Improved Capacity Retention Research Articles

All Dry in One Step (ADIOS to Water) Synthesis of W-Coated Li1+X(Ni0.7Mn0.3)1-XO2

Cathode powders for lithium-ion batteries are typically made from hydroxide precursors with the intended transition metal composition and calcined with a lithium source at high temperatures to make LiMO2, where M = Ni, Mn, Co. However, large amounts of process water and salts like NaOH are used in the co-precipitation process employed to make these hydroxide precursors1. Purifying and drying the precursors after co-precipitation requires additional energy input and produces waste streams that are difficult to treat, as illustrated in Fig. 1a. In this work, we introduce a simple, solvent-free method to produce tungsten (W) coated Li1+x(Ni0.7Mn0.3)1-xO2 (NM73) materials from a mixture of Ni, MnO2, LiOH·H2O and W precursors. NM73 was chosen as the primary focus of investigation so that cobalt is avoided due to its scarcity and high cost.The starting reagents are dry mixed and calcined, followed by jet-milling. An extra reheating step after jet-milling is advantageous for minimizing cation disorder and lithium surface impurities. Pure phase, R -3m single crystal NM73 materials can be made with this method and Rietveld refinement analysis showed that low Ni/Li mixing was achieved. W is believed to remain at the surface, forming a separate LixWyOz phase2. The addition of W was found to reduce the mean particle size and improve both the initial discharge capacity and first cycle efficiency. Small amounts of W increase the initial discharge capacity up to 197 mAh/g. Full coin cells were made from both coated and uncoated materials. Their cycling performance is shown in Fig. 1b, revealing improved capacity retention as another improvement afforded by the W coating.The proposed method simplifies the current production process of LiMO2 by eliminating the need for hydroxide precursors entirely. Cobalt-free single crystal materials with excellent electrochemical performance can be made all-dry in one step, potentially reducing the cost of cathode materials significantly and eliminating waste streams.

Simultaneously promoting the surface/bulk structural stability of Fe/Mn-based layered cathode for sodium ion batteries

Layered sodium iron manganese oxide cathodes have attracted great interest owing to their high specific capacity and cost-effective metal resources, while the detrimental phase transitions and surface structural degradation severely limit their commercial applications. In this work, the bulk and surface structure stability of a P2-Na0.67Fe0.5Mn0.5O2 cathode can be synergically enhanced by a one-step Li/Nb co-doping strategy. Structural characterizations reveal that Li doping promotes the formation of P2/O3 biphasic structure and makes the unfavorable P2-OP4 phase transition convert into a smooth solid-solution reaction. Nb doping enhances the mobility of sodium ions and forms strong Nb-O bonds, thereby enhancing the stability of the TMO2 layer structure. In particular, the Nb element induces the surface reorganization of an atomic-scale NaNbO3 coating layer, which could effectively prevent the dissolution of metals and surface side reactions. The synergistic mechanism of enhanced electrochemical performance is proved by multiple characterizations during cycling. As a result, the as-prepared Na0.67Li0.1Fe0.5Mn0.38Nb0.02O2 exhibits improved capacity retention of 85.4 % than raw material (45.7 %) after 100 cycles at 0.5C (1C = 174 mA g−1) within 2.0–4.0 V. This co-regulating strategy provides a promising approach to designing highly stable sodium-ion battery cathodes. Furthermore, a full cell of Na0.67Li0.1Fe0.5Mn0.38Nb0.02O2 with hard carbon displays excellent cycling stability (85.1 % capacity retention after 100 cycles), making its commercial operation possible. This synergistic strategy of biphasic structure and surface reorganization is a critical route to accelerate the application of layer oxide cathodes.

Constructing a Highly Robust Interface Film for Enhancing Rate Performance of Graphite Anode via a Novel Electrolyte Additive.

