CN109786808A

CN109786808A - A kind of lithium metal battery nitrile electrolyte and the lithium metal battery using the electrolyte

Info

Publication number: CN109786808A
Application number: CN201811534126.1A
Authority: CN
Inventors: 崔光磊; 胡正林; 董杉木; 咸芳; 张舒; 徐红霞
Original assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Current assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Priority date: 2018-12-14
Filing date: 2018-12-14
Publication date: 2019-05-21

Abstract

The invention discloses a kind of lithium metal battery nitrile electrolyte and using the lithium metal battery of the electrolyte, it is made of at least two kinds of lithium salts and at least one solid containing cyano functional group or liquid reagent.Lithium metal battery provided by the invention nitrile electrolyte, ionic conductivity at room temperature can achieve with traditional comparable level of carbonates electrolyte, 10 can be reached^‑2S cm^‑2.What is assembled using the electrolyte is the battery of Soft Roll in face amount (4mA h cm 30 weeks big using lithium anode^‑2) still have after circulation 95% or so capacity retention ratio, the capacity retention ratio (55%) compared to the Soft Roll of conventional carbonate class electrolyte assembling is much greater.And by cobalt acid lithium/lithium half-cell under the high voltage of 3-4.7V 1C circulation, still may be implemented 500 times circulation after 74% capacity retention ratio.And the lithium metal battery nitrile electrolyte can effectively inhibit soft-package battery flatulence.

Description

A kind of lithium metal battery nitrile electrolyte and the lithium metal battery using the electrolyte

Technical field

The present invention relates to Room Temperature Ionic Liquid Electrolyte, specifically a kind of non-carbonic ester suitable for lithium metal battery The double salt ion nitrile electrolyte systems of class, room temperature.

Background technique

Important component of the electrolyte as lithium metal battery has the properties of lithium metal battery particularly significant Influence.Replace traditional carbonates liquid electrolyte using ionic liquid at room temperature, lithium metal electricity can be effectively reduced The problem that pond is inflammable and explosive and flatulence is serious.Meanwhile ionic liquid at room temperature can also reach and conventional carbonate class electrolysis liquid phase When ionic conductivity and electrochemical stability window.On the one hand double salt introduce largely stable electrolyte and lithium metal On the other hand interface is also greatly improved the ion transport capability of solid electrolyte interface, so that lithium metal battery is with excellent Different overall performance.

Traditional lithium-ion battery electrolytes mostly use carbonates as solvent, are applied directly in lithium metal battery Problems can be generated.Firstly, lithium anode is reacted with carbonate-based solvent, a large amount of hydrogen and hydrocarbon gas are generated, is caused Battery flatulence.Meanwhile a large amount of side reaction induces a large amount of consumption and the appearance and growth of dendrite lithium of lithium metal, drops significantly The low security performance and cycle performance of battery.Therefore, a kind of novel non-carbonates stable with lithium anode are developed Electrolyte has a very important significance.

Nitrile organic matter is high as a kind of potential window, nonflammable, flash-point is high, liquid journey is wide and is not easy to produce the electrolyte of gas etc. System is expected to the ideal chose as high safety electrolyte.However it can not be formed between nitrile electrolyte and lithium anode effectively SEI film.Therefore it can not be used nitrile material as the main solvent of electrolyte.

For the present invention by introducing a variety of lithium salts in electrolyte system, composition, the lithium ion for regulating and controlling anion in lithium salts are dense Degree could be formed with effect SEI at lithium an- ode interface, and be dissociated nitrile organic matter and lithium salts by high concentration ion limitation It directly contacts, it is hereby achieved that a kind of pair of lithium metal is stable and does not contain the high safety electrolyte of conventional carbonate class solvent. The safe utilization for realizing lithium an- ode is had a very important significance.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the existing technology with it is insufficient, a kind of lithium metal battery is provided and is electrolysed with nitrile Liquid and the lithium metal battery for using the electrolyte.

To achieve the goals above, the present invention is achieved through the following technical solutions:

A kind of lithium metal battery nitrile electrolyte, by least two kinds of lithium salts and at least one consolidating containing cyano functional group Body or liquid reagent composition.

