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Effects of Carbon Structure and Surface Oxygen on the Carbon’s Performance as the Anode in Lithium-Ion Battery Determined

Four carbon materials (C1, C2, C3, and C4) were tested electrochemically at the NASA Glenn Research Center at Lewis Field to determine their performance in lithium-ion batteries. They were formed as shown in the figure. This process caused very little carbon loss. Products C1 and C3 contained very little oxygen because of the final overnight heating at 540 °C. Products C2 and C4, on the other hand, contained small amounts of basic oxide. The electrochemical test involved cycles of lithium intercalation and deintercalation using C/saturated LiI-50/50 (vol %) ethylene carbonate (EC) and dimethyl carbonate (DMC)/Li half cell. The cycling test, which is summarized in the table, resulted in three major conclusions.

  1. The capacity of the carbon with a basic oxide surface converges to a constant value quickly (within 4 cycles), possibly because the oxide prevents solvent from entering the carbon structure and, therefore, prolongs the carbon’s cycle life.

  2. Under certain conditions, the disordered carbon can store more lithium than its precursor.

  3. These samples and their precursor can intercalate at 200 mA/g and deintercalate at a rate of 2000 mA/g without significant capacity loss.

CAPACITIES OF THE CARBON MATERIALS TO STORE AND RELEASE LITHIUM
 

Capacity, mA-hr/g

1st cycle

4th cycle

High current density
(After more than four cycles)

Intercalation
10 mA/g

Deintercalation
10 mA/g

Intercalation
10 mA/g

Deintercalation
10 mA/g

Intercalation
200 mA/g

Deintercalation
2000 mA/g

C1

487

280

288

268

---

---

C2

310

208

197

197

161

163

C3

249

223

224

219

---

---

C4

257

245

245

244

194

232

chemical reaction diagram showing (1) a transition from P 100 to CF<SUB>0.68</SUB> via fluorination to soft carbon via 450-degree-centigrade bromoform, 1000-degree-centigrade nitrogen, and room temperature air, to C1 after 540-degree-centigrade nitrogen and to C2 after 180-degree-centigrade vacuum and (2) a transition from P 100 to graphitized carbon via 1000-degree-centigrade nitrogen and room temperature air to C3 via 540-degree centigrade nitrogen and C4 via 180 degree centigrade vacuum

Preparation of carbon samples.

Glenn contact: Ching-cheh Hung, (216) 433–2302, Ching-cheh.Hung@grc.nasa.gov

Author: Ching-cheh Hung

Headquarters program office: OSS (ATMS)

Programs/Projects: Space Power

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Last updated April 24, 2000, by Nancy.L.Obryan@nasa.gov

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