Lithium Metal Cell Stack Compression for Longer Cycle Life
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Solution Overview
Problem
Current techniques for controlling dendrite growth in lithium metal batteries are less than satisfactory, leading to short circuits and degradation after a few discharge/charge cycles, as the re-plating of lithium metal ions is often non-uniform, resulting in dendrite formation that can pierce the separator.
Innovation Solution
A battery core pack with a containment structure that applies a substantially uniform and constant surface pressure of at least 100 psi to the cell stack, using a combination of lithium salts and solvents in the electrolyte, and a cell design with a layered or spinel oxide cathode and lithium metal anode, to suppress dendrite growth and extend cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal anode is used for high energy density, then energy density is improved, but dendrite growth occurs leading to short circuits and reduced reliability
Solution Approach 1:
The patent applies constant compressive force (5-100 psi) to the cell structure as a physical parameter change that modifies the mechanical environment during charging. This constraint prevents excessive volume expansion of the lithium metal anode and promotes uniform lithium plating, thereby suppressing dendrite growth while maintaining high energy density benefits
Solution Approach 2:
The containment structure with compressive force acts as a preliminary constraint that prevents dendrite formation before it can occur. By pre-applying mechanical pressure during cell assembly and charging, the system counteracts the natural tendency of lithium to form dendrites during plating, preventing the harmful effect before it manifests
2Reliability
If compressive force is applied to constrain cell structure, then dendrite growth is suppressed, but device complexity increases
Solution Approach 1:
The containment structure serves multiple functions simultaneously: it provides mechanical constraint to suppress dendrite growth, maintains uniform pressure distribution across the cell, and supports the cell during volume changes. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity while achieving reliable dendrite suppression
3Manufacturing precision
If constant compressive force is applied during charging, then uniform lithium plating is achieved, but manufacturing complexity increases
Solution Approach 1:
The compressive force is applied during cell assembly and maintained throughout charging cycles as a preliminary and continuous action. This ensures uniform lithium plating from the first charge cycle, eliminating the need for complex post-manufacturing adjustments or specialized plating equipment, thereby achieving high manufacturing precision with relatively simple implementation
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
The uniform pressure effectively constrains lithium plating and stripping, significantly extending the battery's cycle life by maintaining discharge capacity over 100 charge/discharge cycles with improved energy density and suppressing dendrite growth, achieving a cycle life of over 300 cycles with minimal pressure variance across the cell faces.
Implementation Method 1
the containment structure imparts a substantially uniform surface pressure on the cell stack of at least about 100 psi
Implementation Method 2
lithium metal ions are stripped from the anode and travel to the cathode through the separator
Implementation Method 3
During charging, the ion flow is reversed and the metal ions are re-plated back onto the anode
Data Source
AI summary
Battery core packs employing specific electrolyte solutions and minimum cell-face pressures and methods are disclosed for minimizing dendrite growth and increasing cycle life of metal and metal-ion battery cells.