Mitsui Kinzoku Company, Limited
5706.TMEDIUMScore: 30.5Battery Materials / Electrolytic Copper Foil + A-SOLiD · Weight: 3%· Data as of 2026-05-21
Investment Thesis
Renamed from Mitsui Mining & Smelting (Oct 2025). Global leader in electrolytic copper foil — the anode current collector inside every Li-ion battery cell. Near-monopoly in ultra-thin carrier copper foil (MicroThin: >90% global share in advanced PCB/packaging foil). Honda e-motorcycle supply chain link: copper foil → Panasonic cylindrical cells → Honda Mobile Power Pack (confirmed Panasonic as MPP cell supplier); ALSO → LG Energy Solution 2170 cells → Honda Vietnam Hanoi 1,000-station swap network (MOU May 2026, confirmed by TNGlobal/Electrek). Dual catalyst: (1) EV battery copper foil demand scaling with Honda Vietnam/India ramp; (2) A-SOLiD™ sulfide solid electrolyte R&D (pilot plant 2027) aligned with Honda's Jan 2025 all-solid-state battery demo line. ROE 18.4% + op margin ~15.6% = exceptional quality for materials company.
Risk
1) PB ~5x elevated vs. materials sector peers — guardrail warning (P/B above 80th percentile for cyclicals). Override: structural moat in carrier foil + ROE 18.4% justifies premium. 2) Battery copper foil moat is ★★★ (competitive vs. Korean SK Nexilis, Iljin, Chinese makers) even though carrier foil is ★★★★★ — distinguish the two segments. 3) FY2025 earnings upgrade was primarily AI server PCB foil, not EV battery foil — Honda motorcycle catalyst is medium-term, not immediate. 4) A-SOLiD ASSB is pre-commercial (pilot 2027) — speculative optionality, not revenue yet.
Monitoring Trigger
Q2 FY2026 results (Oct 2026): Check Functional Materials segment revenue split between AI server foil vs. battery foil. If battery foil >30% of segment, UPGRADE to HIGH. Honda Vietnam swap station count: if exceeds 200 by end-2026, CONFIRM supply chain ramp. A-SOLiD pilot plant announcement: if confirmed 2027 startup, UPGRADE thesis to include Honda ASSB optionality.
Key Dates
Key Metrics
Business Segments
| Segment | Revenue | Share | Description |
|---|---|---|---|
| Functional Materials (copper foil + battery materials) | est. ~¥200B+ | ~30%+ | Electrolytic copper foil for AI server PCB and EV battery anodes. MicroThin ultra-thin carrier foil (>90% share). A-SOLiD sulfide solid electrolyte R&D. |
| Metals (copper smelting + precious metals) | est. ~¥400B+ | ~55%+ | Traditional copper smelting, zinc processing, precious metal refining. Stable cash generation base. |
| Mobility (automotive parts + zinc die-casting) | est. ~¥100B | ~15% | Automotive parts, zinc die-casting — indirect Honda connection via automotive supply chain. |
Supply Chain Evidence
| Evidence | Customer | Product | Detail |
|---|---|---|---|
| probable | Panasonic Energy | Electrolytic copper foil for cylindrical 18650/21700 Li-ion cell anode current collector → Honda Mobile Power Pack e: cells | Panasonic is confirmed as Honda MPP cell manufacturer (Wikipedia/press releases); Mitsui Kinzoku is Japan's leading electrolytic copper foil maker; logical Tier-2 link. No named Panasonic-Mitsui Kinzoku contract found publicly. |
| probable | LG Energy Solution | Copper foil for 2170 cylindrical cells → Honda Vietnam MPP Hanoi 1,000-station swap network (MOU May 2026) | LG Energy Solution confirmed as 2170 cell supplier for Honda-Hanoi MPP swap network (May 2026 MOU). LG's Korea supply chain may use Korean foil (SK Nexilis) — not confirmed Mitsui. But Mitsui supplies global cell makers. |
| confirmed | AI server PCB manufacturers (via Functional Materials) | MicroThin ultra-thin carrier copper foil for advanced PCB/packaging — near-monopoly >90% global share | FY2025 earnings upgrade explicitly driven by AI server copper foil demand for VSP-grade ultra-thin foil. Current primary revenue driver. |
| inferred | Honda Motor (future — ASSB) | A-SOLiD™ sulfide solid electrolyte for all-solid-state batteries (pilot plant 2027) | Honda launched ASSB demo production line Jan 2025 targeting motorcycles and cars. Mitsui A-SOLiD pilot planned 2027. No confirmed Honda-Mitsui ASSB contract, but technology roadmap alignment is strong. |