Graphite Anode Composition for Li-Ion Battery Temperature Stability
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Solution Overview
Problem
Conventional lithium-ion secondary batteries face challenges in achieving high power performance at low temperatures (e.g., -40°C) and high stability/calendar life at high temperatures (e.g., 60°C) due to the low ionic conductivity of cyclic carbonates and the reactivity of natural graphite with ester solvents at low and high temperatures, respectively.
Innovation Solution
A lithium-ion secondary battery design incorporating a blend of natural and artificial graphite particles with a specific particle size distribution and a solvent containing a linear ester and additives for forming a solid electrolyte interphase (SEI) to enhance stability and performance across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If natural graphite is used as anode active material, then high power performance at low temperature is achieved, but electrolyte stability at high temperature deteriorates due to reactions between graphite edge planes and ester solvents
Solution Approach 1:
The patent changes the particle size parameter of natural graphite from conventional small sizes (typically <10 μm) to a specific range of 10-30 μm. This parameter change reduces the relative surface area and number of reactive edge planes, thereby decreasing the reactivity with ester solvents at high temperature while maintaining adequate power performance at low temperature
Solution Approach 2:
The patent creates a composite anode material system by combining natural graphite particles (10-30 μm) with artificial graphite particles and conductive carbon materials. This composite structure allows the natural graphite to provide low-temperature power performance while the artificial graphite and conductive carbon compensate for reduced surface area, and the specific natural graphite particle size reduces high-temperature reactivity
2Reliability
If cyclic carbonate electrolytes are used, then high temperature stability is achieved, but low temperature ionic conductivity deteriorates
Solution Approach 1:
The patent uses a composite electrolyte system combining cyclic carbonate (for high-temperature stability) with linear carbonate and ester components (for low-temperature conductivity). The cyclic carbonate provides thermal stability at high temperature, while the linear carbonate and ester portions maintain ionic conductivity at low temperature, resolving the contradiction between temperature extremes
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 battery achieves a combination of high temperature calendar life and high power performance at low temperatures by stabilizing the electrolyte and reducing reactivity, thereby extending the battery's operational lifespan and performance.
Implementation Method 1
one or more additive compounds for forming a solid electrolyte interphase ('SEI') on the anode active material
Data Source
AI summary
A lithium-ion secondary battery, including (A) an anode including an anode active material; (B) a cathode including a cathode active material; (C) a separator; and (D) an electrolytic solution, the anode active material including (a1) about 5.0 to about 45.0 wt % natural graphite particles, and (a2) about 95.0 to about 55.0 wt % artificial graphite particles; a size of both the natural and artificial graphite particles (a1), (a2) independently being about 2.0 μm<D50<about 7.0 μm; the electrolytic solution containing (d1) an organic solvent, (d2) a charge carrier, and (d3) one or more additive compounds for forming a solid electrolyte interphase (“SEI”) on the anode; and the organic solvent (d1) including about 10.0 to about 95.0 vol % of a linear ester of a C2 to C8 saturated acid; and a total weight of the additive compounds (d3) being about 0.20 to about 6.0 wt %.