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Single-crystal LiNixMnyCo1-x-yO2 (SC-NMC) cathode with electro-chemo-mechanically compliant microstructure is regarded as a promising candidate for high-energy-density lithium ion battery. However, the research of Ni-rich SC-NCM still lags behind its corresponding polycrystalline cathode materials, mainly due to the difficulties in synthesis. Herein, the single-crystal LiNi0.8Mn0.1Co0.1O2 cathode (SC-NCM811) was successfully synthesized by microfluidic technology combined with the solid-state lithiation process. The nano-sized Ni0.8C- o0.1Mn0.1(OH)2 precursor prepared via microfluidic technology enhances its accessibility to lithium salts, thus exhibiting high chemical activity for lithiation reaction. As a result, the optimized SC-NCM811 cathode shows relatively small-scale grain size (<3 mu m), low cation mixing and well layered structure, which is beneficial to electrochemical kinetics and redox reversibility. The electrochemical characterization results further reveal that the optimized SC-NCM811 cathode can well balance the cycle performance and rate capability, showing good electrochemical performance. Overall, microfluidic technology is expected to provide a new strategy for pre-paring single-crystal Ni-rich cathode materials, which may extend to the commercial application of other cathode materials.

The nickel-rich ternary-layered oxide LiNixCoyMn(1-x-y)O2 (NCM) cathode exhibits high reversible capacity and low cost; however, severe capacity fade and aggravated air degradation prohibit its widespread commercialization. Herein, the hydrophobic fluoroalkylsilane-modified NCM811 cathode materials are reported. To better understand the effects of electrochemical properties of lithium-ion batteries, a variety of characterization techniques and electrochemical methods are utilized to study the surface chemistry at the cathode/electrolyte interphase. The hydrophobic fluoroalkylsilanes-grafted NCM811 cathode materials suppress the formation of residual lithium even after 30 days in humid air. The fluoroalkylsilanes layer can also provide chemical stabilization to the NCM811 cathode materials by anchoring transition metals (TM) and suppressing TM dissolution during long immersion times in electrolytes. Moreover, the degree of improvement depends on the structure of the fluoroalkylsilanes, such as the number of F groups and the length of carbon chains. As a result, FAS17-modified NCM811 cathode materials after 30-day humid air exposure (humidity 70%) exhibit the greatest overall capacity retention of 74.2% after 200 charge/discharge cycles.

The single-crystal Ni-rich Li(NixCoyMn1_x_y)O-2 cathode (NCM) demonstrates better cycle performance, enhanced tap density and improved mechanical structure stability, compared with polycrystalline NCM. However, limited Li+ transports, (003) plane slips and microcracks in large single particles hinder rate capability and cycle performance. To overcome these shortcomings, single-crystal NCM cathodes have been modified by nanosized tetragonal BaTiO3. Due to the dielectric properties, BaTiO(3 )particles induce electric field concentration at the BaTiO3-NCM-electrolyte interface. Thus, a large amount of lithium vacancies can be formed, providing sufficient sites for the hopping diffusion of lithium ions, thereby significantly enhancing the diffusion coefficient of Li+. Moreover, the redistribution of charges can inhibit the formation and accumulation of cathode-electrolyte-interface. Owing to the synergetic effect of BaTiO3, the BT-modified single-crystal NCM with the optimized loading shows a remarkable initial discharge capacity of 138.5 mAh g(_1) and maintains 53.8% of its initial discharge capacity after 100 cycles under 5C at 4.5 V cut-off voltage. Overall, the proposed dielectric cathode-electrolyte-interface strategy can enhance Li+ ion transport and stabilize the interface structure, leading to improved rate performance. Meanwhile, the diffusion-induced state of charge gradient can also be inhibited, resulting in high structure stability of single-crystal NCMs under high rate and cut-off voltage cycling. (C) 2022 Elsevier Inc. All rights reserved.

