WO2012163186A1

WO2012163186A1 - Lithium phosphorus secondary battery

Info

Publication number: WO2012163186A1
Application number: PCT/CN2012/074072
Authority: WO
Inventors: 高学平; 叶世海; 王永龙; 李国然; 赵倩倩; 李国春
Original assignee: 南开大学
Priority date: 2011-06-02
Filing date: 2012-04-16
Publication date: 2012-12-06
Also published as: CN102244288B; CN102244288A

Abstract

The present invention relates to a lithium phosphorus secondary battery. It is a new secondary battery system with high specific energy, consisting of a phosphorus material as the positive electrode active substance, metal lithium or a lithium metal alloy as the negative electrode material and an organic electrolyte system. The positive electrode contains phosphorus element as an active substance, and the phosphorus material is elementary phosphorus, Li_xP_y(1 ≤ x/y ≤ 3) or other polymeric phosphorus compounds. The positive (active) material is a phosphorus material, a composite of a phosphorus material and a carbon material, or a composite of a phosphorus material and a conducting polymer. The carbon material is natural graphite, artificial graphite, carbon nanotube, graphene, acetylene black, carbon black or active carbon; and the conducting polymer is polyaniline, polypyrrole, or polythiophene. The preparation of the battery has low costs, a simple technical process, a large application value, and is suitable for industrial production, and in particular, the present invention has features, such as high charging-discharging specific energy, and a stable electrochemical cycle.

Description

Lithium phosphorus secondary battery

Technical field

The present invention relates to the manufacture of secondary batteries, and more particularly to a lithium phosphorus secondary battery. It is a novel secondary battery system having a high specific energy, which is composed of a material containing a phosphorus element as a positive electrode active material, a lithium metal or a lithium metal alloy as a negative electrode material and an organic electrolyte system. Background technique

At present, the energy of commercial lithium ion secondary batteries is generally low, which limits the wide application of lithium ion batteries in the field of electric vehicles. The development of new battery materials with high specific capacity is the main goal of battery development at present and in the future, that is, meeting the needs of high-performance and large-capacity secondary batteries in the field of electronic and communication equipment, and is also an urgent need for the development of electric vehicles. The energy density of a lithium ion battery is generally limited by the material of the positive electrode active material. The positive electrode material of the lithium ion battery is mostly single electron or less than a single electron embedded reaction material, thereby causing the positive electrode material to have a small specific capacity. At present, commercial cathode materials mainly include LiCo0 ₂ (120-140 mAh/g), LiNi0 ₂ (150-190 mAh/g), LiMn ₂ 0 ₄ (100-120 mAh/g), LiFeP0 ₄ (150-160 mAh/g). ) and materials such as ternary LiNi Co Mn^C (155-165 mAh/g). The maximum actual discharge capacity of these lithium ion battery cathode materials is difficult to exceed 200 mAh/g. Among the organic electrolytes, the small molecular weight non-metal active material has a high oxidation-reduction potential and a multi-electron reaction characteristic, and thus has a large theoretical specific capacity, and is very suitable as a positive electrode material for a lithium ion battery. For example, elemental sulfur has two electronic reaction characteristics, its theoretical specific capacity is as high as 1675 mAh/g, and exhibits excellent high specific capacity characteristics in actual lithium-sulfur battery systems. Elemental phosphorus has a low molecular weight and a three-electron reaction characteristic, and its theoretical capacity is 2596 mAh/g, which is 30% higher than the theoretical specific capacity of elemental sulfur. If elemental phosphorus, Li _x P _y (l≤x/y≤3) or other polyphosphide is used as the positive electrode active material of the secondary battery, and a lithium metal or lithium metal alloy constitutes a novel secondary battery system, Has a higher energy density. Summary of the invention

An object of the present invention is to provide a novel lithium phosphorus secondary battery comprising a material containing a phosphorus element as a positive electrode active material, a lithium metal or a lithium metal alloy as a negative electrode active material, having a high charge-discharge ratio energy and electricity. The chemical cycle is stable and can meet the needs of large-capacity and high-performance secondary batteries in the field of electronic and communication equipment. The invention is simple to manufacture and suitable for industrial production.

