Compared with liquid organic lithium-ion batteries, solid-state lithium-ion batteries have higher safety performance, so they are expected to become the next generation of energy storage devices and have attracted extensive research attention. The thermal management of the battery is a multi-coupling problem. Battery safety, cycle life, and even electrochemical reactions are all related to it. This Perspective presents the commonly used solid-state electrolytes and recent studies on their thermal stability and thermal transport properties. The thermal decomposition temperature and thermal conductivity are summarized, and we also present the summary and a brief outlook. This Perspective provides a reference for how to design and select high thermal conductive electrolyte materials, which is important for further advancement of solid-state lithium-ion batteries.
The thermal transport properties of porous graphene nanoribbons are studied by the non-equilibrium Green's function method. The results show that owing to the existence of nano-pores, the thermal conductance of porous graphene nanoribbons is much lower than that of graphene nanoribbons. At room temperature, the thermal conductance of zigzag porous graphene nanoribbons is only 12% of that of zigzag graphene nanoribbons of the same size. This is due to the phonon localization caused by the nano-pores in the porous graphene nanoribbons. In addition, the thermal conductance of porous graphene nanoribbons has remarkable anisotropy. With the same size, the thermal conductance of armchair porous graphene nanoribbons is about twice higher than that of zigzag porous graphene nanoribbons. This is because the phonon locality in the zigzag direction is stronger than that in the armchair direction, and even part of the frequency phonons are completely localized.
The layered solid electrolyte Li2ZrCl6 and Li metal electrodes have a very good contact stability, but the thermal transport properties of Li2ZrCl6 are still unclear. Here, we systematically study the intrinsic lattice thermal conductivity ( κp) of Li2ZrCl6 using the machine-learning potential approach based on first-principles calculations combined with the Boltzmann transport theory. The results show that the κp of Li2ZrCl6 at room temperature is 3.94 W/mK along the in-plane (IP) direction and 1.05 W/mK along the out-plane (OP) direction, which means that the κp is significantly anisotropic. In addition, under the compressive stress in the OP direction, the κp evolution along the IP and OP directions exhibits completely different trends, because the stress has a significant regulatory effect on the contribution of optical phonons to κp. With the increase in stress, the κp in the IP direction monotonically decreases, while the κp in the OP direction increases by a factor of 2.2 under a compressive strain of 13%. This is because the contribution of low-frequency optical phonons to κp in the IP direction is as high as 58% when no stress is applied, and this contribution is significantly suppressed with increasing compressive strain. However, the contribution of optical phonons in the OP direction to the κp increases with the increase in stress. Our results reveal the thermal transport properties of Li2ZrCl6 and the effect of the compressive strain on the κp of Li2ZrCl6, thereby providing a reference for the use of Li2ZrCl6 in Li-metal batteries.
The ability to tune the interfacial thermal conductance of GaN/AlN heterojunction nanowires with a core/shell structure is shown using molecular dynamics and nonequilibrium Green’s functions method. In particular, an increase in the shell thickness leads to a significant improvement of interfacial thermal conductance of GaN/AlN core/shell nanowires. At room temperature (300 K), the interfacial thermal conductance of nanowires with specific core/shell ratio can reach 0.608 nW/K, which is about twice that of GaN/AlN heterojunction nanowires due to the weak phonon scattering and phonon localization. Moreover, changing the core/shell type enables one to vary interfacial thermal conductance relative to that of GaN/AlN heterojunction nanowires. The results of the study provide an important guidance for solving the thermal management problems of GaN-based devices.
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