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Development and Characterization of Limn 2 O 4 Based Cathode Materials for Lithium-Ion Batteries

Thesis Info

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Author

Iqbal, Azhar

Program

PhD

Institute

University of Peshawar

City

Peshawar

Province

KPK

Country

Pakistan

Thesis Completing Year

2013

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2625/1/2695S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725854048

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Spinel LiMn 2 O 4 is one of the most attractive positive electrode materials for Li-ion rechargeable batteries. In the present study, six series of low content bi-metal doped LiMn 2 O 4 with nominal compositions of LiNi x Cr y Mn 2-x-y O 4 , LiLa x Zn y Mn 2-x-y O 4 , LiCu x Cr y Mn 2-x-y O 4 , LiCu x Zn y Mn 2-x-y O 4 , LiNi x Cu y Mn 2-x-y O 4 and LiNi x Zn y Mn 2-x-y O 4 (where x = y = 0.01-0.05) were prepared by the sol-gel method. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) confirmed the formation of the pure as well as the doped spinel LiMn 2 O 4 between 285 o C and 350 o C. However, well crystallized spinel phase verified from the X-ray diffraction studies was obtained at 750 o C. XRD measurements further confirmed that all the synthesized compounds crystallized as single phase products in the cubic spinel Fd3m space group. The results showed that doping LiMn 2 O 4 with such small amount of metals has not affected the original spinel structure. Inductively coupled plasma optical emission spectrometry (ICP-OES) findings agreed the used nominal compositions. Energy dispersive X-ray analysis (EDX) also confirmed the purity of all the synthesized samples. SEM and TEM images showed that unlike the pure LiMn 2 O 4 , all the doped samples exhibited uniform size with smooth faceted polyhedral particles. The average particle size ranges from about 42 nm to 250 nm. High resolution TEM images also demonstrated the highly crystalline nature of all the six doped series. Cyclic voltammetric studies indicated that all the synthesized samples showed two pairs of well-defined anodic and cathodic peaks at around 4.0 V that corresponded to the redox couple of Mn 3+ / Mn 4+ . However, for the doped samples, the oxidation and reduction peaks were much closer to each other. The peak current was increased and the peak width was narrowed, indicating the reduced polarization of the bi-metal doped LiMn 2 O 4 , resulting from the faster iiinsertion/ extraction of Li + ions into the spinel matrix. Electrochemical impedance spectroscopy (EIS) was employed to have an insight about the synergetic effect of the bi-metal doping on the electrochemical performance of spinel LiMn 2 O 4 . The Nyquist plots showed that the charge transfer resistance (R ct ) decreases upon doping with Ni-Cr, La-Zn, Cu-Cr, Cu-Zn, Ni-Cu and Ni- Zn. The observed faster kinetics of Li + ions is attributed to the enhanced conductivities of the doped samples. Galvanostatic charge/ discharge measurements performed between 3.0 and 4.8 V for all the samples showed two plateaus around 4.0 V and 4.1 V vs. Li/ Li + that clearly demonstrated that insertion/ extraction of Li + ions takes place in two steps. The improved cycling performance of all the doped samples over the investigated 100 charge/ discharge cycles indicated that low content bi-metal doping has stabilized the spinel LiMn 2 O 4 structure by suppressing Jahn- Teller distortion. Rate capability of the pure and doped samples was also evaluated. The cells for each material were charged to 4.8 V at constant low current rate (0.1 C) and discharged to 3.0 V at 0.1 C, 0.3 C, 0.5 C, 1 C, 2 C, and 5 C, respectively. Compared to the pure LiMn 2 O 4 which retained only 41% of the initial discharge capacity when cycled at high current rate of 5 C, the capacity retention at 5 C for the Ni-Cr, La-Zn, Cu-Cr, Cu-Zn, Ni-Cu and Ni-Zn doped samples (x = y = 0.01) was 82%, 78%, 81%, 67%, 62%, and 58%, respectively. Among the various synthesized bi-metal doped series, samples with the lowest doping metal contents LiM 0.01 M'' 0.01 Mn 1.98 O 4 (where M and M'' are the various doping metal cations used in this study) appeared to be the best composition both in terms of the initial discharge capacity as well as the rate capability.
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میری جان پاکستان

