CN103390746B

CN103390746B - A kind of method improving lithium ionic cell cathode material lithium titanate performance

Info

Publication number: CN103390746B
Application number: CN201210137566.XA
Authority: CN
Inventors: 王影; 张海全; 邹威; 牟成旭; 周爱军; 李晶泽
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2012-05-07
Filing date: 2012-05-07
Publication date: 2016-08-03
Anticipated expiration: 2032-05-07
Also published as: CN103390746A

Abstract

The present invention successfully realize a kind of be suitable to produce prepare high rate capability, the preparation method of high cycle life ion cathode material lithium lithium titanate.A certain proportion of lithium source and titanium source are carried out ball mill mixing by the method, obtain precursor powder and are placed in high temperature furnace sintering, i.e. can get the lithium titanate (Li of two-phase coexistent after batch mixing₄Ti₅O₁₂-Li₂TiO₃) composite.It is advantageous that: specific capacity and the charge-discharge magnification performance of lithium titanate system can be customized by the ratio controlling lithium source and titanium source；The lithium titanate system prepared by the method, carries out discharge and recharge with the charge-discharge magnification of 10C, and reversible capacity reaches 106mAh/g, and after discharge and recharge 500 times, capability retention is 98.2%, almost without decay；The method environmental protection, large-scale production controlled, applicable.

Description

A kind of method improving lithium ionic cell cathode material lithium titanate performance

Technical field

The present invention relates to a kind of solid phase synthesis technique to prepare lithium ion secondary battery negative pole lithium titanate composite material, improve its chemical property, belong to lithium rechargeable battery researchs and produces field.

Background technology

Entering 21 century, the impact that environment is caused by the use of the energy crisis being on the rise and fossil energy has become as the weakness of national development, even jeopardizes national stability.Global research worker is done a lot of work at Looking For Substitutions Of Oil, such as solar energy, wind energy etc..But the electric energy discontinuity in time that produces of these alternative energy sources and dispersibility spatially make its storage become unavoidable problem.The factors such as considering cost, reliability, ruggedness and safety, direct energy storage system (ultracapacitor etc.) and energy transfer medium system (flywheel, battery etc.) are widely studied and are applied to the storage of electric energy.Wherein battery system effectively can be changed into chemical energy electric energy and stores, and discharges with the form of electric energy it is considered to be electric energy stores one of most suitable system when of needs again.It is known that lithium ion battery has been widely used for portable electric appts.Its higher energy density becomes the first-selection of electric automobile or battery of hybrid vehicle, and is the very promising member of electrical network energy storage system.As the negative material of lithium ion battery, carbon-based material commercialization is also widely used in mobile phone and notebook.But carbon based negative electrodes material easily separates out Li dendrite and causes internal short-circuit of battery when fast charging and discharging, it is difficult to apply in the main equipment such as electric automobile and hybrid electric vehicle.The silicon of height ratio capacity, the cycle life of tin base cathode material still need to improve further.

And the lithium titanate (Li of spinel structure₄Ti₅O₁₂) possess following two major advantage: (1) Li₄Ti₅O₁₂Charging/discharging voltage platform is about 1.55V (Vs.Li/Li⁺), the formation of Li dendrite can be avoided, from the danger without there being short circuit, make battery system safer.(2)Li₄Ti₅O₁₂It is a kind of " zero strain " material, almost without change in volume during Lithium-ion embeding and abjection.This point makes with Li₄Ti₅O₁₂Battery as negative material possesses good cycle performance and long service life.But, pure phase Li₄Ti₅O₁₂Material electronics electric conductivity and ionic conductivity all ratios are relatively low, are difficult to meet the requirement of the fast charging and discharging such as electric automobile and hybrid electric vehicle, and this point hinders Li₄Ti₅O₁₂Commercially produce.Current research is concentrated mainly on raising Li₄Ti₅O₁₂The electron conduction of material and the distance of shortening lithium ion transport are to improve Li₄Ti₅O₁₂The high rate performance of material.Cation doping (Mg, Al, V etc.), surface modification (carbon coated, polyacene, copper oxide etc.) are the main method improving material electronics electric conductivity currently mainly.Mainly by reducing Li in terms of shortening lithium ion transport distance₄Ti₅O₁₂The particle diameter of material or dimension.

Recently, fake capacitance effect is the most successfully used for improving the high rate performance of lithium ion battery electrode material, it was found that have the ability of extra electrochemical reversible storage lithium ion, this energy density being conducive to improving electrode material at the boundary of composite.It is reported, Li₄Ti₅O₁₂-TiO₂Nano-complex negative material, due to the effect of Faraday pseudo-capacitance effect, shows higher specific capacity under the conditions of high power charging-discharging.But, about Li₄Ti₅O₁₂-TiO₂The preparation of nano composite material and the application in lithium ion battery there is not yet open report.

