WO2025007219A1

WO2025007219A1 - Compositions and processes for manufacturing porous electrodes

Info

Publication number: WO2025007219A1
Application number: PCT/CA2024/050909
Authority: WO
Inventors: Xiangchun Yin
Original assignee: Saltworks Technologies Inc.
Priority date: 2023-07-05
Filing date: 2024-07-05
Publication date: 2025-01-09

Abstract

Compositions and processes for manufacturing porous electrodes with inter-connected pores and saltwater-wettable surfaces. Porous electrodes are produced by 1) coating onto a current collector a composition that includes i) 0.2 to 5.0 wt% of a block copolymer having a block with repeating ethylene oxide units, in which the block copolymer has a number average molecular weight of at least 2,000; ii) 1.0 to 10.0 wt% of a fluoropolymer, in which a mass ratio of the block copolymer to the fluoropolymer is not above 0.5; iii) 30.0 to 80.0 wt% of an organic solvent that dissolves both the block copolymer and the fluoropolymer; iv) 2.0 to 10.0 wt% of an electrically conductive additive; and v)10.0 to 50.0 wt% of either a lithium-intercalated material or a lithium-deintercalated material, and 2) inducing a nonsolvent phase inversion process to the fluoropolymer.

Description

COMPOSITIONS AND PROCESSES FOR MANUFACTURING POROUS ELECTRODES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to United States provisional patent application no. 63/524,965, filed on July 5, 2023, and entitled “Compositions And Porous Electrodes”, the entirety of which is hereby incorporated by reference herein.

TECHNICAL FIELD

[0002] The present disclosure is directed at compositions and processes for manufacturing porous electrodes with a saltwater wettable surface.

BACKGROUND

[0003] The global demand for lithium-ion batteries continues to increase. This is resulting in the need for lithium exceeding the rate at which lithium is being recovered from lithium resources, driving advancements in lithium recovery technologies. Over 70% of Earth’s lithium is found in saltwaters such as Salar brine, geothermal brine, or produced water from oil/gas fields. Various direct lithium recovery technologies, such as selective lithium adsorption, selective lithium ion exchange, and electrochemical lithium extraction have been developed to selectively recover lithium from saltwater resources. Electrochemical lithium extraction, which operates similarly to an aqueous lithium-ion battery through electrochemically driven lithium intercalation/deintercalation, offers advantages such as minimal chemical and freshwater consumption compared to other direct lithium extraction methods.

SUMMARY

[0004] According to a first aspect, there is provided a composition for manufacturing a porous layer of a porous electrode, the composition comprising: 0.2 to 5.0 wt% of a block copolymer comprising a block with repeating ethylene oxide units, wherein the block copolymer has a number average molecular weight of at least 2,000; 1.0 to 10.0 wt% of a fluoropolymer, wherein a mass ratio of the block copolymer to the fluoropolymer is 0.5 or lower; 30.0 to 80.0 wt% of an organic solvent that is able to dissolve both the block copolymer and the fluoropolymer; 2.0 to 10.0 wt% of an electrically conductive additive; and 10.0 to 50.0 wt% of either a lithium- intercalated material or a lithium-deintercalated material.

[0005] The block copolymer may have a hydrophilic-lipophilic balance value of at least 12.

[0006] The block copolymer may be a triblock copolymer of poly(ethylene oxide)-b- poly(propylene oxide)-b-poly(ethylene oxide).

[0007] The composition may further comprise 0.1 to 2.0 wt% of polyvinylpyrrolidone, and a mass ratio of polyvinylpyrrolidone to the block copolymer may be 1.0 or lower.

[0008] The composition may further comprise 2.0 to 37.5 wt% of a water-dissolvable compound, and the mass ratio of the water-dissolvable compound to the lithium-intercalated material or the lithium-deintercalated material may be 1.0 or lower.

[0009] The water-dissolvable compound may comprise an inorganic salt.

[0010] The composition may further comprise 0.1 to 1.5 wt% of carbon short fibers with an average length of 3 mm or lower, and the mass ratio of the carbon short fibers to the lithium- intercalated material or the lithium-deintercalated material may be 0.05 or lower.

[0011] According to another aspect, there is provided a process for manufacturing a porous electrode, the process comprising: preparing a slurry comprising a composition for a porous layer of the porous electrode, the composition comprising: i) 0.2 to 5.0 wt% of a block copolymer comprising a block with repeating ethylene oxide units, wherein the block copolymer has a number average molecular weight of at least 2,000; ii) 1.0 to 10.0 wt% of a fluoropolymer, wherein a mass ratio of the block copolymer to the fluoropolymer is 0.5 or lower; iii) 30.0 to 80.0 wt% of an organic solvent that is able to dissolve both the block copolymer and the fluoropolymer; iv) 2.0 to 10.0 wt% of an electrically conductive additive; and v) 10.0 to 50.0 wt% of either a lithium- intercalated material or a lithium-deintercalated material; applying the slurry as a coating onto a current collector to produce a precursor electrode; and exposing the precursor electrode to a nonsolvent comprising water to induce a phase inversion to the precursor electrode so that a porous layer is formed onto the current collector.

[0012] The block copolymer may have a hydrophilic-lipophilic balance value of at least 12.

[0013] The block copolymer may be a triblock copolymer of poly(ethylene oxide)-b- poly(propylene oxide)-b-poly(ethylene oxide).

