Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries(LIBs).However,the effect of safety valve type on the thermal runaway(TR)and gas venting behavior of LIBs,as well as the TR hazard severity of LIBs,are not known.In this paper,the TR and gas venting behavior of three 100 A h lithium iron phosphate(LFP)batteries with different safety valves are investigated under overheating.Compared to previous studies,the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types.Two significant results are obtained:(Ⅰ)the safety valve type dominates over gas venting pressure of battery during safety venting,the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa,which is one order of magnitude higher than other batteries with oval or cavity safety valve;(Ⅱ)the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process.This study reveals the effect of safety valve type on TR and gas venting,providing a clear direction for the safety valve design.

多级钯-铜-银多孔纳米花作为高效电催化剂催化CO_(2)还原为C_(2+)产物

近年来,具有可控元素分布的铜基多金属纳米晶作为CO_(2)还原反应(CO_(2)RR)的电催化剂,受到了广泛研究。通过对铜电催化剂进行二次甚至多次的金属元素修饰,能够有效改变其整体d带结构并引起d带中心的位移。这种变化可以影响铜对关键中间体的表面亲和力,从而影响后续的催化途径。除了调整电子结构,形貌工程也成为提高CO_(2)RR电催化性能的有效手段。相对于随机形状的球形颗粒,基于二维纳米片构建的三维多孔结构有利于最大限度地暴露表面原子,为催化过程中产生的关键中间体提供丰富的扩散通道和反应中心。然而,通过设计合成路线构建这种类型的纳米结构是一项技术挑战,传统的分步自组装策略耗时且难以精确控制结构。因此,我们的研究旨在实现高纯度的合成方法,制备这种独特的纳米结构,并精确调控元素组成和电子结构,以探索结构优势与CO_(2)RR电化学性能改善之间的潜在关系,具有重要的应用价值。在此研究中,我们合理设计了钯-铜-银(Pd-Cu-Ag)纳米晶的二维-三维杂化结构,实现了可控的合成过程,并验证了其在电化学CO_(2)还原中的应用潜力。合成过程中,通过使用封装剂十八烷基三甲基氯化铵,成功地将Au@Cu_(x)O纳米球转化为层状CuAg纳米花(HNFs)。有趣的是,该过程中原位形成了作为构建单元的纳米薄片。通过对CuAg HNFs与Na_(2)PdCl_(4)进行电偶置换,除去了Ag和Cu,引入了零价的Pd,并在纳米片上形成了大量孔隙。我们对这些CuAg电催化剂进行了CO_(2)RR测试,结果显示Pd_(0.7)Cu_(40.0)Ag_(59.7)PHNs在C_(2+)产物选择性(69.5%)和C_(2+)分电流密度(-349.1mA·cm^(-2))方面表现出最佳性能。密度泛函理论(DFT)模拟表明,PdAgCu表面具有独特的电子性质,降低了C-C偶联反应的能垒,凸显了Pd掺杂对CuAg电催化剂CO_(2)还原的卓越性能。本研究为基于多孔纳米薄片构建多层次多金属纳米结构提供了一种直观方法,并验证了其在电催化方面的结构优势,为高效的CO_(2)RR催化剂的合理设计提供了依据。