Slurry Casting Research Articles

PRODUCTION TECHNOLOGY OF RADIO-TRANSPARENT CERAMIC MATERIALS

Ceramic radiotransparent materials are non-metallic materials that ensure the transmission of electromagnetic radiation in the radio frequency range of 105–1012 Hz with minimal dielectric losses in the operating temperature range (tgδ 10-2–10-5, ε < 10) and a low value of the radio wave reflection coefficient (P < 1 %). Ceramic radiotransparent materials are used to create rocket and aircraft fairings that protect antenna systems from external factors. For the synthesis of radiotransparent ceramic materials, it is expedient and promising to use such crystalline phases as celsian (BaAl2Si2O8) and slawsonite (SrAl2Si2O8) due to their low dielectric constant and dielectric loss tangent, as well as rather high thermal stability and melting point compared to other aluminosilicate compounds (mullite, spodumene, cordierite, etc.). The development of technology for obtaining radio-transparent ceramic antenna fairings and elements of protective structures of antenna systems of aviation facilities based on the BaO (SrO) – Al2O3 – SiO2 system is relevant. For the formation of complex profile ceramic radiotransparent materials slurry casting in porous gypsum molds is used. In order to compare the developed ceramic compositions, the physico-mechanical, dielectric and electrodynamic properties were studied under normal conditions and in the millimeter frequency range (26-38 GHz). As a result of the research, the following have been developed: a technology for the production of ceramic radiotransparent materials based on slawsonite by semi-dry pressing method, based on celsian-slawsonite by slip casting method and based on celsian or slawsonite by slip casting method. It has been established that the developed materials meet the technical requirements for radio-transparent ceramic materials and can be used to produce elements of protective structures of antenna equipment, such as nose fairings for aircraft.

Dry-printing outdoes slurry casting

Dry-printing outdoes slurry casting

Application of polypropylene carbonate for the tape casting of silicon nitride ceramics

AbstractQPAC40 (polypropylene carbonate), with a little decomposition residue, is commonly used as a binder in aluminum nitride (AlN) tape casting. In this paper, we tried to explore its application in silicon nitride (Si3N4) tape casting. By studying the influence of dispersant, binder, plasticizer/binder ratio, and solid loading on slurry and green tape properties, the optimum formulation of the tape casting of Si3N4 slurry was determined, and the green tape with a uniform structure and relative density up to 63.16% was prepared. Si3N4 ceramics were obtained by debinding at 600°C for 1 h in vacuum and gas‐pressure sintering at 1830°C for 2 h in N2. The thermal conductivity and flexural strength of Si3N4 ceramics were 56.28 ± 1.21 W/(m·K) and 1130.67 ± 23.58 MPa, respectively. These results indicated that QPAC40 can be used to prepare Si3N4 sheets through tape casting.

Manufacturing and structural control of slurry-cast catalyst layers for AEMFC

Fabrication of the catalyst layer (CL) in a cost-effective and scalable manner is a critical step toward commercialization of anion exchange membrane fuel cells (AEMFCs). Herein, we present a CL manufactured by slurry-casting that is compatible with the roll-to-roll process. Careful control of the rheological properties of the catalyst slurry enables casting onto a gas diffusion layer. The slurry cast CL features uniform thickness and well-developed mesoporous structure. By adjusting the solid content and ionomer-to-carbon ratio of the slurry, the pore structure and ionomer connectivity in the CL are controlled and the power performance is enhanced. This work suggests a practical strategy for mass production of the CL and extends the understanding of the structure–property relationship for slurry-cast CLs.