The lithium phosphorus secondary battery provided by the present invention includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode is made of a material containing a phosphorus element including elemental phosphorus, Li _x P _y (l≤x/y≤3) or a polyphosphide. The positive (active) material includes a phosphor material, a phosphor material and a carbon material composite or a composite of a phosphorus material and a conductive polymer.

The carbon material includes natural graphite, artificial graphite, carbon nanotubes, graphene, acetylene black, carbon black or activated carbon; and the conductive polymer includes polyaniline, polypyrrole or polythiophene.

The mass ratio of the phosphorus to the carbon raw material in the phosphorus material and the carbon material composite is 1:4-4:1.

The mass ratio of the phosphorus to the raw material of the polymer monomer in the composite of the phosphorus material and the conductive polymer is 1:4-4:1. The electrolyte includes an electrolyte lithium salt and a single organic solvent or a mixed organic solvent or ionic liquid having at least two components.

The electrolyte lithium salt includes LiC10 ₄ , LiPF ₆ , LiTFSK LiBF ₄ or LiAsF ₆ and the like.

The organic solvent includes acetonitrile, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, dipropyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethoxy An ionic liquid of ethane, diethoxyethane, dioxolane, ethylene glycol dimethyl ether, tetraglyme, tetrahydrofuran, and imidazoles, or quaternary ammonium salts.

The preparation method of the phosphor material and the carbon material composite cathode material according to the present invention is that the phosphorus material and the carbon material are ball milled in a ball mill tank for l-10h, and the rotation speed is set to 200-400 rev/min to obtain a porous carbon-supported phosphorus. Composite cathode material; or elemental phosphorus and carbon material in an inert gas protection reaction tank, the temperature is raised to 400-500 ° C, constant temperature 2-6h, cooling to 300~26 (TC, constant temperature 2-40 h, get Carbon-supported phosphorus composite cathode material.

The method for preparing a composite positive electrode material of phosphorus and a conductive polymer according to the present invention is to ball-mill the phosphor material and the polymer in a ball mill tank for l-10h, and the rotation speed is set to 200-400 rpm to obtain a polymer. Supported phosphorus composite cathode material; or

Disperse the phosphorus material in water and ethanol or a mixed solvent of water and acetone, then introduce the oxidant ferric chloride or ammonium persulfate and hydrochloric acid, stir to dissolve, and then ultrasonically disperse the phosphor material for 0.5-2 h, then add the polymer. The monomer, which is to be polymerized, centrifuged, washed with water or ethanol, to obtain a conductive polymer-supported phosphorus composite positive electrode material; the polymer monomer is aniline, pyrrole or thiophene.

The lithium phosphorus secondary battery of the invention is prepared by supporting a phosphor material active material on a conductive material (the carbon material is directly supported on or compounded with the polymer) to form a positive electrode active material, and then a conductive agent and a binder PTFE. It is mixed with a solvent to form a slurry, and is formed by rolling to form a positive electrode sheet. The positive electrode sheet, the lithium metal or lithium metal alloy negative electrode sheet, the electrolytic solution, and the separator were assembled in a usual manner.

The invention provides a novel lithium phosphorus secondary battery, which has low preparation cost, simple process flow and great application value, for example, electronic and communication equipment fields and electric vehicles. The invention is suitable for industrial production, special It has the characteristics of high charge-discharge ratio energy and stable electrochemical cycle. DRAWINGS

Figure 1 Example 1 Lithium-phosphorus battery charge and discharge curve.

Figure 2 Example 2 Lithium-phosphorus battery charge and discharge curve.

