CN107768720B

CN107768720B - Non-negative secondary lithium battery based on liquid electrolyte

Info

Publication number: CN107768720B
Application number: CN201610685939.5A
Authority: CN
Inventors: 俞海龙; 黄学杰; 詹元杰; 赵俊年
Original assignee: Institute of Physics of CAS
Current assignee: Institute of Physics of CAS
Priority date: 2016-08-18
Filing date: 2016-08-18
Publication date: 2020-03-17
Anticipated expiration: 2036-08-18
Also published as: CN107768720A

Abstract

The invention provides a non-negative secondary lithium battery based on liquid electrolyte, which comprises a lithium-embedded positive electrode material, a diaphragm, the liquid electrolyte, a positive current collector and a negative current collector; wherein a seed layer is deposited on the surface of the negative current collector, and the liquid electrolyte contains non-lithium metal ions. The invention also provides a preparation method and application of the liquid electrolyte-based non-negative secondary lithium battery. The non-negative secondary lithium battery provided by the invention uses a liquid electrolyte system, can work circularly and can effectively inhibit dendritic crystal generation, and further, the metal mechanical barrier layer of the non-negative secondary lithium battery does not need to be prepared and packaged independently, and the technology is simple and suitable for industrial production.

Description

Non-negative secondary lithium battery based on liquid electrolyte

Technical Field

The invention belongs to the technical field of batteries, relates to a non-negative secondary lithium battery and a preparation method thereof, and particularly relates to a non-negative secondary lithium battery based on liquid electrolyte and a preparation method thereof.

Background

Because the metallic lithium has extremely high theoretical capacity (3840mAh/g) and simultaneously has the lowest reduction potential, the metallic lithium becomes the most ideal negative electrode material of the lithium battery. The energy density of the battery can be greatly improved by using the metal lithium as the negative electrode. Taking the currently commercialized cathode materials as examples, the materials are mainly lithium iron phosphate, lithium manganate and lithium nickel cobalt manganese (ternary materials), and the reversible specific capacities of the materials are 155 mAh/g, 110 mAh/g and 160mAh/g respectively. The current commercial graphite is matched with the negative electrode to prepare the full-cell, and the highest energy density can respectively reach 351, 324 and 403Wh/kg (calculated by the weight of the positive and negative active materials only).

Neudecker et al proposed in 2000 that the first solid-state thin-film, non-negative cell was composed of positive electrode materials, solid electrolyte and current collectors (see b.j. neudecker et al, j.electrochem. soc.,147 (2)) 517-523 (2000)). The battery directly uses the negative current collector as a negative electrode, when the battery is charged for the first time, metal lithium is deposited on the surface of the negative current collector, and the metal lithium is converted into lithium ions to return to the positive electrode in the discharging process, so that cyclic charge and discharge are realized. Such a non-negative electrode battery has many advantages over batteries using metallic lithium as the negative electrode: 1. the use of metal lithium with higher chemical activity in the preparation process is avoided, so that the production risk in the battery preparation process is reduced; 2. because the metal lithium is generated in the subsequent cycle process, the battery has no voltage before the first charging, so that the battery can be stored for a long time without self-discharging, and the battery can not generate current even if the battery is short-circuited, thereby having extremely high safety; 3. since no anode material is used only for the anode current collector, the anodeless battery can obtain higher energy density than the metallic lithium anode. When the conventional positive electrode material (lithium iron phosphate, lithium manganate and nickel cobalt lithium manganate) and the negative electrode current collector are assembled into a non-negative electrode battery, the energy density can reach 440, 527 and 646Wh/kg (calculated by the weight of positive and negative electrode active substances), and compared with the energy density of a graphite negative electrode, the energy density is respectively increased to 125%, 163% and 160% of the original energy density.

Although the theoretical energy density of such a battery is high, since lithium phosphate nitride (LiPON) is used as a solid electrolyte, the electrolyte consumes a large amount of lithium ions at the time of first charge, and the actual reversible capacity of the first cycle is only about 60% (see b.j. neudecker, et al, j.electrochem. soc.,147(2) 517-. Furthermore, due to the low ion mobility rate of the solid electrolyte, the battery is difficult to operate at high current densities, substantially maintaining current densities of several to tens of microamps, and even only capable of operating in nanoamp environments.

In contrast, liquid electrolytes have higher ion mobility and can operate at higher current densities than solid state batteries. But since metallic lithium has extremely high chemical activity, it may catalyze decomposition of the electrolyte to generate a Solid Electrolyte Interface (SEI) film at the interface. The SEI film insulates metallic lithium from contact with an electrolyte on the one hand, and can transport lithium ions at the same time. But on the other hand, since the SEI film of the surface layer is not uniformly dense and lacks sufficient mechanical strength, cracks occur during battery cycle charge/discharge, thereby inducing generation of metallic lithium dendrites from the cracks (see z.li et al, j.powersources 254(2014) 168-. The grown metal lithium dendrites continue to react with the electrolyte to form a new SEI film again, thereby consuming the electrolyte and reducing the content of recyclable lithium. In addition, as the dendrites grow, the bonding force between the anisotropic lithium dendrites and the substrate gradually weakens, and finally the anisotropic lithium dendrites are separated from the current collector to form non-conductive 'dead lithium'. These dead lithium can cause irreversible capacity, compromising the cycling capacity of the lithium battery. Most importantly, lithium metal accumulates as dendrites, where a portion of the vertical dendrites can pierce the insulating separator causing an internal cell short circuit that can cause the cell to fire or explode (see z. li et al, j. power sources 254(2014) 168-. Further, electrochemical deposition of lithium is often difficult to uniform, subject to the surface topography of the current collector and the degree of cleanliness. Non-uniform deposition further increases the generation of lithium dendrites during subsequent cycling.