Summary of the invention

The present invention provides one to prepare two-phase coexistent composite L i₄Ti₅O₁₂-Li₂TiO₃Method.The synthesis of this material uses a kind of simple, energy-conservation, solid sintering technology of production suitable for industrialized.Two-phase coexistent material prepared by the method effectively can embed with lithium ion Faraday pseudo-capacitance effect in active material and combine with abjection, makes composite L i₄Ti₅O₁₂-Li₂TiO₃Possess higher specific capacity, excellent charge-discharge magnification performance, when charge-discharge magnification is up to 10C, circulate 500 weeks almost without capacity attenuation.

The concrete technical scheme of this invention is as follows:

1. by Li: Ti mol ratio (4～4.16): 5 weigh lithium source and titanium source.

2. by the lithium source weighed, titanium source mixture by (4～10): the ratio of grinding media to material of 1 carries out ball mill mixing in planetary ball mill.

3. being dried by the presoma that batch mixing obtains, the powder body obtained after drying is positioned in high temperature furnace and is warming up to 700～850 DEG C with the programming rate of 2～10 DEG C, and is incubated 5～15 hours, naturally cools to room temperature subsequently and i.e. can obtain this two-phase coexistent composite.

The titanium source related in such scheme is anatase structured TiO₂, lithium source be lithium source be lithium carbonate, Lithium hydrate, lithium nitrate, lithium acetate, lithium oxalate or the cooperation in several lithium source, Li: Ti mol ratio is (4～4.16): 5.

The ratio of grinding media to material during batch mixing related in such scheme is (4～10): 1, and rotating speed is 300～500r/min, and Ball-milling Time is 3～6 hours, and dispersant can use ethanol, deionized water, acetone or the mixing of several dispersant.

The sintering atmosphere related in such scheme can be directly to sinter in atmosphere, it is also possible to argon, nitrogen, helium or CO 2 gas-shielded under be sintered.

The temperature increasing schedule related in such scheme is 2～10 DEG C/min, and sintering temperature is 700～850 DEG C, and temperature retention time is 5～15 hours.

Accompanying drawing explanation

Fig. 1: the method prepares Li₄Ti₅O₁₂-Li₂TiO₃The XRD diffraction pattern of composite.

Fig. 2: the method prepares Li₄Ti₅O₁₂-Li₂TiO₃The SEM figure of composite.

Fig. 3: the method prepares Li₄Ti₅O₁₂-Li₂TiO₃The constant current charge-discharge high rate performance curve of composite.

Fig. 4: the method prepares Li₄Ti₅O₁₂-Li₂TiO₃Composite when charge-discharge magnification is 10C, cycle-index is constant current charge-discharge efficiency curve when 500 times.

Detailed description of the invention

Case study on implementation one:

Weigh lithium carbonate and titanium dioxide by Li: Ti mol ratio 4.08: 5, the lithium carbonate weighed and titanium dioxide 4 hour are carried out batch mixing with rotating speed 400r/min ball milling by the ratio of grinding media to material of 5: 1 in deionized water in planetary ball mill.The slurry obtained by batch mixing is dried in atmosphere, and the precursor powder obtained after drying is placed in Muffle furnace and is warming up to 750 DEG C with the programming rate of 2 DEG C/min in atmosphere, and is incubated 12 hours, natural to room temperature subsequently.

Prepared powder sample is analyzed through X-ray diffraction analysis instrument (XRD, x ' pertMPD), and sweep limits is 10～85 °, and leg speed is 0.03 °/min.Shown in XRD diffraction pattern such as Fig. 1 (a), the diffraction maximum of sample includes the Li of spinel structure₄Ti₅O₁₂With a small amount of Li₂TiO₃.The granule-morphology of prepared sample is recorded by field emission scanning electron microscope (CFSEM, HitachiS-4800), and uniform particle sizes is substantially distributed in 300～600nm, as shown in Fig. 2 (a).

Li₄Ti₅O₁₂-Li₂TiO₃Composite and acetylene black are ground in agate mortar about 20 minutes and are made it be sufficiently mixed, and are subsequently adding the n-methylpyrrolidone solution containing polyvinylidene binding agent and are fully ground, wherein Li₄Ti₅O₁₂-Li₂TiO₃Composite: acetylene black: the ratio of binding agent is 80: 10: 10.Slurry uniform application after grinding is on a piece of Copper Foil, dried 5～6 hours in 80 DEG C, it is pressed into the disk of a diameter of 1cm, move into after vacuum drying oven continues to be dried 12 hours with 110 DEG C and be filled with in 99.99% argon glove box, with lithium sheet for electrode assembling being become half-cell and carrying out electro-chemical test in glove box.Constant current charge-discharge is at blue electricity battery test system (CT2001A/CT2001C；WuhanKinguoElectronicsCo., Ltd.) on carry out.Constant current charge-discharge high rate performance curve is as it is shown on figure 3, when charge-discharge magnification is 0.5C, its reversible specific capacity is up to 155mAh/g；When charge-discharge magnification is 10C, reversible capacity may remain in 104.5mAh/g.

