Long-term survivals of immune checkpoint inhibitors as neoadjuvant and adjuvant therapy in dMMR/MSI-H colorectal and gastric cancers.

BACKGROUND: The long-term survival benefit of immune checkpoint inhibitors (ICIs) in neoadjuvant and adjuvant settings is unclear for colorectal cancers (CRC) and gastric cancers (GC) with deficiency of mismatch repair (dMMR) or microsatellite instability-high (MSI-H). METHODS: This retrospective study enrolled patients with dMMR/MSI-H CRC and GC who received at least one dose of neoadjuvant ICIs (neoadjuvant cohort, NAC) or adjuvant ICIs (adjuvant cohort, AC) at 17 centers in China. Patients with stage IV disease were also eligible if all tumor lesions were radically resectable. RESULTS: In NAC (n = 124), objective response rates were 75.7% and 55.4%, respectively, in CRC and GC, and pathological complete response rates were 73.4% and 47.7%, respectively. The 3-year disease-free survival (DFS) and overall survival (OS) rates were 96% (95%CI 90-100%) and 100% for CRC (median follow-up [mFU] 29.4 months), respectively, and were 84% (72-96%) and 93% (85-100%) for GC (mFU 33.0 months), respectively. In AC (n = 48), the 3-year DFS and OS rates were 94% (84-100%) and 100% for CRC (mFU 35.5 months), respectively, and were 92% (82-100%) and 96% (88-100%) for GC (mFU 40.4 months), respectively. Among the seven patients with distant relapse, four received dual blockade of PD1 and CTLA4 combined with or without chemo- and targeted drugs, with three partial response and one progressive disease. CONCLUSION: With a relatively long follow-up, this study demonstrated that neoadjuvant and adjuvant ICIs might be both associated with promising DFS and OS in dMMR/MSI-H CRC and GC, which should be confirmed in further randomized clinical trials.

Novel Low-Strain Layered/Rocksalt Intergrown Cathode for High-Energy Li-Ion Batteries.

Both layered- and rocksalt-type Li-rich cathode materials are drawing great attention due to their enormous capacity, while the individual phases have their own drawbacks, such as great volume change for the layered phase and low electronic and ionic conductivities for the rocksalt phase. Previously, we have reported the layered/rocksalt intergrown cathodes with nearly zero-strain operation, while the use of precious elements hinders their industrial applications. Herein, low-cost 3d Mn4+ ions are utilized to partially replace the expensive Ru5+ ions, to develop novel ternary Li-rich cathode material Li1+x[RuMnNi]1-xO2. The as-designed Li1.15Ru0.25Mn0.2Ni0.4O2 is revealed to have a layered/rock salt intergrown structure by neutron diffraction and transmission electron microscopy. The as-designed cathode exhibits ultrahigh lithium-ion reversibility, with 0.86 (231.1 mAh g-1) out of a total Li+ inventory of 1.15 (309.1 mAh g-1). The X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectra further demonstrate that the high Li+ storage of the intergrown cathode is enabled by leveraging cationic and anionic redox activities in charge compensation. Surprisingly, in situ X-ray diffraction shows that the intergrown cathode undergoes extremely low-strain structural evolution during the charge-discharge process. Finally, the Mn content in the intergrown cathodes is found to be tunable, providing new insights into the design of advanced cathode materials for high-energy Li-ion batteries.

Accelerated aging of lithium-ion batteries: bridging battery aging analysis and operational lifetime prediction.

The exponential growth of stationary energy storage systems (ESSs) and electric vehicles (EVs) necessitates a more profound understanding of the degradation behavior of lithium-ion batteries (LIBs), with specific emphasis on their lifetime. Accurately forecasting the lifetime of batteries under various working stresses aids in optimizing their operating conditions, prolonging their longevity, and ultimately minimizing the overall cost of the battery life cycle. Accelerated aging, as an efficient and economical method, can output sufficient cycling information in short time, which enables a rapid prediction of the lifetime of LIBs under various working stresses. Nevertheless, the prerequisite for accelerated aging-based battery lifetime prediction is the consistency of aging mechanisms. This review, by comprehensively summarizing the aging mechanisms of various components within LIBs and the battery degradation mechanisms under stress-accelerated conditions, provides a reference for evaluating the consistency of battery aging mechanisms. Furthermore, this paper introduces accelerated aging-based lifetime prediction models and offers constructive suggestions for future research on accelerated lifetime prediction of LIBs.

