CN100413139C - A lithium secondary battery using boride as negative electrode material - Google Patents

Abstract

The invention belongs to the technical field of high-energy batteries and provides a lithium secondary battery using borides as negative electrode materials. The lithium secondary battery provided by the present invention is composed of a negative electrode, a positive electrode, a diaphragm, an electrolyte or a polymer electrolyte. The positive electrode and the negative electrode are respectively coated on a current collector and connected to both ends of a mutually insulated battery case through the current collector. The negative electrode is composed of boride, binder and conductive agent, and the active material of the negative electrode is boride. The chemical composition of the boride is M _a B _b O _c , wherein M is selected from one or more of Co, Al, Zr, V, Cr, Ni, Fe, Ti, Cu, Zn, Nd, Mo, Ag, Mg species; 1≤a≤4, 0≤b≤1, 0≤c≤4; the structure of boride is crystalline or amorphous. The lithium secondary battery of the invention has high capacity, no pollution to the environment, safe use, and is suitable for various small mobile electronic devices.

Description

A lithium secondary battery using boride as negative electrode material

technical field

The invention belongs to the technical field of high-energy batteries, in particular to the technical field of lithium secondary batteries, and provides a lithium secondary battery using metal borides as negative electrode materials.

technical background

At present, high-energy secondary battery technology is developing rapidly, and it will occupy an important position in the future energy structure no matter as a "replacement technology" or a "transition technology" (Review, Selected Chemical Power Sources, Wuhan University Press, Wuhan, 2005); and lithium secondary batteries are important members of high-energy secondary batteries. In order to continue to improve the energy density and power density of lithium secondary batteries, it is very important to develop high-performance electrode materials.

Because metallic lithium has a high energy density of 3830mAh/g, it was first used as a negative electrode material for lithium secondary batteries, but part of the lithium dendrites formed in the cycle will pierce the separator and cause a soft short circuit, causing safety problems (B.Scrosati . Lithium Rocking Chair Batteries: An Old Concept?. J. Electrochem. Soc, 1992, 139: 2776-2780). When initially searching for anode materials to replace metallic lithium, people naturally chose lithium alloys. Because the lithium alloy negative electrode avoids the growth of lithium dendrites and improves the safety of the battery, it has attracted widespread attention from researchers; however, it often undergoes large volume and shape changes during repeated cycles, and the electrode materials gradually pulverize and fail. The alloy structure is destroyed. At present, the theoretical lithium intercalation capacity of graphite-based carbon materials widely used in commercial lithium secondary batteries is 372mAh/g, which is difficult to meet people's increasing demand for high-energy secondary batteries; while some oxides, sulfides, nano-metals, metals Alloys, nano-carbon materials, etc. have been studied as anode materials for lithium secondary batteries, but there is still a considerable distance from commercialization. Our recent research has found that some borides can reversibly intercalate and delithiate lithium, and their lithium intercalation capacity exceeds the theoretical lithium intercalation capacity of graphitic carbon materials, which can be used as a new class of anode materials for lithium secondary batteries.

Contents of the invention

The object of the present invention is to provide a lithium secondary battery using metal boride as negative electrode material. The preparation method of the metal boride negative electrode material of the lithium secondary battery is diverse and flexible, the preparation process is simple and quick, and has high electrochemical activity, so the lithium secondary battery can achieve a high capacity.

In order to achieve the above object, the lithium secondary battery provided by the present invention uses metal boride as the negative electrode material and comprises negative pole, positive pole, separator, electrolyte or polymer electrolyte in composition; the positive pole contains lithium-containing transition metal oxide , or lithium-containing phosphate, or lithium metal; the positive electrode and the negative electrode are separated by a separator soaked in electrolyte or a polymer electrolyte; the positive active material and the negative active material are respectively coated on the current collector, and passed through the current collector The poles are connected to both ends of the mutually insulated battery case; the negative pole is composed of metal borides, binders and conductive agents, and the negative active material used is metal borides.

The chemical composition of the metal boride used in the lithium secondary battery with the metal boride as the negative electrode material provided by the invention is _Ma B _b O _c ; wherein M is selected from Co, Al, Zr, V, Cr, Ni, Fe , one or more of Ti, Cu, Zn, Nd, Mo, Ag, Mg;

In the metal borides, 1≤a≤4, 0.04≤b≤1, 0≤c≤4;

The structural form of the metal boride is crystalline or amorphous;

The preparation process of the metal boride is simple and diverse, and can be synthesized by a solution method, a roasting method, a ball milling method, a reduction method and a precipitation method.

In the lithium secondary battery using metal boride as the negative electrode material provided by the present invention, the binder used is selected from polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, methylcellulose, polymethacrylate, One or more of polyvinyl alcohol, vinylidene fluoride-hexafluoropropylene copolymer;

The conductive agent used is selected from one or more of acetylene black, graphite, mesocarbon microspheres, metal powder, and alloy powder;

When the metal boride used has good enough electrical conductivity, no conductive agent can be used in the negative electrode;

The negative current collector used is one of metal mesh, metal foil, carbon cloth, carbon paper, and nickel foam.

