Conductive Binder Research Articles

Lattice-matched Cu3P/Cu2Se heterojunction catalysts for efficient hydrogen evolution reactions

The research and development of efficient electrocatalysts for the hydrogen evolution reaction (HER) are indispensable for the large-scale popularization of hydrogen energy. As most existing electrocatalysts are powder materials, many conductive agents and binders are required for electrocatalytic performance test. Besides the tedious the preparation process of the electrode, the long-term cycle stability of the electrode is also low. In this study, Cu(OH)2 precursors were prepared on copper foam by anodic oxidation. Subsequently, lattice-matched Cu3P/Cu2Se heterojunction catalysts were obtained via simultaneous phosphorization and selenization. The results showed that the synergistic effect of the two phases and heterogeneous interface significantly improved the electrochemical HER performance. The overpotential of the lattice-matched Cu3P/Cu2Se catalyst was only 166 mV and the Tafel slope was 187.90 mV dec−1 at 10 mA cm−2. After testing for 10 h at 10 mA cm−2, the overpotential stabilized at 250 mV. The overpotential of the lattice-matched Cu3P/Cu2Se was lower than that of the individual Cu3P and Cu2Se catalysts. Thus, synergism between the heterostructure and interface is an effective approach for enhancing the electrocatalytic activity and durability. It was proved that element doping and constructing defects are feasible strategies to improve the electrocatalytic performance of catalysts.

Cellulose sulfate lithium as a conductive binder for LiFePO4 cathode with long cycle life

Polysaccharides can be potential binders for lithium-ion batteries due to their strong adhesion through numerous hydroxyl groups. As a novel waterborne lithiated polysaccharide derivative, cellulose sulfate lithium (CSL) is successfully synthesized and used as the binder for LiFePO4 (LFP) cathode. The chemical structure of CSL is verified by FTIR-ATR, XRD, C13-NMR, GPC, EA, ICP and TGA. Compared to LFP cathode using polyvinylidene difluoride binder, electrochemical measurements show that the LFP cathode using CSL (LFP-CSL) has lower polarization and better rate performance owing to higher lithium-ion conductivity of CSL. The result of morphological analysis indicates that CSL binder can maintain an integrated LFP cathode structure during hundreds of cycles. As a result, the LFP-CSL cathode exhibits a discharge capacity of 133.4 mAh g−1 and maintains remarkable cycle stability with retention of 93.1 % after 300 cycles at 1C. These findings provide novel insights into the rational design of the binders for the LFP cathode.

N-Type Polyoxadiazole Conductive Polymer Binders Derived High-Performance Silicon Anodes Enabled by Crosslinking Metal Cations.

The dilemma of employing high-capacity battery materials and maintaining the electrodes' electrical and mechanical integrity requires a unique binder system design. Polyoxadiazole (POD) is an n-type conductive polymer with excellent electronic and ionic conductive properties, which has acted as a silicon binder to achieve high specific capacity and rate performance. However, due to its linear structure, it cannot effectively alleviate the enormous volume change of silicon during the process of lithiation/delithiation, resulting in poor cycle stability. This paper systematically studied metal ion (i.e., Li+, Na+, Mg2+, Ca2+, and Sr2+)-crosslinked PODs as silicon anode binders. The results show that the ionic radius and valence state remarkably influence the polymer's mechanical properties and the electrolyte's infiltration. Electrochemical methods have thoroughly explored the effects of different ion crosslinks on the ionic and electronic conductivity of POD in the intrinsic and n-doped states. Attributed to the excellent mechanical strength and good elasticity, Ca-POD can better maintain the overall integrity of the electrode structure and conductive network, significantly improving the cycling stability of the silicon anode. The cell with such binders still retains a capacity of 1770.1 mA h g-1 after 100 cycles at 0.2 C, which is ∼285% that of the cell with the PAALi binder (620.6 mA h g-1). This novel strategy using metal-ion crosslinking polymer binders and the unique experimental design provides a new pathway of high-performance binders for next-generation rechargeable batteries.