Figure 3 Example 3 Lithium-phosphorus battery charge and discharge curve. Specific lung

The essential features and significant effects of the present invention can be embodied by the following examples, but they are not intended to limit the invention in any way.

Example 1

Preparation of positive electrode material and positive electrode:

5 g of red phosphorus powder was mixed with 5 g of acetylene black powder, the mass ratio of the ball was 20:1, the rotation speed of the ball mill was 300 rpm, and the ball was mechanically milled for 4 hours to obtain phosphorus of red phosphorus powder and acetylene black having an average particle diameter of 1 μm. Carbon composite cathode material. Then mixed with the binder polytetrafluoroethylene (phosphorus: conductive agent: binder weight ratio of 75: 15: 10), then added anhydrous ethanol to make a slurry, crushed into a positive electrode sheet, at 60 ° C Dry and spare. The positive electrode sheet has a diameter of 8 mm and a thickness of 0.1 mm.

The preparation of the positive electrode material can also select the following steps:

Elemental red phosphorus (dark red, amorphous powder) having an average particle diameter of 20 μm and conductive carbon black (pore size distribution of 0.5 to 50 nm, pore volume of 0.8 cm ³ /g, specific surface area of 800 cm ² /g) in terms of mass ratio Weighed in a ratio of 1:1, placed in an inert gas argon-protected reaction tank, heated to 500 ° C, kept at a constant temperature for 6 h, cooled to 260 ° C, and kept at a constant temperature for 10 h to obtain a carbon-supported phosphorus composite positive electrode material.

Preparation of the negative electrode: The negative electrode was made of a metal lithium plate having a diameter of 8 mm and a thickness of 1.00 mm. Use a knife to scrape off the oxide layer on the surface and set aside.

Electrolyte solution: electrolyte solution using propylene carbonate solution of LiPF ethyl carbonate _6, LiPF ₆ at a concentration of lmol / 1, ethyl carbonate, propylene carbonate and a volume ratio of 1: 1.

Battery assembly: The battery assembly was carried out in a waterless oxygen-free operation box with a diaphragm of _C eUgu _ar d2600 diaphragm paper and a thickness of 0.1 mm. The spare lithium metal negative electrode sheet is placed on the conductive current collector copper foil and the bottom of the battery stainless steel mold, the copper foil is in contact with the stainless steel, and then the _Ce llguard 2600 separator paper having a thickness of 0.1 mm is placed on the metal lithium negative electrode sheet, and the standby positive electrode is placed. Place the sheet on the septum paper, add 3 drops of the electrolyte solution with a dropper, press and screw the stainless steel jacket with a stainless steel positive electrode column, and seal the jacket gap with paraffin. The battery has a cylindrical shape. Battery capacity test: The assembled battery adopts voltage controlled constant current charge and discharge mode. The charge and discharge current is 20mA/g, and the charge and discharge voltage ranges from 1.0 to 4.3V. The test results obtained are shown in Figure 1.

The first discharge of the battery has a specific capacity of about 1800 mAh/g at a voltage of 1.0 V or more. When the charge cut-off voltage is 4.3 V, the charge specific capacity is also about 1800 mAh/g, which reflects the characteristics of the high specific energy of the pity/lithium battery. . Example 2

Preparation of positive electrode material and positive electrode: Mixing red phosphorus powder (dark red, amorphous powder) with an average particle diameter of 20 μm with conductive carbon black powder (pence: conductive carbon black weight ratio of 1:1), ball mass The ratio is 20:1, the ball mill rotates at 300 rpm, and the machine is ball milled for 4 hours to obtain a phosphorus-carbon composite positive electrode material. The phosphorus carbon composite is mixed with the conductive agent acetylene black and the binder polytetrafluoroethylene (phosphorus carbon composite: conductive agent: binder weight ratio is 85:8:7), and then added with anhydrous ethanol to prepare a slurry. Shape, crushed into a positive electrode for use.

