【摘要】：目前,從微電子技術(shù)到交通運輸,可充電電池的使用越來越廣泛,要求也越來越苛刻,鋰離子電池已經(jīng)成為能量存儲和轉(zhuǎn)換設(shè)備中使用最廣泛的電池。但隨之而來的問題也不斷凸顯,其中,容量衰減成為限制鋰離子電池進一步發(fā)展的主要瓶頸。研究發(fā)現(xiàn),痕量水和過渡金屬離子的溶蝕對電池性能破壞非常嚴(yán)重。在鋰離子電池的生產(chǎn)制備過程中痕量水的存在是不可避免的,這會導(dǎo)致電池的不可逆容量損失,影響固體電解質(zhì)界面膜的形成,且會引起集流體和陰極材料的腐蝕。過渡金屬離子在正極的溶蝕,不僅導(dǎo)致正極可用活性材料損失,且溶蝕的金屬離子在電解液中遷移并沉積在負(fù)極,致使固體電解質(zhì)界面膜嚴(yán)重?fù)p害,還有部分金屬離子插入石墨層導(dǎo)致負(fù)極容量衰減。因此,探究痕量水和過渡金屬離子對電池性能破壞的機理和提出相對應(yīng)的抑制措施成為目前研究的重點。本論文主要進行以下三方面的研究。第一,以六氟磷酸鋰-碳酸乙烯酯/碳酸二乙酯電解液和雙草酸硼酸鋰-環(huán)丁砜/碳酸二乙酯電解液為研究對象,通過調(diào)節(jié)電解液中痕量水的含量,系統(tǒng)地研究電解液中不同含量的痕量水對鋰離子電池綜合性能的影響。若以100個循環(huán)后的容量保持率低于85%為電池失效的衡量標(biāo)準(zhǔn),則六氟磷酸鋰-碳酸乙烯酯/碳酸二乙酯和雙草酸硼酸鋰-環(huán)丁砜/碳酸二乙酯電解液中痕量水的臨界值分別為0.2113‰和0.5391‰。第二,采用商用電解液六氟磷酸鋰-碳酸乙烯酯/碳酸二乙酯作為參比電解液,研究雙草酸硼酸鋰作為電解質(zhì)鋰鹽對負(fù)極錳沉積的抑制作用。雙草酸硼酸鋰-環(huán)丁砜/碳酸二乙酯電解液體系具有優(yōu)異的成膜性,能在石墨電極表面形成致密的保護膜,可有效地抑制錳沉積。但當(dāng)電解液中錳濃度過高時由于存在電化學(xué)吸附的作用,所以固體電解質(zhì)界面膜表面仍有少量錳離子被檢測到。這些錳離子會催化電解液的分解,分解產(chǎn)物沉積在固體電解質(zhì)界面膜表面上,增加了電池阻抗,從而降低電池的循環(huán)穩(wěn)定性。通過前兩部分的研究,明確痕量水和金屬離子破壞電池性能的機理,并構(gòu)建新型的電解液體系來抑制電解液中痕量水和過渡金屬離子對電池造成的破壞。第三,利用噴霧沉積技術(shù),采用硫酸鋰水溶液對石墨電極表面進行預(yù)處理。經(jīng)硫酸鋰預(yù)處理的石墨電極組裝的半電池,不僅表現(xiàn)出優(yōu)異的循環(huán)性能和較高的容量保持率,還具有較低的界面阻抗。這種修飾處理對鋰離子電池性能改善有重要意義,同時從負(fù)極材料和固體電解質(zhì)界面膜的角度出發(fā),為抑制電解液中痕量水和過渡金屬離子對電池性能的破壞提供了一個新思路。
[Abstract]:At present, from microelectronics technology to transportation, rechargeable batteries are more and more widely used and demanding. Li-ion batteries have become the most widely used batteries in energy storage and conversion devices. However, the following problems have become increasingly prominent, among which capacity attenuation is the main bottleneck restricting the further development of lithium-ion batteries. It was found that the corrosion of trace water and transition metal ions seriously damaged the performance of the battery. The existence of trace water in the preparation of lithium-ion batteries is inevitable, which will lead to the irreversible loss of the battery capacity, affect the formation of solid electrolyte interfacial films, and cause the corrosion of the collector and cathode materials. The dissolution of transition metal ions at the positive electrode not only results in the loss of the active materials available for the positive electrode, but also the migration of the dissolved metal ions in the electrolyte and deposition in the negative electrode, resulting in serious damage to the solid electrolyte boundary film, Some of the metal ions inserted into the graphite layer lead to negative electrode capacity attenuation. Therefore, exploring the mechanism of trace water and transition metal ions destroying the performance of the battery and putting forward corresponding inhibition measures have become the focus of current research. This paper mainly carries on the following three aspects of research. Firstly, the lithium hexafluorophosphate-vinyl carbonate / diethyl carbonate electrolyte and the lithium oxalate borate-sulfolane / diethyl carbonate electrolyte were used as the research objects, and the content of trace water in the electrolyte was adjusted. The effect of trace water in electrolyte on the comprehensive performance of lithium ion battery was studied systematically. If the capacity retention rate of 100 cycles is less than 85%, The critical values of trace water in lithium-hexafluorophosphate-vinyl carbonate / diethyl carbonate and lithium borate bisoxalate / diethyl carbonate electrolyte are 0.2113 鈥，

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