The conventional methods for suppressing dendrites can be basically divided into ① adding a mechanical barrier layer to prevent the metal lithium dendrites from penetrating the diaphragm and ② adding an SEI film forming agent in the electrolyte for generating a thick and uniform SEI film.

A hard mechanical barrier layer is used to prevent dendrites from penetrating the membrane to cause internal short circuits, for example, an amorphous carbon film, an amorphous hollow carbon sphere, a boron nitride film, a graphene film, etc. with a certain mechanical strength are placed on the surface of lithium metal, and vertical growth of lithium dendrites is well blocked even at an extremely high current density (see g.y.zheng et al, naturentano. 2014,9,618; k.yan et al, Nano lett.2014,14, 6016-. However, to ensure that the cell will function properly, it is necessary that the mechanical barrier layer be thin enough to avoid limiting the lithium ion mobility rate, and that the thin film must also completely cover the lithium metal surface, otherwise the protection mechanism will fail (see g.y. zheng et al, Nature nanotech.2014,9,618; k.yan et al, Nano lett.2014,14, 6016-. However, mechanical barrier layers consume a certain amount of lithium to form SEI, and for example, carbon-based mechanical barrier layers, such as graphene and amorphous carbon, tend to form very thick SEI layers that consume the reversible capacity of the cell (see g.y.zheng et al, Nature nanotech.2014,9,618; k.yan et al, Nano lett.2014,14, 6016-. One method of protecting lithium metal has recently been reported by the Cui group as a seeding of gold nanoparticles into hollow amorphous carbon microspheres (see Kai Yan1 et al, Nature Energy,/nenergy.2016.10). Research finds that lithium is selectively deposited on gold particles in amorphous carbon spheres because the deposition barrier of metallic lithium on the surface of gold is smaller than that of amorphous carbon, so that the amorphous carbon plays a role in inhibiting dendritic growth of metallic lithium. However, the amorphous carbon interface produces SEI and thus consumes recyclable lithium, requiring several pre-cycles of the electrode before use, a process that may require one or several times the amount of metallic lithium consumed by the positive electrode to compensate for the loss of capacity consumed by SEI (see g.y. zheng et al, Nature nanotech.2014,9,618; and Kai Yan1 et al, Nature Energy,/nenergy.2016.10). The method has a serious defect besides complex manufacturing, namely a large amount of electrolyte exists in the amorphous carbon spheres, and the electrolyte continuously reacts with metal lithium before and after circulation to generate SEI and dead lithium and damage the circulation capacity. The method also needs to carry out capacity matching on the positive electrode and the negative electrode, if the space for accommodating the metallic lithium by the hollow amorphous carbon microspheres is insufficient, metallic lithium dendrite can be precipitated on the outer surface, and if the capacity of the negative electrode is higher than that of the positive electrode, a large amount of metallic lithium can be consumed, so that the reversible cycle capacity is greatly reduced. Therefore, to use the negative electrode, the negative electrode needs to be pre-charged and pre-discharged, then the negative electrode is disassembled, and then the battery is reassembled with the positive electrode, and the positive and negative electrode capacities of the battery need to be accurately regulated and controlled. The cycling efficiency tests of these documents all use metallic lithium as the counter electrode and employ a constant volume charging method, i.e. 1mAh of lithium is deposited onto the protective electrode every week, the ratio of the capacity that can be discharged to the charging capacity is studied and the coulombic efficiency calculated in this document is only calculated after pre-cycling (see g.y. zheng et al, Nature nanotech.2014,9,618; and Kai Yan1 et al, Nature energy,/nergy.2016.10). This test method is actually used to continuously replenish the cell with additional lithium, and even if such a test method is used in a carbonate electrolyte, the maximum coulombic efficiency for the first 10 cycles has not reached 96% (see g.y. zheng et al, Nature nanotech.2014,9,618; k.yan et al, Nano lett.2014,14, 6016-. Since in a non-negative cell all the lithium needs to be supplied by the positive electrode, the reversible capacity of the cell is greatly compromised if the mechanical barrier responsible for blocking the dendrites loses a significant amount of lithium. The current methods of mechanical barrier layer inhibition of metallic lithium dendrites cannot be used to construct liquid electrolyte based non-negative secondary lithium batteries.

Another method for suppressing lithium dendrites is to add an SEI film-forming agent into the electrolyte to improve the uniformity and mechanical strength of the SEI film. The aurbach group started to study from 1996 by changing electrolyte composition to form a stable SEI film to suppress lithium dendrites. Through a series of studies, it was found that dendritic dendrites do not appear at 100 cycles at extremely small currents by optimizing the electrolyte composition to some extent, but dendrite generation cannot be completely suppressed at all because the mechanical strength of SEI films of conventional thickness is not sufficient to suppress dendrite growth (see f. ding et al, jacs.2013,135, 4450-4456; d. aurbach, E et al, Solid State ionics.2002,148, 405-416; l. gireaud et al, electrochem. commun.2006,8, 1639-. However, it is reported by l.a. archer that the use of a hard ceramic separator with 30% LiF added to the electrolyte forms an ultra-thick SEI film that has good cycle stability without dendrite generation even in carbonate-based electrolytes (see y.lu et al, nat. mater.2014,13, 961-. However, the use of a large amount of LiF as an additive in the report can increase the internal resistance of the battery by an order of magnitude, on one hand, the electrochemical performance of the battery is greatly inhibited from losing the advantage of using a liquid electrolyte, and on the other hand, the increase of heat generation during current operation is detrimental to the safety of the battery.

