Regulation of Lithium-Ion Flux by Nanotopology Lithiophilic Boron-Oxygen Dipole in Solid Polymer Electrolytes for Lithium-Metal Batteries

Inhomogeneous lithium-ion(Li^(+))deposition is one of the most crucial problems,which severely deteriorates the performance of solid-state lithium metal batteries(LMBs).Herein,we discovered that covalent organic framework(COF-1)with periodically arranged boron-oxygen dipole lithiophilic sites could directionally guide Li^(+)even deposition in asymmetric solid polymer electrolytes.This in situ prepared 3D cross-linked network Poly(ACMO-MBA)hybrid electrolyte simultaneously delivers outstanding ionic conductivity(1.02×10^(-3)S cm^(-1)at 30°C)and excellent mechanical property(3.5 MPa).The defined nanosized channel in COF-1 selectively conducts Li^(+)increasing Li^(+)transference number to 0.67.Besides,The COF-1 layer and Poly(ACMO-MBA)also participate in forming a boron-rich and nitrogen-rich solid electrolyte interface to further improve the interfacial stability.The Li‖Li symmetric cell exhibits remarkable cyclic stability over 1000 h.The Li‖NCM523 full cell also delivers an outstanding lifespan over 400 cycles.Moreover,the Li‖LiFePO_(4)full cell stably cycles with a capacity retention of 85%after 500 cycles.the Li‖LiFePO_(4)pouch full exhibits excellent safety performance under pierced and cut conditions.This work thereby further broadens and complements the application of COF materials in polymer electrolyte for dendrite-free and high-energy-density solid-state LMBs.

减缓自由阴离子迁移以缓解浓差极化用于高性能的聚合物锂金属电池

Traditional dual-ion lithium salts have been widely used in solid polymer lithium-metal batteries(LMBs).Nevertheless, concentration polarization caused by uncontrolled migration of free anions has severely caused the growth of lithium dendrites. Although single-ion conductor polymers(SICP) have been developed to reduce concentration polarization, the poor ionic conductivity caused by low carrier concentration limits their application. Herein, a dual-salt quasi-solid polymer electrolyte(QSPE), containing the SICP network as a salt and traditional dual-ion lithium salt, is designed for retarding the movement of free anions and simultaneously providing sufficient effective carriers to alleviate concentration polarization. The dual salt network of this designed QSPE is prepared through in-situ crosslinking copolymerization of SICP monomer, regular ionic conductor, crosslinker with the presence of the dual-ion lithium salt,delivering a high lithium-ion transference number(0.75) and satisfactory ionic conductivity(1.16 × 10^(-3) S cm^(-1) at 30 ℃). Comprehensive characterizations combined with theoretical calculation demonstrate that polyanions from SICP exerts a potential repulsive effect on the transport of free anions to reduce concentration polarization inhibiting lithium dendrites. As a consequence, the Li||LiFePO_4 cell achieves a long-cycle stability for 2000 cycles and a 90% capacity retention at 30 ℃. This work provides a new perspective for reducing concentration polarization and simultaneously enabling enough lithiumions migration for high-performance polymer LMBs.

Nonflammable PVDF-based gel polymer electrolytes modified by dimethyl methylphosphate for wide temperature range,long cycle-life and high-safety lithium metal batteries

Gel polymer electrolytes(GPEs)has been considered as a promising candidate for the development of lithium metal batteries(LMBs)with high energy density and high safety,yet most reported GPEs is flammable,making the LMBs still facing great safety hazards.Herein,we used dimethyl methylphosphate(DMMP)as the functional flame retardant and plasticizer for poly(vinylidene fluoride)(PVDF)matrix to develop a novel nonflammable PVDF-DMMP GPEs for LMBs.The DMMP not only highly enhances the flame resistance of PVDF-DMMP GPEs,the efficient dissociation of lithium salt and the rapid transport of lithium ions,but also helps to form stable and robust CEI/SEI layers.As a result,the ultrathin PVDF-DMMP GPEs(∼20µm)present superb flame resistance,high ionic conductivity(1.34×10^(−3) S cm^(−1) at 30℃),fast lithium ion transport(t_(Li^(+))=0.59at 30℃),high electrochemical stability voltage window(over 4 V)at 30–80℃ and uniform lithium deposition.When used in Li∥Li symmetric cells,Li∥LiFePO_(4)(LFP)and Li∥LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) full cells,the nonflammable PVDF-DMMP GPEs could endow these cells with long-term cycle stability,high rate capability,wide-temperature operation ranges(from−20 to 80℃)and high safety simultaneously.Even when suffering from harsh deconstructive tests,the Li∣PVDF-DMMP GPEs∣LFP pouch cells still work normally without any safety hazards.The actual energy density of the packed pouch cell is as high as 508 Wh kg^(−1).Therefore,our work can provide a promising strategy for the design of high safety and high-energy-density LMBs.

