Synergistically Engineering Grains and Grain Boundaries toward Li Dendrite-Free Li7La3Zr2O12.

Cation-doped cubic Li7La3Zr2O12 is regarded as a promising solid electrolyte for safe and energy-dense solid-state lithium batteries. However, it suffers from the formation of Li2CO3 and high electronic conductivity, which give rise to an unconformable Li/Li7La3Zr2O12 interface and lithium dendrites. Herein, composite AlF3-Li6.4La3Zr1.4Ta0.6O12 solid electrolytes were created based on thermal AlF3 decomposition and F/O displacement reactions under a high-temperature sintering process. When the AlF3 is thermally decomposed, it leaves Al2O3/AlF3 meliorating the grain boundaries and F- ions partially displacing O2- ions in the grains. Due to the higher electronegativity of F- in the grains and the grain-boundary modification, these AlF3-Li6.4La3Zr1.4Ta0.6O12 deliver optimized electronic conduction and chemical stability against the formation of Li2CO3. The Li/AlF3-Li6.4La3Zr1.4Ta0.6O12/Li cell exhibits a low interfacial resistance of ∼16 Ω cm2 and an ultrastable long-term cycling behavior for 800 h under a current density of 200 µA/cm2, leading to Li//LiCoO2 solid-state batteries with good rate performance and cycling stability.

Electron-injection-engineering induced dual-phase MoO2.8F0.2/MoO2.4F0.6 heterostructure for magnesium storage.

Rechargeable magnesium batteries (RMBs) have received increased attention due to their high volumetric capacity and safety. Nevertheless, the sluggish diffusion kinetics of highly polarized Mg2+ in host lattices severely hinders the development of RMBs. Herein, we report an electron injection strategy for modulating the Mo 4d-orbital splitting manner and first fabricate a dual-phase MoO2.8F0.2/MoO2.4F0.6 heterostructure to accelerate Mg2+ diffusion. The electron injection strategy triggers weak Jahn-Teller distortion in MoO6 octahedra and reorganization of the Mo 4d-orbital, leading to a partial phase transition from orthorhombic phase MoO2.8F0.2 to cubic phase MoO2.4F0.6. As a result, the designed heterostructure generates a built-in electric field, simultaneously improving its electronic conductivity and ionic diffusivity by at least one order of magnitude compared to MoO2.8F0.2 and MoO2.4F0.6. Importantly, the assembled MoO2.8F0.2/MoO2.4F0.6//Mg full cell exhibits a remarkable reversible capacity of 172.5 mAh g-1 at 0.1 A g-1, pushing forward the orbital-scale manipulation for high-performance RMBs.

Modulating Surface Architecture and Electronic Conductivity of Li-rich Manganese-Based Cathode.

Li-rich manganese-based cathode (LRMC) has attracted intense attention to developing advanced lithium-ion batteries with high energy density. However, LRMC is still plagued by poor cyclic stability, undesired rate capacity, and irreversible oxygen release. To address these issues, herein, a feasible polyvinylidene fluoride (PVDF)-assisted interface modification strategy is proposed for modulating the surface architecture and electronic conductivity of LRMC by intruding the F-doped carbon coating, spinel structure, and oxygen vacancy on the LRMC, which can greatly enhance the cyclic stability and rate capacity, and restrain the oxygen release for LRMC. As a result, the modified material delivers satisfactory cyclic performance with a capacity retention of 90.22% after 200 cycles at 1 C, an enhanced rate capacity of 153.58 mAh g-1 at 5 C and 126.32 mAh g-1 at 10 C, and an elevated initial Coulombic efficiency of 85.63%. Moreover, the thermal stability, electronic conductivity, and structure stability of LRMC are also significantly improved by the PVDF-assisted interface modification strategy. Therefore, the strategy of simultaneously modulating the surface architecture and the electronic conductivity of LRMC provides a valuable idea to improve the comprehensive electrochemical performance of LRMC, which offers a promising reference for designing LRMC with high electrochemical performance.

