Lithium Polyacrylate Research Articles

Functional Separator with Poly(Acrylic Acid)-Enabled Li2CO3-Free Garnet Coating for Long-Cycling Lithium Metal Batteries.

Lithium metal batteries (LMBs) possess a theoretical energy density far surpassing that of commercial lithium-ion batteries (LIBs), positioning them as one of the most promising next-generation energy storage systems. Modifying separators with composite coatings comprising oxide solid-state electrolyte (SSE) particles and polymers can improve the cycling stability and safety of LMBs. However, exposure to air forms Li2CO3 on oxide SSE particles, diminishing their ion flux regulation at the electrode/electrolyte interface. Utilizing the reaction of Li2CO3 with polyacrylic acid (PAA) to form lithium polyacrylate (LiPAA), an ultra-thin composite coating on polyethylene (PE) separator with Li2CO3-free Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles and LiPAA binder is fabricated in one step. The exposed Li2CO3-free LLZTO surface increases the ionic conductivity and lithium ion (Li+) transference number of the functional separator, resulting in small resistance and uniform Li deposition of the Li metal anode. Consequently, the Li//LiCoO2 cell with the functional separator exhibits a significantly improved life of 980 cycles with 80.9% capacity retention under lean-electrolyte conditions. Both the Li//LiCoO2 coin cell and pouch cell using thin Li foil anode demonstrate good cycling stability and high mechanical robustness. This study provides a green and scalable approach for fabricating advanced separators for LMBs.

Silicon Anodes for Lithium‐Ion Batteries Based on a New Polyimide Binder

AbstractSilicon is a promising candidate for replacing graphite in anodes for advanced Li‐ion batteries due to its high theoretical gravimetric energy density. However, silicon as an active anode material suffers from significant volume changes upon lithiation/delithiation, causing fast capacity fading. The performance of silicon anodes depends on the polymeric binders used, which form well‐bound Si particles matrices that accommodate the strains developed during their repeated lithiation, thus maintaining their integrity.

Development of an in situ polymerized artificial layer for dendrite‐free and stable lithium metal batteries

AbstractSevere lithium dendrite issues bring a significant challenge for the practical application of Li metal anodes. In this study, a scalable spray‐coating method is used to in situ construct an organic/inorganic composite interfacial layer including Li‐Zn alloy and lithium polyacrylate on the surface of lithium metal. The Li‐Zn alloy exhibits favorable lithiophilic and high Li+ diffusion coefficient, whereas highly elastic lithium polyacrylate is a Li+ conductor and provides excellent mechanical properties. Finally, the ZA‐Li||ZA‐Li cell shows stable cycling for over 1800 h with 1 mA cm−2 at 2 h per cycle, which demonstrates a pronounced inhibition of lithium dendrite growth. Based on the above merits, this work would open a new avenue to develop advanced artificial interfacial layer with multiple capabilities for high‐performance lithium metal batteries.

New exploration of water-soluble lithium polyacrylate/xanthan gum composite binder for Li-rich Mn-based cathode materials

Li-rich Mn-based oxides are considered promising cathode materials of Li-ion batteries with high specific capacity and operating voltage. However, Li-rich materials suffer from a high initial irreversible capacity loss and severe voltage attenuation during cycling. In this work, lithium polyacrylate (LiPAA) was crosslinked with xanthan gum (XG) to form a water-soluble binder for Li[Li0.2Co0.13Ni0.13Mn0.54]O2 electrode. The capacity retention was 78.3 % after 100 cycles at 0.2 C. LiPAA provided additional Li+ ions during cycling, while XG firmly bound to the surface of the active particles. Cost-effective binders provide a facile mean to improve the electrochemical performance of Li-rich cathode materials.

