CN102517481B - High-capacity germanium-cobalt alloy lithium ion battery anode material and preparation method thereof - Google Patents

Abstract

The invention discloses a high-capacity germanium-cobalt alloy lithium ion battery anode material and a preparation method thereof, which belong to an alloy powder material of a lithium ion battery anode and a preparation method thereof. In the method, carbon powder is taken as oxidants of reduced Ge and Co for generating a Ge-Co binary alloy or a binary intermetallic compound. A compound consists of polycrystalline particles of 1-100 micrometers, the reversible capacity is up to 900 mAh/g in maximum and is more than or equal to 750 mAh/g after circulation of 40 times, and the specific content is kept at 83.3 percent. The preparation method comprises the following steps of: preparing oxidants of Ge and Co according to the Ge-Co proportion of a generated alloy; mixing uniformly with carbon powder by milling; putting into inertia gas and heating to 600-1,200 DEG C; preserving heat; and switching off for cooling to the room temperature along with a furnace. The material has high specific capacity, stable performance, a simple preparation process, low cost and an industrial prospect.

Description

A kind of heavy body germanium cobalt alloy lithium ion battery cathode material and preparation method

Technical field

The invention belongs to the alloy powder material for lithium ion battery negative, and adopt carbothermic method by the method for preparation of metal oxides alloy powder material.

Background technology

The global energy and environmental problem are just impelling that automobile industry is constantly accelerated restructuring, the paces of industrial upgrading, the power truck of energy-saving and environmental protection (EV) and hybrid electric vehicle (HEV) become the developing direction of automobile industry, and people predict that generally the power supply of the high-energy-density of EV and HEV will become one of big industry in 10 years the most potential ten future.As the present lithium ion battery of practicability, it is the secondary cell with highest energy density, and its maximization will become EV and HEV key of success.After the world climate conference of Copenhagen, the Chinese government promises to undertake the year two thousand twenty, and the per GDP CO2 emissions was thandecline 40%-50% in 2005.New-energy automobile is as the important component part of national energy-saving and emission-reduction, is listed in to accelerate during " 12 " to cultivate and one of seven great strategy new industries of development, will continue to give the emphasis support in fund and policy aspect.

Because the exploitation leeway of lithium ion heavy body novel anode material is very little, the lithium ion battery negative material performance becomes the important factor that improves energy capacity of battery and cycle life.Yet the actual capacity of present business-like carbon negative pole material is near its theoretical value (372 mAhg^-1, 800 mAhcc^-1), thereby further develop or to improve the potentiality of embedding lithium capacity of this material very little.On the other hand, the embedding lithium current potential of graphite-based negative pole (is approximately 10 near the metallic lithium current potential and lithium velocity of diffusion therein is lower^-9--10^-11Cm²s^-1), the possibility that exists lithium to separate out on the surface when high magnification charges is unfavorable for the security of battery.Therefore, seek the current potential higher slightly than carbon negative pole current potential and embed lithium, preparation specific storage height, the reliable new type lithium ion battery negative material of safety performance becomes the important research direction of industry and academia.

The storage lithium theoretical specific capacity of germanium is up to 1600mAh/g, and far above the graphite-like negative material, and the velocity of diffusion of lithium ion in germanium is 400 times in silicon.But Li and single metal form alloy Li_xM(is removal lithium embedded) time, can be attended by 2-3 volumetric expansion doubly, this will cause electrode cycle performance variation, thereby hinder the practical application of alloy anode.Forming alloy Li for suppressing or relaxing_xThe volume change of following in the M process, usually take off the electrode matrix of embedding as Li with binary or multicomponent alloy, being about to activity implants in the nonactive phase carrier mutually, form activity/nonactive alloy, one of metal mostly is ductility inactive substance preferably in the alloy, variation to volume has stronger adaptability, when Li takes off embedding, can cushion the mechanical stress of bringing owing to the active substance volume change, thereby make alloy or intermetallic compound base negative material have good cyclical stability, Ge-Cu wherein, Ge-Sb etc. show better electrochemical performance.