The melting temperature of the lithium metal battery nitrile electrolyte is -10~140 DEG C, and ionic conductivity is 1 × 10-4 ~1 × 10-2S/cm；The concentration of lithium salts is 0.1~5mol/L in the lithium metal battery nitrile electrolyte.

Further, the melting temperature of the lithium metal battery nitrile electrolyte is 0~60 DEG C, and the lithium salts is in electrolyte In concentration be 1~3mol/L.

At least one of described two lithium salts are lithium borate salt, and described two lithium salts are fluorine-containing sulfimide lithium salts or fluorine-containing The combination of one of phosphoric acid lithium salts or hydracid lithium salts and lithium borate salt.

The fluorine-containing sulfimide lithium salts is double fluorine sulfimide lithium (LiFSI), bis trifluoromethyl sulfimide lithium (LiTFSI), double pentafluoroethyl group sulfimide lithium Li (C2F5SO2) 2N, trifluoromethyl pentafluoroethyl group sulfimide lithium Li (CF3SO2) one or more of (C2F5SO2) N.

The fluorine-containing phosphoric acid lithium salts is difluorophosphate (LiPO2F2), four lithium fluophosphates (LiPOF4), lithium hexafluoro phosphate One or more of (LiPF6).

The hydracid lithium salts is one or more of lithium perchlorate LiClO4, lithium bromate LiBrO3, lithium iodate LiIO3.

The lithium borate salt is difluorine oxalic acid boracic acid lithium (LiDFOB), LiBF4 (LiBF4), biethyl diacid lithium borate One or more of (LiBOB).

Described two lithium salts are further the group of double fluorine sulfimide lithiums (LiFSI) and difluorine oxalic acid boracic acid lithium (LiDFOB) Conjunction, the combination of bis trifluoromethyl sulfimide lithium (LiTFSI) and the combination of difluorine oxalic acid boracic acid lithium (LiDFOB), double fluoroforms The combination of base sulfimide lithium (LiTFSI) and biethyl diacid lithium borate (LiBOB), bis trifluoromethyl sulfimide lithium (LiTFSI) with the combination of LiBF4 (LiBF4), double fluorine sulfimide lithiums (LiFSI) and biethyl diacid lithium borate (LiBOB) combination.

The solid containing cyano functional group or liquid reagent are acetonitrile, propionitrile, malononitrile, butyronitrile, succinonitrile, penta Nitrile, glutaronitrile, 2- methylene glutaronitrile, own nitrile, adiponitrile, heptonitrile, pimelic dinitrile, caprylic nitrile, hexamethylene dicyanide, acrylonitrile, butene nitrile, cyanogen Base acrylate, polyacrylonitrile, allyl acetonitrile, hexene nitrile, azodiisobutyronitrile, chlordene tripolyphosphazene, azobisisoheptonitrile, chlordene It is one or more of in three phosphonitrile of ring.

A kind of lithium metal battery, including anode, diaphragm, cathode and above-described lithium metal battery nitrile electrolyte.

The lithium metal battery cathode must contain 0 valence lithium metal, and the lithium metal battery negative electrode material is lithium metal, graphite With mixture, graphite and the silicon-carbon of lithium metal and the mixture of lithium metal, the pre- intercalation materials of li ions of graphite chemical method, graphite with it is SiGeC One of pre- intercalation materials of li ions of method.

The lithium metal battery positive electrode active materials be LiFePO4, cobalt acid lithium, lithium ferric manganese phosphate, LiMn2O4, lithium titanate, One or more of nickel ion doped, nickel-cobalt-manganese ternary material.

The diaphragm that the lithium metal battery uses is fibreglass diaphragm, cellulosic nonwoven fabric film, poly terephthalic acid second One of terephthalate films (PET film), polyimides, polyalkene diaphragm.

The present invention has the advantages that

It 1, is by a kind of price containing cyano functional group the present invention provides a kind of lithium metal battery nitrile electrolyte The cheap liquid or solid reagent easily obtained is mixed to prepare with lithium salts, has simple preparation process, easily operated.It considers Preparation process and cost of material, such method commercialization easy to accomplish.

