Corrosion Of Current Collectors Research Articles

Study of the Corrosion Behavior of Cathode Current Collector in LiFSI Electrolyte.

Cycling aging is the one of the main reasons affecting the lifetime of lithium-ion batteries and the contribution of aluminum current collector corrosion to the ageing is not fully recognized. In general, aluminum is corrosion resistant to electrolyte since a non-permeable surface film of alumina is naturally formed. However, corrosion of aluminum current collector can still occur under certain conditions such as lithium bis(fluorosulfonyl)imide (LiFSI)-based electrolyte or high voltage. Herein, we investigates the corrosion of aluminum current collector in the electrolyte of 1.2 M LiFSI in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed solvents. The electrochemical results shows that the corrosion current of aluminum is enhanced by cycling time and potential, which is correlated with the surface species and morphology. The formation of AlF3, which is induced by deep penetration of F- anions through surface passivation film, leads to internal volume change and the surface crack in the end. Our work will be inspiring for future development of high-energy-density and high-power-density lithium-ion batteries in which the LiFSI salt will be intensively used.

Side Reactions/Changes in Lithium-Ion Batteries: Mechanisms and Strategies for Creating Safer and Better Batteries.

Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and over-discharge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components.

Interfacial Insights into the Polarization Protocol: Toward Reducing Corrosion and Improving the Cycle Life of Electrochemical Capacitors.

The number of scientific publications on the impact of corrosion on current collectors on the working parameters of electrochemical capacitors is very limited. The aim of current research is to search for new, environmentally friendly chemical power sources and energy storage devices and to improve existing ones. Therefore, this article presents a simple and effective way to improve the life of a symmetric electrochemical capacitor by changing the direction of electrode polarization, which in turn inhibits the corrosion of the current collector. This slows the degradation of current collectors of positive electrode over long durations. However, activated carbon electrode corrosion also occurs. Experiments on capacitors with stainless steel and gold current collectors indicate that the lifespan of the latter is much longer than that of the former. Therefore, current collector corrosion has a distinct and detrimental impact on electrochemical capacitor operation. Moreover, the research results indicate that carbon corrosion results from current collector corrosive damage.

The Role of Current Collector Corrosion on the Performance of Thermal Batteries

As a bridge connecting external circuits and electrodes, current collectors are critical for battery performance. While numerous studies have investigated lithium-ion battery current collectors at room temperature, fewer address high-temperature batteries (>500 °C). The interfacial properties of thermal battery collector and cathode at high temperatures remain unclear, and collector selection is more empirical. In this paper, the effects of 304 stainless steel on the discharge performance of NiS2 cathode were investigated. At 500 °C, 100 mA cm−2 and 1.5 V cutoff voltage, NiS2 first-voltage plateau specific capacity with 304 stainless steel current collector exhibits a high specific capacity of 320 mAh g−1 and total specific capacity of 700 mAh g−1, 146% and 17% higher than Ni, respectively. The Ni current collector of the thermal battery underwent severe chemical reactions at high operating temperatures, consuming active mass and increasing interfacial impedance. In contrast, stainless steel formed an iron-chromium sulfide passivation layer inhibiting further chemical reactions and accelerating charge transfer rate at the interface, resulting in effective increase in the discharge capacity of the thermal battery. This study provides theoretical guidance for selecting current collectors for thermal batteries based on high-temperature chemical reactions.

Insights into Corrosion of Current Collectors for Magnesium Batteries

To enable the shift towards renewable energy, the use of low-cost energy storage systems is necessary. Magnesium (Mg) is an abundant and safer raw material than lithium for electrochemical energy storage systems such as batteries, due to its reduced sensitivity to air. Promising intercalation materials for cathodes include Chevrel phase Mo6S8 and Prussian green FeFe(CN)6. Although magnesium perchlorate-based electrolytes are practical for early-stage cathode research, they are not compatible with Mg metal due to corrosion. The organo-metallic all phenyl complex (APC) based electrolyte is a potential candidate for magnesium full cells, but both systems contain reactive chloride species that cause severe corrosion of the current collector.This study utilizes linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy to identify suitable materials for current collectors, including carbon-coated Al and Ni. The selected materials must withstand a polarization potential of 2 V vs. Mg/Mg2+. A Graphite-based current collector is shown to be the most promising candidate due to its low areal density, which can increase the energy density of practical Mg batteries.

