Triweekly Patent Update – Free Version

A solid-state battery with enhanced cycling stability was developed by incorporating a porous graphene functional layer between the negative electrode and solid electrolyte (Li₆PS₅Cl, see Figure). The battery comprises a positive electrode layer, negative electrode layer, functional layer on at least one surface of the negative electrode, and solid electrolyte layer between the functional layer and positive electrode.

The functional layer includes porous graphene-like materials with individual sheet porosity of 3-9% and average pore diameter of 0.2-15 nm. At ≤10% state of charge (SOC), the porous graphene-like material comprises 91-100 mass% of the functional layer.

Porous reduced graphene oxide was synthesized by oxidizing graphene powder (average flake diameter: 50 μm, average thickness: 2 nm) in mixed oxidizing solution containing hydrogen peroxide solution (20%) and ammonia solution (25%) at 40°C for 1.5 h, followed by reduction with hydrazine hydrate at 90°C for 2 h. The resulting material (5% individual sheet porosity, 2 nm average pore diameter, 50 μm average flake diameter) was spin-coated onto copper foil to form a 300 nm functional layer.

Full cells with NCM811 positive electrodes and lithium metal negative electrodes exhibit 82% capacity retention after 200 cycles (0.5 C charge/discharge, 25°C, 2-4.35 V).

1211: positive electrode current collector
1212: positive electrode active layer
122: solid electrolyte layer
124: functional layer
1231: negative electrode current collector
1232: negative electrode active layer

Porous carbon (BET surface area: 1,940 m²/g, pore volume: 1 cm³/g) was heated to 150°C under nitrogen flow. The material contains OH groups and C_xH_y groups at active sites, with CO gas detected at ≈8,000 ppm in the exhaust.

Monosilane gas was introduced at 365-380°C under pressurized atmosphere (50 kPa). CO gas from active sites enables low-temperature monosilane decomposition, depositing silicon oxide with dangling bonds. Oxygen atoms from active sites bond with silicon, forming Si-O structures internally.

After cooling, oxidation was performed under 20 kPa pressurized atmosphere using nitrogen-diluted oxygen (1 mass% O₂), creating low-valence nano-silicon oxide with a defect-rich SiO_x structure at the surface. The material was then heat-treated to partially crystallize the Si.

The material was heated to 600°C to form Si-C bonds in the bulk interior. Carbon layer deposition was performed at 580°C using acetylene gas under reduced pressure (10 kPa, 8 h). At the interface, oxygen transfer creates C=O or C-O bonds.

The material exhibits an Si grain size of 4.6 nm. In half-cells, the material exhibits a discharge capacity of 1,860 mAh/g, initial efficiency of 89%, and 1,000-cycle retention of 81%. ²⁹Si MAS-NMR analysis confirms the presence of both Si-C bonds and amorphous Si / low-valence silicon oxide (see Figure).

Si-C: Si-C bonds
非晶質Si: Amorphous Si

A hydroxide precursor Ni_0.96Co_0.01Mn_0.03(OH)₂ was synthesized via co-precipitation (50-60°C, pH 10-12, 1,000 rpm). The precursor was mixed with LiOH (Li to transition metal molar ratio of 1.01), Al(OH)₃ (0.1 mol), ZrO₂ (0.1 mol), and deionized water (3-6 mass%), followed by compression molding (see Figure).

The molded bodies were sintered in a roller hearth kiln without using sintering vessels (oxygen atmosphere, ramp to 700-900°C, hold 8-10 h) to obtain Ni_0.966Co_0.01Mn_0.03O₂ doped with Zr and Al. The sintered bodies were crushed using a jet mill (1.2-2 bar) to obtain cathode active material powder comprising single particles.

The material exhibits an XRD (003) plane grain size of 237 nm compared to 85-91 nm for comparative material.

In half-cells, the material exhibits a discharge capacity of 214.5 mAh/g (0.2 C, 25°C, 2.5-4.25 V vs. Li⁺/Li), a first cycle efficiency of 86.4%, and a capacity retention after 50 cycles of 86.8% (0.5 C / 1 C charge / discharge).

100: molded sintered body (green body)
30: drive roller

A cellulose nanofibril (CNF) adhesive material was developed as a PFAS-free interface layer for polymer electrolyte membrane fuel cell (PEMFC) membrane electrode assemblies (MEAs).

The adhesive material comprises a colloidal dispersion of cellulose nanofibrils at a concentration of 2-10 g/l. The cellulose nanomaterial can be chemically modified to exhibit aldehyde groups (0.5-1 mmol/g dry nanomaterial), sulfonate groups (200-1500 μmol/g), or other functional groups such as carboxymethyl, phosphor, or sulfoethyl groups on the nanofiber surfaces.

Two commercial platinum gas diffusion electrodes were prepared. The cellulose dispersion was placed on one side of a cellulose-based proton exchange membrane and a Pt-GDE was added. The assembly was hot-pressed (70°C, 60 s). The cellulose dispersion was applied to the opposite membrane side, the second Pt-GDE was aligned, and hot-pressing was repeated (70°C, 60 s).

Fuel cell testing was performed with H₂ and air at 40°C and 80% relative humidity. The Pt-GDEs were activated at 300 mV. Polarization curves for MEAs assembled with the sulfoethylated cellulose nanofibril adhesive exhibit similar performance compared to conventional Nafion ionomer-based MEAs (see Figure).

membrane_SE: sulfoethylated cellulose ionomer MEA
membrane_SE_Nafion: Nafion ionomer MEA