Patent Description:
The present invention relates to a separating layer of an electrochemical system, in particular to a composite separating layer, which a thickness of the overall separating layer can be greatly reduced.

In the era of energy crisis and energy revolution, secondary chemical energy plays a very important role, especially metal ion batteries with high specific energy and specific power, such as sodium-ion batteries, aluminum-ion batteries, magnesium-ion batteries or lithium-ion batteries. These batteries are applied in information and consumer electronics products, and has recently expanded to the field of transportation energy.

For the metal ions batteries, the conventional separating film formed by the polymers is easily curled under high temperature. Therefore, various types of using heat-resistant materials as the reinforcement of the separating film or directly serve as the main body of the separating film are developed accordingly.

For example, in case of the separating film using a polymer material as a base material substrate and coating with a ceramic reinforcement material, which can slightly improve the thermal stability of the separating film, however the shrinkage or curling of the separating film still cannot be avoided. Alternatively, the ceramic materials are used as the main material of the separating film, and the adhesive is also used to bind the ceramic materials. Such a structure can greatly improve the thermal stability of the separating film. However, the separating film must have enough thickness (about <NUM> microns to <NUM> microns) to make the ceramic powders be stacked in multiple layers to avoid the formation of straight through holes. The relatively high thickness is the bottleneck for the separating film with structure when applied in batteries.

<CIT> provides to a multilayer electrolyte cell, in which electrolytes are configured in multiple layers by stacking polymer coating layers containing ceramic solid electrolytes and liquid electrolytes including an ionic liquid in a porous structure base. Therefore, the ceramic solid electrolyte may serve as the separator and include the porous structure base through which lithium ions may pass and the ionic liquid serving as the electrolyte.

<CIT> discloses a composite solid electrolyte, which comprises: polyethylene oxide, polyvinylidene fluoride or derivatives thereof, lithium salt and inorganic nanoparticles. The high-performance composite solid electrolyte film is suitable for all-solid-state lithium batteries to improve the solid-to-solid interface compatibility between the electrode and the electrolyte.

<CIT> provides a battery separator, which includes a ceramic layer and a first polymer electrolyte layer and a second polymer electrolyte layer which are arranged on two sides of the ceramic layer. Each of the first polymer electrolyte layer and the second polymer electrolyte layer is composed of <NUM>-<NUM>% of polymer, <NUM>-<NUM>% of ceramic powder, <NUM>-<NUM>% of lithium salt and <NUM>-<NUM>% of plasticizer. The separator has higher liquid absorption rate, ionic conductivity and fracture elongation rate.

Therefore, this invention provides an impact resistant separating layer with reduced thickness to mitigate or obviate the aforementioned problems.

It is an objective of this invention to provide a composite separating layer to greatly lower the overall thickness. Also, the composite separating layer is capable of resisting impact to prevent short circuit caused from the contacting of the positive electrode and the negative electrode due to deformations.

In order to implement the abovementioned, this invention discloses a composite separating layer, which includes a separating body and a structural reinforcing layer disposed on one side of the separating body. The separating body is characterized in that: <NUM>) with ion conductivity; <NUM>) without holes (no soft shorting would be occurred); and <NUM>) with adhesive. Therefore, the separating body is mainly composed of an ion-conductive material.

The structural reinforcing layer is disposed on one side of the separating body and is characterized in that: <NUM>) with ion conductivity; <NUM>) has a mechanical strength higher than a mechanical strength of the separating body and is not easy to deform by force; <NUM>) has higher thermal stability compared with the separating body; and <NUM>) has holes compared with the separating body. Therefore, the structural reinforcing layer is composed of an undeformable structural supporting material and a binder.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only.

The present invention will become more fully understood from the detailed description given hereinbelow illustration only, and thus are not limitative of the present invention, and wherein:.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the general inventive concept. 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 terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In the description of the present invention, it should be noted that the terms "installation", "connected", and "disposed" are to be understood broadly, and may be fixed or detachable, for example, can be mechanical or electrical, can be connected directly or indirectly, through an intermediate medium, which can be the internal connection between two components. The specific meanings of the above terms in the present invention can be understood in the specific circumstances by those skilled in the art.