Towards Moisture Tolerant Lithium-Ion Batteries: A Systematic Investigation on the Effect of Moisture on Ni-Rich NMC Cathodes

In the ever-expanding lithium-ion battery (LIB) industry, lithium hexafluorophosphate (LiPF6) has been the most dominant lithium salt for preparing electrolytes. However, the challenges related to its moisture sensitivity (manifested by the formation of hydrofluoric acid) and thermal instability are yet to be addressed. Due to its improved ionic conductivity, reduced risk of producing hydrofluoric acid and better thermal and chemical stability, Lithium bis(fluorosulfonyl)imide (LiFSI) has been considered as a potential alternative salt to replace LiPF6. Nonetheless, LiFSI salt is currently not available in volumes relevant to industrial production; hindered by its high cost and the presence of trace quantities of chloride impurities. In addition, for operating cells at upper cut off voltages higher than 4.1~4.2 V, oxidative aluminum current collector corrosion [1] is a challenge.Among the high energy density LIB cathode materials, Nickel-rich LiNixMnyCozO2 (NMCs) are the most promising choices to fulfil the long mileage per charge requirements for powering electric vehicles [2]. In this study, the effect of moisture on the electrochemical performance of NMC622/Li and NMC622/graphite pouch cells was systematically investigated by adding water into 1 M LiFSI electrolyte. To better understand the interaction and effect of the added H2O with other electrolyte additives such as fluoroethylene carbonate (FEC), the electrochemical performance of the NMC622/Li half cells were tested with four different electrolytes; 1 M LiFSI in EC/DMC (50/50, v/v, control), 1 M LiFSI + 1000 ppm water, 1 M LiFSI + 10 wt% FEC, and 1 M LiFSI + 1000 ppm water + 10 wt% FEC. Double layered ultra-high molecular weight polyethylene separator (Solupor 3P07B) was used in all measurements. The water content in the electrolytes with 1000 ppm water was regularly monitored using the Karl-Fisher titration technique.It is intriguing that the addition of 1000 ppm water into the 1 M LiFSI electrolyte improved the specific discharge capacity and capacity retention of the NMC622/Li pouch cells. Furthermore, to investigate the morphological, microstructural, and chemical evolutions of the electrodes after short- and long-term cycling performance tests, postmortem characterizations such as ex situ XRD, S(T)EM, SEM/EDS, FTIR and XPS are being conducted.As expected, the oxidative aluminum current collector corrosion was scrutinized by running cyclic voltammetric measurements with the different electrolytes and the results were compared with that in 1 M LiPF6 (Figure 1a). It should be noted, however, that the voltammograms are obtained in the voltage range of 3.0 – 4.9 V. Ex situ SEM images of the cycled aluminum electrodes exhibited the formation of a thin film on the surface (Figure 1b, 1c), and the film formed on the aluminum electrode cycled with 10 wt% FEC was thicker compared to those with 1 M LiFSI and 1 M LiFSI + 1000 ppm H2O electrolytes. It was evident from the oxidative aluminum corrosion study that the current density and pitting corrosion were relatively smaller in the 10 wt% FEC containing electrolytes (Figure 1a). This is in agreement with the formation of relatively thicker films on the electrode surface with FEC containing electrolytes, as discussed above.Overall, it was evident from this study that addition of 1000 ppm water enhanced the discharge capacity and capacity retention of NMC622/Li pouch cells, and such moisture tolerant LiFSI based lithium-ion batteries can open new pathways which can ultimately enable the development of relatively higher dew point and less energy intensive dry rooms. However, for cell operations above ca. 4.3 V, proper prevention mechanisms are required for the oxidative aluminum current collector corrosion in such systems.

