Reducing Carbon in LiFePO[sub 4]/C Composite Electrodes to Maximize Specific Energy, Volumetric Energy, and Tap Density

Chen, Zhaohui; Dahn, J. R.

doi:10.1149/1.1498255

Cited by 784 publications

(476 citation statements)

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“…Carbon coatings have been successfully employed to improve electronic conductivity. [17][18][19] The use of nanoscale materials is also considered an effective way to ameliorate rate performance due to shorter lithium diffusion paths. [ 20 , 21 ] But, the large surface area of nanomaterials can cause undesirable side reactions that ultimately impair cycling performance.…”

Section: Wileyonlinelibrarycommentioning

confidence: 99%

Extremely Durable High‐Rate Capability of a LiNi_0.4Mn_0.4Co_0.2O₂ Cathode Enabled with Single‐Walled Carbon Nanotubes

Ban

et al. 2010

Advanced Energy Materials

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wileyonlinelibrary.comAdv. Energy Mater. 2011, 1, [58][59][60][61][62] Extensive studies on intercalation electrodes have enabled rapid development of lithium-ion batteries for electronic applications. However, limited cycle life and moderate rate-capability as well as the high-cost of electrode materials still restrict penetration of Li-ion cells for vehicular applications. [ 1 ] LiCoO 2 , the most commonly employed cathode in portable electronics with a capacity of ~135 mAh g − 1 , is expensive, toxic and unstable at higher voltages ( > 4.3 V). [2][3][4] Recently, Ni and Mn substituted compounds (LiNi y Mn y Co 1-2y O 2 (0 < y ≤ 0.5)) have been explored. [ 2 , 5-8 ] Unfortunately, the instability of de-lithiated Li x NiO 2 and LiMnO 2 limits their usage as Li-ion cathodes. [9][10][11] Although, the LiNi y Mn y Co 1-2y O 2 (0 < y ≤ 0.5) compounds show better thermal stability in organic electrolytes, [ 12 , 13 ] the electronic conductivity and structural stability are lower than that of LiCoO 2 , thereby negatively affecting rate capability and lifetime, respectively. Different compounds with variations in y (LiNi y Mn y Co 1-2y O 2 ) including the one discussed here have been studied, but it has still not been possible to demonstrate stable high rates with conventional electrodes. [ 14 , 15 ] Recent research in the Whittingham group has shown that LiNi y Mn y Co 1-2y O 2 (y = 0.4, 0.45) compounds have higher capacities than other compositions but still exhibit low rate-capability. [ 16 ] Many efforts to enhance the conductivity of layered structures that improves the rate performance of Ni and Mn substituted compounds have been undertaken. Carbon coatings have been successfully employed to improve electronic conductivity. [17][18][19] The use of nanoscale materials is also considered an effective way to ameliorate rate performance due to shorter lithium diffusion paths. [ 20 , 21 ] But, the large surface area of nanomaterials can cause undesirable side reactions that ultimately impair cycling performance. [ 22 ] Surface coatings with stable chemicals such as Al 2 O 3 and ZrO 2 have been employed to protect the surface resulting in a longer cycle-life. [ 2 , 23 ] However, the electronic conductivity may be reduced if the coating is an insulating material. [ 24 ] In our previous work we demonstrated that single-walled carbon nanotubes (SWNTs) could be employed as a fl exible net enabling reversible cycling for a high volume expansion materials. [ 25 ] In this work the cathode material does not undergo volume expansion but suffers from poor electrical conductivity and surface over-charge/over-discharge causing capacity fade, especially at high rate. We now demonstrate that the SWNTs can improve both conductivity and also stabilize the surface at an exceptionally high rate of 10C (charge/discharge in 6 min). Specifi cally, by constructing an LiNi 0.4 Mn 0.4 Co 0.2 O 2 cathode (NMCSWNT) with 5 wt.% SWNTs, the cathode is shown to have a capacity of ˜130 mAh g − 1 at 5C and nearly 120 mAh g − 1 at 10C, both for...

