Secondary battery and electric device
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving both high cycle performance and fast-charging capabilities due to the trade-off between areal density and lithium ion conductivity, which affects energy density and safety.
Innovation Solution
A secondary battery design incorporating a negative electrode sheet with a specific areal density and lithium ion conductivity, combined with an electrolyte containing a first solvent of the form R1-COO-R2 and an additive that forms a stable solid electrolyte interface (SEI) film, balances fast-charging and cycle performance by optimizing ion conductivity and reducing gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the areal density of the negative electrode active layer is increased to improve energy density, then the energy density is improved, but the fast-charging performance deteriorates due to reduced lithium ion conductivity
Solution Approach 1:
The patent optimizes the areal density parameter of the negative electrode active layer within a specific range (0.08-0.20 mg/mm²) to balance energy density and fast-charging performance. By precisely controlling this parameter, the patent achieves both high energy density and good lithium ion conductivity for fast charging.
Solution Approach 2:
The patent uses a composite electrolyte system comprising multiple components (cyclic carbonate and chain carbonate in specific ratios, along with additives like LiPO2F2 and LiDFOB) to enhance lithium ion conductivity while maintaining energy density, thereby resolving the contradiction between energy storage and charging speed.
2Speed
If the areal density of the negative electrode active layer is decreased to improve fast-charging performance, then the lithium ion conductivity is improved, but the energy density deteriorates
Solution Approach 1:
The patent determines the optimal areal density range (0.08-0.20 mg/mm²) for the negative electrode active layer to simultaneously achieve high lithium ion conductivity and acceptable energy density. This parameter optimization resolves the trade-off between charging speed and energy storage.
Solution Approach 2:
The patent applies different electrolyte compositions and additive concentrations in specific regions or proportions to enhance local lithium ion conductivity without compromising overall energy density, thereby resolving the contradiction between fast charging and energy storage.
3Speed
If the electrolyte composition is optimized to improve fast-charging performance, then the lithium ion conductivity is improved, but gas generation increases which affects cycle performance
Solution Approach 1:
The patent converts the potential harm of gas-generating electrolyte components into a benefit by carefully selecting and proportioning additives (LiPO2F2, LiDFOB) that form stable SEI films. This prevents excessive gas generation while maintaining high lithium ion conductivity for fast charging.
Solution Approach 2:
The patent introduces specific electrolyte additives as intermediaries that mediate between the electrolyte and electrode, forming protective SEI films that prevent harmful gas generation reactions while allowing efficient lithium ion transport for fast charging.
4Reliability
If the additive content in the electrolyte is increased to improve SEI film stability, then the cycle performance is improved, but the cost and complexity of the electrolyte formulation increases
Solution Approach 1:
The patent optimizes the concentration parameters of electrolyte additives within specific ranges to achieve stable SEI film formation and good cycle performance without excessive complexity. By controlling additive content precisely, the patent balances performance improvement with formulation simplicity.
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 optimized battery design maintains high energy density, fast-charging capabilities, and improved cycle life by controlling the areal density and lithium ion conductivity, while minimizing gas generation and enhancing safety.
Implementation Method 1
an additive, at least a part of which reacts prior to the first solvent at the time of forming a solid electrolyte interface (SEI) film
Implementation Method 2
the lithium ion conductivity of the electrolyte is 12 mS/cm to 20 mS/cm
Data Source
Figure 1~2
Figure 3
AI summary
A secondary battery and an electric device. The secondary battery includes a negative electrode sheet and an electrolyte, where the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, the negative electrode active layer includes graphite, and the areal density of the negative electrode active layer is 0.09 mg/mm2 to 0.16 mg/mm2; the lithium ion conductivity of the electrolyte at 25°C is 10 mS/cm to 20 mS/cm; and the electrolyte includes a first solvent, the first solvent having a general structural formula of R1-COO-R2, where R1 and R2 are each independently selected from any one of C1-C5 alkyl and C1-C5 haloalkyl.