[0014] The process may further comprise: i) pressing a porous substrate onto a surface of the slurry after the slurry has been coated onto the current collector and before the precursor electrode is exposed to the non-solvent so that at least some of the slurry enters pores of the porous substrate; and ii) removing the porous substrate from the porous layer after the induced phase inversion so that a skin layer on the porous layer is removed along with the porous substrate.

[0015] The process may further comprise drying the porous layer attached to the current collector after the induced phase inversion at a temperature below 100 °C.

[0016] The composition may further comprise 0.1 to 2.0 wt% of polyvinylpyrrolidone, and a mass ratio of polyvinylpyrrolidone to the block copolymer may be 1.0 or lower.

[0017] The composition may further comprise 2.0 to 37.5 wt% of a water-dissolvable compound, and the mass ratio of the water-dissolvable compound to the lithium-intercalated material or the lithium-deintercalated material may be 1.0 or lower.

[0018] The composition may further comprise 0.1 to 1.5 wt% of carbon short fibers with an average length of 3 mm or lower, and a mass ratio of the carbon short fibers to the lithium- intercalated material or the lithium-deintercalated material may be 0.05 or lower. [0019] The current collector may comprise a conductive substrate and an active layer on a surface of the conducive substrate such that the slurry is coated onto the active layer of the current collector, the active layer may comprise a fluoropolymer and an electrically conductive additive, and the active layer may be unable to completely absorb a water droplet of approximately 30 microliters within ten minutes.

[0020] The active layer may further comprise the lithium-intercalated material or lithiumdeintercalated material.

[0021] According to another aspect, there is provided a porous electrode produced according to the above-described process.

[0022] According to another aspect, there is provided a porous electrode comprising: a current collector; and a porous layer attached onto the current collector, the porous layer comprising: i) a block copolymer comprising a block with repeating ethylene oxide units; ii) a fluoropolymer; iii) an electrically conductive additive; and iv) at least one of a lithium-intercalated material or a lithium-deintercalated material, wherein the block copolymer has a number average molecular weight of at least 2,000.

[0023] The block copolymer may have a hydrophilic-lipophilic balance value of at least 12.

[0024] The block copolymer may be a triblock copolymer of poly(ethylene oxide)-b- poly(propylene oxide)-b-poly(ethylene oxide).

[0025] The current collector may comprise a conductive substrate and an active layer on a surface of the conducive substrate such that the slurry is coated onto the active layer of the current collector, the active layer may comprise a fluoropolymer and an electrically conductive additive, and the active layer may be unable to completely absorb a water droplet of approximately 30 microliters within ten minutes.

[0026] The active layer may further comprise the lithium-intercalated material or the lithium-deintercalated material.

[0027] The porous layer may have a thickness of at least 4 times than the active layer. [0028] This summary does not necessarily describe the entire scope of all aspects. Other aspects, features and advantages will be apparent to those of ordinary skill in the art upon review of the following description of specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the accompanying drawings, which illustrate one or more example embodiments:

[0030] FIG. 1 is a flowchart illustrating a process for manufacturing a porous electrode, according to an example embodiment.

[0031] FIG. 2 is a cross-section of a porous electrode manufactured in accordance with the process depicted in FIG. 1.

[0032] For the sake of clarity, not every component is labeled, nor is every component of each embodiment shown where illustration is unnecessary to allow those of ordinary skill in the art to understand the embodiments described herein.

DETAILED DESCRIPTION

[0033] An electrochemical lithium extraction system comprises electrodes similar to those used in an aqueous lithium-ion battery. These electrodes comprise lithium intercalated or deintercalated active material particles (e.g., LiFePO4/FePO4 or LiMmCL/k-MnCh), conductive additive particles (e.g., carbon black), and a polymer binder (e.g., polyvinylidene fluoride) that binds the particles together. While electrodes used in an aqueous lithium-ion battery are impregnated with a static aqueous electrolyte containing lithium as the only positively charged ion, electrodes for an electrochemical lithium extraction system are designed to selectively extract lithium from a flowing saltwater containing lithium and various cation impurities (e.g., sodium, calcium, and magnesium). Therefore, they benefit from more porous structures and a saltwater wettable surface compared to electrodes used in an aqueous lithium-ion battery, with the increased porosity and saltwater wettable surface facilitating selective lithium extraction.

[0034] The present disclosure is accordingly directed at compositions and processes for manufacturing a porous electrode with interconnected pores and a saltwater-wettable surface. Saltwater can transport freely into and out of the porous electrode via a porous layer, facilitating lithium diffusion within the porous electrode and lithium extraction reactions at the electrode/saltwater interface. The porous electrode herein is produced using a composition comprising a fluoropolymer binder and by applying a nonsolvent-induced phase inversion process to the fluoropolymer binder. A block copolymer comprising a block with repeating ethylene oxide units is used to regulate the formation of pores and saltwater-wettable surfaces for the porous electrode during the nonsolvent-induced phase inversion process. After coating a conductive substrate that acts as a current collector with a composition for a porous layer, a nonsolvent comprising water, which cannot dissolve the fluoropolymer, gradually permeates into the coating. This causes the fluoropolymer to precipitate, resulting in the formation of a fluoropolymer-lean phase and a fluoropolymer-rich phase having intercalated/deintercalated active material particles and conductive additive particles. After drying the electrode following the nonsolvent-induced phase inversion process, the fluoropolymer-rich phase and the fluoropolymer-lean phase become the electrode's skeleton and pores, respectively. The block copolymer regulates the formation of the fluoropolymer-rich phase and the fluoropolymer-lean phase during the nonsolvent-induced phase inversion. The repeating ethylene oxide block of the block copolymer migrates to the surfaces of the fluoropolymer-rich phase, leading to saltwater-wettable surfaces for the porous electrode. The remaining blocks of the block copolymer integrate with the fluoropolymer as anchors for the repeating ethylene oxide block, thereby preventing its removal by water during nonsolvent-induced phase inversion or an electrochemical lithium extraction process.

