CN102386439B - A lithium ion secondary battery - Google Patents
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- CN102386439B CN102386439BCN201010274846.6ACN201010274846ACN102386439BCN 102386439 BCN102386439 BCN 102386439BCN 201010274846 ACN201010274846 ACN 201010274846ACN 102386439 BCN102386439 BCN 102386439B
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Abstract
Description
Translated fromChinese技术领域technical field
本发明属于电池技术领域，尤其涉及一种锂离子二次电池。The invention belongs to the technical field of batteries, in particular to a lithium ion secondary battery.
背景技术Background technique
目前，锂离子二次电池的负极多采用石墨类碳材料，但其理论比容量低。硅材料以其巨大的理论储锂容量而备受业界关注。锂与硅反应可得到不同的合金产物，如Li12Si17、Li13Si4、Li7Si3、Li22Si5等，其中Si嵌入锂时形成的合金Li4.4Si，其理论容量达4200mAh/g以上，在目前研究的各种合金中理论容量最高。At present, the negative electrodes of lithium-ion secondary batteries mostly use graphite-like carbon materials, but their theoretical specific capacity is low. Silicon materials have attracted the attention of the industry for their huge theoretical lithium storage capacity. Different alloy products can be obtained by the reaction of lithium and silicon, such as Li12 Si17 , Li13 Si4 , Li7 Si3 , Li22 Si5 , etc. Among them, the alloy Li4.4 Si formed when Si is embedded in lithium has a theoretical capacity of 4200mAh /g or more, the theoretical capacity is the highest among the various alloys currently being studied.
但是硅材料在充放电循环过程中，Li-Si合金的可逆生成与分解伴随着巨大的体积变化(达到400％)，会引起合金的机械分裂(产生裂缝与粉化)，导致材料结构的崩塌和电极材料的剥落而使电极材料失去电接触，从而造成电极的循环性能急剧下降，最后导致电极失效。However, during the charge-discharge cycle of silicon materials, the reversible formation and decomposition of Li-Si alloys is accompanied by a huge volume change (up to 400%), which will cause mechanical splitting of the alloy (creating cracks and pulverization), resulting in the collapse of the material structure. The electrode material loses electrical contact with the peeling off of the electrode material, resulting in a sharp decline in the cycle performance of the electrode, and finally leading to electrode failure.
目前，硅纳米线由于其一维结构，在嵌锂过程中其具有足够的体积膨胀空间，从而可以承受较大的膨胀应力而不粉化。另外，硅纳米线与集流体直接接触，保证了锂离子径向扩散的连续，从而提供了良好的电子通路和缩短锂离子扩散距离。硅纳米线还可以承受较大的应力和塑性形变，在材料韧性方面也有很大提高。但是，采用硅纳米线作为负极材料，电池的循环性能还是不够理想。At present, due to its one-dimensional structure, silicon nanowires have enough space for volume expansion during the lithium intercalation process, so that they can withstand large expansion stress without pulverization. In addition, the silicon nanowires are in direct contact with the current collector, which ensures the continuous radial diffusion of lithium ions, thereby providing a good electronic path and shortening the diffusion distance of lithium ions. Silicon nanowires can also withstand large stress and plastic deformation, and the material toughness has also been greatly improved. However, using silicon nanowires as the negative electrode material, the cycle performance of the battery is still not ideal.
发明内容Contents of the invention
本发明所要解决的技术问题是：现有技术中，采用硅纳米线作为负极的锂离子电池循环性能不良的问题；提供一种循环性能良好锂离子二次电池。The technical problem to be solved by the present invention is: in the prior art, the problem of poor cycle performance of lithium ion batteries using silicon nanowires as negative electrodes; providing a lithium ion secondary battery with good cycle performance.
一种锂离子二次电池，其包括电池壳、极芯和电解液，所述极芯和电解液密封容纳在电池壳内；A lithium ion secondary battery, which includes a battery case, a pole core and an electrolyte, the pole core and the electrolyte are hermetically accommodated in the battery case;
所述极芯包括正极、负极和位于正极与负极之间的隔膜，所述正极包括集流体和负载在集流体上的正极材料，所述负极包括集流体和负载在集流体上的负极材料；The pole core includes a positive electrode, a negative electrode and a separator between the positive electrode and the negative electrode, the positive electrode includes a current collector and a positive electrode material loaded on the current collector, and the negative electrode includes a current collector and a negative electrode material loaded on the current collector;
所述电解液包括锂盐、有机溶剂；Described electrolytic solution comprises lithium salt, organic solvent;
其中，所述负极材料包含碳材料和硅纳米线；所述锂盐中阴离子选自全氟烷基阴离子、螯合硼阴离子、有机铝酸基阴离子、螯合磷阴离子、全氟膦阴离子、亚胺基阴离子和硅基胺基阴离子中的一种或几种。Wherein, the negative electrode material includes carbon materials and silicon nanowires; the anions in the lithium salt are selected from perfluoroalkyl anions, chelated boron anions, organoaluminate anions, chelated phosphorus anions, perfluorophosphine anions, One or more of amino anions and silicon amino anions.
