Ion Insertion Research Articles

Tunnel‐Type Na2Ti6O13@Carbon Nanowires as Anode Materials for Low‐Temperature Sodium‐Ion Batteries

AbstractEconomical efficient anode materials play an important role in low‐temperature sodium‐ion batteries (SIBs). Tunnel‐type structured Na2Ti6O13@C nanowires were synthesized and utilized as anode material for low‐temperature SIBs. The appropriate interlayer spacing for sodium ion insertion and short diffusion pathway can accelerate the sodium ion kinetics and decrease the apparent activation energy at low temperature. The diffusion apparent activation energy and activation energy for Na2Ti6O13@C were calculated to be 42.0 kJ mol−1 and 15.3 kJ mol−1 with the sodium ion diffusion coefficients about 10−12 cm2 s−1. The Na2Ti6O13@C nanowires exhibit a high reversible capacity of 100 mAh g−1 at 0 °C with 99.6 % retention after 200 cycles at 0.5 C. Coupling with the sodium vanadium phosphate as cathode, the assembled Na2Ti6O13@C||NVP full‐cell can keep a 65 % capacity retention after 175 cycles at 0 °C. This work presents that Na2Ti6O13@C nanowires can be an ideal type of anode active materials for low‐temperature SIBs.

Electrochromic Electrodes with Enhanced Performance: Review of Morphology and Ion Transport Mechanism Modifications

The electrochromic (EC) performance of smart windows is highly dependent on the rate of ions insertion/extraction. A direct way to increase the ion exchange in EC device is to modify the structure of the EC electrodes. Structural changes also affect the electrical conduction between the transparent electrodes and the EC layers, leading to efficient smart windows. In more detail, modifying the structure of the EC electrodes results in an increase in the surface-to-volume ratio, which is combined with the increase in charge transfer reaction between the insertion and extraction of ions. The current review summarizes the enhancement in the EC performance due to the fabrication of nano/microstructures or hybrid structures on the surface of the EC electrodes to increase their surface area. Moreover, metal oxide thin films have poor electrical conduction, which leads to a high charge transport barrier. Accordingly, improving the electrical conductivity of the EC layer is considered another effective strategy to enhance the ion transport between the transparent conductor layer and the EC electrode. This behavior could be applied by combining the transition metal oxide with metallic nanoparticles or suitable organic/inorganic transparent conducting materials.

NH4 + Deprotonation at Interfaces Induced Reversible H3 O+ /NH4 + Co-insertion/Extraction.

Ion insertions always involve electrode-electrolyte interface process, desolvation for instance, which determines the electrochemical kinetics. However, it's still a challenge to achieve fast ion insertion and investigate ion transformation at interface. Herein, the interface deprotonation of NH4 + and the introduced dissociation of H2 O molecules to provide sufficient H3 O+ to insert into materials' structure for fast energy storages are revealed. Lewis acidic ion-NH4 + can, on one hand provide H3 O+ itself via deprotonation, and on the other hand hydrolyze with H2 O molecules to produce H3 O+ . In situ attenuated total reflection-Fourier transform infrared ray method probed the interface accumulation and deprotonation of NH4 + , and density functional theory calculations manifested that NH4 + tend to thermodynamically adsorb on the surface of monoclinic VO2 , and deprotonate to provide H3 O+ . In addition, the inserted NH4 + has a positive effect for stabilizing the VO2 (B) structure. Therefore, high specific capacity (>300 mAh g-1 ) and fast ionic insertion/extraction (<20 s) can be realized in VO2 (B) anode. This interface derivation proposes a new path for designing proton ion insertion/extraction in mild electrolyte.

NH4+ Deprotonation at Interfaces Induced Reversible H3O+/NH4+ Co‐insertion/Extraction

AbstractIon insertions always involve electrode‐electrolyte interface process, desolvation for instance, which determines the electrochemical kinetics. However, it′s still a challenge to achieve fast ion insertion and investigate ion transformation at interface. Herein, the interface deprotonation of NH4+ and the introduced dissociation of H2O molecules to provide sufficient H3O+ to insert into materials′ structure for fast energy storages are revealed. Lewis acidic ion‐NH4+ can, on one hand provide H3O+ itself via deprotonation, and on the other hand hydrolyze with H2O molecules to produce H3O+. In situ attenuated total reflection‐Fourier transform infrared ray method probed the interface accumulation and deprotonation of NH4+, and density functional theory calculations manifested that NH4+ tend to thermodynamically adsorb on the surface of monoclinic VO2, and deprotonate to provide H3O+. In addition, the inserted NH4+ has a positive effect for stabilizing the VO2(B) structure. Therefore, high specific capacity (&gt;300 mAh g−1) and fast ionic insertion/extraction (&lt;20 s) can be realized in VO2(B) anode. This interface derivation proposes a new path for designing proton ion insertion/extraction in mild electrolyte.