Roles of Fast-Ion Conductor LiTaO3 Modifying Ni-rich Cathode Material for Li-Ion Batteries.

Limited cycling stability hampers the commercial application of Ni-rich materials, which are regarded as one of the most promising cathode materials for Li-ion batteries. Ni-rich LiNi0.9 Co0.06 Mn0.04 O2 layered cathode was modified with different amounts of LiTaO3 , and the influences of fast-ion conductor material on cathode materials were explored. Detailed analysis of the materials revealed the formation of a uniformly epitaxial LiTaO3 coating layer and a little Ta5+ doping into the lattice structure of Ni-rich materials. The coating-layer thickness increased with the amount of LiTaO3 added, protecting the electrode from erosion by electrolyte and suppressing undesired parasitic reactions on the cathode-electrolyte interface. Meanwhile, the doped Ta5+ increased the interplanar spacing of materials, accelerating Li+ transfer. Using the positive synergistic effects of LiTaO3 -coating and Ta5+ -doping, improved capacity retentions of the modified materials, especially for 0.25 and 0.5 wt%-coated Ni-rich materials, were obtained after long-term cycling, showing the potential applications of LiTaO3 modification. Further, the relations between one excessively thick coating layer and transfer of Li+ /electron between the cathode and electrolyte was established, proving that very thick coating layers, even layers containing Li ions, have adverse effects on electrochemical performances. This finding may help to understand the roles of the coating layer better.

High-Temperature Storage Deterioration Mechanism of Cylindrical 21700-Type Batteries Using Ni-Rich Cathodes under Different SOCs.

The safety and energy density of lithium-ion batteries (LIBs) are important concerns. The use of high-capacity cathode materials, such as Ni-rich cathodes, can greatly improve the energy density of LIBs, but it also brings some safety hazards. Cylindrical 21700-type batteries using Ni-rich cathodes were employed here to investigate their high-temperature storage deterioration mechanism under different states of charge (SOCs). Electrolyte decomposition was identified as the main problem. It can be worsened by elevated storage temperatures and battery SOCs, with the latter having a more significant influence. Specifically, the decomposition of the LiPF6 solute and the carbonate solvent will induce hydrofluoric acid (HF) formation and solid-electrolyte interphase (SEI) film regeneration, respectively. HF erosion will aggravate the dissolution of transition metal ions and structural degradation of cathode materials, while the destruction/regeneration of SEI films will consume active lithium and hinder Li+ diffusion at the anode side. Besides, the self-discharge behavior will also enlarge the graphite layer spacing, thus decreasing the graphitization degree of graphite anodes and causing anode failure. These findings will aid in the development of strategies for improving the safety of LIBs with high energy density.

Clean the Ni-Rich Cathode Material Surface With Boric Acid to Improve Its Storage Performance.

The existence of residual lithium compounds (RLCs) on the surface of layered Ni-rich materials will deteriorate the electrochemical properties and cause safety problem. This work presents an effective surface washing method to remove the RLCs from LiNi0.90Co0.06Mn0.04O2 material surface, via ethyl alcohol solution that contains low concentration of boric acid. It is a low-cost process because the filter liquor can be recycled. The optimal parameters including washing time, boric acid concentration, and solid-liquid ratio were systematically studied. It has been determined by powder pH and Fourier transform infrared spectra results that the amount of RLCs was reduced effectively, and the storage performance was significantly enhanced for the washed samples. The 150th capacity retentions after storing had increased from 68.39% of pristine material to 85.46-94.84% of the washed materials. The performance enhancements should be ascribed to the surface washing process, which removed not only the RLCs, but also the loose primary particles effectively.

Riveting Dislocation Motion: The Inspiring Role of Oxygen Vacancies in the Structural Stability of Ni-Rich Cathode Materials.

In Ni-rich cathode materials, dislocation can be generated at the surface of primary grains because of the accumulation of stress fields. The migration of dislocation into grains, accelerating the annihilation of reverse dislocation as well as oxygen loss, is considered as the principal origin of crack nucleation, phase transformation, and consequent fast capacity decay. Thus, reducing the dislocation would be effective for improving cathode stability. Here, we report the inspiring role of oxygen vacancies in blocking and anchoring the dislocation. Specifically, a large number of oxygen vacancies can assemble to form dense dislocation layers at the surface of grains. Thanks to the dislocation interaction mechanism, preformed dense dislocation at the surface can effectively rivet the newly developed dislocation during cycling. Ex situ transmission electron microscopy analysis indicates that the intragranular cracks and phase transformation were hindered by the riveted effect, which in turn improved the structural and cycling stability of the Ni-rich cathode. Overall, this work provides novel crystallographic design and understanding of the enhanced mechanical strength of Ni-rich cathode materials.

