阅读说明：本技术 一种掺氮的复合平面金属锂阳极、制备及其在锂金属电池中的应用 (Nitrogen-doped composite planar metal lithium anode, preparation and application thereof in lithium metal battery ) 是由 赖延清 洪波 范海林 向前 张治安 张凯 于 2018-08-29 设计创作，主要内容包括：本发明公开了一种掺氮的复合平面金属锂阳极的制备与应用。所述的掺氮的复合平面金属锂阳极由平板集流体、均匀覆盖在平面金属集流体两侧的掺氮的中空碳纳米笼与胶粘剂活性层、以及存在于掺氮中空碳纳米笼中的金属锂组成。其优势在于,高比表面积中空碳纳米笼的存在有效地降低了金属锂成核和沉积过程中的过电位,而氮原子的掺杂提供了均匀的成核和沉积位点,使金属锂得意于向中空碳纳米笼的内部生长,从而实现了锂金属持续循环过程中均匀的沉积和溶解。此外,超薄的碳壁有效的阻挡了界面反应的发生,大幅度提高锂金属电池的循环寿命。(The invention discloses a preparation method and application of a nitrogen-doped composite planar metal lithium anode. The nitrogen-doped composite planar metal lithium anode consists of a planar current collector, nitrogen-doped hollow carbon nanocages and an adhesive active layer which are uniformly covered on two sides of the planar metal current collector, and metal lithium existing in the nitrogen-doped hollow carbon nanocages. The method has the advantages that the existence of the hollow carbon nano cage with high specific surface area effectively reduces the overpotential in the nucleation and deposition process of the metallic lithium, and the doping of nitrogen atoms provides uniform nucleation and deposition sites, so that the metallic lithium is expected to grow towards the inside of the hollow carbon nano cage, and uniform deposition and dissolution in the continuous circulation process of the lithium metal are realized. In addition, the ultrathin carbon wall effectively prevents the occurrence of interface reaction, and greatly prolongs the cycle life of the lithium metal battery.)

1. A nitrogen-doped composite planar metal lithium anode comprises a flat metal current collector and an active layer compounded on the surface of the flat metal current collector; the method is characterized in that: the active layer comprises an adhesive and nitrogen-doped carbon nanocages dispersed in the adhesive, and the nitrogen-doped carbon nanocages are made of nitrogen-doped graphitized carbon; the nitrogen-doped carbon nanocage is provided with a filling cavity, and metal lithium is filled in the filling cavity.

2. The nitrogen-doped composite planar metallic lithium anode of claim 1, wherein: the material of the planar metal current collector is at least one of copper, titanium, nickel, iron and cobalt;

preferably, the thickness of the planar metal current collector is 5-100 μm; preferably 10 to 50 μm.

3. The nitrogen-doped composite planar metallic lithium anode of claim 1, wherein: the specific surface area of the nitrogen-doped carbon nanocage is 10-1000 m²(ii)/g; preferably 50 to 500m²(ii)/g; further preferably 85 to 350m²/g。

4. The nitrogen-doped composite planar metallic lithium anode of claim 1, wherein: the carbon wall thickness of the nitrogen-doped carbon nanocages is 0.5-100 nm; preferably 2-50 nm; more preferably 6 to 34 nm.

5. The nitrogen-doped composite planar metallic lithium anode of claim 1, wherein: the volume ratio of the filling cavity of the nitrogen-doped carbon nano cage is 50-99%; preferably 60 to 95%, and more preferably 65 to 85%.

6. The nitrogen-doped composite planar metallic lithium anode of claim 1, wherein: in the nitrogen-doped carbon nanocage, the nitrogen content is 0.05-10 at%; preferably 0.2 to 6 at.%; more preferably 0.5 to 3 at.%;

the nitrogen-doped carbon nanocages are obtained by roasting carbon nanocages with filling cavities in a nitrogen-containing atmosphere:

the nitrogen source of the nitrogen-containing atmosphere is nitrogen and/or ammonia;

the content of the nitrogen-doped atmosphere nitrogen source is 5-95 vol%; preferably 15 to 75 vol.%;

the roasting temperature is 600-1200 ℃; preferably 700-1100 ℃;

the roasting time is 0.4-20 h; preferably 0.6-15 h.

7. The nitrogen-doped composite planar metallic lithium anode of claim 1, wherein: the thickness of the active layer is 2-1000 mu m; preferably 8-800 μm;

preferably, the active layer is compounded on two planes of the planar metal current collector.

8. The nitrogen-doped composite planar metallic lithium anode of claim 1, wherein: the adhesive is at least one of polyvinyl alcohol, polytetrafluoroethylene, sodium carboxymethylcellulose, polyethylene, polypropylene, polyvinylidene chloride, SBR rubber, fluorinated rubber and polyurethane;

the ratio of the nitrogen-doped carbon nanocages to the adhesive is 50-98%; preferably 70 to 95%.