The positive effect that the present invention possesses has:

1. The preparation methods of the metal borides are diverse and flexible, and the preparation process is simple and quick.

2. The metal borides have good compatibility with key components such as separators and electrolytes commonly used in commercial lithium secondary batteries, and can be easily assembled into battery products.

3. The lithium secondary battery provided with the metal boride as the negative electrode material has a high capacity, no pollution to the environment, and is safe and reliable to use.

Description of drawings

Accompanying drawing-be the first three week charge-discharge graphs of the lithium secondary battery prepared by embodiment 1,

The horizontal axis represents capacity in mAh/g; the vertical axis represents voltage in V.

Detailed ways

Describe content of the present invention in detail below by specific embodiment:

Example 1

Take 200ml of 1mol/l CoCl solution in the flask, then add 230ml of 2mol/l _NaBH solution into _the flask; during this process, mechanically stir the solution in the flask. After the reaction was over, the stirring was stopped to separate the layers of the suspension. The supernatant was removed; the lower precipitate was taken out, washed with deionized water, and suction filtered until the _AgNO solution was added dropwise to the eluate to no longer produce white precipitate. The above-mentioned suction-filtered precipitate was vacuum-dried at 100°C to obtain a boride, which was found to be Co _2.12 B _1.03 O _3.72 by inductively coupled plasma spectroscopic analysis.

The preparation method of the negative electrode with boride as the active material is as follows: the boride synthesized above and the polytetrafluoroethylene as the binder are mixed uniformly at a mass ratio of 85:15, no conductive agent is added, and the nickel as the current collector Compressed into tablets online.

The prepared negative electrode was cut into pieces, and assembled with self-made polyvinylidene fluoride-hexafluoropropylene separator and metal lithium sheet to form an experimental battery. The electrolyte was 1M LiPF ₆ -EC/DEC (vol 1:1). After the experimental battery was aged for 12 hours, the charge and discharge test was carried out at a current density of 0.05mA/cm ² , the discharge cut-off voltage was 0.005V, and the charge cut-off voltage was 2V. Its initial discharge capacity reaches 614mAh/g, exceeding the theoretical lithium intercalation capacity of graphite-based carbon materials, and has good cycle performance. The charge and discharge curves of the experimental battery for the first three weeks are shown in the attached figure.

Example 2

Take 0.2mol/l NiCl ₂ solution 300ml and place it in the flask, then add 200ml concentration of 0.5mol/l NaBH ₄ solution into the flask; during this process, the solution in the flask is magnetically stirred. After the reaction was over, the stirring was stopped to separate the layers of the suspension. The supernatant was removed; the lower precipitate was taken out, washed with deionized water, and suction filtered until the _AgNO solution was added dropwise to the eluate to no longer produce white precipitate. After vacuum-drying the above-mentioned filtered precipitate at 90°C, continue heating at 700°C for 0.5 hour, and after cooling down, a boride was obtained, which was determined to be Ni ₃₉₆ B _0.04 O _0.01 by inductively coupled plasma spectroscopic analysis.

The preparation method of the negative electrode with boride as the active material is as follows: the boride synthesized above, the N-methylpyrrolidone solution of polyvinylidene fluoride as the binder, and the Ni powder as the conductive agent are mixed in a mass ratio of 80:5:15 Mix evenly, make a slurry, evenly coat on the copper foil as the current collector, and dry.

2300隔膜、金属锂片组装成实验电池，电解液采用1M LiClO₄-EC/DMC(vol 1∶1)。实验电池经12小时陈化后，以0.02mA/cm²的电流密度进行充放电测试，放电截止电压为0.005V，充电截止电压为2V。其首次放电容量达412mAh/g，超过了石墨类碳材料的理论嵌锂容量，并具有良好的循环性能。The prepared negative electrode was cut into pieces and compared with the commercialized

2300 separators and metal lithium sheets were assembled into experimental batteries, and the electrolyte was 1M LiClO ₄ -EC/DMC (vol 1:1). After the experimental battery was aged for 12 hours, the charge and discharge test was carried out at a current density of 0.02mA/cm ² , the discharge cut-off voltage was 0.005V, and the charge cut-off voltage was 2V. Its initial discharge capacity reaches 412mAh/g, exceeding the theoretical lithium intercalation capacity of graphite-based carbon materials, and has good cycle performance.

Example 3

Take 2.92 grams of metal Fe, 3.02 grams of metal Mg, and 1.23 grams of B, mix them uniformly, place them in a ball mill jar under a nitrogen atmosphere, and take out the product after ball milling for 50 hours. The composition is Fe _1.02 Mg _2.13 B _0.82 by induced coupling plasma spectroscopic analysis.

The preparation method of the negative electrode with boride as the active material is as follows: the boride synthesized above, the N-methylpyrrolidone solution of polyvinylidene fluoride as the binder, and the Co powder as the conductive agent are mixed in a mass ratio of 80:10:10 Mix evenly, make a slurry, evenly coat on the copper foil as the current collector, and dry.