High‐Energy‐Density Graphene Hybrid Flexible Fiber Supercapacitors

AbstractGraphene fiber‐based supercapacitors (GFSCs) as flexible energy‐storage devices have achieved much in the wearable electronics. However, the GFSCs still suffer insufficient energy density, and of which desirable balance between mechanical and electrochemical properties has not been realized. Herein, we developed AgI and conductive polymer assisted co‐enhancement strategy to prepare the high‐performance GFSCs with super‐high energy density, favorable mechanical properties, and superior electrochemical properties. The conductive binder polymer, poly(3,4‐ethylenedioxythiophene) (PEDOT) was introduced into the GO spinning solution to enhance RGO fiber strength, conductivity, and electrochemical performance by forming a strong interface with GO in the spinning solution. On the other hand, the synergistic effect of micro‐ and nano‐scale AgI grown on the fiber surface and aqueous gel electrolyte widen the potential window of the GFSC to 1.6 V, which is much higher than that of reported GFSCs, and resulting in a significantly increased energy density. At 0.1 A cm−3, the volumetric capacitance and energy density of the fabricated GFSCs are as high as 166.6 F cm−3 and 29.65 mWh cm−3, respectively. The high strength and flexibility of the hybrid fibers endowed the GFSCs with ∼100 % capacitance retention when bent to 180°. This work opens a new way to design and fabricate high‐performance GFSCs.

Local Structural Analysis of Sulfide Polymer Electrolytes Prepared via I2-Induced Polymerization of Li3PS4

To avoid the volume change associated with the electrode active material during charge/discharge in all-solid-state batteries, an effective binder that improves the contact between the solid electrolyte and the electrode active material must be developed. To this aim, the polymerization of the sulfide solid electrolyte Li3PS4 offers a promising route. However, the local structure of the resulting solid electrolyte, i.e., a mixture of LiI crystals and glassy sulfide polymers, needs to be elucidated for further development of sulfide polymers as binders. Herein, we analyze the local structure of the isolated mixture via a differential pair distribution function analysis using X-ray total scattering. The presence of disulfide bonds between PS4 anions is confirmed in the glassy phase. The coordination number of the disulfide bonds is 0.65, and each PS4 tetrahedron is connected to two tetrahedrons to form a polymer chain structure of (−P–S–S−)n bonds containing Li ions. The coordination number of Li ions surrounding PS4 anions in the glassy phase is much smaller than that in the pure Li3PS4 glasses. This polymer may find application as a Li-ion conductive binder in sheet-type all-solid-state batteries having low resistance and high capacity retention.

Effect of Lithium Substitution Ratio of Polymeric Binders on Interfacial Conduction within All-Solid-State Battery Anodes.

Problematic issues with electrically inert binders have been less serious in the conventional lithium-ion batteries by virtue of permeable liquid electrolytes (LEs) for ionic connection and/or carbonaceous additives for electronic connection in the electrodes. Contrary to electron-conductive binders used to maximize an active loading level, the development of ion-conductive binders has been lacking owing to the LE-filled electrode configuration. Herein, we represent a tactical strategy for improving the interfacial Li+ conduction in all-solid-state electrolyte-free graphite (EFG) electrodes where the solid electrolytes are entirely excluded, using lithium-substitution-modulated (LSM) binders. Finely tuning a lithium substitution ratio, a conductive LSM-carboxymethyl cellulose (CMC) binder is prepared from a controlled direct Na+/Li+ exchange reaction without a hazardous acid involvement. The EFG electrode employing LSM with a maximum degree of substitution of lithium (DSLi) of ∼68% in our study shows a considerably higher rate capability of 1.05 mA h cm-2 at 1 C and a capacity retention of ∼61.9% after 200 cycles at 0.5 C than those using sodium-CMC (Na-CMC) (0.78 mA h cm-2, ∼49.5%) and LSM with ∼35% lithium substitution (0.93 mA h cm-2, ∼55.4%). More importantly, the correlation between the phase transition near the bottom region of the EFG electrode and the state of charge (SOC) is systematically investigated, clarifying that the improvement of the interfacial conduction is proportional to the DSLi of the CMC binders. Theoretical calculations combined with experimental results further verify that creating the continuous interface through abundant pathways for mobile ions using the Li+-conductive binder is the enhancement mechanism of the interfacial conduction in the EFG electrode, mitigating serious charge transfer resistance.

