METHOD OF PREPARING BATTERY ELECTRODES
Provided herein is a method for preparing a battery electrode based on an aqueous slurry. The method disclosed herein has the advantage that an aqueous solvent can be used in the manufacturing process, which can save process time and facilities by avoiding the need to handle or recycle hazardous organic solvents. Therefore, costs are reduced by simplifying the total process. In addition, the batteries having the electrodes prepared by the method disclosed herein show impressive energy retention.
1 . A method of preparing a battery electrode, comprising the steps of:
1) pre-treating a cathode material in a first aqueous solution having a pH from about 7.0 to about 8.0 to form a first suspension;
2) drying the first suspension to obtain a pre-treated cathode material;
3) dispersing the pre-treated cathode material, a conductive agent, and a binder material in a second aqueous solution to form a slurry;
4) homogenizing the slurry by a homogenizer to obtain a homogenized slurry;
5) applying the homogenized slurry on a current collector to form a coated film on the current collector; and
6) drying the coated film on the current collector to form the battery electrode;
wherein the first aqueous solution is water, alcohol, or a mixture of water and alcohol; and
wherein the cathode material is a lithium transition metal oxide or a core-shell composite comprising a core comprising a lithium transition metal oxide and a shell formed by coating the surface of the core with a transition metal oxide or lithium transition metal oxide; wherein each of the lithium transition metal oxides is independently selected from the group consisting of LiCoO 2 , LiNiO 2 , LiNi x Mn y O 2 , Li 1+z Ni x Mn y Co 1-x-y O 2 , LiNi x Co y Al z O 2 , LiV 2 O 5 , LiTiS 2 , LiMoS 2 , LiMnO 2 , LiCrO 2 , LiMn 2 O 4 , LiFeO 2 , LiFePO 4 , and combinations thereof; wherein each x is independently from 0.3 to 0.8; each y is independently from 0.1 to 0.45; and each z is independently from 0 to 0.2; and wherein the transition metal oxide is selected from the group consisting of Fe 2 O 3 , MnO 2 , Al 2 O 3 , MgO, ZnO, TiO 2 , La 2 O 3 , CeO 2 , SnO 2 , ZrO 2 , RuO 2 , and combinations thereof.
2 . The method of claim 1 , wherein the cathode material is a nickel-rich cathode material selected from NMC532, NMC622, NMC811, or Li 1.0 Ni 0.8 Co 0.15 Al 0.05 O 2 .
3 . The method of claim 1 , wherein the first suspension is stirred for a time period from about 2 minutes to about 12 hours.
4 . The method of claim 1 , wherein the first aqueous solution is alcohol or a mixture of water and alcohol and wherein the alcohol is selected from ethanol, isopropanol, methanol, n propanol, t-butanol, or a combination thereof.
5 . The method of claim 1 , wherein the first suspension is dried by a double-cone vacuum dryer, a microwave dryer, or a microwave vacuum dryer.
6 . The method of claim 1 , wherein the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibres, carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof.
7 . The method of claim 1 , wherein the conductive agent is pre-treated in a basic solution for a time period from about 30 minutes to about 2 hours and wherein the basic solution comprises a base selected from the group consisting of H 2 O 2 , LiOH, NaOH, KOH, NH 3 .H 2 O, Be(OH) 2 , Mg(OH) 2 , Ca(OH) 2 , Li 2 CO 3 , Na 2 CO 3 , NaHCO 3 , K 2 CO 3 , KHCO 3 , and combinations thereof.
8 . The method of claim 1 , wherein the conductive agent is dispersed in a third aqueous solution to form a second suspension prior to step 3).
9 . The method of claim 1 , wherein the binder material is selected from the group consisting of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), acrylonitrile copolymer, polyacrylic acid (PAA), polyacrylonitrile, poly(vinylidene fluoride)-hexafluoropropene (PVDF-HFP), latex, a salt of alginic acid, and combinations thereof.
10 . The method of claim 9 , wherein the binder material is the salt of alginic acid and wherein the salt of alginic acid comprises a cation selected from Na, Li, K, Ca, NH 4 , Mg, Al, or a combination thereof.
11 . The method of claim 8 , wherein the binder material is dissolved in a fourth aqueous solution to form a resulting solution prior to step 3).
12 . The method of claim 11 , wherein each of the first, the second, third and fourth aqueous solutions independently is purified water, pure water, de-ionized water, distilled water, or a combination thereof.
13 . The method of claim 1 , wherein the homogenizer is a stirring mixer, a planetary stirring mixer, a blender, a mill, an ultrasonicator, a rotor-stator homogenizer, or a homogenizer.
14 . The method of claim 13 , wherein the ultrasonicator is a probe-type ultrasonicator or an ultrasonic flow cell.
15 . The method of claim 1 , wherein the homogenized slurry is applied on the current collector using a doctor blade coater, a slot-die coater, a transfer coater, or a spray coater.
16 . The method of claim 1 , wherein the coated film is dried for a time period from about 1 minute to about 30 minutes at a temperature from about 45° C. to about 100° C.
17 . The method of claim 1 , wherein the cathode material is the core-shell composite comprising the core comprising the lithium transition metal oxide and the shell formed by coating the surface of the core with the lithium transition metal oxide, and wherein each of the lithium transition metal oxides in the core and the shell is independently doped with a dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof.
18 . The method of claim 1 , wherein the cathode material is the core-shell composite, and wherein the diameter of the core is from about 5 μm to about 45 μm and the thickness of the shell is from about 3 μm to about 15 μm
19 . The method of claim 1 , wherein the electrode is able to retain at least about 83% of its initial storage capacity after 1,000 cycles at a rate of 1 C at room temperature in a full cell.