Good Solid‐State Electrolytes Have Low, Glass‐Like Thermal Conductivity

Abstract

Lithium-ion batteries (LIBs) are widely used for electrical energy storage. The kinetics of charge transport, intercalation, and chemical reactions [1,2] in LIBs are strongly dependent on temperature. These processes, in turn, control cell round-trip efficiency and cycle life. For example, side reactions that irreversibly consume Li ions, for example, electrolyte decomposition, are accelerated at high temperatures. Furthermore, exposure of a battery to elevated temperatures, while beneficial for fast charging, leads to significant safety risks due to the potential for electrolyte decomposition, oxygen release by cathode materials, and if heat cannot be removed at an appropriate rate, thermal runaway. Greater understanding of the thermal properties of battery materials will facilitate advances in the engineering design and thermal management of LIBs is needed to improve safety and performance.The thermal properties of materials used in liquid-electrolyte-based batteries were summarized by Kantharaj et al. at both the device and material levels. [2] An additional level of complexity is created by the fact that the thermal conductivity of cathodes and anodes are known to depend on the state of charge, for example, the thermal conductivities of LiCoO 2 and graphite depend on Li composition. [3] From the cell assembly perspective, interfaces play a significant role in heat transfer. [4] For example, Lubner et al. characterized thermal resistances in a pouch-cell and showed that the thermal resistance of the separator-electrode interfaces accounts for up to 65% of the total thermal resistance within the cell. [4] Solid-state batteries (SSBs) are under intense investigation as safer, more robust, and higher energy-density alternatives to liquid-electrolyte-based LIBs. Similar to their liquidelectrolyte-based counterparts, SSBs also require thermal management strategies for dissipation of heat, especially in large, high-energy cell stacks. [2,5,6] If lithium metal is used as the SSB anode, which is highly attractive due to lithium's low reduction potential (−3.04 V vs standard-hydrogen-electrode) and high specific capacity (3860 mAh g −1 ), [7] temperature control becomes particularly important, as control of internal temperature distributions enhances the homogeneity of Li deposition and suppresses the formation of dendrites. [6] In Thermal management in Li-ion batteries is critical for their safety, reliability, and performance. Understanding the thermal conductivity of the battery materials is crucial for controlling the temperature and temperature distribution in batteries. This work provides systemic quantitative measurements of the thermal conductivity of three important classes of solid electrolytes (SEs) over the temperature range 150 < T < 350 K. Studies include the oxides

Coupling between Voltage Profiles and Mechanical Deformations in LAGP Solid Electrolyte During Li Plating and Stripping

“…Elastic modulus, E, and Poisson's ratio, v, for LAGP were reported as 144 GPa and 0.25, respectively. 31 When considering the relationship between stress and strains, our experimental measurements on the correlation between overpotential and strains in the interphase layer align very well with the predictions in the mathematical model. The nonuniform growth of the interphase layer accelerates at higher currents, which leads to the chemo-mechanical failure in the solid electrolytes.…”

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

“…Furthermore, Cheng et al recently reported “glass‐like” thermal transport behavior of different Li + and Na + solid electrolyte classes, which is consistent with diffuson transport. [ 20 ]…”

“…Furthermore, Cheng et al recently reported "glass-like" thermal transport behavior of different Li + and Na + solid electrolyte classes, which is consistent with diffuson transport. [20] Generally, there are strong underlying physical similarities between thermal diffusons and ionic diffusion: 1) fast ionic transport is achieved in strongly disordered materials [22,24] and strong disorder promotes the prevalence of thermal transport via diffusons. [15] 2) Both transport phenomena operate within an atomic-scale random walk, in which local vibrations carry and transfer thermal energy or momentum of ions (Figure 1).…”

“…[16] Fast ion transport has also been associated with diffuson-like signatures in inelastic neutron scattering experiments and ab initio molecular dynamics calculations. [4,9] As complexity, anharmonicity, and fast ion transport, are commonly found in both state-of-the-art solid electrolytes for battery applications, e.g., Na 3 PS 4 and Li 6 PS 5 Cl, [19][20][21] and promising thermoelectric materials such as Ag 9 GaSe 6 , Cu 2 Se and (Ag,Cu)CrSe 2 , [1,4,5,10,20,[22][23][24] there is an outstanding question if diffusons play a significant role in their thermal conductivity. In fact, many Ag + and Cu + conducting argyrodites have thermal conductivities below the theoretical "minimum" thermal conductivity proposed for purely propagating transport, [10,11,25,26] which may be explained…”

The Coupling between Voltage Profiles and Mechanical Deformations in LAGP Solid Electrolyte During Li Plating and Stripping

“…Bulk modulus can be calculated via 𝐾 = 𝐸/[3(1 − 2𝑣)]. Elastic modulus, 𝐸 and Poisson's ratio, 𝑣 for LAGP were reported as 144 GPa and 0.25, respectively 29 . When considering the relationship between stress and strains, our experimental measurements on the correlation between overpotential and strains in the interphase layer aligns very well with the predictions in the mathematical model.…”