[0035] According to at least some embodiments, a composition that may be used to manufacture a porous layer of a porous electrode as described above comprises:

1) 0.2 to 5.0 wt% of a block copolymer comprising a block with repeating ethylene oxide units, wherein the block copolymer has a number average molecular weight of at least 2,000;

2) 1.0 to 10.0 wt% of a fluoropolymer, wherein a mass ratio of the block copolymer to the fluoropolymer is 0.5 or lower;

3) 30.0 to 80.0 wt% of an organic solvent that dissolves both the block copolymer and the fluoropolymer;

4) 2.0 to 10.0 wt% of an electrically conductive additive; and 5) 10.0 to 50.0 wt% of either a lithium-intercalated material or a lithium-deintercalated material. When between 10.0 to 50.0 wt% of one of the lithium-intercalated or lithium- deintercalated material is in the composition, the composition may nonetheless also comprise at least some of the other lithium-intercalated or lithium-deintercalated material (e.g., as an impurity).

[0036] According to at least some embodiments, the composition for the porous layer further comprises 0.1 to 2.0 wt% of polyvinylpyrrolidone, and the mass ratio of polyvinylpyrrolidone to the block copolymer is 1.0 or lower. It has been experimentally found that polyvinylpyrrolidone at a concentration of at least 0.1 wt% facilitates an even dispersion of the electrically conductive additive, and that of the lithium-intercalated material or lithium- deintercalated material, preventing their aggregation when formulating the composition and when coating the current collector with the composition to form the porous layer. It has been also experimentally found that the electrically conductive additive starts to leach out during the nonsolvent-induced phase inversion process when the mass ratio of the block copolymer to the fluoropolymer is above 0.5 or the mass ratio of polyvinylpyrrolidone to the block copolymer is above 1.0.

[0037] According to at least some embodiments, the composition for the porous layer further comprises 2.0 to 37.5 wt% of a water-dissolvable compound, wherein the mass ratio of the water-dissolvable compound to the lithium-intercalated material or the lithium-deintercalated material is 1.0 or lower. Examples of the water-dissolvable compound include, but are not limited to, inorganic salts, such as sodium chloride; sodium sulfate; potassium chloride; and potassium sulfate. During the nonsolvent-induced phase inversion process, at least some of the water- dissolvable compound dissolves in water, thereby increasing the porosity of the porous layer. It has been experimentally found that the skeleton of the porous layer formed during the nonsolvent- induced phase inversion process is unstable and disintegrates into pieces when the mass ratio of the water-dissolvable particle to the lithium-intercalated material or the lithium-deintercalated material exceeds 1.0.

[0038] According to at least some embodiments, the composition used for the porous layer further comprises 0.1 to 1.5 wt% of carbon short fibers with an average length of not more than 3.0 mm, wherein the mass ratio of the carbon short fibers to the lithium-intercalated material or the lithium-deintercalated material is 0.05 or lower. It has been experimentally found that the carbon short fibers at a concentration of at least 0.1 wt% improves the mechanical integrity of the porous layer, while the coating of the composition on the current collector suffers from dragging defects and an uneven thickness when the mass ratio of the carbon short fibers to the lithium- intercalated material or the lithium-deintercalated material exceeds 0.05.

[0039] According to at least some embodiments, the block copolymer has a hydrophilic- lipophilic balance value of at least 12. As indicated in one of the examples below, the porous layer absorbs saltwater at a speed too slow for transporting saltwater into and out of the electrode freely when a block copolymer with a hydrophilic-lipophilic balance value less than 12 is used for the composition. A number average molecular weight of at least 2,000 has experimentally been shown useful for ensuring the porous layer, and consequently the finished electrode, has saltwater wettable surfaces. If a short block copolymer with a number average molecular weight of less than 2,000 is used, the block copolymer may be washed away during the nonsolvent-induced phase inversion process or electrochemical lithium extraction, rendering the saltwater-wettable surfaces unsustainable.

[0040] According to at least some embodiments, the block copolymer in the composition comprises a triblock copolymer of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide). The fluoropolymer in the composition is polyvinylidene fluoride (PVDF). The organic solvent in the composition is selected from a group comprising N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), triethyl phosphate (TEP), or mixtures thereof. The lithium-intercalated/deintercalated material in the composition for the porous layer are selected from a group comprising LiMn2O4, LiFePC , Li1.6Mn1.eO4, Li1.33Mn1.67O4, X-MnO₂, FePO₄, Li_xMn2O4, Li_xFeC>4, 0 < x < 1.0, or their Ni and/or Co doped materials.