The employing high energy ball mill methods such as Hun-Joon Sohn of Korea S Seoul National University are prepared the negative pole that the Ge-Cu thin-film material is used for lithium ion battery, showing higher lithium storage content is 710mAh/g(Yoon Hwa, Cheol-Min Park, Sukeun Yoon, Hun-Joon Sohn, Electrochimica Acta, 55 (2010): 3324 – 3329).The Chang-Mook Hwang of Korea S Hanyang University, the method of employing magnetron sputterings such as Jong-Wan Park sinks to the bottom at Copper Foil prepares the Ge-Si film, maximum reversible capacity is 2099mAh/g (Chang-Mook Hwang, Jong-Wan Park, Journal of Power Sources, 196(2011): 6772-6780).Domestic still do not have lithium ion battery and report with the ground correlative study of Ge base alloy anode.

Studies show that: the metal Co quality is hard, good ductility is arranged, and is incorporated into the ductility that can improve alloy in other metal.The former higher hardness can be alloy and improves firm skeleton, and latter's good ductility can effectively cushion the mechanical swelling of system in the electrochemical process.

On preparation technology, the synthetic method of Ge base negative pole adopts physical sputtering more, the method that high-energy ball milling, galvanic deposit or chemical heat are decomposed, and complex process, length consuming time, the cost height, productive rate is low.Thereby, research and develop a kind of electrochemical specific capacity height, good cycling stability, and cost is low, be convenient to the multicomponent alloy negative material that industrialization is produced, for promoting the practical application of alloy material in lithium ion battery to have great importance.

Summary of the invention

Purpose of the present invention at first is to provide a kind of lithium ion battery negative material of germanium cobalt binary alloy, and the uniform particles of this material germanium cobalt-base alloy powder is tiny, and degree of crystallinity is good, germanium cobalt lithium ion battery negative material specific storage height, the good cycling stability prepared.

The present invention proposes a kind of carbothermic method that adopts simultaneously by the method for the lithium ion battery negative material of preparation of metal oxides germanium cobalt binary alloy, and not only preparation process is simple for this method, cost is low, and has the prospect of industrialized development.

Purpose of the present invention realizes in the following manner:

(1) heavy body germanium cobalt alloy lithium ion battery cathode material

This material adopt carbothermic method with carbon dust as reductive agent, the oxide compound of reduction Ge and Co, the metal Ge that restores and Co alloying, generation has compound between the Ge-Co binary alloy of stabilization of bony shelf structure or binary metal.

Compound is 1 micron～100 microns polycrystalline particle between described material Ge-Co binary alloy or binary metal, the degree of crystallinity height, and reversible capacity is up to 900mAh/g, circulates still to remain on more than the 750mAh/g after 40 times.

(2) a kind of method for preparing heavy body germanium cobalt alloy lithium ion battery cathode material

May further comprise the steps:

(1) with raw material GeO₂With Co₃O₄Or Co₂O₃Or CoO and gac or carbon black powder carry out the proportioning weighing, and above raw material is micron order or submicron order or nano level powder, GeO₂With Co₃O₄Or Co₂O₃Or the atomic ratio 7:1-1:5 that the add-on of CoO is pressed Ge/Co calculates, and the add-on of gac or carbon black is calculated by chemical formula (1) or (2) or (3) respectively:

With Co₃O₄During for the Co source:

xGeO₂ +yCo₃O₄ + (2x+4y)C → Co_3yGe_x + (2x+4y)CO↑ （1）

With Co₂O₃During for the Co source:

xGeO₂ +yCo₂O₃+ (2x+3y)C → Co_2yGe_x + (2x+3y)CO↑ （2）

When being the Co source with CoO:

xGeO₂ +yCoO+ (2x+y)C → Co_yGe_x + (2x+y)CO↑ （3）

(2) raw material of proportioning weighing mixes to adopt mechanical dry method mixed or wet mixing to incite somebody to action, place the process furnace of flowing nitrogen or argon gas or CO (carbon monoxide converter) gas, temperature rise rate with 5 ℃/min～30 ℃/min reaches temperature required 600 ℃～1200 ℃, is incubated 1～6 hour; Outage naturally cools to room temperature with furnace temperature then.

Among the described preparation method, the consumption of gac or carbon black can excessiveatomic percent 2～30%, and is oxidized to prevent system.

Described preparation method further is with GeO₂With Co₃O₄Or CoO and activated carbon are initial feed, initial feed is micron order, 3:1:10～2:1:5 prepares burden in molar ratio, the atomic ratio that is Ge:Co is 1:1～2:1, after grinding mixture evenly, place that the temperature rise rate with 5 ℃/min is elevated to 800 ℃ under the mobile argon gas atmosphere, be incubated 4～5 hours, outage naturally cools to room temperature then.