V-Doping Strategy Induces the Construction of the CoFe-LDHs/NF Electrodes with Higher Conductivity to Achieve Higher Energy Density for Advanced Energy Storage Devices.

Doping of metal ions shows promising potential in optimizing and modulating the electrical conductivity of layered double hydroxides (LDHs). However, there is still much room for improvement in common metal ions and conventional doping methods. In contrast to previous methodologies, a hollow triangular nanoflower structure of CoFeV-LDHs is devised, which is enriched with a greater number of oxygen vacancies. This resulted in a significant enhancement in the conductivity of the LDHs, leading to an increase in energy density following the appropriate doping of V. To investigate the impact of V-doping on the energy density of the LDHs, in situ XPS and in situ X-ray spectroscopy is employed. Regarding electrochemical performance, the CoFeV-LDHs/NF electrode with optimal doping ratio exhibited a specific capacitance of 881 F g-1 at a current density of 1 A g-1. The capacitance remained at 90.53% after 3000 cycles. In addition, the constructed battery-type supercapacitor CoFeV-LDHs/NF-2//AC exhibited an impressive energy density of 124.7 Wh kg-1 at a power density of 850 W kg-1 and capacitance remained almost unchanged at 95.2% after 3000 cycles. All the above demonstrates the great potential of V-doped LDHs and brings a new way for the subsequent research of LDHs.

Advances in electroactive bioscaffolds for repairing spinal cord injury.

Spinal cord injury (SCI) is a devastating neurological disorder, leading to loss of motor or somatosensory function, which is the most challenging worldwide medical problem. Re-establishment of intact neural circuits is the basis of spinal cord regeneration. Considering the crucial role of electrical signals in the nervous system, electroactive bioscaffolds have been widely developed for SCI repair. They can produce conductive pathways and a pro-regenerative microenvironment at the lesion site similar to that of the natural spinal cord, leading to neuronal regeneration and axonal growth, and functionally reactivating the damaged neural circuits. In this review, we first demonstrate the pathophysiological characteristics induced by SCI. Then, the crucial role of electrical signals in SCI repair is introduced. Based on a comprehensive analysis of these characteristics, recent advances in the electroactive bioscaffolds for SCI repair are summarized, focusing on both the conductive bioscaffolds and piezoelectric bioscaffolds, used independently or in combination with external electronic stimulation. Finally, thoughts on challenges and opportunities that may shape the future of bioscaffolds in SCI repair are concluded.

Decreased Electrically and Increased Ionically Conducting Scaffolds for Long-Life, High-Rate and Deep-Capacity Lithium-Metal Anodes.

Lithium (Li) metal batteries are deemed as promising next-generation power solutions but are hindered by the uncontrolled dendrite growth and infinite volume change of Li anodes. The extensively studied 3D scaffolds as solutions generally lead to undesired "top-growth" of Li due to their high electrical conductivity and the lack of ion-transporting pathways. Here, by reducing electrical conductivity and increasing the ionic conductivity of the scaffold, the deposition spot of Li to the bottom of the scaffold can be regulated, thus resulting in a safe bottom-up plating mode of the Li and dendrite-free Li deposition. The resulting symmetrical cells with these scaffolds, despite with a limited pre-plated Li capacity of 5 mAh cm-2, exhibit ultra-stable Li plating/stripping for over 1 year (11 000 h) at a high current density of 3 mA cm-2 and a high areal capacity of 3 mAh cm-2. Moreover, the full cells with these scaffolds further demonstrate high cycling stability under challenging conditions, including high cathode loading of 21.6 mg cm-2, low negative-to-positive ratio of 1.6, and limited electrolyte-to-capacity ratio of 4.2 g Ah-1.

Construction of Hierarchical Conductive Networks for LiNi0.8Mn0.1Co0.1O2 Cathode toward Stable Cycling at High Areal Mass Loadings.

