte amount and Li foil thickness that impact the cell-level cycle life. Furthermore, we identify several important strategies to reduce electrolyte-Li reaction, protect Li surfaces and stabilize anode architectures for long-cycling high-specific-energy cells. Jun Liu and Battery500 Consortium colleagues contemplate the way forward towards high-energy and long-cycling practical batteries.

A time-resolved operando X-ray absorption spectroscopy experiment was successfully designed to explore the sulfur reaction dynamics in lithium-sulfur (Li-S) batteries. It presents direct real-time experimental evidence for the distinct sulfur dynamics at different discharge rates, deepening the understanding of reaction mechanisms in Li-S batteries.

Polyimide (PI) membranes with superior chemical resistance, insulation and self-extinguishing are attracting numerous attentions as the separators of lithium-ion batteries (LIBs), but significant challenges of low mechanical strength and poor electrolyte affinity still remain. Herein, a new kind of environmentally friendly hydrogen-bond (H-bond) cross-linked cellulose/carboxylated PI (Cellulose/PI-COOH) nanofiber composite separator is prepared via electrospinning followed by imidization and alkaline hydrolysis. Besides inheriting the high porosity of the pristine PI separator to absorb the electrolyte, the three-dimensional interconnected structure resulting from H-bond cross-linking is beneficial to improving the mechanical properties of the composite separator, and thereby delivers a tensile strength of 34.2 MPa, 5 times higher than that of the pristine PI separator (6.8 MPa). Meanwhile, the exposed hydroxyl groups on the cellulose, and carboxyl and imino groups on the carboxylated PI can also enhance the electrolyte affinity and wettability of the Cellulose/PI-COOH separator, which plays an important role in increasing the ionic conductivity (0.51 mS cm−1) and widening the electrochemical stability window (∼5.1 V). Consequently, compared with the polypropylene separator and PI separator, the H-bond cross-linked Cellulose/PI-COOH separators show better cycle performance and rate performance when adopted in lithium iron phosphate (LiFePO4) and lithium cobaltate (LiCoO2) half-cells. For example, the Cellulose/PI-COOH-based LiFePO4 half-cell demonstrates the highest initial discharge capacity of 166.2 mAh g-1 and capacity retention rate of 90%, much higher than the pristine PI-based LiFePO4 half-cell (114.6 mAh g-1, 86%). Furthermore, the much enhanced tensile strength, flexibility, thermal stability and flame-resistance of the Cellulose/PI-COOH separator are believed to greatly enhance the safety performance of the obtained LIBs.

High-nickel content cathode materials offer high energy density. However, the structural and surface instability may cause poor capacity retention and thermal stability of them. To circumvent this problem, nickel concentration-gradient materials have been developed to enhance high-nickel content cathode materials’ thermal and cycling stability. Even though promising, the fundamental mechanism of the nickel concentration gradient’s stabilization effect remains elusive because it is inseparable from nickel’s valence gradient effect. To isolate nickel’s valence gradient effect and understand its fundamental stabilization mechanism, we design and synthesize a LiNi0.8Mn0.1Co0.1O2 material that is compositionally uniform and has a hierarchical valence gradient. The nickel valence gradient material shows superior cycling and thermal stability than the conventional one. The result suggests creating an oxidation state gradient that hides the more capacitive but less stable Ni3+ away from the secondary particle surfaces is a viable principle towards the optimization of high-nickel content cathode materials., High-nickel content cathode materials suffer issues of structural and surface instability. Herewith authors show that introduction of a nickel valence gradient enhances the thermal and cycle stability of high-nickel content cathode materials.