Later on, some reports have been made that the addition of HF or trace amounts of water to the electrolyte means the reaction with lithium metal to form LiF as a passivation layer, which also inhibits the growth of vertical dendrites (see J.F. Qian et al, Nano Energy,2015,15, 135-. With the circulation, H in the electrolyte₂Li is continuously consumed by O and HF⁺The generated LiF greatly influences the cycle performance of the battery, and the problems of coulombic efficiency are avoided in the related documents. It is noteworthy that high cycle efficiency and dendrite suppression cannot be achieved simultaneously using optimized electrolyte composition, and most work is based on deposition cycles on metallic lithium surfaces, with less research on deposition directly on the current collector surface. This approach remains difficult to apply in a non-negative cell for recyclable Li⁺Even more than the mechanical barrier layer, and the residual HF in the electrolyte further deteriorates the cycle performance of the battery, which adversely affects the cycle performance and safety of the entire battery.

Based on the above reasons, to design a non-negative secondary lithium battery based on a liquid electrolyte, the fatal defects of the whole battery in cycle performance and safety performance caused by the growth problem of lithium dendrites must be solved, and meanwhile, the stability of interface SEI needs to be enhanced, so that the flatness of metal lithium deposition is improved, and the cycle efficiency of the battery is improved.

Disclosure of Invention

Based on the above, the present invention provides a non-negative secondary lithium battery, which aims at solving the problem of low energy density of the lithium ion secondary battery in the prior art. The non-negative secondary lithium battery provided by the invention is based on liquid electrolyte, and further, the non-negative secondary lithium battery provided by the invention is subjected to surface treatment on a negative current collector and is added with non-lithium metal salt, so that an ultrathin metal layer is formed when the battery is charged for the first time, the metal layer allows lithium ions to penetrate through and can be used as a mechanical barrier layer to inhibit the growth of metal lithium dendrites, and therefore, the non-negative secondary lithium battery provided by the invention greatly improves the cycle efficiency and safety of the battery.

In one aspect, the invention provides a liquid electrolyte-based non-negative secondary lithium battery, which comprises a lithium-embedded positive electrode material, a diaphragm, a liquid electrolyte, a positive current collector and a negative current collector; wherein an oxide layer on the surface of the negative current collector has been removed and a seed layer is deposited, and the liquid electrolyte contains non-lithium metal ions.

Preferably, the thickness of the seed crystal layer is 1-200 nm; more preferably, the thickness of the seed layer is 5-150 nm; further preferably, the thickness of the seed crystal layer is 10-100 nm; most preferably, the thickness of the seed layer is 10-30 nm;

preferably, the positive electrode current collector is a metal current collector, more preferably, the metal current collector is formed of aluminum;

preferably, the negative electrode current collector is a metal current collector or a non-metal current collector; more preferably, the negative electrode metal current collector is formed of a material selected from the group consisting of copper, nickel, cobalt, titanium, iron; further preferably, the negative metal current collector is formed of copper;

still further preferably, the negative non-metallic current collector is formed of a material selected from carbon fiber cloth, carbon fiber paper, or a conductive organic polymer.

Preferably, the thickness of the negative electrode current collector is 1 to 200 μm; more preferably, the thickness of the negative electrode current collector is 1 to 150 μm; further preferably, the thickness of the negative electrode current collector is 1 to 10 μm.

Preferably, the oxide layer on the surface of the negative current collector may be removed using a method known in the art, preferably, the oxide layer on the surface of the negative current collector is removed by one or more of physical, chemical polishing, high-temperature reduction, or plasma etching; more preferably, the plasma etching is Ar ion beam etching.

Preferably, a seed crystal layer is deposited on the surface of the negative electrode current collector by one or more methods of spin coating, magnetron sputtering, electron beam evaporation and thermal evaporation;

preferably, the seed crystal layer material is selected from materials that can undergo an electrochemical alloying process with lithium at room temperature, and more preferably, the seed crystal layer material is selected from one of gold, silver, zinc, magnesium, platinum, or an alloy of two or more thereof.

Preferably, the deposition potential of the non-lithium metal ions in the liquid electrolyte is higher than that of lithium ions; more preferably, the non-lithium metal ions are selected from electrochemically inert metal ions; further preferably, the non-lithium metal ion is selected from Ti⁺、Cu⁺、Cu²⁺、Ni⁺、Ni²⁺、Mo⁶⁺、Mo⁴⁺、Mo²⁺、Al³⁺Co + and Co²⁺One or more of; still further preferably, the non-lithium metal ion is Cu⁺Or/and Cu²⁺；

Preferably, the content of the non-lithium metal ions is 1-200 mM; more preferably, the content of the non-lithium metal ions is 5 to 100 mM; further preferably, the content of the non-lithium metal ions is 10 to 60 mM;

preferably, the non-lithium metal ion is in the form of a non-lithium metal ion organic or inorganic salt;

preferably, the non-lithium metal ion organic or inorganic salt is selected from one or more of anhydrous copper sulfate, anhydrous copper nitrate, anhydrous copper acetate, tetraacetonitrile copper hexafluorophosphate, copper bis (2,2,6, 6-tetramethyl-3, 5-heptanedionate), tetrabutyl titanate, titanium isopropoxide, titanium nitrate, molybdenum oxydithiophosphate, molybdenum nitrate, molybdenum diiodide, cobalt naphthenate, cobalt stearate and cobalt nitrate.