2, the present invention provides a kind of lithium metal battery nitrile electrolyte, ionic conductivity at room temperature be can achieve With traditional comparable level of carbonates electrolyte, 10 can be reached^-2S cm^-2.The electrification of conventional carbonate class electrolyte Window is learned usually in 4.5V hereinafter, however nitrile electrolyte provided by the present invention can reach the stable electricity of 4.7V at room temperature Chemical window.

3, lithium metal battery nitrile electrolyte provided by the present invention can significantly improve the safety of lithium metal battery It can be with long circulating performance.What it is using nitrile electrolyte assembling is the battery of Soft Roll in 30 weeks big face amount using lithium anode (4mA h cm^-2) still have after circulation 95% or so capacity retention ratio, compared to the Soft Roll of conventional carbonate class electrolyte assembling Capacity retention ratio (55%) it is much greater.Meanwhile it also may be implemented in lithium/lithium Symmetrical cells big more than 10000 hours Face amount (4mA h cm^-2) circulation.Even if by cobalt acid lithium/lithium half-cell under the high voltage of 3-4.7V 1C circulation, still After recycling 74% capacity retention ratio so may be implemented 500 times.

4, the lithium metal soft-package battery proposed by the invention assembled using such nitrile electrolyte is carried out after pre-activate There is not the case where battery flatulence in subsequent long circulating in air suction process.The Soft Roll assembled using carbonates electrolyte Battery equally carries out air suction process after pre-activate.However, still occurring the case where Soft Roll flatulence in subsequent long circulating. Therefore, which can effectively inhibit soft-package battery to produce gas, improve the circulation of lithium metal battery Security performance.

Specific embodiment

Below by exemplary embodiment, the present invention will be further elaborated；But the scope of the present invention should not limit to In the range of embodiment, any variation or change without departing from present subject matter can be understood by the person skilled in the art, All within protection scope of the present invention.

Comparative example

Under inert gas atmosphere protection, EC/DMC (V:V=1:1) 5mL is pipetted with liquid-transfering gun, is weighed with assay balance LiTFSI powder 1.44g is stirred at room temperature in inert gas and makes it dissolve in 10mL sample bottle, obtains transparent uniform electrolysis Liquid.

Embodiment 1

Under inert gas atmosphere protection, malononitrile solid 5g, LiFSI powder 3g, LiTFSI powder is weighed with assay balance Last 0.25g is in 10mL sample bottle, and stirring and dissolving, obtains transparent uniform solution at room temperature.

Embodiment 2

Under inert gas atmosphere protection, malononitrile solid 5g, LiTFSI powder 3g, LiClO are weighed with assay balance₄Powder For last 0.25g in 10mL sample bottle, stirring and dissolving under the conditions of 0 DEG C obtains transparent uniform solution.

Embodiment 3

Under inert gas atmosphere protection, malononitrile solid 5g, LiFSI powder 1.5g is weighed with assay balance,

For LiBOB powder 1g in 10mL sample bottle, stirring and dissolving under the conditions of 60 DEG C obtains transparent uniform solution.

Embodiment 4

Under inert gas atmosphere protection, malononitrile solid 5g, LiBF are weighed with assay balance₄Powder 2g, LiPF₆Powder 1.5g is in 10mL sample bottle, stirring and dissolving under the conditions of -10 DEG C, obtains transparent uniform solution.

Embodiment 5

Under inert gas atmosphere protection, polyacrylonitrile solid 10g, LiDFOB powder 4g, LiBF are weighed with assay balance₄ For powder 2g in 20mL sample bottle, stirring and dissolving under the conditions of 100 DEG C obtains transparent uniform solution.

Embodiment 6

Under inert gas atmosphere protection, polyacrylonitrile solid 10g, LiFSI powder 5g, LiTFSI are weighed with assay balance For powder 1g in 20mL sample bottle, stirring and dissolving under the conditions of 140 DEG C obtains transparent uniform solution.