本发明所提供的锂离子二次电池，相比现有的硅纳米线电池，其电池循环性能有了大幅的提高，从而大大延长了电池的使用寿命。Compared with the existing silicon nanowire battery, the lithium-ion secondary battery provided by the invention has greatly improved battery cycle performance, thereby greatly prolonging the service life of the battery.
附图说明Description of drawings
图1是本发明一实施例负极材料的SEM图(2μm)。FIG. 1 is a SEM image (2 μm) of an anode material of an embodiment of the present invention.
图2是本发明一实施例负极材料的SEM图(5μm)。Fig. 2 is a SEM image (5 μm) of the negative electrode material of an embodiment of the present invention.
具体实施方式Detailed ways
为了使本发明所解决的技术问题、技术方案及有益效果更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.
一种锂离子二次电池，其包括电池壳、极芯和电解液，所述极芯和电解液密封容纳在电池壳内；A lithium ion secondary battery, which includes a battery case, a pole core and an electrolyte, the pole core and the electrolyte are hermetically accommodated in the battery case;
所述极芯包括正极、负极和位于正极与负极之间的隔膜，所述正极包括集流体和负载在集流体上的正极材料，所述负极包括集流体和负载在集流体上的负极材料；The pole core includes a positive electrode, a negative electrode and a separator between the positive electrode and the negative electrode, the positive electrode includes a current collector and a positive electrode material loaded on the current collector, and the negative electrode includes a current collector and a negative electrode material loaded on the current collector;
所述电解液包括锂盐、有机溶剂；Described electrolytic solution comprises lithium salt, organic solvent;
其中，所述负极材料包含碳材料和硅纳米线；所述锂盐中阴离子选自全氟烷基阴离子、螯合硼阴离子、有机铝酸基阴离子、螯合磷阴离子、全氟膦阴离子、亚胺基阴离子和硅基胺基阴离子中的一种或几种。Wherein, the negative electrode material includes carbon materials and silicon nanowires; the anions in the lithium salt are selected from perfluoroalkyl anions, chelated boron anions, organoaluminate anions, chelated phosphorus anions, perfluorophosphine anions, One or more of amino anions and silicon amino anions.
在本发明的锂离子二次电池中，对正极没有特殊要求，正极可以是锂离子二次电池中常见的正极。In the lithium ion secondary battery of the present invention, there is no special requirement for the positive electrode, and the positive electrode may be a common positive electrode in lithium ion secondary batteries.
在本发明中，正极中的集流体为本领域技术人员所公知的，在此不作赘述。In the present invention, the current collector in the positive electrode is well known to those skilled in the art and will not be described in detail here.
正极材料亦为本领域技术人员所公知的，一般包括钴镍锰系列、磷酸盐系列、钛系列、钒系列等。常见的正极材料有：锂钴氧LiCoO2、锂镍氧LiNiO2、锂锰氧LiMnO2、锂镍钴氧、锂镍钴锰氧、LiFePO4、Li3V2(PO4)3、LiMnPO4、Li2FeSiO4、Li2MnSiO4、LiVO2、Li2V2O4、LiV3O8以及上述物质包覆或者掺杂的产物。Cathode materials are also well known to those skilled in the art, and generally include cobalt-nickel-manganese series, phosphate series, titanium series, vanadium series, and the like. Common cathode materials are: lithium cobalt oxide LiCoO2 , lithium nickel oxide LiNiO2 , lithium manganese oxide LiMnO2 , lithium nickel cobalt oxide, lithium nickel cobalt manganese oxide, LiFePO4 , Li3 V2 (PO4 )3 , LiMnPO4 , Li2 FeSiO4 , Li2 MnSiO4 , LiVO2 , Li2 V2 O4 , LiV3 O8 and products coated or doped with the above substances.