Li-Zn alloy patch for defect-free polymer interface film enables excellent protection effect towards stable Li metal anode

Constructing a smart polymer film with favorable lithium (Li) transport capability and mechanical flexibility for suppressing Li dendrite growth is an effective strategy. Unfortunately, the porosity and the swelling of the polymer membrane cannot completely prevent liquid electrolyte from sweeping through the artificial protection film, severely deteriorating the cyclic performance. Herein, we propose a defect-free hybrid film that consists of Li+ conductive lithium polyacrylate (LiPAA) polymer interface layer and Li-Zn alloy patch to tackle the critical problems of traditional polymer composite passivation film. The pinhole leaks of the polymer matrix are self-filled by Li-Zn alloy patches, enhancing the integrity of LiPAA film. Consequently, a defect-free hybrid film is nailed flat against the Li metal anode, exhibiting extraordinary stability in the liquid electrolyte and enabling perfect protection effect. This facile strategy produces a promising anode for next generation Li batteries.

Simple construction of multistage stable silicon-graphite nanosheets composites for lithium-ion batteries

Silicon/carbon composites are considered as the preferred anode materials for high energy density lithium-ion batteries due to their high capacity. However, the high cost of raw materials and the complex preparation process have resulted in expensive cost and poor batch stability of silicon-carbon materials, which have impeded their widespread adoption on a large scale. In this study, a multistage stable silicon-graphite nanosheets composite (Si-NSs/G-NSs@C) with intercalated and core-shell structure was produced from low-cost precursors of silicon nanosheets (Si-NSs) and graphite nanosheets (G-NSs) by simple modification-grafting-coating and heat treatment processes. Benefiting from the effective bonding, citric acid carbon coating, intercalation and core-shell structure, the Si-NSs/G-NSs@C composite exhibits excellent performance for lithium storage. The Si-NSs/G-NSs@C electrode, using the sodium alginate binder system, displays the reversible specific capacity of 821.4 mAh g−1 at 400 mA g−1, with the capacity retention rate of 80% after 200 cycles. When employing lithium polyacrylate as the binder, the composite electrode demonstrates the reversible specific capacities of 1048.9 mAh g−1 at 400 mA g−1 and 723.6 mAh g−1 at 1000 mA g−1. After 200 cycles, the capacity retention rates were 81% and 85%, respectively. In summary, the low-cost precursors, simple and controllable preparation process and excellent electrochemical performance will further promote the market application of silicon/carbon anode materials.

Lithium Polyacrylate as Lithium and Carbon Source in the Synthesis of Li3 VO4 for High-Rate and Long-Life Li-Ion Batteries.

Li3 VO4 is a promising anode material for use in lithium-ion batteries, however, the conventional synthesis methods for Li3 VO4 anodes involve the separate use of lithium and carbon sources, resulting in inefficient contact and low crystalline quality. Herein, lithium polyacrylate (LiPAA) was utilized as a dual-functional source and an in-situ polymerization followed by a spray-drying method was employed to synthesize Li3 VO4 . LiPAA serves a dual purpose, acting as both a lithium source to improve the crystal process and a carbon source to confine the particle size within a desired volume during high-temperature treatment. Additionally, the in-situ synthesis of a porous carbon decorating skeleton prevents the growth and agglomeration of Li3 VO4 particles and provides abundant ion/electron diffusion channels and contact areas. Based on the synthesis route and the constructed primary-secondary structure, the Li3 VO4 anodes obtained in this study exhibit an impressive capacity of 596.2 mAh g-1 . Moreover, they demonstrate enhanced rate performance over 600 cycles during 10 periods of rate testing, as well as a remarkably long lifespan of 5000 cycles at high currents. The utilization of LiPAA as a dual-functional source represents a broad approach that holds great potential for future research on high-performance electrodes requiring both lithium and carbon sources.

In Situ Formation of Lithium Polyacrylate Binder for Aqueous Manufacturing and Recycling of Ni-Rich Cathodes

Water has now become the standard process solvent for graphite-based anodes, eliminating the use of toxic and costly N-Methyl-pyrrolidone (NMP) in anode manufacturing. Ideally, water could also become the standard for cathodes; however, water-based processing of NMC cathode materials induces lithium leaching, which reduces their specific capacity and leads to capacity fade. Here, we demonstrate that leached lithium ions can be exploited during aqueous slurry preparation to create a Li-containing polymer binder that enables cathode performance comparable to those fabricated using NMP. Specifically, we show that leached lithium ions from LiNi0.8Mn0.1Co0.1O2 (NMC 811) particles react with polyacrylic acid (PAA) to form a lithium polyacrylate (LPA) surface coating and binder. Because the resulting LPA binder is water soluble, aqueous-based recycling of the cathode particles is feasible and over 90% capacity retention is shown in recycled material after 100 cycles.

