A previous post, Li-ion Battery Disadvantages, examines how the original magnetic recording tape production paradigm for the Li-ion battery has created performance limitations and safety issues. In contrast to the “jelly roll” structure of a conventional Li-ion battery, derived from magnetic recording tape production techniques, Enovix uses 3D cell architecture (see illustration below).
The Enovix 3D cell is inherently rectangular. This structure eliminates the dead inner-cell winding core of conventional Li-ion battery construction and reduces other inactive elements. For example, the 3D cell utilizes thinner metal film current collectors, rather than the thicker foil current collectors of conventional Li-ion battery construction.
This significantly increases the proportion of active to inactive materials, so that only about 25% of the total battery volume is inactive. This is a sharp contrast with the inactive materials of a conventional Li-ion cell, which typically comprise about 43% of the total battery volume. The improved ratio of active to inactive elements—about 3:1 (75:25) versus about 4:3 (57:43)—produces a corresponding increase in volumetric energy density.
2D microfabrication was initially used to miniaturize electronic devices (i.e., micro-electronics). The technique was adapted for 3D disk drive read/write heads and for MEMS (microelectro-mechanical systems) sensors and wafer probe cards. The Enovix 3D cell is fabricated using a photolithographic mask and etch process applied to a solar-grade silicon (SGSi) substrate—a process initially pioneered for the low-cost, high-volume production of photovoltaic solar cells.
While this is a novel production approach for Li-ion batteries, it has previously proven itself by transforming the dated, complex industrial processes of several major industries. For example, photolithography and wafer production have transformed computing from vacuum tubes to integrated circuits (ICs), lighting from incandescent bulbs to light-emitting diodes (LEDs) and video displays (including television) from cathode ray tubes (CRTs) to flat-panel liquid-crystal displays (LCDs).