阅读说明：本技术 一种金属锂负极及其制备方法和锂电池 (Metallic lithium cathode, preparation method thereof and lithium battery ) 是由 李云明 周时国 曹瑞中 尹利超 裴卫兵 彭能岭 于 2018-07-09 设计创作，主要内容包括：本发明涉及一种金属锂负极及其制备方法和锂电池。该金属锂负极包括金属锂或金属锂合金形成的活性物质层,活性物质层的一侧表面上由内向外依次复合有混合电导材料层和固态电解质层,所述混合电导材料层含有混合电导材料,混合电导材料为天然石墨、人造石墨、软碳、硬碳、硅碳、硅、氧化亚硅、钛酸锂中的至少一种。该金属锂负极,位于内层的混合电导材料层通过提供金属锂沉积空间而缓解金属锂负极在电化学反应过程中的体积膨胀；位于外层的固态电解质层起到离子导体保护层的作用,与内层的混合导电材料层协同进一步抑制锂枝晶的生长,减少电化学极化,进而提高金属锂负极在电池中的电化学性能表现。(The invention relates to a metal lithium cathode, a preparation method thereof and a lithium battery. The metal lithium negative electrode comprises an active substance layer formed by metal lithium or metal lithium alloy, wherein a mixed conductive material layer and a solid electrolyte layer are compounded on the surface of one side of the active substance layer from inside to outside in sequence, the mixed conductive material layer contains a mixed conductive material, and the mixed conductive material is at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon oxide and lithium titanate. The mixed conducting material layer positioned in the inner layer relieves the volume expansion of the metallic lithium cathode in the electrochemical reaction process by providing a metallic lithium deposition space; the solid electrolyte layer positioned on the outer layer plays a role of an ion conductor protective layer, and the solid electrolyte layer and the mixed conductive material layer on the inner layer cooperate to further inhibit the growth of lithium dendrites, reduce electrochemical polarization and further improve the electrochemical performance of the metal lithium cathode in the battery.)

1. The metal lithium negative electrode comprises an active substance layer formed by metal lithium or metal lithium alloy, and is characterized in that a mixed conductive material layer and a solid electrolyte layer are compounded on the surface of one side of the active substance layer from inside to outside in sequence, the mixed conductive material layer contains a mixed conductive material, and the mixed conductive material is at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon oxide and lithium titanate.

2. The lithium metal anode of claim 1, wherein the layer of mixed conducting material is comprised of a mixed conducting material, a conductive agent, and a binder.

3. The lithium metal negative electrode according to claim 2, wherein the conductive agent is contained in an amount of 0.5 to 10% by mass, and the binder is contained in an amount of 0.5 to 10% by mass.

4. The lithium metal anode of claim 1, wherein the mixed conducting material layer further comprises a solid electrolyte, and the solid electrolyte is a polymer electrolyte, an inorganic solid electrolyte or a composite electrolyte of the polymer electrolyte and the inorganic solid electrolyte.

5. The lithium metal anode of claim 4, wherein the solid state electrolyte is an inorganic solid state electrolyte and the layer of mixed conducting material is comprised of a mixed conducting material, a conductive agent, an inorganic solid state electrolyte, and a binder.

6. The metallic lithium negative electrode of claim 4, wherein the solid state electrolyte is a polymer electrolyte or a composite electrolyte, and the layer of mixed conducting material is composed of a mixed conducting material, a conducting agent, and a polymer electrolyte or a composite electrolyte.

7. The lithium metal negative electrode according to claim 5 or 6, wherein the mixed electroconductive material layer contains the conductive agent in an amount of 0.5 to 10% by mass and the solid electrolyte in an amount of 0.5 to 20% by mass.

8. The lithium metal anode of claim 1, 2 or 4, wherein the thickness of the mixed conducting material layer is 0.01 to 10 μm, and the thickness of the solid electrolyte layer is 0.01 to 10 μm.

9. A method of making a lithium metal anode of claim 1, comprising the steps of:

1) coating the slurry containing the mixed conducting material on a metal lithium or lithium alloy substrate, and forming a mixed conducting material layer on the substrate after drying;

2) and coating the slurry containing the solid electrolyte on the mixed conducting material layer, and drying to form the solid electrolyte layer.

10. A lithium battery using the lithium metal negative electrode as claimed in claim 1.

Technical Field

The invention belongs to the field of secondary battery electrodes, and particularly relates to a metal lithium cathode, a preparation method thereof and a lithium battery.