Case study on implementation two:

Weigh Lithium hydrate and titanium dioxide by Li: Ti mol ratio 4.04: 5, the Lithium hydrate weighed and titanium dioxide 4 hour are carried out batch mixing with rotating speed 400r/min ball milling by the ratio of grinding media to material of 5: 1 in ethanol in planetary ball mill.The slurry obtained by batch mixing is dried in atmosphere, and the precursor powder obtained after drying is placed in tube furnace and is warming up to 750 DEG C with the programming rate of 2 DEG C/min in argon, and is incubated 12 hours, naturally cools to room temperature subsequently.

Li₄Ti₅O₁₂-Li₂TiO₃The sign of composite and the test of battery performance such as case study on implementation one, the diffraction maximum of sample includes the Li of spinel structure₄Ti₅O₁₂With a small amount of Li₂TiO₃, shown in XRD diffraction pattern such as Fig. 1 (b).Uniform particle sizes, is substantially distributed in 300～600nm, and SEM schemes as shown in Fig. 2 (b).Constant current charge-discharge high rate performance curve is as it is shown on figure 3, when charge-discharge magnification is 0.5C, its reversible specific capacity is up to 146mAh/g；When charge-discharge magnification is 10C, reversible capacity may remain in 106mAh/g.

Case study on implementation three:

Weigh lithium nitrate and titanium dioxide by Li: Ti mol ratio 4.12: 5, the lithium nitrate weighed and titanium dioxide 4 hour are carried out batch mixing with rotating speed 400r/min ball milling by the ratio of grinding media to material of 5: 1 in ethanol in planetary ball mill.The slurry obtained by batch mixing is dried in atmosphere, and the precursor powder obtained after drying is placed in tube furnace and is warming up to 750 DEG C with the programming rate of 2 DEG C/min in nitrogen, and is incubated 12 hours, naturally cools to room temperature subsequently.

Li₄Ti₅O₁₂-Li₂TiO₃The sign of composite and the test of battery performance such as case study on implementation one, the diffraction maximum of sample includes the Li of spinel structure₄Ti₅O₁₂With a small amount of Li₂TiO₃, shown in XRD diffraction pattern such as Fig. 1 (c).Uniform particle sizes, is substantially distributed in 300～600nm, and SEM schemes as shown in Fig. 2 (c).Constant current charge-discharge high rate performance curve is as it is shown on figure 3, when charge-discharge magnification is 0.5C, its reversible specific capacity is up to 122.5mAh/g；When charge-discharge magnification is 10C, reversible capacity may remain in 85mAh/g.

The result of case study on implementation shows: along with the increase of lithium source ratio, and the high rate performance of battery is greatly improved, and cycle life substantially increases；Simultaneously because Li₂TiO₃Existence, can be with the reduction of battery specific capacity.Wherein when Li: Ti mol ratio is 4.08: 5, combination property reaches optimization: be 0.5C at charge-discharge magnification, and its specific capacity is up to 155mAh/g；Being 10C at charge-discharge magnification, capacity still can keep 72.56%.In terms of cycle life, when charge-discharge magnification is 10C, after circulating 500 weeks, capability retention is 98.2%, almost without decay, as shown in Figure 4.

Claims

1. the method improving lithium ionic cell cathode material lithium titanate performance, it is characterised in that comprise the following steps:

A. by lithium source and titanium source (4～4.16) in molar ratio: 5 add in dispersant, in planetary ball mill, batch mixing 3～6 hours is carried out with 400r/min rotating speed with ratio of grinding media to material 5: 1, the slurry obtained by batch mixing is dried in atmosphere, dried presoma is transferred to grind into powder in agate mortar stand-by；Described lithium source is one or more in lithium carbonate, Lithium hydrate, lithium nitrate, lithium acetate or lithium oxalate；Described titanium source is anatase phase titanium dioxide；

The most mixed powder is placed in high temperature furnace, in nitrogen or argon gas atmosphere, is warming up to 750 DEG C with the speed of 2～10 DEG C/min and sinters 12 hours, i.e. obtain the Li of two-phase coexistent₄Ti₅O₁₂-Li₂TiO₃Lithium titanate composite material, gained composite uniform particle sizes, particle diameter is between 300-600nm.

The method of raising lithium ionic cell cathode material lithium titanate performance the most according to claim 1, it is characterised in that one or more during dispersant uses ethanol, deionized water or acetone in step A.