Phosphorus Additive for Capacity Compensation in Secondary Batteries
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Solution Overview
Problem
Secondary batteries, particularly lithium-ion, sodium-ion, and potassium-ion batteries face challenges such as 'range anxiety', cycle stability, and safety performance due to irreversible ion consumption during the first charging cycle, leading to reduced capacity and energy density, and high-voltage conditions causing electrolyte decomposition and capacity loss.
Innovation Solution
A capacity-compensation electrolyte additive, specifically phosphorus-containing substances like LixPy, NamPn, and KpPq, are dissolved in the electrolyte to compensate for active ion and electron losses through decomposition, improving compatibility with solvents and electrode materials, and are prepared using a mild liquid-solid reaction method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium salts are added to electrolyte solvents to pre-lithiate the electrolyte, then lithium ion loss in the first cycle is compensated, but the solubility of lithium salts in electrolyte solvent is low and additional additives need to be added
Solution Approach 1:
The patent combines the pre-lithiation function and the solvent function into a single compound (LiP5). This eliminates the need for separate lithium salts and additional additives, resolving the contradiction between capacity compensation and electrolyte formula complexity.
Solution Approach 2:
LiP5 serves multiple functions simultaneously: it acts as a lithium source for pre-lithiation, functions as an electrolyte solvent with good solubility, and provides stable SEI formation. This multi-functionality resolves the contradiction by eliminating the need for multiple separate components.
2Reliability
If lithium powder or lithium particles are used for anode pre-lithiation, then active ion loss is compensated, but safety hazards and additional binders reduce overall energy density
Solution Approach 1:
The patent changes the physical and chemical parameters of the lithium source from metallic lithium powder/particles to a molecular compound (LiP5). This transformation eliminates safety hazards associated with reactive lithium metal while maintaining the capacity compensation function through controlled decomposition.
Solution Approach 2:
Instead of using stable but hazardous lithium metal that requires additional protective binders, the patent uses a disposable molecular compound (LiP5) that decomposes controllably to provide lithium ions, eliminating the need for additional binders and improving energy density.
3Reliability
If multiple solvents are used for pre-lithiation and preventing co-intercalation, then both functions are achieved, but the electrolyte formula becomes complex
Solution Approach 1:
LiP5 serves as a universal compound that simultaneously provides pre-lithiation functionality and prevents co-intercalation, eliminating the need for multiple separate solvent components and simplifying the electrolyte formula while maintaining all required functions.
4Reliability
If electrolytes decompose to form SEI and CEI in the first charging cycle, then protective interphases are formed, but active ions are consumed irreversibly reducing capacity and energy density
Solution Approach 1:
The patent performs preliminary action by having LiP5 decompose first to form a stable SEI layer before the main electrolyte decomposes. This preliminary SEI formation prevents subsequent continuous decomposition and active ion consumption, protecting the electrode while preserving capacity.
Solution Approach 2:
LiP5 serves itself by decomposing to provide both the protective SEI layer and additional lithium ions that compensate for the initial ion consumption. This self-service mechanism simultaneously achieves electrode protection and capacity compensation without requiring external additives.
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 additives enhance cycle stability and energy density by uniformly compensating ions and electrons across battery cycles, forming stable solid electrolyte and cathode interphases, and improving safety through phosphorus' flame retardant properties.
Implementation Method 1
The additive may decompose prior to the electrolyte solvents and the electrolyte salts to release the active ions and the electrons for compensating the capacity loss occurred in the first cycle and subsequent cycle processes of the battery
Implementation Method 2
A capacity-compensation electrolyte additive, specifically phosphorus-containing substances like LixPy, NamPn, and KpPq, are dissolved in the electrolyte
Data Source
AI summary
The present disclosure discloses a capacity-compensation electrolyte additive and electrolyte having the same, the additive comprises one or more of LixPy, NamPn and KpPq, where 0<x≤3, 0<y≤11, 0<m≤3, 0<n≤11, 0<p≤3 and 0<q≤11, the electrolyte is applied to a lithium-ion battery, a sodium-ion battery or a potassium-ion battery. The additive can decompose active ions and electrons during whole charge-discharge cycle, and improves the initial Coulombic efficiency of the battery, specific capacity and cycling stability, so as to achieve uniform capacity compensation; and the additive is dissolved prior to electrolyte solvents, the products stabilize both of cathode and anode solid electrolyte layer, and improve capacity retention ratio in batteries so as to achieve stable cycling. Adding additive in electrolyte will not hazard electrode structure, can achieve uniform capacity compensation, has higher safety and easy to implement.