U.S. patent application number 14/986637 was filed with the patent office on 2016-04-28 for electrophoretic deposition of thin film batteries.
The applicant listed for this patent is Ramot at Tel-Aviv University Ltd.. Invention is credited to Gilat Ardel, Kathrin Freedman, Diana Golodnitsky, Roni Hadar, Hadar Mazor-Shafir, Svetlana Menkin-Bachbut, Menachem Nathan, Emanuel Peled, Tania Ripenbein.
Application Number | 20160118684 14/986637 |
Document ID | / |
Family ID | 45478379 |
Filed Date | 2016-04-28 |
United States Patent
Application |
20160118684 |
Kind Code |
A1 |
Golodnitsky; Diana ; et
al. |
April 28, 2016 |
ELECTROPHORETIC DEPOSITION OF THIN FILM BATTERIES
Abstract
Methods for forming three-layer thin-film battery (TFB)
structures by sequential electrophoretic deposition (EPD) on a
single conductive substrate. The TFBs may be two-dimensional or
three-dimensional. The sequential EPD includes EPD of a first
battery electrode followed by EPD of a porous separator on the
first electrode and by EPD of a second battery electrode on the
porous separator. In some embodiments of a Li or Li-ion TFB, the
separator includes a Li ion conducting solid. In some embodiments
of a Li or Li-ion TFB, the separator includes an inorganic porous
solid rendered ionically conductive by impregnation with a liquid
or polymer. In some embodiments, the TFBs are coated and sealed
with an EPDd PEEK layer.
Inventors: |
Golodnitsky; Diana;
(Rishon-LeZion, IL) ; Peled; Emanuel;
(Even-Yehuda, IL) ; Nathan; Menachem; (Tel-Aviv,
IL) ; Ardel; Gilat; (Givat Ada, IL) ;
Mazor-Shafir; Hadar; (Herzlia, IL) ; Hadar; Roni;
(Kibutz Gan Shmuel, IL) ; Menkin-Bachbut; Svetlana;
(Kfar-Yona, IL) ; Ripenbein; Tania; (Natanya,
IL) ; Freedman; Kathrin; (Tsoran, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ramot at Tel-Aviv University Ltd. |
Tel-Aviv |
|
IL |
|
|
Family ID: |
45478379 |
Appl. No.: |
14/986637 |
Filed: |
January 1, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13988337 |
May 19, 2013 |
9249522 |
|
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PCT/IB2011/002916 |
Dec 5, 2011 |
|
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14986637 |
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61419855 |
Dec 5, 2010 |
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Current U.S.
Class: |
429/94 |
Current CPC
Class: |
H01M 4/1397 20130101;
H01M 2/1646 20130101; H01M 10/058 20130101; H01M 2/1673 20130101;
H01M 4/0404 20130101; H01M 4/583 20130101; H01M 6/40 20130101; Y02E
60/10 20130101; H01M 4/0407 20130101; H01M 2300/002 20130101; H01M
2300/0077 20130101; H01M 2/1094 20130101; H01M 2/18 20130101; H01M
4/5825 20130101; H01M 2/0202 20130101; H01M 2/0275 20130101; H01M
2/0277 20130101; C25D 13/02 20130101; H01M 4/1393 20130101; H01M
4/133 20130101; H01M 4/366 20130101; H01M 2300/0068 20130101; H01M
10/0436 20130101; H01M 10/0562 20130101; H01M 4/0438 20130101; H01M
4/5815 20130101; H01M 2220/30 20130101; H01M 4/0457 20130101; H01M
4/587 20130101; H01M 4/136 20130101; H01M 2300/0074 20130101; H01M
10/0525 20130101 |
International
Class: |
H01M 10/058 20060101
H01M010/058; H01M 2/16 20060101 H01M002/16; H01M 2/18 20060101
H01M002/18; H01M 10/0562 20060101 H01M010/0562; H01M 4/36 20060101
H01M004/36; H01M 4/587 20060101 H01M004/587; H01M 10/0525 20060101
H01M010/0525; H01M 2/10 20060101 H01M002/10; H01M 4/58 20060101
H01M004/58 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2011 |
IB |
PCT/IB2011/002916 |
Claims
1. A thin film battery (TFB) comprising two thin-film active
material electrodes with opposite polarities separated by a
composite ceramic hybrid electrolyte separator that includes an
inorganic porous solid, at least one of the electrodes and the
separator formed inside a through-hole of a perforated substrate,
wherein the porous solid is partially penetrated by at least one of
the active material electrodes at an interface therebetween.
2. The TFB of claim 1, wherein both electrodes and the separator
are formed at least inside the through hole of the perforated
substrate.
3. The TFB of claim 1, wherein the at least one electrode and the
separator form a concentric microbattery structure.
4. The TFB of claim 2, wherein the two electrodes and the separator
form a concentric microbattery structure.
5. The TFB of claim 1, wherein the porous solid comprises ZrO.sub.2
(8% Y.sub.2O.sub.3).
6. The TFB of claim 1, wherein the porous solid is a lithium ion
conducting solid.
7. The TFB of claim 1, wherein the porous solid comprises a
glass-ceramic.
8. The TFB of claim 1, wherein the porous solid comprises
LiAlO.sub.2.
9. The TFB of claim 1, further comprising an external PEEK
coating.
10. The TFB claim 2, wherein one active material electrode
comprises LiFePO.sub.4 and the other active material electrode
comprises MCMB.
11. The TFB claim 3, wherein one active material electrode
comprises LiFePO.sub.4 and the other active material electrode
comprises MCMB.