Improved Stability of Layered and Porous Nickel-Rich Cathode Materials by Relieving the Accumulation of Inner Stress.

The commercial application of high-capacity LiNi0.8 Co0.1 Mn0.1 O2 is impeded by its inferior cycling stability, which has been attributed to structural instability caused by stress accumulation during both calcination and cycling. A porous structure was deliberately introduced into nickel-rich material particles to relieve such stress. Cross-sectional SEM and mercury penetration tests confirmed the successful construction of a porous structure. Ex situ TEM and powder XRD confirmed that the porous structure reduced the stress concentration regions in uncycled nickel-rich material by providing a buffer space. In addition, the porous structure helps the permeation of the electrolyte and alleviates the stress accumulation during cycling, endowing the nickel-rich cathode materials with enhanced rate capability and suppressed phase transition. This strategy can be extended for the synthesis of diverse nickel-rich cathode materials to improve their cycling stability.

Improving the Structure Stability of LiNi0.8Co0.1Mn0.1O2 by Surface Perovskite-like La2Ni0.5Li0.5O4 Self-Assembling and Subsurface La3+ Doping.

The commercialization of high-capacity Ni-rich cathode LiNi0.8Co0.1Mn0.1O2 is still hindered by some defects, such as moderate rate property and inferior high-voltage cycling stability. The main reason is that the structural transformation starts at the surface from layered to spinel and then to the rock salt phase, which will be aggravated under a higher voltage and gradually spread to the bulk region during cycling. Here, we fabricate the LiNi0.8Co0.1Mn0.1O2 surface with the perovskite-like La2Ni0.5Li0.5O4, which possesses good thermostability and Li+-ion diffusion kinetics, to strengthen its surface and subsurface lattice stability. First-principles theory has confirmed the well compatibility of La2Ni0.5Li0.5O4 with LiNi0.8Co0.1Mn0.1O2, thus affording unimpeded channels for fast Li+-ion transport in the same dimensions through these two crystal lattices. On the other hand, during the high-temperature synthesis process, La3+ ions are also doped into the subsurface lattice of LiNi0.8Co0.1Mn0.1O2. After La modification with the two above-mentioned effects, the structure stability of LiNi0.8Co0.1Mn0.1O2 at high operating voltages and after long cycles has been significantly enhanced. Specifically, at 2.75-4.5 V, the first discharge capacity at 0.2C of the La-modified sample is 229.3 mAh g-1 and the 200th capacity retention ratio at 1C has been improved from 63.7 to 90.1%.

High-Rate Structure-Gradient Ni-Rich Cathode Material for Lithium-Ion Batteries.

To simultaneously achieve high compaction density and superior rate performance, a structure-gradient LiNi0.8Co0.1Mn0.1O2 cathode material composed by a compacted core and an active-plane-exposing shell was designed and synthesized via a secondary co-precipitation method successfully. The tight stacking of primary particles in the core part ensures high compaction density of the material, whereas the exposed active planes, resulting from the stacking of primary nanosheets along the [001] crystal axis predominantly, in the shell region afford enhanced Li+ transport. Thus, this structure-gradient Ni-rich cathode material shows a high compaction density with excellent electrochemical performances, especially the rate performance, exhibiting excellent rate capability (160 mA h g-1 at 10 C), which is 62% larger than that of the pristine material within 2.75-4.3 V (vs Li+/Li). Our work proposes a possible strategy for designing and synthesizing layered cathode materials with the required hierarchical structure to meet different application requirements.

Hand-in-Hand Reinforced rGO Film Used as an Auxiliary Functional Layer for High-Performance Li-S Batteries.