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Solvent-free lithium iron phosphate cathode fabrication with fibrillation of polytetrafluoroethylene

Fabricating electrode for lithium-ion batteries (LiBs) with solvent-free (SF) procedure can save energy and improve electrochemical performance simultaneously. Polymer fibrillation is one of the most promising SF procedures due to its feasibility for upscale production. The hardness of lithium iron phosphate (LFP) impedes its SF fabrication with polytetrafluoroethylene (PTFE) fibrillation. In this study, we successfully expanded PTFE fibrillation for SF LFP electrode fabrication with the help of carbon nanotubes (CNTs). CNTs increase the conductivity of electrode, and act as matrix for LFP particles to ensure relative displacement to further fibrillate PTFE to form self-supporting electrode film when the dry mixture was hot rolled. The SF LFP/hard carbon full cells were fabricated and demonstrated comparable electrochemical performance to slurry casting (SC) fabricated LFP electrode. The initial coulombic efficiency (ICE) of full cell increased to more than 95% after prelithiation.

Influence of particle content and temperature on dry sliding wear behavior of rice husk ash reinforced AA6061 slurry cast aluminum matrix composites

AA6061 aluminum matrix composites (AMCs) reinforced rice husk ash (RHA) particles (0–8 wt %) were produced. The sliding wear was assessed using a pin-on-disc wear apparatus with a heating facility, and the temperature was varied from 40 °C to 240 °C. The incorporation of RHA particles was beneficial in improving the wear resistance and reducing the COF values over the entire range of temperatures used. The increase in temperature deteriorated the wear resistance of the composites. AA6061/(0–4 wt %) RHA AMCs showed a clear transition from mild wear to severe wear at a temperature of 200 °C. The increase in RHA particle content increased the transition wear temperature. The wear mode changed from abrasive wear at 40 °C to adhesive material flow at 240 °C.

Solvent‐Free Manufacturing of Lithium‐Ion Battery Electrodes via Cold Plasma

Slurry casting has been used to fabricate lithium‐ion battery electrodes for decades, which involves toxic and expensive organic solvents followed by high‐cost vacuum drying and electrode calendering. This work presents a new manufacturing method using a nonthermal plasma to create inter‐particle binding without using any polymeric binding materials, enabling solvent‐free manufacturing electrodes with any electrochemistry of choice. The cold‐plasma‐coating technique enables fabricating electrodes with thickness (>200 μm), high mass loading (>30 mg cm−2), high peel strength, and the ability to print lithium‐ion batteries in an arbitrary geometry. This crosscutting, chemistry agnostic, platform technology would increase energy density, eliminate the use of solvents, vacuum drying, and calendering processes during production, and reduce manufacturing cost for current and future cell designs. Here, lithium iron phosphate and lithium cobalt oxide were used as examples to demonstrate the efficacy of the cold‐plasma‐coating technique. It is found that the mechanical peel strength of cold‐plasma‐coating‐manufactured lithium iron phosphate is over an order of magnitude higher than that of slurry‐casted lithium iron phosphate electrodes. Full cells assembled with a graphite anode and the cold‐plasma‐coating‐lithium iron phosphate cathode offer highly reversible cycling performance with a capacity retention of 81.6% over 500 cycles. For the highly conductive cathode material lithium cobalt oxide, an areal capacity of 4.2 mAh cm−2 at 0.2 C is attained. We anticipate that this new, highly scalable manufacturing technique will redefine global lithium‐ion battery manufacturing providing significantly reduced plant footprints and material costs.

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

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

Full Cell Lithium‐Ion Battery Manufacture by Electrophoretic Deposition

AbstractElectrophoretic deposition (EPD) is a proven coating operation at an industrial scale. Initially designed for the automotive industry, it has expanded to other applications, notably ceramic coatings for surface protection, and has found promising application in the battery industry. Whilst fundamental half‐cell studies of EPD electrodes are numerous, their practical performance at full‐cell level is largely unknown. This study reports full‐cell lithium‐ion batteries in which anode and cathode are manufactured by EPD, using an exemplary Li4Ti5O12/LiFePO4 (LTO/LFP) chemistry. Investigations compatible with industry scalability were carried out including a) formulation of colloidal electrolytes for large area electrode manufacture, b) optimisation of EPD parameters providing high coating thickness and mass loading, c) comparison with slurry cast electrodes, d) scaling investigations to prototype large area pouch cells, and e) ease of manufacture with porous current collectors for high power applications. It was found that the practical performance of EPD electrodes outperformed slurry casting in various categories including lower resistances, more extractable capacity, higher power capability and stable cycling robustness.