Solid electrolyte interphase (SEI) is regarded as a key factor to enable high power outputs of Lithium-ion batteries (LIBs). Herein, we demonstrate a modified electrolyte consisting of a novel electrolyte additive, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (FTMS) to construct a highly robust and stable SEI on a graphite anode for LIBs to enhance its rate performance. With 2% FTMS, the anode presents an improved capacity retention from 77.6 to 91.2% at 0.5 C after 100 cycles and an improved capacity from 86 to 229 mAh g-1 at 2 C. Experimental characterizations and theoretical calculations reveal that FTMS is preferentially absorbed and reduced on graphite to construct an interface chemistry with uniform fluoride-containing organic lithium salt and silicon-containing polymer, which exhibits high flexibility and conductivity and endows the SEI with high robustness and stability. This work provides an effective way to address the issue of slow lithium insertion/desertion kinetics of graphite anodes.

Improvement of manganese dioxide cathode by molybdenum doping in highly acidic electrolyte

To address the increased demand for rechargeable batteries such as Li-ion, the market must introduce an alternative to Li-ion technology. Rechargeable Zn-MnO2 battery technology is one feasible option, yet it has struggled to dominate the market due to low cathode cyclic stability and potential. To look into this problem, the characteristics of the cathode material were altered in this work through Mo-doping and modification of the resulting material morphology. KMnO4 was used as a precursor in the hydrothermal synthesis of the active material, which was produced at 120 °C for 12 or 24 h with Mo doping at varied concentrations. The phase composition and morphology of the produced samples were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Moreover, the electrochemical characteristics were determined using a galvanostat. It was found that the synthesised powders consist of α-MnO2 and δ-MnO2 crystalline phases and the phase does not change after cyclic voltammetry (CV) measurements. In addition, the distribution of doped Mo before and after CV measurements was even throughout the sample surface. Furthermore, the addition of up to 2.5 mol% Mo to MnO2 increases the specific capacity of the cathode in a highly acidic (pH = 1.5) electrolyte, in addition, improved capacity retention for faster discharge rates is observed by increasing Mo doping up to 5 mol%.

Correlation between structural characteristics of edge selectively-oxidized graphite and electrochemical performances under fast charging condition

In the pursuit of ameliorating of the battery-performance degradation particularly during fast charging of lithium-ion batteries, we investigated the influence of surface-structural parameter of graphite. To explore the effect of the graphite surface state on the battery performance, we synthesized the edge selectively-oxidized graphite. The detailed analysis about the structural parameters of graphite samples revealed that the edge area increased from 3.41 to 4.26 m2 g−1 by oxidation process while preserving the specific surface area. Edge selectively-oxidized graphite samples showed the similar ratio between carbon and oxygen regardless of oxidized time, but the change of surface charge due to the different functional groups. The edge selectively-oxidized graphite exhibited a significantly improved capacity retention and rate performance compared with the bare graphite. Based on thorough examination about material properties and electrochemical responses, we corroborated a strong correlation among the electrochemical performance, edge surface area, and type of oxygen-based functional groups of graphite. Our study provides conclusive evidence that the surface nature of graphite plays a pivotal role in boosting the battery performance.

Suppressing Bulk Strain and Surface O2 Release in Li-Rich Cathodes by Just Tuning the Li Content.

Layered oxides represent a prominent class of cathodes employed in lithium-ion batteries. The structural degradation of layered cathodes causes capacity decay during cycling, which is generally induced by anisotropic lattice strain in the bulk of cathode particle and oxygen release at the surface. However, particularly in lithium-rich layered oxides (LLOs) that undergo intense oxygen redox reactions, the challenge of simultaneously addressing bulk and surface issues through a singular modification technique remains arduous. Here a thin (1-nm) and coherent spinel-like phase is constructed on the surface of LLOs particle to suppress bulk strain and surface O2 release by just adjusting the amount of lithium source during synthesis. The spinel-like phase hinders the surface O2 release by accommodating O2 inside the surface layer, while the trapped O2 in the bulk impedes strain evolution by ≈70% at high voltages compared with unmodified LLOs. Consequently, the enhanced structural stability leads to an improved capacity retention of 97.6% and a high Coulombic efficiency of ≈99.5% after 100 cycles at 0.1°C. These findings provide profound mechanistic insights into the functioning of surface structure and offer guidance for synthesizing high-capacity cathodes with superior cyclability.