Realizing high-performance thick electrodes is considered as a practical strategy to promote the energy density of lithium-ion batteries. However, establishing effective transport pathways for both lithium-ions and electrons in a thick electrode is very challenging. This study develops a hierarchical conductive network structure for constructing high-performance NMC811 (LiNi0.8Mn0.1Co0.1O2) cathode toward stable cycling at high areal mass loadings. The hierarchical conductive networks are composed of a Li+/e- mixed conducting interface (lithium polyacrylate/hydroxyl-functionalized multiwalled carbon nanotubes) on NMC811 particles, and a segregated network of single-walled carbon nanotubes in the electrode, without any additional binders or carbon black. Such strategy endows the NMC811 cathode (up to 250 µm and 50 mg cm-2) with low porosity/tortuosity, ultrahigh Li+/e- conductivities and excellent mechanical property at low carbon nanotube content (1.8 wt%). It significantly improves the electrochemical reaction homogeneity along the electrode depth, meanwhile effectively inhibits the side reactions at the electrode/electrolyte interface and cracks in the NMC particles during cycling. This work emphasizes the crucial role of the electronic/ionic cooperative transportation in the performance deterioration of thick cathodes, and provide guidance for architecture optimization and performance improvement of thick electrodes toward practical applications, not just for the NMC811 cathode.

Calcium Doped NASICON Electrolyte with Graphite Coating for Stable All-solid-state Sodium Metal Batteries.

All-solid-state sodium metal batteries face the challenges of low ionic conductivity of solid electrolytes and poor wettability towards metallic Na anode. Herein, Na3Zr2Si2PO12 solid electrolyte is doped with Ca2+, obtaining a high ionic conductivity of 2.09×10-3 S cm-1 with low electronic conductivity of 1.43×10-8 S cm-1 at room temperature, which could accelerate Na+ transportation and suppress sodium dendrite growth. Meanwhile, a graphite-based interface layer is coated on Na3.4Zr1.8Ca0.2Si2PO12 (Na3.4Zr1.8Ca0.2Si2PO12-G) in order to improve the solid-solid contact between solid electrolyte and Na anode, realizing a uniform current distribution and smooth Na metal plating/stripping, and thus achieving a triple higher critical current density of 3.5 mA cm-2 compared with that of Na3.4Zr1.8Ca0.2Si2PO12. In addition, the assembled Na3V2(PO4)3/Na3.4Zr1.8Ca0.2Si2PO12-G/Na all-solid-state battery exhibits excellent electrochemical performances with a reversible capacity of 81.47 mAh g-1 at 1 C and capacity retention of 97.75 % after 500 cycles.

Electrochemical Doping Effect on the Conductivity of Melanin-Inspired Materials.

Eumelanin is a natural pigment that can be particularly valuable for sustainable bioelectronic devices due to its inherent biocompatibility and hydration-dependent conductivity. However, the low conductivity of eumelanin limits its technological development. In this research, electrochemical doping was proposed as an alternative route to increase the electronic conductivity of synthetic eumelanin derivatives. Thin films of sulfonated eumelanin were deposited on platinum interdigitated electrodes and electrochemically treated by using cyclic voltammetry and chronoamperometry treatments. X-ray photoelectron spectroscopy analysis confirmed ion doping in sulfonated melanin. Current-voltage, current-time, and electrochemical impedance measurements were used to investigate the effect of different aqueous electrolytes (including KCl and LiClO4) treatments on the charge transport of sulfonated eumelanin. We show that the conductivity depends on the type and size of the anion used and can reach 10-3 S·cm-1. Additionally, depending on the electrolyte, there is a change in charge transport from mixed ionic/electronic to a predominantly electronic-only conduction. Our results show that the chemical nature of the ion plays an important role in the electrochemical doping and, consequently, in the charge transport of eumelanin. These insights serve as inspiration to explore the use of alternative electrolytes with different compositions further and develop eumelanin-based devices with tunable conductivities.