[0041] An example process 100 for manufacturing a porous electrode is depicted in FIG. 1. The process 100 begins at block 102, in which a material that will eventually serve as the electrode’s current collector is obtained. A conductive substrate alone may be provided as the current conductor, or as discussed further below, the conductive substrate may be modified (e.g., coated or chemically treated) to have an active layer and the substrate and layer collectively may be treated as the current collector.

[0042] The process 100 also comprises:

1) preparing a slurry comprising the composition for the porous layer of the porous electrode as described above (block 104);

2) applying the slurry onto a current collector, such as by coating the current collector, to produce a precursor electrode (block 106); and

3) exposing the precursor electrode to a nonsolvent comprising water for the fluoropolymer to induce a phase inversion to the precursor electrode so that a porous layer is formed onto the current collector (block 110).

[0043] According to at least some embodiments, the process 100 for manufacturing the porous electrode further comprises applying a porous substrate onto a surface of the slurry after forming the precursor electrode so that at least some of the slurry enters the porous substrate (block 108), and removing the porous substrate from the porous layer after the nonsolvent-induced phase inversion so that a skin layer of the porous layer is removed along with the porous substrate (block 112). Blocks 108 and 112 in particular are optional, and hence are shown in dashed lines in FIG. 1. Examples of porous substrates include, but are not limited to, a paper towel, woven fabric, or nonwoven fabric. Without the application of the porous substrate to the surface of the precursor electrode, a skin layer may be formed during the nonsolvent-induced phase inversion on the surface of the porous layer. The skin layer has less porosity than the underlying porous layer. The removal of the skin layer with the porous substrate after the nonsolvent-induced phase inversion leads to a porous layer with uniform porosity throughout its entire structure.

[0044] According to at least some embodiments, the process 100 for manufacturing the porous electrode further comprises drying the porous layer that becomes attached onto the current collector as a result of the nonsolvent-induced phase inversion at a temperature below 100 °C (block 114), preferably below 70 °C, and more preferably below 40 °C. Drying the porous layer at temperatures exceeding 100 °C causes the entire block copolymer (including both the ethylene oxide units and the rest of anchoring blocks) to migrate onto the surface of the porous layer. This migration can result in the block copolymer being washed away by a flowing saltwater during electrochemical lithium extraction, leading to unstable saltwater-wettable surfaces.

[0045] According to at least some embodiments, the conductive substrate used for the current collector for the porous electrode comprises a porous titanium mesh, a woven carbon fabric, or nonwoven carbon fabric. The slurry with the composition as described above is coated onto surfaces and into pores of the current collector when manufacturing the porous electrodes.

[0046] According to at least some embodiments, the current collector for the porous electrode comprises a conductive substrate with a flat surface, such as a titanium foil or a graphite foil, and an active layer (as mentioned above in respect of block 100) on the surfaces of the conductive substrate to enhance the adhesion between the porous layer and the current collector. Without the active layer, the porous layer may delaminate from the conducive substrate during the nonsolvent-induced phase inversion or the drying process. The porous electrode can be prepared through first coating and forming the active layer onto the conductive substrate to create the current collector. The composition for the porous layer is then coated onto the active layer of the current collector. Alternatively, the active layer and the porous layer can be prepared concurrently through applying a first layer, which serves as the active layer, as a coating onto the conductive substrate, and then applying a second layer, comprising the composition for the porous layer, as a coating onto the first layer. The first layer and the second layer are subjected to a nonsolvent-induced phase inversion together, resulting in the active layer being formed on the conductive substrate and the porous layer being formed on the active layer. The active layer comprises a fluoropolymer, an electrically conductive additive, and optionally at least one of a lithium -intercalated material or a lithium-deintercalated material. The fluoropolymer and the electrically conductive material for the active layer may or may not be the same as those used for the porous layer. In their dry states, the active layer cannot completely absorb a water droplet of around 30 microliters within ten minutes, whereas the porous layer can completely absorb a water droplet of around 30 microliters in less than 5 seconds.

[0047] In the above example embodiments, the various weight percentages provided for the block copolymer, fluoropolymer, organic solvent, electrically conductive additive, and lithium- intercalated/deintercalated material in respect of the slurry may change during the electrode manufacturing process. For example, the solvent and other water-soluble constituents may leach away, including a small amount of the block copolymer. Consequently, the weight percentages of the various constituents may differ in the finished electrode than in the slurry used for the porous layer during the electrode manufacturing process. Nevertheless, in the finished electrode, the block copolymer retains a number average molecular weight of at least 2,000, while the fluoropolymer, electrically conductive additive, and lithium-intercalated/deintercalated material remain in the porous layer in suitable proportions.

[0048] Certain embodiments are further illustrated in the following examples. It is however to be understood that these examples are for illustrative purposes only, and are not to be used to limit the scope of the present disclosure in any manner. Moreover, features of any one of the examples may be combined with features of any other of the examples, so long as such features are not mutually exclusive.

EXAMPLES

Example 1 : Preparing a current collector with an active layer

[0049] A first slurry for the active layer, comprising PVDF (3.2 wt%), NMP (68.0 wt%), C65 carbon black (3.2 wt%), and LiMn2O4 (25.6 wt%), was coated onto a conductive substrate in the form of a graphite foil using a doctor blade. The coated graphite foil was immersed into a water bath at room temperature for Ih to induce phase inversion, leach NMP, and solidify the coating. Subsequently, the graphite foil, along with the solidified coating from the phase inversion, was dried at 70 °C under vacuum to produce a current collector with an active layer.