2300隔膜、金属锂片组装成实验电池，电解液采用1M LiPF₆-EC/DMC(vol 1∶1)。实验电池经8小时陈化后，以0.01mA/cm²的电流密度进行充放电测试，放电截止电压为0.005V，充电截止电压为2V。其首次放电容量达394mAh/g，超过了石墨类碳材料的理论嵌锂容量，并具有良好的循环性能。The prepared negative electrode was cut into pieces and compared with the commercialized

2300 separators and metal lithium sheets were assembled into experimental batteries, and the electrolyte was 1M LiPF ₆ -EC/DMC (vol 1:1). After the experimental battery was aged for 8 hours, the charge and discharge test was carried out at a current density of 0.01mA/cm ² , the discharge cut-off voltage was 0.005V, and the charge cut-off voltage was 2V. Its initial discharge capacity reaches 394mAh/g, exceeding the theoretical lithium intercalation capacity of graphite-based carbon materials, and has good cycle performance.

Example 4

Take 100ml _of 0.5mol/l CoCl solution in the flask, then add 150ml of 1mol/l _NaBH solution into the flask; during this process, magnetically stir the solution in the flask. After the reaction was over, the stirring was stopped to separate the layers of the suspension. The supernatant was removed; the lower precipitate was taken out, washed with deionized water, and suction filtered until the _AgNO solution was added dropwise to the eluate to no longer produce white precipitate. After vacuum-drying the above-mentioned suction-filtered precipitate at 90° C., continue heating at 500° C. for 1 hour, and obtain borides after cooling down. The composition is Co _1.00 B _1.01 O _0.48 by induced coupling plasma spectroscopic analysis.

The preparation method of the negative electrode with boride as the active material is as follows: the boride synthesized above, the N-methylpyrrolidone solution of polyvinylidene fluoride as the binder, and the Co powder as the conductive agent are mixed in a mass ratio of 80:10:10 Mix evenly, make a slurry, evenly coat on the copper foil as the current collector, and dry.

2300隔膜、金属锂片组装成实验电池，电解液采用1M LiPF₆-EC/DMC(vol 1∶1)。实验电池经24小时陈化后，以0.01mA/cm²的电流密度进行充放电测试，放电截止电压为0.005V，充电截止电压为2V。其首次放电容量达426mAh/g，超过了石墨类碳材料的理论嵌锂容量，并具有良好的循环性能。The prepared negative electrode was cut into pieces and compared with the commercialized

2300 separators and metal lithium sheets were assembled into experimental batteries, and the electrolyte was 1M LiPF ₆ -EC/DMC (vol 1:1). After aging for 24 hours, the experimental battery was charged and discharged at a current density of 0.01mA/cm ² , the discharge cut-off voltage was 0.005V, and the charge cut-off voltage was 2V. Its initial discharge capacity reaches 426mAh/g, exceeding the theoretical lithium intercalation capacity of graphite-based carbon materials, and has good cycle performance.

Claims (7)

1. one kind is the lithium secondary battery of negative material with the metal boride, forms to comprise negative pole, positive pole, barrier film, electrolyte or polymer dielectric; Positive pole includes the transition metal oxide that contains lithium, or li-contained phosphate, or lithium metal; Separate by barrier film that has soaked electrolyte or polymer dielectric between positive pole and the negative pole; Positive electrode active material and negative electrode active material are coated in afflux respectively and extremely go up, and link to each other with the battery case two ends of mutually insulated by the afflux utmost point; It is characterized in that: negative pole is made up of metal boride, binding agent and conductive agent, and used negative active core-shell material is a metal boride.

2. described by claim 1 is the lithium secondary battery of negative material with the metal boride, it is characterized in that: the chemical composition of described metal boride is M _aB _bO _cWherein M is selected from one or more among Co, Al, Zr, V, Cr, Ni, Fe, Ti, Cu, Zn, Nd, Mo, Ag, the Mg; 1≤a≤4,0.04≤b≤1,0≤c≤4; The structural form of metal boride is crystalline state or amorphous state.

By claim 1 or 2 described be the lithium secondary battery of negative material with the metal boride, it is characterized in that: solwution method, roasting method, ball-milling method, reducing process or the precipitation method are adopted in the preparation of described metal boride.

By claim 1 or 2 described be the lithium secondary battery of negative material with the metal boride, it is characterized in that: described binding agent is selected from one or more in Kynoar, polytetrafluoroethylene, polyacrylate, methylcellulose, polymethacrylates, polyvinyl alcohol, the vinylidene fluoride-hexafluoropropylene copolymer.

By claim 1 or 2 described be the lithium secondary battery of negative material with the metal boride, it is characterized in that: described conductive agent is selected from one or more in acetylene black, graphite, carbonaceous mesophase spherules, metal powder, the alloyed powder.

By claim 1 or 2 described be the lithium secondary battery of negative material with the metal boride, it is characterized in that: do not use conductive agent in the negative pole.

By claim 1 or 2 described be the lithium secondary battery of negative material with the metal boride, it is characterized in that: described negative current collector is selected from a kind of in wire netting, metal forming, carbon cloth, carbon paper, the nickel foam.

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