支柱策略增强离子传输和结构稳定性的KVPO4F用于超稳定的钾离子电池正极

近年来,由于丰富的钾资源储量和低廉的价格,钾离子电池在大规模储能领域表现出极大的应用前景.开发具有高安全性、高能量密度、低成本、长寿命的正极材料是推动钾离子电池实用化的关键.KVPO4F(KVPF)因其工作电压高、能量密度高、热稳定性好,被认为是一种很有前途的钾离子电池正极材料.然而,由于大半径的钾离子反复脱出/嵌入导致较慢的动力学和大的体积变化,从而影响材料循环稳定性.本文通过将大半径铯离子引入KVPF结构中的“支柱”策略,可有效提高材料的离子传导特性,并改善充放电过程中材料的结构稳定性,从而实现铯掺杂的KVPF正极优异的储钾性能.同时,高循环稳定性的KVPF//石墨全电池也展示了其在钾离子电池中巨大的实际应用潜力.

Robust hydrogel adhesives for emergency rescue and gastric perforation repair

Development of biocompatible hydrogel adhesives with robust tissue adhesion to realize instant hemorrhage control and injury sealing,especially for emergency rescue and tissue repair,is still challenging.Herein,we report a potent hydrogel adhesive by free radical polymerization of N-acryloyl aspartic acid(AASP)in a facile and straightforward way.Through delicate adjustment of steric hindrance,the synergistic effect between interface interactions and cohesion energy can be achieved in PAASP hydrogel verified by X-ray photoelectron spectroscopy(XPS)analysis and simulation calculation compared to poly(N-acryloyl glutamic acid)(PAGLU)and poly(N-acryloyl amidomalonic acid)(PAAMI)hydrogels.The adhesion strength of the PAASP hydrogel could reach 120 kPa to firmly seal the broken organs to withstand the external force with persistent stability under physiological conditions,and rapid hemostasis in different hemorrhage models on mice is achieved using PAASP hydrogel as physical barrier.Furthermore,the paper-based Fe^(3+)transfer printing method is applied to construct PAASP-based Janus hydrogel patch with both adhesive and non-adhesive surfaces,by which simultaneous wound healing and postoperative anti-adhesion can be realized in gastric perforation model on mice.This advanced hydrogel may show vast potential as bio-adhesives for emergency rescue and tissue/organ repair.

Computational study of transition metal single-atom catalysts supported on nitrogenated carbon nanotubes for electrocatalytic nitrogen reduction

Developing efficient and stable catalysts for the electrocatalytic N_(2)reduction reaction(NRR)shows promise in nitrogen fixation.Here,we proposed active and stable single-atom catalysts(SACs)toward NRR,where transition metals are anchored on nitrogenated carbon nanotubes(NCNTs).Among the screened nine common transition metals(Ti,V,Cr,Mn,Fe,Mo,Ru,Rh,and Ag)on(4,4)NCNTs,we found Mo-NCNT possesses the most excellent NRR catalytic activity and selectivity with a low overpotential of 0.29 V.Then,the NRR performance of Mo-NCNT was further engineered by controlling the nanotube diameter,where the lowest overpotential is 0.18 V at a diameter of 9.6Å.In addition,we found a linear scaling relation between*NNH and*NH_(2)on the studied catalysts with the exception of(2,2)and(3,3)Mo-NCNTs,owing to their extremely unstable structures.We attribute the outstanding NRR performance of Mo-NCNT to the moderate adsorption of N_(2)due to the slightly low d-band center of Mo,and the charge donating and accepting capacity of NCNTs.This work has provided a deeper insight into designing highefficiency and stable NRR SACs supported by NCNTs.