[0050] The active layer had a thickness of about 80 micrometers and was unable to completely absorb a water droplet of around 30 microliters in 10 minutes.

Example 2: Preparing a porous electrode by forming a porous layer onto an active layer of a current collector

[0051] A second slurry for a porous layer of the porous electrode was prepared comprising 1.0 wt% of triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (a number average molecular weight of about 12,600 and a hydrophilic-lipophilic balance value of 18 - 23), 0.5 wt% of polyvinylpyrrolidone (a number average molecular weight of about (e.g. +/- 30%) 1,300,000), 3.5 wt% of PVDF, 50.2 wt% of NMP, 5.0 wt% of C65 carbon black, and 39.8 wt% of LiMn2O4, and was applied using a doctor blade as a coating onto the current collector made from Example 1 to form a precursor electrode. The precursor electrode was immersed into a water bath for 2h to induce a phase inversion and to form a porous layer attached to the active layer. The porous layer, along with the current collector, was dried at 40 °C to produce a porous electrode.

[0052] The porous layer had a thickness of about 500 micrometers and completely absorbed completely a water droplet of around 30 microliters in less than 5 seconds. The crosssection of the porous electrode manufactured is schematically illustrated in FIG. 2. More particularly, in FIG. 2 the current collector 202 from Example 1 comprises the active layer 206 coated on to the conductive substrate 204. The porous layer 208 is on the active layer 206, with the porous layer comprising an array of columns of electrode constituents 216 (i.e., the PVDF, LiMn2C>4, NMP, carbon black, and the block copolymer mixture). Between those columns of the electrode constituents 216 are gaps that act as large pores 214, which give the porous layer 208 its porosity. On top of the porous layer 208 is the skin layer 210, which also includes the electrode constituents 216. However, in the skin layer 210 the gaps between the electrode constituents 216 is much smaller than the corresponding gaps in the porous layer 208, resulting in the skin layer 210 having much smaller pores 212 than the porous layer 208.

Example 3 : Preparing a porous electrode by forming the active layer and the porous layer using one phase inversion

[0053] A first slurry for an active layer, comprising PVDF (3.2 wt%), NMP (68.0 wt%), C65 carbon black (3.2 wt%), and LiMn2O4 (25.6 wt%) was coated onto a conductive substrate in the form of a graphite foil using a doctor blade to form a first layer. A second slurry for use as a porous layer, comprising 1.0 wt% of triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (a number average molecular weight of about 12,600, a hydrophilic- lipophilic balance value of 18 - 23), 0.5 wt% of polyvinylpyrrolidone (a number average molecular weight of about 1,300,000), 3.5 wt% of PVDF, 50.2 wt% of NMP, 5.0 wt% of C65 carbon black, and 39.8 wt% of LiMn2O4, was coated using a doctor blade to form a second layer onto the first layer. The first layer and the second layer, along with the graphite foil, were immersed into a water bath for 2h to induce a phase inversion and to form an active layer attached to the graphite foil and a porous layer attached to the active layer. The active layer and the porous layer, along with the graphite foil, were dried at 40 °C to produce a porous electrode.

[0054] The total thickness of the active layer and the porous layer was about 550 micrometers and the porous layer completely absorbed a water droplet of around 30 microliters in less than 5 seconds.

Example 4: Preparing a porous electrode by forming a porous layer onto an active layer of a current collector

[0055] A porous electrode was prepared similarly to Example 2, except that the second slurry for the porous layer comprised 1.5 wt% of triblock copolymer polyethylene oxide)-b- poly(propylene oxide)-b-poly(ethylene oxide) (number average molecular weight of about 12,600, hydrophilic-lipophilic balance value of 18 - 23) and no polyvinylpyrrolidone.

[0056] The porous layer had a thickness of about 500 micrometers, developed cracks during the drying process, and completely absorbed a water droplet of around 30 microliters in less than 5 seconds.

Example 5: Preparing a porous electrode by forming a porous layer onto an active layer of a current collector

[0057] A porous electrode was prepared similarly to Example 2, except that the second slurry for the porous layer comprised 1.0 wt% of diblock copolymer polyethylene-b-poly(ethylene oxide) (number average molecular weight of about 2250, a hydrophilic-lipophilic balance value of 15) instead of the triblock copolymer.

[0058] The porous layer had a thickness of about 500 micrometers and completely absorbed a water droplet of around 30 microliters in about 30 seconds. Example 6: Preparing a porous electrode by forming a porous layer onto an active layer of a current collector

[0059] A porous electrode was prepared similarly to Example 2, except that the second slurry for the porous layer comprised 0.5 wt% of triblock copolymer polyethylene oxide)-b- poly(propylene oxide)-b-poly(ethylene oxide) (number average molecular weight of about 12,600, a hydrophilic-lipophilic balance value of 18 - 23), 0.2 wt% of polyvinylpyrrolidone (an average weight molecular weight of about 1,300,000), 1.6 wt% of PVDF, 76.4 wt% of NMP, 2.4 wt% of C65 carbon black, and 18.9 wt% of LiMn2O4.

[0060] The porous layer had a thickness of about 500 micrometers and completely absorbed a water droplet of around 30 microliters within 5 seconds.