9. A method of making a nitrogen-doped composite planar lithium metal anode of any of claims 1 to 8, comprising: roasting the carbon nanocages with the filling cavities in a nitrogen-containing atmosphere to obtain nitrogen-doped carbon nanocages, mixing the nitrogen-doped carbon nanocages with an adhesive to prepare slurry, coating the slurry on the surface of the planar metal current collector, drying, and filling metal lithium into the filling cavities to obtain the nitrogen-doped composite planar metal lithium anode;

the method for filling the metallic lithium is electrodeposition and/or melting lithium filling, and the electrodeposition is preferred;

the amount of the filled metal lithium is 0.4-200 mAh/cm²(ii) a Further preferably 1.6-160 mAh/cm²(ii) a Further preferably 10 to 80mAh/cm²。

10. Use of the nitrogen-doped composite planar lithium metal anode according to any one of claims 1 to 8 or the nitrogen-doped composite planar lithium metal anode prepared by the preparation method according to claim 9, wherein: the material is used as an electrode material for assembling a metal lithium battery;

preferably, the metal lithium battery is a lithium sulfur battery, a lithium iodine battery, a lithium selenium battery, a lithium tellurium battery, a lithium oxygen battery or a lithium carbon dioxide battery.

Technical Field

The invention belongs to the field of energy storage devices, and particularly relates to the field of electrode materials of metal lithium batteries.

Background

Commercial lithium ion batteries have been widely used in 3C electronic products. However, the limitation of the theoretical specific capacity (372mAh/g) of the graphite negative electrode is limited, so that the lithium battery consisting of the graphite negative electrode is difficult to break through the bottleneck of the energy density of 250 Wh/kg. Therefore, the application of the method in the fields of smart grids, electric vehicles and the like is greatly limited. Therefore, the development of lithium batteries with higher energy density is imminent.

Metallic lithium is of great interest because of its high theoretical specific capacity of 3860 mAh/g. Lithium sulfur and lithium air batteries composed of metallic lithium may exhibit ultra-high energy densities of 2600Wh/kg and 3500Wh/kg, respectively. However, lithium dendrites, low coulombic efficiency and large volume effects limit the use of metallic lithium in these batteries. The stable artificial SEI film is constructed on the surface of the lithium metal foil or the copper foil, so that the growth of lithium dendrites can be inhibited, and the coulombic efficiency of lithium metal deposition and dissolution can be improved. Such as Nae-Lih Wu et al [ J.Luo, C. -C.Fang, N. -L.Wu, High polarity poly (vinylidenedifluoride) in coating for dendrimer-free and High-performance metal complexes, Advanced Energy Materials 8(2 (2018)) 1701482 and 1701488.]Coating polar polyvinylidene chloridePreparing a working electrode on a copper foil at 2mA/cm²A stable cycle of 60 turns is achieved at a current density of (1). And Jiang-Ping Tu et al [ Y. -j.Zhang, X. -h.Xia, D. -h.Wang, X. -1.Wang, C. -d.Gu, J. -p.Tu, Integrated reduced graphene oxide multilayers/Li composite and for reusable lithium metal batteries, RSC Advances 6(14) (2016) (11657) and 11664.]Pressing the graphene oxide film on the lithium sheet to prepare the graphene oxide modified lithium sheet at 0.4mA/cm²The stable cycle of 100 circles is realized under the current density, and the growth of lithium dendrites is successfully inhibited. But cannot solve the huge volume expansion and contraction during the deposition and dissolution of metallic lithium.

In addition, the apparent current density can be effectively reduced by adopting the 3D porous current collector with high specific surface area, so that the probability of occurrence of lithium dendrites is greatly reduced. Meanwhile, the huge internal cavity of the 3D porous current collector can effectively relieve the expansion and contraction of the volume in the lithium metal deposition/dissolution process. Such as Fokko M.Mulder et al [ Y.xu, A.S.Menon, P.P.R.M.L.Harks, D.C.Hermes, L.A.Haverkate, S.Unnikurishnan, F.M.Mulder, Honeomycin-like porous 3 Dnicol electrochemical deposition for stable Li and Na metal alloys, Energy storage materials 12(2018)69-78.]The porous nickel is prepared by a hydrogen bubble template method, and the volume effect of the porous nickel in the deposition/dissolution process of effective lithium is realized at 1mA/em²At a current density of 140 cycles. However, the high specific surface area of the 3D porous current collector also causes a large amount of interfacial reactions, which makes it difficult to improve the coulombic efficiency of the metallic lithium, and ultimately makes it difficult to apply such metallic lithium anodes industrially. Therefore, the problems of dendrite, low coulombic efficiency and huge volume effect are solved effectively, and the lithium metal anode is pushed to be practically applied.