Indium Nitride Nanowires: Low Redox Potential Anodes for Lithium-Ion Batteries.

Advanced lithium-ion batteries (LIBs) are crucial to portable devices and electric vehicles. However, it is still challenging to further develop the current anodic materials such as graphite due to the intrinsic limited capacity and sluggish Li-ion diffusion. Indium nitride (InN), which is a new type of anodic material with low redox potential (<0.7 V vs Li/Li+) and narrow bandgap (0.69 eV), may serve as a new high-energy density anode material for LIBs. Here, the growth of 1D single crystalline InN nanowires is reported on Au-decorated carbon fibers (InN/Au-CFs) via chemical vapor deposition, possessing a high aspect ratio of 400. The binder-free Au-CFs with high conductivity can provide abundant sites and enhance binding force for the dense growth of InN nanowires, displaying shortened Li ion diffusion paths, high structural stability, and fast Li+ kinetics. The InN/Au-CFs can offer stable and high-rate Li delithiation/lithiation without Li deposition, and achieve a remarkable capacity of 632.5 mAh g-1 at 0.1 A g-1 after 450 cycles and 416 mAh g-1 at a high rate of 30 A g-1. The InN nanowires as battery anodes shall hold substantial promise for fulfilling superior long-term cycling performance and high-rate capability for advanced LIBs.

Topologically Tunable Conjugated Metal-Organic Frameworks for Modulating Conductivity and Chemiresistive Properties for NH3 Sensing.

Electrically conductive metal-organic frameworks (cMOFs) have garnered significant attention in materials science due to their potential applications in modern electrical devices. However, achieving effective modulation of their conductivity has proven to be a major challenge. In this study, we have successfully prepared cMOFs with high conductivity by incorporating electron-donating fused thiophen rings in the frameworks and extending their π-conjugated systems through ring-closing reactions. The conductivity of cMOFs can be precisely modulated ranging from 10-3 to 102 S m-1 by regulating their dimensions and topologies. Furthermore, leveraging the inherent tunable electrical properties based on topology, we successfully demonstrated the potential of these materials as chemiresistive gas sensors with an outstanding response toward 100 ppm NH3 at room temperature. This work not only provides valuable insights into the design of functional cMOFs with different topologies but also enriches the cMOF family with exceptional conductivity properties.

Versatile Nitrogen-Centered Organic Redox-Active Materials for Alkali Metal-Ion Batteries.

Versatile nitrogen-centered organic redox-active molecules have gained significant attention in alkali metal-ion batteries (AMIBs) due to their low cost, low toxicity, and ease of preparation. Specially, their multiple reaction categories (anion/cation insertion types of reaction) and higher operating voltage, when compared to traditional conjugated carbonyl materials, underscore their promising prospects. However, the high solubility of nitrogen-centered redox active materials in organic electrolyte and their low electronic conductivity contribute to inferior cycling performance, sluggish reaction kinetics, and limited rate capability. This review provides a detailed overview of nitrogen-centered redox-active materials, encompassing their redox chemistry, solutions to overcome shortcomings, characterization of charge storage mechanisms, and recent progress. Additionally, prospects and directions are proposed for future investigations. It is anticipated that this review will stimulate further exploration of underlying mechanisms and interface chemistry through in situ characterization techniques, thereby promoting the practical application of nitrogen-centered redox-active materials in AMIBs.

Defining ferroelectric characteristics with reversible piezoresponse: PUND switching spectroscopy PFM characterization.