The hydrogen oxidation reaction (HOR) in alkaline media is critical for the alkaline fuel cell and electrochemical ammonia compressor. The sluggishness of HOR in the alkaline electrolyte requires platinum nano-catalysts, which are scarce and expensive. Decorating Pt catalysts with transition metals can boost the area specific activity (SA) of Pt nano-catalysts, but it often reduces the electrochemical active surface area (ECSA), resulting in a limited enhancement in Pt mass activity (MA). Single-atom surface modification of Pt catalysts can significantly enhance the reaction kinetics of single molecule, but it is less effective for HOR process that involve multiple molecules, i.e. H2 and OH-. Here we use a single-atom Pd-Ru pair to boost the activity of Pt nano-catalysts without loss of surface-active sites. Using a mildly catalytic thermal pyrolysis approach, single-Pd and single-Ru atom pair are precisely decorated on Pt nanoparticle surfaces, which is confirmed by Extended X-Ray Absorption Fine Structure (EXAFS) analysis. Density functional theory (DFT) calculations and ab-initio molecular dynamics (AIMD) simulations show the preferred adsorption of single-atom Pd and Ru dopants over Pd and Ru clustering on Pt surfaces. The single-atom Pd-Ru pair decorated Pt (Pd-Ru@Pt) catalyst features tri-active sites including: hydrophilic Pd promoting activation of adsorbed hydrogen atoms (Hads) via the hydrogen spill-over effect, oxyphilic Ru facilitating the adsorption of hydroxide molecules (OHads), and highly-catalytic Pt facilitating water formation with increased availability of Hads and OHads. In addition, the dopant decoration also reduces the hydrogen binding energy due to the shift of the (d) band center relative to the Fermi Level. The tri-active Pd-Ru@Pt catalyst shows 15.9 times higher area specific activity (SA) and 17.5 times larger mass activity (MA) than the state-of-the-art nano-Pt catalyst for HOR, and 2 times higher MA than nano-Pt for the hydrogen evolution reaction (HER). The mass exchange current density of single-atom Pd-Ru@Pt/C for the HOR/HER was 6.0 times that of the Pt/C, corresponding to 9.7 times that of Pd@Pt/C and 6.5 times that of Ru@Pt/C. The superior HOR/HER performance of the tri-active site catalyst is also demonstrated in ammonia and hydrogen pumps for practical application.

Majority existing organic composite phase change materials (CPCMs) are flammable that result in thermal hazards such as fire and explosions in battery modules. Furthermore, the performance of PCM-based battery modules in extreme conditions like thermal runaway has not been studied adequately. In this study, a tubular CPCM-cell structure is designed using physically flame-retardant-modified CPCMs, and a series of experiments on the CPCMs with/without real cells is conducted with calorimeter tests and SEM analysis on morphology structure. First, the calorimeter tests and comparison on the heat release rate (HRR) are conducted on the CPCMs with and without flame retardant additives. Results show that the addition of Al(OH)3 reduced the HRR from 242.5 to 204.4 kW/m2 with 15 wt% additives. Besides, the analysis of the mitigating performances of structure-enhanced tubular module and traditional cuboid module with real batteries is conducted. A factor of safety (FOS) parameter is defined to evaluate the safety degree of thermal runaway domino with energy density. The FOS of blank, CPCM–0C, and CPCM–15C modules are 0, 3.59, and 16.67, respectively, while that of CPCM-15T reaches 21.01, indicating a significant improvement on mitigating effects by structure enhancement compared to adding flame retardant additives. This study brings novelty in the design of PCM-based battery modules, particularly from the thermal safety prospect.

Flexible composite phase change materials (CPCMs) can minimize the thermal contact resistance in battery thermal management. However, these “thermally-induced” flexible CPCMs only present well-flexibility above the phase change temperature, which is unfavorable to the flexible assembly of the cells and battery modules with variable specifications. Herein, a kind of flexible CPCM with well-retained flexibility in a wide temperature range is prepared by carefully selecting a copolyester thermoplastic elastomer with polyether soft segment (TPC-et) to replace the conventional olefin block copolymer (OBC) skeleton. The internal rotation resistance of the ether bond in TPC-et is much lower than that of the C–C bond in OBC, thus giving rise to a better flexibility in room and low temperatures from 20 to −5 ℃. Combining the room-temperature-flexibility with the high thermal conductivity of 1.64 W m−1 K−1, enough latent heat of 102 J g−1 and suitable phase change region of 40–50 ℃, the obtained TPC-et based flexible CPCM shows outstanding applicability and cooling performance to various cells and battery modules through facile installations. The maximum temperature of the cylindrical, prismatic and pouch battery modules with TPC-et based CPCM is 51.5, 42.1 and 50.0 ℃, respectively, 4.0, 3.9 and 5.4 ℃ lower than the modules using rigid CPCM, respectively.

Sodium-ion batteries (SIBs) are attracting significant research attentions for large-scale energy storage applications. Cathode material is the vital part of SIBs to determine the capacity and cycle performance. Here, a series of F-doped Na0.66[Mn0.66Ti0.34]O2-xFx (x

To enhance the photocatalytic recycling capability of the TiO2-based photocatalysts, a new kind of plate-like In2O3/TiO2 nanotube array (TNA) hybrids is fabricated herein by constructing TNAs via an anodization method followed by doping In2O3 via a solvothermal method. The obtained In2O3/TNA hybrid demonstrates a well-aligned nanotubular structure with homogeneous dispersion of In2O3 nanoparticles. It shows a much higher degradation rate of 77% after 2 h compared to TNA (37%). In addition, the plate-like feature endows the photocatalysts with an excellent recycling capability. These superior photocatalytic degradation performances can be ascribed to the following factors: (1) the enhanced light absorption ability and efficient separation of photoexcited electron-hole pairs derived from the formation of the heterostructure between the interface of TiO2 and In2O3; (2) the efficient transport of reactant molecules provided by the well-defined TNAs and the homogeneous distribution of the In2O3 nanoparticles without blocking the nanotubes.