Study of the coating effect of mildly oxidized graphene on aluminium current collectors by electrophoretic deposition and drop-casting methods for Li-ion battery application

Preventing current collector corrosion is critical in Li-ion batteries. This study investigates mildly oxidized graphene (MGO) coating on aluminium (Al) foil for corrosion resistance and battery performance for the first time. Electrophoretic deposition (EPD) and drop-casting are used to apply this coating. Polarization tests and SEM analysis are performed on coatings to determine the optimal EPD conditions. Optimal conditions for EPD of MGO on aluminium are 5 V and 40 s. Using LiNi0.8Co0.15Al0.05O2 (NCA) cathodes, the performance of cells on MGO-coated and uncoated aluminium (Bare-Al) is evaluated. EPD sample shows a capacity of 175 mAh/g at C/2, 35 mAh/g more than the Bare-Al sample despite a 67.3 Ω increase in charge transfer resistance (Rct). Due to inadequate adhesion, the drop-casted sample displays a 136 mAh/g capacity at C/2, poor rate capability, and higher Rct (335.48 Ω). MGO-coated aluminium batteries perform better under the EPD method because of improved corrosion resistance of current collectors, as demonstrated by reduced corrosion currents in the polarization curves and reduced conductivity losses in incremental capacity (ICA) results.

Electrolyte Engineering Empowers Li||CFx Batteries to Achieve High Energy Density and Low Self‐Discharge at Harsh Conditions

AbstractGiven its exceptional theoretical energy density (over 2000 Wh kg−1), lithium||carbon fluoride (Li||CFx) battery has garnered global attention. N‐methylpyrrolidone (NMP)‐based electrolyte is regarded as one promising candidate for tremendously enhancing the energy density of Li||CFx battery, provided self‐discharge challenges can be resolved. This study successfully achieves a low self‐discharge (LSD) and desirable electrochemical performance in Li||CFx batteries at high temperatures by utilizing NMP as the solvent and incorporating additional ingredients, including vinylene carbonate additive, as well as the dual‐salt systems formed by LiBF4 with three different Li salts, namely lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and LiNO3. The experimental results unfold that the proposed methods not only minimize aluminum current collector corrosion, but also effectively passivate the Li metal anode. Among them, LiNO3 exhibits the most pronounced effect that achieves an energy density of ≈2400 Wh kg−1 at a current density of 10 mA g−1 at 30 °C, nearly 0% capacity‐fade rate after 300 h of storage at 60 °C, and the capability to maintain a stable open‐circuit voltage over 4000 h. This work provides a distinctive perspective on how to realize both high energy density and LSD rates at high temperature of Li||CFx battery.

Strategies towards inhibition of aluminum current collector corrosion in lithium batteries

Aluminum (Al) foil, serving as the predominant current collector for cathode materials in lithium batteries, is still unsatisfactory in meeting the increasing energy density demand of rechargeable energy storage systems due to its severe corrosion under high voltages. Such Al corrosion may cause delamination of cathodes, increasement of internal resistance, and catalysis of electrolyte decomposition, thus leading to premature failure of batteries. Hence, a systematic understanding of the corrosion mechanisms and effective anticorrosion strategies are necessary to enhance overall performance of lithium batteries. In this review, the corrosive mechanisms related to Al current collectors are systematically summarized and clarified. In addition, an overview on recent progress and advancement of strategies toward inhibiting Al corrosion is presented. In the end, we also provide a perspective with motivation to stimulate new ideas and research directions to further inhibit Al corrosion to achieve high energy density, long cycle life, and high safety of lithium batteries.