Disclosure of Invention

Aiming at the problems of dendritic crystal, low coulombic efficiency, large volume effect and the like of the conventional lithium metal anode, the invention aims to provide a nitrogen-doped composite planar lithium metal anode, and aims to improve the electrical property of the obtained lithium metal anode by arranging an electrode material.

The second purpose of the invention is to provide a preparation method of the nitrogen-doped composite planar lithium metal anode.

The third purpose of the invention is to provide the application of the nitrogen-doped composite planar lithium metal anode.

A fourth object of the present invention is to provide a lithium metal battery loaded with the nitrogen-doped composite planar lithium metal anode.

A nitrogen-doped composite planar metal lithium anode comprises a flat metal current collector and an active layer compounded on the surface of the flat metal current collector; the active layer comprises an adhesive and nitrogen-doped carbon nanocages dispersed (for example, coated or embedded) in the adhesive, and the nitrogen-doped carbon nanocages are made of nitrogen-doped graphitized carbon; the nitrogen-doped carbon nanocage is provided with a filling cavity, and metal lithium is filled in the filling cavity.

The nitrogen-doped carbon nanocages can effectively reduce the apparent current density and relieve the probability of occurrence of dendrites; meanwhile, the expansion and contraction of the volume in the lithium deposition/dissolution process can be effectively relieved; further cooperating with nitrogen atoms to provide uniform nucleation sites, so that the metallic lithium grows to the interior of the carbon nano cage. The lithium anodes of the present invention ultimately achieve long cycle life.

The invention mainly solves the problems of reducing apparent current density, relieving volume effect and inhibiting interface reaction which are difficult to solve synergistically in the conventional lithium metal cathode. Therefore, the invention adopts the carbon nanocages with filling cavities, and through reasonable nitrogen doping, the metal lithium is successfully deposited in the cavities, the problem that the interface reaction is difficult to inhibit in the 3D lithium anode is fully solved, and the high current density (2-8 mA/cm) is realized²) And (4) stabilizing circulation.

Preferably, the planar metal current collector is a metal foil made of at least one of copper, titanium, nickel, iron and cobalt.

Preferably, the planar metal current collector is any one of planar single metal current collectors such as copper foil, titanium foil, nickel foil, iron foil, cobalt foil and the like and planar binary and ternary alloy current collectors thereof; preferably a copper foil.

The thickness of the planar metal current collector is 5-100 mu m.

Preferably, the thickness of the planar metal current collector is 10-50 μm.

The nitrogen-doped carbon nanocage is provided with a filling cavity (nitrogen-doped carbon nanocage shell), and the wall material (cage material of the nitrogen-doped carbon nanocage) of the filling cavity is the nitrogen-doped graphitized carbon; which helps to induce selective deposition of lithium within the loading chamber.

The nitrogen-doped carbon nanocage is of a graphitized carbon shell structure, and the carbon shell structure completely covers the metal lithium filled in the filling cavity. Researches find that parameters such as the specific surface area, the carbon wall thickness, the volume ratio of the filling chamber, the nitrogen doping amount and the like of the nitrogen-doped carbon nanocages are controlled, and the electrical performance of the nitrogen-doped composite planar metal lithium anode is further improved.

Preferably, the specific surface area of the nitrogen-doped carbon nanocages is 10-1000 m²/g。

Preferably, the specific surface area of the nitrogen-doped carbon nanocage is 50-500 m²(ii)/g; further preferably 85 to 350m²/g。

Preferably, the carbon wall thickness of the nitrogen-doped carbon nanocages is 0.5-100 nm.

Further preferably, the carbon wall of the nitrogen-doped carbon nanocage is 2-50 nm thick; more preferably 6 to 34 nm.

The filling cavity of the nitrogen-doped carbon nanocage accounts for 50-99% of the total volume.

Preferably, the filling cavity of the nitrogen-doped carbon nanocage accounts for 60-95% of the total volume; more preferably 65 to 85%.

The nitrogen content of the nitrogen-doped carbon nanocage is 0.05-10 at.%.

Preferably, the nitrogen content of the nitrogen-doped carbon nanocages is 0.2-6 at%; more preferably 0.5 to 3 at.%.

The nitrogen-doped carbon nanocages are obtained by roasting carbon nanocages with filling cavities in a nitrogen-containing atmosphere:

the nitrogen source of the nitrogen-containing atmosphere is nitrogen and/or ammonia.

The content of the nitrogen-doped atmosphere nitrogen source is 5-95 vol%; preferably 15 to 75 vol.%.

The roasting temperature is 600-1200 ℃; preferably 700-1100 ℃; further preferably 850 to 1000 ℃.

