Triweekly Patent Update – Free Version

An anode-free all-solid-state battery was developed featuring an amorphous silicon layer on a copper current collector. The silicon layer exhibits a thickness of up to 500 nm (see Figure), resulting in Ns/P ratios (charge capacity of silicon layer to positive electrode) of less than 0.3.

The battery comprises a Li₆PS₅Cl (LPSCl) solid electrolyte separator and a positive electrode composite of NMC811 with LPSCl and vapor-grown carbon fiber (VGCF) (mass ratio : 66 : 31 : 3, 3 mAh/cm² loading). Amorphous silicon (500 nm) was deposited on Cu via sputtering. This stack was pressed at 370 MPa prior to cycling, while a stack pressure of 5 MPa was maintained during cycling.

During initial charging, silicon lithiation occurred up to 3.7 V (0.25 mAh/cm²), forming amorphous Li_xSi_1-x (0.5<x<0.79) with composition Li_0.7Si_0.3. Subsequent lithium metal plating (2.75 mAh/cm²) formed a dense lithium layer on the pre-lithiated silicon substrate. The lithiated silicon layer persists throughout cycling without further silicon participation.

Rate performance testing in the all-solid sulfide electrolyte cells exhibits stable cycling up to C/5 (0.6 mA/cm²). Thin-film cells with LiPON solid electrolyte demonstrate critical current densities up to 5.0 mA/cm², representing a five-fold improvement compared to bare Cu current collectors.

Na ingots were cut into ≈5 mm pieces and mixed with Si powder in a Wonder Crusher (Si amount: 102 parts by mass per 100 parts Na). The Na ingots were added in three portions, followed by mixing for 1 min for each portion. The resulting mixture was placed in a stainless steel container, evacuated, and heated under argon flow (420°C, 40 h), which resulted in a Na-Si alloy.

AlF₃ particles were sieved with a 32 µm mesh to remove fine particles, followed by sieving with a 75 µm mesh to remove coarse particles, which resulted in an AlF₃ classified material with a D50 particle size of 56.1 µm (D10: 38.9 µm, D90: 80.2 µm).

The AlF₃ classified material was mixed with the Na-Si alloy (AlF₃ amount: 50-100 parts by mass per 100 parts Na-Si alloy). This mixture was placed in a stainless steel container, evacuated, and heated under argon flow (350°C, 60 h), resulting in silicon clathrate II.

The material exhibits a silicon clathrate II / silicon clathrate I ratio of 14.0 as measured by XRD (X-ray diffraction), as compared to 0.74 for a comparative material prepared without classification of AlF₃ particles (D50: 75.1 µm, D10: 37.6 µm, D90: 138.6 µm).

A high-nickel Ni_0.89Co_0.04Mn_0.07(OH)₂ precursor with center-concentrated buffer pores was synthesized. Polypropylene particles (3 μm diameter) were added to a mixed metal sulfate solution (Ni : Co : Mn molar ratio of 0.89 : 0.04 : 0.07, 2.0 M, 50°C). The solution was stirred at 400 rpm while sodium hydroxide was added to maintain pH at 11.5-11.6, forming precursor seeds. The pH was decreased stepwise to 11.0-11.2, 10.7-10.9, and 10.3-10.5 while stirring speed increased to 1,000 rpm (5 h).

The dried precursor exhibits secondary particles (≈12 μm) with polypropylene concentrated in the core region. The precursor was mixed with lithium hydroxide (Li : transition metal molar ratio of 1.03 : 1) and sintered (5°C/min to 750°C, 17 h) to obtain LiNi_0.89Co_0.04Mn_0.07O₂.

During sintering, polypropylene decomposes to form buffer pores (≈3 μm) concentrated in the particle center (see Figure). Primary particles in the outer region exhibit radial crystalline structure oriented from center to surface.

In half-cells (lithium metal negative electrode, 0.5 C charge / 1 C discharge, 45°C), the material exhibits a discharge capacity of 210 mAh/g and capacity retention of 96.3% after 50 cycles, as compared to 210 mAh/g and 92.1% for material without buffer pores. The material exhibits 3.38 vol% of particles <1 μm after pressing, as compared to 5.71 vol% for comparative material.

A modified ionomer was developed for polymer electrolyte membrane fuel cell (PEMFC) cathode catalyst layers with enhanced oxygen transportability.

The ionomer comprises perfluorocarbon sulfonic acid polymer (Nafion EW : 1100) with sulfonic acid functional groups. A modifying layer containing 1,3,5-triazine forms ionic bonds with the acidic functional groups on the ionomer surface.

The ionomer material and modifier containing 1,3,5-triazine were mixed in water/ethanol solvent using an ultrasonic homogenizer and stirrer (15 min). The 1,3,5-triazine content was 3 mass% relative to total ionomer mass, corresponding to 34 mol% relative to acidic functional groups.

The modified ionomer was combined with platinum catalyst (48-50 mass% Pt on acetylene black support) to prepare cathode catalyst ink. The ink was coated onto polytetrafluoroethylene (PTFE) substrate and dried to form a catalyst layer (5-30 μm thickness, 0.1-0.6 mg-Pt/cm²). Membrane electrode assemblies (MEA) were fabricated using Nafion NR211 electrolyte membrane.

Performance testing (80°C, 80% relative humidity, 3.2 A/cm²) exhibits a cell voltage improvement of 64 mV as compared to unmodified ionomer MEA (absolute cell voltages were not disclosed). The electrode catalyst layer exhibits proton transport resistance of 0.043 Ω·cm² and oxygen diffusion resistance of 13 s/m, as compared to 0.062 Ω·cm² and 15 s/m for unmodified ionomer.