Firstly, the composite separating layer of this invention is adapted for an electrochemical system, such as a lithium battery, to separate a positive electrode and a negative electrode to prevent physical contact therebetween. Please refer to <FIG>, the composite separating layer <NUM> of this invention includes a separating body <NUM> and a structural reinforcing layer <NUM> disposed on one side of the separating body <NUM>. As sown in <FIG>, it is demonstrated a side view for the separating body <NUM> of the composite separating layer <NUM>. The separating body <NUM> is essentially plate-shaped or sheet-shaped in practice, such as a rectangular parallelepiped (but not limited to). The shape of the separating body <NUM> may be modified depends on the applied electrochemical systems. Therefore, the separating body <NUM> has an upper surface and an opposite bottom surface as shown. The structural reinforcing layer <NUM> is disposed on one side (one of the surface) of the separating body <NUM>. The positional relationship does not limited to that shown in figures. The composite separating layer <NUM> can be adapted to be utilized in any orientation. A thickness of the separating body is <NUM>-<NUM> microns, and a thickness of the structural reinforcing layer is <NUM>-<NUM> microns.

Moreover, please refer to <FIG> and <FIG>, another structural reinforcing layer <NUM> may be disposed on opposite side of the separating body <NUM>, or another separating body <NUM> may be disposed on opposite side of the structural reinforcing layer <NUM>.

The separating body <NUM> of this invention is characterized in that: <NUM>) with ion conductivity; <NUM>) without holes; and <NUM>) with adhesive. Therefore, the separating body <NUM> is mainly composed of an ion-conductive material. Due to the separating body <NUM> is without holes, there is no soft shorting would be occurred. The term "without holes" means that the separating body <NUM> does not have any blind holes or through holes. Also, the separating body <NUM> is mainly composed of an ion-conductive material. Therefore, the separating body <NUM> may be formed by <NUM>% ion-conductive material, or added with certain of ceramic material. The volume content of the ion-conductive material has to be much higher than the volume content of the ceramic material. The ceramic material is selected from an oxide-based solid electrolyte or a passive ceramic material.

The adhesion of the separating body <NUM> may be achieved through the selection of the ion conductive materials. Therefore, the adhesion is improved between the separating body <NUM> and the structural reinforcing layer <NUM>, or the electrodes of the applied electrochemical system. If non-adhesive ion conductive materials are selected, the additional binder may be added in the separating body <NUM> to make the separating body <NUM> be adhesive.

The structural reinforcing layer <NUM> is characterized in that: <NUM>) with ion conductivity; <NUM>) has a higher mechanical strength and is not easy to deform by force; <NUM>) has higher thermal stability compared with the separating body <NUM>; and <NUM>) has holes compared with the separating body <NUM>.

The structural reinforcing layer <NUM> has the mechanical strength higher than the mechanical strength of the separating body <NUM> and does not deform by force. Therefore, the mechanical strength of the separating body <NUM> is improved. When the separating body <NUM> is suffered impact, the contact of the positive electrode and the negative electrode can be avoided due to the presence of the structural reinforcing layer <NUM>. The structural reinforcing layer <NUM> is composed of an undeformable structural supporting material and a binder.

The undeformable structural supporting material is a ceramic material which is selected from a passive ceramic material or an oxide-based solid electrolyte. The passive ceramic material, such as TiO<NUM>, Al<NUM>O<NUM>, SiO<NUM>, would improve the mechanical strength without ion conductivity. The oxide-based solid electrolyte is a lithium lanthanum zirconium oxide (LLZO) electrolyte or a lithium aluminum titanium phosphate (LATP) electrolyte and their derivatives. The ceramic material added with the separating body <NUM> may be the same materials.

The binder may be selected from the materials which could not transfer metal ions, such as polyvinylidene fluoride (PVDF), polyimide (PI) or polyacrylic acid (PAA). Also, the binder may be selected from the ion-conductive materials which could transfer metal ions.