Background

Batteries have been used as mobile power sources to promote the development of portable electronic devices and mobile tools, and play a decisive role in the development of new energy automobiles and the utilization of renewable energy sources. Lithium ion batteries are the first choice for portable electronic product batteries and power batteries because of their advantages of high energy density, high power density, long life, no memory effect, etc. With the progress of society, people put higher demands on the portability of electronic products and the endurance mileage of new energy automobiles, and lithium ion batteries with higher energy density are urgently needed to be developed.

Metallic lithium is considered as the final negative electrode of a lithium battery because it has the most negative potential and an extremely high specific capacity (3860mAh/g), but the volume expansion of the negative electrode and the growth of lithium dendrites during electrochemical reaction limit the commercial application of the metallic lithium negative electrode.

Disclosure of Invention

The invention aims to provide a lithium metal negative electrode, so as to solve the problem that the conventional lithium metal negative electrode has poor effect of inhibiting the growth of lithium dendrites. The invention also provides a preparation method of the metal lithium negative electrode and a lithium battery using the metal lithium negative electrode.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a metal lithium negative electrode comprises an active substance layer formed by metal lithium or metal lithium alloy, wherein a mixed conductive material layer and a solid electrolyte layer are compounded on the surface of one side of the active substance layer from inside to outside in sequence, the mixed conductive material layer contains a mixed conductive material, and the mixed conductive material is at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon oxide and lithium titanate.

The invention provides a lithium metal negative electrode, which is formed by compounding an active material layer, a mixed conducting material layer and a solid electrolyte layer to form a three-layer structure, wherein the mixed conducting material layer positioned on the inner layer relieves the volume expansion of the lithium metal negative electrode in the electrochemical reaction process by providing a lithium metal deposition space, and the layer can inhibit the formation and growth of lithium dendrites due to the provision of uniform lithium metal deposition sites; the solid electrolyte layer positioned on the outer layer plays a role of an ion conductor protective layer, and the solid electrolyte layer and the mixed conductive material layer on the inner layer cooperate to further inhibit the growth of lithium dendrites, reduce electrochemical polarization and further improve the electrochemical performance of the metal lithium cathode in the battery.

The mixed conducting material layer generally contains a conducting agent in addition to the mixed conducting material to form a more perfect conducting network. The conductive agent is at least one of carbon black, ketjen carbon, acetylene black, Super P, graphene, single-walled or multi-walled carbon nanotubes and graphene. In the case of no conductive agent, it is generally necessary to add a conductive substance to form a conductive network. From the viewpoint of reducing the cost and the manufacturing difficulty of the lithium metal negative electrode, preferably, the mixed conducting material layer is composed of a mixed conducting material, a conducting agent and a binder. More preferably, the mass content of the conductive agent is 0.5-10%, and the mass content of the binder is 0.5-10%. The binder can be selected from conventional binders for lithium ion batteries.

The mixed conducting material is a material with certain ionic conductivity and electronic conductivity. In order to further improve the ionic conductivity of the mixed conducting material layer, optimize the deposition space of metallic lithium and improve the lithium deposition performance, the mixed conducting material layer preferably further contains a solid electrolyte, wherein the solid electrolyte is a polymer electrolyte, an inorganic solid electrolyte or a composite electrolyte formed by the polymer electrolyte and the inorganic solid electrolyte. Two typical applications involving different types of solid electrolyte are listed below.

The solid electrolyte is inorganic solid electrolyte, and the mixed conducting material layer is composed of a mixed conducting material, a conducting agent, inorganic solid electrolyte and a binder. In this case, the conductive agent, the inorganic solid electrolyte, and the binder may be selected from conventional binders for lithium ion batteries, and serve to enhance the electronic and ionic conductivities of the mixed conductive material layer.

The solid electrolyte is a polymer electrolyte or a composite electrolyte, and the mixed conducting material layer is composed of a mixed conducting material, a conducting agent and the polymer electrolyte or the composite electrolyte. When the solid electrolyte contains the polymer electrolyte, the polymer electrolyte can be used as the ion conductive material and the binder at the same time, so that the use of the traditional binder can be reduced or avoided, and a more perfect mixed conductive network can be formed compared with the traditional binder.

In the above two application cases, the addition amount of the solid electrolyte can be determined according to the specific kind of the electrolyte and the selection of the mixed conducting material. Preferably, in the mixed conducting material layer, the mass content of the conducting agent is 0.5-20%, and the mass content of the solid electrolyte is 0.5-50%. More preferably, the mass content of the conductive agent and the solid electrolyte is 0.5 to 10% and 0.5 to 20%.