The room and low-temperature performances of solid-state lithium batteries are crucial to expand their practical application. Polyethylene oxide (PEO) has received great attention as the most representative polymer electrolyte matrix. However, most PEO-based solid-state batteries need to operate at high temperature due to low room temperature ionic conductivity. Improving the ionic conductivity by adding plasticizers or reducing the crystallinity of PEO often compromises its mechanical strength. Here, an amorphous PEO-based composite solid-state electrolyte is obtained by ultraviolet (UV) polymerizing PEO and methacryloyloxypropyltrimethoxy silane (KH570)-modified SiO2 which demonstrates both satisfactory mechanical performance and high ionic conductivity at room (3.37 x 10(-4) S cm(-1)) and low temperatures (1.73 x 10(-4) S cm(-1) at 0 degrees C). In this electrolyte, the crystallinity of PEO is reduced through cross-linking, and therefore provides a fast Li+ ions transfer area. Moreover, the KH570-modified SiO2 inorganic particles promote the dissociation of lithium salts by Lewis acid centers to increase the ionic conductivity. Importantly, this kind of cross-linking networks endows the final electrolyte much higher mechanical strength than the pure PEO polymer electrolyte or PEO-inorganic filler blended systems. The solid-state LiFePO4/Li cell assembled with this electrolyte exhibits excellent cycling performance and high capacity at room and low temperatures.

The application of LAGP ceramic solid electrolytes is circumscribed by the large electrode/electrolyte interfacial resistance because of their rigidity and brittleness. Here, a highly cohesive composite polymer layer consisting of poly(vinylene carbonate)-thermoplastic polyurethanes (PVC-TPU) is coated onto both sides of the Li1.5Al0.5Ge1.5(PO4)(3) pellet to address the interfacial problems with the electrodes. The coated PVC-TPU acts as an ionic conductive welding layer to facilitate the interfacial contact of the LAGP pellet with both electrodes and decreases the interfacial resistance of the LAGP pellet against the cathode (from 1.4 x 10(6) to 3.8 x 10(3) Omega cm(2)) and the Li-metal anode (from 3.3 x 10(4) to 890 Omega cm(2)). The resulting composite solid-state electrolyte (CSSE) presents the synergistic effect of the LAGP ceramic pellet and the PVC-TPU layer in terms of electrochemical stability, ionic transport properties, and stable lithium plating/stripping cycling with a low overpotential for 1000 h. Consequently, the LiFePO4/Li solid-state batteries utilizing this CSSE deliver a high capacity retention of 95.3% after 100 cycles at room temperature with a high Coulombic efficiency exceeding 99.99% per cycle and lithium dendrite inhibition.

The separator, an essential component in lithium ion batteries, faces more challenges with the increasing diversification of electrode materials towards higher energy density and longer life. Herein we report the performance improvements of lithium ion batteries enabled by the multifunctional separator, which is fabricated by constructing the silica-oxygen-borate (Si-O-B) thin layer on Al2O3-coated polyethylene separators through surface engineering. This separator inherits the advantage of Al2O3-coated polyethylene separators in terms of excellent thermal stability and puncture strength, and no obvious dimensional change at 200 degrees C. The Si-O-B thin layer provides abundant Lewis acid sites and excellent electrolyte uptake to desolvate Li+ ions and traps anions, and therefore favors excellent lithium ion transport properties and lithium/electrolyte interfacial stability. More importantly, the Si-O-B hybrid thin layer endows an additional function of scavenging HF and H2O molecules. The benefits offered by this separator are demonstrated by the enhanced C-rates capability and cycling performance of both LiCoO2/Li half-cell and NCM/graphite full cell, which lies far beyond those achievable with commercial polyethylene separators and Al2O3-coated polyethylene separators. This work presents a simple and efficient strategy to construct multifunctional separators with excellent comprehensive properties, and provides inspiration for the rational design of advanced separators towards next-generation high-performance batteries.

Ni-rich layered oxides are potential cathode candidate's materials for Li-ion batteries due to their low cost and high energy density. However, it is difficult to reproducibly prepare uniformly distributed element and wellcontrolled morphology of Ni-rich layered oxide particles. This study develops a continuous microfluidic reaction process to synthesize spherical carbonate precursors (Ni0.6Mn0.2Co0.2CO3). The as-synthesized LiNi0.6Co0.2Mn0.2O2 materials exhibit well-defined microsphere morphology, uniform particles size distribution, better thermal stability and homogeneous transition metal distribution, due to the excellent mixing, well mass and heat transfer rate during the microfluidic reaction. Moreover, the as-prepared LiNi0.6Co0.2Mn0.2O2 materials achieve higher initial capacity, excellent electrochemical reversibility and capacity retention than that of the samples prepared by traditional co-precipitation. Therefore, our results demonstrate that microfluidic reaction is a simple and effective synthesis technology for preparing Ni-rich layered cathode.