On the other hand, the structural reinforcing layer <NUM> may further include a deformable electrolyte material, which is determined depended on the undeformable structural supporting material. The structural reinforcing layer <NUM> is essentially formed by stacking of the undeformable structural supporting material mixing with the binder. The holes formed thereof are filled with the deformable electrolyte material. When the undeformable structural supporting material is selected form the passive ceramic material, the deformable electrolyte material is selected from a soft-solid electrolyte, an ionic liquid, an ionic liquid electrolyte, a gel electrolyte, a liquid electrolyte or a combination thereof to fill the holes. Thus, the ionic conductively would be increased. When the undeformable structural supporting material is selected from the oxide-based solid electrolyte, the deformable electrolyte material may be added or not.

The ion-conductive material is mainly composed of a polymer base material, an additive, and an ion supplying material. The polymer base material is capable of allowing metal ions, such as lithium ions, to move inside the material. The additive is capable of dissociating metal salts, such as lithium salts, and is served as a plasticizer. Also, the ion-conductive material further includes a crystal growth inhibiting material to make the primary lattice state of the ion-conductive material be amorphous state to facilitate ion transfer.

The aforementioned polymer base material that allows metal ions, such as lithium ions, to move inside the material refers to a material that does not have metal ions, such as lithium ions, by itself (in the state of raw materials or at the beginning of the electrochemical reaction), but can transfer metal ions, such as lithium ions. For example, the polymer base material may be a linear structural material without containing salts, such as a polyethylene oxide (PEO), or the PEO already containing salts, the ions supplying material, such as PEO-LiCF<NUM>SO<NUM>, PEO-LiTFSI-Al<NUM>O<NUM> composite solid polymer, PEO-LiTFSI-<NUM>% TiO<NUM> composite solid polymer, PEO-LiTFSI-<NUM>% HNT composite solid polymer, PEO-LiTFSI-<NUM>% MMT composite solid polymer, PEO-LiTFSI-<NUM>% LGPS composite solid polymer or PEO-LiClO<NUM>-LAGP. Or in addition to be able to transfer metal ions, such as lithium ions, it is also a material that can increase the mechanical strength of the film-forming due to its cross-linked structure, such as a poly(ethylene glycol)diacrylate (PEGDA), a poly(ethylene glycol)dimethacrylate (PEGDMA), a poly(ethylene glycol) monomethylether (PEGME), a poly(ethylene glycol) dimethylether (PEGDME), a poly[ethylene oxide-co-<NUM>-(<NUM>-methoxyethoxy)ethyl glycidyl ether] (PEO/MEEGE), a hyperbranched polymer, such as a poly[bis(triethylene glycol)benzoate], or a polynitrile, such as a polyacrylonitrile (PAN), a poly(methacrylonitrile) (PMAN)or a poly(N-<NUM>-cyanoethyl)ethyleneamine) (PCEEI).

The additive, which is capable of dissociating metal salts, such as lithium salts, and is served as a plasticizer, may be selected from a plasticizer, a plastic crystal electrolytes (PCEs) or an ionic liquid, wherein the plastic crystal electrolytes (PCEs) may be a Succinonitrile (SN) [ETPTA//SN; PEO/SN; PAN/PVA-CN/SN], a N-ethyl-N-methylpyrrolidinium, [C<NUM>mpyr] + AnionsN, N-diethyl-pyrrolidinium,[C<NUM>Epyr], a quaternary alkylammonium, a n-alkyltrimethylphosphonium, [P1,<NUM>,<NUM>,n], a decamethylferro-cenium, [Fe(C<NUM>Me<NUM>)<NUM>], a <NUM>-(N,N-dimethylammonium)-<NUM>-(ammonium)ethane triflate ([DMEDAH<NUM>][Tf]<NUM>), an anions=[FSI], [FSA], [CFSA], [BETA], a LiSi(CH<NUM>)<NUM>(SO<NUM>), or a trimethy(lithium trimethylsilyl sulfate). The ionic liquid may select from an imidazolium, such as an anion / bis(trifluoromethanesulfonyl)imide, an anion / bis(fluorosulfonyl)imide, or an anion / trifluoromethanesulfonate, or an ammonium, such as an anion / bis(trifluoromethanesulfonyl)imide, or a pyrrolidinium, such as an anion / Bis(trifluoromethanesulfonyl)imide, an anion / bis(fluorosulfonyl)imide, or a piperidinium, such as an anion / bis(trifluoromethanesulfonyl)imide, an anion / bis(fluorosulfonyl)imide.

