Triweekly Patent Update – Free Version

A positive electrode sheet for solid-state batteries incorporates a polymer interface layer on the positive active material layer to improve interfacial contact and ion transport with the solid electrolyte membrane.

The interface layer comprises an interpenetrating polymer network (IPN) of poly(1,3-propane sultone, top Figure: monomer) (polyether sulfonate, single-ion conductor) and poly(dimethylaminoethyl acrylate, bottom Figure: monomer, PDMAEA, Lewis-basic nitrogen-containing polymer) with LiTFSI (20–30 mass%). Sulfonate anions (−SO₃⁻) fixed on the polyether sulfonate backbone enable Li⁺ transference numbers approaching unity, while PDMAEA neutralizes corrosive H₂S byproducts from sulfide electrolyte decomposition.

A precursor solution of 1,3-propane sultone and dimethylaminoethyl acrylate (1 : 1 mass ratio) with MeOTf (cationic initiator), AIBN (radical initiator), and LiTFSI dissolved in anhydrous acetonitrile was blade-coated onto an NMC positive electrode (gap: 80 μm) and dried under vacuum (60°C, 2 h; 80°C, 1 h; 60°C, 12 h) to form a 30 nm interface layer via in-situ polymerization.

Cells were assembled with Li₆PS₅Cl pellets (ø12 mm, 200 MPa) and lithium metal anodes and cycled (0.1 C / 1 C, 2.4–4.25 V, 25°C). The 30 nm IPN interface layer electrode exhibits a first-cycle coulombic efficiency of 98.5%, a 2 C rate capacity retention of 64.1%, and a 300-cycle capacity retention of 91.5%, compared to 89.5%, 21.5%, and failure within 60 cycles for cells without the interface layer.

A porous carbon matrix (micropore volume proportion: 90%, BET (Brunauer–Emmett–Teller) specific surface area: 1,600 m²/g, total pore volume: 0.95 cm³/g, pores ≤5 nm: 95% of total pore volume) was placed in a PECVD (plasma-enhanced chemical vapor deposition) furnace and heated to 300°C under a vacuum degree of 3.5 × 10⁻⁴ Pa. A radio frequency plasma (13.56 MHz, 25 W) was applied.

Silane (SiH₄, 20 sccm) and hydrogen (100 sccm) were introduced at a deposition pressure of 0.133 kPa for 50 min. The silicon material deposits as a first phase (Si(111) grain size ≤0.5 nm, amorphous character, isotropic volume expansion) and a second phase (Si(111) grain size >0.5 nm, crystalline character, anisotropic volume expansion), quantified by PED (precession electron diffraction) analysis (see Figure).

The resulting anode material exhibits a first phase area proportion of 85%, a silicon grain size of 0.5 nm (XRD), a Si content of 52 mass%, a BET specific surface area of 5.3 m²/g, a D₅₀ of 12.5 μm, and a powder conductivity of 1.25 S/cm at 20 kN.

In half-cells, the anode material exhibits a discharge capacity of 2,025 mAh/g and a first cycle efficiency of 90.8% (0.1 C charge/discharge), and a capacity retention of 89.0% with an electrode thickness expansion of 39.0% after 50 cycles (1 C charge/discharge), as compared to 1,663 mAh/g, 87.9%, 84.0%, and 43.9% for a comparative material deposited at 500°C (first phase area proportion: 40%, second phase: 60%).

Figure: Processed PED phase map of the anode material (Example 3), where white regions represent the dominant first phase (amorphous silicon, ≥70% area proportion) and black regions represent the second phase (crystalline silicon, ≤30% area proportion), illustrating the predominantly amorphous character achieved through controlled PECVD conditions.

