metal oxide based electrode for electrochemical energy storage
DESCRIPTION
Metal oxide based electrode for electrochemical energy storage. ZeWei Fang 2012/11/23. Research Background . 1. Research Content. 2. Experimental Design. 3. Reference. 4. Contents. 20 世纪 60-70 年代 石油危机!!. 寻找新能源. 电压高 干电池: 1.5V ; - PowerPoint PPT PresentationTRANSCRIPT
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
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
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
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
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.