Electrode-forming compositions
A composition and positive electrode technology, applied in the direction of positive electrodes, electrode manufacturing, battery electrodes, etc., can solve the problems of rapid increase in slurry viscosity and gelation
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example 1
[0145] Example 1: Preparation of polymer (A) and comparative polymers:
[0146] In a 4 liter reactor equipped with an impeller running at 650 rpm, demineralized water and a suspending agent (as in Table 1) of 1.5 g / kg Mni (initial amount of monomer added in the reactor before setting the temperature) were introduced in sequence detailed in). The reactor was purged at 11°C with a vacuum (30 mmHg) followed by a nitrogen purge. Then 5.0 g of initiator was introduced. At a speed of 880 rpm, acrylic acid (AA) and perfluoromethyl vinyl ether (PMVE) were introduced. Finally, vinylidene fluoride (VDF) is introduced into the reactor. The amounts of AA, PMVE and VDF in polymer (A) used in the preparation of polymer (A) according to the invention (and in comparative polymer (Comp)) are reported in Table 1 . The reactor was gradually heated up to a setpoint temperature of 55°C and the pressure was fixed at 120 bar. The pressure was kept constant equal to 120 bar by feeding an aqueou...
example 2
[0153] Example 2: General procedure for preparing electrode-forming compositions
[0154] Electrode-forming compositions were prepared by dissolving polymer (comparative), polymer (A-1) and polymer (A-2) in N- Methylpyrrolidone (NMP) to a concentration of 8 wt%, then predetermined amounts of positive electrode active material, conductive material and residual NMP were added to the polymer in NMP solution and mixed well with a Dispermat apparatus equipped with a flat PTFE disk . The total solids concentration of the resulting slurry was 70% or 75% by weight. Details of the electrode-forming composition prepared in Example 2 are reported in Table 3.
[0155] table 3
[0156]
example 3
[0157] Example 3: Electrode-forming composition gel evaluation
[0158] Compositions (C-1) and (C-3) were prepared, followed by visual observation to check their appearance.
[0159] The flowability of the compositions was evaluated at different aging times up to 48 hours, based on the ability and quality of the compositions to be cast on PET foil (50 μm wet thickness). The results are reported in Table 4.
[0160] Table 4
[0161]
[0162] Composition (C-1) failed to provide high quality castings 4 hours after preparation. Clumping started to appear in the composition and it was unusable. In contrast, composition (A-2) showed good stability at least until 48 h after preparation.
[0163] In view of the above, it was found that the positive electrode-forming composition (C) according to the present invention is characterized by improved anti-gelling properties due to the presence of the polymer (A) comprising the binder (B).
PUM
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