Embodiment 7

Under inert gas atmosphere protection, polyacrylonitrile solid 10g, LiBOB powder 6g, LiDFOB are weighed with assay balance For powder 0.5g in 20mL sample bottle, stirring and dissolving under the conditions of 60 DEG C obtains transparent uniform solution.

Embodiment 8

Under inert gas atmosphere protection, succinonitrile solid 5g, LiBF are weighed with assay balance₄Powder 3g, LiPF₆Powder For 0.05g in 10mL sample bottle, stirring and dissolving under the conditions of 40 DEG C obtains transparent uniform solution.

Embodiment 9

Under inert gas atmosphere protection, succinonitrile solid 5g, LiFSI powder 1.5g is weighed with assay balance,

For LiBOB powder 2g in 10mL sample bottle, stirring and dissolving under the conditions of 0 DEG C obtains transparent uniform solution.

Embodiment 10

Under inert gas atmosphere protection, succinonitrile solid 5g, LiDFOB powder 2g, LiBF are weighed with assay balance₄Powder For last 1g in 10mL sample bottle, stirring and dissolving under the conditions of 80 DEG C obtains transparent uniform solution.

Embodiment 11

Under inert gas atmosphere protection, succinonitrile solid 5g, LiDFOB powder 1g, Li are weighed with assay balance (C₂F₅SO₂)₂For N powder 4g in 10mL sample bottle, stirring and dissolving under the conditions of 60 DEG C obtains transparent uniform solution.

Embodiment 12

Under inert gas atmosphere protection, succinonitrile solid 5g, LiBF are weighed with assay balance₄Powder 1g, LiPO₂F₂Powder For last 4g in 10mL sample bottle, stirring and dissolving under the conditions of 40 DEG C obtains transparent uniform solution.

Embodiment 13

Under inert gas atmosphere protection, heptonitrile and each 2.5g of caprylic nitrile solid, LiFSI powder are weighed with assay balance For 1.5g, LiDFOB powder 2g in 10mL sample bottle, stirring and dissolving under the conditions of 60 DEG C obtains transparent uniform solution.

Embodiment 14

Under inert gas atmosphere protection, azobisisoheptonitrile 5g, LiBF are weighed with assay balance₄Powder 3g, LiPF₆Powder For last 1.5g in 10mL sample bottle, stirring and dissolving under the conditions of 40 DEG C obtains transparent uniform solution.

Embodiment 15

Under inert gas atmosphere protection, chlordene tripolyphosphazene 5g, LiDFOB powder 1g, Li are weighed with assay balance (C₂F₅SO₂)₂For N powder 4g in 10mL sample bottle, stirring and dissolving under the conditions of 60 DEG C obtains transparent uniform solution.

Embodiment 16

Under inert gas atmosphere protection, hexachlorocyclotriph,sphazene 5g, LiDFOB powder 1g, Li are weighed with assay balance (C₂F₅SO₂)₂For N powder 4g in 10mL sample bottle, stirring and dissolving under the conditions of 60 DEG C obtains transparent uniform solution.

Embodiment 17

Under inert gas atmosphere protection, acrylonitrile 5g, LiBF are weighed with assay balance₄Powder 1g, LiPO₂F₂Powder 4g In 10mL sample bottle, stirring and dissolving under the conditions of 40 DEG C obtains transparent uniform solution.

Embodiment 18

Under inert gas atmosphere protection, butene nitrile 5g, LiBF are weighed with assay balance₄Powder 1g, LiPO₂F₂Powder 4g In 10mL sample bottle, stirring and dissolving under the conditions of 40 DEG C obtains transparent uniform solution.

Embodiment 19

Under inert gas atmosphere protection, cyanacrylate 5g, LiDFOB powder 1g, Li are weighed with assay balance (C₂F₅SO₂)₂For N powder 4g in 10mL sample bottle, stirring and dissolving under the conditions of 25 DEG C obtains transparent uniform solution.