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Section: Wileyonlinelibrarycommentioning

confidence: 99%

Extremely Durable High‐Rate Capability of a LiNi_0.4Mn_0.4Co_0.2O₂ Cathode Enabled with Single‐Walled Carbon Nanotubes

Ban

et al. 2010

Advanced Energy Materials

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“…Structural defects or other factors that may retard the Li þ diffusion further lower the actual capacity of the cathode. Current strategies to enhance the electrochemical performance of LFP include carbon coating on LFP (cLFP) [1][2][3][4][5][6] , metal doping [7][8][9] , and LFP particle size reduction [10][11][12][13][14][15] . The carbon coating process has been massively used in industry because the conductive carbon layer increases the electron migration rate during the charge/discharge processes.…”

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confidence: 99%

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

Lin

et al. 2013

Nat Commun

520

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The specific capacity of commercially available cathode carbon-coated lithium iron phosphate is typically 120-160 mAh g À 1 , which is lower than the theoretical value 170 mAh g À 1 . Here we report that the carbon-coated lithium iron phosphate, surface-modified with 2 wt% of the electrochemically exfoliated graphene layers, is able to reach 208 mAh g À 1 in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes, where the graphene flakes exhibit a capacity higher than 2,000 mAh g À 1 . The highly conductive graphene flakes wrapping around carbon-coated lithium iron phosphate also assist the electron migration during the charge/discharge processes, diminishing the irreversible capacity at the first cycle and leading to B100% coulombic efficiency without fading at various C-rates. Such a simple and scalable approach may also be applied to other cathode systems, boosting up the capacity for various Li batteries.

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“…In addition, the efforts to improve ion/electron conductivity have been led to its high power density. Many studies have investigated coating [1][2][3] and doping [4][5][6] in order to improve cell performance. However, those studies have not fully explained the effect on lithium ion diffusion and phase transformation due to the difficulty and complexity of a transport process.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Lithium Diffusion Coefficient and Rate Performance by using the Discharge Curves of LiFePO₄Materials

Yu¹,

Park

Jang³

et al. 2011

Bulletin of the Korean Chemical Society

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The lithium ion diffusion coefficients of bare, carbon-coated and Cr-doped LiFePO 4 were obtained by fitting the discharge curves of each half cell with Li metal anode. Diffusion losses at discharge curves were acquired with experiment data and fitted to equations. Theoretically fitted equations showed good agreement with experimental results. Moreover, theoretical equations are able to predict lithium diffusion coefficient and discharge curves at various discharge rates. The obtained diffusion coefficients were similar to the true diffusion coefficient of phase transformation electrodes. Lithium ion diffusion is one of main factors that determine voltage drop in a half cell with LiFePO 4 cathode and Li metal anode. The high diffusion coefficient of carbon-coated and Cr-doped LiFePO 4 resulted in better performance at the discharge process. The performance at high discharge rate was improved much as diffusion coefficient increased.

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Reducing Carbon in LiFePO[sub 4]/C Composite Electrodes to Maximize Specific Energy, Volumetric Energy, and Tap Density

Cited by 784 publications

References 6 publications

Extremely Durable High‐Rate Capability of a LiNi_0.4Mn_0.4Co_0.2O₂ Cathode Enabled with Single‐Walled Carbon Nanotubes

Extremely Durable High‐Rate Capability of a LiNi_0.4Mn_0.4Co_0.2O₂ Cathode Enabled with Single‐Walled Carbon Nanotubes

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

Prediction of Lithium Diffusion Coefficient and Rate Performance by using the Discharge Curves of LiFePO₄Materials

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Reducing Carbon in LiFePO[sub 4]/C Composite Electrodes to Maximize Specific Energy, Volumetric Energy, and Tap Density

Cited by 784 publications

References 6 publications

Extremely Durable High‐Rate Capability of a LiNi0.4Mn0.4Co0.2O2 Cathode Enabled with Single‐Walled Carbon Nanotubes

Extremely Durable High‐Rate Capability of a LiNi0.4Mn0.4Co0.2O2 Cathode Enabled with Single‐Walled Carbon Nanotubes

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

Prediction of Lithium Diffusion Coefficient and Rate Performance by using the Discharge Curves of LiFePO4Materials

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Extremely Durable High‐Rate Capability of a LiNi_0.4Mn_0.4Co_0.2O₂ Cathode Enabled with Single‐Walled Carbon Nanotubes

Extremely Durable High‐Rate Capability of a LiNi_0.4Mn_0.4Co_0.2O₂ Cathode Enabled with Single‐Walled Carbon Nanotubes

Prediction of Lithium Diffusion Coefficient and Rate Performance by using the Discharge Curves of LiFePO₄Materials