Example 7: Preparing a current collector with an active layer

[0061] The current collector was prepared similarly to Example 1, except that the first slurry for the active layer comprised LiFePCU instead of LiMn2O4.

[0062] The active layer had a thickness of about 80 micrometers and was unable to completely absorb a water droplet of around 30 microliters within 10 minutes.

Example 8: Preparing a porous electrode by forming a porous layer onto an active layer of a current collector

[0063] A porous electrode was prepared similarly to Example 2, except that the current collector was prepared as described in Example 6, and the second slurry for the porous layer comprised 1.2 wt% of triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b- poly(ethylene oxide) (number average molecular weight of about 12,600, a hydrophilic-lipophilic balance value of 18 - 23), 0.6 wt% of polyvinylpyrrolidone (an average weight molecular weight of about 1,300,000), 4.2 wt% of PVDF, 60.2 wt% of NMP, 4.0 wt% of C65 carbon black, and 29.8 wt% of LiFePO₄.

[0064] The porous layer had a thickness of about 500 micrometers and completely absorbed a water droplet of around 30 microliters in 5 seconds. Example 9: Preparing a porous electrode by forming a porous layer directly onto a porous current collector without an active layer

[0065] The second slurry presented in Example 2 was applied as a coating using a scraper blade onto both sides of a titanium mesh current collector (thickness of about 2 mm) to create a precursor electrode. The precursor electrode was immersed into a water bath for 2h to induce a phase inversion and to form a porous layer attached to the titanium mesh current collector. The porous layer, along with the titanium mesh, was dried at 40 °C to produce a porous electrode.

[0066] The porous electrode had a thickness of about 2,200 micrometers and completely absorbed completely a water droplet of around 30 microliters in less than 5 seconds.

Example 10: Preparing a porous electrode without a skin layer by forming a porous layer onto an active layer of a current collector

[0067] The second slurry presented in Example 2 was applied as a coating using a doctor blade onto the current collector prepared in Example 1. A Bounty™ paper towel acting as a porous substrate was pressed gently onto the surface of the second slurry coating. Once some of the second slurry coating was wicked into pores of the paper towel, the paper towel was affixed to the surface of the precursor electrode. The precursor electrode, along with the paper towel, was immersed into a water bath for 2h to induce a phase inversion and to form a porous layer attached to the active layer. The paper towel was removed after the phase inversion. The porous layer, along with the current collector, was dried at 40 °C to produce a porous electrode.

[0068] The porous layer had a thickness of about 500 micrometers, had no skin layer, and completely absorbed a water droplet of around 30 microliters in less than 5 seconds.

Example 11 : Preparing a porous electrode without a skin layer by forming a porous layer onto an active layer of a current collector and by using dissolvable NaCl particles

[0069] A second slurry for the porous electrode, comprising 0.7 wt% of triblock copolymer poly(ethylene oxi de)-b -poly (propylene oxi de)-b -poly (ethylene oxide) (number average molecular weight of about 12,600, a hydrophilic-lipophilic balance value of 18 - 23), 0.3 wt% of polyvinylpyrrolidone (an average weight molecular weight of about 1,300,000), 2.3 wt% of PVDF, 51.7 wt% of NMP, 6.6 wt% of C65 carbon black, 23.1 wt% of LiMn2O4, 0.5% of carbon short fiber (average length of 3.0 mm), and 14.8 wt% of NaCl, was applied as a coating using a doctor blade onto the current collector made from Example 1 to create a precursor electrode. A Bounty™ paper towel acting as a porous substrate was pressed gently onto the surface of the second slurry coating. Once some of the coated second slurry was wicked into the pores of the paper towel, the paper towel was affixed to the surface of the precursor electrode. The precursor electrode, along with the paper towel, was immersed into a water bath for 2h to induce a phase inversion, dissolve NaCl, and form a porous layer attached to the active layer. The paper towel was removed after the phase inversion. The porous layer, along with the current collector, was dried at 40 °C to produce a porous electrode.

[0070] The porous layer had a thickness of about 4,000 micrometers and completely absorbed a water droplet of around 30 microliters in less than 5 seconds.

Example 12: Preparing a porous electrode without a skin layer by directly forming a porous layer onto a porous current collector without an active layer

[0071] The second slurry presented in Example 10 was applied as a coating using a scraper blade onto both sides of a titanium mesh current collector (thickness of about 2 mm) to form a precursor electrode. Two Bounty™ paper towels acting as porous substrates were pressed gently onto both sides of the precursor electrode. Once some of the coated second slurry was wicked into the pores of the paper towels, the paper towels were affixed to both sides the precursor electrode. The precursor electrode, together with the paper towels, were immersed into a water bath for 2h to induce a phase inversion, dissolve NaCl, and form a porous layer attached to the titanium mesh current collector. After removing the paper towels, the porous layer, along with the current collector, was dried at 40 °C to produce a porous electrode.