Molecular sieves (MSs) coated with conductive polymer (PEDOT:PSS) are used as water scavengers to modify the nickel‐rich LiNi1–x–yCoxMnyO2 (NMC)‐layered cathode. This strategy proactively captures residual water in the battery system without affecting the transport performance of electrons and Li+ ions. The moisture content and nuclear magnetic resonance (NMR) tests show that MSs after coating still maintain good water absorption characteristics and inhibit the decomposition of the electrolyte. The conductivity of the PEDOT:PSS@MS‐NMC electrode is 1.08 × 10−4 S cm−1, which is improved by 63.9%, compared with the MS‐NMC electrode. Through X‐ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy measurements, it is also shown that the surface structure stability and particle integrity for PEDOT:PSS@MS‐NMC electrode is well retained. After 500 cycles, the capacity retention of the composite cathode is 71.3%, which is higher than that of the NMC (38.3%) and MS‐NMC cathode (62.4%). This is a novel and effective strategy to suppress side reactions at the electrode interface and improve electrode stability, capacity retention, and cycle performance of the Ni‐rich NMC cathode.

The safety concerns and the pursuit of high energy density have stimulated the development of high-performance solid-state lithium ion batteries. Therefore, the key component in solid-state lithium batteries, i.e. the solid-state electrolytes, also has attracted tremendous attention due to its non-flammability and good adaptability to high-voltage cathodes/lithium metal anodes. An in-depth understanding of the existing problems of solid-state electrolytes and proposed strategies for addressing these problems is crucial for the efficient design of high-performance solid-state electrolytes. In this review, we systematically summarized the current limitations of composite solid-state electrolytes and efforts to overcome them, and gave some proposals for the future perspectives of solid-state electrolytes with the aim to provide practical guidance for the researchers in this area.

In this paper, a simple and feasible method for preparing gel polymer electrolyte (GPE) with good ionic transport properties and mechanical stability is proposed. A ZrO2/KH570/PU/P123 layer was formed on the outer and inner pore surfaces of PE separator before in situ polymerization by a simple one-step dipping coating process. This coating layer changes the PE separator surface from hydrophobic to hydrophilic, and therefore facilitates the uniform spreading of the GPE precursor solution on the PE surface to enable the formation of highly uniform GPE. Moreover, it effectively compensates the negative effects of in situ gelatinization on the ionic transport behavior of the final PE-supported GPE. This GPE possesses excellent ion transport properties and mechanical stability, as well as improves the static and dynamic interfacial stability with lithium metal anode. When using metallic lithium and LiCoO2 to assemble cells, this PE-supported GPE affords improved C-rate capability, cycling performance and effective dendrite inhibition. [GRAPHICS] .

Ni-rich cathode materials have received much attention because of their high specific capacity, low cost and environmentally friendly characteristic. However, the nickel-rich cathode is extremely sensitive to moisture, which results in poor structure stability and electrochemical performance. Herein, we demonstrate an efficient and simple route to prolong the lifetime of nickel-rich cathode by introducing a low-temperature dehydratable molecular sieve as water scavenger. The residual water content in electrolyte measurement and nuclear magnetic resonance test manifest that molecular sieve can effectively fix the trace H2O and reduce the decomposition rate of electrolyte from 16.6% to 4.0%, respectively. Transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy confirm that the molecular sieve inhibits the fragmentation of the electrode and the side reactions on the surface of the cathode. This approach improves structural integrity and stabilizes surface structure of the cathode, which increases the capacity retention without sacrificing rate performance. This effective strategy can be extended to other cathode materials which are sensitive to moisture to realize good cycling stability.