Thermal Properties of Porous Mullite Ceramics Modified with Microsized ZrO2 and WO3.

Mullite ceramics are well known as materials with a high temperature stability, strength and creep resistance. In this research, the effect of a modification with magnesia-stabilized zirconia and yttria-stabilized zirconia, separately, as well as in a mixture with WO3, in 1:1 and 1:2 ratios on the thermal properties of porous mullite ceramics was investigated. The porous mullite-containing ceramics were prepared by a slip casting of the concentrated slurry of raw materials with the addition of a suspension of Al paste for the pore formation due to the H2 evolution as a result of the reaction of Al with water. The formed samples were sintered at 1600 °C and the holding time was 1 h. The materials were characterized using X-ray diffractometry, scanning electron microscopy, mercury porosimetry, the laser flash contactless method, thermal shock resistance testing and the non-destructive impulse excitation method for determining the elasticity modulus. The modification of the porous mullite ceramic with a mixture of ZrO2 and WO3 oxides had a positive effect by decreasing the thermal conductivity, due to the increased porosity, in comparison to the undoped samples and samples with only ZrO2. The doubling of the WO3 amount in the modifying oxide mixtures improved the ceramic thermal shock resistance. The porous mullite ceramics which were modified with magnesia-stabilized zirconia (2.8 mol% MgO) and WO3 had a lower thermal conductivity and improved thermal shock resistance than the samples with yttria-stabilized zirconia (8 mol% Y2O3) and WO3.

Low Cost, Solvent-Free Lithium-Ion Battery Electrode Manufacturing Based on Electrostatic Dry Powder Coating

Conventional industrial processes for the manufacture of Lithium-Ion Battery (LIB) electrodes are costly and not environmentally friendly. The state-of-the-art slurry casting technique utilizes a large amount of toxic N-methly pyrollidinone (NMP), necessitating significant energy and capital costs associated with electrode drying and solvent recovery.Electrostatic Dry Powder Deposition (EDPD) is well established in many industries as an effective method of achieving well-adhered and uniform coatings of controlled thickness & composition. Recently, a small number of studies have demonstrated the viability of EDPD in LIB electrode manufacture, achieving cell capacities similar to, or exceeding, those from slurry casting. Crucially, this approach eliminates the need for solvent usage. Nevertheless, several challenges remain before EDPD can be adopted within the LIB industry. In particular, achieving adequate dispersion of powder materials and a level of adhesion sufficient for use in standard roll-2-roll lines.With the goal of developing & demonstrating the viability of the EDPD process, this work will present a solvent-free approach, coupled with innovative methods to improve adhesion and overall coating quality. The high voltage spinel cathode Lithium Nickel Manganese Oxide (LNMO) was utilized as a demonstrator material, as it can provide high energy density cells without the use of expensive and rare cobalt. Results will include: (a) development of EDPD equipment and appropriate process parameters, (b) optimization of coating formulation, (c) adhesion enhancement through through the use of in-situ heating and post-deposition treatments, (d) electrochemical analysis of EDPD electrodes and benefits compared with slurry casting, (e) full process cost analysis. The presentation will conclude with a discussion of the potential of this new manufacturing technique to disrupt the LIB industry.Rechargeable lithium-ion batteries (LIBs) are ubiquitous in mostly every electronic device. However, the process of manufacturing LIBs is costly and not environmentally friendly. State of the art LIB electrode manufacturing is carried out using slurry casting. A mixture of active material (most commonly containing Cobalt), a binder and a conductive additive are mixed with a solvent and cast onto a substrate. This process is energy-intensive and requires significant capital for drying equipment and processes and the recovery of toxic solvents, such as N-methyl pyrrolidone (NMP).Utilising an EDPD process with a Cobalt free active material such as LNMO in place of the slurry casting process would eliminate the need to use toxic solvents, thereby significantly reducing the manufacturing time and cost. Additionally, LNMO can work as a replacement for the next-generation lithium-ion battery Cobalt-free cathode materials due to its high lithiation/delithiation potential, > 4.5 V compared with 3 – 4 V in the case of more conventional cathode material.The EDPD process presented has demonstrated that a reduction in cost of over 35% can be achieved when tested with LNMO, polyvinylidene fluoride (PVDF) as binder and Carbon Black (CB) as a conductive additive, by eliminating the use of NMP and Cobalt from the process. This is based on a comparison carried out with 1kg of active material mix. There are challenges associated with dry powder electro manufacture for LIBs, such as achieving good adhesion, tortuosity, and obtaining an even dispersion and thickness of the coating. This work addresses these challenges and develops an innovative dry powder deposition method assisted with a low power laser to improve adhesion in a scalable manner.Using a combination of EDPD, low heat and low power laser as an enhancement for the adhesion process in electrode manufacture create an innovative opportunity to remove the toxic solvents to achieve good dry powder depositions making the process less energy demanding and more environmentally friendly. The present research will focus on how to produce dry electrodes with electrostatic coating manufacture, the process innovation of adding a Laser to improve the adhesion and electrochemical testing to quantify the LIB's performance when using this approach.Early research has shown that the manufactured electrodes have similar capacity retention and improved rate capability in lithium-ion batteries when compared to the current state of the art of slurry casting. The simple process operation offers flexibility in scalable production and modularity for future development and commercial implementation.