Detecting ferroelectricity at micro- and nanoscales is crucial for advanced nanomaterials and materials with complicated topography. Switching spectroscopy piezoresponse force microscopy (SSPFM), which involves measuring piezoelectric hysteresis loops via a scanning probe microscopy tip, is a widely accepted approach to characterize polarization reversal at the local scale and confirm ferroelectricity. However, the local hysteresis loops acquired through this method often exhibit unpredictable shapes, a phenomenon often attributed to the influence of parasitic factors such as electrostatic forces and current flow. Our research has uncovered that the deviation in hysteresis loop shapes can be caused by spontaneous backswitching occurring after polarization reversal. Moreover, we've determined that the extent of this effect can be exacerbated when employing inappropriate SSPFM waveform parameters, including duration, frequency, and AC voltage amplitude. Notably, the conventional 'pulse-mode' SSPFM method has been found to intensify spontaneous backswitching. In response to these challenges, we have redesigned SSPFM approach by introducing the positive up-negative down (PUND) method within the 'step-mode' SSPFM. This modification allows for effective probing of local piezoelectric hysteresis loops in ferroelectrics with reversible piezoresponse while removing undesirable electrostatic contribution. This advancement extends the applicability of the technique to a diverse range of ferroelectrics, including semiconductor ferroelectrics and relaxors, promising a more reliable and accurate characterization of their properties.

Copper Phosphide Nanostructures Covalently Modified Ti3 C2 Tx for Fast Lithium-Ion Storage by Enhanced Kinetics and Pesudocapacitance.

2D layer Ti3 C2 Tx material attracts enormous attention in lithium ion energy storage field owing to the unique surface chemistry properties, but the material still suffers from restacking issue and the restriction on capacity. Herein, copper phosphide (Cu3 P) nanostructures@Ti3 C2 Tx composites are prepared by the in situ generation of Cu-BDC precursor in the bulk material followed with phosphorization. The uniformly distributed copper phosphide nanostructures effectively expand the interlayer spacing promoting the structural stability, and achieves the effective connection with the bulk material accelerating the diffusion and migration of lithium ions. The electrochemical activity of Cu3 P also provides more lithium ion active sites for lithium storage. The X-ray photoelectron spectroscopy (XPS) analysis verifies that Ti─O─P bond with strong covalency allows the upper shift of maximum valence band and Fermi level, stimulating the charge transportation between Cu3 P and the bulk Ti3 C2 Tx for better electrode kinetics. 3Cu3 P@Ti3 C2 Tx exhibits excellent rate performance of 165.4 mAh g-1 at 3000 mA g-1 and the assembled 3Cu3 P@Ti3 C2 Tx //AC Lithium-ion hybrid capacitorsLIC exhibits superior energy density of 93.0 Wh kg-1 at the power density of 2367.3 W kg-1 . The results suggest that the interfacial modification of Ti3 C2 Tx with transition metal phosphides will be advantageous to its high energy density application in lithium-ion storage.

Enhanced Electrochemical Performance of Ca-Doped Na3V2(PO4)2F3/C Cathode Materials for Sodium-Ion Batteries.

Na3V2(PO4)2F3 (NVPF) with a NASICON structure has garnered attention as a cathode material owing to its stable 3D structure, rapid ion diffusion channels, high operating voltage, and impressive cycling stability. Nevertheless, the low intrinsic electronic conductivity of the material leading to a poor rate capability presents a significant challenge for practical application. Herein, we develop a series of Ca-doped NVPF/C cathode materials with various Ca2+ doping levels using a simple sol-gel and carbon thermal reduction approach. X-ray diffraction analysis confirmed that the inclusion of Ca2+ does not alter the crystal structure of the parent material but instead expands the lattice spacing. Density functional theory calculations depict that substituting Ca2+ ions at the V3+ site reduces the band gap, leading to increased electronic conductivity. This substitution also enhanced the structural stability, preventing lattice distortion during the charge/discharge cycles. Furthermore, the presence of the Ca2+ ion introduces two localized states within the band gap, resulting in enhanced electrochemical performance compared to that of Mg-doped NVPF/C. The optimal NVPF-Ca-0.05/C cathode exhibits superior specific capacities of 124 and 86 mAh g-1 at 0.1 and 10 C, respectively. Additionally, the NVPF-Ca-0.05/C demonstrates satisfactory capacity retention of 70% after 1000 charge/discharge cycles at 10 C. These remarkable results can be attributed to the optimized particle size, excellent structural stability, and enhanced ionic and electronic conductivity induced by the Ca doping. Our findings provide valuable insight into the development of cathode material with desirable electrochemical properties.