This paper proposes a strategy to fabricate surface activated polyethylene (PE)-supported gel polymer electrolyte (GPE) with high ion transport ability, excellent electrolyte retention and mechanical properties to stabilize lithium (Li)-metal anodes. The inert outer and inner pore surface activation of polyethylene is demonstrated by coating an ultrathin zirconium oxide nanocrystal (ZrO2)/polyhedral oligomeric silsesquioxane (POSS) composite layer through a simple layer by layer (LBL) assembly method prior to the in situ polymerization. It is found that the activation layer may improve the Li+ ion transference number and induce the formation of GPE with a gradient structure by the interaction with the initiator system, giving rise to higher ion transport ability of final GPE. On the other hand, the GPE using the activated PE separator as support improves the Li/electrolyte interfacial stability during storage and repeated lithium plating/stripping cycling. A stable voltage profile with cycling for more than 800 h in a Li/Li symmetric cell was obtained by using surface activated PE-supported GPE. When it is assembled into the cells with metallic lithium anodes and lithium cobalt oxide (LiCoO2) cathodes, the cells show excellent rate capability and cycling performance, as well as effective dendrite inhibition.

Lithium anodes suffer from severe safety problems in liquid electrolyte systems that result from an unstable Li plating/stripping process and Li dendrite growth, leading to rapid degradation of Li metal batteries. A polyethylene (PE)-supported gel polymer electrolyte (GPE) with excellent electrolyte uptake/retention capability was simply prepared in this paper by the construction of cross-linked polymer networks (PNs) on the surface of a poly(ethylenimine)-primed PE separator to stabilize the lithium anode. The highly delocalized negative charge of p-styrene sulfonate groups on PNs plays a role in regulating the Li+ and anion transport, giving rise to a high Li+ transference number. This GPE extended the electrochemical stability to 4.8 V and improved the stability of interface between the electrolyte and lithium metal anode (reduced overpotential and suppressed lithium dendrites) during storage and repeated lithium plating/stripping cycling. The Li metal anode-based battery employing this GPE exhibits excellent cycling stability and C-rate capability.

Poor intrinsic electrical conductivity as well as considerable volume change during lithium alloying/dealloying process has been a critical defect for high theoretical capacity silicon-based anodes. In our work, we demonstrate the synthesis design of multiscale recombined dendritic Si/Ag/C anode for high energy density LIBs via compositing bulky silicon with uniformly distributed Ag NPs, followed by a carbon source PDA (polydopamine) coating step. Here Ag NPs are generated by an in situ redox reaction between Ag+ and PDA, no need for additional reducing agents. According to the characterization analysis, the robust porous Si/Ag/C structure can provide channels for fast Li+ diffusion and electron conduction, promoting the formation of a thinner and more stable SEI film. As a result, the Si/Ag/C composite anode still yields a relatively high residual capacity of 1422.1 mAh g (1) after 100 cycles at 0.2 A g (1). In addition, it remains 633.1 mAh g (1) after 500 cycles at a high current density of 8 A g (1).

The metallic lithium anode provides unparalleled opportunities for rechargeable batteries with very high energy density. A main problem hindering the development of cells using metallic lithium anodes stems from the electrochemical instability of the interface between metallic lithium and organic liquid electrolytes. This paper reports an approach rationally designing the surface characteristic of separator for stable, dendrite-free operation of lithium-metal batteries. A unique polymer multilayer PEI(PAA/PEO)(3) was fabricated on the microporous polyethylene (PE) separator by a simple layer-by-layer (LbL) assembly process, which maintains the pore structure and thickness of PE separator but remarkably enhances the ionic conductivity (from 0.36 mS cm(-1) to 0.45 mS cm(-1)) and Li+ transference number (from 0.37 to 0.48), as well as stabilizes lithium metal anodes against the reaction with liquid electrolytes during storage and repeated charge/discharge cycles, which is responsible for restraining the electrode polarization and the formation of lithium dendrites, and therefore endows lithium metal batteries with long-term cycling at high columbic efficiency and excellent rate capability, as well as the improved safety.