The ion supplying material may be a lithium salt, such as a LiTFSI, a LiFSI, a LiBF<NUM>, or a LiPF<NUM>.

The crystal growth inhibiting material is selected from the material for further decreasing in crystallinity, such as a poly(ethyl methacrylate) (PEMA), a poly(methyl methacrylate) (PMMA), a poly(oxyethylene), a poly (cyanoacrylate) (PCA), a polyethylene glycol (PEG), a poly(vinyl alcohol) (PVA), a polyvinyl butyral (PVB), a poly(vinyl chloride) (PVC), a PVC-PEMA, a PEO-PMMA, a poly(acrylonitrile-co-methyl methacrylate) P(AN-co-MMA), a PVA-PVdF, a PAN-PVA, a PVC-PEMA, a polycarbonates, such as a poly(ethylene oxide-co-ethylene carbonate) (PEOEC), a polyhedral oligomeric silsesquioxane (POSS), a polyethylene carbonate (PEC), a poly (propylene carbonate) (PPC), a poly(ethyl glycidyl ether carbonate) (P(Et-GEC), or a poly(t-butyl glycidyl ether carbonate) P(tBu-GEC), a cyclic carbonates, such as a poly (trimethylene carbonate) (PTMC), a polysiloxane-based, such as a polydimethylsiloxane (PDMS), a poly(dimethyl siloxane-co-ethylene oxide) P(DMS-co-EO), or a poly(siloxane-g-ethyleneoxide), a polyesters, such as an ethylene adipate, an ethylene succinate, or an ethylene malonate. Further, the crystal growth inhibiting material may be a poly(vinylidenedifluoridehexafluoropropylene) (PvdF-HFP), a poly(vinylidenedifluoride) (PvdF), or a poly(ε-caprolactone) (PCL).

When applied to the electrochemical system, please refer to <FIG>, it includes a first electrode <NUM>, a second electrode <NUM> and a composite separating layer <NUM> disposed between the first electrode <NUM> and the second electrode <NUM>. Please note that it is only illustrated the relative locations in the figure, not limited to the relative thickness. The thickness of the overall composite separating layer <NUM> of this invention is greatly reduced compared to the conventional separating layer. Also, the first electrode <NUM> may be the positive electrode or the negative electrode, and the second electrode <NUM> may be the negative electrode or the positive electrode accordingly. In other words, the separating body <NUM> of the composite separating layer <NUM> may contact to the positive electrode or the negative electrode. Due to the separating body <NUM> is adhesive, the separating body <NUM> and the electrode are bonded very well. Furthermore, although the composite separating layer <NUM> of this invention contains some materials that can provide metal ions (as described above), it is not the element that mainly supplies metal ions in the electrochemical system. The first electrode <NUM> and the second electrode <NUM> have to be contain active materials, such as a lithium metal layer, that mainly provides metal ions. The composite separating layer <NUM> plays a role to isolate the first electrode <NUM> and the second electrode <NUM> to prevent direct contact and short circuit.

Similarly, the embodiments of this invention in <FIG> can also be applied to an electrochemical system, and the repeated description is omitted for clarity. Furthermore, the first electrode <NUM> and the second electrode <NUM> shown in the foregoing figures are only for illustration, and it does not limit that they are a single-layer structure. For well-known electrochemical systems, the electrodes at least include a current collector and an active material layer.

Claim 1:
A composite separating layer (<NUM>), comprising:
a separating body (<NUM>), being ion-conductive and without holes, and mainly composed of an ion-conductive material
the ion-conductive material including:
a polymer base material, being capable of allowing metal ions to move inside;
an additive, being capable of dissociating metal salts and be served as a plasticizer;
an ion supplying material; and
a crystal growth inhibiting material to decrease in crystallinity;
and
a structural reinforcing layer (<NUM>), disposed on one side of the separating body (<NUM>) and having a mechanical strength higher than a mechanical strength of the separating body (<NUM>), wherein the structural reinforcing layer (<NUM>) is composed of an undeformable structural supporting material and a binder, the binder being an ion-conductive material including:
a polymer base material, being capable of allowing metal ions to move inside;
an additive, being capable of dissociating metal salts and be served as a plasticizer;
an ion supplying material; and
a crystal growth inhibiting material to decrease in crystallinity.