Hybrid crosslinking for in-situ encapsulation of three-dimensional porous SiOx@rGO as high-performance anodes in lithium-ion batteries

Silicon suboxide (SiOx) anodes have garnered significant attention from both academia and industry due to their superior theoretical capacity compared to graphite, as well as their improved capacity retention in comparison to pure silicon. Nevertheless, SiOx electrodes still confront the challenge of substantial volume expansion (>160 %) during the alloying process, resulting in electrode structural damage or even fragmentation and severely impacting cycling performance. Here, a three-dimensional (3D) conductive network was constructed by ethylenediamine (EDA) cross-linking reduced graphene oxide (rGO), which was encapsulated on the surface of SiOx spheres generated in situ via a magnesium thermal reduction reaction. Accordingly, the SiOx@rGO-EDA anode was prepared successfully with high reversible capacity (892 mAh g−1 after 100 cycles at 1 A g−1) and fascinating rate performance (447 mAh g−1 at 4 A g−1). In full cell, the SiOx@rGO-EDA anode also exhibits outstanding cycling stability (154 mAh g−1 after 100 cycles at 0.1C) and rate capability. The scanning electron microscopy (SEM) images captured from a top-view perspective indicate that the surface of SiOx@rGO-EDA electrode is smooth and dense without any noticeable cracks, and it maintains its structural integrity throughout the cycling process. The cross-sectional thickness of the electrode remains essentially the same. These results illustrate the superior structural stability of the EDA cross-linked graphene conductive network cladding structure, enabling it to adapt to dynamic changes and ensure efficient transport of lithium ions and electrons. The facile and versatile synthesis method of SiOx@rGO-EDA structures by incorporating cross-linking agents provides inspiration for the design of next-generation high-performance anodes.

Capacity Retention Through a Separator Coated with Bifunctional Ferroelectric Nanoparticles and Modified Cathodes for Li−S Batteries

AbstractGadolinium (Gd) and Nickel (Ni) doped bismuth ferrite (BiFeO3) nanoparticles Bi0.925Gd.075Fe0.95Ni0.05O3 (BGFNO) with spontaneous polarization (2.5 μC/cm2) were mechano‐chemically synthesized and used to achieve high capacity retention in lithium sulfur (Li−S) batteries. The BGFNO particles were coupled with single walled carbon nanotubes (SWCNT)/sulfur (S) composite cathodes as well as coated on separator. The X‐ray diffraction of BGFNO@S/SWCNT cathodes show an orthorhombic structure with particle size distribution of 20–26 nm, while Raman spectra substantiate efficient coupling of BGFNO with S/SWCNT cathodes, in agreement with SEM images, showing the interconnected network of composites. The specific discharge capacity of S60BGFNO30SWCNT10 composite cathode @ 200 mA/g together with BGFNO coated separator gains maximum capacity up to 1611 mAh/g and retains up to 1294 mAh/g after 50th cycle with improved capacity retention of 80 % showing suppression of polysulfides formation. The coated separator controls transport of carrier ions and side reactions, however modified cathodes with BGFNO particles acts as trapping center for polysulfides to enhance the electrochemical performance of the cells. The Coulombic efficiency(CE) for BGFNO/S/SWCNT composites @ 100 mA/g attained >98 % and CE @ 200 mA/g it is attained > 80 to 90 % compared to S/SWCNT composites in terms of improved cycle stability and reaction kinetics.