Ion Co-storage in Porous Organic Frameworks through On-site Coulomb Interactions for High Energy and Power Density Batteries.

Fast and continuous ion insertion is blocked in the common electrodes operating with widely accepted single-ion storage mechanism, primarily due to Coulomb repulsion between the same ions. It results in an irreconcilable conflict between capacity and rate performance. Herein, we designed a porous organic framework with novel multiple-ion co-storage modes, including PF6 - /Li+ , OTF- /Mg2+ , and OTF- /Zn2+ co-storage. The Coulomb interactions between cationic and anionic carriers in the framework can significantly promote electrode kinetics, by rejuvenating fast ion carrier migration toward framework interior. Consequently, the framework via PF6 - /Li+ co-storage mode shows a high energy density of 878 Wh kg-1 cycled more than 20 000 cycles, with an excellent power density of 28 kW kg-1 that is already comparable to commercial supercapacitors. The both greatly improved energy and power densities via the co-storage mode may pave a way for exploring new electrodes that are not available from common single-ion electrodes.

Ion Co‐storage in Porous Organic Frameworks through On‐site Coulomb Interactions for High Energy and Power Density Batteries

AbstractFast and continuous ion insertion is blocked in the common electrodes operating with widely accepted single‐ion storage mechanism, primarily due to Coulomb repulsion between the same ions. It results in an irreconcilable conflict between capacity and rate performance. Herein, we designed a porous organic framework with novel multiple‐ion co‐storage modes, including PF6−/Li+, OTF−/Mg2+, and OTF−/Zn2+ co‐storage. The Coulomb interactions between cationic and anionic carriers in the framework can significantly promote electrode kinetics, by rejuvenating fast ion carrier migration toward framework interior. Consequently, the framework via PF6−/Li+ co‐storage mode shows a high energy density of 878 Wh kg−1 cycled more than 20 000 cycles, with an excellent power density of 28 kW kg−1 that is already comparable to commercial supercapacitors. The both greatly improved energy and power densities via the co‐storage mode may pave a way for exploring new electrodes that are not available from common single‐ion electrodes.

Solvothermal Engineering of NaTi2(PO4)3 Nanomorphology for Applications in Aqueous Na-Ion Batteries.

Aqueous Na-ion batteries are among the most discussed alternatives to the currently dominating Li-ion battery technology, in the area of stationary storage systems because of their sustainability, safety, stability, and environmental friendliness. The electrochemical properties such as ion insertion kinetics, practical capacity, cycling stability, or Coulombic efficiency are strongly dependent on the structure, morphology, and purity of an electrode material. The selection and optimization of materials synthesis route in many cases allows researchers to engineer materials with desired properties. In this work, we present a comprehensive study on size- and shape-controlled hydro(solvo)thermal synthesis of NaTi2(PO4)3 nanoparticles. The effects of different alcohol/water synthesis media on nanoparticle phase purity, morphology, and size distribution are analyzed. Water activity in the synthesis media of different alcohol solutions is identified as the key parameter governing the nanoparticle phase purity, size, and shape. The careful engineering of NaTi2(PO4)3 nanoparticle morphology allows control of the electrochemical performance and degradation of these materials as aqueous Na-ion battery electrodes.