Potassium-based dual-carbon battery with pure ionic liquid electrolyte

Dual-carbon batteries (DCBs) have attracted considerable attention as they are environmentally friendly, economical, and exhibit a high cost-to-performance ratio. However, severe electrolyte decomposition and Al current collector corrosion lead to moderate reversible capacity and low average coulombic efficiency in DCBs, limiting their practical application. This paper reports a potassium-based DCB using a pure ionic liquid (IL) electrolyte with asymmetric FTA− anions (FTA = (fluorosulfonyl)(trifluoromethylsulfonyl)amide) and graphite electrodes, with a high charge–discharge capacity and long cycle-life. ILs are intrinsically highly concentrated electrolytes composed of cations and anions that enable the construction of high energy density DCBs. Here, symmetric dual-carbon full cells with the FTA-based IL electrolyte and graphite positive and negative electrodes delivered a high discharge capacity of 81 mAh g−1 with an average discharge voltage of ∼4.35 V up to 300 cycles. Further, ex-situ X-ray diffraction measurements conducted at 298 K indicated the formation of stage 1 FTA-graphite intercalation compounds at the full-charged state. This study facilitates the construction of cost-effective DCBs with a high operating voltage, fast charge–discharge, and long cycling, without the use of toxic metals.

Enabling Aqueous Processing of Ni-Rich Layered Oxide Cathode Materials by Using Lithium Sulphate as Processing Additive

Roughly 75% of the cost for Lithium ion batteries are attributed to material cost for electrodes, electrolyte and separator. Furthermore, the production cost of the cathode material is responsible for >50% of the overall material cost. Therefore, technological breakthroughs for an increased energy density and decreased production cost along the whole battery value chain are urgently needed. State of the art (SOTA) cathode active materials (CAMs) are LiFePO4 (LFP) and layered oxides such as LiNi1-x-yCoxMnyO2 (NCM). By increasing the Ni content within NCM materials, the discharge capacity and therefore the energy density on material level can be gradually increased. Since a higher Ni content (>80% Ni) in NCM´s implicitly entails several challenges with respect to the material synthesis procedure, stability during electrode processing as well as life time, the broad commercialization of these CAMs still needs further advances.Aqueous processing of Ni-rich layered oxide cathode materials is a promising approach to simultaneously decrease electrode manufacturing costs, while bringing environmental benefits by substituting the SOTA, often toxic and expensive organic processing solvents. Furthermore, recycling of batteries and especially of the cathode material, will probably become an important topic in the coming years. The conversion of electrodes into black mass might be cheaper and easier for aqueously-processed cathodes (e.g., by using fluorine-free binders). However, an aqueous environment still remains challenging due to the high reactivity of Ni-rich layered oxides towards moisture, leading to surface reconstruction, lithium leaching and Al current collector corrosion due to the resulting high pH value of the aqueous electrode paste. Common approaches to suppress current collector corrosion are the protection of the Al current collector by a carbon coating or decreasing the pH value by using dilute acids. The latter approach, especially with phosphoric acid, might lead to formation of a phosphate coating at the surface of cathode particles, which is able to protect the NCM against further degradation.Herein, we present a facile method to enable aqueous processing of LiNi0.8Co0.1Mn0.1O2 (NCM811) by the addition of lithium sulphate (Li2SO4) during electrode paste dispersion. The aqueously-processed electrodes retain 80% of their initial capacity after 400 cycles in NCM811 || graphite full-cells, while electrodes processed without the addition of Li2SO4 reach 80% of their capacity after only 200 cycles. Furthermore, with regard to electrochemical performance, aqueously-processed electrodes using carbon-coated Al current collector outperform reference electrodes, based on SOTA production processes involving N-methyl-2-pyrrolidone as processing solvent and fluorinated binders. The positive impact on cycle life by the addition of Li2SO4 stems from a formed sulphate coating, protecting the NCM811 surface against degradation. Results reported herein open a new avenue for the processing of Ni-rich NCM electrodes using more sustainable aqueous routes. Figure 1