In another aspect, the present invention provides a method for preparing the above non-negative secondary lithium battery, the method comprising the steps of:

1) removing an oxide layer of a negative current collector, and then depositing a seed crystal layer on the surface of the negative current collector to obtain a treated negative current collector;

the oxide layer on the surface of the negative current collector may be removed using a method known in the art, preferably, by one or more of physical, chemical polishing, high-temperature reduction, or plasma etching; more preferably, the plasma etching is Ar ion beam etching.

Preferably, a seed crystal layer is deposited on the surface of the negative electrode current collector by one or more methods of spin coating, magnetron sputtering, electron beam evaporation and thermal evaporation; more preferably, a seed crystal layer is deposited on the surface of the negative electrode current collector by magnetron sputtering; further preferably, the current intensity of the magnetron sputtering is 0.1-2 mA; preferably 0.5-1.5 mA; most preferably 1 mA; the deposition time is 60-120s, preferably 80-100 s;

preferably, the seed crystal layer material is selected from materials which can perform an electrochemical alloying process with lithium at room temperature, more preferably, the seed crystal layer material is selected from one or two or more of gold, silver, zinc, magnesium and platinum;

2) adding non-lithium metal ions into the liquid electrolyte to obtain liquid electrolyte containing the non-lithium metal ions;

preferably, the deposition potential of the non-lithium metal ions in the liquid electrolyte is higher than that of lithium ions; more preferably, the non-lithium metal ions are selected from electrochemically inert metal ions; further preferably, the non-lithium metal ion is selected from Ti⁺、Cu⁺、Cu²⁺、Ni⁺、Ni²⁺、Mo⁶⁺、Mo⁴⁺、Mo²⁺、Al³⁺、Co⁺And Co²⁺One or more of; still further preferably, the non-lithium metal ion is Cu⁺Or/and Cu²⁺；

preferably, the non-lithium metal ion organic or inorganic salt is selected from one or more of anhydrous copper sulfate, anhydrous copper nitrate, anhydrous copper acetate, tetraacetonitrile copper hexafluorophosphate, copper bis (2,2,6, 6-tetramethyl-3, 5-heptanedionate), tetrabutyl titanate, titanium isopropoxide, titanium nitrate, molybdenum oxydithiophosphate, molybdenum nitrate, molybdenum diiodide, cobalt naphthenate, cobalt stearate and cobalt nitrate;

3) assembling the lithium-embedded positive electrode material, the positive electrode current collector, the diaphragm, the treated negative electrode current collector prepared in the step 1) and the liquid electrolyte prepared in the step 2) together to obtain the non-negative secondary lithium battery.

In still another aspect, the present invention provides a use of the above-mentioned non-negative secondary lithium battery for power batteries of automobiles and electric tools, and energy storage devices of solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power sources, or communication base stations.

The non-negative electrode battery of the invention is a secondary lithium battery which only uses a lithium-embedded positive electrode material as a positive electrode and uses metal lithium deposited on a negative electrode current collector during first charging as a negative electrode under the condition of not using a negative electrode material. And in the initial stage of the first charging of the battery, non-lithium metal ions in the electrolyte are firstly deposited on the surface of the negative electrode current collector to form a metal mechanical barrier layer, and the metal mechanical barrier layer can allow lithium ions to pass through but can prevent lithium dendrite from penetrating. Since the seed layer is below the metallic mechanical barrier layer, lithium metal is preferentially deposited in the seed layer to form lithium metal. The lithium metal becomes the negative pole of the battery and is wrapped and protected by the metal mechanical barrier layer. The inventor finds that the deposition uniformity of metal lithium ions and non-lithium metal ions can be improved by subjecting the surface of the negative electrode current collector of the lithium ion secondary battery to physical, chemical polishing, high-temperature reduction or plasma etching treatment to remove the oxide layer on the surface to the maximum extent, and further depositing an ultrathin seed crystal layer on the treated surface of the negative electrode current collector. Further, the present inventors have found that if a small amount of non-lithium metal ions is contained in the liquid electrolytic solution, the non-lithium metal ions and the lithium ions have different deposition potentials. Non-lithium metal ions are deposited on the surface of a seed crystal layer on a negative current collector before metal lithium ions in the first charging process, and a mechanical barrier layer is generated in situ, so that the generation of lithium dendrites is inhibited. Because this layer of metal mechanical barrier layer is through the mode preparation of in situ electrodeposition, so need not through the sample transfer, can effectually avoid the metal level to take place the oxidation to because metal mechanical barrier layer has ductility and elasticity, be different from general hard mechanical barrier layer, more can attach on the metal lithium surface, thereby reduce metal lithium and electrolyte area of contact, thereby reduce the passivation of metal lithium and increase cycle efficiency.

Compared with the prior art, the non-negative secondary lithium battery provided by the invention has the following advantages:

1) the metal mechanical barrier layer of the non-negative secondary lithium battery provided by the invention is different from the conventional mechanical barrier layer and can be attached to the surface of metal lithium, so that the contact area of the metal lithium and electrolyte is reduced, the passivation of the metal lithium is reduced, and the cycle efficiency is increased.

2) The mechanical barrier layer of the non-negative secondary lithium battery provided by the invention does not need to be prepared independently, so that the preparation cost is reduced.

3) The seed crystal layer is arranged on the negative current collector of the non-negative secondary lithium battery, so that the uniform mechanical barrier layer can be better formed, independent preparation and packaging are not needed, the technology is simple, and the non-negative secondary lithium battery is suitable for industrial production.