For lithium-sulfur (Li-S) batteries, a promising candidate for future high-energy storage devices, several prominent problems still need to be solved urgently, such as limited rate capability and poor cycle life caused by the insulating nature of sulfur and the shuttle of soluble polysulfides produced during battery operation. In this work, a facile vacuum filtration method is employed to graft polyethyleneimine to reduced graphene oxide (rGO) in a "hand-in-hand" way using the amino and catechol groups from polydopamine. The resulting polymer-reinforced rGO (PPG) film is applied as a free-standing auxiliary functional layer for Li-S batteries. It has been confirmed by both theoretical calculations and experimental methods that, benefiting from the rich amine groups and oxygen-containing functional groups, the as-prepared PPG composite film shows great ability to capture polysulfides. Moreover, its high conductivity enables itself to function as a polysulfide reservoir, thus facilitating the successive reutilization of the trapped active materials and improving sulfur utilization. For this reason, the PPG film can also be regarded as a cathode material, serving as a novel "SPPG cathode" together with the pure sulfur cathode. The cell assembled with the pure sulfur cathode and the PPG auxiliary functional layer displays high reversible capacity, excellent Coulombic efficiency, and good cycling stability, suggesting that the rational auxiliary functional layer design ensures a good match with pure sulfur cathodes and shows the potential to achieve energy-dense Li-S batteries.

The Effects of Trace Yb Doping on the Electrochemical Performance of Li-Rich Layered Oxides.

Layered lithium-rich cathode materials are one of the most promising cathode materials owing to their higher mass energy density than the commercial counterparts. A series of trace Yb-doped lithium-rich cathode materials Li1.2 Mn0.54 Ni0.13 Co0.13-x Ybx O2 (0≤x≤0.050) were synthesized and the effects were investigated by XRD, X-ray photoelectron spectroscopy, and high-resolution TEM. The participation of Yb ions in electrochemical reactions and the larger binding energy of Yb-O than M-O (M=Mn, Ni, Co), which expands the lithium layer spacing and stabilizes the oxygen stacking, resulted in excellent performance of materials doped with a limited Yb content (x≤0.005). However, higher doping amounts (x>0.005) significantly increased the charge-transfer impedance and led to a sharp deterioration in electrochemical performance. The reason lies in the large difference in ionic radius between the transition metals (Mn, Co, and Ni) and Yb. There is an upper limit to the amount of Yb ions in the lattice. If the amount of Yb is higher than the limit, excess Yb ions enter the Li layers instead of staying in the transition-metal layers or even segregate on the surface and form electrochemically inert oxides.

Ginsenoside Rg3 suppresses the proliferation of prostate cancer cell line PC3 through ROS-induced cell cycle arrest.

To investigate the potential antitumor effects of ginsenoside Rg3 in prostate cancer cells, the androgen-insensitive prostate cancer cell line PC3 was cultured and incubated with ginsenoside Rg3 in vitro. Cell number counts, cell proliferation assays and senescence-associated ß-galactosidase (SA-ß-gal) staining were performed to evaluate cell proliferation. The results demonstrated that ginsenoside Rg3 led to cell proliferation arrest; ginsenoside Rg3 decreased the number of cells and increased the positive SA-ß-gal staining rate in PC3 cells. Cell cycle analysis by flow cytometry revealed that ginsenoside Rg3 interfered with the G1/S transition in PC3 cells. The mechanism involved in ginsenoside Rg3-induced cell proliferation arrest was then further investigated. This indicated that the level of reactive oxygen species (ROS) in PC3 cells was upregulated by ginsenoside Rg3 treatment. Furthermore, pretreatment with N-acetyl-L-cysteine, a scavenger of ROS, was able to reverse the effects on cell number and cell cycle arrest induced by ginsenoside Rg3 in PC3 cells. These results indicate that ginsenoside Rg3 exhibits anticancer effects on prostate cancer cells through ROS-mediated arrest of the cell cycle.

Use of Ce to Reinforce the Interface of Ni-Rich LiNi0.8 Co0.1 Mn0.1 O2 Cathode Materials for Lithium-Ion Batteries under High Operating Voltage.

Nickel-rich cathode materials are among the most promising cathode materials for high-energy lithium-ion batteries. However, their structural and thermodynamic stability, cycle and rate performances still need to be further improved. In this study, the rare earth element Ce is employed to reinforce the interface of Ni-rich cathode materials both internally and externally. High-valence Ce4+ can easily cause the oxidization of Ni2+ to Ni3+ when doped into the material owing to its strong oxidation performance, thus reducing Li+ /Ni2+ mixing. In addition, the inert Ce3+ ions in transition metal slabs with strong Ce-O bonds can maintain the layered structure at high delithiation state. Furthermore, when the calcination temperature during synthesis is above 500 °C, a CeO2 coating layer will form, which can protect the electrode from erosion by the electrolyte and alleviate the increasing resistance during cycling. The modified Ni-rich materials fabricated with an erosion-resistant CeO2 layer outside and stronger Ce-O bonds inside with reduced Li+ /Ni2+ mixing exhibit excellent electrochemical properties, especially at high operating voltages, for example, the 50th capacity retention at 0.2 C within 2.75-4.5 V is improved from 89.8 % to 99.2 % after the modification.