The roasting time is 0.4-20 h; preferably 0.6-15 h.

Preferably, the adhesive is at least one of polyvinyl alcohol, polytetrafluoroethylene, sodium carboxymethylcellulose, polyethylene, polypropylene, polyvinylidene chloride, SBR rubber, fluorinated rubber and polyurethane; preferably polytetrafluoroethylene.

Preferably, the ratio of the nitrogen-doped carbon nanocages to the adhesive is 50-98%; preferably 70 to 95 percent; more preferably 80% to 90%.

Preferably, the thickness of the active layer is 2 to 1000 μm.

More preferably, the thickness of the active layer is 8-800 μm.

The active layer is 0.4-150 times of the thickness of the planar metal current collector.

Preferably, the active layer is compounded on two planes of the planar metal current collector.

The nitrogen-doped composite planar metal lithium anode consists of a planar metal current collector, nitrogen-doped carbon nanocages uniformly covering two sides of the planar metal current collector, an active layer of an adhesive and metal lithium existing in the nitrogen-doped carbon nanocages.

The invention provides a preparation method of a nitrogen-doped composite planar metal lithium anode, which comprises the steps of roasting a carbon nano cage with a filling chamber in a nitrogen-containing atmosphere to obtain a nitrogen-doped carbon nano cage, mixing the nitrogen-doped carbon nano cage with an adhesive to prepare slurry, coating the slurry on the surface of a planar metal current collector, drying, and filling metal lithium into the filling chamber to obtain the nitrogen-doped composite planar metal lithium anode.

The nitrogen-doped carbon nanocages are obtained by roasting carbon nanocages with filling cavities in a nitrogen-containing atmosphere. It was found that controlling the verified nitrogen doping process (e.g. temperature, atmosphere, time, etc.) can further improve the electrical properties of the resulting lithium metal anode.

Preferably, the nitrogen source of the nitrogen-containing atmosphere is nitrogen and/or ammonia.

The nitrogen-containing atmosphere is a mixed atmosphere of a nitrogen source atmosphere and a protective atmosphere; for example, an argon atmosphere containing nitrogen or ammonia.

Preferably, the content of the nitrogen-doped atmosphere nitrogen source is 5-95 vol.%; preferably 15 to 75 vol.%.

Preferably, the roasting temperature is 600-1200 ℃; preferably 700 to 1100 ℃. (whether or not performance can be further improved in a preferred range, if so, the point can be illustrated and verified by the arrangement of the subsequent examples.)

Preferably, the roasting time is 0.4-20 h; preferably 0.6-15 h.

And slurrying the nitrogen-doped carbon nanocages and the adhesive by using an organic solvent, then coating the slurry on the surface of a planar metal current collector, and carrying out a lithium charging step after drying.

The method for filling the metallic lithium is preferably electrodeposition and/or fusion lithium filling; further preferred is electrodeposition.

Preferably, the lithium electrodeposition process is, for example: and taking the dried planar metal current collector as a working electrode and a lithium sheet as a counter electrode, and carrying out electrodeposition in an organic solvent containing lithium salt.

The amount of the filled metal lithium is 0.4-200 mAh/cm²(ii) a Further preferably 1.6-160 mAh/cm²(ii) a Further preferably 10 to 80mAh/cm²。

The invention also discloses application of the nitrogen-doped composite planar metal lithium anode as an electrode of a metal lithium battery.

The invention also includes a lithium metal battery loaded with the nitrogen-doped composite planar lithium metal anode.

Preferably, the metal lithium battery is a lithium sulfur battery, a lithium iodine battery, a lithium selenium battery, a lithium tellurium battery, a lithium oxygen battery or a lithium carbon dioxide battery.

Has the advantages that:

according to the nitrogen-doped composite planar lithium metal anode, the high specific surface area of the nitrogen-doped carbon nanocages can effectively reduce the apparent current density and relieve the probability of occurrence of dendrites. Meanwhile, the huge internal cavity (filling cavity) of the carbon nanocage can effectively relieve the expansion and contraction of the volume in the lithium deposition/dissolution process. While the nitrogen atoms provide uniform nucleation sites for the lithium metal to grow intentionally into the interior of the carbon nanocages. In addition, the existence of the ultrathin carbon nano wall inhibits the occurrence of interface reaction and greatly improves the coulombic efficiency. Such lithium anodes ultimately achieve long cycle life.

Drawings

Fig. 1 is a morphology diagram of carbon nanocages in example 1: (a) SEM picture; (b) TEM image.

Detailed Description

The following is a detailed description of the preferred embodiments of the invention and is not intended to limit the invention in any way, i.e., the invention is not intended to be limited to the embodiments described above, and modifications and alternative compounds that are conventional in the art are intended to be included within the scope of the invention as defined in the claims.