12. The TFB claim 4, wherein one active material electrode
comprises LiFePO.sub.4 and the other active material electrode
comprises MCMB.
13. The TFB of claim 5, wherein one active material electrode
comprises LiFePO.sub.4 and the other active material electrode
comprises MCMB.
14. The TFB of claim 7, wherein the glass-ceramic
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.sub.2.
15. The TFB of claim 10, further comprising a CuS topcoat over the
LiFePO.sub.4.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation application from U.S.
patent application Ser. No. 13/988,337 filed May 19, 2013 (now
allowed) which was a National Phase application of PCT patent
application PCT/IB2011/002916, and is related to and hereby claims
the priority benefit of U.S. Provisional Patent Application No.
61/419,855 titled "Electrophoretic deposition of thin film energy
storage devices" filed Dec. 5, 2010, which is incorporated herein
by reference in its entirety.
FIELD
[0002] Embodiments disclosed herein relate generally to energy
storage devices and more particularly to electrophoretic deposition
(EPD) of thin film batteries (TFBs) in both two-dimensional (2D)
and three-dimensional (3D) configurations.
BACKGROUND
[0003] TFBs comprise a "stack" of two, one negative ("anode") and
one positive ("cathode") thin-film active material electrode layers
(referred to henceforth simply as "electrodes") separated by an
ionically conducting and electronically insulating
("non-conducting") separator layer. Hereinafter, the various
battery layers are mentioned without use of the word "layer". The
thickness of each electrode may range from sub-micrometer
("sub-micron") to a few microns. The thickness of the separator may
range from sub-micron to a few tens of microns. The stack is formed
on a substrate. If one or both electrodes are not sufficiently
electronically conductive, thin film current collectors ("CC"s) are
provided to facilitate electron current flow in an external
circuit. One such CC is formed on the substrate prior to the
formation of the TFB stack.
[0004] 3D-TFBs, as disclosed for example in U.S. Pat. No. 6,197,450
to Nathan et al., are formed inside perforations (through-holes or
cavities) of a substrate as well as on any remaining original
(planar) surface of the substrate. Each perforation may include a
partial or full stack of concentric layers forming a "concentric
microbattery" or "CMB". Such 3D-TFBs combine the known advantages
of 2D-TFBs with an order of magnitude and more increase in power
and energy per footprint (original substrate area). A general known
problem with CMBs is the difficulty of forming a solid separator
using wet chemistry. Also, known art does not teach electrochemical
deposition of a full three layer battery stack.
[0005] "Electrophoresis" refers to the motion of charged particles
in a liquid under an applied electric field. Electrophoresis can be
used to deposit materials in the form of thin films (layers),
coatings and bulk products. The deposition process is commonly
termed "electrophoretic deposition" (EPD). Reviews of EPD include
those by Van der Biest and Vandeperre, Ann. Rev. Mater. Sci., 29
(1999) 327-352 and by Corni et al., J. Europ. Ceram. Soc., 28
(2008) 1353-1367. The EPD of layers faces a hurdle in the
requirement that the solid to be deposited be available as a
colloidal suspension or powder with grains smaller that a required
layer thickness.
[0006] EPD has been used to produce bulk battery electrodes, see
e.g., Kanamura et al., Electrochemical and Solid-State Letters, 3
(2000) 259-262, and Kanamura et al., J. Power Sources, 97-98 (2001)
294-297. The use of EPD to prepare film (thick or thin) battery
components has been extremely limited, and applied mainly to
positive electrodes (cathodes). Structures and materials
investigated include thick films of LiNi.sub.0.5Mn.sub.1.5O.sub.4
[Caballero et al., J. Power Sources 158 (2005) 583-590] and
relatively thin films of Li.sub.4Ti.sub.5O.sub.12 [Sugiura et al.,
Functional Mater. Lett. 2(1) (2009) 9-12]. A general concern and
trend in the EPD of TFB electrodes it to make them dense (as
opposed to porous).
[0007] Electrophoretic assembly of electrochemical devices is also
disclosed by Chiang et al. in U.S. Pat. No. 7,662,265. Their
methods requite always use of two current collectors ("terminals")
for EPD of mutually repulsive electrodes, and cannot be used to EPD
TFBs on a single current collector.
SUMMARY
[0008] Embodiments disclosed herein provide methods to produce
partial or full thin-film battery stacks on both planar (2D) and 3D
substrates using EPD. Henceforth in this specification, the term
"EPDd" means "electrophoretically deposited". Layers of a battery
stack are EPDd in sequence on a single electronically conductive
substrate which can be either in bulk form or in film form.
Typically, the single conductive substrate also serves as a first
current collector. In some embodiments, a first polarity electrode
and a separator are EPDd in sequence to form a two-layer stack,
with a second, opposite polarity electrode added to complete a TFB
stack. In some embodiments, a "three-layer"
electrode-separator-electrode battery stack is EPDd in sequence on
a single current collector. In some embodiments, the separator
includes an electronically insulating inorganic porous solid. As
used herein, "porous solid" refers to a continuous solid structure
having porosity of varying degrees. This definition does not
inorganic solid powders dispersed in an organic matrix, where the
"solid" phase is not continuous. Advantageously, the porous solid
provides pathways for cations (e.g. protons), which lose their
positive charge (reduce) on the first polarity electrode.
[0009] In some embodiments, the inorganic porous solid is an oxide.
In some embodiments, the inorganic porous solid is a glass-ceramic.