For the preparation of the negative electrode, see Example 1

Electrolyte solution of propylene carbonate using ethyl carbonate of LiBF _4, LiBF ₄ at a concentration of lmol / l, propylene carbonate and diethyl carbonate in a volume ratio 1: 1

See Figure 1 for battery assembly.

Battery capacity test

The assembled battery uses a voltage controlled constant current charge and discharge mode with a charge and discharge current of 20 mA/g and a charge and discharge voltage range of 1.0-4.3V. The test results obtained are shown in Figure 2.

The first discharge of the battery has a specific capacity of about 1700 mAh/g at a voltage of 1.0 V or more. It has an obvious voltage platform at 2.4 V, which embodies the characteristics of high specific energy of the lithium-phosphorus battery. Example 3

Preparation of positive electrode

0.5 g of an elemental red phosphorus having an average particle diameter of 20 μm (dark red, amorphous powder) was dispersed in 50 ml of a mixed solvent of water and ethanol (volume ratio of 1:1), and then an oxidizing agent 0.2 g of ferric chloride hexahydrate was introduced. 1ml of concentrated hydrochloric acid, stir to dissolve, then ultrasonically 0.5h to make the elemental phosphorus evenly dispersed, then add 0.5g of aniline monomer, to be polymerized, centrifuged, washed with water, anhydrous ethanol, then get conductive polymer polyaniline-loaded phosphorus composite Cathode material.

The phosphorus conductive polymer composite is mixed with the conductive agent acetylene black and the binder polytetrafluoroethylene (phosphorus conductive polymer composite: conductive agent: binder weight ratio is 80:12:8), and then anhydrous The ethanol was slurried and rolled into a positive electrode for use.

For the preparation of the negative electrode, see Example 1. The electrolyte of the electrolyte was LiTFSI, and the solvent was 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME), and the concentration of LiTFSI was 1 mol/l.

See Example 1 for battery assembly.

Battery capacity test

The assembled battery uses a voltage-controlled constant current charge and discharge mode with a charge and discharge current of 50 mA/g and a charge and discharge voltage range of 1.0-4.3V. The test results obtained are shown in Figure 3.

The first discharge of the battery has a specific capacity of about 1800 mAh/g at a voltage of 1.5V or more. There is an obvious voltage platform at 1.3V, which reflects the high specific energy of the lithium-phosphorus battery. According to the analysis of the results of the three examples, the initial discharge specific capacity of the new phosphorus-lithium battery system can reach the specific capacity of 1000 mAh/g or more (based on phosphorus as active material), and the performance of the discharge platform is good. Reflecting the obvious high specific energy characteristics, it is a new secondary battery system with great application potential, which can be used in the field of electronic and communication equipment and electric vehicles.

Claims

Claim

A lithium-phosphorus secondary battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that:

The positive electrode material is an active material containing a phosphorus element including elemental phosphorus, Li _x P _y 3 ) or a polyphosphide;

The negative electrode material is metallic lithium or a lithium metal alloy.

2. The lithium phosphorus secondary battery according to claim 1, wherein the positive electrode material comprises a phosphor material, a phosphor material and a carbon material composite, or a composite of a phosphorus material and a conductive polymer.

The lithium phosphorus secondary battery according to claim 2, wherein the carbon material comprises natural graphite, artificial graphite, carbon nanotubes, graphene, acetylene black, carbon black or activated carbon.

The lithium phosphorus secondary battery according to claim 2, wherein said conductive polymer comprises polyaniline, polypyrrole or polythiophene.

The lithium phosphorus secondary battery according to claim 2, wherein a mass ratio of the phosphorus to the carbon raw material in the phosphor material and the carbon material composite is 1:4 to 4:1.

6. The lithium phosphorus secondary battery according to claim 2, wherein a mass ratio of the phosphorus to the raw material of the polymer monomer in the composite of the phosphor material and the conductive polymer is 1:4-4: 1.