According to calculation of thermodynamics, the oxide compound of Ge and Co (460～800 ℃) under relatively low temperature can be metal Ge, Co by carbon reducing agent, the metal Ge that restores has higher activity, and easy and Co alloying generates Ge-Co alloy or the intermetallic compound with stabilization of bony shelf structure.And as lithium ion battery binary alloy electrode materials, Ge can close with lithiumation, and shows higher lithium storage content; Co is non-active element with respect to lithium, in the electrochemistry working cycle, and the various volume change of Co in can buffer electrode, thus improve the structural stability of electrode materials.

The present invention adopts the pyrochemistry reduction technique; utilize carbon dust as reductive agent; the ratio of germanium oxide and cobalt oxide in the control starting raw material; germanium oxide, cobalt oxide and carbon dust are evenly mixed; place the sintering oven that is connected with under the protective atmosphere to carry out sintering; be incubated and obtain final product Ge-Co alloy composite materials with the furnace temperature naturally cooling after 1-6 hour, and the ratio of element is consistent with the starting raw material ratio in the gained Ge-Co alloy product.

The distinguishing feature and the progress that have by evidence the present invention are:

The present invention uses the Ge-Co alloy composite materials as lithium ion battery negative material, specific storage height, stable cycle performance.

The present invention adopts carbothermic method by the preparation method of preparation of metal oxides Ge-Co alloy powder material, synthesize Ge-Co alloy degree of crystallinity height, it is 1 micron～100 microns polycrystalline particle, specific surface area is lower, be difficult for serious reunion and surface oxidation take place, thereby reduced the irreversible capacity of negative material.Simultaneously, there is inactive buffering phase in the structural pattern of binary alloy, cushioned the volume change of material in the removal lithium embedded process, thereby improved the cyclical stability of material, Ge-Co lithium ion battery negative material specific storage height, the stable cycle performance prepared, reversible capacity is up to 900mAh/g, circulates still to remain on more than the 750mAh/g after 40 times.

Technological process of the present invention simple, consuming time less, productive rate is high, thereby, the development prospect that the Ge-Co alloy that is proposed by the present invention and preparation method have industrialization.

Description of drawings

Fig. 1 is the XRD figure of the synthetic Ge-Co powdered alloy of carbothermic reduction of the present invention, and the atomic ratio of Ge, Co is 1:1, and synthesis temperature is 800 ℃, is incubated 4 hours.

Fig. 2 is the specific storage-cycle index curve of the synthetic Ge-Co alloy anode of carbothermic reduction of the present invention, and the atomic ratio of Ge, Co is 1:1, and synthesis temperature is 800 ℃, is incubated 4 hours.

The present invention will be further described below in conjunction with embodiment, and embodiment comprises but do not limit the scope that the present invention protects.

Embodiment

Embodiment 1:

With GeO₂(purity〉99.9%), Co₃O₄(purity〉99.9%), activated carbon (purity〉99%) be initial feed, initial feed is micron order, 3:1:10 prepare burden (atomic ratio that is equivalent to Ge:Co is 1:1) in molar ratio, after grinding mixture evenly, place that the temperature rise rate with 5 ℃/min is elevated to 800 ℃ under the mobile argon gas atmosphere, be incubated 4 hours, outage naturally cools to room temperature then.As Fig. 1, the XRD material phase analysis result of gained sample shows that synthetic product is the CoGe/Ge alloy complex, does not have the existence of any oxide impurity phase.

The conductive agent acetylene black that synthetic material is added 10 wt%, the binding agent PVDF of 10 wt% makes slurry, evenly be applied on the Copper Foil, after the oven dry, block circular pole piece, form test cell with metallic lithium, carry out the constant current charge-discharge experiment, charging and discharging currents is 100 mA/g, and the charging/discharging voltage scope is controlled between 0.01-2.0 V.The maximum reversible capacity of germanium cobalt negative material of preparation is 900mAh/g, and the specific storage that circulates after 40 times is 750mAh/g, and capability retention is 83.3%(such as Fig. 2).

Embodiment 2:

With GeO₂(purity〉99.9%), CoO(purity〉99.9%) and activated carbon (purity〉99%) be initial feed, initial feed is micron order, 2:1:5 prepare burden (atomic ratio that is equivalent to Ge:Co is 2:1) in molar ratio, after grinding mixture evenly, place under the mobile carbon monoxide atmosphere, be elevated to 900 ℃ with the temperature rise rate of 10 ℃/min, be incubated 5 hours, outage naturally cools to room temperature then.The XRD material phase analysis of gained sample shows that synthetic product is CoGe/Ge/CoGe₂Alloy complex does not have the existence of any oxide impurity phase.