Molten Hydroxide Electrodeposition of Transition Metal Oxide Cathodes for Electrochemical Energy Storage

State-of-the-art synthesis for layered oxide cathodes for Li and Na-ion battery involves prolonged high temperature (>700°C) multistep processing for long reaction times (~24 hours) under high oxygen pressure, followed by slurry casting after mixing with binders and additives. Here, we demonstrate an intermediate temperature (250-350°C) molten hydroxide-based electrodeposition process to grow alkali ion (Li+, Na+) intercalated transition metal oxides across multiple transition metal chemistries of the Li system (from layered LiCoO2 to cobalt-less orthorhombic LiMnO2, layered Li2MnO3, spinel LiNixMn1-xO4, LiMn2O4,) and Na system (O3 and P2 NaxCoO2, O’3 NaxMnO2) in thick film form factors. The highly textured ([110]||ND), dense (>95%) electroplated LiCoO2 cathodes can perform at ultrahigh thickness of ~200 µm (areal capacity ~13.6 mAh/cm2) in comparison to 40-60 µm for state-of-the-art slurry cast cathodes (areal capacity ~3-4 mAh/cm2 with a porosity of ~20%), a fivefold increase in areal capacity and volumetric energy density. We discuss the interplay of bulk crystallographic orientation of the electro-active material (LiCoO2), surface terminating planes interacting with the electrolyte, and electrochemically grown conformal surface protective layers on the electrochemical-chemo-mechanical degradation mechanisms during intercalation and deintercalation for high voltage operation (>4.2 V vs. Li). We also demonstrate electrochemically controllable isovalent transition metal doping and substitution in ceramic oxides (LiCoxMn1-xO2) by electrodeposition. Our findings highlight the influence of the unique molten hydroxide-based solution chemistry platform and electrochemical processing parameters, on regulating the phase assemblage, designing the microstructure, and controlling crystallographic orientation during electrocrystallization.

