Stable cycling of LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)/lithium metal batteries enabled by synergistic tuning the surface stability of cathode/anode

Ni-rich layered oxides(LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2))show great potential in long-range and low-cost lithiumion batteries.However,due to the high surface sensitivity,their practical application is hindered by interfacial instability with electrolytes under high voltage for long cyclic life.Herein,by combining both firstprinciple calculations and time-of-flight secondary ion mass spectrometry(TOF-SIMS),a novel surface fluorinated reconstruction(SFR)mechanism is proposed to improve the interfacial stability under high voltage,which could effectively regulate the surface fluoride species to desensitize the LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)interface.We demonstrate here that by tuning the ratio of fluoride species,the LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)/Li battery could achieve excellent long-term and high voltage performance(163.5 mA h g^(-1)at 0.5 C for 300 cycles under 4.4 V),while the controlled sample decayed to 125.4 mA h g^(-1)after 300 cycles.Moreover,the favorable cross-talk effect induced by SFR further facilitates the incorporation of suitable amounts of Ni ions into the construction of stable solid electrolyte interface(SEI)layer for anode surface.Therefore,the ultra-long cycling stability under high voltage can be achieved by the robust cathode/electrolyte and Li/electrolyte interfaces,which results in excellent interfacial stability after long cycling.This work provides new insights into the surface design of cathode materials and improves the stability of the electrode-electrode interface under high voltage.

Hierarchical graphene@MXene composite foam modified with flower-shaped FeS for efficient and broadband electromagnetic absorption

Developing high-performance broadband microwave absorption material becomes an urgent concern in the field of electromagnetic protection.In this work,an ultralight magnetic composite foam was con-structed by electrostatic self-assembly of MXene on the surface of graphene skeletons,and subsequent hydrothermal anchoring of flower-shaped FeS clusters.Under the synergistic effect of MXene coating in-creasing conductive loss and FeS clusters improving magnetic loss,the rational construction of hierarchi-cal impedance structure in foam can effectively promote the entrance and consumption of more incident electromagnetic waves.The minimum reflection loss(RL min)reaches-47.17 dB at a thickness of 4.78 mm,and the corresponding effective absorption bandwidth(EAB)is up to 6.15 GHz.More importantly,the microwave absorption performance of composite foam can be further optimized by controlling the load-ing of MXene and thermal treatment at a low temperature.The maximum of EAB for GMF-300 can be extended to an unprecedented value of 11.20 GHz(covering 6.10-17.30 GHz).

Ultrathin,flexible,and oxidation-resistant MXene/graphene porous films for efficient electromagnetic interference shielding

Designing and fabricating efficient electromagnetic interference(EMI)shielding materials becomes a significant and urgent concern.Hence,a novel ultrathin,flexible,and oxidation-resistant MXene-based graphene(M-rGX)porous film is successfully fabricated by electrostatic self-assembly between MXene and graphene oxide(GO)nanosheets,and subsequently thermal annealing under hydrogen-argon atmosphere.The rapid breakaway of functional groups on GO and MXene sheets induces formation of porous conductive network in film,thereby facilitating efficient shielding for incident electromagnetic waves.The optimal absolute shielding effectiveness(SSE/t)value of 76,422 dB·cm2·g−1 can be achieved at a thinner thickness of 15μm.More importantly,the effective removal of functional groups on MXene conspicuously improves the oxidation resistance of the film,endowing it with an excellent durability(12 months)in EMI shielding performance.

Flashover Behavior of Cone-type Spacers with Inhomogeneous Temperature Distribution in SF_(6)/N_(2)-filled DC-GIL Under Lightning Impulse with DC Voltage Superimposed

Before designing DC gas insulated transmission lines(GIL),the insulation characteristics of spacers under a lightning impulse(LI)voltage with a superimposed DC voltage must be clarified.Many experiments have been performed to guide the development of the DC spacer.However,the impacts of thermal stresses on their insulation performance under combined voltage are always neglected,and little attention has been given to the insulation characteristics of spacers in an eco-friendly gas filled DC-GIL.To solve these problems,an experiment setup with the abilities to load the thermal field and the DC voltage with LI voltage superimposed on the cone-type spacer are built.After that,the insulation characteristics of spacers under the combined voltage of DC with lightning impulse at 0.1 MPa SF_(6)/N_(2) gas mixtures are investigated,under different thermal stress conditions.The experiment’s results indicate that:1)The flashover voltage of spacers under the same polarity superimposed voltages is slightly higher than that under LI alone.Conversely,the flashover voltage under reverse polarity superimposed voltages is lower than that under LI alone.2)The longer the duration of the foregoing DC voltage,the differences between the flashover voltage under superposed voltage and that under LI alone are larger.3)The combined flashover voltages are reduced under thermal stress.To ensure the insulation performance of newly designed DC spacers,the insulation test is suggested to be applied under thermal stress and combined voltage of the DC with lightning impulse,especially for superimposed reverse polarity.