Fabrication of Flexible Poly(m-aminophenol)/Vanadium Pentoxide/Graphene Ternary Nanocomposite Film as a Positive Electrode for Solid-State Asymmetric Supercapacitors.

In this study, poly(m-aminophenol) (PmAP) has been investigated as a multi-functional conductive supercapacitor binder to replace the conventional non-conductive binder, namely, poly(vinylene difluoride) (PVDF). The kye benefits of using PmAP are that it is easily soluble in common organic solvent and has good film-forming properties, and also its chemical functionalities can be involved in pseudocapacitive reactions to boost the capacitance performance of the electrode. A new ternary nanocomposite film based on vanadium pentoxide (V2O5), amino-functionalized graphene (amino-FG) and PmAP was fabricated via hydrothermal growth of V2O5 nanoparticles on graphene surfaces and then blending with PmAP/DMSO and solution casting. The electrochemical performances of V2O5/amino-FG/PmAP nanocomposite were evaluated in two different electrolytes, such as KCl and Li2SO4, and compared with those of V2O5/amino-FG nanocomposite with PVDF binder. The cyclic voltametric (CV) results of the V2O5/amino-FG/PmAP nanocomposite exhibited strong pseudocapacitive responses from the V2O5 and PmAP phases, while the faradaic redox reactions on the V2O5/amino-FG/PVDF electrode were suppressed by the inferior conductivity of the PVDF. The V2O5/amino-FG/PmAP electrode delivered a 5-fold greater specific capacitance than the V2O5/amino-FG/PVDF electrode. Solid-state asymmetric supercapacitors (ASCs) were assembled with V2O5/amino-FG/PmAP film as a positive electrode, and their electrochemical properties were examined in both KCl and Li2SO4 electrolytes. Although the KCl electrolyte-based ASC has greater specific capacitance, the Li2SO4 electrolyte-based ASC delivers a higher energy density of 51.6 Wh/kg and superior cycling stability.

Novel Strategy for the Formulation of High-Energy-Density Cathodes via Porous Carbon for Li-S Batteries.

Porous carbon is considered an attractive host material for high-energy sulfur electrodes. This study concerns the design of a porous carbon-based sulfur electrode for the formulation of high-energy Li-S batteries. The porous carbon is impregnated with up to 80 vol.% of sulfur and a reduction in both the conductive agent and binder content. Therefore, less solvent can be used during slurry casting to inhibit crack formation following electrode drying. In addition, the utilization of two distinct electrically conducting networks enables reduced battery polarization, resulting in a battery with a capacity of 690 mAh g-1 (even after 100 cycles). Finally, pouch cells are prepared to characterize the practical performance of the optimized cathode. This yields a capacity of 741 mAh and a cathode energy density of 1001 Wh kg-1 . These findings are expected to guide the further development of high-energy-density cathode materials for Li-S batteries.

3D microscale modeling of NMC cathodes using multi-resolution FIB-SEM tomography

The electrochemical performance of the lithium-ion battery (LIB) is intimately linked to the electrodes’ microstructure dictated by the arrangement of the different constituents. The conductive binder domain (CBD) is of critical importance to battery performance; however, the impact of CBD content on electrode performance is not uniquely identified without altering its morphology. Herein, we use realistic digital cathode microstructures reconstructed from focused ion beam scanning electron microscopy (FIB-SEM) tomography with multiple magnification levels for two NMC111 cathodes to assess the sensitivity of the effective electronic conductivity to the intrinsic conductivity of the CBD and active material (AM), deconvolute the impact of CBD content from morphology on effective transport properties, and highlight the impact of CBD nanoporosity on the pore phase tortuosity. The effective electronic conductivity is more sensitive to changes in the bulk conductivity of the conductive additives where increasing their conductivity by one order of magnitude results in a 10-fold increase in the effective conductivity. Additionally, while the CBD content alone with fixed morphology brings about a nonlinear change in the effective conductivity, the CBD morphology is critical even though it becomes less significant at high CBD contents. Finally, the CBD nanoporosity can lower the tortuosity by ∼17%.