Synthesis of porous carbon with low oxygen content from fulvic acid for high voltage organic supercapacitors

The operating voltage of over 3.0 V is a severe challenge for commercial supercapacitors in organic electrolyte, which raises rigorous requirements for the structure and composition characteristics of porous carbon. There are few reports regarding the construction of ultra-high voltage withstanding porous carbon derived from cheap biomass carbon sources. Herein, using cheap and renewable fulvic acid (FA) and graphene oxide (GO) as carbon precursors, the ultra-high withstanding voltage 2D porous carbon nanosheets are synthesized through KOH activation and annealing treatment, assisted by the π-π conjugation and hydrogen bonding. The incorporation of GO plays an important role in modulating the 2D nanosheet morphology of FA derived porous carbon, enhancing the e-conductivity and reducing the OFGs of porous carbons, which makes significant contribution to improving the structural stability and electrochemical performance of material. The obtained FG1% C/C composite simultaneously exhibits high specific surface area (2593 m2/g) and desirable e-conductivity (101 S m−1). More critically, it possesses highly stable surface chemical microenvironment with very-low surface oxygen content of 2.7 at.%, mainly existing as stable ether and quinone bonds. Thus, FG1% exerts ultra-high withstanding voltage up to 3.3 V in commercial TEABF4/PC electrolyte with the maximum energy density of 68.6 Wh kg−1, superior to most of the literatures, also it shows excellent stability throughout its lifespan, maintaining improved capacity retention rate (88.9%) at 2.5 A/g over 10,000 cycles. This work pares the way for the architecture design of high withstanding voltage porous carbon.

Biodegradable Pea Protein Fibril Hydrogel-Based Quasi-Solid-State Zn-Ion Battery.

Zinc-ion batteries show great potential as the next-generation power source due to their nontoxic, low-cost, and safe properties. However, issues with zinc anodes, such as dendrite growth and parasitic hydrogen evolution reactions (HERs), must be addressed to commercialize them. Solutions, such as quasi-solid-state electrolytes made from synthetic polymer hydrogels, have been proposed to improve battery flexibility and energy density. However, most polymers used are nonbiodegradable, posing a challenge to sustainability. In this study, hydrogels made from biodegradable poly(vinyl alcohol) and protein nanofibrils from pea protein, a renewable plant-based source, are used as an electrolyte in aqueous zinc-ion batteries. Results show that the flexible and biodegradable hydrogel can enhance the zinc anode stability and effectively restrict HER. This phenomenon is because of the hydrogen-bond network between nanofibril functional groups and water molecules. In addition, the interaction between functional groups on nanofibrils and Zn2+ constructs ion channels for the even migration of Zn2+, avoiding dendrite growth. The Zn||Zn symmetric cell using the hydrogel electrolyte exhibits a long lifespan of over 3000 h and improved capacity retention in the Zn||AC-I2 hybrid ion batteries by suppressing cathode material dissolution. This study suggests the potential of biodegradable hydrogels as a sustainable and effective solution for biodegradable soft powering sources.

P doping in NCMA cathode improves electronic and cationic conductivity to enable higher capacity retention and better rate performance

In previous reports, P doping was regarded as an effective approach to endow layered NCA cathode material with a better electrochemical performance via suppressing polarization or promoting Li migration. In this work, P doping enables higher capacity retention and better rate performance of NCMA cathode due to the dually improved electronic and cationic conductivity. DFT calculation reveals that P doping reduces the bandgap of NCMA, which inhibits the increase of internal resistance during cycling and thereafter improves capacity retention. Furthermore, P doping also expands the thickness of the Li slab within the NCMA lattice, which facilitates lithium ion diffusion and significantly enhances rate capability. Under a current of 0.5 C, P-doped NCMA exhibits a high initial capacity of 198.4 mAh·g−1 with an exceptional capacity retention of 93.7% after 100 cycles. Even at a high rate of 5 C, it still delivers a discharge capacity of 162.2 mAh·g−1. These promoted performances indicate the high potential of P-doped NCMA as a candidate cathode material for high-energy-density battery systems.