High Mass Loading of Flowerlike Ni-MoS2 Microspheres toward Efficient Intercalation Pseudocapacitive Electrodes

This work reports the exploration of intercalation pseudocapacitance in a thicker electrode of flowerlike Ni-doped MoS2 microspheres that features a mass loading of ∼10 mg/cm2 without sacrificing the gravimetric capacitance (∼425 F/g at 5 mV/s). Integration of Ni atoms into MoS2 microspheres not only stabilized the structural integrity but also ameliorated the rapid intercalation and deintercalation of electrolyte ions even at a commercial-level mass loading. The energy instability by Ni doping significantly changed the local bonding behavior and the overall electronic structure of MoS2, facilitating the breaking of the MoS2 layer and generation of more active edge sites, which are responsible for faster reaction kinetics. The experiments attribute the overall capacitance enhancement in (Mo-Ni)S2 to the increased rate of electrolyte ion insertion and extraction, which is confirmed by b-values close to 0.5, at different potentials, indicating that the current response predominantly depends on the diffusive mechanism for both MoS2 and Ni-MoS2 thicker electrodes. The symmetric device constructed with Ni-MoS2 microspheres exhibited a capacitance value of 101 F/g in 1 mV/s, for which the energy density is 9 Wh/kg, as well as attained an outstanding cycling stability of 10 000 cycles with 60% retention at 2 A/g. In addition to providing insights into the development of 2D TMDs, this work explores the design of robust and highly efficient intercalation electrode material for electrochemical energy storage devices.

Molecularly Hybridized Conduction in DPP-Based Donor-Acceptor Copolymers toward High-Performance Iono-Electronics.

Iono-electronics, that is, transducing devices able to translate ionic injection into electrical output, continue to demand a variety of mixed ionic-electronic conductors (MIECs). Though polar sidechains are widely used in designing novel polymer MIECs, it remains unclear to chemists how much balance is needed between the two antagonistic modes of transport (ion permeability and electronic charge transport) to yield high-performance materials. Here, the impact of molecularly hybridizing ion permeability and charge mobility in semiconducting polymers on their performance in electrochemical and synaptic transistors is investigated. A series of diketopyrrolopyrrole (DPP)-based copolymers are employed to demonstrate the multifunctionality attained by controlling the density of polar sidechains along the backbone. Notably, efficient electrochemical signal transduction and reliable synaptic plasticity are demonstrated via controlled ion insertion and retention. The newly designed DPP-based copolymers further demonstrate unprecedented thermal tolerance among organic mixed ionic-electronic conductors, a key property in the manufacturing of organic electronics.

Hexagonal Carbon Nanoplates Decorated with Layer-Engineered MoS2: High-Performance Cathode Materials for Zinc-Ion Batteries.

Hexagonal carbon nanoplates bearing MoS2 (HCN@MoS2) were synthesized using two-dimensional (2D) microporous organic polymers as templating materials. The layer number of MoS2 in HCN@MoS2 and the 2D morphology of composites were critical factors to achieve high-performance cathode materials for aqueous zinc-ion batteries. The best cathode performance was obtained with HCN@MoS2 bearing 2-3 layered MoS2 (HCN@MoS2-2), showing excellent discharge capacities of 602 mAh/g (@50 mA/g), 498 mAh/g (@0.1 A/g), and 328 mAh/g (@1 A/g). The promising electrochemical performance of HCN@MoS2-2 is attributable to the facilitated insertion of zinc ions into 2-3 layered MoS2 due to the reduced lattice energy and the efficient electrochemical utilization of composite materials.

Lithium exchange across a lithium-less coating for high energy cathodes

Surface degradation is a major limitation in the utilization of high energy cathodes. Cathode coatings provide a promising route for achieving interfacial stability. In this case, there is interest in developing coatings which will provide efficient ion transport across the cathode-electrolyte-interface (CEI). Aluminum based coatings, particularly metal fluorides, have shown great promise for stabilizing the high voltage cathode, LiNi0.5Mn1.5O4. Despite the clear practical advantages of coatings, the chemical basis for their improved performance remains ambiguous. Here we present an in-depth investigation of a nominal AlF3 coating on LiNi0.5Mn1.5O4 based on solid state NMR spectroscopy to determine the composition and function of the Al/F coating layer. NMR results, supported by X-ray photoelectron spectroscopy and electron microscopy, reveal that the actual composition of the deposited layer is an amorphous Al–O–F phase. Isotope exchange is used to follow the spontaneous exchange of lithium ions across the CEI, revealing improved transport in coated cathodes. Finally, NMR experiments provide evidence for insertion of lithium ions in the Al/F coating following electrochemical cycling. The results suggest that lithium insertion into a nominally lithium-less coating plays a role in its improved performance, highlighting lithium content as an important factor in designing beneficial coatings for higher energy cathodes.

