Structural Lithium-ion Batteries Using Dual-functional CarbonFabric Composite Anodes

摘要

The cost of launching a satellite into space is estimated at up to $20,000 per kilogram, andbatteries typically occupy a significant share of a spacecraft’s mass budget. Boundless’ unique structurallithium-ion battery is intended to reduce overall vehicle mass and volume by replacing inert structure withactive energy storage. In the structural battery, rigid load-bearing lithium-ion cells form the core of alightweight sandwich panel. The mass of the battery can be effectively discounted by the mass of thestructure which it replaces. The volume of the battery effectively goes to zero.This paper discusses Boundless’ development of a dual-function rigid composite anode for a lithium-ionbicell. This new anode uses mesophase pitch-based carbon fabric composite as both a structural elementand as an electrochemically active site for intercalation of lithium ions. Particular effort has gone intodeveloping a method to saturate one face of the fabric in matrix resin for structural integrity, whileleaving a sufficient amount of free fibers on the opposite face for ion intercalation. In initial tests, thefabric demonstrated a charge capacity of 285 mAh/g and an irreversible capacity of 7%. This approachesthe electrochemical performance of the particulate carbon (MCMB) traditionally used in lithium batteryanodes while offering structural performance.Since separator and cathodes are comprised of traditional materials, a structural cell requires the use of abicell construction where two rigid carbon composite anodes sandwich the separator and double-sidedcathode. Depending on the requirements of energy storage and panel structure, the bicell can be combinedwith inert carbon composite to form the honeycomb of a multifunctional structural battery panel.This paper will discuss the optimization of the carbon fabric composite anode for strength andelectrochemical activity. The critical component is the matrix resin, which must partially saturate thefabric and be stable in the interior of the lithium-ion battery. In addition, the present state of developmentof lithium-ion structural bicells and their performance will be described. Ongoing work includesoptimization of the materials used as well as empirical testing of higher-level structural assemblies.