Protective behavior of phosphonate-functionalized imidazolium ionic liquid and its impact on the Li-ion battery performance

The commercial lithium-ion batteries (LIBs) rely on lithium hexafluorophosphate (LiPF6), which is extremely sensitive to moisture and liable to thermal decomposition. Lithium bis (trifluoro methane sulfonyl) imide (LiTFSI), as a promising electrolyte salt, possesses high thermal stability and excellent moisture tolerance. However, LiTFSI is closely related to severe corrosion of the aluminum (Al) current collector at high voltage. Herein, phosphonate-functionalized imidazolium ionic liquid (PFIL) is developed and utilized as an electrolyte co-solvent to inhibit the oxidative dissolution of the Al current collector. PFIL can suppress Al corrosion by participating in the interface reaction and forming a stable and reliable protective film on the surface of Al foils, as confirmed by X-ray photoelectron spectroscopy. Thanks to the corrosion suppression of the Al current collector, the Li||LiNi0.8Mn0.1Co0.1O2 (NCM811) cells with PFIL-containing electrolytes exhibit better cycling performance and improved capacity retention. This work proposes an effective strategy for the advancement of high-voltage LIBs and contributes to promoting the widespread use of the sulfone imide-based lithium salts.

Addressing the Sluggish Kinetics of Sulfur Redox for High‐Energy Mg–S Batteries

AbstractA key challenge for practical magnesium–sulfur (Mg–S) batteries is to overcome the sluggish conversion kinetics of sulfur cathodes, achieving a high energy density and long‐lasting battery life. To address this issue, a doping strategy is demonstrated in a model Ketjenblack sulfur (KBS) cathode by introducing selenium with a high electronic conductivity. This leads to a significantly enhanced charge transfer in the resultant KBS1−xSex cathodes, giving rise to a higher S utilization and less polysulfide dissolution. Compared to the bare S cathode, the S‐Se composite cathodes exhibit a higher capacity, smaller overpotentials, and improved efficiency, serving as better benchmark compounds for high‐performance Mg–S batteries. First principles calculations reveal a charge transport mechanism via electron polaron diffusion in the redox end‐products, that enhances the reaction kinetics. By suppressing polysulfide dissolution in the electrolyte, the use of the KBS1−xSex cathodes also enables a more uniform anode reaction, and thereby significantly extends the cyclability of the cells. To improve the performance, further efforts are made by implementing a Mo6S8 modified separator into the cell. With an optimized cathode composition of KBS0.86Se0.14, the cell applying modified separator shows an improvement of capacity retention by >50% after 200 cycles.

Li2CO3 Nanocomposites as Cathode Lithium Replenishment Material for High-Energy-Density Li-Ion Batteries.

The irreversible capacity loss of lithium-ion batteries during initial cycling directly leads to a decrease in energy density, and promising lithium cathode replenishment can significantly alleviate this problem. In response to the problems of complex preparation, instability in air, and unfavorable residue of the conventional cathode lithium replenishment materials, a Li2CO3/carbon nanocomposite is prepared and utilized as the lithium replenishment material. With high-speed ball-milling, a nanocomposite with a tight embedment structured Li2CO3/Ketjen Black (KB) composite composed of nanosized Li2CO3 and KB is synthesized. The decomposition potential of Li2CO3 is effectively decreased to 3.8 V, and the amount of the active lithium ion being released is significantly increased, corresponding to a specific capacity of 645.2 mAh·g-1 during the initial charging cycle. It has been introduced into the full-cells composed of the NCM523 cathode and graphite anode, resulting in a capacity increase of 44 mAh·g-1 in the initial cycle and a 26.4% improvement in capacity retention over 100 cycles. The working mechanism of the Li2CO3/KB nanocomposite as the lithium replenishment agent has been discussed. The outcome of the work provides a practically feasible route to realize lithium-ion battery technology with improved energy density and cycling life.