Poor stability of lithium metal anodes in liquid electrolytes hinders its practical application in rechargeable batteries with very high energy density. Herein, we present an approach to tackle the intrinsic problems of Li metal anodes from the standpoint of separators. By a facile and versatile method based on mussel-inspired surface chemistry, a hybrid polydopamine/octaammonium POSS (PDA/POSS) coating was spontaneously formed on the surface of PE separators through the self-polymerization and strong adhesion feature of dopamine. This ultrathin PDA/POSS coating endows PE separators with different surface characteristics while keeping its microporous structure almost unchanged. The altered surface characteristics influence the separator/electrolyte interaction, and lead to remarkable enhanced ionic conductivity (from 0.36 mS cm−1 to 0.45 mS cm−1) and Li+ ion transference number (from 0.37 to 0.47) of PE separators as well as the improved stability of lithium/electrolyte interface, which effectively decreases the electrode polarization and suppresses the lithium dendrites formation, contributing to superior C-rates capability and cycling performance of cells.

Low Li+ ion transference number is one fatal defect of the liquid LiPF6 electrolyte for Li-metal anode based batteries. This work aims to improve Li+ ion transference number and ionic conductivity polyethylene (PE) separators. By a simple dip-coating method, the water-borne nanosized molecular sieve with 3D porous structure (ZSM-5) can be coated on PE separators. Especially, the Li+ ion transference number is greatly enhanced from 0.28 to 0.44, which should be attributed to the specific pore structure and channel environment of ZSM-5 as well as the interaction between ZSM-5 and electrolyte. Compared with the pristine PE separator, the ionic conductivity of modified separators is remarkably improved from 0.30 to 0.54 mS cm(-1). As results, the C-rate capability and cycling stability are both improved. The Li-metal battery using the ZSM-5-modified PE separator keeps 94.2% capacity after 100 cycles. In contrast, the discharge capacity retention of the battery using pristine PE is only 74.7%.

The composite of tungsten-doped SnO2 and reduced graphene oxide was synthesized through a simple one pot hydrothermal method. According to the structural characterization of the composite, tungsten ions were doped in the unit cells of tin dioxide rather than simply attaching to the surface. Tungsten-doped SnO2 was in situ grown on the surface of graphene sheet to form a three-dimensional conductive network that enhanced the electron transportation and lithium-ion diffusion effectively. The issues of SnO2 agglomeration and volume expansion could be also avoided because the, tungsten-doped SnO2 nanoparticles were homogeneously distributed on a graphene sheet. As a result, the nanocomposite electrodes of tungsten-doped SnO2 and reduced graphene oxide exhibited an excellent long-term cycling performance. The residual capacity was still as high as 1100 mA h g(-1) at 0.1 A g(-1) after 100 cycles. It still remained at 776 mA h g(-1) after 2000 cycles at the current density of lA g(-1).

Today there are new interests in using metallic lithium as anode materials in lithium batteries because of its extremely large theoretical specific capacity. However, the low cycle efficiency and the lithium dendrite formation during repeated charge/discharge cycles hinder the practical application of metallic lithium anodes. Herein, we report a distinctive ZrO2/POSS multilayer deposited on PE separators by a simple layer-by-layer (LbL) self-assembly process to enable excellent rate capability and cycle life of lithium metal batteries. The ZrO2/POSS multilayer on PE separators weakens the solvation effect of lithium ions and significantly enhances the electrolyte uptake of separators, which is responsible for the enhanced ionic conductivity and Li+ transference number, as well as the improved Li/electrolyte interfacial stability. These advantageous characteristics of the resulting PE separators effectively decrease the electrode polarization and protect lithium metal anodes against lithium dendrites formation during repeated charge/discharge cycles, endowing LiCoO2/Li unit cells with both excellent electrochemical performance and high safety. The fundamental understanding on the effects of the micro/nano structures and properties of separators on the important electrochemistry processes at electrode/electrolyte interface of battery systems may lead to new approaches to tackle the intrinsic problems of Li metal anodes for energy storage applications.

The developments of high-performance lithium ion battery are eager to the separators with high ionic conductivity and thermal stability. In this work, a new way to adjust the comprehensive properties of inorganic-organic composite separator was investigated. The cellulose diacetate (CDA)-SiO2 composite coating is beneficial for improving the electrolyte wettability and the thermal stability of separators. Interestingly, the pore structure of composite coating can be regulated by the weight ratio of SiO2 precursor tetraethoxysilane (TEOS) in the coating solution. The electronic performance of lithium ion batteries assembled with modified separators are improved compared with the pristine PE separator. When weight ratio of TEOS in the coating solution was 9.4%, the composite separator shows the best comprehensive performance. Compared with the pristine PE separator, its meltdown temperature and the break-elongation at elevated temperature increased. More importantly, the discharge capacity and the capacity retention improved significantly.