Embodiment 20

Under inert gas atmosphere protection, succinonitrile 10g, LiTFSI powder 6g, LiDFOB powder are weighed with assay balance For 0.5g in 20mL sample bottle, stirring and dissolving under the conditions of 60 DEG C obtains transparent uniform solution.

Pole piece preparation and battery assembly:

(1) prepared by positive plate: with cobalt acid lithium (LiCoO₂) for, LiCoO is weighed according to mass ratio 93:4:3₂Powder, conduction Carbon black, Kynoar (PVDF) are added solvent N-methyl pyrilidone (NMP), so that PVDF is relative to NMP mass fraction 6%, it is uniformly mixing to obtain slurry at room temperature.By obtained slurry according to 230g/m²Surface density be coated on aluminium foil, Zhi Hou 2h is placed in 60 DEG C of blast driers, is transferred in 120 DEG C of vacuum drying ovens and dries for 24 hours, roll-in is then carried out, cuts to obtain anode Piece.

(2) capacity retention ratio test: assembling cobalt acid lithium soft-package battery, successively into Soft Roll be packed into lithium anode, diaphragm, Lithium cobaltate cathode injects the nitrile electrolyte prepared in comparative example and embodiment 1-19, uses heat sealing machine in an inert atmosphere Sealing.Air suction process is carried out to battery after pre- circulation, at room temperature after charge and discharge 30 times circulations, the circulation volume for testing battery is protected Holdup.Assemble LiCoO₂| Li half-cell, electrolyte is using the nitrile electrolyte prepared in embodiment 20.In filling for 3.0-4.7V In discharge voltage range, at room temperature after charge and discharge 500 times circulations, the circulation volume conservation rate of battery is tested.

(3) electrochemical stability window is tested: assembling LIR2032 type button cell, assembling sequence are successively negative from top to bottom Pole shell, metal lithium sheet, diaphragm, steel disc, spring leaf, anode cover inject the nitrile electrolysis prepared in comparative example and embodiment 1-19 Liquid is sealed with sealing machine in an inert atmosphere.It stands at room temperature and the survey of room temperature electrochemical stability window is carried out to battery afterwards for 24 hours Examination.

(4) ionic conductivity test: assembling LIR2032 type button cell, assembling sequence be followed successively by from top to bottom negative electrode casing, Steel disc, diaphragm, steel disc, spring leaf, anode cover inject the nitrile electrolyte prepared in comparative example and embodiment 1-19, in inertia It is sealed under gaseous environment with sealing machine.It stands at room temperature and room-temperature ion conductivity test is carried out to battery afterwards for 24 hours.

(5) cobalt acid lithium soft-package battery flatulence degree is tested: the thickness in test (2) before soft-package battery constant current charge-discharge cycle.So Afterwards by battery in 50mA g^-1Under conditions of constant current charge and discharge 30 weeks, test its thickness respectively again.

At room temperature, 1C circulation under the high voltage of 3-4.7V may be implemented 500 times 74% after recycling embodiment 20 Capacity retention ratio.

By the capacity retention ratio of tested battery, room temperature electrochemical stability window, room temperature in comparative example and embodiment 1-19 The thickness swelling of ionic conductivity and battery is listed in table 1, as a result as follows:

The capacity retention ratio of 1 comparative example of table and embodiment 1-19 battery, room temperature electrochemical stability window, room-temperature ion are conductive The thickness swelling of rate and battery

Claims

1. A nitrile electrolyte for lithium metal batteries, characterized in that: the lithium metal battery electrolyte is composed of at least two kinds of lithium salts and at least one solid or liquid reagent containing a cyano functional group.

2 . The nitrile-based electrolyte for lithium metal batteries according to claim 1 , wherein the melting temperature of the nitrile-based electrolyte for lithium metal batteries is -10 to 140° C., and the ionic conductivity is 1×10 ^{− 4} to 1×10 ^-2 S/cm; the concentration of the lithium salt in the electrolyte is 0.1 to 5 mol/L.

3 . The nitrile-based electrolyte for lithium metal batteries according to claim 2 , wherein the melting temperature of the nitrile-based electrolyte for lithium metal batteries is 0 to 60° C., and the concentration of the lithium salt in the electrolyte is 0 to 60° C. 4 . The concentration is 1～3mol/L.