Manipulating the Solvation Structure and Interface via a Bio-Based Green Additive for Highly Stable Zn Metal Anode.

The practical application of aqueous zinc-ion batteries (AZIBs) is limited by serious side reactions, such as the hydrogen evolution reaction and Zn dendrite growth. Here, the study proposes a novel adoption of a biodegradable electrolyte additive, γ-Valerolactone (GVL), with only 1vol.% addition (GVL-to-H2O volume ratio) to enable a stable Zn metal anode. The combination of experimental characterizations and theoretical calculations verifies that the green GVL additive can competitively engage the solvated structure of Zn2+ via replacing a H2O molecule from [Zn(H2O)6]2+, which can efficiently reduce the reactivity of water and inhibit the subsequent side reactions. Additionally, GVL molecules are preferentially adsorbed on the surface of Zn to regulate the uniform Zn deposition and suppress the Zn dendrite growth. Consequently, the Zn anode exhibits boosted stability with ultralong cycle lifespan (over 3500h) and high reversibility with 99.69% Coulombic efficiency. The Zn||MnO2 full batteries with ZnSO4-GVL electrolyte show a high capacity of 219 mAh g-1 at 0.5 A g-1 and improved capacity retention of 78% after 550 cycles. This work provides inspiration on bio-based electrolyte additives for aqueous battery chemistry and promotes the practical application of AZIBs.

Ultrathin, flexible and smooth carbon coating extends the cycle life of dual-ion batteries

The anion storage electrochemistry of carbon cathode is bottlenecked by the severe electrolyte decomposition and significant volume expansion. A surface coating that can impart simultaneous protection against all the drawbacks is challenging to achieve. Herein, the multifaceted benefits of pitch-derived soft carbon are leveraged as a coating layer. An upscalable annealing treatment results in an ultrathin, polycrystalline, uniformly distributed, and porous layer of carbonized pitch on the redox-active core. The coated material demonstrates 25 and 5.5% improvement in capacity retention, and coulombic efficiency, respectively, and a 150 mV reduction in voltage hysteresis. The smooth surface topography of the coated sample alleviates the electrolyte decomposition during high-voltage cycling. The mechanical flexibility of the coated material to withstand the volume change and to preserve the structural integrity are uncovered by the nanoindentation experiments and further supported by the post-cycling characterizations. The coating offers mechanochemical robustness to the interface and minimizes the growth of resistance. The strategy of soft carbon coating on anion-storing cathode can be extended to dual graphite full cells and other anion-storing chemistries irrespective of the anode and electrolyte.

Atomic pins bridging integrated surface to assist high-rate stability for Co-free Li-rich cathode

Li- and Mn-rich oxides (LMR) have emerged as promising cathode materials for next-generation Li-ion batteries due to their cost effectiveness, impressive capacity, and high energy density. However, the poor electrochemical kinetics and structural instability in hostile interface environments have result in continuous voltage/capacity decay and undesirable rate performance, impeding the large-scale commercial application of LMR materials. In this study, we introduce an atomic pins-assisted integrated surface reconstruction (AISR) strategy to address the interfacial degradation and instability issues. Utilizing the bidirectional diffusion effect of the aluminum-containing intermediate layer during the heat treatment process, we employ aluminum atoms as bridging centers to in situ construct a composite interface structure. This approach capitalizes on the element diffusion reaction and anchoring effect to achieve multifunctional modification through the Al-based ionic conductor network constructing and near-surface Al doping for LMR material. Intriguingly multiple kinetic investigations and calculations reveal that the epitaxial ionic conductor layer suppresses interfacial side reactions, enhances ionic conductivity, and improves electronic conductivity by regulating cationic/anionic redox activity through Al surface doping.Impressively, the modified electrodes exhibited an increased reversible capacity at both 0.1C/5C rates (0.1C, 2 ∼ 4.8 V, from 264.2 mAh∙g−1 to 274 mAh∙g−1; 5C, 2 ∼ 4.6 V, from 145.5 mAh∙g−1 to 197.9 mAh∙g−1) and improved capacity retention after 250 cycles at 1C/5C rates (2 ∼ 4.6 V: 1C, from 69.46% to 81.92%; 5C from 57.73% to 81.35%). We systematically summarized the rate-dependent failure mechanism and the corresponding integrated interface reconstruction principle. These key findings offer valuable insights for the development of high-energy–density and long-life lithium-ion batteries in commercial applications.