Lithium metal is considered to be the most promising anode for the next-generation lithium batteries. However, dendrite growth due to uneven Li plating during battery cycling leads to short circuit and safety hazards, as well as shorted cycling life for the battery, which is the vital obstacle for the practical application of Li metal anode in lithium batteries. We report a CoO nanofiber decorated Ni foam (CONF) skeleton used as a 3D conductive host to suppress the dendrite formation for composite Li anode (CONF-Li) fabricated by thermal infusion method. The uniformly distributed CoO nanofibers on the Ni foam can improve the lithiophilicity of Ni foam, and decrease the local current inhomogeneity of the anode, leading to a mild and uniform Li plating/stripping behavior which effectively suppresses the Li dendrite formation. As a result, the electrochemical performances of CONF-Li anode are significantly improved both in symmetric cells and full cells (lithium-sulfur and lithium-LiNi0.8Co0.15Al0.05O2 cells) proving its advancement over the pure Li anode.

The effect of H2 O in electrolytes and in electrode lattices on the thermodynamics and kinetics of reversible multivalent-ion intercalation chemistry based on a model platform of layered VOPO4 has been investigated. The presence of H2 O at the electrolyte/electrode interface plays a key role in assisting Zn2+ diffusion from electrolyte to the surface, while H2 O in the lattice structure alters the working potential. More importantly, a dynamic equilibrium between bulk electrode and electrolyte is eventually reached for H2 O transport during the charge/discharge cycles, with the water activity serving as the key parameter determining the direction of water movement and the cycling stability.

Lithium-ion battery (LIB) technology is the most attractive technology for energy storage systems in today’s market. However, further improvements and optimizations are still required to solve challenges such as energy density, cycle life, and safety. Addressing these challenges in LIBs requires a fundamental understanding of the reaction mechanisms in various physical/chemical processes during LIB operation. Advanced in situ/operando synchrotron-based X-ray characterization techniques are powerful tools for providing valuable information about the complicated reaction mechanisms in LIBs. In this review, several state-of-the-art in situ/operando synchrotron-based X-ray techniques and their combination with other characterization tools for battery research are introduced. Various in situ cell configurations and practical operating tips for cell design and experimental set-ups are also discussed. The mechanisms that shorten lithium-ion battery lifetimes and cause safety issues can be identified using advanced x-ray light source at National Synchrotron Light Source II. Xiao-Qing Yang from Brookhaven National Laboratory in the USA and Xiqian Yu at the Chinese Academy of Science in Beijing review efforts to look inside working batteries using synchrotron-generated X-rays with a specially designed in situ cell. These experiments can record the changes of lithium battery electrodes, such as the evolution of structures as the battery during charge-discharge by x-ray diffraction (XRD) and the complementary techniques including X-ray absorption spectroscopy, which can pinpoint the individual element responsible for improving the battery’s performance and lifetime. Testing battery with different electrochemical history can be removed and re-inserted into the synchrotron beam to track individual nanostructures as the battery cycles and ages. Advanced in situ/operando synchrotron based X-ray characterization techniques are powerful tools in providing valuable information about the complicate reaction mechanisms in lithium-ion batteries. In this review, the state-of-the-art of in situ/operando synchrotron-based X-ray techniques and their combination for battery research are introduced. Various types of in situ cell designs and practical operation tips for experimental set ups are also discussed.

Summary Lithium-ion batteries with high energy density are being intensively pursued to meet the ever-growing demand for energy storage. However, the increase in energy density often comes with an elevated instability of electrode materials, causing major concerns about the reliability and safety of lithium-ion batteries. Here, we report a strategy for stabilizing cathode materials by modulating the vacant lattice sites on the particle surface. Using the high-voltage Li[Ni0.5Mn1.5]O4 as an example, we demonstrate that introduction of a 10-nm epitaxial surface layer with Al3+ in the empty 16c octahedral sites of the spinel Li[Ni0.5Mn1.5]O4 suppresses structural degradation during cycling by increasing the surface stability without interfering with the Li+ diffusion around the Al3+ sites. Control of the Al3+ concentration in the surface region was shown to be a facile process. The process was shown to stabilize long-term cycling of Li[Ni0.5Mn1.5]O4 to 5 V versus Li+/Li0.