The Many Deaths of Supercapacitors: Degradation, Aging, and Performance Fading

AbstractHigh‐performance electrochemical applications have expedited the research in high‐power devices. As such, supercapacitors, including electrical double‐layer capacitors (EDLCs) and pseudocapacitors, have gained significant attention due to their high power density, long cycle life, and fast charging capabilities. Yet, no device lasts forever. It is essential to understand the mechanisms behind performance degradation and aging so that these bottlenecks can be addressed and tailored solutions can be developed. Herein, the factors contributing to the aging and degradation of supercapacitors, including electrode materials, electrolytes, and other aspects of the system, such as pore blocking, electrode compositions, functional groups, and corrosion of current collectors are examined. The monitoring and characterizing of the performance degradation of supercapacitors, including electrochemical methods, in situ, and ex situ techniques are explored. In addition, the degradation mechanisms of different types of electrolytes and electrode materials and the effects of aging from an industrial application standpoint are analyzed. Next, how electrode degradations and electrolyte decompositions can lead to failure, and pore blocking, electrode composition, and other factors that affect the device's lifespan are examined. Finally, the future directions and challenges for reducing supercapacitors' performance degradation, including developing new materials and methods for characterizing and monitoring the devices are summarized.

Sodium Nitrate/Formamide Deep Eutectic Solvent as Flame‐Retardant and Anticorrosive Electrolyte Enabling 2.6 V Safe Supercapacitors with Long Cyclic Stability

Safe operation of electrochemical capacitors (supercapacitors) is hindered by the flammability of commercial organic electrolytes. Non‐flammable Water‐in‐Salt (WIS) electrolytes are promising alternatives; however, they are plagued by the limited operation voltage window (typically ≤2.3 V) and inherent corrosion of current collectors. Herein, a novel deep eutectic solvent (DES)‐based electrolyte which uses formamide (FMD) as hydrogen‐bond donor and sodium nitrate (NaNO3) as hydrogen‐bond acceptor is demonstrated. The electrolyte exhibits the wide electrochemical stability window (3.14 V), high electrical conductivity (14.01 mS cm−1), good flame‐retardance, anticorrosive property, and ultralow cost (7% of the commercial electrolyte and 2% of WIS). Raman spectroscopy and Density Functional Theory calculations reveal that the hydrogen bonds between the FMD molecules and ions are primarily responsible for the superior stability and conductivity. The developed NaNO3/FMD‐based coin cell supercapacitor is among the best‐performing state‐of‐art DES and WIS devices, evidenced by the high voltage window (2.6 V), outstanding energy and power densities (22.77 Wh kg−1 at 630 W kg−1 and 17.37 kW kg−1 at 12.55 Wh kg−1), ultralong cyclic stability (86% after 30 000 cycles), and negligible current collector corrosion. The NaNO3/FMD industry adoption potential is demonstrated by fabricating 100 F pouch cell supercapacitors using commercial aluminum current collectors.

Electrolyte Design Strategies for Non-Aqueous High-Voltage Potassium-Based Batteries

High-voltage potassium-based batteries are promising alternatives for lithium-ion batteries as next-generation energy storage devices. The stability and reversibility of such systems depend largely on the properties of the corresponding electrolytes. This review first presents major challenges for high-voltage electrolytes, such as electrolyte decomposition, parasitic side reactions, and current collector corrosion. Then, the state-of-the-art modification strategies for traditional ester and ether-based organic electrolytes are scrutinized and discussed, including high concentration, localized high concentration/weakly solvating strategy, multi-ion strategy, and addition of high-voltage additives. Besides, research advances of other promising electrolyte systems, such as potassium-based ionic liquids and solid-state-electrolytes are also summarized. Finally, prospective future research directions are proposed to further enhance the oxidative stability and non-corrosiveness of electrolytes for high-voltage potassium batteries.

Enabling Aqueous Processing of Ni-Rich Layered Oxide Cathode Materials by Addition of Lithium Sulfate.

