确定电池材料的纳米力学特性进行故障分析亚博网站下载

可充电电池具有广泛的应用，会影响人们的生活质量；例如，这些电池用于医疗设备，智能手机，电动汽车，手持工具，玩具等。app亚博体育

增加电荷 - 放电周期的总数，提高能量密度并提高安全性方面，同时减轻体重和成本构成了可充电电池的持续开发。为了实现这些措施，需要新颖的材料和创新，例如在将其引入生产周期之前亚博网站下载必须进行严格测试的固态电池。

This high energy density can be very dangerous, and it is one of the reasons that a majority of devices are forbidden on commercial aircraft. Moreover, mechanical damage, such as separator penetration and brittle failure of the electrodes, can lead to significant releases of stored energy, like battery fires (see Figure 1).

图1。电池故障导致能量迅速释放的示例。

In addition, stresses arising from fabrication, mechanical (or ion)-induced stiffening and swelling, failures of coatings, and mechanical damage and stresses arising from numerous charge-discharge cycles represent considerable challenges in the development and integration of new devices. Therefore, for the sake of performance and safety reasons, it is essential to understand the mechanical performance of these devices, including every component at a suitable size scale.

Experiment

由于锂具有高电极电势，因此在电池电极中形成核心成分。相反，该元素对氮，氧气和水具有高度反应性，并在暴露于水分或水时会在氧气中点燃。结果，必须在受监管的环境中进行测试。布鲁克的hysitron^®TI 980 IO TriboIndenter^®这些实验使用的是，它提供了一个少于1 ppm的水分和氧气水平的受控大气（见图2）。

图2。息肌^®Ti 980 IO提供了大多数选项的兼容性，包括从-80°C到+800°C的温度，在受控的气体环境中，在低（下10μn）和高（最高10 n）载荷的凹痕。

Case A: Time-Dependent Deformation—Creep and Strain Rate Effects for 4N Lithium

When it comes to batteries, lithium metal is regarded as a suitable material because it has the lowest negative electromechanical potential and ultra-high theoretical specific capacity. Despite this, lithium is an exceptionally soft metal, showing time-dependent plastic deformation. In this regard, establishing the nanomechanical characteristics of battery materials, such as hardness and elastic modulus, and inferring nanomechanical behaviors, like the plastic flow of the emerging battery materials, are vital for failure analysis and hypothetical predictions.

使用钻石Berkovich的凹痕在连续的载荷应变速率条件下使用纯锂箔进行负载分位曲线计算（见图3A）。

图3。4N锂的应变速率的影响。计算了0.06的应变率指数：（a）应变速率对加载曲线的影响；（b）粘塑性，导致卸载时蠕变。即使是从5 MN的1秒卸载也会导致这种持续的粘塑性。更快的卸载速率（例如-50 MN/秒）必须应用于使用传统的卸载刚度来计算减少模量。

这种恒定的应变率可以定义为在哪里δis the depth andɛis the strain. Conversely, this can be simplified as在哪里pdenotes the load, provided the material has constant hardness with regards to depth. The strain rate sensitivity exponent, in this case, is found to be 0.06 — 10 times that of large-grained copper and twice that of nanocrystalline copper.

如图3B所示，这种压痕测量值在99.99％的锂箔上进行，也显示出粘膜塑料的粘膜特性。这种持续的塑性变形尽管减少了施加的负载，但对这些材料中的变形方式有了更深入的了解。亚博网站下载

案例B：高速机械属性映射

大多数情况下，用于固体电解质，阳亚博网站下载极和阴极的材料是具有微结构异质性的复合材料。在这里，机械稳定性在防止固体电解质的降解以及可能导致电池严重故障的电极中起着重要作用[1，2]。例如，硅电极在骑自行车时的体积膨胀超过300％[3]。因此，研究机械性能，例如电池材料的硬度（强度）和弹性模量，对于了解电池材料在充电和放电过程时的机械降解过程的发生很重要。亚博网站下载

Figure 4 shows maps of hardness and modulus achieved for lithium deposited on a copper working electrode.

图4。（a）模量和（b）硬度图显示了铜工作电极上电沉积锂膜的变化。

在25 x25μm上执行625个凹痕花了30分钟²使用布鲁克的区域加速属性映射（XPM™）技术。In this example, the viscoplastic effect on the unloading slope was resolved using unloading times of 100 ms. The distribution of the modulus and hardness across the sample is shown by the indentation maps in Figure 4. This spatial precision is partly due to the reduced indentation depth when compared to the thickness of the film and the size of the heterogeneity. The statistical distribution of modulus and hardness is shown in Figure 5.

图5。The distribution of (a) reduced modulus and (b) hardness of lithium deposited on copper electrode determined by 625 measurements。

Assuming numerous distributions, this data can be further examined to find out the average and also the maximum and minimum properties of the electrodeposited film.

结论

Using Bruker’sHysitron TI 980 IO测试套件, nanomechanical testing of battery materials was successfully carried out in a regulated, argon-filled environment. This initial study represents the instrument’s basic capabilities to enable mechanical characterization of emerging materials in a quantitative manner and also provides a better understanding to enhance mechanical performance.

参考

1. Müller, S., Pietsch, P., Brandt B., Baade P., Andrade, V., Carlo F., and Wood V.,Nature Comm.，9（2018），第1页。2340。
2. Xu R.，Sun H.，Vasconcelos L.和Zhao K.，J. Elecrochem. Soc.，164（2017），A3333。
3. Kumar R.，Lu P.，Xiao X.，Huang Z.和Sheldon B.，ACS Appl. Mater. Interfaces, 9 (2017), p. 28406.

该信息已从布鲁克·纳米（Bruker Nano）表面提供的材料中采购，审查和改编。亚博网站下载

For more information on this source, please visit布鲁克纳米表面。