میری جان پاکستان
محبت کی زباں میرا وطن ہے
وفا کی داستاں میرا وطن ہے
زندگی تو جیسے بھی ہوگزر جاتی ہے، سورج آگ برسا رہا ہو،موسم سرما کی یخ بستہ ہوائیں شدت کی سردی کا سبب بن رہی ہوں ، موسم بہار میں گلستان کے گلہائے رنگارنگ خوبصورتی بکھیر رہے ہوں۔ ہرلمحہ ہر آن زندگی کاہمامحو پرواز رہتا ہے، لیکن وہ شخص قابل صد افتخار ہے جو زندگی کی بو قلو موینوں سے محبت و پیار سے نبردآزما ہوتا ہے، اور محبت و پیارکی پتنگیںاُس وقت تک نہیں چڑھائی جا سکیں گی جب تک ماحول خوشگوار نہ ہو اور انسیت بھری فضاء نہ ہو۔
اللہ تعالیٰ کا لاکھ لاکھ شکر ہے کہ اللہ تعالیٰ نے ہمیں پاکستان کی صورت میں نعمت غیر متر قبہ سے نواز رکھا ہے۔ اس سے محبت ہمارانہ صرف طبعی تقاضا ہے کہ ہمارے عزیز واقارب یہاں رہائش پذیر ہیں ، ہماری سانسوں کی یہاں آمدورفت ہورہی ہے، اس کے شجر، اس کے حجر ہماری زندگی میں ایک اہم اور فعال کردار ادا کرتے ہیں۔ بلکہ اس سے محبت ہمارے ایمان کا حصہ ہے۔ فرمانِ رسالت مآب صلی اللہ علیہ و آلہٖ وسلم ہے کہ ’’ حب الوطن من الایمان‘‘ وطن سے محبت ایمان کا حصہ بھی ہے۔ ہمارے تو ایمان کی تکمیل ہی وطن سے محبت میں مضمر ہے۔ اگر محبت اور پیار ہے تو ایمان مکمل ہے، اگر وطن سے پیار اور محبت نہیں ہے تو دعویٰ ایمان حقیقت سے یکسر خالی ہے۔
میں کیوں نہ کہوں کہ پاکستان میری جان ہے، میری آن ہے، میری شان ہے۔ انسان اس فانی زندگی میں بھی اپنی جان سے بڑھ کر محبت اور پیار کرتا ہے ، جان کی حفاظت بھی ایمان کی ضروریات میں سے ہے۔ کیونکہ جان سلامت ہے تو پھر ایمان بھی سلامت ہے۔ اور جان کے تحفظ کے...

Pleasure versus Virtue Ethics in The Light of Aristotelians and the Utilitarianism of John Stuart Mills and Jeremy Bentham

The question of the end of morality is certainly as old as moral speculation itself. It is this question that prompted Aristotle speculating on moral or character virtue. Moral question is properly a human question since only human beings are expected to act in a given way and are subject to praise and reward or blame and punishment. We should remember that also God and angels are expected to act in a given way, but that would, strictly speaking, be the subject of moral theology and revelation, since without revelation depending only on reason, we cannot examine the acts of God and angels in order to determine how they should act. In short, it is only human beings who can be judged to act morally or immorally if we depend only on human reason, without the support of revelation. In the whole work, Stuart Mills and Jeremy Bentham stick on happiness, though each differ in approaches. Consequentialists are after the greatest happiness of the greatest number, by advocating on the struggle to that which may make man happy and avoid evil by all means. Aristotle on his side is on eudaimonism, where man is found to be happy but moral happy. Happiness for Aristotle should be reasonable, morally good and means should be maintained. This research is analytical by nature, where both qualitative and analytical methods have been implemented throughout the work. The work has been successful though some challenges could not be avoided. Finally, in doing or acting, man should observe virtue; and this is always doing good and avoiding evil.  

Role of Phosphoric Acid and Potassium Humate on Nutrient Availability in Saline-Sodic Soil

Phosphorus is the 2nd nutrient that is scarce (< 10 mg P kg−1 soil) after nitrogen (N) in 90%> of soils in Pakistan. The phosphorus contents decreased in calcareous salt affected soils. Salinity decreases the progress of plants and availability of macro and micronutrients due to high soil pH. Liquid fertilizers are more efficient than granular fertilizers due their rapid availability to the plants and less fixation in the soil. Phosphoric acid is the phosphorus containing liquid fertilizer which not only improves the availability of phosphorus to the plants, as well as it improves the availability of other nutrients like potassium, iron and copper. Potassium humate (PH) is the potassium salt of humic acid (HA) contains 5.2% K2O and 32% carbon. A successive trials were undertaken at different locations of University of Agriculture Faisalabad including field and pot experiments. Nitrogen (N), Phosphorus(P) and potassium(K) were applied by using Urea, SSP and SOP in case of control. Phosphorus was applied through phosphoric acid (10% and 50%) while PH was applied 50 and 100 kg ha-1. NPK rate of 200-150-200 kg ha-1 was followed for maize hybrid Pioneer 30Y87. Similarly for wheat recommended NPK dose 120-90-60 kg ha-1 was followed. Pot and field trial were harvested at maturity while lysimeter trial was harvested at flowering stage (65 days) and leachate was collected three time during growth period with an interval of 20 days. Plants were picked and all the samples were analyzed for growth, ionic and quality parameters. The results showed that in pot experiments growth was more with the use of 50 kg ha-1 PH and phosphoric acid (10 and 50%). All the nutrients were available in the next crop up to 25% as compared to the previous crop growth. While in case of lysimeter growth was more in mutual use of phosphoric acid and PH. Phosphorus concentration was more where phosphoric acid was applied alone however leaching of nutrients was more due to light texture of theused soil especially macro nutrients (N, P and K). Micronutrients were not detected in all the leachate samples. Results of field experiment showed the mutual use of phosphoric acid and PH considerably improved the grain ash contents, soil microbial biomass and soil respiration whereas the grain gluten contents were reduced as related to control. There was noteworthy +ve correlation among soil and crop quality parameters. Grain yield was positively associated with dry weight of shoot (r2 = 0.7592). However grain ash contents had significant negative correlation. Post-harvest analysis showed the destructive correlation among grain yield and ECe or with SAR. In field experiment higher level of both the amendments perform best as compared to other treatment including the quality parameters as well. All the data were analyzed statistically under CRD design in pot and lysimeter experiment whereas data of field experiment were analysed under RCBD design with Tukey multiple comparison test using STATISTICS 8.1 (R) software package.