Surface engineering of P2-type cathode material targeting long-cycling and high-rate sodium-ion batteries

The widespread interest in layered P2-type Mn-based cathode materials for sodium-ion batteries(SIBs)stems from their cost-effectiveness and abundant resources.However,the inferior cycle stability and mediocre rate performance impede their further development in practical applications.Herein,we devised a wet chemical precipitation method to deposit an amorphous aluminum phosphate(AlPO_(4),denoted as AP)protective layer onto the surface of P2-type Na_(0.55)Ni_(0.1)Co_(0.7)Mn_(0.8)O_(2)(NCM@AP).The resulting NCM@5AP electrode,with a 5 wt%coating,exhibits extended cycle life(capacity retention of78.4%after 200 cycles at 100 mA g^(-1))and superior rate performance(98 mA h g^(-1)at 500 mA g^(-1))compared to pristine NCM.Moreover,our investigation provides comprehensive insights into the phase stability and active Na^(+)ion kinetics in the NCM@5AP composite electrode,shedding light on the underlying mechanisms responsible for the enhanced performance observed in the coated electrode.

P2-Na_(2/3)Ni_(2/3)Te_(1/3)O_(2)Cathode for Na-ion Batteries with High Voltage and Excellent Stability

Air-stable layered structured cathodes with high voltage and good cycling stability are highly desired for the practical application of Na-ion batteries.Herein,we report a P2-Na_(2/3)Ni_(2/3)Te_(1/3)O_(2) cathode that is stable in ambient air with an average operating voltage of~3.8 V,demonstrating excellent cycling stability with a capacity retention of more than 92.7%after 500 cycles at 20 mA g^(-1) and good rate capability with 91.9%capacity utilization at 500 mA g^(-1) with respect to capacity at 5 mA g^(-1) between 2.0 and 4.0 V.When the upper cutoff voltage is increased to 4.4 V,P2-Na_(2/3)Ni_(2/3)Te_(1/3)O_(2) delivers a reversible capacity of 71.9 mAh g^(-1) and retains 91.8%of the capacity after 100 cycles at 20 mA g^(-1).The charge compensation during charge/discharge is mainly due to the redox couple of Ni^(2+)/Ni^(3+)in the host with a small amount of contribution from oxygen.The stable structure of the material without phase transformation and with small volume change during charge-discharge allows it to give excellent cycle performance especially when the upper cutoff voltage is not higher than 4.2 V.

Bidirectional Clone Node Model of Optimizing Performance of Structured P2P Overlay Network

In order to reduce the maintenance cost of structured Peer-to-Peer (P2P),Clone Node Protocol (CNP) based on user behavior is proposed.CNP considers the regularity of user behavior and uses the method of clone node.A Bidirectional Clone Node Chord model (BCNChord) based on CNP protocol is designed and realized.In BCNChord,Anticlockwise Searching Algorithm,Difference Push Synchronize Algorithm and Optimal Maintenance Algorithm are put forward to increase the performances.In experiments,according to the frequency of nodes,the maintenance cost of BCNChord can be 3.5%～32.5% lower than that of Chord.In the network of 212 nodes,the logic path hop is steady at 6,which is much more prior to 12 of Chord and 10 of CNChord.Theoretical analysis and experimental results show that BCNChord can effectively reduce the maintenance cost of its structure and simultaneously improve the query efficiency up to (1/4)O(logN).BCNChord is more suitable for highly dynamic environment and higher real-time system.

Increasing(010) active plane of P2-type layered cathodes with hexagonal prism towards improved sodium-storage

Na-ion cathode materials with a fast charge and discharge behavior are needed to develop future high energy sodium-ion batteries(SIBs).However,inevitably complicated phase transitions and sluggish kinet ics during insertion and removal of Na+in P_(2)-type layered transition metal oxides generate structura instability and severe capacity decay.To get rid of such a dilemma,we report a structural optimization strategy to promote P2-type layered transition metal oxides with more(010)active planes as an efficien cathode for SIBs.As a result,as-prepared hexagonal-prism P2-type layered Na_(0.71)Ni_(0.16)Li_(0.09)Co_(0.16)Mn0.6O_(2)cathode with more(010)active planes delivers a reversible capacity of 120.1 mAh/g at 0.1 C,impressive rate capability of 52.7 m Ah/g at 10 C,and long-term cycling stability(capacity retention of 95.6%ove200 cycles).The outstanding electrochemical performance benefited from the unique hexagonal-prism with more(010)active facets,which can effectively shorten the diffusion distances of Na+,increase the Na-ion migration dynamics and nanostructural stability during cycling verified by morphology character ization,Rietveld refinement,GITT,density functional theory calculations and operando XRD.

In sight of K-deficient layered K_(x)MnO_(2) cathode for potassium-ions batteries

Potassium-ions batteries(PIBs)are attracting increasing attention as up-and-coming youngster in largescale grid-level energy storage benefiting from its low-cost and high energy density.Nevertheless,enough researches regarding indispensable cathode materials for PIBs are badly absent.Herein,we synthesize K-deficient layered manganese-based oxides(P2-K_(0.21)MnO_(2) and P3-K_(0.23)MnO_(2))and investigate them as cathode of PIBs for the first time.As the newcomer of potassium-containing layered manganese-based oxides(K_(x)MnO_(2))group,P2-K_(0.21)MnO_(2) delivers high discharge capacity of 99.3 mAh g^(-1) and P3-K_(0.23)MnO_(2) exhibits remarkable capacity retention rate of 75.5%.Besides,in-situ XRD and ex-situ XRD measurements reveal the reversible phase transition of P2-K_(0.21)MnO_(2) and P3-K_(0.23)MnO_(2) with the potassium-ions extraction and reinsertion,respectively.This work contributes to a better understanding for the potassium storage in K-deficient layered K_(x)MnO_(2)(x≤0.23),possessing an important basic scientific significance for the exploitation and application of layered K_(x)MnO_(2) in PIBs.