Investigation of Lithium Polyacrylate Binders for Aqueous Processing of Ni-Rich Lithium Layered Oxide Cathodes for Lithium-Ion Batteries.

Ni‐rich layered oxide cathodes are promising candidates to satisfy the increasing energy demand of lithium‐ion batteries for automotive applications. Aqueous processing of such materials, although desirable to reduce costs and improve sustainability, remains challenging due to the Li+/H+ exchange upon contact with water, resulting in a pH increase and corrosion of the aluminum current collector. Herein, an example was given for tuning the properties of aqueous LiNi0.83Co0.12Mn0.05O2 electrode pastes using a lithium polyacrylate‐based binder to find the “sweet spot” for processing parameters and electrochemical performance. Polyacrylic acid was partially neutralized to balance high initial capacity, good cycling stability, and the prevention of aluminum corrosion. Optimized LiOH/polyacrylic acid ratios in water were identified, showing comparable cycling performance to electrodes processed with polyvinylidene difluoride requiring toxic N‐methyl‐2‐pyrrolidone as solvent. This work gives an exemplary study for tuning aqueous electrode pastes properties aiming towards a more environmentally friendly processing of Ni‐rich cathodes.

Multifunctional Composite Binder for Thick High-Voltage Cathodes in Lithium-Ion Batteries.

High-voltage LiNi0.5Mn1.5O4 (LNMO) spinel offers high specific energy and good rate capability with relatively low raw-material cost due to cobalt-free and manganese-rich chemical compositions. Also, increasing mass loading (mg/cm2) by thickening cathodes has been one of the focused areas to greatly improve the energy density of lithium-ion batteries (LIBs) at the cell level. The LNMO cathode made with a polyvinylidene fluoride (PVdF) binder, however, suffers from an oxidative decomposition of liquid electrolytes and cathode delamination from a current collector. This problem is exacerbated with an increase in thickness. In this study, we developed a lithium polyacrylate (LiPAA)-sodium alginate (Na-Alg) composite binder series that offer positive multifunctions such as enhancing cathode adhesion and cohesion, improving cycle life, creating an effective passivating layer at the cathode-electrolyte interface (CEI), and lowering cell impedance. Comprehensive design of systematic experiments revealed a close chemo-mechano-electrochemical relationship in the thick high-voltage cathodes. Among the various binder compositions, the LiPAA (30 wt %)-Na-Alg (70 wt %) binder offered a strong adhesion property and positive multifunctions at the CEI layer, which consequently stabilized the solid-electrolyte interfacial (SEI) layer on the graphite anode and improved LIB performances. This novel composite binder will be applicable to various types of thick cathodes in future studies.

LiPAA with Short‐chain Anion Facilitating Li2Sx (x ≤ 4) Reduction in Lean‐electrolyte Lithium–sulfur Battery