4) The non-negative secondary lithium battery provided by the invention uses a liquid electrolyte system, can work circularly, has higher coulombic efficiency and can effectively inhibit dendritic crystals from being generated.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a scanning electron micrograph of a copper foil according to example 3 of the present invention at different magnifications after acid treatment, wherein FIG. 1(a) is a scanning electron micrograph at a magnification of 10k and FIG. 1(b) is a scanning electron micrograph at a magnification of 100 k; as can be seen from the figure, the surface of the copper foil is covered with a layer of nano-particles with the size of about 30 nm;

fig. 2 is X-ray energy dispersion spectrum data of the copper foil according to example 3 of the present invention after acid treatment, and it is shown by the X-ray energy dispersion spectrum data that the surface of the copper foil contains 4 atomic% of oxygen, indicating that the surface of the copper foil is covered with an oxide layer.

Fig. 3 is a scanning electron micrograph of a copper foil according to example 3 of the present invention, which is subjected to Ar ion beam etching and has different magnifications, wherein fig. 3(a) is a scanning electron micrograph of 5k times and fig. 3(b) is a scanning electron micrograph of 100k times; as can be seen from the figure, the surface of the etched copper foil was smooth.

Fig. 4 is a scanning electron micrograph of a copper foil with gold sputtering (a3) according to example 3 of the present invention, from which it can be seen that the surface of the copper foil is coated with a layer of ultra-thin nanoparticles.

Fig. 5 is a graph of the 50-cycle coulombic efficiencies of test examples C1, C3, C5 and F3, from which it can be seen that test example C5, which did not remove the surface oxide layer, had only an extremely low coulombic efficiency. The experimental example C1 with the oxide layer removed alone is significantly improved over the experimental example without the oxide layer removed. The experimental example C3 with the seed layer and the oxide layer removed was significantly higher in coulombic efficiency at the beginning of the cycle than the case without the seed layer, but showed a tendency to decay in the subsequent cycles. And the test example F3 has the highest coulombic efficiency from the initial stage to the end of the cycle and has good cycle stability.

FIG. 6 is a scanning electron micrograph of test examples C3 and F3 after ten cycles, showing that: the lithium metal with a metallic mechanical barrier layer has a flat surface after cycling and does not form dendrites (F3). While the metallic lithium surface without the metallic mechanical barrier layer is covered with a large amount of lithium dendrites while severe passivation occurs (C3). Further proves that the metallic mechanical barrier layer formed by in-situ electrochemical deposition can effectively inhibit the generation of lithium dendrites.

Detailed Description

The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention.

Example 1

Using 10 μm copper foil as negative current collector, the copper foil was immersed in 1% HNO₃Ultrasonic cleaning with water solution for 5min to remove oxide layer. And cleaning the copper foil subjected to acid treatment by using ethanol, and drying at room temperature after cleaning. And then further removing the residual oxide layer on the surface by using Ar ion beam etching. The treated copper foil was quickly transferred to a glove box where it was cut into a wafer having a diameter of 15mm by a sheet punch. The samples after the metal spraying were directly stored in a glove box and ready for the next step of electrochemical performance testing (this material was designated as a 1).

Example 2

Using 10 μm copper foil as negative current collector, the copper foil was immersed in 1% HNO₃Ultrasonic cleaning with water solution for 5min to remove oxide layer. And cleaning the copper foil subjected to acid treatment by using ethanol, and drying at room temperature after cleaning. And then further removing the residual oxide layer on the surface by using Ar ion beam etching. The treated copper foil was quickly transferred to a glove box where the current collector was cut into disks with a diameter of 15mm by a die cutter. The samples were gold-sputtered using a small magnetron sputtering apparatus placed in a glove box and deposited at a current of 1mA for 60 s.

The samples after the metal spraying were directly stored in a glove box and ready for the next step of electrochemical performance testing (this material was designated as a 2).

Example 3

Using 10 μm copper foil as negative current collector, the copper foil was immersed in 1% HNO₃Ultrasonic cleaning with water solution for 5min to remove oxide layer. And cleaning the copper foil subjected to acid treatment by using deionized water and ethanol, and airing at room temperature after cleaning. And then further removing the residual oxide layer on the surface by using Ar ion beam etching. The treated copper foil was quickly transferred to a glove box where the current collector was cut into disks with a diameter of 15mm by a die cutter. The samples were gold-sputtered using a small magnetron sputtering apparatus placed in a glove box and deposited at a current of 1mA for 120 s. The samples after the metal spraying were directly stored in a glove box and ready for the next step of electrochemical performance testing (this material was designated as a 3).

Example 4

Using 10 μm nickel foil as the negative current collector, the nickel foil was immersed in 1% HNO₃Ultrasonic cleaning with water solution for 5min to remove oxide layer. And cleaning the nickel foil subjected to acid treatment by using deionized water and ethanol, and airing at room temperature after cleaning. Annealing was carried out at 300 ℃ for 3 hours in a 10% hydrogen/argon atmosphere. The treated nickel foil was quickly transferred to a glove box where the current collector was cut into disks with a diameter of 15mm by a die cutter. The samples were gold-sputtered using a small magnetron sputtering apparatus placed in a glove box and deposited at a current of 1mA for 120 s. The samples after the metal spraying were directly stored in a glove box and ready for the next step of electrochemical performance testing (this material was designated as a 4).

Example 5

And (3) using a 10-micron copper foil as a negative current collector, washing the copper foil by using deionized water and ethanol, and drying at room temperature after washing. The treated copper foil was quickly transferred to a glove box where the current collector was cut into disks 15mm in diameter by a die cutter in preparation for the next step of electrochemical performance testing (this material was designated a 5).