Electrospun Nanofiber Electrodes for High and Low Humidity PEMFC Operation

MEAs with nanofiber mat electrodes containing Pt/C catalyst and Nafion binder were fabricated and evaluated. The electrodes were prepared by electrospinning a solution of catalyst powder, salt-form Nafion (with Na+, Li+, or Cs+ as the sulfonic acid counterion), and a carrier polymer of either polyethylene oxide or poly(acrylic acid). The carrier polymer was extracted prior to MEA testing by a hot water soaking step. The resulting fibers were 15%–17% porous, with a core–shell-like morphology (a coating of primarily Nafion on the fiber surface). MEAs with anode/cathode catalyst loadings of 0.1 mgPt cm−2 each and a Nafion 211 membrane produced high power at both high and low relative humidity (RH) conditions in H2/air fuel cell tests, e.g., a maximum power density of 919 mW cm−2 at 100% RH and 832 mW cm−2 at 40% RH for a test at 80 °C and 200 kPaabs. The presence of nm-size pores within the fibers trapped water via capillary condensation during low RH feed gas testing, thus maintaining a high proton conductivity of the Nafion binder in the anode and cathode while minimizing/eliminating ionic isolation of catalyst particles in low water content, poorly conductive binder.

Porous Carbon Nanofiber Flexible Membranes via a Bottlebrush Copolymer Template for Enhanced High-Performance Supercapacitors.

We report a method to construct ordered hierarchical porous structures in carbon nanofiber membranes using poly(ethylene oxide)-block-polydimethylsiloxane bottlebrush block copolymers (BBCPs) as templates. The BBCPs self-assemble into a spherical morphology driven by small-molecule hydrogen bond donors which act as bridges between carbon precursors and templates to promote uniform dispersion of the templates. We successfully obtained flexible, self-supporting, and porous carbon nanofiber membranes (PCNFs) with high porosity. Then, a supercapacitor electrode was independently prepared using PCNFs as an active substance without infiltrating any conductive agents or binders. The PCNFs exhibit excellent performance with a capacitance of 234.1 F g-1 at a current density of 1 A g-1 owing to the abundant hierarchical porous structures and high content of nitrogen and oxygen elements internally. The aqueous symmetric supercapacitor prepared using PCNFs electrodes maintains more than 95% capacitance retention after 55,000 charge-discharge cycles. Furthermore, the capacitance retention reaches up to 67.72% at a current density of 50 A g-1 (compared to 1 A g-1), exhibiting excellent cycling stability and rate capability. Based on the excellent electrochemical performance and flexible self-supporting ability of PCNFs, this work is expected to facilitate the development of flexible displays, flexible sensors, wearable devices, and electrocatalysis.

Interconnected Metallic Membrane Enabled by MXene Inks Toward High‐Rate Anode and High‐Voltage Cathode for Li‐Ion Batteries

AbstractThe ever‐increasing popularity of smart electronics demands advanced Li‐ion batteries capable of charging faster and storing more energy, which in turn stimulates the innovation of electrode additives. Developing single‐phase conductive networks featuring excellent mechanical strength/integrity coupled with efficient electron transport and durability at high‐voltage operation should maximize the rate capability and energy density, however, this has proven to be quite challenging. Herein, it is shown that a 2D titanium carbide (known as MXene) metallic membrane can be used as single‐phase interconnected conductive binder for commercial Li‐ion battery anode (i.e., Li4Ti5O12) and high‐voltage cathodes (i.e., Ni0.8Mn0.1Co0.1O2). Electrodes are fabricated directly by slurry‐casting of MXene aqueous inks composited with active materials without any other additives or solvents. The interconnected metallic MXene membrane ensures fast charge transport and provides good durability, demonstrating excellent rate performance in the Li//Li4Ti5O12cell (90 mAh g−1at 45 C) and high reversible capacity (154 mAh g−1at 0.2 C/0.5 C) in Li//Ni0.8Mn0.1Co0.1O2cell coupled with high‐voltage operation (4.3 V vs Li/Li+). The LTO//NMC full cell demonstrates promising cycling stability, maintaining capacity retention of 101.4% after 200 cycles at 4.25 V (vs Li/Li+) operation. This work provides insights into the rational design of binder‐free electrodes toward acceptable cyclability and high‐power density Li‐ion batteries.

