Prelithiated Silicon Anode for Battery Cycle Life
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Solution Overview
Problem
Lithium-ion batteries with silicon-based anodes and high-voltage nickel-rich cathodes face challenges in long-term cycling stability due to irreversible capacity loss and solid electrolyte interphase (SEI) formation, leading to performance fade.
Innovation Solution
The development of prelithiated silicon-based electrodes with a prelithiation level of 0% to 30% and the use of a self-supporting composite material film with a carbonized polymer as a current collector, eliminating the need for metal foil and enhancing cycle life, combined with an electrolyte containing fluoroethylene carbonate (FEC) to stabilize the SEI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based anodes are used to achieve high capacity, then energy density is improved, but irreversible capacity loss occurs due to SEI formation
Solution Approach 1:
The patent applies preliminary action by introducing lithium into the silicon anode structure before battery assembly and operation. This prelithiation process pre-forms part of the lithium-silicon alloy, so that during the first charge cycle, less lithium is consumed by SEI formation, thereby reducing irreversible capacity loss and improving overall energy density.
2Use of energy by moving object
If high-voltage nickel-rich cathodes are used to increase capacity, then energy density is improved, but long-term cycling stability deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and structure of the cathode material. Specifically, it uses nickel-rich layered oxides with controlled stoichiometry and crystal structure parameters to achieve high voltage operation while maintaining structural stability during cycling, thus improving both energy density and cycling stability.
3Quantity of substance
If silicon anodes are lithiated during first charge to form alloy, then capacity is increased, but organic solvent electrolytes decompose to form SEI, causing Li loss
Solution Approach 1:
The patent applies preliminary action by pre-lithiating the silicon anode before battery assembly. This ensures that when the battery operates, the prelithiated silicon has excess lithium already incorporated, so that the lithium consumed by SEI formation during first charge does not deplete the available lithium, thereby maintaining higher capacity.
Solution Approach 2:
The patent introduces a solid electrolyte interphase (SEI) stabilizing approach where the electrolyte composition is optimized to form a stable SEI layer that prevents further decomposition. This intermediary SEI layer acts as a protective barrier, allowing lithium ion transport while preventing harmful electrolyte decomposition and lithium loss.
4Duration of action of stationary object
If Li losses accumulate during cycling, then capacity fade occurs, but performance degradation increases
Solution Approach 1:
The patent applies preliminary action by pre-lithiating the silicon anode to compensate for future lithium losses. The excess lithium incorporated during prelithiation serves as a reservoir that compensates for lithium consumed by SEI formation and other irreversible processes during cycling, thereby maintaining capacity retention and extending cycle life.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the first cycle coulombic efficiency, stabilizes cycle performance, and reduces capacity fade, achieving higher energy density and longer cycle life for silicon-dominant anode batteries.
Implementation Method 1
silicon reduces Li ions emanating from the cathodes and through the electrolyte resulting in an alloy of lithium and silicon
Implementation Method 2
organic solvent based electrolytes of batteries are unstable and tend to decompose a portion of the Li content to form a solid electrolyte interphase (SEI)
Implementation Method 3
as the SEI layer is formed, a portion of the Li introduced into the silicon is irreversibly bound effectively removing it from cyclic operation
Data Source
AI summary
The present disclosure relates to prelithiated Si electrodes, methods of prelithiating Si electrodes, and use of prelithiated electrodes in electrochemical devices are described. There are several characteristics of electrode prelithiation that enable the superior battery performance. First, a prelithiated silicon anode is already in its expanded state during SEI formation, and therefore less of the SEI layer breaks down and reforms during cycling. Second, the prelithiated anode has a lower anode potential, which may also help the cycle performance of an electrochemical device. A silicon-based electrode, for use in energy storage devices, may have prelithiated silicon active material with a prelithiation level of above 0% to about 30%, with a lithium source within the energy storage devices providing excess lithium for contributing at least a portion of the prelithiation of the silicon active material.