Example 6

Using 150 μm copper foil as negative current collector, the copper foil was immersed in 1% HNO₃Ultrasonic cleaning with water solution for 5min to remove oxide layer. And cleaning the copper foil subjected to acid treatment by using ethanol, and drying at room temperature after cleaning. And then further removing the residual oxide layer on the surface by using Ar ion beam etching. The treated copper foil was quickly transferred to a glove box where the current collector was cut into disks with a diameter of 15mm by a die cutter. The samples were platinum sputtered using a small magnetron sputtering apparatus placed in a glove box and deposited at a current of 0.1mA for 120 s. The platinum sprayed samples were stored directly in the glove box and ready for the next step of the electrochemical performance test (this material was designated A6).

Example 7

Using a 200 μm cobalt foil as the negative current collector, the cobalt foil was immersed in 1% HNO₃Ultrasonic cleaning with water solution for 5min to remove oxide layer. And cleaning the cobalt foil subjected to acid treatment by using ethanol, and drying at room temperature after cleaning. Then make it possible toAnd further removing the residual oxide layer on the surface by Ar ion beam etching. The treated cobalt foil was quickly transferred to a glove box where the current collector was cut into disks with a diameter of 15mm by a die cutter. And sputtering Zn on the surface of the sample by using a magnetron sputtering device, and depositing the cobalt foil by using a high-purity Zn target in a low-vacuum argon atmosphere. The deposition current was set at 100mA and the deposition time was 5 s. The Zn-sprayed samples were stored directly in a glove box and ready for further electrochemical performance testing (this material was designated a 7).

Example 8

Using a 20 μm copper foil as the negative current collector, the copper foil was immersed in 1% HNO₃Ultrasonic cleaning with water solution for 5min to remove oxide layer. And cleaning the copper foil subjected to acid treatment by using ethanol, and drying at room temperature after cleaning. And then further removing the residual oxide layer on the surface by using Ar ion beam etching. The treated copper foil was quickly transferred to a glove box where the current collector was cut into disks with a diameter of 15mm by a die cutter. Using Ag sheet as evaporation source, the air pressure in the vacuum evaporation cavity is reduced to x 10^-4After Pa, the current of the apparatus was set to 90A, when the pressure was increased to 3.0X 10^-3Pa for 60 s. The vacuum evaporated samples were stored directly in the glove box and ready for the next step of electrochemical performance testing (this material was designated as A8).

Topography characterization

FIG. 1 is a scanning electron micrograph of a copper foil according to example 1 of the present invention at different magnifications after acid treatment, wherein FIG. 1(a) is a scanning electron micrograph at a magnification of 10k and FIG. 1(b) is a scanning electron micrograph at a magnification of 100 k; as can be seen from the figure, the surface of the copper foil is covered with a layer of nano-particles with the size of about 30 nm;

fig. 2 is X-ray energy dispersion spectrum data of the copper foil according to example 1 of the present invention after acid treatment, and it is shown by the X-ray energy dispersion spectrum data that the surface of the copper foil contains 4 atomic% of oxygen, indicating that the surface of the copper foil is covered with an oxide layer.

Fig. 3 is a scanning electron micrograph of a copper foil according to example 1 of the present invention, which is subjected to Ar ion beam etching and has different magnifications, wherein fig. 3(a) is a scanning electron micrograph of 5k times and fig. 3(b) is a scanning electron micrograph of 100k times; as can be seen from the figure, the surface of the etched copper foil was smooth.

Performance testing

Negative current collectors a1 to A8 prepared in examples 1 to 8 were assembled into button cells according to the following procedure.

(1) Preparation of Positive electrode sheet

Commercial carbon-coated lithium iron phosphate is used as a positive electrode material, carbon black is used as a conductive additive, polyvinylidene fluoride (PVDF) is used as a binder, the carbon-coated lithium iron phosphate and the carbon black are dispersed in N-methyl pyrrolidone (NMP) according to the weight ratio of 90:5:5, and the mixture is uniformly mixed to prepare uniform positive electrode slurry. The uniform positive electrode slurry was uniformly coated on an aluminum foil current collector having a thickness of 15 μm using a doctor blade having a thickness of 75 μm, and dried in a vacuum drying oven at 50 ℃. The dried pole piece is placed under a roller press for rolling (the pressure is about 0.4MPa multiplied by 1.5 cm)²) Cutting the pole piece into a wafer with the diameter of phi 14mm, placing the wafer in a vacuum oven to be dried for 6 hours at the temperature of 120 ℃, and quickly taking out and transferring the wafer to a glove box to be used as a positive pole piece after natural cooling.

(2) 1M LiPF was used as an electrolyte₆Dissolved in EC/DMC (volume ratio 1:1), copper tetraacetonitrilephosphonate was added to the electrolytes in concentrations of 0mM, 10mM, 30mM and 50mM, respectively, as four electrolytes (B1-B4).

(3) 1M LiPF was used as an electrolyte₆Dissolved in EC/DMC (1: 1 by volume), copper sulfate was added to the electrolytes in four concentrations of 10mM, 30mM and 50mM, respectively, as counted (B5-B7).

(4) 1M LiPF was used as an electrolyte₆Dissolved in EC/DMC (volume ratio 1:1), tetrabutyl titanate was added to the electrolytes in four electrolytes at concentrations of 10mM, 30mM and 50mM, respectively, as counted (B8-B10).

(5) 1M LiPF was used as an electrolyte₆Dissolving in EC/DMC (volume ratio 1:1), adding molybdenum diiodide into electrolyte to obtainFour electrolytes at concentrations of 10mM, 30mM and 50mM were counted as (B11-B13), respectively.