The inventors prepared glass-ceramic powders of small enough size
(diameter) for EDP of separators inside through-holes having aspect
ratios (AR) of length to diameter greater than 1 and diameters of
exemplarily 50 .mu.m. Electrochemical deposition of conformal thin
films of glass-ceramics inside holes with AR greater than 1,
greater than 5 and even greater than 10, wherein the hole diameters
are on the order of a few tens of microns, is extremely difficult.
The inventors are unaware of any successful EPD of a glass-ceramic
layer inside through holes, or, for that matter, on planar
substrates The inventors managed to overcome significant technical
difficulties in developing EDP processes for such layers.
[0010] In some embodiments, the first polarity electrode is a
cathode and the second polarity electrode is an anode. In some
embodiments, the order of the electrodes is reversed. In some
embodiments, the EPDd two-layer or three-layer structures are
impregnated with an ion-conductive liquid (electrolyte).
[0011] In some embodiments, the single conductive substrate is a
thin-film current collector formed on a fully-perforated substrate
(having through-holes as e.g. in U.S. Pat. No. 6,197,450) or on a
semi-perforated substrate (with non-through-holes, as e.g. in U.S.
Pat. No. 7,772,800). As used herein, the term "through-hole"
indicates a perforation of any shape which extends between and
penetrates two opposite and substantially planar surfaces bounding
a substrate. Non-limiting examples of through-holes may be found in
Averbuch et al., J. Power Sources, 196 (2011) 1521-1529. A TFB in
which a three-layer stack is inserted in substrate holes is a
"full-3D" TFB. A TFB in which only two layers of a three-layer
stack are inserted in substrate holes is a "semi-3D" TFB.
[0012] In some embodiments, a separator and/or second electrode may
be EPDd on a first electrode which is formed by another method. For
example, in one embodiment, a separator and/or an anode may be EPDd
on an electrodeposited CuS or MoS cathode, on both planar and 3D
perforated substrates.
[0013] In some embodiments, an EPDd TFB disclosed herein is a
Li-ion TFB. In some embodiments of a semi-3D or full-3D EPDd Li-ion
TFB, the cathode is made of a lithiated metal phosphate. In
particular embodiments, the lithiated metal phosphate is
LiFePO.sub.4 (henceforth referred to as "LFP"). In some
embodiments, the separator is in the form of a composite solid
thin-film electrolyte or a composite ceramic hybrid electrolyte. In
the hybrid electrolyte, ionic conductivity may be provided by
impregnating an inorganic porous solid with a liquid, for example
EC/DEC 1M LiPF6. In some embodiments in which the ion-conducting
electrolyte is a non-impregnated composite solid, the porous solid
is sintered after the formation of the anode layer, with the goal
of decreasing porosity and grain-boundary resistance. In some
embodiments which provide a "solid state TFB", the sintering is
applied to the entire battery structure.
[0014] In some embodiments, the anode includes graphite or
meso-carbon micro-beads (MCMB), or nanotubes. In other embodiments,
the anode includes nano-silicon. In some embodiments, the anode
and/or the cathode may be co-deposited with an electronically
conducting material, such as carbon or/and graphite powders.
[0015] Particles useful in the EPD of TFB structures described
herein can be in the nanometer to micrometer range. Large particles
can be ball-milled to small diameters, down to submicron and even
nanometer range. In some embodiments, an EPDd layer includes two or
more types of different micro- and nano-sized particles. In some
embodiments, the particle size is less than 10 .mu.m. In some
embodiments, the particles size is less than 1 .mu.m. In some
embodiments, the particle size is less than 100 nm.
[0016] In some embodiments, the anode and/or cathode powders may be
pre-coated by one or more (e.g. up to 10) monolayers of carbon
prior to EPD. In some embodiments, EPDd 2D-TFBs and 3D-TFBs are
coated and sealed with an EPDd PEEK packaging layer. Additional
polymers that can be EPDd to serve as battery packaging layer
include Nylon-MXD6 (a copolymer of m-Xylyenediamine and Adipic
acid), PVDC (plasticized Vinylidene Chloride copolymer) and EVOH
copolymer (Ethylene Vinyl Alcohol copolymer).
[0017] 2D-TFBs according to embodiments disclosed herein may be
formed on large (a few square inches to a few square meters) to
very large (a few tens of square meters) surfaces, which need not
be flat. Such 2D-TFBs may be formed on any conductive surface or
non-conductive surface coated with a conductive layer which serves
as current collector/deposition electrode.
[0018] Suitable positive electrode (cathode) materials include
ordered rock-salt compounds such as LiCoO.sub.2, LiNiO.sub.2,
Li(Al, Ni, Mn)O.sub.2, LiMnO.sub.2, and solid solutions or doped
combinations thereof; spinel structure compounds such as
LiMn.sub.2O.sub.4 and its doped counterparts or solid solutions
with other metal oxides; ordered olivines such as LiFePO.sub.4,
LiMnPO.sub.4, LiCoPO.sub.4, and their doped counterparts or solid
solutions; and other ordered transition metal phosphates such as
those of so-called Nasicon structure type and their derivatives and
related structures.
[0019] Suitable negative electrode (anode) materials include
compounds such as graphitic or disordered carbons; metal oxides
that intercalate lithium such as Li.sub.4Ti.sub.5O.sub.12 spinel
and its derivatives; and other metal oxides or their solid
solutions that undergo intercalation or displacement reactions such
as tin oxide, indium tin oxide, or first-row transition metal
oxides; and crystalline or amorphous metals and alloys of metals or
metalloids such as Si, Al, Zn, Sn, Ag, Sb, and Bi.
