Metal-oxidized graphite composite electrodes for lithium-ion batteries

Interfacial Properties of Copper‐coated Graphite Electrodes: Coating Thickness Dependence

“…In general, the presence of a metal layer or metal particles at the graphite surface leads to a substantial decrease in the charge transfer and solid electrolyte interface (SEI) resistances and to an effective protection against solvent co-intercalation permitting the use of propylene carbonate (PC)-based solvents. In our recent papers [14,15], we have reported on the effect of the addition of metal particles and of coating with 50 Å thick metal layers (Au, Cu, In, Pb, or Sn) on the electrochemical properties of partially oxidised graphite electrodes. Both modifications have been demonstrated to markedly affect the lithium intercalation capacity of the graphite electrodes especially at low temperature.…”

“…Both modifications have been demonstrated to markedly affect the lithium intercalation capacity of the graphite electrodes especially at low temperature. Composite electrodes with 1% Cu or Sn metal particles [15] as well as electrodes coated with a 50 Å thick copper layer [16] are capable of intercalating lithium up to 30% of the theoretical capacity at a temperature as low as -30°C. The high intercalation capacities at low temperature of copper composite electrodes appear to be due to the combined effect of low SEI and charge transfer resistances.…”

Improvement of Rate Capability and Low-temperature Performances of Graphite Negative Electrode by Surface Treatment with Copper Phthalocyanine

“…2) 특히 음극으로 사용되는 흑연계 물질의 저온 특성이 전체 전지의 성 능에 크게 영향을 미치는데, [3][4][5] 전해질 내 이온의 이 동도 저하, 흑연의 표면과 전해액 계면에 형성되는 SEI(Solid electrolyte interphase)내 리튬의 이동 저항, 전하 전달 저항, 흑연의 층상 구조에서 리튬이 이동하 는 저항 등이 유기적으로 영향을 미친다고 알려져 있 다. 이러한 흑연의 저온 성능을 개선하기 위해 다양한 시도가 이루어져 왔는데, 대표적인 것으로는 전해액의 전도도를 향상시키기 위해 co-solvent를 사용하거나, 6) 전해액 첨가제를 넣어 SEI의 특성을 바꾸고, 7,8) 흑연 표면에 금속을 코팅하여 전도도를 증가시키는 방법 등 이 있다.…”

Low-Temperature Characteristics and Film-Forming Mechanism of Elemental Sulfur Additive on Graphite Negative Electrode

“…• C. [4][5][6] The poor performance at low temperatures has been attributed to several factors; (i) increased viscosity and reduced Li + conductivity in electrolytes, (ii) sluggish Li + ion mobility in the surface films called solid electrolyte interphase (SEI), (iii) increased charge transfer resistances at the electrode/electrolyte interface, and (iv) reduced solid-state Li + diffusivity within the graphene sheets. Several approaches have been pursued to overcome these limitations, 4,[6][7][8] one of which is the use of propylene carbonate (PC) instead of ethylene carbonate (EC) as the solvent.…”

“…Lithium-ion batteries (LIBs) are the most promising candidate for these applications due to their high energy and power density relative to other power sources. To market HEVs and EVs, a series of technical barriers in LIBs must first be overcome, one of which is the drastic decrease in reversible capacity at low temperatures.1 According to the U.S. Department of Energy, LIBs in power-assisted HEVs should function at −30• C and survive at −46 • C. 2 It has been reported that a commercial 18650 LIB delivers an energy density of only 5% at −40• C compared to the value at 20 • C. 3 It is well known that graphite, which represents the preferred negative electrode for LIBs, delivers poor electrochemical performance below −20• C. [4][5][6] The poor performance at low temperatures has been attributed to several factors; (i) increased viscosity and reduced Li + conductivity in electrolytes, (ii) sluggish Li + ion mobility in the surface films called solid electrolyte interphase (SEI), (iii) increased charge transfer resistances at the electrode/electrolyte interface, and (iv) reduced solid-state Li + diffusivity within the graphene sheets. Several approaches have been pursued to overcome these limitations, 4,6-8 one of which is the use of propylene carbonate (PC) instead of ethylene carbonate (EC) as the solvent.…”