De-flocculant as slurry and EPD bath stabilizer and uses thereof

Abstract

The technology concerns methods for stabilizing slurries and/or electrophoretic deposition (EPD) bath suspensions for the preparation of electrodes and/or separation area or any other coating and specifically, to electrodes and separators for use in energy storage devices.

Claims

1. An electrophoretic deposition (EPD) bath comprising a stabilized slurry, said slurry comprising at least one active material in a particulate solid form, at least one conducting additive in a particulate solid form, at least one liquid carrier, at least one deflocculant and optionally at least one binder, wherein the at least one deflocculant is selected to increase a zeta potential of the slurry and repulsive forces between the solid particles of the conducting additive, said at least one deflocculant being selected from sodium hexametaphosphate (SHMP (NaPO.sub.3).sub.n), SHMP derivatives (R-SHMP), trisodium phosphate, tetrasodium pyrophosphate, sodium tripolyphosphate, sodium tetraphosphate, and sodium polyphosphates.

2. The bath according to claim 1, wherein the slurry is free of agglomerated particulate materials.

3. The bath according to claim 1, wherein the at least one deflocculant is sodium hexametaphosphate.

4. The bath according to claim 1, for use in manufacturing a functional electrode or a separation area.

5. The bath according to claim 4, wherein the electrode is an anode.

6. The bath according to claim 1, wherein the at least one active material is an anode active material selected from graphite, silicon-based materials, carbon-silicon composite materials, metal-based materials, metal composite materials, carbon-metal composite materials and combination thereof.

7. The bath according to claim 6, wherein the silicon-based material is selected from silicon nanoparticles (SiNP), silicon nanowires (SiNW) and silicon nano flakes (SiNF).

8. The bath according to claim 6, wherein the metal-based material is selected from lithium titanium oxide (LTO), germanium nanoparticles (GeNP), germanium nanowires (GeNW), tin nanoparticles (SnNP), tin nanowires (SnNW), tin/tin sulfide, lead nanoparticles (PbNP), lead nanowires (PbNW), lithium metal alloy of formula Li.sub.xSi.sub.n, aluminum, core/shell aluminum particles, lithium and combination thereof.

9. The bath according to claim 6, wherein the carbon-metal composite material is selected from tin/tin sulfide on reduced graphene oxide (Sn/SnS@rGO), tin@rGO, lead@rGO, tin@graphite, tin@hard-carbon, tin@carbon, lead@graphite, lead@hard-carbon, lead@carbon and combination thereof.

10. The bath according to claim 4, wherein the electrode is a cathode.

11. The bath according to claim 1, wherein the at least one active material is a cathode active material selected from lithium nickel manganese cobalt oxide (NMC), lithium iron phosphate (LFP), lithium cobalt oxide (LCO), lithium ferrophosphate (LFP), lithium manganese iron phosphate (LMFP), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), nickel-rich cathode (lithium nickel oxide, LNO) and combination thereof.

12. The bath according to claim 1, wherein the at least one conductive additive in the form of particles is selected from carbon based materials or carbon composite materials.

13. The bath according to claim 1, wherein the at least one binder is present and selected from carboxymethyl cellulose (CMC) and derivatives thereof, styrene-butadiene rubber (SBR), polyvinyliedene fluoride (PVDF), lithium alginate, sodium Alginate, sodium polyacrylic acid (PAA), lithium PAA, ionic conducting polymers, hydrophobic or super-hydrophobic ion conductive polymers, optionally in crosslinked forms, and combination thereof.

14. A method of electrophoretic deposition, the method comprising obtaining a bath according to claim 1.

15. The method according to claim 14, wherein the slurry is prepared by adding at least one deflocculating agent to a carrier liquid, optionally prior to adding solid particulate materials.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

Example 1—Stability Test

(1) The following samples were prepared in order to study the effect of stabilization of a phosphate-based deflocculant, e.g., SHMP, on EPD bath compositions as described herein:

Preparation of Suspension 1

(2) 0.0548 gr of iodine was added to 100 ml of acetone, and were mixed until full dissolution. Then, 1 gr of NMC 532 (D10=3.7 μm, D50=10.1 μm. D90=18.2 μm) was added to the mixture and mixed for another 15 minutes, followed by addition of 0.022 gr PVDF and was mixed for 30 minutes. Then 0.033 gr of SC 65 was added and mixed for 1 hour, followed by 5 minutes sonication and then addition of 0.5 ml Triton X100 to give a fine dispersion (time=0).

Preparation of Suspension 2a

(3) 0.0548 gr of iodine was added to 100 ml of acetone, and were mixed until full dissolution, followed by addition of 0.021 gr PVDF and a mixing for 30 minutes. Then adding 2 ml of the “light slurry” suspension and mixing for 15 minutes, followed by 5 minutes sonication and then addition of 0.5 ml Triton X100 to give a fine dispersion (time=0).

Preparation of Suspension 2

(4) 0.1 gr of SHMP added to 100 ml of acetone and mixed, followed by the addition of 0.0548 gr of iodine to 100 ml of acetone, and were mixed until full iodine dissolution. Then 0.021 gr PVDF were added and mixed for 30 minutes. Then adding 2 ml of the “light slurry” suspension and mixing for 15 minutes, followed by 5 minutes sonication and then addition of 0.5 ml Triton X100 to give a fine dispersion (time=0).

