Electro-chemo-mechanical analysis of the effect of bending deformation on the interface of flexible solid-state battery

Flexible solid-state battery has several unique characteristics including high flexibility,easy portability,and high safety,which may have broad application prospects in new technology products such as rollup displays,power implantable medical devices,and wearable equipments.The interfacial mechanical and electrochemical problems caused by bending deformation,resulting in the battery damage and failure,are particularly interesting.Herein,a fully coupled electro-chemo-mechanical model is developed based on the actual solid-state battery structure.Concentration-dependent material parameters,stress-dependent diffusion,and potential shift are considered.According to four bending forms(k=8/mm,0/mm,-8/mm,and free),the results show that the negative curvature bending is beneficial to reducing the plastic strain during charging/discharging,while the positive curvature is detrimental.However,with respect to the electrochemical performance,the negative curvature bending creates a negative potential shift,which causes the battery to reach the cut-off voltage earlier and results in capacity loss.These results enlighten us that suitable electrode materials and charging strategy can be tailored to reduce plastic deformation and improve battery capacity for different forms of battery bending.

Electro-chemo-mechanical design of polymer matrix in composited LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode endows solid-state batteries with superior performance

Nickel-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) cathode material has been widely concerned due to its high voltage,high specific capacity and excellent rate performance,which is considered as one of the most promising cathode materials for the next generation of high-energy-density solid-state lithium batteries.However,serious electro-chemo-mechanical degradation of Nickel-rich cathode during cycling,especially at a high voltage(over 4.5 V),constrains their large-scale application.Here,using the multiphysical simulation,highly-conductive polymer matrix with spontaneous stress-buffering effect was uncovered theoretically for reinforcing the electrochemical performance of composited NCM81 1 cathode through the visualization of uniform concentration distribution of Li-ion coupled with improved stress field inside NCM811 cathode.Thereupon,polyacrylonitrile(PAN) and soft polyvinylidene fluoride(PVDF) were selected as the polymer matrix to fabricate the composited NCM811 cathode(PVDFPAN@NCM811) for improving the electrochemical performance of the solid-state NMC811|Li full cells,which can maintain high capacity over 146.2 mA h g^(-1)after 200 cycles at a high voltage of 4.5 V.Suggestively,designing a multifunctional polymer matrix with high ionic conductivity and mechanical property can buffer the stress and maintain the integrity of the structure,which can be regarded as the door-opening avenue to realize the high electrochemical performance of Ni-rich cathode for solidstate batteries.

Viability of all-solid-state lithium metal battery coupled with oxide solid-state electrolyte and high-capacity cathode

Owing to the utilization of lithium metal as anode with the ultrahigh theoretical capacity density of 3860 mA h g^(-1)and oxide-based ceramic solid-state electrolytes(SE),e.g.,garnet-type Li7La_(3)Zr_(2)O_(12)(LLZO),all-state-state lithium metal batteries(ASLMBs)have been widely accepted as the promising alternatives for providing the satisfactory energy density and safety.However,its applications are still challenged by plenty of technical and scientific issues.In this contribution,the co-sintering temperature at 500℃is proved as a compromise method to fabricate the composite cathode with structural integrity and declined capacity fading of LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM).On the other hand,it tends to form weaker grain boundary(GB)inside polycrystalline LLZO at inadequate sintering temperature for LLZO,which can induce the intergranular failure of SE during the growth of Li filament inside the unavoidable defect on the interface of SE.Therefore,increasing the strength of GB,refining the grain to 0.4μm,and precluding the interfacial defect are suggested to postpone the electro-chemo-mechanical failure of SE with weak GB.Moreover,the advanced sintering techniques to lower the co-sintering temperature for both NCM-LLZO composite cathode and LLZO SE can be posted out to realize the viability of state-of-the-art ASLMBs with higher energy density as well as the guaranteed safety.

商业锂电池充电倍率与循环寿命的标度律

商用锂电池的健康管理目前存在大量亟待解决的问题,其中循环寿命的有效预测是电池管理系统的核心目标.本文通过利用商业锂电池不同快充倍率下循环寿命的实验结果,发现并提出了锂电池等效快充倍率c与循环寿命N之间的标度律关系,c=c_(0)N^(b)(即c-N准则),其中c_(0)表示电极材料极限充电倍率,b是与电池材料相关的常数.这一c-N准则,类似于固体材料疲劳中所周知的S-N曲线,适用于不同类型的商业锂电池,并通过已有的文献数据获得了验证.结合c-N准则和机器学习方法,我们发展了一种物理增强的机器学习模型,基于前面提出的c-N准则,使用首圈的充放电测试即可实现对电池循环寿命的高精度预测.这一工作为锂电池循环寿命预测、健康管理和锂电池的优化提供了基于力学原理的新思路.

Artificial muscles driven by the cooperative actuation of electrochemical molecular machines.Persistent discrepancies and challenges

Here we review the persisting conceptual discrepancies between different research groups working on artificial muscles based on conducting polymers and other electroactive material.The basic question is if they can be treated as traditional electro-mechanical(physical)actuators driven by electric fields and described by some adaptation of their physical models or if,replicating natural muscles,they are electro-chemo-mechanical actuators driven by electrochemical reaction of the constitutive molecular machines:the polymeric chains.In that case the charge consumed by the reaction will control the volume variation of the muscular material and the motor displacement,following the basic and single Faraday’s laws:the charge consumed by the reaction determines the number of exchanged ions and solvent,the film volume variation to lodge/expel them and the amplitude of the movement.Deviations from the linear relationships are due to the osmotic exchange of solvent and to the presence of parallel reactions from the electrolyte,which originate creeping effects.Challenges and limitations are underlined.