Synergistic effects of low - level magnesium and chromium doping on the electrochemical performance of LiNiO2 cathodes

LiNiO2 cathode materials with magnesium and chromium doping were prepared using a simple low - cost and efficient co - precipitation and lithiation procedure. During this procedure, both magnesium and chromium form a concentrated core particle, unto which nickel hydroxide precipitates. During lithiation, the elements in question will redistribute themselves and form a homogenous mixture. Magnesium - containing materials exhibit an excellent electrochemical performance, due to phase stabilizing effects, while for chromium - containing materials, performance remains poor. Rietveld refinement reveals that there is a possible upper limit for Mg doping (~ 2.5 mol %) as a pilar dopant. Washing of the lithiated materials was explored, and it is proposed that this can improve capacity retention in prolonged cycling. However, the inevitable loss of lithium from the surface layer remains a challenge. Two sources for the chromium facilitated capacity decay are proposed, both owing to the highly irreversible redox reaction of hexavalent chromium possibly blocking lithium pathways.

Stable Low-Temperature Al Batteries Enabled by Integrating Polydopamine-Derived N-Doped Carbon Nanospheres With Flake Graphite.

The battery performance declines significantly in severely cold areas, especially discharge capacity and cycle life, which is the most significant pain point for new energy consumers. To address this issue and improve the low-temperature characteristic of aluminum-ion batteries, in this work, polydopamine-derived N-doped carbon nanospheres are utilized to modify the most promising graphite material. More active sites are introduced into graphite, more ion transport channels are provided, and improved ionic conductivity is achieved in a low-temperature environment. Due to the synergistic effect of the three factors, the ion diffusion resistance is significantly reduced and the diffusion coefficient of aluminum complex ions in the active material become larger at low temperatures. Therefore, the battery delivers an improved capacity retention rate from 23% to 60% at -20 °C and excellent ultra-long cycling stability over 5500 cycles at -10 °C. This provides a novel strategy for constructing low-temperature aluminum-ion batteries with high energy density, which is conducive to promoting the practicality of aluminum-ion batteries.

Postprocessing of solution-cast polyaniline for enhanced electrochemical properties

Commercially available solutions of polyaniline (PANI) stabilized with dinonylnaphthalene sulfonic acid (DNNSA) offer a convenient means of forming PANI films via solution casting that are of interest for energy storage and other electrochemical applications. Here, we study the electrochemical charge storage properties of 200–400 nm thick PANI films cast from PANI-DNNSA solutions before and after postprocessing steps. As-cast PANI-DNNSA films exhibit a specific capacitance of <20 F/g at a 50 mV/s sweep rate, which increases to >300 F/g after p-toluene sulfonic acid:butanol (pTSA:BuOH) and dibromopropane (PrBr2) treatments. Crosslinked PANI also exhibits a 25% improvement in capacity retention over un-crosslinked PANI after 500 charge/discharge cycles. The capacity, energy, and power of postprocessed PANI films is examined in a symmetric coin cell device, and the utility of soluble PANI is demonstrated by coating planar and porous substrates using spin coating, drop casting, and dip coating techniques. These studies inform the use of PANI-DNNSA to fabricate high-capacity electrochemical devices.