Lithium bis͑oxalato͒borate ͑LiBOB͒ has been proposed recently as an electrolyte salt for Li-ion batteries, however safety testing of full Li-ion cells incorporating this salt has not been reported. Earlier accelerating rate calorimetry ͑ARC͒ work demonstrated that the thermal reactivity between LiBOB ethylene carbonate/diethyl carbonate ͑EC/DEC͒ electrolyte and Li 0.81 C 6 was lower than that between LiPF 6 EC/DEC electrolyte and the same negative electrode material, suggesting that LiBOB may be an attractive salt choice for safer Li-ion cells. Here, we report ARC studies of the reactions between LiBOB EC/DEC electrolyte and Li 0.5 CoO 2 and compare them to the reactions between LiPF 6 EC/DEC and the same positive electrode material. Unfortunately, the reactivity of LiBOB electrolyte with the charged positive electrode initiates at a substantial rate at about 40°C lower in temperature than for LiPF 6 electrolyte. Oven exposure tests on charged ͑4.2 V͒ 18650 Li-ion cells made using the same electrolytes and electrode materials show that the heat caused by the reaction of the negative electrode with electrolyte is less for LiBOB electrolyte than for LiPF 6 electrolyte but that the opposite is true for the heat caused by the reaction of the positive electrode with electrolyte, as expected based on the ARC measurements. Using ARC tests on the individual electrode reactivity and oven exposure testing on 18650 Li-ion cells, the usefulness of electrolytes with mixed LiBOB/LiPF 6 salts is also explored.

No abstract

The exclusion of salts from the pores of activated carbon granules is demonstrated for the first time for the salts K 2 CO 3 , K 2 HPO 4 and K 3 PO 4 . In soaking experiments, the concentrations of solutions of K 2 CO 3 , K 2 -HPO 4 , and K 3 PO 4 inside the pores are less than in the bulk solutions. This phenomenon is observed by measuring the bulk concentration, which increases upon addition of carbon. This suggests that these salts are repelled by the carbon surface. In incipient wetness experiments, the three aforementioned salts do not enter the carbon at concentrations greater than ∼1 M. The contact angles of these three salt solutions on highly oriented pyrolitic graphite and polished resin-impregnated graphite surfaces rise with concentration and approach 90°, which suggests that these solutions would not enter activated carbon pores. By contrast, soaking, incipient wetness, and contact angle measurements for salts like ZnCl 2 and Zn(CH 3 COO) 2 show preferential adsorption by soaking (the salt is depleted from the solution), high imbibing limits (maximum incipient wetness volumes) at high solution concentrations, and a reduction of contact angle with increase in concentration. It is found that the behavior of these solutions on graphite surfaces approximates the solution behavior on an activated carbon that is relatively low in acidic surface functional groups.

No abstract

No abstract