Lean electrolyte usage in lithium–sulfur battery (LSB) meets the demand of the high energy density. However, lean condition makes the electrolyte‐related interface discrete, leading to retardation of ion transfer that depends on interfaces. Consequently, electrochemical reactions face restraint. Herein, lithium polyacrylate acid (LiPAA) with short‐chain anions (molecular weight of 2000) is introduced into the cathode. Because of the polysulfide (PS)‐philic instinct of the short‐chain PAA anions, short‐chain PS is captured inside of the cathode. In addition, LiPAA supplies Li+ to the short‐chain PS captured. The strong interaction between Li2S4 and LiPAA effectively decreases Li2S4 migration to the anode during discharging. In a sense, the ion mass transfer pattern is thus changed comparing to traditional long‐way mode between cathode and anode. Galvanostatic intermittent titration technique (GITT) proves that the interfacial reaction resistance is greatly decreased in the region where Li2Sx (x ≤ 4) reduction contributes most. In the same time, the reversibility of electrochemical reduction/oxidation is improved. Owing to the accelerated Li2Sx (x ≤ 4) reduction, Li implanting of only 0.3 wt.% plus O introduction up to 1.4 wt.% enables the LSB perform well even with 1/4 of regular electrolyte dosage (5 μL mg−1) and high‐sulfur loading (4.2 mg cm−2), increasing its rate capacity C0.8/0.5 from 52.6% (without the LiPAA) to 92.3% (with the LiPAA) as well as a capacity of 518.7 mAh g−1 after 400 cycles at 0.8 mA cm−2.

(Invited) Spectroscopic and Microscopic Characterizations of Silicon-Electrolyte Interfacial Chemistry and Silicon-Based Electrode Aging Behaviors

Due to inherent properties of the silicon (Si)-electrolyte interphase (SEI)—complexity, high reactivity and continuous evolution—it remains a poorly understood topic in advanced Si-based Li-ion battery (LiB) research,1,2 and its detailed and real-time analysis is a great challenge. Vibrational spectroscopy, such as Raman and Fourier-transform infrared spectroscopy (FTIR), is one of the most important analytical tools for understanding and quantifying the interfacial chemical reactions. These techniques are used extensively by the battery community in their ex situ form, but developing in situ variants of these techniques and combing in situ analyses from both techniques can provide new insight and help to elucidate the mechanism of interfacial failure in battery systems. We have optimized in situ vibrational spectroscopy methods that show reproducible and stable performance over multiple cycles in terms of both electrochemistry and spectroscopy, which enables us to monitor the surface chemistry and evolution of the SEI. This is essential to gaining a better understanding of the electrochemical performance of Si-based LiBs.3-5 Further, the reactions leading to SEI growth and evolution in Si-based LiBs may be more comprehensively probed by monitoring changes in the gas and liquid phases. To this end, we are developing novel in situ gas chromatography (GC) techniques, which may be applied to both coin-type cells and larger-format pouch cells. Using custom cell designs, we track the evolution of electrolyte and degradation species in the gaseous and liquid6 phases at various stages of battery cycling. We achieve both qualitative identification and quantification through coupled mass-spectrometry (MS) and flame ionization detection (FID). This GC-MS-FID analysis complements our in situ vibrational spectroscopy studies, providing a true multi-modal and multi-phase approach to SEI analysis. Taken together, these studies can provide an in-depth understanding of the underlying chemistry and physics and mechanical explanation of various reactions/interactions within the SEI, thus enabling the rational design of electrolytes and electrodes to stabilize the SEI.Additionally, we have developed advanced techniques to assess the structural and electronic properties of Si-based composite electrodes. Comprehensive characterization of pristine and cycled composite electrode architectures is complicated by several inherent properties. During battery operation, Si-based composite electrodes experience localized lithiation and reaction rates due to heterogeneous conditions and distributions of electrode components. Further, (electro)chemical and structural properties continuously evolve during cycling. Finally, the nanoscale diameter of particles falls beneath the lateral and depth resolution of most laboratory-based instruments. To address these challenges, we have utilized scanning spreading resistance microscopy (SSRM) to image the three-dimensional nanostructure of composite anodes via contrast in the electronic properties of the distinct components.7 Specifically, Si-based composite anode components, such as SiOx nanoparticles, graphite, carbon black, and lithium polyacrylate binder, are all readily distinguished by their intrinsic electronic properties, with measured electronic resistivity closely matching known material properties. In combination with scanning electron microscopy/energy dispersive X-ray (SEM-EDX) and electron energy loss spectroscopy (EELS), we expect to compare the electrical, chemical and structural changes of Si-based composite electrodes before and after cycling. This can provide a fundamental understanding of localized degradation mechanisms, which informs our understanding of SEI formation and evolution. This technique may also be applied to assess heterogeneous aging within the electrode, and is more broadly applicable to other battery systems. In particular, it may be used to better understand particle dispersion, localized lithiation, electrolyte-electrode interphase formation/evolution, and degradation processes in composite electrodes for the development of next-generation batteries.

