CN117317165A - 一种MnO-LiF/C复合物及其制备方法和应用 - Google Patents
一种MnO-LiF/C复合物及其制备方法和应用 Download PDFInfo
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- 150000001875 compounds Chemical class 0.000 title claims abstract description 65
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 28
- 239000011572 manganese Substances 0.000 claims abstract description 27
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 24
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- CESXSDZNZGSWSP-UHFFFAOYSA-L manganese(2+);diacetate;tetrahydrate Chemical compound O.O.O.O.[Mn+2].CC([O-])=O.CC([O-])=O CESXSDZNZGSWSP-UHFFFAOYSA-L 0.000 claims description 21
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 19
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Abstract
本发明属于储能技术领域,本发明提供了一种MnO‑LiF/C复合物及其制备方法和应用,制备方法包含如下步骤:将含锰化合物、含锂化合物、聚四氟乙烯混合,得到前驱体粉末;将前驱体粉末顺次进行热处理、烧结反应,得到MnO‑LiF/C复合物。本发明利用聚四氟乙烯分解形成的残留碳对MnO‑LiF复合物进行碳原位包覆,以聚四氟乙烯为氟源和碳源,在烧结过程中原位生成的MnO纳米颗粒、LiF纳米颗粒、纳米碳颗粒三种组分均匀分布,有利于建立适合的表面转化反应进行的纳米活性微区,提高活性组分的利用率。
Description
技术领域
本发明涉及储能技术领域,尤其涉及一种MnO-LiF/C复合物及其制备方法和应用。
背景技术
基于嵌入化合物的锂离子电池在先进便携式储能市场已占据主导地位。这些锂离子电池正极材料属于含有氧化还原活性的过渡金属和Li+传导通道的晶体。而对于晶体结构中不含Li+传导通道或无锂的材料而言,由于其不能可逆嵌锂或必须用金属锂作为负极,所以很少用作正极。这些制约因素不仅大幅度限制了正极材料的选择,也阻碍了锂离子电池新型电极材料的发展。而用不含锂的过渡金属氧化物MO(如FeO、MnO、NiO、Mn2O3、NiMn2O4等)作为锂离子电池正极活性物质成为了另外一种选择,通过将MO和含锂的离子化合物LiF在纳米尺度上混合而形成纳米复合物。在纳米复合物中,MO提供电化学反应的氧化还原电对,锂离子则由LiF提供。例如,MnO-LiF体系的充放电反应可表示为式⑴的反应式。
由式⑴可知,通过充电反应后MnO和LiF转化为金属氟氧化物MnO…F,其中LiF的Li+和F-分别作为载流子和电荷中和剂参与锰元素的氧化还原反应,MnO同时作为氧化还原电对和F-受体。另外,MnO还作为促进LiF分裂的催化剂。与常规的转化正极材料相比,MO-LiF复合物的化学和结构变化主要集中在MO表面,因此这类转化反应被归类为表面转化反应。这一策略由于不仅不依赖于特定的晶体结构,而且可以突破嵌入化合物LiMO2已达到的~250mAh/g的比容量壁垒,因而受到关注。尤其是MnO-LiF纳米复合物体系,其Mn3+/Mn2+(氧化还原电位~2.5V)和Mn4+/Mn3+(氧化还原电位~3.75V)电对均参与了电化学反应,在1.5~4.8V电压区间以20mA/g电流密度充放电时,可逆比容量可以达到~240mAh/g。因此MnO-LiF体系的表面转化反应可以利用过渡金属的多价态氧化还原反应,从而获得更高的放电比容量和能量密度。