Selectivity of Oxygen Evolution Reaction on Carbon Cloth-Supported δ-MnO2 Nanosheets in Electrolysis of Real Seawater.

Electrolysis of seawater using solar and wind energy is a promising technology for hydrogen production which is not affected by the shortage of freshwater resources. However, the competition of chlorine evolution reactions and oxygen evolution reactions on the anode is a major obstacle in the upscaling of seawater electrolyzers for hydrogen production and energy storage, which require chlorine-inhibited oxygen evolution electrodes to become commercially viable. In this study, such an electrode was prepared by growing δ-MnO2 nanosheet arrays on the carbon cloth surface. The selectivity of the newly prepared anode towards the oxygen evolution reaction (OER) was 66.3% after 30 min of electrolyzer operation. The insertion of Fe, Co and Ni ions into MnO2 nanosheets resulted in an increased number of trivalent Mn atoms, which had a negative effect on the OER selectivity. Good tolerance of MnO2/CC electrodes to chlorine evolution in seawater electrolysis indicates its suitability for upscaling this important energy conversion and storage technology.

Self-Adaptive Re-Organization Enables Polythiophene as an Extraordinary Cathode Material for Aluminum-Ion Batteries with a Cycle Life of 100 000 Cycles.

Aluminum-ion batteries (AIBs) have attracted great attentions in recent years. Organic materials such as polythiophene (PT) are promising cathode for AIBs. However, the capacity and cyclic stability of conventional organic cathode such as PT are limited by the inadequate degree of reaction and the unstable nature of organic materials. To obtain high-performance organic cathode, a new PT with the ability of self-adaptive re-organization was prepared. During cycling, its molecular chain can be re-organized, and the polymerization mode will change from Cα -Cα (α-PT) to Cβ -Cβ (β-PT). This change leads to smaller steric hindrance and faster kinetics during ion insertion which can lower the reaction energy barrier and stabilize the molecular structure. Benefited by this, AIBs with this cathode can deliver a specific capacity of 180 mAh g-1 (@2 A g-1 ) and a superb stability of 100 000 cycles at 10 A g-1 . High energy density and power density can also be achieved with this cathode.

Self‐Adaptive Re‐Organization Enables Polythiophene as an Extraordinary Cathode Material for Aluminum‐Ion Batteries with a Cycle Life of 100 000 Cycles

AbstractAluminum‐ion batteries (AIBs) have attracted great attentions in recent years. Organic materials such as polythiophene (PT) are promising cathode for AIBs. However, the capacity and cyclic stability of conventional organic cathode such as PT are limited by the inadequate degree of reaction and the unstable nature of organic materials. To obtain high‐performance organic cathode, a new PT with the ability of self‐adaptive re‐organization was prepared. During cycling, its molecular chain can be re‐organized, and the polymerization mode will change from Cα−Cα(α‐PT) to Cβ−Cβ(β‐PT). This change leads to smaller steric hindrance and faster kinetics during ion insertion which can lower the reaction energy barrier and stabilize the molecular structure. Benefited by this, AIBs with this cathode can deliver a specific capacity of 180 mAh g−1(@2 A g−1) and a superb stability of 100 000 cycles at 10 A g−1. High energy density and power density can also be achieved with this cathode.

Elucidation of the Charging Mechanisms and the Coupled Structural–Mechanical Behavior of Ti3C2Tx (MXenes) Electrodes by In Situ Techniques

AbstractThe discovery of the Ti3C2Tx compounds (MXenes) a decade ago opened new research directions and valuable opportunities for high‐rate energy storage applications. The unique ability of the MXenes to host various mono‐ and multivalent cations and their high stability in different electrolyte environments including aqueous, organic, and ionic liquid solutions, promoted the rapid development of advanced MXene‐based electrodes for a large variety of applications. Unlike the vast majority of typical intercalation compounds, the electrochemical performance of MXene electrodes is strongly influenced by the presence of co‐inserted solvent molecules, which cannot be detected by conventional current/potential electrochemical measurements. Furthermore, the electrochemical insertion of ions into MXene interspaces results in strong coupling with the intercalation‐induced structural, dimensional, and viscoelastic changes in the polarized MXene electrodes. To shed light on the charging mechanisms of MXene systems and their associated phenomena, the use of a large variety of real‐time monitoring techniques has been proposed in recent years. This review summarizes the most essential findings related to the charging mechanism of Ti3C2Tx electrodes and their potential induced structural and mechanical phenomena obtained by in situ investigations.