Morphological & Structural Control of Electrodeposited Sb Anodes through Solution Additives and Their Influence on Electrochemical Performance in Na-Ion Batteries

Alloy-based materials such as antimony (Sb) are of interest for both Li/Na-ion batteries due to their theoretical capacity and electronic conductivity. Of the various ways to fabricate Sb films (slurry casting, sputtering, etc.) one promising route is through the use of electrodeposition. Electrodeposition is an industrially relevant synthetic technique that allows for the use of solution additives to control different characteristics such as film uniformity, morphology, and electrical conductivity. Solution additives such as cetyltrimethylammonium bromide (CTAB) and bis-(3-sulfopropyl) disulfide (SPS) have been used to control characteristics such as particle morphology, and electrical conductivity in various applications but have not been applied to the electrodeposition of Sb for battery applications. In this study, Sb films were electrodeposited with various concentrations of CTAB and SPS and the structure, morphology, composition, and electrochemical performance in Na-ion batteries were compared. We report that CTAB and SPS additives can significantly influence electrodeposited Sb films by altering the morphology and reducing the crystallinity of the Sb films, affecting the electrochemical performance. These studies provide valuable insight into the tunability of alloy-based films through electrodeposition and solution additives.

Development of Large Area All Solid-State Lithium-Ion Cells Using Scalable and Manufacturable Coating Processes

The NREL team has fabricated all solid-state full cells with sulfide-based electrolytes using fabrication techniques suitable for high speed/low-cost manufacturing, such as slurry and tape casting. Slurry coating is a well-established and cost-effective process feasible for large scale/continuous process (e.g., roll-to-roll processing). However, most solid-state cells fabricated to date have been small area (1 cm2) cells with single mAh capacities. These cells are generally fabricated by dry mixing of powders and compressing layers to hundreds of MPa up to GPa of pressure and high temperatures to condense powders into a coin-cell size battery. The use of such high pressures is not suitable for large-scale manufacturing. Further, the separator layer in this configuration is often prohibitively thick (hundreds of microns) resulting in poor rate capability and low energy density. NREL has demonstrated ability to cast thin (100 micron) electrically isolating sulfide-based separator layers and composite solid-state cathodes. Functioning large-area cells (30 cm2) have been fabricated by punching out sections of cast layers to make cells tested at modest pressures. The chemical reactivity of sulfide-based electrolytes with solvents for casting and active cathode oxide materials (NMC, NCA, etc.) is particularly challenging. Figure below shows all solid-state cathode (left) and anode/argyrodite separator (right) having dimensions of 5X6 cm. The anode, cathode, and separator all use a chloride argyrodite electrolyte (Li6PS5Cl). The anode active material is graphite and cathode is alumina coated NMA with high specific capacity (> 200 mAh/g). Initial performance testing will be shared. Figure 1

(Industrial Electrochemistry and Electrochemical Engineering Division H. H. Dow Memorial Student Achievement Award) Electrochemically Grown Highly Textured Thick Ceramic Oxide Films for Energy Storage: A New Manufacturing Paradigm for Cathode Materials

Electrochemical synthesis of materials has contributed to significant breakthroughs in materials processing by replacing high temperature, cost and energy intensive pyrometallurgical processes. Noteworthy examples include aluminum extraction by Hall–Heroult process, electrowinning of copper, titanium extraction through the Kroll process, electrolytic production of steel, and electrochemical synthesis of cement. Increasing the energy and power density of alkali ion intercalated transition metal oxide cathodes which power electric cars and portable electronics, has been a growing topic of global techno-economic interest. Our work demonstrates a direct electrodeposition of thick ternary ceramic oxide films as an alternate scalable manufacturing technique for fabrication of binder-and-additive free cathode materials for secondary battery. Employing an intermediate temperature (200-400°C) molten hydroxide-based electrodeposition method, a general electrochemical growth strategy for multiple Li and Na ion cathode chemistries is demonstrated for the first time including NaCoO2, NaMnO2, LiCoO2, Li2MnO3, LiMnO2, LiMn2O4, (A. Patra, P.V. Braun et. al, PNAS, 2021) in a thick (> 50 µm) thick film form factor. In-plane and through-plane texture can be electrochemically architectured in LiCoO2 and NaCoO2 films across multiple textures: <003>||ND (Li/Na ion blocking sites parallel to the normal direction), <101>||ND, <104>||ND, <110>||ND (fast lithium ion conducting sites parallel to the normal direction). An accurate control of crystallization dynamics leads to highly anisotropic, grain boundary engineered structure with low tortuosity and fastest electron and Li ion conducting pathways (<110>||ND) oriented normal to the current collector. The highly textured (<110>||ND), dense (>95%) electroplated cathodes can perform even at ultrahigh thickness of ~ 200 µm (areal capacity of ~13.6 mAh/cm2) in comparison to 40-60 µm for conventional slurry cast cathodes (areal capacity of ~3-4 mAh/cm2 with a porosity of ~10-20%), a fivefold increase in areal capacity and volumetric energy density (A. Patra, P.V. Braun et. al, to be submitted). In order to enable a high voltage (> 4.5 V vs. Li) cathode design, a functionally graded architecture is also demonstrated with a core capable of providing high-capacity and rate capability (LCO <110>||ND); and multiple capping layers (LCO <003>||ND and Li2MnO3) to suppress harmful side reactions occurring at voltages beyond the normal operation range (beyond 4.2 V vs. Li). Our work paves the way towards an electrosynthesis platform for functional oxides with the ability to generate micron scale ordering with controllable in-and-through-plane orientation in thick ceramic oxide films important for electrochemical energy storage.