Aqueous processing of Ni-rich layered oxide cathode materials is a promising approach to simultaneously decrease electrode manufacturing costs, while bringing environmental benefits by substituting the state-of-the-art (often toxic and costly) organic processing solvents. However, an aqueous environment remains challenging due to the high reactivity of Ni-rich layered oxides towards moisture, leading to lithium leaching and Al current collector corrosion because of the resulting high pH value of the aqueous electrode paste. Herein, a facile method was developed to enable aqueous processing of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) by the addition of lithium sulfate (Li2 SO4 ) during electrode paste dispersion. The aqueously processed electrodes retained 80 % of their initial capacity after 400 cycles in NCM811||graphite full cells, while electrodes processed without the addition of Li2 SO4 reached 80 % of their capacity after only 200 cycles. Furthermore, with regard to electrochemical performance, aqueously processed electrodes using carbon-coated Al current collector outperformed reference electrodes based on state-of-the-art production processes involving N-methyl-2-pyrrolidone as processing solvent and fluorinated binders. The positive impact on cycle life by the addition of Li2 SO4 stemmed from a formed sulfate coating as well as different surface species, protecting the NCM811 surface against degradation. Results reported herein open a new avenue for the processing of Ni-rich NCM electrodes using more sustainable aqueous routes.

Insights into Electrolytic Pre-Lithiation: A Thorough Analysis Using Silicon Thin Film Anodes.

Pre-lithiation via electrolysis, herein defined as electrolytic pre-lithiation, using cost-efficient electrolytes based on lithium chloride (LiCl), is successfully demonstrated as a proof-of-concept for enabling lithium-ion battery full-cells with high silicon content negative electrodes. An electrolyte for pre-lithiation based on γ-butyrolactone and LiCl is optimized using boron-containing additives (lithium bis(oxalato)borate, lithium difluoro(oxalate)borate) and CO2 with respect to the formation of a protective solid electrolyte interphase (SEI) on silicon thin films as model electrodes. Reversible lithiation in Si||Li metal cells is demonstrated with Coulombic efficiencies (CEff ) of 95-96% for optimized electrolytes comparable to 1 m LiPF6 /EC:EMC 3:7. Formation of an effective SEI is shown by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). electrolytic pre-lithiation experiments show that notable amounts of the gaseous product Cl2 dissolve in the electrolyte leading to a self-discharge Cl2 /Cl- shuttle mechanism between the electrodes lowering pre-lithiation efficiency and causing current collector corrosion. However, no significant degradation of the Si active material and the SEI due to contact with elemental chlorine is found by SEM, impedance, and XPS. In NCM111||Si full-cells, the capacity retention in the 100th cycle can be significantly increased from 54% to 78% by electrolytic pre-lithiation, compared to reference cells without pre-lithiation of Si.

Binder Effect on Electrochemical Performance of Silicon Anodes

Binder is a crucial component of high-capacity silicon anodes. It allows the active material to cohere to itself and surrounding materials. In the past few years, there have been divergent conclusions on the cell performance of anodes using water-based PAA vs. LiOH-PAA binder [1-3]. While there is agreement that LiOH-PAA facilitates the coating process, cell performance between these two binders is not settled.The difference in cell performance may be due to the pH value or the extra Li+ in the binder, both of which change when LiOH is added to PAA. In this work we examined these two factors separately to determine their effect on cell performance. Our hypothesis is that the extra Li+ could facilitate ion transfer and the low pH could affect current collector corrosion and silicon oxidation. NH3(aq) is used to adjust the binder slurry pH and experimental results are compared between NH3-PAA and LiOH-PAA electrodes otherwise made with the same pH value. Similarly, we compared performance of NH3-PAA anodes with different pH values.Multiple experiments were done to compare aspects of cell performance. Overall electrochemical performance was examined by cell cycling. Ionic conductivity was determined by an impedance test. Contact resistances to the current collector were measured with an apparatus developed in our lab. Silicon oxidation state was determined by XRD. Morphology of the anode can be compared by SEM.In our cycling results silicon half cells with LiOH-PAA binder had a 10% higher capacity than those with PAA binder (Fig. 1), all other factors being constant. And the LiOH-PAA film had a lower impedance value which confirms the hypothesis that extra Li+ could facilitate ion transfer. The PAA anode had a lower contact resistance to the current collector than did the LiOH-PAA anode. This result agrees with Xiong’s work [3], which claims that the corrosion of current collector when using PAA slurry could form a more rigid coating surface and thus lead to the surface cracking and lower the capacity. Other parts of this work including cycling performance and XRD are still in progress and will be reported. Hays, K.A., et al., Journal of Power Sources, 2018. 384: p. 136-144. Hu, B., et al., Journal of Power Sources, 2019. 416: p. 125-131. Xiong, J., et al., ACS Applied Materials & Interfaces, 2021. 13(24): p. 28304-28323. Figure 1

