【作者】 张辉；

【导师】 张嘉恒；

【作者基本信息】 哈尔滨工业大学 ， 材料加工（专业学位）， 2024， 硕士

【摘要】 高能量密度电池需求逐渐增长,石墨负极的锂离子电池由于能量密度较低,已经无法满足要求,目前广泛应用于阳极中的是高比容量、低氧化还原电位的锂金属电池。锂金属电池的性能会受到电解液的影响,目前常用的电解液主要是有机碳酸酯（链状和环状碳酸酯的混合物）,其与锂金属阳极界面相容性较差,在电池充放电过程中存在各种副反应,锂库伦效率低且生成的锂枝晶可能引起电池短路。此外,碳酸酯电解液易燃,电池短路后易引发火灾,有一定的安全隐患。深共晶电解液是由两种或者两种以上的氢键受体和氢键供体按照一定比例混合而成的新型电解液,具有低蒸气压、热稳定性和化学稳定性好、不易燃、电化学窗口宽等优点,可以解决上述问题,有望取代传统的有机碳酸酯电解液。本课题开发了一种具有良好界面相容性的不易燃深共晶电解液,提高了锂金属电池的性能。提出了一种二苯甲酮（BP）/双三氟甲磺酰亚胺锂（LiTFSI）深共晶电解液,该电解液通过Li-O相互作用诱导深共晶结构,适用于锂金属电池且具备不易燃性和长循环性能。该电解液具有5.0 V的氧化电压和0.44的锂离子迁移数,同时诱导形成了稳定的界面化合物Li-F和Li-N,抑制锂枝晶生长,具有良好的锂金属相容性,可以在Li||Li对称电池中保持长达1500小时的稳定性和低过电势。Li||LFP（磷酸铁锂）全电池测试中,表现出近似1 M LiPF₆ in EC/DMC/EMC（商用电解液）的室温性能,且在50℃高温下循环800圈后容量保持率为88%。通过引入二氟草酸硼酸锂（LiDFOB）于BP/LiTFSI深共晶电解液,提出了了一种实现铝集流体腐蚀抑制且适用于（高压钴酸锂）HLCO电极材料的双盐深共晶电解液。LiDFOB通过Li-O相互作用参与到深共晶结构的形成,引入LiDFOB后电解液保有不易燃性和良好的锂金属相容性,可以在Li||Li对称电池中保持长达1000小时的稳定性和低过电势。此外引入LiDFOB后电解液可以诱导Al表面形成Al-F和B-O化合物,提高了Al集流体腐蚀电位,实现了Al集流体腐蚀保护。在Li||HLCO全电池性能测试中,循环200圈并表现出94%的容量保持率,实现了HLCO的高压容量释放。更多还原

【Abstract】 The demand for high-energy density batteries is steadily increasing,and graphite-based negative electrode lithium-ion batteries,due to their lower energy density,are no longer meeting the requirements.Lithium metal batteries,characterized by high specific capacity and low redox potential,are now widely utilized in the anode.However,the performance of lithium metal batteries is influenced by the electrolyte.Currently,commonly used electrolytes primarily consist of organic carbonates(a mixture of linear and cyclic carbonates),which exhibit poor compatibility with the lithium metal anode.During the charge-discharge process of the battery,various side reactions occur,resulting in low lithium Coulombic efficiency and the potential formation of lithium dendrites,which can lead to short circuits.Additionally,carbonate electrolytes are flammable,posing safety hazards such as fire risk in the event of a short circuit.Deep eutectic electrolytes,composed of two or more hydrogen bond acceptors and donors mixed in specific proportions,represent a novel electrolyte solution.They possess advantages such as low vapor pressure,good thermal and chemical stability,non-flammability,and a wide electrochemical window,making them promising candidates to replace traditional organic carbonate electrolytes.This study developed a non-flammable deep eutectic electrolyte with excellent interface compatibility,thereby enhancing the performance of lithium metal batteries.A deep eutectic electrolyte composed of benzophenone(BP)and lithium bis(trifluoromethanesulfonyl)imide(LiTFSI)was proposed.This electrolyte induces a deep eutectic structure through Li-O interactions,making it suitable for lithium metal batteries while exhibiting non-flammability and long cycling performance.The electrolyte possesses an oxidation voltage of 5.0 V and a lithium ion transference number of 0.44.Moreover,it induces the formation of stable inte rface compounds,Li-F and Li-N,inhibiting the growth of lithium dendrites and demonstrating excellent lithium metal compatibility.In symmetrical Li||Licells,the electrolyte maintains stability and low overpotential for up to 1500 hours.In Li||LFP(lithium iron phosphate)full-cell tests,it exhibits comparable performance to a commercial electrolyte containing approximately 1 M LiPF 6 in EC/DMC/EMC solvent at room temperature,with a capacity retention of 88% after 800 cycles at50°C.By introducing lithium difluoro(oxalato)borate(LiDFOB)into the BP/LiTFSI deep eutectic electrolyte,a corrosion-inhibiting binary salt deep eutectic electrolyte suitable for high voltage lithium cobalt oxide(HLCO)electrode materials was proposed.LiDFOB participates in the formation of the deep eutectic structure through Li-O interactions.The electrolyte retains non-flammability and excellent lithium metal compatibility after the introduction of LiDFOB,maintaining stability and low overpotential for up to 1000 hours in symmetrical Li||Licells.Additionally,the introduction of LiDFOB induces the formation of Al-F and B-O compounds on the aluminum surface,raising the corrosion potential of the aluminum current collector and achieving corrosion protection.In Li||HLCO f ull-cell performance tests,a capacity retention of 94% was achieved after 200 cycles,demonstrating high voltage capacity release for HLCO.更多还原