Single Step Electrochemical Recovery and Regeneration of Cathode Materials

Sustainable battery production is a major challenge for the future of electrification. The rise in battery usage, particularly in portable electronics and electric vehicles, has led to a massive increase in the demand for critical battery materials. However, global supply has already begun to strain under the increased demand and projections predict that the global demand could easily surpass global supply in a matter of decades.Current battery recycling and recovery techniques for battery components involve multistep regenerative processes through either pyrometallurgical, hydrometallurgical, or direct recycling methods route. Our work demonstrates for the first time, the dissolution and electrochemical deposition of transition metal oxides in the same solvent for sustainable battery material usage and recovery for slurry cast and electroplated Li-ion battery cathodes. Ultra-dense, high-performing, binder and additive free cathodes are formed at the end of the recycling process.This discovery generates high quality energy dense battery cathodes from “end-of-life” batteries and paves the way towards a simplified recycling conditions for more sustainable battery production.

Aluminum hydroxide, bayerite, boehmite, and gibbsite ToF-SIMS spectra in the negative ion mode. I

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed for boehmite (AOH-60) and its potential products of oxidation including pseudo-boehmite (AOH-180), α- and γ-Al2O3, and α- and γ-Al(OH)3. Since boehmite is often incorporated on cladding materials to prevent corrosion, surface analysis techniques are performed to determine the amount of oxidation present. This ToF-SIMS spectral library is of significance because it includes boehmite and its potential oxidation products (i.e., aluminum oxide and hydroxide), which can be used to compare to spectra obtained for real-world samples containing boehmite. Furthermore, ToF-SIMS is often used as a complementary technique to x-ray photoelectron spectroscopy due to its surface sensitivity and ability to compare spectra via a multivariate analysis, therefore establishing that the molecular signatures of boehmite and relevant compounds are essential for peak identification. The SIMS spectra shown are acquired from commercially available powders, which were deposited onto a silicon wafer substrate via liquid slurry drop casting. This library of SIMS mass spectra will serve as a comparison of boehmite [γ-AlO(OH)], pseudo-boehmite [AlOOH⋅nH2O], α- and γ-aluminum oxide [Al2O3], and α- and γ-aluminum hydroxide [Al(OH)3] in the negative ion mode, which compliments those reported in the positive ion mode {Part II [L. Strange et al., Surf. Sci. Spec. 29, 025002 (2022)]}.