Aqueous electrolyte-mediated reversible K+ ion insertion into graphite.

Herein, reversible K+ ion insertion into graphite in an aqueous electrolyte is illustrated. It is shown that more facile diffusion of K+ ions is possible in natural graphite than in pyrolytic graphite.

Mechanical characterization and modelling of lithium-ion batteries

Mechanical phenomena in lithium-ion batteries are one of the main sources of damage, as well as an indicator of battery health and charge. Then, a deep study of these phenomena may improve battery life, management and safety. Mechanical phenomena are caused by the insertion of lithium ions in the microstructure of the electrodes and can be divided into two main categories: stress and degradation of the electrode microstructure, and battery volume change. The stress and fracture behaviour of the electrode microstructure due to lithium intercalation are studied with an electrochemical-mechanical model. Stress intensity factor is computed to assess how current rate and the geometry of the electrode microstructure affect fracture and may reduce the battery life. In addition to stress in the microstructure, lithium insertion causes the swelling of the entire battery. Then, the thickness change of batteries with different chemistries is measured. These measurements carry important information on the battery states and represent an alternative to voltage to extrapolate charge and health states.

Investigation of reversible metal ion (Li+, Na+, Mg2+, Al3+) insertion in MoTe2 for rechargeable aqueous batteries.

In this work, we report the electrochemical reactivity of MoTe2 for various metal ions with special emphasis on Al3+ ion storage in aqueous electrolytes for the first time. A stable discharge capacity of 100 mA h g-1 over 250 cycles at a current density of 1 Ag-1 could be obtained for the Al3+ ion, whereas inferior storage capacities were shown for other metal ions.

Molten salt-assisted synthesis of bismuth nanosheets with long-term cyclability at high rates for sodium-ion batteries.

Bismuth is a promising anode material for sodium-ion batteries (SIBs) due to its high capacity and suitable working potential. However, the large volume change during alloying/dealloying would lead to poor cycling performance. Herein, we have constructed a 3D hierarchical structure assembled by bismuth nanosheets, addressing the challenges of fast kinetics, and providing efficient stress and strain relief room. The uniform bismuth nanosheets are prepared via a molten salt-assisted aluminum thermal reduction method. Compared with the commercial bismuth powder, the bismuth nanosheets present a larger specific surface area and interlayer spacing, which is beneficial for sodium ion insertion and release. As a result, the bismuth nanosheet anode presents excellent sodium storage properties with an ultralong cycle life of 6500 cycles at a high current density of 10 A g-1, and an excellent capacity retention of 87% at an ultrahigh current rate of 30 A g-1. Moreover, the full SIBs that paired with the Na3V2(PO4)3/rGO cathode exhibited excellent performance. This work not only presents a novel strategy for preparing bismuth nanosheets with significantly increased interlayer spacing but also offers a straightforward synthesis method utilizing low-cost precursors. Furthermore, the outstanding performance demonstrated by these nanosheets indicates their potential for various practical applications.

Optimized crystal orientation for enhanced reaction kinetics and reversibility of SnSe/NC hollow nanospheres towards high-rate and long-term lithium/sodium storage.

The development of anode materials with high theoretical capacity and cycling stability is very important for the electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, SnSe/NC hollow nanospheres with different crystal orientations were prepared by regulating the high-temperature selenization of the PDA@SnO2 precursor for lithium/sodium storage. In SnSe/NC hollow nanospheres, the physical buffering and chemical bonding of the nitrogen carbon matrix and SnSe nanoparticles could inhibit volume expansion and polyselenide loss, thus maintaining long-term structural stability. More importantly, electrochemical tests and DFT calculations show that the diffusion energy barrier of Li+/Na+ is significantly reduced at the SnSe (400) rather than the usual (111) facet, which is conducive to the uniformity of ion insertion into SnSe, thus effectively enhancing the reaction kinetics and reversibility of lithium/sodium storage. Therefore, SnSe/NC hollow nanospheres with rich SnSe (400) and good dispersion formed at 550 °C delivered the best reversible specific capacity and rate performance. After a long period of 900 cycles, the capacity retention of lithium/sodium ion batteries is close to 84.88% and 77.05%, respectively. Our findings provide valuable insights into the design of metal selenides for advanced LIBs/SIBs.