Two ideas sit behind the phrase "solid-state battery," and the patents keep them distinct. The first is the electrolyte: a conventional lithium-ion cell moves ions between its electrodes through a liquid or gel electrolyte, and a solid-state cell replaces that with a solid electrolyte — an oxide, a sulfide, or a polymer — that conducts ions while staying rigid. The second, more aggressive idea is the anode. The most ambitious solid-state designs are anode-free: the cell is manufactured with no anode material at all, just a bare current collector, and the lithium that would have made up the anode is instead plated onto that collector out of the cathode during the first charge, then stripped back during discharge. Removing the anode removes mass, volume, and cost — which is the whole point — but it puts enormous demands on the electrolyte and the interfaces, which is why so much of the patenting happens here.

A granted record makes the architecture concrete. The U.S. patent US11824159B2, "Anode-free solid-state battery and method of battery fabrication," issued November 21, 2023 to GM Global Technology Operations LLC, states the design in its abstract.

"An anode-free solid-state battery includes a cathode layer having transient anode elements and a bare current collector devoid of non-transitory anode material and configured to accept thereon the transient anode elements. The battery also includes a solid-state electrolyte layer defining voids and arranged between the current collector and the cathode layer."— Anode-free solid-state battery and method of battery fabrication, source

Every phrase in that sentence is doing work, and reading it closely is the difference between understanding the architecture and repeating a slogan. The "transient anode elements" are the lithium that lives in the cathode at rest and migrates to form the anode only when the cell is charged. The "bare current collector devoid of non-transitory anode material" is the anode-free part stated precisely: there is no permanent anode, only a collector waiting to receive lithium. The abstract continues that charging "diffuses the anode elements from the cathode layer, via the gelled solid-state electrolyte layer, onto the current collector," and discharging returns them — the plate-and-strip cycle that defines an anode-free cell. The record also discloses a gel "situated within the solid-state electrolyte and cathode layers" to fill the electrolyte's voids and carry the ions, which is the disclosure's answer to the central problem of solid-state cells: getting reliable contact and ion conduction across solid interfaces.

How the field classifies and where the patenting concentrates

The classification line on this record reads H01M 10/0565, H01M 4/505, H01M 4/525, H01M 10/0525, and H01M 2004/028. The two H01M 10 symbols place it among rechargeable lithium cells and their electrolytes; the H01M 4 symbols mark the cathode active materials; and the 2004 indexing symbol flags the anode-free construction. That is the standard signature of a solid-state cell patent — rechargeable-chemistry symbols in the H01M 10 subclass, electrode symbols in H01M 4 — and it is the handle a landscape analyst uses to find the field rather than relying on the inconsistent phrasing of "solid-state" versus "all-solid-state." The patenting clusters tightly around the interfaces: a separate granted record in the same area, US12424625B2, "Stable lithium metal sulfide coatings for solid-state batteries," claims "a lithium metal sulfide separating an anode and a solid-state electrolyte" — an interfacial-layer invention. The recurring subject across solid-state records is not the bulk electrolyte chemistry alone but the boundary between the electrolyte and the electrode, which is where solid cells tend to fail.

That clustering at the interface is itself the signal a landscape reader should take from the field. In a liquid-electrolyte cell, the electrolyte flows into contact with the electrode surfaces and re-wets them as the cell cycles; a solid electrolyte cannot do that, so any gap, void, or chemical incompatibility at the solid-solid boundary becomes a permanent defect that grows with cycling. The patents reflect this physics directly: rather than one or two foundational chemistry patents, the record fills with interfacial-layer coatings, surface-roughening of current collectors, gels and intermediate films to bridge contact, and pressure or stacking arrangements to hold the layers together. Reading a run of solid-state records, the engineering story that emerges is less about discovering a new conductive solid and more about the unglamorous work of making solids touch and stay touching. A landscape that counts "solid-state battery" filings as a single bet misses that the filings divide into electrolyte-chemistry bets and interface-engineering bets, and that the second category is where the volume sits.

What the records establish — and what they do not

The discipline here is to separate what a patent claims from what a company ships, because solid-state batteries are a field where that gap is wide and consequential. A granted anode-free patent establishes that a particular cell architecture and fabrication method were claimed and allowed; it does not establish that the assignee is mass-producing such a cell, that the cell meets any cycle-life or fast-charge target, or that the architecture has cleared the manufacturing hurdles — dendrite growth, interfacial contact, stack pressure — that have kept solid-state cells largely out of volume production. The abstract is the description of an invention, and the protection it carries is set by its claims, which may be narrower than the architecture the abstract sketches. What the patent record reliably gives a reader is the engineering vocabulary, stated exactly: a solid-state cell swaps the liquid electrolyte for a solid one, an anode-free cell omits the anode and plates lithium onto a bare collector from the cathode, and the hard part — the part the claims keep returning to — is the interface where solid meets solid.