A Ni_0.6Co_0.1Mn_0.3(OH)₂ precursor was synthesized by co-precipitation (NiSO₄, CoSO₄, MnSO₄; molar ratio Ni : Co : Mn = 0.6 : 0.1 : 0.3; NaOH as precipitant, 5 h). The precursor was mixed with Li₂CO₃ (Li/Metal = 1.03) and CeO₂ (0.3 mol%) in a Henschel mixer (3,000 rpm, 30 min), then sintered (950°C, 10 h, air atmosphere) to yield single-crystal particles with an average diameter of 3–5 μm.

The sintering-promoting element Ce concentrates preferentially at the particle surface, forming a buffer layer that comprises an inner region (Ce diffused into the core interior) and an outer region (Ce remaining at the surface), as confirmed by FE-SEM EDS and Nano SIMS imaging. The buffer layer induces grain growth via Ostwald ripening, enabling single-crystal formation at lower sintering temperatures compared to undoped materials. The material exhibits an XRD (003) grain size of 380 nm, with a Ni content/grain size ratio of 0.158 mol%/nm, satisfying the ≤0.17 mol%/nm criterion defined in the claims.

In half-cells, the material exhibits a 0.1 C discharge capacity of 200.5 mAh/g and a capacity retention of 92.7% after 50 cycles (0.5 C charge / 1.0 C discharge, 4.3–4.5 V vs. Li⁺/Li, 45°C), as compared to 90.0% for undoped LiNi_0.6Co_0.1Mn_0.3O₂ sintered at the same temperature without CeO₂. The DC internal resistance increase (ΔDCIR) is 75.4%, as compared to 98.6% for the undoped material, reflecting the improved structural stability conferred by the Ce buffer layer.

A bilayer microporous layer (MPL) gas diffusion layer (GDL) was developed for proton exchange membrane fuel cells (PEMFC) combining a large-pore open-cell inner layer (B1) with a fine-pore outer layer (B2) on a carbon fiber nonwoven substrate impregnated via foulard with carbon black and PTFE binder (70 : 30 mass ratio, solid content), dried (160°C, 5 min), and sintered (400°C, 10 min).

Inner MPL layer B1 was applied by doctor blade using a paste containing PTFE binder (2.1 mass%), carbon black (4.0 mass%), graphite particles (4.0 mass%; 1 : 1 carbon black : graphite mass ratio), and spherical PMMA (polymethyl methacrylate) pore-forming particles (0.4 mass%; D90 <50 µm); coating weight 10 g/m²; dried at 120°C. Outer MPL layer B2 was applied over B1 containing PTFE binder with carbon black only or carbon black and expanded graphite (1 : 3 mass ratio); coating weight 5 g/m²; dried at 120°C. Final sintering at 400°C removes the PMMA particles from B1, generating the open-cell macroporous inner structure.

The bilayer MPL exhibits a B1 mean pore diameter of 12–100 µm by µ-CT (X-ray micro computed tomographic microscopy) and a B2 mean pore diameter of 0.005–10 µm by SEM (scanning electron microscopy) (top Figure). Claims require the largest through-pore for substrate A + B1 to be ≥30 µm and the mean pore diameter for the complete GDL to be ≤8 µm by capillary flow porometry (ASTM F-316:2003). The µ-CT cross-section confirms the two-layer architecture with large open B1 cells covered by the thin, fine-pore B2 layer (bottom Figure).

Example 2 (expanded graphite outer layer) achieves a mean pore diameter of 6.125 µm and O₂ transport resistance of 3.04 s/cm, reduced from 3.62 s/cm for comparative single-layer MPL V1. Example 1 (carbon black-only outer layer) achieves a mean pore diameter of 1.353 µm with surface roughness Ra of 2.5 µm, enabling improved electrical contact between the MPL and the catalyst layer.

B1: Inner open-cell MPL layer (large pore, pore-former-derived)
B2: Outer fine-pore MPL layer (carbon black or carbon black / expanded graphite)
Top Figure: SEM top view showing B2 outer layer with dome-shaped protrusions at locations of underlying B1 macropores
Bottom Figure: µ-CT cross-section showing bilayer MPL structure with large open B1 pores and covering B2 layer at top