Sufficient Utilization of Zirconium Ions to Improve the Structure and Surface properties of Nickel-Rich Cathode Materials for Lithium-Ion Batteries.

We doped Zr4+ ions in the outer layer of Ni0.8 Co0.1 Mn0.1 (OH)2 by coprecipitation. The distribution of Zr4+ in the final cathode materials showed a gradient distribution because of ion migration during the thermal treatment. The doped layer was confirmed by using various analysis methods (energy-dispersive X-ray spectroscopy, XRD, X-ray photoelectron spectroscopy, and TEM), which implies that Zr4+ can not only occupy both the transition metal slabs and Li slabs but also form a Li2 ZrO3 layer on the surface as a highly ion-conductive layer. The doped Zr4+ in the transition metal slabs can stabilize the crystal structure because of the strong Zr-O bond energy, and the doped Zr4+ in the Li slabs can act as pillar ions to improve the structural stability and reduce cation mixing. The gradient doping can take advantage of the "pillar effect" and restrain the "blocking effect" of the pillar ions, which reduces irreversible capacity loss and improves the cycling and rate performance of the Ni-rich cathode materials. The capacity retention of the modified sample reached 83.2 % after 200 cycles at 1C (200 mA g-1 ) at 2.8-4.5 V, and the discharge capacity was up to 164.7 mAh g-1 at 10C. This effective strategy can improve the structure stability of the cathode material while reducing the amount of non-electrochemical active dopant because of the gradient distribution of the dopant. In addition, the highly ion-conductive layer of Li2 ZrO3 on the surface can improve the rate performance of the cathode.

Exposing the {010} Planes by Oriented Self-Assembly with Nanosheets To Improve the Electrochemical Performances of Ni-Rich Li[Ni0.8Co0.1Mn0.1]O2 Microspheres.

A modified Ni-rich Li[Ni0.8Co0.1Mn0.1]O2 cathode material with exposed {010} planes is successfully synthesized for lithium-ion batteries. The scanning electron microscopy images have demonstrated that by tuning the ammonia concentration during the synthesis of precursors, the primary nanosheets could be successfully stacked along the [001] crystal axis predominantly, self-assembling like multilayers. According to the high-resolution transmission electron microscopy results, such a morphology benefits the growth of the {010} active planes of final layered cathodes during calcination treatment, resulting in the increased area of the exposed {010} active planes, a well-ordered layer structure, and a lower cation mixing disorder. The Li-ion diffusion coefficient has also been improved after the modification based on the results of potentiostatic intermittent titration technique. As a consequence, the modified Li[Ni0.8Co0.1Mn0.1]O2 material exhibits superior initial discharges of 201.6 mA h g-1 at 0.2 C and 185.7 mA h g-1 at 1 C within 2.8-4.3 V (vs Li+/Li), and their capacity retentions after 100 cycles reach 90 and 90.6%, respectively. The capacity at 10 C also increases from 98.3 to 146.5 mA h g-1 after the modification. Our work proposes a novel approach for exposing high-energy {010} active planes of the layered cathode material and again confirms its validity in improving electrochemical properties.

Ni-Rich LiNi0.8Co0.1Mn0.1O2 Oxide Coated by Dual-Conductive Layers as High Performance Cathode Material for Lithium-Ion Batteries.

Ni-rich materials are appealing to replace LiCoO2 as cathodes in Li-ion batteries due to their low cost and high capacity. However, there are also some disadvantages for Ni-rich cathode materials such as poor cycling and rate performance, especially under high voltage. Here, we demonstrate the effect of dual-conductive layers composed of Li3PO4 and PPy for layered Ni-rich cathode material. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy show that the coating layers are composed of Li3PO4 and PPy. (NH4)2HPO4 transformed to Li3PO4 after reacting with surface lithium residuals and formed an inhomogeneous coating layer which would remarkably improve the ionic conductivity of the cathode materials and reduce the generation of HF. The PPy layer could form a uniform film which can make up for the Li3PO4 coating defects and enhance the electronic conductivity. The stretchy PPy capsule shell can reduce the generation of internal cracks by resisting the internal pressure as well. Thus, ionic and electronic conductivity, as well as surface structure stability have been enhanced after the modification. The electrochemistry tests show that the modified cathodes exhibited much improved cycling stability and rate capability. The capacity retention of the modified cathode material is 95.1% at 0.1 C after 50 cycles, whereas the bare sample is only 86%, and performs 159.7 mAh/g at 10 C compared with 125.7 mAh/g for the bare. This effective design strategy can be utilized to enhance the cycle stability and rate performance of other layered cathode materials.