与过渡金属离子和锂离子位于同一个晶畴内的嵌入型正极活性物质不同,在MnO-LiF复合物中,过渡金属离子和锂离子在空间上被分隔在MnO和LiF两个不同的晶畴内,即锂源和电子源在空间上处于分离状态。因此,如何实现锂源与MnO纳米级的均匀分散和紧密接触,建立适合的表面转化反应进行的纳米活性微区,则是一个非常关键的问题。目前,MnO-LiF纳米复合物大多采用高能球磨法制备。这种方法简易可行,但若不加入有效的研磨剂,一般难以达到优化转换反应性能的尺寸要求,不容易实现MnO和LiF两相在纳米尺度下的均匀分散和紧密接触。虽然专利CN202110132662.4使用氟化铵进行氟化反应制备了MnO和LiF均匀分布的复合物,但由于氟化铵遇热水即分解成氨和有腐蚀性的氟化氢,因此,在喷雾干燥法制备前躯体粉末的过程中存在形成具有腐蚀性、在一般情况下很难处理的氟化氢气体的风险。另外,由于氟化剂NH4F和原料中醋酸锂的分解温度相差较大(NH4F分解温度在145~165℃之间,S Kim,et al.Defect engineering via the F-doping ofβ-MnO2cathode todesign hierarchical spheres of interlaced nanosheets for superior high-rateaqueous zinc ionbatteries[J].J Mater Chem A,2021,9,17211),醋酸锂的分解温度在300~350℃之间(黄玉代,低热固相法合成锂离子电池Li-Mn-O系正极材料及其性能表征[D]),因而不利于热化学氟化制备复合物过程中LiF的形成。
因此,提供一种安全性高,提高活性组分利用率,改善电化学性能的MnO-LiF/C复合物正极材料及其制备方法,具有重要的意义。
发明内容
本发明的目的在于为了克服现有技术的不足而提供一种MnO-LiF/C复合物及其制备方法和应用,通过聚四氟乙烯的热化学分解同时实现氟化物合成与碳原位包覆,使得复合物的电化学性能得到改善。
为了实现上述发明目的,本发明提供以下技术方案:
本发明提供了一种MnO-LiF/C复合物的制备方法,包含如下步骤:
1)将含锰化合物、含锂化合物、聚四氟乙烯混合,得到前驱体粉末;
2)将前驱体粉末顺次进行热处理、烧结反应,得到MnO-LiF/C复合物;
步骤1)所述含锰化合物为碳酸锰或四水合乙酸锰,含锂化合物为氢氧化锂或二水合乙酸锂,聚四氟乙烯为聚四氟乙烯粉末或聚四氟乙烯乳液。
作为优选,当步骤1)所述含锰化合物为碳酸锰,含锂化合物为氢氧化锂,聚四氟乙烯为聚四氟乙烯粉末时,含锰化合物、含锂化合物、聚四氟乙烯混合后进行球磨,得到前驱体粉末。
作为优选,步骤1)所述含锰化合物为四水合乙酸锰,含锂化合物为二水合乙酸锂时,含锰化合物和含锂化合物的混合溶液与聚四氟乙烯乳液混合后进行喷雾干燥,得到前驱体粉末;
或含锰化合物和含锂化合物的混合溶液进行喷雾干燥得到混合物粉末,混合物粉末与聚四氟乙烯粉末混合,得到前驱体粉末。
作为优选,步骤1)所述混合得到的混合物中还包含助剂和/或无水乙醇,助剂为科琴黑和/或石墨烯。
作为优选,碳酸锰、氢氧化锂和聚四氟乙烯粉末的质量比为3~4:0.65~0.75:0.7~0.8,碳酸锰和助剂的质量比为3~4:0.68~0.75。
作为优选,当不包含助剂时,四水合乙酸锰、二水合乙酸锂和聚四氟乙烯的质量比为3~3.5:2.5~3:0.9~2.5;当包含助剂时,四水合乙酸锰、二水合乙酸锂和聚四氟乙烯的质量比为3~3.5:2.5~3:0.6~1.72,四水合乙酸锰和助剂的质量比为3~3.5:0.35~0.45。
作为优选,步骤2)所述热处理的温度为330~370℃,热处理的时间为1.5~2.5h,热处理在保护气氛下进行。
作为优选,步骤2)所述烧结反应的温度为500~700℃,烧结反应的时间为0.5~2h。
本发明还提供了所述的制备方法制备得到的MnO-LiF/C复合物。
本发明还提供了所述的MnO-LiF/C复合物在锂离子电池正极材料中的应用。
本发明的有益效果包括:
1)本发明利用聚四氟乙烯分解形成的残留碳对MnO-LiF复合物进行碳原位包覆,以聚四氟乙烯为氟源和碳源,在烧结过程中原位生成的MnO纳米颗粒、LiF纳米颗粒、纳米碳颗粒三种组分均匀分布,有利于建立适合的表面转化反应进行的纳米活性微区,提高活性组分的利用率。聚四氟乙烯的分解温度(400~600℃)高于原料中乙酸锂或氢氧化锂的分解温度,从而有利于热化学氟化制备复合物过程中LiF的形成。
2)在烧结过程中通过聚四氟乙烯热解生成的中间体对含锂化合物和含锰化合物组成的前驱体进行氟化,不仅避免了使用具有腐蚀性、在一般情况下很难处理的氢氟酸或氟化氢气体,而且在烧结过程中通过聚四氟乙烯热解生成的残留碳对MnO-LiF复合物进行原位碳包覆,复合物中的残留碳不仅为MnO、LiF纳米粒子在表面转化反应过程中提供导电网络,确保电子的快速转移,还避免了MnO、LiF颗粒的团聚,明显改善材料颗粒大小和分布的均匀性,因而缩短了锂离子的扩散路径,提高了活性组分的利用率和电子导电性,改善了MnO-LiF/C复合物的电化学性能。
附图说明
图1为实施例1~7的MnO-LiF/C复合物样品的X射线衍射谱图;
图2为实施例3的MnO-LiF/C复合物样品的SEM图;
图3为实施例3的MnO-LiF/C复合物样品的首次充放电曲线图;
图4为实施例3的MnO-LiF/C复合物样品的循环性能曲线图;
图5为实施例5的MnO-LiF/C复合物样品的SEM图和EDS能谱面扫描图。
具体实施方式
本发明提供了一种MnO-LiF/C复合物的制备方法,包含如下步骤:
1)将含锰化合物、含锂化合物、聚四氟乙烯混合,得到前驱体粉末;
2)将前驱体粉末顺次进行热处理、烧结反应,得到MnO-LiF/C复合物;
步骤1)所述含锰化合物为碳酸锰或四水合乙酸锰,含锂化合物为氢氧化锂或二水合乙酸锂,聚四氟乙烯为聚四氟乙烯粉末或聚四氟乙烯乳液。
本发明中,当步骤1)所述含锰化合物为碳酸锰,含锂化合物为氢氧化锂,聚四氟乙烯为聚四氟乙烯粉末时,含锰化合物、含锂化合物、聚四氟乙烯混合后优选进行球磨,得到前驱体粉末。
本发明中,步骤1)所述含锰化合物为四水合乙酸锰,含锂化合物为二水合乙酸锂时,优选为含锰化合物和含锂化合物的混合溶液与聚四氟乙烯乳液混合后进行喷雾干燥,得到前驱体粉末,
或含锰化合物和含锂化合物的混合溶液进行喷雾干燥得到混合物粉末,混合物粉末与聚四氟乙烯粉末混合,得到前驱体粉末。
本发明中,聚四氟乙烯乳液的质量分数优选为55~65%,进一步优选为57~62%,更优选为59~60%。
本发明中,步骤1)所述混合得到的混合物中优选还包含助剂和/或无水乙醇,助剂优选为科琴黑和/或石墨烯。
本发明中,碳酸锰、氢氧化锂和聚四氟乙烯粉末的质量比优选为3~4:0.65~0.75:0.7~0.8,进一步优选为3.2~3.8:0.67~0.72:0.72~0.78,更优选为3.4485~3.6:0.69~0.7185:0.75~0.76;碳酸锰和助剂的质量比优选为3~4:0.68~0.75,进一步优选为3.2~3.8:0.7~0.73,更优选为3.4485~3.6:0.71~0.7266。
本发明中,当不包含助剂时,四水合乙酸锰、二水合乙酸锂和聚四氟乙烯的质量比优选为3~3.5:2.5~3:0.9~2.5,进一步优选为3.1~3.4:2.6~2.8:1.1~2.4,更优选为3.2687~3.3:2.65~2.7212:1.1132~2.2231;当包含助剂时,四水合乙酸锰、二水合乙酸锂和聚四氟乙烯的质量比优选为3~3.5:2.5~3:0.6~1.72,进一步优选为3.1~3.4:2.6~2.8:0.63~1.69,更优选为3.2687~3.3:2.65~2.7212:0.65~1.6673;四水合乙酸锰和助剂的质量比优选为3~3.5:0.35~0.45,进一步优选为3.1~3.4:0.37~0.42,更优选为3.2687~3.3:0.40~0.41。
本发明中,步骤2)所述热处理的温度优选为330~370℃,进一步优选为340~360℃,更优选为350℃;热处理的时间优选为1.5~2.5h,进一步优选为1.7~2.2h,更优选为2h;热处理优选在保护气氛下进行,保护气氛优选为氮气或氩气。
本发明中,步骤2)所述烧结反应的温度优选为500~700℃,进一步优选为550~650℃,更优选为600℃;烧结反应的时间优选为0.5~2h,进一步优选为1~1.5h;烧结反应优选在保护气氛下进行,保护气氛优选为氮气或氩气。