[0020] Suitable composite ceramic hybrid electrolyte materials
include ceramic powders like ZrO.sub.2, Zr.sub.2O.sub.3, SiO.sub.2,
Al.sub.2O.sub.3, LiAlO.sub.2 and polymer binders like PEO,
polyethylenimine (PEI), polyvinyldiene fluoride (PVDF), PEG, PMMA,
methylcellulose, alkyd resin, dewaxed shellac, polyvinyl butyral
(PVB), polyvinyl alcohol (PVA) and poly(dimethyldiallylammonium
chloride) (PDDA). The ceramic material is impregnated with a liquid
electrolyte typically used for lithium-ion batteries. Exemplarily,
the liquid electrolyte may be LiPF.sub.6:EC:DEC.
[0021] Suitable inorganic solid separator materials include
lithium-ion conductive glasses such as lithium zirconate, lithium
aluminate, lithium silicate,
LiCl--Li.sub.2O--SiO.sub.2--P.sub.2O.sub.5,
LiCl--Li.sub.2O--SiO.sub.2--P.sub.2O.sub.5, sulfide-based glasses
like Li.sub.2S--SiS.sub.2--Al.sub.2S.sub.3 and
Li.sub.2S--SiS.sub.2--P.sub.2S.sub.5,
Li.sub.2S--SiS.sub.2--Li.sub.3N, lithiated boron oxide glasses of
the family xLi.sub.2O--B.sub.2O.sub.3 and lithium ion conducting
glass ceramics like
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.sub.2--GeO.sub-
.2 and
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--T.sub.2O.sub-
.2. The solid electrolyte layers are preferably 1 to 10 .mu.m thick
to eliminate high ohmic resistance at RT. Alternatively, they can
be thicker than about 10 .mu.m if used at elevated temperatures
(such as 60-70 C).
[0022] Suitable solvents for use in the EPD of various materials
may be found for example in Table 3 of L. Besra and M. Liu,
Progress in Materials Science, 52 (2007) 1-61.
[0023] The electrophoretic deposition may be enhanced by use of
additives. Useful additives include but are not limited to
conductive particles that increase the electrical conductivity of
the deposited material, such as conductive carbon, metallic
particles, or conductive polymer dispersions, or binders that
improve the adherence of the deposited particles to each other or
to a current collector. Other exemplary additives which may be used
for this purpose are described for example in U.S. Pat. No.
7,662,265.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Aspects, embodiments and features disclosed herein will
become apparent from the following detailed description when
considered in conjunction with the accompanying drawings. In the
drawings:
[0025] FIG. 1 is a low magnification SEM view of a YSZ separator
EPDd on a previously EPDd LFP cathode in a planar
configuration;
[0026] FIG. 2 shows high resolution SEM views at different
magnifications of the YSZ layer in FIG. 1;
[0027] FIG. 3A shows charge-discharge curves of an assembly of EPDd
planar LFP cathode/YSZ LiPF6 EC:DEC VC tested in a coin cell
configuration with a Li foil serving as anode;
[0028] FIG. 3B shows cycling results of the assembly in FIG.
3A;
[0029] FIG. 4A shows an SEM image of a YSZ-PEI membrane deposited
by EPD on a previously EPDd MCMB anode in a planar
configuration;
[0030] FIG. 4B shows SEM images of YSZ-PEI membranes EPDd from an
acidic suspension (pH2) containing 10% PEI without iodine;
[0031] FIG. 5 shows SEM images of LiAlO.sub.2-PEG membranes EPDd on
a previously EPDd MCMB anode;
[0032] FIG. 6A shows charge-discharge curves of an assembly of EPDd
planar assembly MCMB/(LiAlO2)-15% PEG LiPF6 EC:DEC/Li and of a cell
with a commercial Celgard membrane for comparison;
[0033] FIG. 6B shows cyclability data for the MCMB/(LiAlO2)-15% PEG
LiPF6 EC:DEC/Li cell in FIG. 6A;
[0034] FIG. 7 shows details of the layers in a cross section of an
EPDd three-layer LFP/YSZ/MCMB stack on a single planar conductive
substrate;
[0035] FIG. 8 shows a tilted cross-section SEM view of a perforated
3D Si substrate coated with Au and an EPDd two-layer LFP-YSZ (PEI)
structure;
[0036] FIG. 9A shows polarization curves of 2D and semi-3D cells
with EPDd LFP cathode modified with CuS;
[0037] FIG. 9B shows cyclability data of 2D and semi-3D cells with
EPDd LFP cathode modified with CuS.