(6) Assembling non-negative secondary lithium battery

And (3) in a glove box filled with inert atmosphere, taking the treated copper foil (A1-A5) as a negative electrode current collector of the battery, taking a PP/PE/PP three-layer film as a diaphragm to be placed between a positive electrode and a negative electrode, dropwise adding 150 mu L of electrolyte B1, taking the positive electrode piece prepared in the step (1) as the positive electrode, and assembling into a button battery (counted as C1-C5) with the model of CR 2032.

And (3) in a glove box filled with inert atmosphere, taking the treated copper foil (A1-A5) as a negative electrode current collector of the battery, taking a PP/PE/PP three-layer film as a diaphragm to be placed between a positive electrode and a negative electrode, dropwise adding 150 mu L of electrolyte B2, taking the positive electrode piece prepared in the step (1) as the positive electrode, and assembling into a button battery (counted as D1-D5) with the model of CR 2032.

And (3) in a glove box filled with inert atmosphere, taking the treated copper foil (A1-A5) as a negative electrode current collector of the battery, taking a PP/PE/PP three-layer film as a diaphragm to be placed between a positive electrode and a negative electrode, dropwise adding 150 mu L of electrolyte B3, taking the positive electrode piece prepared in the step (1) as the positive electrode, and assembling into a button battery (counted as E1-E5) with the model of CR 2032.

In a glove box filled with inert atmosphere, the treated copper foil (A1-A5) is used as the negative current collector of the battery, a three-layer film of PP/PE/PP is used as a diaphragm and is placed between a positive electrode and a negative electrode, 150 mu L of electrolyte B4 is dripped, the positive pole piece prepared in the step (1) is used as the positive electrode, and the button cell (counted as F1-F5) with the model CR2032 is assembled

In a glove box filled with inert atmosphere, the treated copper foil (A6-A8) is used as the negative current collector of the battery, a PP/PE/PP three-layer film is used as a diaphragm and is placed between a positive electrode and a negative electrode, 150 mu L of electrolyte B2 is dripped, the positive pole piece prepared in the step (1) is used as the positive electrode, and the button cell (counted as G1-G3) with the model CR2032 is assembled

In a glove box filled with inert atmosphere, the treated copper foil (A6-A8) is used as the negative current collector of the battery, a PP/PE/PP three-layer film is used as a diaphragm and is placed between a positive electrode and a negative electrode, 150 mu L of electrolyte B3 is dripped, the positive pole piece prepared in the step (1) is used as the positive electrode, and the button cell (counted as H1-H3) with the model CR2032 is assembled

In a glove box filled with inert atmosphere, the treated copper foil (A6-A8) is used as the negative current collector of the battery, a PP/PE/PP three-layer film is used as a diaphragm and is placed between a positive electrode and a negative electrode, 150 mu L of electrolyte B4 is dripped, the positive pole piece prepared in the step (1) is used as the positive electrode, and the button cell (counted as I1-I3) with the model CR2032 is assembled

In a glove box filled with inert atmosphere, the treated copper foil A3 is used as the negative current collector of the battery, a PP/PE/PP three-layer film is used as a diaphragm and is placed between a positive electrode and a negative electrode, 150 mu L of electrolyte (B5-B7) is respectively dripped, the positive pole piece prepared in the step (1) is used as the positive electrode, and the button cell (counted as J1-J3) with the model CR2032 is assembled

In a glove box filled with inert atmosphere, the treated copper foil A3 is used as the negative current collector of the battery, a PP/PE/PP three-layer film is used as a diaphragm and is placed between a positive electrode and a negative electrode, 150 mu L of electrolyte (B8-B10) is respectively dripped, the positive pole piece prepared in the step (1) is used as the positive electrode, and the button cell (counted as K1-K3) with the model CR2032 is assembled

In a glove box filled with inert atmosphere, the treated copper foil A3 is used as the negative current collector of the battery, a PP/PE/PP three-layer film is used as a diaphragm and is placed between a positive electrode and a negative electrode, 150 mu L of electrolyte (B11-B13) is respectively dripped, the positive pole piece prepared in the step (1) is used as the positive electrode, and the button cell (counted as L1-L3) with the model CR2032 is assembled

Test examples 1 to 38

The 38 button cells (C1-C5, D1-D5, E1-E5, F1-F5, G1-G3, H1-H3, I1-I3, J1-J3, K1-K and L1-L3) prepared by different methods are respectively kept still for 10 hours at room temperature (25 ℃), and then a blue cell charge-discharge tester is used for carrying out charge-discharge cycle test on the prepared button cells. Firstly, the mixture is heated at room temperature (25 ℃) at 0.1mA/cm²The d current density is cycled for 50 times, and the charge-discharge voltage range of the battery is controlled to be 2.5-3.8V.

Table 1 shows the test results of test examples 1 to 20 (C1-C5, D1-D5, E1-E5 and F1-F5).

TABLE 1

Table 2 shows the test results of Experimental examples 21-29 (G1-G3, H1-H3, and I1-I3).

TABLE 2

G1 92.1％	H1 93.5％	I1 95.3％
			G2 91.4％	H2 93.6％	I2 94.8％
G3 92.2％	H3 93.4％	I3 95.3％

Table 3 shows the test results (J1-J3, K1-K and L1-L3) of test examples 30 to 38.