本发明优选包括LiCoO2、LiMnO2、LiNiO2、Li(Ni0.8Co0.2)O2、LiNi1/3Co1/3Mn1/3O2、LiFePO4、Li3V2(PO4)3、LiV3O8中一种或几种。The present invention preferably includes LiCoO2 , LiMnO2 , LiNiO2 , Li(Ni0.8 Co0.2 )O2 , LiNi1/3 Co1/3 Mn1/3 O2 , LiFePO4 , Li3 V2 (PO4 )3 , LiV3 O8 or one or more.
正极中粘结剂以及导电剂均为本领域技术人员所公知的，在此不作赘述。The binder and the conductive agent in the positive electrode are well known to those skilled in the art, and will not be repeated here.
正极的制备方法是将正极材料、导电剂以及粘结剂按一定比例在溶剂中搅拌混合均匀得到所需正极浆料，然后将该浆料涂敷在集流体上，经过干燥、压片处理即得正极。The preparation method of the positive electrode is to stir and mix the positive electrode material, the conductive agent and the binder in a solvent in a certain proportion to obtain the required positive electrode slurry, and then apply the slurry on the current collector, and then dry and tablet it. Positive.
本发明用于正极材料溶剂可以选自本领域内常规使用的溶剂，如可以选自N-甲基吡咯烷酮(NMP)、N，N-二甲基甲酰胺(DMF)、N，N-二乙基甲酰胺(DEF)、二甲亚砜(DMSO)、四氢呋喃(THF)以及水和醇类中的一种或几种。溶剂的用量使所述浆料能够涂覆到所述集流体上即可。一般来说，溶剂的用量为使浆液中正极材料的浓度为40～90wt％，优选为50～85wt％。The present invention is used for positive electrode material solvent and can be selected from the solvent that routinely uses in this area, as can be selected from N-methylpyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-diethyl One or more of methyl sulfoxide (DMSO), tetrahydrofuran (THF), water and alcohols. The amount of the solvent is such that the slurry can be coated on the current collector. Generally, the amount of the solvent is such that the concentration of the positive electrode material in the slurry is 40-90 wt%, preferably 50-85 wt%.
在本发明的锂离子二次电池中，负极包括集流体和负载在集流体上的负极材料。该负极材料包含碳材料和硅纳米线，碳材料呈颗粒状，硅纳米线分布在所述碳材料上；In the lithium ion secondary battery of the present invention, the negative electrode includes a current collector and a negative electrode material supported on the current collector. The negative electrode material includes carbon material and silicon nanowires, the carbon material is in the form of particles, and the silicon nanowires are distributed on the carbon material;
其中，硅纳米线为本领域技术人员所公知的物质。其为一维结构，可以通过商购获得，也可以自己制备。Among them, silicon nanowires are known to those skilled in the art. It is a one-dimensional structure, which can be obtained commercially or prepared by oneself.
本发明的硅纳米线可以是全部晶体结构的硅纳米线，还可以是全部为无定形硅的硅纳米线，更可以是表面为无定形硅，内部为晶体结构的核壳结构的硅纳米线。The silicon nanowires of the present invention can be silicon nanowires with all crystalline structures, can also be silicon nanowires that are all amorphous silicon, or can be silicon nanowires with amorphous silicon on the surface and a core-shell structure with a crystalline structure inside. .
优选情况下，本发明的硅纳米线的平均直径为10～120nm，长度为1～20μm。更优选为平均直径为20～80nm，长度为2～10μm。Preferably, the silicon nanowires of the present invention have an average diameter of 10-120 nm and a length of 1-20 μm. More preferably, the average diameter is 20 to 80 nm, and the length is 2 to 10 μm.
其中，碳材料亦为本领域技术人员所公知的物质。Among them, carbon materials are also known to those skilled in the art.
本发明的碳材料优选选自石墨、硬碳、软碳以及石墨化中间相碳微珠MCMB中一种或几种；更优选为石墨。The carbon material of the present invention is preferably selected from one or more of graphite, hard carbon, soft carbon and graphitized mesocarbon microbeads MCMB; more preferably graphite.
本发明优选碳材料呈颗粒状，硅纳米线包覆在碳材料上。In the present invention, the carbon material is preferably in the form of particles, and the silicon nanowires are coated on the carbon material.
碳材料的微观形貌可以是球形、类球形或片层状结构。The microscopic morphology of carbon materials can be spherical, spherical or lamellar structures.
优选情况下，本发明的碳材料的中值粒径D50为2～20μm，更优选为5～15μm。Preferably, the median particle diameter D50 of the carbon material of the present invention is 2-20 μm, more preferably 5-15 μm.