DETAILED DESCRIPTION
[0038] The inventors found surprisingly that three-layer (first
electrode/separator/second electrode) thin film battery stacks can
be EPDd in sequence on a single conductive substrate in both 2D and
3D configurations. The conductive substrate may be a metal or a
thin-film current collector deposited on a non-conducting substrate
(e.g. plastic or glass) or on a semiconductor substrate (like
silicon). In some embodiments, an electrode may be electrically
conductive enough to serve as current collector. If necessary, a
second current collector is provided to form a full energy storage
cell, which can be packaged in various packages. In some
embodiments, the separator includes an inorganic porous solid,
which, as mentioned, provides pathways for cations which reduce on
the first EPDd electrode. Its porosity depends on the deposition
conditions and may vary from 20-80%. In some embodiments, the
porous solid is impregnated with an ion-conductive electrolyte to
provide a "composite ceramic electrolyte". Exemplarily, the
electrolyte may be LiPF.sub.6:EC:DEC with a 2% volume VC (vinylene
carbonate) solution, or a N-methyl-N-propylpyrrolidinium
bis(trifluoromethanesulfonyl)imide (PYR.sub.13TFSI) RT ionic liquid
(IL) and LiTFSI salt. The impregnation is carried out after the
deposition of the entire battery stack. In other embodiments, the
separator is a composite solid thin-film electrolyte which includes
Li ion conducting, but electronically non-conducting crystalline
materials (such as oxide perovskites,
La.sub.0.5Li.sub.0.5TiO.sub.3, thio-LISICON,
Li.sub.3.25Ge.sub.0.25P.sub.0.75S.sub.4, glass-ceramics, glassy
materials (e.g. Li.sub.2S--SiS.sub.2--Li.sub.3PO.sub.4),
Li.sub.10GeP.sub.2S.sub.12, lithium sulfide, lithium iodide,
lithium nitride and/or a mixture thereof. In particular, a wide
variety of glass ceramic systems useful as ion-conducting
separators exist, for example the Li.sub.2O x Al.sub.2O.sub.3x
nSiO.sub.2-system (LAS-system), the MgO x Al.sub.2O.sub.3 x
nSiO.sub.12-system (MAS-system) and the ZnO x Al.sub.2O.sub.3 x
nSiO.sub.2-System (ZAS-system). Note that after EPD, all separators
are porous (i.e. include a porous solid) in order to enable further
EPD of a second electrode. The porosity of a Li-ion conducting
solid separator may be reduced significantly by additional
sintering.
[0039] The EPDd first electrode can serve as a deposition electrode
for the EPD of an electronically insulating and ionically
conducting separator. Unexpectedly and advantageously, the first
electrode/separator stack was found able to serve as a deposition
electrode in the EPD of the second electrode. This is enabled by
the porosity of the separator solid, which allows cation (proton)
motion to the first electrode. In some embodiments, the porous
separator was EPDd as a conformal layer on a first electrode
previously EPDd inside holes of a perforated substrate. Thus,
previously unachievable and unknown conformal separators which
include a porous solid could be obtained for semi-3D and full-3D
TFB configurations (i.e. CMBs) inside perforated substrates. Even
more surprisingly, the inventors found that the second electrode
could be EPDd as a conformal layer over the conformal separator
above, i.e. all three layers could be EPDd in sequence inside
perforations. That is, concentric microbatteries (CMBs) inside
holes could be formed entirely by EPD. In some embodiments, the
inventors found that the porous separator EPDd inside holes could
be sintered and used for ionic conduction without impregnation by
an ionically conducting liquid.
[0040] The following examples illustrate the sequential EPD of
two-layer and three-layer TFB stacks on a single conductive
substrate in both 2D and 3D configurations, and 2D-TFBs and 3D-TFBs
obtained by EPD.
Example 1
Two-Layer LiFePO.sub.4/ZrO.sub.2 (8% Y.sub.2O.sub.3).sub.2Stack on
a Planar Substrate
[0041] A two-layer LFP/ZrO.sub.2 (8% Y.sub.2O.sub.3) stack was
prepared by EPD on a planar substrate. ZrO.sub.2 (8%
Y.sub.2O.sub.3) will be referred to henceforth as "YSZ". FIG. 1
shows a low magnification SEM view of the YSZ layer, having a
porosity of between 40-50%. FIG. 2 shows high-resolution SEM images
of the same layer at different magnifications.
[0042] LFP powder (Hydro Quebec, Canada), black-pearl carbon (BP)
and PVDF were dispersed in an acetone solution with 0.28 mg/L. The
weight percentage ratio of LFP:BP:PVDF was (91:4:5%). In one case,
0.4% v/v polymer triton-X 100 (TTX,
(C.sub.14H.sub.22O(C.sub.2H.sub.4O)n)) was added to the dispersion.
Black-pearl carbon and PVDF were used as conducting and binding
materials, respectively. The modification of the film with TTX
caused smoother and more homogeneous deposition during the EPD
process. The addition of iodine produces charged particles
(protons) in the solution through chemical reaction of I.sub.2 with
acetone. The reaction may be written as follows:
CH.sub.3COCH.sub.3CH.sub.3C(OH)CH.sub.2
CH.sub.3C(OH)CH.sub.2+I.sub.2.fwdarw.CH.sub.3COCH.sub.2I+H.sup.++I.sup.-
A nickel disk was used as a substrate (working electrode) and a
graphite plate was used as a counter electrode. The constant
voltage applied between the two electrodes was set at 60V for 60
seconds. The mass of the EPDd LFP deposit was 9 mg.
[0043] The YSZ membrane was prepared by cathodic EPD on the LFP
cathode (which served as working electrode), using a deposition
bath with the following composition: 250 ml Ethanol, 0.7 gr YSZ, 4
ml Acetone, 2 ml water, 0.4 ml Acetylacetone, 0.027 gr Iodine and
0.0105 gr PEI (PolyEthylene Imine). As before, the graphite plate
served as counter electrode. The working distance between the
electrodes was 15 mm. The deposition solution preparation was
carried in two steps: preparation of solution 1 containing 150 ml
Ethanol, 0.4 ml Acetylacetone and 0.7 gr YSZ in one container and
stirring overnight; and preparation of solution 2 containing 100 ml
Ethanol, 2 ml de-ionized water, 4 ml acetone and 0.027 gr iodine
and stirring for a few minutes. Solutions 1 and 2 where then mixed
and placed in an ultrasonic bath. EPD was carried out at room
temperature (RT) and atmospheric conditions using a Keithley 2400
source-meter. The addition of iodine produced protons in the
solution, as explained above. Some of the protons were adsorbed on
the ZrO.sub.2 particles, rendering them positively charged. The
addition of PEI to the solution helped to obtain a smoother,
adherent film. The YSZ deposition was carried out at a constant
current of 1.6 mA/cm.sup.2 for 10 minutes, and resulted in a highly
adherent conformal deposit on the LFP cathode.