4. The nitrile electrolyte for lithium metal batteries according to claim 1, wherein the solid or liquid reagent containing a cyano functional group is acetonitrile, propionitrile, malononitrile, butyronitrile, succinonitrile, Valeronitrile, Glutaronitrile, 2-Methyleneglutaronitrile, Capronitrile, Adiponitrile, Heptanenitrile, Pimeliconitrile, Caprylonitrile, Suberonitrile, Acrylonitrile, Butenenitrile, Cyanoacrylate, Poly One or more of acrylonitrile, pentenenitrile, hexenenitrile, azobisisobutyronitrile, hexachlorotripolyphosphazene, azobisisoheptanenitrile, and hexachlorocyclotriphosphazene.

5 . The nitrile electrolyte for lithium metal batteries according to claim 1 , wherein at least one of the at least two lithium salts is a lithium borate salt. 6 .

6 . The nitrile electrolyte for lithium metal batteries according to claim 1 , wherein at least one of the at least two lithium salts is a fluorine-containing sulfonimide lithium salt, a fluorine-containing lithium phosphate salt, a halogen One or more of lithium salts.

7 . The nitrile electrolyte for lithium metal batteries according to claim 5 , wherein the at least two lithium salts further comprise fluorine-containing sulfonimide lithium salt, fluorine-containing lithium phosphate salt, and lithium halide acid. 8 . a type of salt.

8 . The nitrile electrolyte for lithium metal batteries according to claim 6 or 7 , wherein the fluorine-containing sulfonimide lithium salt is lithium bisfluorosulfonimide (LiFSI), bis-tris Lithium fluoromethylsulfonimide (LiTFSI), lithium bis-pentafluoroethylimide Li(C ₂ F ₅ SO ₂ ) ₂ N, lithium trifluoromethyl pentafluoroethylimide Li(CF One or more of ₃ SO ₂ )(C ₂ F ₅ SO ₂ )N.

9. The nitrile electrolyte for a lithium metal battery according to claim 6 or 7, wherein the fluorine-containing lithium phosphate is lithium difluorophosphate (LiPO ₂ F ₂ ), lithium tetrafluorophosphate ( One or more of LiPOF ₄ ) and lithium hexafluorophosphate (LiPF ₆ ).

10. The nitrile electrolyte for a lithium metal battery according to claim 6 or 7, wherein the lithium halide salt is lithium perchlorate LiClO ₄ , lithium bromate LiBrO ₃ , lithium iodate LiIO One or more of ₃ .

11 . The nitrile electrolyte for lithium metal batteries according to claim 5 , wherein the lithium borate salt is lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4 ), diethylene di One or more of lithium borate (LiBOB).

12. The nitrile electrolyte for a lithium metal battery according to claim 5 or 7, wherein the two lithium salts are lithium bisfluorosulfonimide (LiFSI) and lithium difluorooxalate borate ( LiDFOB), lithium bis-trifluoromethanesulfonimide (LiTFSI) and lithium difluorooxalate borate (LiDFOB), lithium bis-trifluoromethanesulfonimide (LiTFSI) and bisoxalic acid The combination of lithium borate (LiBOB), lithium bistrifluoromethanesulfonimide (LiTFSI) and lithium tetrafluoroborate (LiBF4), lithium bisfluorosulfonimide (LiFSI) and lithium bisoxalatoborate ( LiBOB).

13. A lithium metal battery, comprising a positive electrode, a separator, a negative electrode and the nitrile electrolyte for a lithium metal battery according to any one of claims 1-12.

14. The lithium metal battery according to claim 13, wherein the negative electrode of the lithium metal battery contains 0-valent lithium metal, and the negative electrode material of the lithium metal battery is lithium metal, a mixture of graphite and lithium metal, graphite It is one of the mixture with silicon carbon and lithium metal, graphite chemical method pre-insertion lithium material, graphite and silicon carbon chemical method pre-insertion lithium material.