With the development of electric vehicles, the traditional polyolefin separators can not meet the increasing requirements of lithium ion batteries with high power density, high energy density, and high safety performance. Herein, a novel water-based binder is synthesized by grafting carboxyl groups onto cellulose diacetate. When the polyethylene (PE) separator is coated by this binder and SiO2 nanoparticles, the thermal shrinkage of the modified separator is observed to be almost 0% after exposure at 200 degrees C for 30 min. The puncture strength significantly increase from 5.10 MPa (PE separator) to 7.64 MPa. More importantly, the capacity retention of the cells assembled with modified separators after 100 cycles at 0.5 C increase from 73.3% (cells assembled with PE separator) to 81.6%, owing to the excellent electrolyte uptake and the good compatibility with lithium electrode. Besides, the modified separator shows excellent surface stability after 100 cycles. Considering the above excellent properties, this composite separator shows high potential to be used in lithium ion batteries with high power density and safety.

A simple and environmentally friendly self-assembly process of oppositely charged polymer PEI and inorganic oxide SiO2 was demonstrated for the construction of an ultrathin layer on the surface of PE separator. The XPS, FT-IR, SEM, and EDS characterizations give clear evidence of the successful self-assembly of PEI and SiO2 without significantly increasing the thickness and sacrificing the pristine porous structure of PE separator. This process improves a variety of crucial properties of PE separator such as the electrolyte wetting, the electrolyte uptake, the thermal stability, the ionic conductivity, Li+ transference number, the electrochemical stability and the compatibility with lithium electrode, endowing lithium-ion battery (Li as anode and LiCoO2 as cathode) with excellent capacity retention at high C-rates and superior cycling performance. At the current density of 5 C, the cell with PE separator almost loses all the capacity. In contrast, the cell with (PEI/SiO2)-modified PE separator still holds 45.2% of the discharge capacity at 0.2 C. The stabilized SEI formation and high Li+ transference number of (PEI/SiO2)-modified PE separator were interpreted to be the substantial reasons leading to the remarkably enhanced battery performance, rendering some new insights into the role of the separator in lithium-ion batteries.

A simple layer-by-layer (LbL) self-assembly process of poly(acrylic acid) (PAA) and ZrO2 was applied to construct functional ultrathin multilayers on polyethylene (PE) separators without sacrificing the excellent porous structure of separators. Such PAA/ZrO2 LbL-modified PE separators possess good electrolyte wettability, excellent electrolyte uptake, high ionic conductivity and large Li+ transference number. More importantly, the top layer of LbL self-assembly would affect the dissociation of electrolyte and the formation of solid electrolyte interphase (SEI) layer in half-cells. Compared with the pristine and (PAA/ZrO2)(1)PAA-modified PE separators, (PAA/ZrO2)(3)-modified PE separator shows a larger Li+ transference number (0.6) and a faster tendency to form a stable SEI layer, endowing half-cells with excellent capacity retention at high C-rates and superior cycling performance. These fascinating characteristics will provide the LbL self-assembly with a promising method to improve the surface property of PE separators for high performance lithium-ion batteries.

Tin oxide (SnO2) is a kind of anode material with high theoretical capacity. However, the volume expansion and fast capability fading during cycling have prevented its practical application in lithium ion batteries. Herein, we report that the nanocomposite of fluorine-doped tin oxide (FTO) and reduced graphene oxide (RGO) is an ideal anode material with high capacity, high rate capability, and high stability. The FTO conductive nanocrystals were successfully anchored on RGO nanosheets from an FTO nanocrystals colloid and RGO suspension by hydrothermal treatment. As the anode material, the FTO/RGO composite showed high structural stability during the lithiation and delithiation processes. The conductive FTO nanocrystals favor the formation of stable and thin solid electrolyte interface films. Significantly, the FTO/RGO composite retains a discharge capacity as high as 1439 mAhg(-1) after 200 cycles at a current density of 100 mAg(-1). Moreover, its rate capacity displays 1148 mAhg(-1) at a current density of 1000 mAg(-1).