电双层电容孔隙渐变多孔电极电化学特性分析

针对渐变孔隙多孔结构电极的电双层电容器,将电极中电子电流传导和电解质溶液的扩散与迁移进行了耦合,建立了一维电化学电容物理模型,研究了电双层电容恒流充电恒压放电特性、恒功率充电下的电荷密度分布以及恒功率放电下的电流电压特性。研究结果表明,与常孔隙相比,采用渐变增加孔隙结构的电双层电容,在恒流充电及恒压放电的条件下,最大充电电压有所提高。达到最大电压时,充电时间缩短了60 s。不同周期响应时,达到恒定功率的时间缩短了15 s。在恒功率充电的条件下,电双层电流源最大提升了0.6×10^(6)A/m^(3),电荷密度变化幅度减小了0.5×10^(6)C/m^(3)。在恒功率放电时,放电电压提高了0.3 V。该研究结果可为电双层充电和电极利用率的提高提供参考价值。

Modulating composite polymer electrolyte by lithium closo-borohydride achieves highly stable solid-state battery at 25℃

Rational composite design is highly important for the development of high-performance composite polymer electrolytes(CPEs)for solid-state lithium(Li)metal batteries.In this work,Li closo-borohydride,Li_(2)B_(12)H_(12),is introduced to poly(vinylidene fluoride)-Li-bis-(trifluoromethanesulfonyl)imide(PVDF-LiTFSI)with a bound N-methyl pyrrolidone plasticizer to form a novel CPE.This CPE shows superb Li^(+)conduction properties,as evidenced by its conductivity of 1.43×10^(-4) S cm^(-1) and Li^(+)transference number of 0.34 at 25℃.Density functional theory calculations reveal that Li_(2)B_(12)H_(12),which features electron-deficient multicenter bonds,can facilitate the dissociation of LiTFSI and enhance the immobilization of TFSI to improve the Li^(+)conduction properties of the CPE.Moreover,the fabricated CPE exhibits excellent electrochemical,thermal,and mechanical stability.The addition of Li_(2)B_(12)H_(12) can help form a protective layer at the anode/electrolyte interface,thereby preventing unwanted reactions.The above benefits of the fabricated CPE contribute to the high compatibility of the electrode.Symmetric Li cells can be stably cycled at 0.2mA cm^(-2) for over 1200 h,and Li||LiFePO_(4) cells can deliver a reversible specific capacity of 140mAh g^(-1) after 200 cycles at 1C at 25℃ with a capacity retention of 98%.

Unlocking solid-state conversion batteries reinforced by hierarchical microsphere stacked polymer electrolyte

Pursuing all-solid-state lithium metal batteries with dual upgrading of safety and energy density is of great significance. However, searching compatible solid electrolyte and reversible conversion cathode is still a big challenge. The phase transformation at cathode and Li deformation at anode would usually deactivate the electrode-electrolyte interfaces. Herein, we propose an all-solid-state Li-FeF_(3) conversion battery reinforced by hierarchical microsphere stacked polymer electrolyte for the first time. This gC_(3)N_(4) stuffed polyethylene oxide(PEO)-based electrolyte is lightweight due to the absence of metal element doping, and it enables the spatial confinement and dissolution suppression of conversion products at soft cathode-polymer interface, as well as Li dendrite inhibition at filler-reinforced anode-polymer interface. Two-dimensional(2 D)-nanosheet-built porous g-C_(3)N_(4) as three-dimensional(3 D) textured filler can strongly cross-link with PEO matrix and Li TFSI(TFSI: bistrifluoromethanesulfonimide) anion, leading to a more conductive and salt-dissociated interface and therefore improved conductivity(2.5×10^(-4) S/cm at 60℃) and Li+transference number(0.69). The compact stacking of highly regular robust microspheres in polymer electrolyte enables a successful stabilization and smoothening of Li metal with ultra-long plating/striping cycling for at least 10,000 h. The corresponding Li/LiFePO_(4) solid cells can endure an extremely high rate of 12 C. All-solid-state Li/FeF_(3) cells show highly stabilized capacity as high as 300 m Ah/g even after 200 cycles and of 200 m Ah/g at extremely high rate of 5 C, as well as ultra-long cycling for at least 1200 cycles at 1 C. High pseudocapacitance contribution(>55%) and diffusion coefficient(as high as10^(-12) cm^(2)/s) are responsible for this high-rate fluoride conversion. This result provides a promising solution to conversion-type Li metal batteries of high energy and safety beyond Li-S batteries, which are difficult to realize true "all-solid-state" due to the indispensable step of polysulfide solid-liquid conversion.

Biomimetic brain-like nanostructures for solid polymer electrolytes with fast ion transport

The intrinsic drawbacks of electrolytes and the growth of lithium dendrites limit the development of commercial lithium batteries.To address the aforementioned challenges,a novel biomimetic brain-like nanostructure(BBLN)solid polymer electrolyte was created by manipulating the shape of the incorporated nanoparticles.Our designed BBLN solid polymer electrolyte was created by incorporating spherical core-shell(UIO-66@67)fillers into polymer electrolyte,which is significantly different from traditional polymer-based composite electrolytes.UIO-66@67 spherical nanoparticles are highly favorable to eliminating polymer electrolyte stress and deformation during solidification,indicating a great potential for fabricating highly uniform BBLN solid polymer electrolytes with a substantial number of continuous convolutions.Furthermore,spherical nanoparticles can significantly reduce the crystalline structure of polymer electrolytes,improving polymer chain segmental movement and providing continuous pathways for rapid ion transfer.As a result,BBLN solid polymer electrolyte shows excellent ionic conductivity(9.2×10^(−4)S cm^(−1)),a high lithium transference number(0.74),and outstanding cycle stability against lithium electrodes over 6500 h at room temperature.The concept of biomimetic brain-like nanostructures in this work demonstrates a novel strategy to enhance ion transport in polymerbased electrolytes for solid-state batteries.