本发明还提供了所述的制备方法制备得到的MnO-LiF/C复合物。
本发明还提供了所述的MnO-LiF/C复合物在锂离子电池正极材料中的应用。
下面结合实施例对本发明提供的技术方案进行详细的说明,但是不能把它们理解为对本发明保护范围的限定。
实施例1
将3.2687g四水合乙酸锰与2.7212g二水合乙酸锂溶于300mL蒸馏水中配制成混合溶液,然后将2.2231g聚四氟乙烯乳液(质量分数为60%)以10mL/min的速率缓慢滴入混合溶液中,并用磁力搅拌器在200rpm的速率下持续搅拌30min,再将搅拌均匀后的分散液进行喷雾干燥(进风温度210℃,出风温度110℃,进样速率7mL/min),得到前驱体粉末。
将前驱体粉末在氮气气氛下350℃热处理2h,得到中间产物;中间产物在氮气气氛下600℃烧结2h,得到碳包覆的锂离子电池正极材料MnO-LiF/C复合物。
实施例2
将3.2687g四水合乙酸锰与2.7212g二水合乙酸锂溶于300mL蒸馏水中配制成混合溶液,然后将0.0819g石墨烯、0.3276g科琴黑、100mL无水乙醇和1.6673g聚四氟乙烯乳液(质量分数为60%)加入混合溶液中,并以300W的功率超声分散30min,再将分散均匀后的分散液进行喷雾干燥(进风温度210℃,出风温度110℃,进样速率7mL/min),得到前驱体粉末。
将前驱体粉末在氮气气氛下350℃热处理2h,得到中间产物;中间产物在氮气气氛下600℃烧结2h,得到碳包覆的锂离子电池正极材料MnO-LiF/C复合物。
实施例3
将7.3527g四水合乙酸锰与6.1206g二水合乙酸锂溶于500mL蒸馏水中配制成混合溶液,然后将0.9212g科琴黑、100mL无水乙醇加入混合溶液中,并以300W的功率超声分散30min,经喷雾干燥(进风温度210℃,出风温度110℃,进样速率7mL/min)得到混合物粉末,再将混合物粉末和1.5g聚四氟乙烯粉末混合均匀,得到前驱体粉末。
将前驱体粉末在氩气气氛下350℃热处理2h,得到中间产物;中间产物在氩气气氛下600℃烧结2h,得到碳包覆的锂离子电池正极材料MnO-LiF/C复合物。
实施例4
将3.4485g碳酸锰、0.7185g氢氧化锂、0.75g聚四氟乙烯粉末和0.7266g石墨烯混合,然后以无水乙醇为介质,在行星式球磨机中以600r/min的速率不间断球磨5h,球料比为5:1,得到混合均匀的前驱体粉末。
将前驱体粉末在惰性气氛下350℃热处理2h,得到中间产物;中间产物在氮气气氛下500℃烧结1h,得到碳包覆的锂离子电池正极材料MnO-LiF/C复合物。
实施例5
将3.2687g四水合乙酸锰与2.7212g二水合乙酸锂溶于300mL蒸馏水中配制成混合溶液,然后将2.2231g聚四氟乙烯乳液(质量分数为60%)以10mL/min的速率缓慢滴入混合溶液中,并用磁力搅拌器在200rpm的速率下持续搅拌30min,再将搅拌均匀后的分散液进行喷雾干燥(进风温度210℃,出风温度110℃,进样速率7mL/min),得到前驱体粉末。
将前驱体粉末在氮气气氛下350℃热处理2h,得到中间产物;中间产物在氮气气氛下600℃烧结1h,得到碳包覆的锂离子电池正极材料MnO-LiF/C复合物。
实施例6
将3.2687g四水合乙酸锰与2.7212g二水合乙酸锂溶于300mL蒸馏水中配制成混合溶液,然后将1.1132g聚四氟乙烯乳液(质量分数为60%)以10mL/min的速率缓慢滴入混合溶液中,并用磁力搅拌器在200rpm的速率下持续搅拌30min,再将搅拌均匀后的分散液进行喷雾干燥(进风温度210℃,出风温度110℃,进样速率7mL/min),得到前驱体粉末。
将前驱体粉末在氮气气氛下350℃热处理2h,得到中间产物;中间产物在氮气气氛下700℃烧结0.5h,得到碳包覆的锂离子电池正极材料MnO-LiF/C复合物。
实施例7
将3.2687g四水合乙酸锰与2.7212g二水合乙酸锂溶于300mL蒸馏水中配制成混合溶液,然后将2.2263g聚四氟乙烯乳液(质量分数为60%)以10mL/min的速率缓慢滴入混合溶液中,并用磁力搅拌器在200rpm的速率下持续搅拌30min,再将搅拌均匀后的分散液进行喷雾干燥(进风温度210℃,出风温度110℃,进样速率7mL/min),得到前驱体粉末。