Aluminum hydroxide, bayerite, boehmite, and gibbsite ToF-SIMS spectra in the positive ion mode. II

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed for boehmite (AOH-60) and its potential products of oxidation including pseudo-boehmite (AOH-180), α- and γ-Al2O3, and α- and γ-Al(OH)3. Since boehmite often forms on cladding materials to prevent corrosion, surface analysis techniques are performed to determine the amount of oxidation present. This ToF-SIMS spectral library is of significance because it includes boehmite and its potential oxidation products (i.e., aluminum oxide and hydroxide), which can be used to compare to spectra obtained for real-world samples containing boehmite. Furthermore, ToF-SIMS is often used as a complementary technique to x-ray photoelectron spectroscopy due to its surface sensitivity and ability to compare spectra via a multivariate analysis, therefore establishing that the molecular signatures of boehmite and relevant compounds are essential for peak identification. The SIMS spectra shown are acquired from commercially available powders, which were deposited onto a silicon wafer substrate via liquid slurry drop casting. This library of SIMS mass spectra will serve as a comparison of boehmite [γ-AlO(OH)], pseudo-boehmite [AlOOH⋅nH2O], α- and γ-aluminum oxide [Al2O3], and α- and γ-aluminum hydroxide [Al(OH)3] in the positive ion mode, which compliments those reported in the negative ion mode {Part I [L. Strange et al., Surf. Sci. Spectra 29(2), 025001 (2022)]}.

Polymer-Garnet-Based Composite Cathodes for Solid-State Li Batteries

All-solid-state lithium batteries (ASSLBs) can potentially outperform conventional Li-ion batteries with liquid or polymer electrolyte. One example for solid electrolytes is the garnet-type oxide Li7La3Zr2O12 (LLZO). LLZO has a wide electrochemical window, stability vs. lithium, and good ionic conductivity at room temperature. The cathode in ASSLBs is manufactured from a cathode active material (CAM), such as LiCoO2 (LCO). The efficiency of Li-ion storage can be improved by the use of a composite cathode consisting from a CAM and an ion-conducting ceramic, e.g. LCO/LLZO. In such a composite cathode, LLZO delivers Li-ions through the whole bulk enhancing the volumetric loading of LCO. In this work the addition of polymer electrolyte into LCO/LLZO composite cathode was proposed, aiming at further increase of cell performance due to facilitation of CAM usage, similar to the approach of manufacturing of polymer-ceramic electrolytes. They are fabricated mostly by tape casting of slurry with polymer matrix, ceramic filler and a solvent. An alternative technology includes free sintering of tape-casted LCO/LLZO porous network and subsequent infiltration by liquid or polymer electrolyte. Free sintering of LCO/LLZO composite requires relatively high temperature and/or long sintering time. This results in loss of volatile Li with decrease in electrochemical performance.In the present work the LCO/LLZO composite cathode was manufactured in a powder-based process by Field-Assisted Sintering Technique also known as Spark Plasma Sintering (FAST/SPS). Fast heating (100°C/min and higher) and application of mechanical pressure during FAST/SPS enable reduction of sintering temperature and processing time needed for fabrication of nearly-fully-dense composite.[1] Thereby, Li evaporation and grain growth can be significantly reduced. This technology was used in our previous work for fabrication of half-cells with dense LLZO electrolyte and dense LCO/LLZO composite cathode. However, the appearance of side phase after sintering at low pressure and a residual porosity was observed. The reason for that was partial reduction of oxides by carbon originated from graphite foil in FAST/SPS setup. In the presented work, the graphite foil was replaced by carbon-free mica foil. This measure enabled FAST/SPS sintering of porous LCO/LLZO network without side phase formation. The obtained porous skeleton was infiltrated with polymer electrolyte to fabricate a polymer-ceramic composite cathode. The cathode was assembled with an anodic half-cell consisting of dense FAST/SPS-sintered LLZO electrolyte and attached indium (In) foil used as anode. The ASSLB with polymer-ceramic composite cathode showed significantly lower interfacial impedance and remarkably higher area-specific storage capacity as compared to the similar ASSLBs with pure ceramic (porous or dense) composite cathodes. Thus, the functionality and the advanced storage capacity of the proposed polymer-ceramic cathode and related ASSLB architecture were demonstrated.[2]