本发明中硅纳米线和碳材料的质量比为1∶99～50∶50，更优选为2∶98～20∶80。这样可以使电池的容量和循环性能均处于较高的水平。In the present invention, the mass ratio of silicon nanowires to carbon materials is 1:99˜50:50, more preferably 2:98˜20:80. In this way, the capacity and cycle performance of the battery can be at a high level.
负极中还包括负极粘结剂，负极粘结剂为本领域技术人员所公知负极粘结剂。本发明的负极粘结剂可以选自聚噻吩、聚吡咯、聚四氟乙烯、聚偏氟乙烯、聚乙烯、聚丙烯、聚丙烯酰胺、乙烯-丙烯-二烯共聚树脂、苯乙烯丁二烯橡胶、聚丁二烯、氟橡胶、聚环氧乙烯、聚乙烯吡咯烷酮、聚酯树脂、丙烯酸树脂、酚醛树脂、环氧树脂、聚乙烯醇、羧丙基纤维素和乙基纤维素中的一种或几种。The negative electrode also includes a negative electrode binder, and the negative electrode binder is known to those skilled in the art. The negative electrode binder of the present invention can be selected from polythiophene, polypyrrole, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylamide, ethylene-propylene-diene copolymer resin, styrene butadiene One of rubber, polybutadiene, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, carboxypropyl cellulose and ethyl cellulose species or several.
本发明负极还可以选择性地含有现有技术负极中通常所含有的导电剂。由于导电剂用于增加电极的导电性，降低电池的内阻，因此本发明优选含有导电剂。所述导电剂的含量和种类为本领域技术人员所公知，例如，以负极材料为基准，导电剂的含量一般为0.1～12wt％。所述导电剂可以选自导电碳黑、碳纳米管、镍粉、铜粉中的一种或几种。The negative electrode of the present invention may optionally contain conductive agents generally contained in negative electrodes of the prior art. Since the conductive agent is used to increase the conductivity of the electrode and reduce the internal resistance of the battery, the present invention preferably contains a conductive agent. The content and type of the conductive agent are well known to those skilled in the art. For example, based on the negative electrode material, the content of the conductive agent is generally 0.1-12 wt%. The conductive agent may be selected from one or more of conductive carbon black, carbon nanotubes, nickel powder, and copper powder.
根据所用粘结剂种类的不同，以负极材料的重量为基准，负极粘结剂的含量为0.01～10wt％，优选为0.02～5wt％；导电剂的含量为0～12wt％，优选为2～10wt％。Depending on the type of binder used, based on the weight of the negative electrode material, the content of the negative electrode binder is 0.01 to 10 wt%, preferably 0.02 to 5 wt%, and the content of the conductive agent is 0 to 12 wt%, preferably 2 to 5 wt%. 10 wt%.
负极的制备工艺是将负极材料、粘结剂按一定比例在溶剂中搅拌混合均匀得到所需负极浆料，然后将该浆料涂敷在集流体上，经过干燥、压片处理即得负极。常采用的溶剂为N-甲基吡咯烷酮(NMP)、水、乙醇、丙酮等，以负极材料为基准，溶剂的用量为50-400％。The preparation process of the negative electrode is to stir and mix the negative electrode material and the binder in a solvent in a certain proportion to obtain the required negative electrode slurry, and then apply the slurry on the current collector, and then dry and tablet to obtain the negative electrode. Commonly used solvents are N-methylpyrrolidone (NMP), water, ethanol, acetone, etc., based on the negative electrode material, the amount of solvent used is 50-400%.
在本发明的锂离子二次电池中，隔膜设置于正极和负极之间，具有电绝缘性能和液体保持性能。所述隔膜可以选自本领域技术人员公知的锂离子二次电池中所用的各种隔膜，例如聚烯烃微多孔膜(PP)、聚乙烯毡(PE)、玻璃纤维毡或超细玻璃纤维纸或PP/PE/PP。所述隔膜也可以是聚酰亚胺薄膜。所述聚酰亚胺薄膜可以为本领域技术人员所公知的聚酰亚胺薄膜，优选其孔隙率为20％～55％，平均孔直径为30～120nm。In the lithium ion secondary battery of the present invention, the separator is arranged between the positive electrode and the negative electrode, and has electrical insulation performance and liquid retention performance. The separator can be selected from various separators used in lithium ion secondary batteries known to those skilled in the art, such as polyolefin microporous membrane (PP), polyethylene felt (PE), glass fiber felt or ultrafine glass fiber paper Or PP/PE/PP. The diaphragm may also be a polyimide film. The polyimide film may be a polyimide film known to those skilled in the art, preferably with a porosity of 20%-55% and an average pore diameter of 30-120nm.