Reversible Na Plating/Stripping with High Areal Capacity Using an Electroconductive Liquid Electrolyte System.

Anode-free sodium-metal batteries (AFSMBs) are promising candidates for maximizing energy density and minimizing cost and safety hazards in the absence of metallic sodium during cell assembly. The practical implementation of AFSMBs is hindered by the low cycling stability of Na-metal plating and stripping, particularly under high areal capacities, due to unstable solid electrolyte interphase (SEI) layer formation with electrolyte decomposition and inactive dead Na formation. Here, we proposed an electroconductive electrolyte system consisting of liquid electrolytes that accept electrons at a certain energy level and form electronically conductive and solid electrolytes that prevent internal short circuit through low electronic conductivity. The electron acceptability and high electronic conductivity of the liquid electrolyte can suppress the irreversible electron transfer with electrolyte decomposition and reutilize the inactive dead metal, respectively. The functions of the system were demonstrated using a sodium biphenyl liquid electrolyte-NASICON solid electrolyte in a seawater battery (SWB) system, which features an infinite sodium source. The anode-free SWB cells achieved a high Coulombic efficiency of ≥99.9% for over 60 cycles at a high areal capacity of ∼24 mAh/cm2. This study provides insight into the Na plating/stripping properties in anode-free systems and proposes a significant strategy for improving the reversibility of metal anodes for various battery systems with solid electrolytes.

Spine Surgery with Electronic Conductivity Device: A Prospectively Multicenter Randomized Clinical Trial and Literature Review.

OBJECTIVE: Improving accuracy and safety of pedicle screw placement is of great clinical importance. Electronic conductivity device (ECD) can be a promising technique with features of affordability, portability, and real-time detection capabilities. This study aimed to validate the safety and effectiveness of a modified ECD. METHODS: The ECD underwent a modification where six lamps of various colors, and it was utilized in a prospectively multicenter randomized controlled clinical trial involving 96 patients across three hospitals from June 2018 to December 2018. The trial incorporated a self-control randomization with an equal distribution of left or right side of vertebral pedicle among two groups: the free-hand group and the ECD group. A total of 496 pedicle screws were inserted, with 248 inserted in each group. The primary outcomes focused on the accuracy of pedicle screw placement and the frequency of intraoperative X-rays. Meanwhile, the secondary indicator measured the time required for pedicle screw placement. Results were presented as means ± SD. Paired samples t-test and χ2 -test were used for comparison. Furthermore, an updated review was conducted, which included studies published from 2006 onwards. RESULTS: Baseline patient characteristics were recorded. The primary accuracy outcome revealed a 96.77% accuracy rate in the ECD group, compared to a 95.16% accuracy rate in the free-hand group, with no significant differences noted. In contrast, ECD demonstrated a significant reduction in radiation exposure frequency when compared to the free-hand group (1.11 ± 0.32 vs. 1.30 ± 0.53; p < 0.001), resulting in a 14.6% reduction. Moreover, ECD displayed a decrease of 30.38% in insertion time (70.88 ± 30.51 vs. 101.82 ± 54.00 s; p < 0.001). According to the results of the 21 studies, ECD has been utilized in various areas of the spine such as the atlas, thoracic and lumbar spine, as well as sacral 2-alar-iliac. The accuracy of ECD ranged from 85% to 100%. CONCLUSION: The prospectively randomized trial and the review indicate that the use of ECD presents a secure and precise approach to the placement of pedicle screws, with the added benefit of reducing both procedure time and radiation exposure.