TABLE 3

J1 95.1	K1 94.2	L1 95.6
			J2 95.5	K2 95.6	L2 96.4
J3 96.6	K3 96.2	L4 97.1

FIG. 6 is a scanning electron micrograph of test examples C3 and F1 after ten cycles, showing that: the lithium metal with a metallic mechanical barrier layer has a flat surface after cycling and does not form dendrites (F3). While the metallic lithium surface without the metallic mechanical barrier layer is covered with a large amount of lithium dendrites while severe passivation occurs (C3). Further proves that the metallic mechanical barrier layer formed by in-situ electrochemical deposition can effectively inhibit the generation of lithium dendrites.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A non-negative secondary lithium battery based on liquid electrolyte comprises a lithium-embedded positive electrode material, a diaphragm, the liquid electrolyte, a positive current collector and a negative current collector; the method is characterized in that an oxide layer on the surface of the negative electrode current collector is removed and a seed crystal layer is deposited, and the liquid electrolyte contains non-lithium metal ions;

wherein the non-lithium metal ion is selected from Ti⁺、Cu⁺、Cu²⁺、Ni⁺、Ni²⁺、Mo⁶⁺、Mo⁴⁺、Mo²⁺、Al³⁺、Co⁺And Co²⁺One or more of;

wherein the seed crystal layer material is selected from one or two or more of gold, silver, zinc, magnesium and platinum.

2. The lithium secondary battery as claimed in claim 1, wherein the seed layer has a thickness of 1 to 200 nm.

3. The lithium secondary battery as claimed in claim 1, wherein the seed layer has a thickness of 5 to 150 nm.

4. The lithium secondary battery as claimed in claim 1, wherein the seed layer has a thickness of 10 to 100 nm.

5. The lithium secondary battery as claimed in claim 1, wherein the seed layer has a thickness of 10 to 30 nm.

6. The lithium secondary battery of claim 1, wherein the positive current collector is a metal current collector.

7. The lithium secondary battery of claim 6, wherein the metallic current collector is formed of aluminum.

8. The non-negative secondary lithium battery according to claim 1, wherein the negative electrode current collector is a metal current collector or a non-metal current collector.

9. The non-negative secondary lithium battery of claim 8, wherein the negative metal current collector is formed of a material selected from the group consisting of copper, nickel, cobalt, titanium, and iron.

10. The non-negative secondary lithium battery of claim 8, wherein the negative metal current collector is formed of copper.

11. The lithium secondary battery of claim 8, wherein the negative non-metallic current collector is formed of a material selected from carbon fiber cloth, carbon fiber paper, or a conductive organic polymer.

12. The non-negative secondary lithium battery according to claim 1, wherein the negative electrode current collector has a thickness of 1 to 200 μm.

13. The non-negative secondary lithium battery according to claim 1, wherein the negative electrode current collector has a thickness of 1 to 150 μm.

14. The non-negative secondary lithium battery according to claim 1, wherein the negative electrode current collector has a thickness of 1 to 10 μm.

15. The non-negative secondary lithium battery according to claim 1, wherein the oxide layer on the surface of the negative current collector is removed by one or more of physical, chemical polishing, high-temperature reduction, or plasma etching.

16. The lithium secondary battery of claim 15, wherein the plasma etching is Ar ion beam etching.

17. The lithium secondary battery of claim 1, wherein the seed layer is deposited on the surface of the negative current collector by one or more of spin coating, magnetron sputtering, electron beam evaporation, and thermal evaporation.

18. The lithium secondary battery of claim 1, wherein the non-lithium metal ion is Cu⁺Or Cu²⁺。

19. The lithium secondary battery as claimed in claim 1, wherein the content of the non-lithium metal ion is 1 to 200 mM.

20. The lithium secondary battery as claimed in claim 1, wherein the content of the non-lithium metal ion is 5 to 100 mM.

21. The lithium secondary battery as claimed in claim 1, wherein the content of the non-lithium metal ion is 10 to 60 mM.

22. The lithium secondary battery of claim 1, wherein the non-lithium metal ion is in the form of an organic or inorganic salt of a non-lithium metal ion.

23. The lithium secondary battery of claim 22, wherein the organic or inorganic salt of the non-lithium metal ion is selected from one or more of anhydrous copper sulfate, anhydrous copper nitrate, anhydrous copper acetate, copper tetraacetonitrileate hexafluorophosphate, copper bis (2,2,6, 6-tetramethyl-3, 5-heptanedionate), tetrabutyl titanate, titanium isopropoxide, titanium nitrate, molybdenum dialkyldithiophosphate, molybdenum nitrate, molybdenum diiodide, cobalt naphthenate, cobalt stearate, and cobalt nitrate.

24. The method for manufacturing a non-negative secondary lithium battery according to any one of claims 1 to 23, comprising the steps of:

25. The method of claim 24, wherein in step 1), the oxide layer on the surface of the negative current collector is removed by one or more of physical, chemical polishing, high temperature reduction, or plasma etching.

26. The method of claim 25, wherein the plasma etch is an Ar ion beam etch.

27. The method according to claim 24, wherein in step 1), a seed layer is deposited on the surface of the negative current collector by one or more of spin coating, magnetron sputtering, electron beam evaporation, thermal evaporation.

28. The method according to claim 24, wherein, in step 1), a seed layer is deposited to the surface of the negative current collector by magnetron sputtering.

29. The method of claim 28, wherein the magnetron sputtering has a current intensity of 0.1-2mA and a deposition time of 60-120 s.

30. The method of claim 29, wherein the magnetron sputtering has a current intensity of 0.5-1.5 mA.

31. The method of claim 29, wherein the magnetron sputtering has a current intensity of 1 mA.

32. The method of claim 29, wherein the deposition time of the magnetron sputtering is 80-100 s.