Sulfur polymerization strategy based on the intrinsic properties of polymers for advanced binder‐free and high‐sulfur‐content Li–S batteries

AbstractLithium–sulfur (Li–S) batteries are the promising next‐generation secondary energy storage systems, because of their advantages of high energy density and environmental friendliness. Among numerous cathode materials, organosulfur polymer materials have received extensive attentions because of their controllable structure and uniform sulfur distribution. However, the sulfur content of most organosulfur polymer cathodes is limited (S content <60%) due to the addition of large amounts of conductive agents and binders, which adversely affects the energy density of Li–S batteries. Herein, a hyperbranched sulfur‐rich polymer based on modified polyethyleneimine (Ath‐PEI) named carbon nanotube‐entangled poly (allyl‐terminated hyperbranched ethyleneimine‐random‐sulfur) (CNT/Ath‐PEI@S) was prepared by sulfur polymerization and used as a Li–S battery cathode. The high intrinsic viscosity of Ath‐PEI provided considerable adhesion and avoided the addition of PVDF binder, thereby increasing the sulfur content of cathodes to 75%. Moreover, considering the uniform distribution of elemental sulfur by the polymer, the utilization of sulfur was successfully improved, thus improving the rate capability and discharge capacity of the battery. The binder‐free, sulfur‐rich polymer cathode exhibited ultra‐high initial discharge capacity (1520.7 mAh g−1 at 0.1 C), and high rate capability (804 mAh g−1 at 2.0 C). And cell‐level calculations show that the electrode exhibits an initial capacity of 942.3 mAh g−1electrode, which is much higher than those of conventional sulfur‐polymer electrodes reported in the literature.

Free‐Standing α‐MoO3/Ti3C2 MXene Hybrid Electrode in Water‐in‐Salt Electrolytes

While transition‐metal oxides such as α‐MoO3 provide high capacity, their use is limited by modest electronic conductivity and electrochemical instability in aqueous electrolytes. Two‐dimensional (2D) MXenes, offer metallic conductivity, but their capacitance is limited in aqueous electrolytes. Insertion of partially solvated cations into Ti3C2 MXene from lithium‐based water‐in‐salt (WIS) electrolytes enables charge storage at positive potentials, allowing a wider potential window and higher capacitance. Herein, we demonstrate that α‐MoO3/Ti3C2 hybrids combine the high capacity of α‐MoO3 and conductivity of Ti3C2 in WIS (19.8 m LiCl) electrolyte in a wide 1.8 V voltage window. Cyclic voltammograms reveal multiple redox peaks from α‐MoO3 in addition to the well‐separated peaks of Ti3C2 in the hybrid electrode. This leads to a higher specific charge and a higher rate capability compared to a carbon and binder containing α‐MoO3 electrode. These results demonstrate that the addition of MXene to less conductive oxides eliminates the need for conductive carbon additives and binders, leads to a larger amount of charge stored, and increases redox capacity at higher rates. In addition, MXene encapsulated α‐MoO3 showed improved electrochemical stability, which was attributed to the suppressed dissolution of α‐MoO3. The work suggests that oxide/MXene hybrids are promising for energy storage.

Concentration shift experiment with an electrode of active material for precise electrochemical analysis.