Important Impact of the Slurry Mixing Speed on Water-Processed Li4Ti5O12 Lithium-Ion Anodes in the Presence of H3PO4 as the Processing Additive.

The aqueous processing of lithium transition metal oxides into battery electrodes is attracting a lot of attention as it would allow for avoiding the use of harmful N-methyl-2-pyrrolidone (NMP) from the cell fabrication process and, thus, render it more sustainable. The addition of slurry additives, for instance phosphoric acid (PA), has been proven to be highly effective for overcoming the corresponding challenges such as aluminum current collector corrosion and stabilization of the active material particle. Herein, a comprehensive investigation of the effect of the ball-milling speed on the effectiveness of PA as a slurry additive is reported using Li4Ti5O12 (LTO) as an exemplary lithium transition metal oxide. Interestingly, at elevated ball-milling speeds, rod-shaped lithium phosphate particles are formed, which remain absent at lower ball-milling speeds. A detailed surface characterization by means of SEM, EDX, HRTEM, STEM-EDX, XPS, and EIS revealed that in the latter case, a thin protective phosphate layer is formed on the LTO particles, leading to an improved electrochemical performance. As a result, the corresponding lithium-ion cells comprising LTO anodes and LiNi0.5Mn0.3Co0.2O2 (NMC532) cathodes reveal greater long-term cycling stability and higher capacity retention after more than 800 cycles. This superior performance originates from the less resistive electrode-electrolyte interphase evolving upon cycling, owing to the interface-stabilizing effect of the lithium phosphate coating formed during electrode preparation. The results highlight the importance of commonly neglected─frequently not even reported─electrode preparation parameters.

An Integrated Design of Electrodes for Flexible Dual-Ion Batteries.

Due to the widespread employment of carbon materials in novel dual-ion batteries (DIBs) with high energy density, they possess the potential for large-scale energy storage and are inexpensive and environmentally friendly. However, drawbacks such as Al current collector corrosion and significant self-weight, as well as lithium metal abuse and poor deposition reversibility, impair the energy density and cycle performance of lithium-graphite DIBs (Li-G DIBs), severely limiting their application potential. Therefore, an integrated electrode structure design was proposed. That is, the flexible graphite and single-walled carbon nanotubes (SWCNTs) composite cathode (GSC), which is light-weight and self-supporting, and the self-supporting lithium metal anode, which is loaded on the flexible carbon cloth (CC) derived from waste mask (Li@CC), were prepared. Not only were the impacts of current collector corrosion and active material exfoliation avoided on the electrochemical performance, but the areal loading of Li metal was also regulated and its reversibility of deposition enhanced. At a current density of 200 mA g-1 , the constructed Li@CC//GSC full cell could release a specific capacity of 100.5 mAh g-1 , and the capacity retention rate after 300 cycles was greater than 80 %. Moreover, the fabricated flexible Li@CC//GSC full cell is not only recyclable and produces less environmental pollution but also has potential applications in wearable devices.

Alkaline hydrogel electrolyte from biosourced chitosan to enhance the rate capability and energy density of carbon-based supercapacitors

A green biodegradable hydrogel electrolyte was developed from chitosan biopolymer and KOH. This allows one to increase the energy density of carbon-based supercapacitors and to prevent the electrode degradation and current collector corrosion.