Preparation of Suspension 3

(5) 0.3 gr of SHMP added to 100 ml of acetone and mixed, followed by addition of 0.0548 gr of Iodine was added to 100 ml of acetone, and were mixed until full Iodine dissolution. followed by addition of 0.021 gr PVDF and a mixing for 30 minutes. Then adding 2 ml of the “light slurry” suspension and mixing for 15 minutes, followed by 5 minutes sonication and then addition of 0.5 ml Triton X100 to give a fine dispersion (time=0).

Preparation of Suspension 4

(6) 0.5 gr of SHMP added to 100 ml of acetone and mixed, followed by addition of 0.0548 gr of Iodine was added to 100 ml of acetone, and were mixed until full Iodine dissolution. followed by addition of 0.021 gr PVDF and a mixing for 30 minutes. Then adding 2 ml of the “light slurry” suspension and mixing for 15 minutes, followed by 5 minutes sonication and then addition of 0.5 ml Triton X100 to give a fine dispersion (time=0).

(7) The difference between suspension 2a, suspension 2, suspension 3, and suspension 4 is only the concentration of the SHMP.

(8) The difference between suspension 1, and suspensions 2a, 2, 3, & 4 is that 1 conductive additive, active material and binder were inserted from powder, while all other suspensions active material and conductive additive were inserted using “light slurry”. The “light slurry” was prepared as follows:

(9) Adding 0.5 gr of SHMP to 15 ml of NMP, followed by 2 minutes mixing, and then adding 0.8 ml of 5% PVDF in NMP and mixing for 15 minutes. Than adding 36.8 gr of NMC 532 and mixing for 1 hour. After 1-hour, slow addition, while mixing of 1.2 gr SC 65 in 24 ml NMP and addition of 3 ml NMP—than mixed overnight.

(10) Stability measurements of EPD bath suspensions for cathode deposition comprising NMC as active material, SC65 as conductive additive and PVDF (Solef 5310) as binder were carried out. Four different suspensions were tested: suspension (1) involved commonly used ingredients in a bath. Suspensions (2), (3) and (4) included active materials, where the amount of PVDF in the light slurry equaled 0.2% out of the 4.2% needed, and where the additional PVDF was added separately as a powder.

(11) The “light slurry enables a homogeneous deposition, where each particle in the slurry contains full composition of the desired deposition. While suspension (1) contains separate particles of different size and properties, from micro size of the active material to nano size of the conductive additive, Suspensions (2), (3) and (4), initially contained larger particles. Such particles without a stabilizer flocculated and sedimented faster than expected.

(12) The only difference was observed where SHMP (e.g., 0.1 gr, ˜0.1% w/w from the total bath suspension) was added. When SHMP was added to the suspensions, the suspensions were found highly stable over 100 hours and more after initiation of the experiment.

Comparative Data: SHMP Versus KH550

(13) Three suspensions were prepared in 40 ml acetone each:

(14) First suspension: Pristine—0.5 gr silicon nanoparticles (40-50 nm) with no deflocculant;

(15) Second suspension: 0.5 gr Silicon nanoparticles (40-50 nm) with 0.2% w/w of SHMP as a deflocculant;

(16) Third suspension: 0.5 gr silicon nanoparticles (40-50 nm) with 0.2% w/w KH550.

(17) KH550 is 3-aminopropyltriethoxysilane, a versatile amino-functional coupling agent used to provide association between inorganic surfaces and organic polymers. The silicon-containing portion of the molecule provides strong bonding to substrates. The primary amine function reacts with the polymeric material.

(18) While the first and third suspensions demonstrated fairly immediate particle flocculation, in the presence of SHMP, no such flocculation was observed. After 48 hours of experiment the differences became only more significant. After 96 hours all precipitated in one way or another. But the SHMP sample (second) did not show full precipitation and was stable again after re-mixing for 1 minute, while the 1.sup.st and the 3.sup.rd precipitate quickly (in less than 2 hours) after re-mixing.

Comparative Data: SHMP Versus Li.SUB.2.CO.SUB.3

(19) Two suspensions were prepared in 40 ml distilled water each:

(20) First suspension: 0.4 gr Silicon nanoparticles (40-50 nm) with 0.2% w/w of SHMP;

(21) Second suspension: 0.4 gr silicon nanoparticles (40-50 nm) with 0.2% w/w Li.sub.2CO.sub.3.

(22) One can divide the known deflocculants into 4 major groups: a. Carbonates (such as sodium carbonate (Na.sub.2CO.sub.3), lithium carbonate (Li.sub.2CO.sub.3) and other metal carbonates); b. Silicates (such as sodium silicate); c. Alkaline light sulfonates; and d. Polyphosphates.

(23) In this comparison, the stability of a suspension with two different deflocculant types, the polyphosphates (herein represented by SHMP) and carbonates (herein represented by Li.sub.2CO.sub.3 was tested.

(24) While both showed, at the beginning good suspension stability, after several hours precipitation and floating (buoyant effect) was observed in the 2.sup.nd suspension, while no such behavior was observed in the 1.sup.st suspension even after 28 hours from the beginning of the experiment.