Stable Multicomponent Multiphase All Active Material Lithium-Ion Battery Anodes.

Due to their high energy density, lithium-ion batteries have been the state-of-the-art energy storage technology for many applications. Energy density can be further improved by engineering of the electrode architecture and microstructure, in addition to more common improvements via materials chemistry. All active material (AAM) electrodes consist of only the electroactive material that stores energy, and such electrodes have advantages to conventional composite processing with regards to improved mechanical stability at increased thicknesses and ion transport properties. However, the absence of binders and composite processing makes the electrode more vulnerable to electroactive materials with volume change upon cycling. Also, the electroactive material must have sufficient electronic conductivity to avoid large matrix electronic overpotentials during electrochemical cycling. TiNb2O7 (TNO) and MoO2 (MO) are electroactive materials with potential advantages as AAM electrodes due to relatively high volumetric energy density. TNO has higher energy density, and MO has much higher electronic conductivity, and thus a multicomponent blend of these materials was evaluated as an AAM anode. Herein, blends of TNO and MO as AAM anodes were investigated, where this is the first use of a multicomponent AAM anode. Electrodes that had both TNO and MO had the highest volumetric energy density, rate capability, and cycle life relative to single component TNO and MO anodes. Thus, using multicomponent materials provides a route to improve AAM electrochemical systems.

Magnetic Field-Enhanced Performance of Superparamagnetic LiMn2 O4 -Based Composite Slurry Electrode for Semisolid Flow Battery.

Semisolid flow batteries are expected to be applied to large-scale energy storage fields due to the combination of the high energy density of rechargeable batteries and the flexible design of flow batteries. However, electronic conductivity, specific capacity, and viscosity of slurry electrodes are generally mutually restrictive. Here, a new concept of semisolid flow batteries based on magnetic modification slurry electrode is proposed and the electrochemical performance of the semisolid electrode is expected to be improved by close contact and enhanced electronic conductivity between the active particles with the aid of external magnetic field. This concept is further demonstrated using superparamagnetic LiMn2 O4 -Fe3 O4 -carbon nanotube composite as semisolid cathode. It achieves a capacity of 113.7 mAh g-1 at a current density of 0.5 mA cm-2 with the aid of external magnetic field (about 0.4 T), which is about 21% higher than that without external magnetic field. Simulation study also reveals this improvement mainly resulted from the increase of the conductive paths of electrons after the rearrangement of the active particles under the external magnetic field. It is believed that this strategy gives a new and effective method for controlling the viscosity and electronic conductivity of the slurry electrodes and related flowable electrochemical energy storage systems.

Ultrahigh-Loading Manganese-Based Electrodes for Aqueous Batteries via Polymorph Tuning.

Manganese-based aqueous batteries utilizing Mn2+ /MnO2 redox reactions are promising choices for grid-scale energy storage due to their high theoretical specific capacity, high power capability, low-cost, and intrinsic safety with water-based electrolytes. However, the application of such systems is hindered by the insulating nature of deposited MnO2 , resulting in low normalized areal loading (0.005-0.05 mAh cm-2 ) during the charge/discharge cycle. In this work, the electrochemical performance of various MnO2 polymorphs in Mn2+ /MnO2 redox reactions is investigated, and ɛ-MnO2 with low conductivity is determined to be the primary electrochemically deposited phase in normal acidic aqueous electrolyte. It is found that increasing the temperature can change the deposited phase from ɛ-MnO2 with low conductivity to γ-MnO2 with two order of magnitude increase in conductivity. It is demonstrated that the highly conductive γ-MnO2 can be effectively exploited for ultrahigh areal loading electrode, and a normalized areal loading of 33 mAh cm-2 is achieved. At a mild temperature of 50 °C, cells are cycled with an ultrahigh areal loading of 20 mAh cm-2 (1-2 orders of magnitude higher than previous studies) for over 200 cycles with only 13% capacity loss.