在本发明的锂离子二次电池中，电解液中含有锂盐、有机溶剂。In the lithium ion secondary battery of the present invention, the electrolyte solution contains a lithium salt and an organic solvent.
其中，电解液中锂盐的阴离子选自一下阴离子中一种或几种：Wherein, the anion of the lithium salt in the electrolyte is selected from one or more of the following anions:
烷基磺酸阴离子、全氟烷基阴离子、螯合硼阴离子、有机铝酸基阴离子、螯合磷阴离子、全氟膦阴离子、亚胺基阴离子和硅基胺基阴离子。Alkylsulfonate anions, perfluoroalkyl anions, chelating boron anions, organoaluminate-based anions, chelating phosphorus anions, perfluorophosphine anions, imino anions, and silylamide anions.
优选情况下，本发明的锂盐选自LiB(C2O4)2、Li2Al(CSO3Cl4)、LiP(C6H4O2)3、LiPF3(C2F5)3和LiN(SiC3H9)2中一种或几种。Preferably, the lithium salt of the present invention is selected from LiB(C2 O4 )2 , Li2 Al(CSO3 Cl4 ), LiP(C6 H4 O2 )3 , LiPF3 (C2 F5 )3 and one or more of LiN(SiC3 H9 )2 .
本发明优选锂盐的浓度为为0.3～3mol/L，更优选为0.5～1.5mol/L。In the present invention, the concentration of the lithium salt is preferably 0.3-3 mol/L, more preferably 0.5-1.5 mol/L.
本发明电解液中的有机溶剂可以采用本领域常用的溶剂，例如EC(乙烯碳酸酯)、PC(丙烯碳酸酯)、FEC(氟代碳酸乙烯酯)、DEC(碳酸二乙酯)、DMC(二甲基碳酸酯)、EMC(乙基甲基碳酸酯)、DME(二甲氧基乙烷)、GBL(γ-丁内酯)、DMC(碳酸二甲酯)、MF(甲酸甲酯)、MA(丙烯酸甲酯)、MB(丁酸甲酯)、EP(乙酸乙酯)、ES(亚硫酸乙烯酯)、PS(亚硫酸丙烯酯)、DMS(甲硫醚)、DES(二乙基亚硫酸酯)等。The organic solvent in the electrolytic solution of the present invention can adopt solvent commonly used in this area, such as EC (ethylene carbonate), PC (propylene carbonate), FEC (fluoroethylene carbonate), DEC (diethyl carbonate), DMC ( Dimethyl carbonate), EMC (ethyl methyl carbonate), DME (dimethoxyethane), GBL (γ-butyrolactone), DMC (dimethyl carbonate), MF (methyl formate) , MA (methyl acrylate), MB (methyl butyrate), EP (ethyl acetate), ES (ethylene sulfite), PS (propylene sulfite), DMS (methyl sulfide), DES (diethyl sulfite) base sulfite), etc.
本发明优选乙烯碳酸酯、丙烯碳酸酯、氟代碳酸乙烯酯、碳酸二乙酯、二甲基碳酸酯、乙基甲基碳酸酯中的一种或几种。The present invention is preferably one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.
本发明的电解液中还优选含有添加剂，添加剂可以选用本领域技术人员所公知的添加剂。The electrolyte solution of the present invention preferably also contains additives, and the additives can be selected from additives known to those skilled in the art.
本发明锂离子二次电池的制备方法，按照本领域的技术人员所公知的方法进行。一般来说，该方法包括将正极、负极和位于正极与负极之间的隔膜依次卷绕或者层叠形成极芯，将极芯置入电池壳中，加入电解液，然后密封，其中，卷绕和密封的方法为本领域人员所公知。电解液的用量为常规用量。The preparation method of the lithium ion secondary battery of the present invention is carried out according to methods known to those skilled in the art. Generally speaking, the method includes winding or laminating the positive electrode, the negative electrode, and the separator between the positive electrode and the negative electrode in sequence to form a pole core, putting the pole core into the battery case, adding electrolyte, and then sealing, wherein, winding and Methods of sealing are known to those skilled in the art. The amount of electrolyte used is conventional.