[0044] A LFP cathode/YSZ-PEI assembly EPDd as above was tested in a
coin cell configuration, with a Li foil serving as anode. The
YSZ-PEI membrane was impregnated with LiPF.sub.6:EC:DEC electrolyte
with an added 2% volume VC solution. The VC solution improves solid
electrolyte interphase (SEI) properties. The configuration was
sealed in a stainless steel coin cell. The Li/YSZ/LFP cells were
cycled at RT using a Maccor series 2000 battery test system.
Charge-discharge curves and cycling results are shown in FIGS. 3A
and 3B. The voltage cut-off was 2.8 to 3.5V, with a
charge/discharge at a current density of 75 .mu.A/cm.sup.2. The
cells provided 0.1-0.2 mAh/cm.sup.2 capacity for more than 50
reversible cycles. The Faradaic efficiency was close to 100%.
Example 2
Two-layer LiFePO.sub.4/LiAlO.sub.2 Stack on a Planar Substrate
[0045] A two-layer LFP/LiAlO.sub.2 stack was prepared by EPD on a
Ni planar current collector substrate. First, the LFP cathode was
deposited as in Example 1. The LiAlO.sub.2 membrane was then
deposited by cathodic EPD on the LFP, using a deposition bath with
the following composition: 250 ml Ethanol, 0.7 gr LiAlO.sub.2, 4 ml
Acetone, 2 ml water, 0.4 m1 Acetylacetone, 0.027 gr Iodine and
0.0105 gr PEI. The deposition solution preparation was carried in
two steps: preparation of solution 1 containing 150 ml Ethanol, 0.5
m1 Acetylacetone and 0.8 gr LiAlO.sub.2 in one container with
overnight stirring, and preparation of solution 2 containing 100 ml
Ethanol, 3 ml deionized water, 4.5 ml acetone and 0.035 gr iodine
with stirring for a few minutes. Solutions 1 and 2 where then mixed
and placed in an ultrasonic bath for 20 minutes. 0.0105 gr of PEI
was then added to the mixed solution.
[0046] The EPD of LiAlO.sub.2 was carried out at RT under
atmospheric conditions using a Keithley 2400 source-meter, with the
LFP as working electrode and a graphite plate distanced 15 mm
therefrom as counter electrode. The LiAlO.sub.2 EPD was carried out
at a constant current of 1.6 mA/cm.sup.2 for 10 minutes. The result
was a highly adherent conformal LiAlO.sub.2 deposit. LiImide:PEG500
electrolyte was then dripped onto the surface of the LiAlO.sub.2
and the materials dried.
[0047] The two-layer LiFePO.sub.4/LiAlO.sub.2 stack was soaked in
LiImide:PEG500 liquid electrolyte under vacuum for 30 min and left
overnight in the solution. An assembly of EPDd LFP
cathode/LiAlO.sub.2-LiImide:PEG500 was tested in a coin cell
configuration with a Li foil serving as anode. The configuration
was sealed in a stainless steel coin cell. The Li/LiAlO.sub.2/LFP
cells were cycled at RT using a Maccor series 2000 battery test
system and exhibited the typical behavior of a Li TFB.
Example 3
Two-Layer MCMB/YSZ Stack on a Planar Substrate
[0048] A MCMB anode was deposited by cathodic EPD on a Ni current
collector using a deposition bath with the following composition:
250 ml Ethanol, 0.9 gr MCMB, 4.5 ml Acetone, 2 ml water, 0.5 ml
Acetylacetone, 0.05 gr Iodine and 0.008 gr PEI. The deposition
solution preparation was carried in two steps: preparation of
solution 1 containing 150 ml Ethanol, 0.4 ml Acetylacetone and 0.7
gr MCMB in one container with stirring for a few minutes; and
preparation of solution 2 containing 100 ml Ethanol, 2 ml deionized
water, 4 ml Acetone and 0.05 gr Iodine with stirring for a few
minutes. Solutions 1 and 2 where then mixed and placed in an
ultrasonic bath for 20 minutes. 0.007 gr of PEI was then added to
the solution. EPD was carried out using the Keithley 2400
source-meter at RT under atmospheric conditions, at a constant
voltage of 100V for 120 seconds. The YSZ separator layer was
prepared as in Example 1, providing a highly adherent conformal
deposit on the MCMB. The resulting membrane structure is shown in
FIG. 4A. FIG. 4B shows SEM images of two-layer MCMB-membrane stack
with a YSZ-PEI membrane EPDd from an acidic suspension (pH 2)
containing 10% PEI. The YSZ-PEI deposition was performed at 200V
using 5-10 pulses of 10 s each. Lowering of the pH enabled using a
solution without iodide for EPD.