To precisely evaluate the electrochemical properties of a battery of active material, we proposed a "concentration shift experiment" using single-particle electrochemical measurement (SPEM) and a diluted electrode sheet (DES). SPEM can be used for information, such as the charge-discharge and resistance properties of only the active material (extremely dilute condition: ≈0). DES consists of concentrations varying from 1% to 100% of the active material (LiCoO2) and inactive material (α-Al2O3), electrically conductive additive and binder polymer onto an Al current collector. The resistance components derived from the LiCoO2 single particles were measured and calculated. Their apparent activation energy (Ea) was 27 kJ mol-1, which is relatively low compared with the applied-type sheet electrode (30-60 kJ mol-1). Simple electric/ionic conductive route was analyzed using SPEM cell, and the fundamental LiCoO2 originated Ea could be calculated. Resistance components attributed to LiCoO2 were also measured and extracted by alternating current impedance measurements using DES. The resistance non-linearly decreased with LiCoO2 concentration, and the percolation and inhomogeneity of LiCoO2 particles were suspected. The planful isolation of an active material particle should be critical for the overall information on an electrode particle.

Tightly intercalated Ti3C2Tx/MoO3-x/PEDOT:PSS free-standing films with high volumetric/gravimetric performance for flexible solid-state supercapacitors.

Ti3C2Tx-MXenes have extremely promising applications in electrochemistry, but the development of Ti3C2Tx is limited due to severe self-stacking problem. Here, we introduced oxygen vacancy-enriched molybdenum trioxide (MoO3-x) with pseudocapacitive properties as the intercalator of Ti3C2Tx and PEDOT with high electronic conductivity as the co-intercalator and conductive binder of Ti3C2Tx to synthesize Ti3C2Tx/MoO3-x/PEDOT:PSS (TMP) free-standing films by vacuum-assisted filtration and H2SO4 soaking. The tightly intercalated free-standing film structure can effectively improve the self-stacking phenomenon of Ti3C2Tx, expose more active sites and facilitate electron/ion transport, thus making TMP show excellent electrochemical performance. The volumetric and gravimetric capacitance of optimized TMP-2 can reach 1898.5 F cm-3 and 523.0 F g-1 at 1 A g-1 with a rate performance of 90.5% at the current density from 1 A g-1 to 20 A g-1, which is significantly better than those of MXene-based composites reported in the literature. The directly-assembled TMP-2//TMP-2 flexible solid-state supercapacitor displays high energy/power output performances (25.1 W h L-1 at 6383.1 W L-1, 6.9 W h kg-1 at 1758.4 W kg-1) and there is no obvious change after 100 cycles at a bending angle of 180°. As a result, the tightly intercalated TMP-2 free-standing film with high volumetric/gravimetric capacitances is a promising material for flexible energy storage devices.

Slidable and Highly Ionic Conductive Polymer Binder for High-Performance Si Anodes in Lithium-Ion Batteries.

Silicon is expected to become the ideal anode material for the next generation of high energy density lithium battery because of its high theoretical capacity (4200 mAh g-1 ). However, for silicon electrodes, the initial coulombic efficiency (ICE) is low and the volume of the electrode changes by over 300% after lithiation. The capacity of the silicon electrode decreases rapidly during cycling, hindering the practical application. In this work, a slidable and highly ionic conductive flexible polymer binder with a specific single-ion structure (abbreviated as SSIP) is presented in which polyrotaxane acts as a dynamic crosslinker. The ionic conducting network is expected to reduce the overall resistance, improve ICE and stabilize the electrode interface. Furthermore, the introduction of slidable polyrotaxane increases the reversible dynamics of the binder and improves the long-term cycling stability and rate performance. The silicon anode based on SSIP provides a discharge capacity of ≈1650 mAh g-1 after 400 cycles at 0.5C with a high ICE of upto 92.0%. Additionally, the electrode still exhibits a high ICE of 87.5% with an ultra-high Si loading of 3.84mg cm-2 and maintains a satisfying areal capacity of 5.9 mAh cm-2 after 50 cycles, exhibiting the potential application of SSIP in silicon-based anodes.

