Natural graphite anodes

The future remains bright for the use of carbon materials in batteries. In the past several years, several new carbon materials have appeared mesophase pitch fibers, expanded graphite and carbon nanotubes. New electrolyte additives for Li-Ion permit the use of low cost PC based electrolytes with natural graphite anodes. Carbon nanotubes are attractive new materials and it appears that they will be available in quantity in the near future. They have a high ratio of the base plane to edge plain found in HOPG. The ultracapacitor application to deposit an electronically conductive polymer on the surface of a carbon nanotube may be the wave of the future. 

Zheng H, Jiang K, Abe T, Ogumi Z (2006) Electrochemical intercalation of lithium into a natural graphite anode in quaternary ammonium-based ionic liquid electrolyte. Carbon 44 203-208... 

Fig. 18.12 SEM image of a cross section of (Jeft) MAG and right) flaky natural graphite anode...

Lee, S.-E. Kim, E. Cho, J. Improvement of electrochemical properties of natural graphite anode materials with an ovoid morphology by AIPO4 coating, Electrochem. Solid-State Lett., 2007,10, Al- A4. 

Zheng H., Liu G., Battaglia V. Film-Forming Properties of Propylene Carbonate in the Presence of a Quaternary Ammonium Ionic Liquid on Natural Graphite Anode, J. Phys. Chem. C 2010, 114,6182-6189. 

Yang H, Bang H, Amine K, Prakash J (2005) Investigations of the exothermic reactions of natural graphite anode for Li-ion batteries during thermal runaway. J Electrochem Soc 152(1) A73-A79... 

In order to improve the cycling performance of lithium-ion batteries with TMP-based electrolytes, Wang et al. investigated amorphous carbon (AC) [42]. They found that the reduction decomposition of TMP solvent, which occurred without Umit on a natural graphite anode and concomitantly generated a large amount of methane and ethylene gas, was considerably suppressed on the AC anode. They attributed this improvement to the disordered structure of AC, which hindered the co-intercalation of TMP solvent Based on their experiments, they proposed a total reaction formula for TMP reduction decomposition on a natural graphite electrode ... 

J. Shim and K.A. Striebel, The dependence of natural graphite anode performance on electrode density, /. Power Source 130,2004,247-253. 

The oxygen contribution from these reactions is dependent on the nature of the anode material and the pH of the medium. The current efficiency for oxygen is generally 1—3% using commercial metal anodes. If graphite anodes are used, another overall reaction leading to inefficiency is the oxidation of... 

Magnesium. This molten salt electrolysis process is the current principal method of magnesium production. The graphite anodes can be either round or rectangular in nature (see Magnesiumand magnesium alloys). 

Two different natural graphites manufactured by Superior Graphite Co. (SL-20 and LBG-73) were tested as received on the possibility of using as anode of a cylindrical Li-ion battery. For comparison, typical synthetic graphite KS-15 from Lonza was examined. 

Barsukov I., Henry F., Doninger J., Gallego M., Huerta T., Girkant R. and Derwin D. On the electrochemical performance of lithium-ion battery anodes based on natural graphite with various surface properties. ITE Letters on Batteries, New Technologies Medicine, V.4, N.2 (2003), 163-166. 

The material was developed by the Research Institute of Electrocarbon Products (RIECP, Russian Federation) on the basis of natural graphite specially for application in Lithium-Ion cells. The samples were given with symbolic numbers, without certificates. The anodes, made of RIECP powder, had the capacity about 300 mA-h/g. The typical dicharge characteristic is submitted on Fig. 6. Irreversible capacity is about 16%. Concerning the cycle behavior, this material is not as stable as other ones tested (Fig. 10). 

SURFACE TREATED NATURAL GRAPHITE AS ANODE MATERIAL FOR HIGH-POWER LI-ION BATTERY APPLICATIONS... 

Test cells using the above graphite materials were evaluated in PC-based electrolytes. For this work, the hybrid pulse power characterization (HPPC) test was performed on cells with the different graphite anodes and PC-based electrolytes to evaluate their high power capabilities. These electrochemical experiments indicate that cells containing the surface-modified natural graphite can meet the power requirement set by the FreedomCar partnership for the hybrid vehicle applications. 

Figure 5. ASI vs. DOD for cell using surface treated natural graphite SLC1015 as anode in 1.2MLiPF6, EC/PC/MEC (30 30 40 wt%). Pulse discharge at 10C rate.

Carbonaceous materials with varying degree of graphitic order are the most common commercial anodes in secondary lithium-ion batteries. Among carbon-based materials, natural graphite is the most promising anode... 

The comparative 2016 coin cell data of the uncoated vs. Si-coated spheroidized natural graphite precursor vs Li metal counter electrode (Figure 5) reveals a remarkable effect of metal addition onto the reversible capacity of anode. Thus, the starting material s reversible capacity increased from approximately 350 mAh/g to over 510 mAh/g (data taken at 0.8V vs Li/Li+), which is 1.37 times higher than the theoretical value of the reversible capacity for graphite. 

Figure 5. First charge and discharge of CR2016 coin type half-cells with anodes based on the 15 pm, spheroidized natural graphite (bold line) and the similar graphite modified by 8wt% Si at the C/15 rate.

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