Synergistic Effects of Stabilizing the Surface Structure and Lowering the Interface Resistance in Improving the Low-Temperature Performances of Layered Lithium-Rich Materials.

The layered lithium-rich cathode material, Li1.2Ni0.2Mn0.6O2, was successfully synthesized by a sol-gel method followed by coating with different amounts of Li2O-2B2O (LBO, 1, 3, and 5 wt %). The effects of LBO-coating layer on the structure, morphology, and low-temperature (-30 °C) electrochemical properties of these materials are investigated systematically. The morphology, crystal structure, and grain size of the Li-rich layered oxide are not essentially changed after surface modification; according to the TEM results, the Li-B-O coating layer exists as an amorphous layer with a thickness of 5-8 nm when the amount is 3 wt %. Electrochemistry tests reveal that 3 wt % LBO-coated samples present the best electrochemical capability at low temperature. At -20 °C, the 3 wt % LBO-coated sample could retain 45.7% of the initial discharge capacity (131.7/288.0 mAh g-1) of that at 30 °C, while the pristine material could only retain 22.5% (57.5/256.0 mAh g-1). XPS spectra and EIS results reveal that such an enhancement of low-temperature discharge capacity should be attributed to the proper LBO-coating layer, which not only endows the modified materials with more stable surface structure but also lowers the interface resistance of Li+ diffusion through the interface and charge transfer reaction.

Enhanced Electrochemical Performance of Layered Lithium-Rich Cathode Materials by Constructing Spinel-Structure Skin and Ferric Oxide Islands.

Layered lithium-rich cathode materials have been considered as competitive candidates for advanced lithium-ion batteries because they are environmentally benign, high capacity (more than 250 mAh·g-1), and low cost. However, they still suffer from poor rate capability and modest cycling performance. To address these issues, we have proposed and constructed a spinel-structure skin and ferric oxide islands on the surface of layered lithium-rich cathode materials through a facile wet chemical method. During the surface modification, Li ions in the surface area of pristine particles could be partially extracted by H+, along with the depositing process of ferric hydrogen. After calcination, the surface structure transformed to spinel structure, and ferric hydrogen was oxidized to ferric oxide. The as-designed surface structure was verified by EDX, HRTEM, XPS, and CV. The experimental results demonstrated that the rate performance and capacity retentions were significantly enhanced after such surface modification. The modified sample displayed a high discharge capacity of 166 mAh·g-1 at a current density of 1250 mA·g-1 and much more stable capacity retention of 84.0% after 50 cycles at 0.1C rate in contrast to 60.6% for pristine material. Our surface modification strategy, which combines the advantages of spinel structure and chemically inert ferric oxide nanoparticles, has been shown to be effective for realizing the layered lithium-rich cathodes with surface construction of fast ion diffusing capability as well as robust electrolyte corroding durability.

Layer-by-Layer Assembled Architecture of Polyelectrolyte Multilayers and Graphene Sheets on Hollow Carbon Spheres/Sulfur Composite for High-Performance Lithium-Sulfur Batteries.

In the present work, polyelectrolyte multilayers (PEMs) and graphene sheets are applied to sequentially coat on the surface of hollow carbon spheres/sulfur composite by a flexible layer-by-layer (LBL) self-assembly strategy. Owing to the strong electrostatic interactions between the opposite charged materials, the coating agents are very stable and the coating procedure is highly efficient. The LBL film shows prominent impact on the stability of the cathode by acting as not only a basic physical barrier, and more importantly, an ion-permselective film to block the polysulfides anions by Coulombic repulsion. Furthermore, the graphene sheets can help to stabilize the polyelectrolytes film and greatly reduce the inner resistance of the electrode by changing the transport of the electrons from a "point-to-point" mode to a more effective "plane-to-point'' mode. On the basis of the synergistic effect of the PEMs and graphene sheets, the fabricated composite electrode exhibits very stable cycling stability for over 200 cycles at 1 A g(-1), along with a high average Coulombic efficiency of 99%. With the advantages of rapid and controllable fabrication of the LBL coating film, the multifunctional architecture developed in this study should inspire the design of other lithium-sulfur cathodes with unique physical and chemical properties.