3D High-Resolution Chemical Characterization of Sputtered Li-Rich NMC811 Thin Films Using TOF-SIMS.

Massive demand for Li-ion batteries stimulates the research of new materials such as high-capacity cathodes, metal anodes, and solid electrolytes, which should ultimately lead to new generations of batteries such as all-solid-state batteries. Such material discovery often requires knowledge on lithium's content and local distribution in complex Li-containing systems, which is a challenging analytical task. The state-of-the-art time-of-flight secondary-ion mass spectrometry (TOF-SIMS) is one of the few chemical analysis techniques allowing for parallel detection of all sample components and representing their distributions in 3D with nanoscale resolution. In this work, we explore the outstanding potential of TOF-SIMS for comprehensive chemical and nano-/micro-structural characterization of novel Li-rich nickel manganese cobalt oxide thin films, which are potential cathode materials for the future generation batteries. Off-stoichiometric thin films of Li- and Ni-rich layered oxide with the composition of LixNi0.8Mn0.1Co0.1O2 (LR-NMC811, x > 1) were deposited using reactive magnetron sputtering. Such thin films do not contain any conductive additives or binders and therefore serve as model 2D systems to investigate compositional fluctuations, surface and interface phenomena, and their aging. TOF-SIMS revealed the presence of 400 ± 100 nm overlithiated grains and 100 ± 30 nm nanoparticles with an increased 7Li16O+ ion content in the buried part of LR-NMC811. The Li-rich agglomerates could potentially serve as Li reservoirs for compensating Li losses during cathode fabrication and cell operation. Interestingly, these sub-micron structures decomposed in time upon exposure to ambient conditions for 30 days.

Analysis of Electrochemical Performance with Dispersion Degree of CNTs in Electrode According to Ultrasonication Process and Slurry Viscosity for Lithium-Ion Battery.

Lithium-ion batteries (LIBs) continue to dominate the battery market with their efficient energy storage abilities and their ongoing development. However, at high charge/discharge C-rates their electrochemical performance decreases significantly. To improve the power density properties of LIBs, it is important to form a uniform electron transfer network in the cathode electrode via the addition of conductive additives. Carbon nanotubes (CNTs) with high crystallinity, high electrical conductivity, and high aspect ratio properties have gathered significant interest as cathode electrode conductive additives. However, due to the high aggregational properties of CNTs, it is difficult to form a uniform network for electron transfer within the electrode. In this study, to help fabricate electrodes with well-dispersed CNTs, various electrodes were prepared by controlling (i) the mixing order of the conductive material, binder, and active material, and (ii) the sonication process of the CNTs/NMP solution before the electrode slurry preparation. When the binder was mixed with a well sonicated CNTs/NMP solution, the CNTs uniformly adsorbed to the then added cathode material of LiNi0.6Co0.2Mn0.2O2 and were well-dispersed to form a flowing uniform network. This electrode fabrication process achieved > 98.74% capacity retention after 50 cycles at 5C via suppressed polarization at high current densities and a more reversible H1-M phase transition of the active material. Our study presents a novel design benchmark for the fabricating of electrodes applying well-dispersed CNTs, which can facilitate the application of LIBs in high current density applications.

A flexible hard carbon microsphere/MXene film as a high-performance anode for sodium-ion storage

Hard carbon is considered the most promising anode material for sodium-ion batteries, but its volume change during sodiation/desodiation limits its cycle life. Hard carbon microspheres (HCSs) with no binder were composited with a MXene film to form an electrode and its sodium storage properties were studied. The microspheres were prepared using Shanxi aged vinegar as a liquid carbon source. Two-dimensional Ti3C2Tx MXene (T is a functional group) was used as a multifunctional conductive binder to fabricate the flexible electrodes. Remarkably, because of the three-dimensional conductive network, the HCS/Ti3C2Tx film electrode has a high capacity of 346 mAh g−1, excellent rate performance and outstanding cycling stability over 1 000 cycles. This remarkable electrochemical performance indicates that the flexible film is a very promising anode for next-generation sodium-ion batteries.