将前驱体粉末在氩气气氛下350℃热处理2h,得到中间产物;中间产物在氩气气氛下600℃烧结1h,得到碳包覆的锂离子电池正极材料MnO-LiF/C复合物。
实施例1~7的MnO-LiF/C复合物样品的X射线衍射谱图采用Brucker D8Advance型X射线衍射仪测定,其XRD谱图如图1所示。由图1可知,实施例1~7的MnO-LiF/C复合物样品的X射线粉末衍射数据与MnO的JCPDS标准卡片(卡号:89-2804)以及LiF的JCPDS标准卡片(卡号:72-1538)符合得很好,谱图中不存在聚四氟乙烯、Li2CO3、Li2O、MnF2等杂质峰,说明样品纯度高。
实施例3的MnO-LiF/C复合物样品按照MnO-LiF/C复合物、乙炔黑、PVDF的质量比7:2:1制作成正极片,并组装成纽扣电池,在1.5~4.8V的电压区间以0.05C的倍率进行充放电性能测试。MnO-LiF/C复合物的首次充放电曲线如图3所示,循环性能曲线如图4所示。由图3、图4可知,在设定的充放电制度下,MnO-LiF/C复合物样品的首次放电比容量为160mAh/g,循环50周后的放电比容量保持在111mAh/g,容量保持率为69.4%。
实施例5的MnO-LiF/C复合物样品的SEM图和EDS能谱面扫描图如图5所示。由图5(a)可以看出,复合物样品颗粒形貌均匀,颗粒直径约为50nm,基本为类球形颗粒。图5(b~e)为实施例5样品的能谱面扫描图,分别对应C、F、Mn、O的元素分布。从图5可以看出,F、O、C和Mn四种元素在整个区域中都均匀分布,说明残留碳弥散地分布在复合物中,没有出现明显的颗粒聚集或相分离。
以上所述仅是本发明的优选实施方式,应当指出,对于本技术领域的普通技术人员来说,在不脱离本发明原理的前提下,还可以做出若干改进和润饰,这些改进和润饰也应视为本发明的保护范围。
Claims (10)
1.一种MnO-LiF/C复合物的制备方法,其特征在于,包含如下步骤:
1)将含锰化合物、含锂化合物、聚四氟乙烯混合,得到前驱体粉末;
2)将前驱体粉末顺次进行热处理、烧结反应,得到MnO-LiF/C复合物;
步骤1)所述含锰化合物为碳酸锰或四水合乙酸锰,含锂化合物为氢氧化锂或二水合乙酸锂,聚四氟乙烯为聚四氟乙烯粉末或聚四氟乙烯乳液。
2.根据权利要求1所述的制备方法,其特征在于,当步骤1)所述含锰化合物为碳酸锰,含锂化合物为氢氧化锂,聚四氟乙烯为聚四氟乙烯粉末时,含锰化合物、含锂化合物、聚四氟乙烯混合后进行球磨,得到前驱体粉末。
3.根据权利要求1所述的制备方法,其特征在于,步骤1)所述含锰化合物为四水合乙酸锰,含锂化合物为二水合乙酸锂时,含锰化合物和含锂化合物的混合溶液与聚四氟乙烯乳液混合后进行喷雾干燥,得到前驱体粉末;
或含锰化合物和含锂化合物的混合溶液进行喷雾干燥得到混合物粉末,混合物粉末与聚四氟乙烯粉末混合,得到前驱体粉末。
4.根据权利要求2或3所述的制备方法,其特征在于,步骤1)所述混合得到的混合物中还包含助剂和/或无水乙醇,助剂为科琴黑和/或石墨烯。
5.根据权利要求4所述的制备方法,其特征在于,碳酸锰、氢氧化锂和聚四氟乙烯粉末的质量比为3~4:0.65~0.75:0.7~0.8,碳酸锰和助剂的质量比为3~4:0.68~0.75。
6.根据权利要求4所述的制备方法,其特征在于,当不包含助剂时,四水合乙酸锰、二水合乙酸锂和聚四氟乙烯的质量比为3~3.5:2.5~3:0.9~2.5;当包含助剂时,四水合乙酸锰、二水合乙酸锂和聚四氟乙烯的质量比为3~3.5:2.5~3:0.6~1.72,四水合乙酸锰和助剂的质量比为3~3.5:0.35~0.45。
7.根据权利要求5或6所述的制备方法,其特征在于,步骤2)所述热处理的温度为330~370℃,热处理的时间为1.5~2.5h,热处理在保护气氛下进行。
8.根据权利要求7所述的制备方法,其特征在于,步骤2)所述烧结反应的温度为500~700℃,烧结反应的时间为0.5~2h。
9.权利要求1~8任一项所述的制备方法制备得到的MnO-LiF/C复合物。
10.权利要求9所述的MnO-LiF/C复合物在锂离子电池正极材料中的应用。
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