摘要
基于簇阴离子的反钙钛矿超离子导体由于其在可充电电池固态电解质中的应用前景而引起了人们的兴趣。但是,对其安全性和稳定性至关重要的热力学性能关注甚少。采用第一性原理计算系统地研究了反钙钛矿型X_(3)OBH_(4)(X=Li,Na)材料的电子结构、相稳定性、电化学稳定性、界面兼容性、机械性能和离子输运性质。计算结果表明,X_(3)OBH_(4)(X=Li,Na)在0 K下是热力学亚稳态且宽带隙的电子绝缘体,其在高压下是不稳定的。然而,相应的分解产物XBH4(X=Li,Na)具有宽的电化学稳定窗口,可以保护固态电解质。此外,X_(3)OBH_(4)(X=Li,Na)的低迁移势垒分别为0.34 eV和0.35 eV,室温离子电导率可达10^(-4)S/cm。超卤素的旋转促进了锂/钠离子的运动,从而提高了其离子电导率。这些发现为进一步设计高性能固态电解质提供了理论指导。
Introduction Compared with organic lithium-ion batteries,all-solid-state batteries are expected to improve battery safety and energy density simultaneously.They have attracted extensive attention.The ideal solid electrolyte material should have the basic properties of electronic insulation,wide electrochemical window,good interface compatibility and high ionic conductivity.Many types of solid electrolyte materials are reported,including oxides,sulfides,halides,borohydrides and phosphates,each of which has advantages and disadvantages.For instance,lithium-based halide and sulfide solid electrolytes have a high ionic conductivity but a narrow electrochemical window,and they are unstable to lithium metal negatives.The interface compatibility between oxide solid electrolyte and electrode is poor,and lithium dendrites grow rapidly along the grain boundary in oxide solid electrolyte.To further develop all-solid-state batteries with a higher energy density,a longer cycle life and a higher safety,solid electrolyte materials with excellent comprehensive performance must be designed.Anti-perovskite superionic conductors based on cluster anions have attracted much attention due to their potential applications in solid electrolytes for rechargeable batteries.However,little theoretical studies on the phase stability,electrochemical stability and interface compatibility of anti-perovskite X_(3)OBH_(4)(X=Li,Na)materials have been reported yet.In this work,the electronic structure,phase stability,electrochemical stability,interface compatibility,mechanical properties and ion transport properties of anti-perovskite X_(3)OBH_(4)(X=Li,Na)materials were systematically investigated via first-principles calculation.Methods All the calculations were performed based on density functional theory(DFT)by a projector augmented wave method,as implemented in the Vienna ab initio Simulation Package(VASP).The generalized gradient approximation(GGA)with Perdew–Burke–Ernzerhof(PBE)was applied to treat the electronic exchange-correlation interactions.The cutoff energy was set to 520 eV.The crystal structure was fully relaxed until the convergence criteria for each atomic force and energy were less than 0.02 eV/Åand 10^(–5) eV,respectively.Based on electrochemical energy storage materials design platform(bmaterials.cn),the phase stability and interfacial stability(including electrochemical and chemical stability)of X_(3)OBH_(4)(X=Li,Na)were evaluated.Results and discussion The results show that X_(3)OBH_(4)(X=Li,Na)is a thermodynamically metastable and wide-band insulator at 0 K,which is unstable at a high pressure.Based on the energy calculated by DFT,the phase diagrams of Na-NaBH_(4)-O_(2) and Li-LiBH_(4)-O_(2) are constructed,respectively,and the calculated Ehull of Li_(3)OBH_(4) and Na_(3)OBH_(4) is 52.4 meV/atom and 110.7 meV/atom,respectively.X_(3)OBH_(4)(X=Li,Na)is thermodynamically unstable at 0 K.Since the Ehull value is relatively small,it is possible to stabilize the compound through the regulation of external conditions such as high temperature,high pressure andhigh entropy.Based on the lithium(sodium)giant potential phase diagram of the constructed X-O-B-H quaternary system,thevoltage distribution and phase equilibrium of X_(3)OBH_(4)(X=Li,Na)in the process of lithiation/delithiation are calculated by DFT.The electrochemical window range of X_(3)OBH_(4)(X=Li,Na)is 0.53–0.93 V and 0–0.41 V,respectively.The correspondingdecomposition product XBH4(X=Li,Na)has a wide electrochemical stability window,which can protect the solid electrolyte.Thecalculated moduli of B,E and G of X_(3)OBH_(4)(X=Li,Na)are greater than those of lithium(sodium)metal or even Li3PS4electrolyte,indicating that X_(3)OBH_(4)(X=Li,Na)can effectively block the growth of lithium(sodium)dendrites and has a goodmechanical contact at the electrode/solid electrolyte interface.In addition,the low migration barriers of X_(3)OBH_(4)(X=Li,Na)are0.34 eV and 0.35 eV,respectively,and the ionic conductivity at room temperature can reach 10^(–4)S/cm.The rotation of thesuperhalogen promotes the movement of the lithium/sodium ions,thereby increasing their ionic conductivity.Conclusions The electronic properties,phase stability,electrochemical stability,chemical stability,mechanical properties andion transport mechanism of the anti-perovskite type X_(3)OBH_(4)(X=Li,Na)were systematically investigated via first-principlescalculation.The results showed that the crystal structure of X_(3)OBH_(4)(X=Li,Na)could be a metastable electronic insulator with awide band gap.Under electrochemical oxidation conditions,X_(3)OBH_(4)(X=Li,Na)could be thermodynamically unstable and easilyoxidized at relatively high voltages.However,the decomposition products could form a protective layer at the interface,preventing the electrolyte from further reacting and providing an improved electrochemical stability.In addition,X_(3)OBH_(4)(X=Li,Na)also had a good interface compatibility with typical cathode materials.The calculated mechanical properties indicated thatX_(3)OBH_(4)(X=Li,Na)was brittle.However,their relatively large shear modulus indicated that they could be stable forlithium/sodium metal dendrites growth.By CI-NEB calculation,X_(3)OBH_(4)(X=Li,Na)showed a low migration barrier.In summary,these theoretical results could favor to better understand the thermodynamic and kinetic processes of X_(3)OBH_(4)(X=Li,Na),andprovide a theoretical guidance for the development of high-performance solid electrolytes.
作者
刘波
钟微
蒋达国
伍冬兰
方成
肖志鹏
施思齐
LIU Bo;ZHONG Wei;JIANG Daguo;WU Donglan;FANG Cheng;XIAO Zhipeng;SHI Siqi(College of Mathematics and Physics,Jinggangshan University,Ji'an 343009,Jiangxi,China;School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China)
出处
《硅酸盐学报》
北大核心
2025年第7期1873-1884,共12页
Journal of The Chinese Ceramic Society
基金
国家自然科学基金(12464032)
江西省自然科学基金(20232BAB201032)。
关键词
反钙钛矿固态电解质
电化学稳定性
离子输运
第一性原理计算
antiperovskite solid electrolyte
electrochemical stability
ion transport
first principles calculations