Three-Dimensional Mapping of Cycling Changes in Silicon-Graphite Composite Anodes Via Scanning Probe Microscopy

Silicon (Si) anodes have the potential to greatly improve the energy density of lithium-ion batteries due to the greater specific capacity of Si relative to standard graphite (Gr) anodes (1). However, Si anode implementation is limited by issues such as volumetric expansion during cycling and an unstable solid-electrolyte interphase (SEI). Composite anodes with Si and Gr particles can increase capacity while mitigating Si anode degradation. However, these electrodes can be challenging to characterize (and therefore optimize) due to their multiple components, heterogeneous surfaces, and the complex processes occurring there. Scanning spreading resistance microscopy (SSRM) is a form of scanning probe microscopy that measures local resistivity in a sample. By removing material with the probe tip while measuring resistivity, three-dimensional resistivity maps can be determined (2). For Si-Gr composite anodes, the different resistivities of the electrode components (e.g., Si, Gr, carbon, and lithium polyacrylate binder) allows direct identification through SSRM. 3D nanoscale volumes can then be created for both the whole electrode and the individual components.This presentation will demonstrate 3D SSRM mapping of pristine and cycled anodes with three compositions – Si, Gr, and Si-Gr. By comparing changes in the morphology, thickness, and resistivity in the active material and SEI in each single-component electrode, the component distribution and evolution of the Si-Gr composite anode is better understood. SSRM results will be compared to chemical analysis techniques such as scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and electron energy loss spectroscopy to verify the component identification and to correlate chemical composition to resistivity. These data will then be correlated to electrochemical performance and used to further the development of Si-Gr electrodes with enhanced performance. W.-J. Zhang, Journal of Power Sources, 196, 13 (2011). C. Stetson, Z. Huey, A. Downard, Z. Li, B. To, A. Zakutayev, C. S. Jiang, M. M. Al-Jassim, D. P. Finegan, S. D. Han and S. C. DeCaluwe, Nano Lett (2020). Figure 1

Inorganic Compounds as Binders for Si-Alloy Anodes

The inorganic compounds, lithium polysilicate (Li2Si5O11), sodium polyphosphate ((NaPO3)n), and lithium phosphate monobasic (H2LiPO4) were investigated as the sole binders in Si-alloy and graphite electrodes for Li cells. Surprisingly, the coating quality and cycling performance of Si-alloy anodes with these inorganic binders is similar to those electrodes using the state of the art lithium polyacrylate (LiPAA) organic binder. Graphite electrodes with inorganic binders show good cycling despite having poor coating quality. Graphite electrodes with lithium polysilicate binder have three times the binder volume than expected, indicating that this binder has an open framework microstructure.

Enhanced the mechanical strength of polyimide (PI) nanofiber separator via PAALi binder for lithium ion battery

Polyimide (PI) nanofiber membrane prepared by electrospinning technique exhibits poor mechanical strength for the slippage of fibers, which limits it applied into lithium ion battery (LIB). In this study, we are devoted to promoting the macro mechanical strength of PI nanofiber membrane by inhibiting the slippage among the fibers. Lithium polyacrylate (PAALi) is a kind of excellent binder, and it contributes to increasing the adhesion effect between the fibers. As a result, the PI nanofiber membrane treated by PAALi solution shows the mechanical strength of 16.1 MPa, higher than 5.0 MPa of pristine PI membrane. The introduction of this binder makes the originally loose and disordered PI nanofibers cross-link with each other and prevents from the slip between the fibers. Surprisingly, the PAALi binder has no effect on the thermal stability and electrochemical performance of PI nanofiber separator. Furthermore, these LiCoO2/Li cells using the modified PI nanofiber separators exhibit better cycling stability and superior rate performance compared with the cells containing pristine PI separators. It demonstrates that the use of PAALi binder is a promising method to improve the mechanical strength of nanofiber membrane, which gets it applied in the high-power LIB.