Example 4
Two-Layer MCMB/LiAlO.sub.2 Stack on Planar Substrate
[0049] A MCMB anode was deposited by cathodic EPD on a Ni current
collector as in Example 3. A LiAlO.sub.2 membrane was deposited on
the MCMB anode using the electrolyte described in Example 2. 10%
(v/v) PEGDME was added to the suspension. The membrane was
deposited by pulse potential cathodic EPD. The applied voltage was
100V and the deposition was carried out stepwise. The duration of
each step was 30 sec. Between the deposition steps, the sample was
removed from the suspension and dried under ambient conditions
until complete evaporation of the solvent.
[0050] FIG. 5 shows SEM views of LiAlO.sub.2-based membranes
deposited by EPD from suspensions containing two different
concentrations (15% and 50%) of PEG-polymer binder. A wide
concentration range of polymer can be used in the suspension.
Better uniformity and porosity can be achieved when the suspension
contains 15% PEG. TGA tests indicated that the polymer
concentration in the EPD layers did not exceed 3.5-5.5%.
[0051] An assembly of EPDd MCMB anode/LiAlO.sub.2-PEG with
LiPF.sub.6:EC:DEC 2% VC was tested in a coin cell configuration
with a Li foil serving as counter electrode. The configuration was
sealed in a stainless steel coin cell. FIG. 6A shows a discharge
curve of the Li/LiAlO.sub.2-15% PEG/MCMB cell. FIG. 6B shows
cyclability data for this cell. The comparison of the cell voltage
profile with that of a similar cell including a commercial Celgard
membrane proves the feasibility of using the disclosed membrane for
Li-ion cells.
Example 5
Three-Layer LiFePO.sub.4/YSZ/MCMB Stack on Planar Substrate
[0052] A three-layer LFP/YSZ/MCMB stack was prepared by EPD on a
planar Ni current collector. All three layers were EPDd in sequence
on the single Ni current collector. The cathode and separator
layers were EPDd as in Example 1. The MCMB anode was subsequently
deposited by cathodic EPD on the YSZ using a deposition bath
described in Example 3. The Ni/LFP/YSZ assembly was used as working
electrode and a graphite plate was used as a counter electrode,
with a working distance of 15 mm between the electrodes. The
inventors found that unexpectedly, while YSZ is an electronically
non-conductive separator, its high porosity (here ca. 60%) enables
high proton mobility inside pores and hydrogen evolution reaction
on the electronically conducting Ni/LFP surface, assisting the EPD
of the MCMB layer. The MCMB is electronically conductive enough to
also serve as an anode current collector.
[0053] FIG. 7 shows a cross section of the EPDd three-layer
LFP/YSZ/MCMB stack. One can get a rough measure of both layer
thicknesses and layer porosities. Here, the separator thickness is
roughly 110-120 .mu.m, the thickness of the MCMB anode is roughly
80-90 .mu.m and the thickness of the cathode LFP is roughly 70-80
.mu.m. In general, the thickness of each layer can be controlled by
(among others) controlling the deposition time, and can be made
much thinner. Specifically, the YSZ separator may be made thinner
than 10 .mu.m, thinner than 5 .mu.m and even thinner than 2
.mu.m.
Example 6
Two-Layer LiFePO.sub.4/YSZ Stack on Perforated (3D) Substrate
[0054] A two-layer LFP/YSZ stack was prepared by EPD on a 3D
perforated substrate which had a previously electrolessly deposited
thin (1-2 .mu.m) Au layer on all available surfaces. A tilted SEM
picture of the stack is shown in FIG. 8. The two-layer LFP/YSZ
stack was EPDd inside 50 .mu.m diameter holes in a 500 .mu.m thick
silicon substrate as well as on all remaining planar surfaces. The
hole aspect ratio (length/diameter) was 10:1. The preparation of
the solution and deposition of the LFP were performed as in Example
1, except that two graphite plate counter electrodes were
positioned in parallel, one on each side of the Si substrate, each
at a distance of ca. 15 mm from a respective surface of the Si. The
preparation of the solution and the deposition of the YSZ layer
were also performed as in Example 1. The thickness of the separator
so formed was about 10 .mu.m.
[0055] The 3D LFP/YSZ stack was tested in a coin cell configuration
with a Li foil serving as anode. This configuration forms a
so-called "semi-3D" TFB. The Li foil was brought into an intimate
contact with the YSZ on the top surface of the substrate. The
electrolyte was LiPF.sub.6:EC:DEC with a 2% volume VC solution. The
configuration was sealed in a stainless steel coin cell. The
Li/YSZ/LFP cells were tested at RT using a Maccor series 2000
battery test system. A stable OCV of 3.6V was measured. The testing
proved that the assembly performs as a Li battery.
Example 7
Three-Layer LiFePO.sub.4/YSZ/MCMB Stack on Perforated (3D)
Substrate
[0056] A three-layer LFP/YSZ/MCMB stack was prepared by EPD on a 3D
perforated substrate. First, a LFP/YSZ stack was prepared on a Ni
coated Si perforated substrate as in Example 1. Two graphite plate
counter electrodes were positioned in parallel, one on each side of
the Si substrate, each at a distance of ca. 15 mm from a respective
surface of the Si. A MCMB anode was subsequently deposited by
cathodic EPD on the YSZ as in Example 3. The MCMB was
electronically conductive enough to also serve as anode current
collector. The resulting structure was one of a concentric
electrode/separator/electrode stack formed in each hole in the
perforated substrate and also formed on the remaining planar
surfaces of the substrate. This configuration forms a so-called
"full-3D" TFB.