本发明的发明人经过大量的实验研究以及分析发现，造成现有技术中硅纳米线电池循环性能不良的原因主要是：硅纳米线的表面不可避免的存在着一定的硅的氧化物，硅的氧化物会改变硅纳米线的表面态性质以及表面电荷，从而保证了硅纳米线可以稳定存在于空气中。但是，该硅的氧化物会与现有技术中的电解液中锂盐的阴离子发生反应，从而使锂盐分解。以最常用的LiPF6为例，LiPF6在电池中存在如下平衡：The inventors of the present invention have found through a large number of experimental studies and analysis that the reason for the poor cycle performance of the silicon nanowire battery in the prior art is that there is inevitably a certain amount of silicon oxide on the surface of the silicon nanowire. The oxide will change the surface state properties and surface charges of the silicon nanowires, thus ensuring that the silicon nanowires can exist stably in the air. However, the silicon oxide reacts with the anion of the lithium salt in the conventional electrolytic solution, thereby decomposing the lithium salt. Taking the most commonly used LiPF6 as an example, LiPF6 has the following balance in the battery:
LiPF6＝LiF+PF5，LiPF6 =LiF+PF5 ,
而2PF5+SiO2＝SiF4↑+2PF3OAnd 2PF5 +SiO2 ＝SiF4 ↑+2PF3 O
从而导致LiPF6以及其他类似的无机锂盐的持续分解反应，从影响电解液的性能。同时，化成时由于上述反应的持续进行，不利于在硅纳米线的表面形成SEI膜。从而严重影响硅纳米线电池的循环性能。其次，影响硅纳米线电池循环性能的因素还有：硅纳米线本身的电子电导率低，并且硅纳米线在充放电过程中易结块，会加剧电子电导率降低。As a result, the continuous decomposition reaction of LiPF6 and other similar inorganic lithium salts affects the performance of the electrolyte. At the same time, due to the continuous progress of the above reaction during the chemical formation, it is not conducive to the formation of an SEI film on the surface of the silicon nanowire. Thus seriously affecting the cycle performance of silicon nanowire batteries. Secondly, there are other factors affecting the cycle performance of silicon nanowire batteries: the electronic conductivity of silicon nanowires is low, and silicon nanowires are easy to agglomerate during charging and discharging, which will aggravate the decrease in electronic conductivity.
本发明的发明人意外发现：将硅纳米线材料分散到碳材料中，电解液中采用本发明的锂盐，电池的循环性能有了大幅的提高。The inventors of the present invention unexpectedly found that the cycle performance of the battery is greatly improved by dispersing the silicon nanowire material into the carbon material and using the lithium salt of the present invention in the electrolyte.
本发明的发明人推定的原因是：本发明中锂盐的有机阴离子相对于硅纳米线而言，具有较好的化学稳定性；从而能够有效的抑制硅纳米线与电解液之间的边界反应，并且有利于在硅纳米线上形成稳定的界面膜SEI膜。同时，有机阴离子具有较大的离子半径，可以将阴离子的电荷进行离域化，从而降低晶格能，减少离子之间的相互作用，保证了溶解性和电导率。本发明的硅纳米线分布在碳材料上，一方面可以有效抑制充放电时硅纳米线的结块现象；另一方面，碳材料是良好电子导体，可以弥补硅纳米线的电子电导率的问题。从而使负极材料的导电性有了大幅的提高。最终导致电池循环性能的提高。The inventors of the present invention infer that the reason is that the organic anion of the lithium salt in the present invention has better chemical stability compared to the silicon nanowire; thus the boundary reaction between the silicon nanowire and the electrolyte can be effectively suppressed , and is conducive to the formation of a stable interface film SEI film on silicon nanowires. At the same time, the organic anion has a large ionic radius, which can delocalize the charge of the anion, thereby reducing the lattice energy, reducing the interaction between ions, and ensuring the solubility and conductivity. The silicon nanowires of the present invention are distributed on the carbon material, which can effectively suppress the agglomeration of the silicon nanowires during charge and discharge on the one hand; on the other hand, the carbon material is a good electronic conductor, which can make up for the electronic conductivity of the silicon nanowires. . As a result, the conductivity of the negative electrode material has been greatly improved. Ultimately leading to improved battery cycle performance.
以下结合具体实施例对本发明作进一步的阐述。The present invention will be further elaborated below in conjunction with specific examples.
实施例1Example 1
(1)正极的制作：(1) Production of positive electrode:
将940gLiCoO2、30g PVDF、30g导电剂乙炔黑加入到600g溶剂NMP中，然后在真空搅拌机中搅拌，形成稳定均一的正极浆料。将该浆料均匀地间歇涂布在铝箔(铝箔尺寸为：宽度160mm，厚度16μm)的两面上，然后120℃烘干，经过辊压机压片后，剪裁为尺寸为480mm*45mm的极片即得正极极片。Add 940g LiCoO2 , 30g PVDF, and 30g conductive agent acetylene black into 600g solvent NMP, and then stir in a vacuum mixer to form a stable and uniform positive electrode slurry. Spread the slurry evenly and intermittently on both sides of the aluminum foil (aluminum foil size: width 160mm, thickness 16μm), then dry at 120°C, and cut it into pole pieces with a size of 480mm*45mm after being pressed by a roller press That is, the positive electrode sheet is obtained.