High‐Performance Al2O3/PAALi Composite Separator Prepared by Water‐Based Slurry for High‐Power Density Lithium‐Based Battery

The ceramic composite separator shows great thermal stability and electrolyte wettability compared with polyolefin separator, which is applied in the supply source of electric vehicles. However, the preparation of ceramic composite separator is involved with large amount of organic solvents, and it is of great harm to health. Herein, lithium polyacrylate (PAALi) is selected as a novel binder to prepare the Al2O3/PAALi ceramic composite separator by water‐based slurry. The production of Al2O3/PAALi composite separator is more environmental‐friendly, and it also exhibits excellent thermal stability. In addition, the Al2O3/PAALi composite separator has obviously improved lithium transference number of 0.41, compared with polyethylene (PE) separator and Al2O3/polyvinylidene fluoride (PVDF) composite separator. It can be attributed to the fact that PAALi with a lot of carboxyl (COO−) functional groups has an interaction with ions and facilitates the desolvation of cation. As a result, the LiCoO2/Li half cell using Al2O3/PAALi composite separator shows higher discharge capacity retention (88%) after 180 cycles and excellent cycling stability. Fortunately, these cells containing Al2O3/PAALi composite separator also have wonderful rate performance; even at 5 C, the discharge capacity retention still keeps 58%, higher than Al2O3/PVDF composite separator. Therefore, this is a promising method to further enhance the battery performance.

Silicon-Graphite Anode with High-Areal Capacity for Li-Ion Battery

Nowadays, researchers are increasingly interested in silicon active material for lithium-ion batteries, which could meet the ever-increasing demand for high energy density owing to their satisfactory theoretical capacity (~4200 mAh g-1). Nevertheless, replacing the commercial graphite totally with silicon is still insurmountable due to bottlenecks such as low loading level and unsatisfactory areal capacity. Therefore, in this work, we turned eyes back on improved graphite anode with modified silicon cooperation through a facile blending process. The nano/microporous silicon active mateiral with boron doping and carbon nanotube wedging (B-Si/CNT) exhibits stable electrochemical performance (88.2% retention after 200 cycles at 2000 mA g-1) and high reversible capacity (ca. 2400 mAh g-1). After graphite cooperation, the resultant B-Si/CNT-graphite composite could illustrate an areal capacity of 5.2 mAh cm-2 with a high mass loading (11.2 mg cm-2). Besides, the enhanced anode also demonstrates acceptable utilization in lithium ion full battery with 2 mol% Al-doped full concentration gradient Li[Ni0.76Co0.09Mn0.15]O2 as cathode, showing a good energy density of ca. 8.0 mWh cm-2. Furthermore, considering that low initial coulombic efficiency (ICE) of silicon is another drawback for its industrial application, tough graphite framework and optimized lithium polyacrylate binder could be applied to increase the ICE effectively. Reference s 1. U.-H. Kim, S.-T. Myung, C. S. Yoon and Y.-K. Sun, ACS Energy Lett. 2017, 2, 196.2. J. H. Lee, C. S. Yoon, J.-Y. Hwang, S.-J. Kim, F. Maglia, P. Lamp, S.-T. Myung and Y.-K. Sun, Energy Environ. Sci., 2016, 9, 2152.3. P. Li, J.-Y. Hwang and Y.-K. Sun, ACS Nano, 2019, 13, 2624. Figure 1

Lithium polyacrylate polymer coating enhances the performance of graphite/silicon/carbon composite anodes

