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Metal oxide based electrode for electrochemical energy storage

ZeWei Fang 2012/11/23

Contents

Research Background 1

Research Content2

Experimental Design3

Reference4

Hot Tip

锂离子电池工作温度范围宽，放电平稳

比功率大，可

大电流充放电

金属 Li很轻比能量高，传统锌负极电池的 2-5倍

电压高干电池： 1.5V；锂原电池： 3.9V以上

20世纪 60-70年代石油危机！！

寻找新能源

Application of Lithium ion battery

upsizing

electric bicycle

Solar power generation

Electric battery

Lithium

ion battery

Stored energy

Wind power generation

Compact battery

Electric apparatus

communication

Tradition field

Development tendency

aerospace

electric car

Application

Anode of lithium ion battery

Si-based

graphite composites

metal oxide

Carbon-basedNitrides LiMxNy

The most portion

Mechanism Iron oxides , such as hematite(Fe2O3)and magnetite(Fe3O4),are attractive anode materials for rechargeable lithium-ion batteries because they can store six and eight Li per formula unit via conversion reactions , resulting in high theoretical capacities of about 1007 mAh·g-1 and 926 mAh·g-1 ， respectively.

Fe2O3+6Li 3Li2O+2Fe Fe3O4+8Li 4Li2O+3Fe

During the charge/discharge process,Fe2O3-based anodes have the following possible reactions:

Fe2O3+0.6Li++0.6e- Li0.6 Fe2O3 (theoretically at 1.1V ） (1)

Fe2O3+1.8Li++1.8e- Li 1.8Fe2O3 (theoretically at 0.9V) (2)

Fe2O3 + Li+ + e- LixFe2O3 (x=others , at 0.65 V) (3) Among these reactions , Reaction 3 is irreversible because it is usually followed by the decomposition and destruction of the crystal structure . However, in Reaction (2), Li1.8Fe2O3 can further react with Li+ and e-to form Fe and Li2O by following: Li1.8Fe2O3 + 4.2Li+ +4.2 e- 2Fe +3Li2O(4)The total reaction is:

Advantage and disadvantage

Easy change to nanostructure and controllable to synthesis

ex

Extensive resource and environment

friendlyt

Text

Higher theorical capacity and better rate performance

Lower cycle performance

Higher irreversible

Ratio performance remains to be further improved

advantagedi

sadv

anta

ge

Determining Factor

1 32

metal oxides generally possess low electrical and ion conductivities , which unavoidably results in the low-rate performance.

The rate performance of an electrode is determined by the rate of electron and ion transport

the cyclingstability will be determined by the durabilityof such transport networks

4

Due to the large volume changeof oxide materials during the charge/discharge process , as-formed electrical conductive networks may be destroyed easily

Design and Improvement

composites

Low dimension Core/shell

hollow

Porous

How

Designment

Low dimension

nanowires

nanorods

nanotubes

high interfacial contact area with the electrolyte and better accommodation of strain and volume change without any structural change or fracture.(cycle performance)it facilitates better electron and lithium ion transport(rate performance)

hollow

large surface area and the sufficient contact of active material/ electrolyte, and the short diffusion length of Li+. In well-designed nanostructures , not only the Li+ diffusion is much easier, but also the strain associated with Li+ intercalation and the volume expansion of active materials are often better accommodated , resulting in significantly improved electrochemical performance.

Porous Structure

Porous nanomaterials with large surface will absorb more electrolyte,provide more reaction active sites , even reduce the recombinationof electrons and holes , and thus improve the degradation rate.

Carbon-metal oxide composites

1.Carbon nanotube-based composites

2. Graphene-based composites

3. Ordered mesoporous carbon-based composites

4.Carbon nanofiber-based composites

5. amorphous carbon-based composites

Nanoscaled iron oxide materials and dispersing these nanostructures into carbon matrixes can potentially overcome the problems of their bulk counterparts.

The carbon matrix can help enhance the electrical contact of the electrodes and endure the huge stresses occurred during continuous cycling. In addition, the incorporation of Li-active nanoscaled iron oxide into the carbon matrix can reduce the initial irreversible capacity and improve the Columbic efficiency

Research Content

Electrochemical Application

Controllable growth mechanism

optimum condition

Synthetic route

Difficult and Innovation

Hydrolysis Temperature

Quantity of aniline

Hydrolysis Time

Precursor concentration

Carbonization time

Carbonization Temperature

Optimum parameters

Schedule

2012.05-2012.08 literature investigation and establish experiment plan

2012.08-2012.11preliminary experiment and exploring experimental conditions

2012.11-2013.02preparation and optimization experiment scheme

2013.02-2013.04explore mechanism and material characterization

2013.05-2013.08 electrochemical testing and writing Articles

2013.09-2014.01 Prefect the data

2014.02-2014.05 writing the thesis

Experiment Design

N2 保护 aniline

常温聚合反应水浴反应

Fe3+ 溶液Acided-MWCNT

超声

Preparation

Washing

Water and ethanol

product

centrifugeExtract the supernatant

fluid

3000r/min

60℃Overnight

Dry in vacuum

Standing for 30min

Precipitation 10min

Repeating for 5 times

Carbonization

N2 保护

热电偶

500ºC carbonization for 3h

Product

Next step work

Preparation Characterization

SEM TEM XRD

Thermogravimetry analysis

N2 Adsorption analysis

galvanostatic charge-discharge

cyclic voltammetry

electrochemical impedance

Hydrolysis Polymerization

Carbonization

Electrochemical testing

Innovation

1. A facile , economical, and scalable method for synthesizing

2. A carbon , precursor , aniline, was easily introduced in the middle of an ongoing reaction without any additional separation or purification steps .

3. The synthesized nanocomposite particles have carbon-coated carbon nanotubes-supported Fe3O4 structures that consist of a nanoporous interior with densely packed nanometer subunits on the surface .

4. Due to the characteristic nanostructure and carbon coating , these nanocomposite particles ,I think ,exhibit excellent capacity, cycle stability , and rate performance.

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