(2)负极的制作：(2) Production of negative electrode:
先将1000g去离子水加入到60g硅纳米线中，超声波分散60min至絮状团聚体消失，然后边搅拌边加入940g石墨(日本NCK，D50＝15μm)，待石墨全部加入后，添加粘结剂CMC溶液(其中CMC含量为60g)；同时搅拌和超声波分散120min，补加一定量的溶剂调节浆料粘度至2000～3000cp，即得电极浆料。将该浆料均匀地间歇涂布在铜箔(铝箔尺寸为：宽度160mm，厚度16μm)的两面上，然后120℃烘干，经过辊压机压片后，剪裁为尺寸为480mm*45mm的极片即得负极极片。First add 1000g of deionized water to 60g of silicon nanowires, ultrasonically disperse for 60min until the flocculent aggregates disappear, then add 940g of graphite (NCK Japan, D50 = 15μm) while stirring, after all the graphite is added, add the bonding agent Add a CMC solution (the CMC content is 60g); stir and ultrasonically disperse for 120min at the same time, add a certain amount of solvent to adjust the viscosity of the slurry to 2000-3000cp, and obtain the electrode slurry. The slurry is uniformly and intermittently coated on both sides of copper foil (aluminum foil size: width 160mm, thickness 16μm), then dried at 120°C, and after being pressed by a roller press, it is cut into poles with a size of 480mm*45mm. The sheet is the negative electrode sheet.
(3)电解液的配制(3) Preparation of electrolyte
将EC∶DEC以体积比为4∶6比例的混合作为溶剂，然后将电解质锂盐LiN(SiC3H9)2溶解在溶剂中，添加一定量的添加剂，制备电解液。其中，电解液中锂盐的浓度为1mol/L。EC:DEC is mixed at a volume ratio of 4:6 as a solvent, then electrolyte lithium salt LiN(SiC3 H9 )2 is dissolved in the solvent, and a certain amount of additives are added to prepare an electrolyte solution. Wherein, the concentration of the lithium salt in the electrolyte is 1 mol/L.
(4)电池的制作(4) Production of batteries
在上述制备的正极片、负极片之间设置PP/PE/PP隔膜后经卷绕、套壳，注入上述电解液，封口、化成等制得电池，记作A1。A PP/PE/PP separator was placed between the positive electrode sheet and the negative electrode sheet prepared above, and then the battery was obtained by winding, casing, injection of the above electrolyte, sealing, and chemical formation, which was designated as A1.
实施例2Example 2
与实施例1所不同的是：电解质锂盐为LiPF3(C2F5)3，电解液中的锂盐浓度为1.5mol/L，其他部分同实施例1。制成的电池，记作A2。The difference from Example 1 is that the electrolyte lithium salt is LiPF3 (C2 F5 )3 , the lithium salt concentration in the electrolyte is 1.5 mol/L, and other parts are the same as in Example 1. The finished battery is denoted as A2.
实施例3Example 3
与实施例1所不同的是：电解质锂盐为LiBC2O4F2，电解液中的锂盐浓度为0.5mol/L，其他部分同实施例1。制成的电池，记作A3。The difference from Example 1 is that the electrolyte lithium salt is LiBC2 O4 F2 , the lithium salt concentration in the electrolyte is 0.5 mol/L, and other parts are the same as in Example 1. The finished battery is denoted as A3.
实施例4Example 4
与实施例1所不同的是：电解质锂盐为LiB(C2O4)2，电解液中的锂盐浓度为0.8mol/L，他部分同实施例1。制成的电池，记作A4。The difference from Example 1 is that the electrolyte lithium salt is LiB(C2 O4 )2 , and the lithium salt concentration in the electrolyte solution is 0.8 mol/L. Other parts are the same as in Example 1. The manufactured battery is denoted as A4.
实施例5Example 5
与实施例1所不同的是：电解质锂盐为LiN(SiC3H9)2和LiB(C2O4)2，电解液中LiN(SiC3H9)2的浓度为0.6mol/L，LiB(C2O4)2为0.4mol/L。其他部分同实施例1。制成的电池，记作A5。The difference from Example 1 is that the electrolyte lithium salts are LiN(SiC3 H9 )2 and LiB(C2 O4 )2 , the concentration of LiN(SiC3 H9 )2 in the electrolyte is 0.6mol/L, LiB(C2 O4 )2 is 0.4 mol/L. Other parts are with embodiment 1. The battery made is denoted as A5.