[0072] The porous layer had a thickness of about 6,000 micrometers and completely absorbed a water droplet of around 30 microliters in less than 5 seconds. Example 13: Preparing a porous electrode without a skin layer by forming a porous layer onto an active layer of a current collector

[0073] A porous electrode was prepared similarly to Example 10, except that the second slurry for the porous layer comprised 0.7 wt% of triblock copolymer polyethylene oxide)-b- poly(propylene oxide)-b-poly(ethylene oxide) (number average molecular weight of about 12,600, a hydrophilic-lipophilic balance value of 18 - 23), 0.4 wt% of polyvinylpyrrolidone (an average weight molecular weight of about 1,300,000), 2.5 wt% of PVDF, 36.6 wt% of NMP, 5.1 wt% of C65 carbon black, 28.9 wt% of LiMn2O4, 0.6% of carbon short fiber (average length of 3.0 mm), and 25.1 wt% of NaCl.

[0074] The porous layer had a thickness of about 4,000 micrometers and completely absorbed a water droplet of around 30 microliters in less than 5 seconds.

Comparative Example 1 : Preparing an electrode by forming a porous layer as directly onto a graphite foil without an active layer

[0075] An electrode was prepared similarly to Example 2, except that the second slurry presented in Example 2 was coated directly onto a graphite foil as an intended current collector instead of the current collector prepared in Example 1. The porous layer delaminated from the graphite foil during drying.

Comparative Example 2: Preparing an electrode using a composition without a block copolymer for a non-saltwater-wettable electrode layer

[0076] An electrode was prepared similarly to Example 2, except that the slurry for the electrode layer comprised no block copolymer but 1.5 wt% of polyvinylpyrrolidone (number average molecular weight of about 1,300,000) instead.

[0077] The electrode layer had a thickness of about 500 micrometers and could not completely absorb a water droplet of around 30 microliters in 5 minutes, which is too slow for transporting saltwater into and out of the electrode freely. The electrode layer was consequently unsuitable for use as a porous layer. Comparative Example 3: Preparing an electrode using a composition with a block copolymer having a molecular weight less than 2,000 for a non-saltwater- wettable electrode layer

[0078] An electrode was prepared similarly to Example 2, except that the slurry for the electrode layer comprised 1.0 wt% of polyethylene glycol octadecyl ether (number average molecular weight of about 711, hydrophilic-lipophilic balance value of 12) instead of the triblock copolymer of polyethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide).

[0079] The electrode layer had a thickness of about 500 micrometers and could not completely absorb a water droplet of around 30 microliters in 5 minutes, which is too slow for transporting saltwater into and out of the electrode freely. The electrode layer was consequently unsuitable for use as a porous layer.

Comparative Example 4: Preparing an electrode using a composition with a block copolymer having a molecular weight less than 2,000 and a hydrophilic-lipophilic balance value less than 12 for a non-saltwater-wettable electrode layer

[0080] An electrode layer was prepared similarly to Example 2, except that the slurry for the electrode layer comprised 1.0 wt% of diblock copolymer polyethylene-b-poly(ethylene oxide) (number average molecular weight of about 920, hydrophilic-lipophilic balance value of 10) instead of the triblock copolymer of polyethylene oxide)-b-poly(propylene oxide)-b- poly(ethylene oxide).

[0081] The electrode layer had a thickness of about 500 micrometers and could not completely absorb a water droplet of around 30 microliters in 5 minutes, which is too slow for transporting saltwater into and out of the electrode freely. The electrode layer was consequently unsuitable for use as a porous layer.

[0082] The terminology used herein is only for the purpose of describing particular embodiments and is not intended to be limiting. Accordingly, as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and "comprising", when used in this specification, specify the presence of one or more stated features, integers, steps, operations, elements, and components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and groups. Directional terms such as "top", "bottom", "upwards", "downwards", "vertically", and "laterally" are used in the following description for the purpose of providing relative reference only, and are not intended to suggest any limitations on how any article is to be positioned during use, or to be mounted in an assembly or relative to an environment. Additionally, the term "connect" and variants of it such as "connected", "connects", and "connecting" as used in this description are intended to include indirect and direct connections unless otherwise indicated. For example, if a first device is connected to a second device, that coupling may be through a direct connection or through an indirect connection via other devices and connections.

[0083] Use of language such as "at least one of X, Y, and Z," "at least one of X, Y, or Z," "at least one or more of X, Y, and Z," "at least one or more of X, Y, and/or Z," or "at least one of X, Y, and/or Z," is intended to be inclusive of both a single item (e.g., just X, or just Y, or just Z) and multiple items (e.g., {X and Y}, {X and Z}, {Y and Z}, or {X, Y, and Z}). The phrase "at least one of' and similar phrases are not intended to convey a requirement that each possible item must be present, although each possible item may be present.

[0084] A reference to a variable being “about” or “approximately” a value means that variable is within +/- 30% of that value unless the context requires otherwise.

[0085] It is contemplated that any part of any aspect or embodiment discussed in this specification can be implemented or combined with any part of any other aspect or embodiment discussed in this specification, so long as such those parts are not mutually exclusive with each other.

[0086] While every effort has been made to provide a detailed and accurate description of the disclosure herein, it should be noted that the scope of the disclosure is not limited to the exact configurations and embodiments described. The description provided is intended to illustrate the principles of the disclosure and not to limit the disclosure to the specific embodiments illustrated. It is intended that the scope of the disclosure be defined by the appended claims, their equivalents, and their potential applications in other fields.

Claims

1. A composition for manufacturing a porous layer of a porous electrode, the composition comprising:

3) 30.0 to 80.0 wt% of an organic solvent that is able to dissolve both the block copolymer and the fluoropolymer;

4) 2.0 to 10.0 wt% of an electrically conductive additive; and

5) 10.0 to 50.0 wt% of either a lithium-intercalated material or a lithium-deintercalated material.

