Abstract
All-in-one assemblies of separator, electrode and current collector (SECA) for lithium ion batteries are presented by using 1D nanowires of Si and Cu (nwSi and nwCu). Even without binders, integrity of SECA is secured via structural joints based on ductility of Cu as well as entanglement of nwSi and nwCu. By controlling the ratio of the nanowires, the number of contact points and voids accommodating volume expansion of Si active material are tunable. Zero volume expansion and high energy density are simultaneously achievable by the architecture.
Highlights
All-in-one assemblies of separator, electrode and current collector (SECA) for lithium ion batteries are presented by using 1D nanowires of Si and Cu
Polymeric binders used in conventional lithium ion batteries (LIBs) were not used in this architecture because nwCu plays a role as the binder due to its ductile properties
Line mappings of Cu and Si by energy dispersive spectroscopy were included in each photo. (d) The comparison between SECA and a conventional tri-component electrode in terms of total electrode mass including current collector except of separator
Summary
L min cc to diameter of nwSi was used as the ordinate without dimension, which is the function of only the ratio of diameters (or radius) of nwCu to nwSi at fixed xSi (not the function of absolute values of radii). The tri-layered laminates were dried and pressed to inter-locking structure between nwSi and nwCu in the electrode layer or between nwCu in the current collector. In the conventional tri-component (active material, binder and conducting agent) electrode of this work, copper foils of micrometer thickness (e.g. 18 um thick with 16 mg cm22) are used. NwSi as a representative case, only 44 % of electrode thickness (14 um/32 um) and 39 % of total mass (1.3 mg cm22/3.3 mg cm22) were occupied by the current collectors of inter-tangled nwCu. Resultantly, for example, lighter electrodes including current collector can be possible by the SECA with only 30 % to 70 % of mass of a conventional tri-component electrode at the same silicon loading of 0.6 mg cm[22] (Figure 1d; detailed calculation in supporting information). Based on the lines-ona-plate model in which nanowires of the minor component is evenly distributed on the plate consisting of nanowires of the major component, the maximum values of nc (ncmax) and the minimum values of Lcc (Lccmin) were calculated as functions of xSi (Figure 1e and f; detailed calculation in supporting information)
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