Example 8
Improvement of LiFePO.sub.4 Conductivity
[0057] A topcoat material with high mixed electron/ion conductivity
(exemplarily copper sulfide (CuS)) was used to improve the
conductivity of composite LFP electrodes prepared by EPD. CuS was
electrochemically synthesized on the EPDd LFP cathode with the use
of procedure described in H. Mazor et al., Electrochemical and
Solid-State Letters, 12, (2009), A232-A235. The CuS was deposited
on both 2D and 3D Si substrates over the LFP. Planar and semi-3D
cells comprising an Au cathode current collector, an EPDd LFP
cathode modified by CuS layer, a Celgard separator soaked in
commercial electrolyte (LiPF.sub.6 in 1:1 EC:DEC) and a lithium
anode were assembled and tested. As shown in FIG. 9A, a semi-3D
cell exhibited a 1.5-2.3 mAhcm.sup.-2 (per battery footprint)
reversible capacity. The capacity values were stable for 100 cycles
with a degradation rate of 0.01% capacity loss per cycle. The
capacity of the planar cell was 10 times lower. This agrees with
the geometrical-area gain (AG=9) of the perforated Si
substrate.
[0058] FIG. 9B shows polarization curves of 2D and semi-3D cells
with EPDd LFP cathode modified by CuS. Both cathodes were deposited
under similar conditions and both contained LFP, black-pearl
carbon, PVDF binder (ratio 91:4:5%(w/w)) and TTX-100. The pulse
duration was one second followed by a rest period of 20 seconds. As
can be seen from the graph, the transition from 2D to 3D
architecture is followed by an increase in maximum current-density
capability from 30 to 75 mAcm.sup.-2. The semi-3D cells with
CuS-coated modified LFP electrodes were able to provide more than
85 mAcm.sup.-2 current density and 204 mWcm.sup.-2 peak power per
battery footprint, a 24% increase over the semi-3D non-CuS coated
LFP cell and a significant enhancement in comparison with the 2D
LFP cell.
Example 9
Three-Layer
LiFePO.sub.4/Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.s-
ub.2/MCMB Stack on Planar Substrate
[0059] A 3-layer planar
LFP/Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.sub.2/MCMB
structure with solid electrolyte was EPDd on a single Ni current
collector. The LFP layer was deposited as in Example 1. The
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.sub.2 is
a glass-ceramic available commercially in powder form from OHARA
Ltd, and described exemplarily in US patent application
20080289365. The powder was ball-milled for 24 hours before
preparation of the suspension for EPD. The
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.sub.2
was then EPDd under the same conditions as the LiAlO.sub.2 in the
Example 2. The MCMB anode was then EPDd as in Example 3 on the
LFP/glass-ceramic stack.
Example 10
Three-Layer MCMB/LiAlO.sub.2/LFP Stack on Perforated Si Substrate
Coated by Ni Current Collector
[0060] A MCMB anode was deposited by cathodic EPD on a
3D-perforated Si substrate coated by Ni current collector. The
thickness of nickel layer was 5 .mu.m to eliminate co-intercalation
of lithium to the silicon substrate trough pits of Ni. A MCMB anode
was deposited as in Example 3. A LiAlO.sub.2 membrane was deposited
on the MCMB anode using the electrolyte described in Examples 2 and
4. The LFP cathode was EPDd on the LiAlO.sub.2 membrane-PEG
membrane using the procedure described for LFP in the Example 1. A
3D-assembly of EPDd MCMB anode/LiAlO.sub.2-PEG/LFP with impregnated
LiPF.sub.6:EC:DEC 2% VC was tested in a coin cell configuration.
The configuration was sealed in a stainless steel coin cell.
Example 11
EPD of PEEK Protective and Pre-Packaging Layer
[0061] A polyaromatic, semicrystalline thermoplastic polymer,
Polyetheretherketone (PEEK),
(--C.sub.6H.sub.4--O--C.sub.6H.sub.4--O--C.sub.6H.sub.4--CO--)n,
was electrophoretically deposited on the
LFP/Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.sub.2/MCMB
structure prepared as in Example 9. A Ni coated substrate was
placed in the EPD bath as a cathode between two graphite plates
connected to the anode CC. PEEK suspensions were prepared by
magnetic stirring of 2 g PEEK powder (Victrex, UK) in 250 mL
ethanol. The stirring was conducted for 3 hours, followed by 30 min
ultrasonic treatment. The suspension was mixed with the second bath
containing 4 ml Acetone, 2 ml water, 0.5 ml Acetylacetone and 0.04
gr Iodine. An additional 30 min ultrasonic treatment was then
carried out. A small area surrounding the current collector
contacts was shielded. PEEK EPD was carried our at an applied
voltage was 140V stepwise with 30 sec per step. The as-deposited
PEEK layer was porous. The final
PEEK/Ni/LFP/Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2--P.sub.2O.sub.5--TiO.su-
b.2/MCMB/PEEK structure was dried in vacuum at 100 C for 7 hours.
After drying, the sample was heated at 350 C for 20 minutes to
provide a dense PEEK polymer coating, which serves as a protective
and pre-packaging layer of the battery to eliminate penetration of
moisture and oxygen.
[0062] While this disclosure describes a limited number of
embodiments, it will be appreciated that many variations,
modifications and other applications of such embodiments may be
made. The disclosure is to be understood as not limited by the
specific embodiments described herein, but only by the scope of the
appended claims.
[0063] All patents, patent applications and publications mentioned
in this specification are herein incorporated in their entirety by
reference into the specification, to the same extent as if each
individual patent, patent application or publication was
specifically and individually indicated to be incorporated herein
by reference. In addition, citation or identification of any
reference in this application shall not be construed as an
admission that such reference is available as prior art.
* * * * *