In this study a graphite (Gr)/silicon (Si)/carbon (C) (Gr+C:Si = 85:15, wt.%) composite anode material was prepared through spray-drying and then subjected to wet-coating in an aqueous solution to obtain lithium polyacrylate (LiPAA)–coated Gr/Si/C composite anode materials. The thickness of the LiPAA coating layer of the 1 wt.% LiPAA-coated Gr/Si/C anode material was approximately 4 nm. The characteristics of the LiPAA-coated Gr/Si/C composite materials were examined using X-ray diffraction, micro-Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, the Brunauer–Emmett–Teller method, scanning electron microscopy/energy dispersive X-ray spectroscopy, and transmission electron microscopy. The capacity retentions of CR2032 half-cells featuring the pristine Gr/Si/C composite electrode were ca. 74.0% at 0.2C after 100 cycles and 30.0% at 0.5C after 500 cycles; they improved markedly—up to 94.4% and 82.2%, respectively—for the cells prepared with the 1 wt.% LiPAA-coated Gr/Si/C composite electrode. The LiPAA polymer coating functioned as an artificial solid electrolyte interphase layer that stabilized the structural integrity at the interface between the electrode and the electrolyte during the cycling process. Our experimental results suggest that LiPAA-coated Gr/Si/C composites are promising candidate materials for use as high-capacity anodes in next-generation lithium-ion batteries.

Surface Architecture Design of LiNi0.8Co0.15Al0.05O2 Cathode with Synergistic Organics Encapsulation to Enhance Electrochemical Stability

Ni-rich LiNi0.8 Co0.15 Al0.05 O2 (NCA) material attracts extensive attention due to its high discharge specific capacity, but its distinct drawbacks of rapid capacity decline and poor cycle performance at elevated temperatures and high voltage during charge/discharge cycling restricts its widespread application. To solve these problems, a multifunctional coating layer composed of a lithium-ion-conductive lithium polyacrylate (LiPAA) inner layer and a cross-linked polymer outer layer from certain organic substances of silane-coupling agent (KH550) and polyacrylic acid (PAA) is successfully designed on the surface of NCA materials, which is favorable for eliminating residual lithium and improving lithium-ion conductivity, surface stability, and hydrophobicity of NCA materials. In addition, the amount of the coating material is also investigated. A series of characterization methods such as XRD, FTIR, SEM, TEM, and X-ray photoelectron spectroscopy are used to analyze the morphologies and structures for materials of pristine and modified NCA. It is revealed that the co-coating layer plays a vital part in reducing the surface residual alkalis and improving the stability of NCA particles; as a result, the modified NCA exhibits a greatly improved rate capability, cycle performance, and low polarization impedance.

Enhanced electrochemical performance by GeOx-Coated MXene nanosheet anode in lithium-ion batteries

Here, we demonstrate a facile method to synthesize an amorphous GeOx-coated MXene nanosheet structure as the anode in lithium-ion batteries. By using the GeO32− as the precursor, NaBH4 as the reduction agent, we performed a one-pot in situ synthesis to prepare a composite of GeOx nanoparticles coated on MXene nanosheet. The size of the GeOx nanoparticles is approximately 50 nm, which offers abundant contact surface between active materials with the electrolyte, as well as fast pathways for Li-ion interaction. Moreover, the unique two-dimensional MXene nanosheet serves as the excellent conductive additives to improve the electrochemical stability and electrical conductivity of composite when used in LIBs. The results indicate that the GeOx/MXene nanosheet structure significantly improves the stability during the lithiation/delithiation processes, with the enhanced capacity through an improved kinetic process. Another attractive element of this novel anode is the flexibility to tune the electrochemical properties by using different combination of binder and solvent when the slurry is prepared for the electrode fabrication. The electrode prepared with polyvinylidene fluoride binder and N-methyl pyrrolidinone solvent exhibits an excellent sustainable capacity of 381 mAh g−1 at 15 A g−1. By contrast, the electrode with lithium polyacrylate and de-ionized water delivers a reversible capacity of 950 mAh g−1 at 0.5 A g−1 after 100 cycles. These interesting results are ascribed to the inner characteristic structure of the two types of electrodes, which have been verified by electrochemical kinetics and scanning electron microscopic images. It also reveals that the different dispersion state is responsible to the difference of electrochemical properties, which highlights the importance of the electrode design for high-performance lithium-ion batteries.