实施例6Example 6
与实施例5所不同的是：负极材料中的硅纳米线的量为100g，石墨为900g。其他部分同实施例1。制成的电池，记作A6。The difference from Example 5 is that the amount of silicon nanowires in the negative electrode material is 100 g, and that of graphite is 900 g. Other parts are with embodiment 1. The manufactured battery is denoted as A6.
实施例7Example 7
与实施例5所不同的是：负极材料中的硅纳米线的量为150g，石墨为850g。其他部分同实施例1。制成的电池，记作A7。The difference from Example 5 is that the amount of silicon nanowires in the negative electrode material is 150 g, and that of graphite is 850 g. Other parts are with embodiment 1. The battery made is denoted as A7.
实施例8Example 8
与实施例5所不同的是：负极材料中的硅纳米线的量为40g，石墨为960g。其他部分同实施例1。制成的电池，记作A8。The difference from Example 5 is: the amount of silicon nanowires in the negative electrode material is 40g, and that of graphite is 960g. Other parts are with embodiment 1. The battery made is denoted as A8.
对比例1Comparative example 1
与实施例1所不同的是：The difference with embodiment 1 is:
步骤(2)负极的制作：先将1000g溶剂去离子水加入到200g硅纳米线材料中，超声波分散60min至絮状团聚体消失，添加CMC(粘结剂)溶液，其中CMC的量为20g；搅拌和超声波分散同时进行120min，补加一定量的溶剂调节浆料粘度至2000～3000cp，即得电极浆料。将该浆料均匀地间歇涂布在铜箔(铝箔尺寸为：宽度160mm，厚度16μm)的两面上，然后120℃烘干，经过辊压机压片后，剪裁为尺寸为480mm*45mm的极片即得负极极片。Step (2) Preparation of the negative electrode: first add 1000g of solvent deionized water to 200g of silicon nanowire material, ultrasonically disperse for 60min until the flocculent aggregates disappear, and add CMC (binder) solution, wherein the amount of CMC is 20g; Stirring and ultrasonic dispersion are carried out simultaneously for 120 minutes, and a certain amount of solvent is added to adjust the viscosity of the slurry to 2000-3000 cp to obtain the electrode slurry. The slurry is uniformly and intermittently coated on both sides of copper foil (aluminum foil size: width 160mm, thickness 16μm), then dried at 120°C, and after being pressed by a roller press, it is cut into poles with a size of 480mm*45mm. The sheet is the negative electrode sheet.
其他部分同实施例1。制成的电池，记作AC1。Other parts are with embodiment 1. The battery made is denoted as AC1.
对比例2Comparative example 2
与实施例1所不同的是：用LiPF6替换LiN(SiC3H9)2，锂盐浓度不变。其他部分同实施例1。制成的电池，记作AC2。The difference from Example 1 is that LiN(SiC3 H9 )2 is replaced by LiPF6 , and the lithium salt concentration remains unchanged. Other parts are with embodiment 1. The battery made is denoted as AC2.
性能检测：Performance testing:
将A1-A8以及AC1-AC2的电池各取50支化成、分容，在擎天BS-9300二次电池性能检测装置上，23±2℃条件下，将电池以0.2C进行充放电循环测试。步骤如下：搁置10min；恒压充电至4.2V/0.05C截止；搁置10min；恒流放电至3.0V；循环上述步骤。取其平均值作填入表1内。Take 50 batteries of A1-A8 and AC1-AC2 and divide them into capacity, and conduct a charge-discharge cycle test at 0.2C on DynaSky BS-9300 secondary battery performance testing device at 23±2°C . The steps are as follows: put on hold for 10 minutes; charge at constant voltage to 4.2V/0.05C cut-off; hold for 10 minutes; discharge at constant current to 3.0V; repeat the above steps. Take the average value and fill it in Table 1.
表1Table 1
从表1可以看出，A1-A8电池的保持率为80％时的循环次数相比AC1-AC2有了大幅的提高。还有300次循环之后的容量保持率，也有了大幅的提高。这说明本发明的电池循环性能，相比硅纳米线电池有了大幅的提高。It can be seen from Table 1 that the number of cycles when the retention rate of A1-A8 batteries is 80% has been greatly increased compared with AC1-AC2. The capacity retention rate after 300 cycles has also been greatly improved. This shows that the cycle performance of the battery of the present invention has been greatly improved compared with the silicon nanowire battery.
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.
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