The polymer electrolyte comprises a polymer matrix and a lithium salt, wherein the polymer matrix and the lithium salt can be prepared by the conventional commercial channel or the prior art, and the polymer matrix and the lithium salt can be the common polymer matrix and lithium salt category, and the polymer matrix can be polyethylene oxide PEO, polypropylene oxide PPO, polypropylene carbonate PPC, polyethylene carbonate PEC, polyethylene carbonate PVCA, polyvinylidene fluoride-hexafluoropropylene PVDF-HFP, polyvinyl chloride PVC, polyimide PI, polyacrylonitrile PAN, polyvinyl acetate PVAc, polymethyl methacrylate PMMA, polyvinylidene fluoride PVDF, polypropylene imine PPI, polystyrene PS, polyethyl methacrylate PEMA, polyacrylic acid PAA, polymethacrylic acid PMAA, polyethylene oxide methyl ether methacrylate PEOMA, polyethylene glycol PEG, polydiacrylate PEDA, polyethylene glycol dimethacrylate PDE, polyethylene glycol dimethacrylate, etc, Polyethylene glycol methacrylate PME, polyethylene glycol monomethyl ether PEGMAt least one of polyethylene glycol methyl ether methacrylate PEGMA, poly-2-ethoxyethyl methacrylate PEOEMA, polyethylene glycol dimethyl ether PEGDME, poly-2-vinylpyridine P2VP and polyetherimide PEI. The lithium salt can be LiClO₄Lithium hexafluorophosphate LiPF₆Lithium bis (oxalato) borate LiBOB and lithium hexafluoroarsenate LiAsF₆Lithium tetrafluoroborate (LiBF)₄Lithium trifluoromethanesulfonate LiCF₃SO₃Lithium bis (trifluoromethylsulfonyl) imide LiTFSI and lithium bis (fluorosulfonyl) imide LiFSI.

The inorganic solid electrolyte can be prepared by adopting the conventional varieties or by utilizing the prior art. Preferably, the inorganic solid electrolyte is any one or more of a perovskite structure, a NASICON structure, a LISICON structure, a LiPON type, a garnet structure and an amorphous lithium ion conductive material.

From the viewpoint of suppressing the volume expansion of the metallic lithium negative electrode and the growth of lithium dendrites, it is preferable that the thickness of the mixed electrically conductive material layer is 0.01 to 10 μm and the thickness of the solid electrolyte layer is 0.01 to 10 μm. Further preferably, the thickness of the mixed conducting material layer is 0.01 to 5 μm, and the thickness of the solid electrolyte layer is 0.01 to 5 μm.

The preparation method of the metal lithium negative electrode comprises the following steps:

1) coating the slurry containing the mixed conducting material on a metal lithium or lithium alloy substrate, and forming a mixed conducting material layer on the substrate after drying;

2) and coating the slurry containing the solid electrolyte on the mixed conducting material layer, and drying to form the solid electrolyte layer.

The preparation method of the metal lithium cathode provided by the invention is simple in preparation process, easy for large-scale production and good in application prospect.

A lithium battery using the above metallic lithium negative electrode. The lithium battery may be a liquid lithium ion battery or a solid state battery. The positive electrode of the lithium battery is not particularly limited, and the positive electrodes of lithium cobaltate, ternary materials, lithium manganate, lithium iron phosphate, lithium-rich phase materials and the like can meet the use requirements.

When the lithium battery is prepared, the anode, the cathode and the diaphragm or the solid electrolyte membrane are assembled according to the prior art. In other cases, a solid electrolyte layer and a mixed conducting material layer may be sequentially formed on the surface of the separator or the negative electrode side of the solid electrolyte membrane, and then assembled with the positive electrode and the negative electrode to form a lithium battery. A lithium battery may also be produced by preparing a solid electrolyte layer on the negative electrode-side surface of a separator or a solid electrolyte membrane, and preparing a mixed electrically conductive material layer on metallic lithium or a lithium alloy.

According to the lithium battery provided by the invention, the existence of the metal lithium cathode can effectively relieve the volume expansion of the cathode, inhibit the formation and growth of lithium dendrites, effectively improve the circulating coulomb efficiency of the battery, improve the safety problem and prolong the circulating life.

Drawings

Fig. 1 is a schematic structural view of a lithium negative electrode of example 1 of the invention;

fig. 2 is a schematic structural diagram of a lithium battery according to embodiment 1 of the present invention.

Detailed Description

The following further describes embodiments of the present invention with reference to the drawings.