2. The composition of claim 1, wherein the block copolymer has a hydrophilic-lipophilic balance value of at least 12.

3. The composition of claim 2, wherein the block copolymer is a triblock copolymer of poly(ethylene oxi de)-b -poly (propylene oxi de)-b -poly (ethylene oxide).

4. The composition of claim 3, further comprising 0.1 to 2.0 wt% of polyvinylpyrrolidone, wherein a mass ratio of polyvinylpyrrolidone to the block copolymer is 1.0 or lower.

5. The composition of claim 4, further comprising 2.0 to 37.5 wt% of a water-dissolvable compound, wherein the mass ratio of the water-dissolvable compound to the lithium- intercalated material or the lithium-deintercalated material is 1.0 or lower.

6. The composition of claim 5, wherein the water-dissolvable compound comprises an inorganic salt.

7. The composition of claim 5, further comprising 0.1 to 1.5 wt% of carbon short fibers with an average length of 3 mm or lower, wherein the mass ratio of the carbon short fibers to the lithium-intercalated material or the lithium-deintercalated material is 0.05 or lower.

8. A process for manufacturing a porous electrode, the process comprising:

1) preparing a slurry comprising a composition for a porous layer of the porous electrode, the composition comprising: i) 0.2 to 5.0 wt% of a block copolymer comprising a block with repeating ethylene oxide units, wherein the block copolymer has a number average molecular weight of at least 2,000; ii) 1.0 to 10.0 wt% of a fluoropolymer, wherein a mass ratio of the block copolymer to the fluoropolymer is 0.5 or lower; iii) 30.0 to 80.0 wt% of an organic solvent that is able to dissolve both the block copolymer and the fluoropolymer; iv) 2.0 to 10.0 wt% of an electrically conductive additive; and v) 10.0 to 50.0 wt% of either a lithium-intercalated material or a lithium-deintercalated material;

2) applying the slurry as a coating onto a current collector to produce a precursor electrode; and

3) exposing the precursor electrode to a non-solvent comprising water to induce a phase inversion to the precursor electrode so that a porous layer is formed onto the current collector.

9. The process of claim 8, wherein the block copolymer has a hydrophilic-lipophilic balance value of at least 12.

10. The process of claim 9, wherein the block copolymer is a triblock copolymer of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide).

11. The process of claim 8, further comprising: i) pressing a porous substrate onto a surface of the slurry after the slurry has been coated onto the current collector and before the precursor electrode is exposed to the non-solvent so that at least some of the slurry enters pores of the porous substrate; and ii) removing the porous substrate from the porous layer after the induced phase inversion so that a skin layer on the porous layer is removed along with the porous substrate.

12. The process of claim 8, further comprising drying the porous layer attached to the current collector after the induced phase inversion at a temperature below 100 °C.

13. The process of claim 12, wherein the composition further comprises 0.1 to 2.0 wt% of polyvinylpyrrolidone, and wherein a mass ratio of polyvinylpyrrolidone to the block copolymer is 1.0 or lower.

14. The process of claim 13, wherein the composition further comprises 2.0 to 37.5 wt% of a water-dissolvable compound, wherein the mass ratio of the water-dissolvable compound to the lithium-intercalated material or the lithium-deintercalated material is 1.0 or lower.

15. The process of claim 14, wherein the composition further comprises 0.1 to 1.5 wt% of carbon short fibers with an average length of 3 mm or lower, wherein a mass ratio of the carbon short fibers to the lithium-intercalated material or the lithium-deintercalated material is 0.05 or lower.

16. The process of claim 12, wherein the current collector comprises a conductive substrate and an active layer on a surface of the conducive substrate such that the slurry is coated onto the active layer of the current collector, wherein the active layer comprises a fluoropolymer and an electrically conductive additive, and wherein the active layer is unable to completely absorb a water droplet of approximately 30 microliters within ten minutes.

17. The process of claim 16, wherein the active layer further comprises the lithium-intercalated material or lithium-deintercalated material.

18. A porous electrode produced according to the process of any one of claims 8 to 16.

19. A porous electrode comprising:

1) a current collector; and

2) a porous layer attached onto the current collector, the porous layer comprising: i) a block copolymer comprising a block with repeating ethylene oxide units; ii) a fluoropolymer; iii) an electrically conductive additive; and iv) at least one of a lithium-intercalated material or a lithium-deintercalated material, wherein the block copolymer has a number average molecular weight of at least 2,000.

20. The porous electrode of claim 19, wherein the block copolymer has a hydrophilic-lipophilic balance value of at least 12.

21. The porous electrode of claim 20, wherein the block copolymer is a triblock copolymer of polyethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide).

22. The porous electrode of claim 19, wherein the current collector comprises a conductive substrate and an active layer on a surface of the conducive substrate such that the slurry is coated onto the active layer of the current collector, wherein the active layer comprises a fluoropolymer and an electrically conductive additive, and wherein the active layer is unable to completely absorb a water droplet of approximately 30 microliters within ten minutes.

23. The porous electrode of claim 22, wherein the active layer further comprises the lithium- intercalated material or a lithium-deintercalated material.

24. The porous electrode according to claim 22, wherein the porous layer has a thickness of at least 4 times than the active layer.