The lithium phosphorus secondary battery according to claim 1, wherein the electrolyte solution comprises an electrolyte lithium salt and a single organic solvent or a mixed organic solvent or an ionic liquid having at least two components.

The lithium phosphorus secondary battery according to claim 7, wherein the electrolyte lithium salt comprises LiC10 ₄ , LiPF ₆ , LiTFSI, LiBF ₄ or LiAsF ₆ .

The lithium phosphorus secondary battery according to claim 7, wherein the organic solvent comprises acetonitrile, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, dipropyl carbonate. , propylene carbonate, ethylene carbonate, vinylene carbonate, dimethoxyethane, diethoxyethane, dioxolane, ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran , and ionic liquids of imidazoles, or quaternary ammonium salts.

The lithium phosphorus secondary battery according to claim 7, wherein the organic solvent is a mixed solution of propylene carbonate and ethyl carbonate, or 1,3-dioxolane and ethylene glycol A mixed solution of methyl ether.

The lithium phosphorus secondary battery according to claim 7, wherein the electrolyte lithium salt is LiBF ₄ or LiPF ₆ .

12. A lithium phosphorus secondary battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that:

The cathode material is a composite of a phosphorus material and a conductive carbon material, or a composite of a phosphorus material and a conductive polymer; the carbon material is graphite, carbon nanotubes, graphene, acetylene black, carbon black or activated carbon; The conductive polymer package Including polyaniline, polypyrrole or polythiophene;

The anode material is a metal lithium or a lithium metal alloy;

The electrolyte is a solution of LiBF ₄ , propylene carbonate and ethyl carbonate of LiPF ₆ ; or a mixed solution of 1,3-dioxolane and ethylene glycol dimethyl ether of LiTFSI.

The lithium phosphorus secondary battery according to claim 12, wherein: the mass ratio of phosphorus to carbon raw material in the phosphorus-conducting carbon material composite is 1:4-4:1; The mass ratio of the phosphorus to the raw material of the polymer monomer in the composite with the conductive polymer is 1:4 to 4:1.

The lithium-phosphorus secondary battery according to claim 2, wherein: the phosphor material and the carbon material composite positive electrode material are prepared by ball-milling elemental phosphorus and carbon materials in a ball mill tank for 10-10 hours. , the rotation speed is 200-400 rev / min, and the porous carbon-supported phosphorus composite cathode material is obtained;

The lithium phosphorus secondary battery according to claim 2, wherein the phosphor material and the carbon material composite positive electrode material are prepared by placing an elemental phosphorus and a carbon material in an inert gas-protected reaction tank. In the middle, the temperature is raised to 400-500 °C, the temperature is 2-6h, the temperature is lowered to 260 °C, and the temperature is 2_40h, and the carbon-supported phosphorus composite cathode material is obtained.

The lithium phosphorus secondary battery according to claim 2, wherein the composite material of the phosphorus and the conductive polymer is prepared by ball milling the elemental phosphorus and the polymer in a ball mill tank. 10h, the rotation speed is 200-400 rpm, and the polymer-supported phosphorus composite cathode material is obtained.

The lithium phosphorus secondary battery according to claim 2, wherein the composite material of the phosphorus and the conductive polymer is prepared by dispersing elemental phosphorus in water and ethanol or a mixed solvent of water and acetone. Then, the oxidant ferric chloride or ammonium persulfate and hydrochloric acid are introduced, stirred to dissolve, and then the elemental phosphorus is uniformly dispersed by ultrasonication for 0.5-2 h, then the polymer monomer is added, polymerized, centrifuged, washed with water, ethanol, That is, a conductive polymer-supported phosphorus composite positive electrode material is obtained; the polymer monomer is aniline, pyrrole or thiophene.

18. Use of a lithium phosphorus secondary battery according to any of claims 1 - 13, characterized by a power supply for the field of electronics and communication equipment and electric vehicles.