Anode-free battery
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An anode-free battery (AFB) is one that is manufactured without an anode and instead creates a metal anode the first time it is charged. The anode is formed from charge carriers supplied by the cathode. As such, before charging, the battery consists of a cathode, current collectors, separator and electrolyte.
Conventional batteries use an anode made of graphite. However, the graphite consumes space, adds weight, adds to materials costs, and increases manufacturing complexity. As of 2023, the most practical designs that support lithium metal batteries are anode-free.
Design
Anode-free batteries typically require a solid-state electrolyte made of a ceramic or polymer. This is to ensure that over many charge/discharge cycles, dendrites that may form on the anode-side current collector do not cross the electrolyte and short circuit the battery. Some solid-state designs use conventional graphite anodes.
The charge carriers electroplate lithium onto the anode current collector surface, there offering a solid electrolyte interphase (SEI). After the initial charge, an AFB operates as a lithium metal battery.[1] By eliminating the permanent lithium metal anode, AFBs operate with all the lithium acts as a charge carrier, rather than remaining at the anode (zero excess lithium). Manufacturing a lithium anode is also complex, as this involves making and manipulating a thin lithium foil, given its high reactivity and viscosity. However, some lithium is lost in each charge/discharge cycle, reducing cycle counts. Deposited lithium also tends to be of uneven depth and is more likely to produce dendrites. solid electrolyte interphase[2]
Cathode
Anode-free lithium ion batteries have been demonstrated using a variety of cathode materials, such as LiFePO4, LiCoO2, and LiNi1/3Mn1/3Co1/3 (NMC111).
These intercalation-type cathodes typically offer limited Li content (14.3 at.% for LiFePO4, 25 at.% for LiCoO2 and LiNixCoyMn1-x-yO2), although they remain the primary research targets.[2] Oxide cathodes may release reactive oxygen radicals that trigger side reactions with flammable organic electrolytes. By contrast, lithium sulfide can reach 67% lithium. When fully lithiated, the cathode experiences negligible volume changes during cycling.[3] However, Li2S cathodes may suffer initial activation overpotential (~1.0 V) and poor charge kinetics.[3]