Selection of Conductive Additives in Li-Ion Battery Cathodes

Abstract

The lithium-ion cell has been successively improved with adoption of new cathode electrochemistries, from LiCoO 2 to highercapacity LiNi 1−x Co x O 2 to lower cost LiNi 1−x Co x O 2 . The addition of conductive additives to cathode materials has been demonstrated to improve each type. Four systems have emerged as important cathodes in recent studies: ͑i͒ the spinel LiMn 2 O 4 , ͑ii͒ LiFePO 4 , ͑iii͒ the "Gen 2" material, Li͑Ni 0.8 Co 0.15 Al 0.05 ͒O 2 , and ͑iv͒ the Li͑Ni 1/3 Co 1/3 Mn 1/3 ͒O 2 system. The architectures of model composite cathodes were generated using our prior approach in simulating packing of polydisperse arrangements; conductivity was then simulated for several realizations of each case. A key finding was that the conductive coatings significantly improve overall conductivity. Percolation was achieved for the volume fraction of active material ͑Ն30%͒ in studied cases, which was larger than the percolation threshold ͑29%͒ for a 3D spherical particulate system. Neither surface nor bulk modifications of active-material particle conductivities seem desirable targets for improvement of laminate conductivity at present. As part of future work, trade-offs between conductivity and capacity will be considered.

Transport properties of interpenetrating phase composites tin-carbon

“…The final properties may be either linearly dependent on the volume fraction of individual components or can exhibit a non-linear pattern. The non-linear dependence of electrical conductivity on the fraction of graphite grains in the composite was reported in [14,15]. In both studies, the authors observed the electron percolation effect due to the formation of the continuous cluster from graphite grains.…”

Mathematical Model of Four-Line Probe to Determine Conductive Properties of Thin-Film Battery Electrodes

“…There is a similar distinction for eigenfunctions X n : [7] where δ n,0 is the Kronecker delta and serves to make X o 0 properly normalized so that the n = 0 term can be directly included with the others in the sum. Fourier coefficients C n for the tangential and orthogonal experiments are…”

“…However, it is surprisingly difficult to accurately measure the electrical conductivity and contact resistance (between electrode and current collector) of these films. [4][5][6][7][8][9] This is because the contact resistance between probe and sample is high relative to the resistance of the sample, the sample is mechanically fragile, and the conductivity of the electrode film is confounded by the presence of a highly conductive adjacent metal layer (the current collector). The electrode film can be delaminated from the current collector in order to eliminate the last problem, 4 though it is more desirable to measure electrodes non-destructively as is proposed in this work.…”

Electron Percolation In Copper Infiltrated Carbon

“…Bhlapibul and Pruksathorn described in [10] electron percolation where one component was graphite that formed more conductive clusters. Chen et al [11] described carbon binder additives in Li-ion battery cathodes. In [12] authors presented electrical conductivity measurements of the Cu matrix composites reinforced with carbon nanofibers.…”