The conductive agent acetylene black that synthetic material is added 10 wt%, the binding agent PVDF of 10 wt% makes slurry, evenly be applied on the copper platinum, after the oven dry, block circular pole piece, form test cell with metallic lithium, carry out the constant current charge-discharge experiment, charging and discharging currents is 100mA/g, and the charging/discharging voltage scope is controlled between 0.01-1.5V.The maximum reversible capacity of the Ge-Co alloy composite anode material of preparation is 700mAh/g.The specific storage that circulates after 20 times is 650mAh/g, and capability retention is 92.8%.

Embodiment 3:

With GeO₂(purity〉99.9%), Co₂O₃(purity〉99.9%) and activated carbon (purity〉99%) be initial feed, initial feed is micron order, 10:1:23 prepare burden (atomic ratio that is equivalent to Ge:Co is 5:1) in molar ratio, after grinding mixture evenly, place under the mobile carbon monoxide atmosphere, be elevated to 1200 ℃ with the temperature rise rate of 20 ℃/min, be incubated 1 hour, outage naturally cools to room temperature then.Synthetic product is Ge/CoGe₂The existence of alloy complex and a small amount of Ge, Co oxide impurity phase.

The conductive agent acetylene black that synthetic material is added 10 wt%, the binding agent PVDF of 10 wt% makes slurry, evenly be applied on the copper platinum, after the oven dry, block circular pole piece, form test cell with metallic lithium, carry out the constant current charge-discharge experiment, charging and discharging currents is 100mA/g, and the charging/discharging voltage scope is controlled between 0.01-1.5V.The maximum reversible capacity of the Ge-Co alloy composite anode material of preparation is 500mAh/g.The specific storage that circulates after 20 times is 315mAh/g, and capability retention is 63%.

Embodiment 4:

With GeO₂(purity〉99.9%), CoO(purity〉99.9%) and activated carbon (purity〉99%) be initial feed, initial feed is micron order, 2:1:5 prepare burden (atomic ratio that is equivalent to Ge:Co is 2:1) in molar ratio, after grinding mixture evenly, place under the mobile carbon monoxide atmosphere, be elevated to 600 ℃ with the temperature rise rate of 30 ℃/min, be incubated 6 hours, outage naturally cools to room temperature then.The XRD material phase analysis of gained sample shows that synthetic product is CoGe/Ge/CoGe₂Alloy complex does not have the existence of any oxide impurity phase.

The conductive agent acetylene black that synthetic material is added 10 wt%, the binding agent PVDF of 10 wt% makes slurry, evenly be applied on the copper platinum, after the oven dry, block circular pole piece, form test cell with metallic lithium, carry out the constant current charge-discharge experiment, charging and discharging currents is 100mA/g, and the charging/discharging voltage scope is controlled between 0.01-1.5V.The maximum reversible capacity of the Ge-Co alloy composite anode material of preparation is 820mAh/g.The specific storage that circulates after 20 times is 700mAh/g, and capability retention is 85.3%.

Claims (2)

1. heavy body germanium cobalt alloy lithium ion battery cathode material, it is characterized in that this material adopt carbothermic method with carbon dust as reductive agent, the oxide compound of reduction Ge and Co, the metal Ge that restores and Co alloying generate compound between Ge-Co binary alloy with stabilization of bony shelf structure or binary metal;

Compound is 1 micron～100 microns polycrystalline particle between described lithium ion battery negative material Ge-Co binary alloy or binary metal, and the degree of crystallinity height, and reversible capacity is up to 900mAh/g, circulates still to remain on more than the 750mAh/g after 40 times.

2. one kind prepares the method for material according to claim 1, it is characterized in that with GeO₂With Co₃O₄Or CoO and activated carbon are initial feed, initial feed is micron order, 3:1:10～2:1:5 prepares burden in molar ratio, the atomic ratio that is Ge:Co is 1:1～2:1, after grinding mixture evenly, place that the temperature rise rate with 5 ℃/min is elevated to 800 ℃ under the mobile argon gas atmosphere, be incubated 4～5 hours, outage naturally cools to room temperature then.

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